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  • 151. Jönsson, Anders
    Modelling, Simulation and Experimental Investigation of a Rammer Compactor Machine2001Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This licentiate thesis considers the modelling, simulation and experimental investigation of a rammer compactor machine. The purpose is to develop an efficient and verified method for simulation of rammer compactor machines to be used in the product development process. The experience gained through this work is also intended to be useful for studying other types of dynamic compactor machines. Rammer compactor machines perform impact soil compaction. This is more efficient than static compaction. The machines are often used in places where a high degree of compaction is needed, and where the space for operation is limited. The complexity of this type of machine makes design optimisation through traditional prototype testing impractical. This has pointed to the need for a theoretical model and simulation procedure for predicting the dynamic behaviour of the machine. To be useful for optimisation the theoretical model and simulation procedure must be verified. By concurrently working with theoretical modelling, simulations, experimental verifications, and optimisation an efficient analysis support for product development is achieved. This co-ordination works both ways in an iterative manner: experimental investigations are used to verify theoretical models and simulations; and theoretical models and simulations are used to design good experiments. This Complete Approach concept enables better decisions to be made earlier on in the development process, resulting in a decrease in time-to-market and improved quality. In this thesis, the Complete Approach concept is applied to a rammer soil compactor machine. An introductory iteration is described. The good agreement between theoretical and experimental results indicates that the theoretical model and simulation procedure should prove useful in introductory optimisation studies. The thesis discusses reasons for the remaining discrepancy and suggests improvements in both the theoretical model and the experimental set-up for future iterations.

  • 152. Jönsson, Anders
    et al.
    Bathelt, Jens
    Broman, Göran
    Interacting with real time simulations – virtual reality in industry applications2003Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Modern manufacturing machines are highly multidisciplinary, and with demands on short time-to-market, product development based on traditional prototype testing has become impractical. By using virtual models, it is possible to test large numbers of variants and optimise the product with the aid of a minimum of physical prototypes. Due to the immense development of software and hardware for simulation and visualisation it should today be possible also for small and medium sized enterprises to use methods that just few years ago were too expensive and complicated. There is however still a great need for building knowledge and compe-tence. This work is an early step in a project aiming at a virtual water jet cutting machine to be used by the industrial partner for optimisation during the development process. The possibility of performing real-time simulations of this machine in a virtual environment, using a normal PC and commercial software, will be in-vestigated. Initially strongly simplified models of the system components are used and the focus is on the overall system model and the interaction between the operator and the virtual machine. It is shown that real-time interaction is possible with this system and with the obtained flexibility of the overall virtual model it should be easy to include more realistic component models for improved accuracy in future work. Preliminary results indicate however that to include, for example, flexibility within the mechanic structure, component modelling will be delicate. These models must describe relevant characteristics accurately enough while still being computationally effective enough for real-time interaction and systems optimisation to be possible. This will probably be a challenge in the continuation of the project, even with an expected continued strong devel-opment of computer capacity.

  • 153. Jönsson, Anders
    et al.
    Broman, Göran
    Experimental Investigation of a Rammer Soil Compactor Machine on Linear Spring Foundation2001Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Rammer compactor machines perform impact soil compaction, which is very efficient compared to static compaction. They are often used in places where a high degree of compaction is needed and the space for operation is limited. The complexity of this machine type makes design optimisation through traditional prototype testing impractical. This has pointed to the need for a theoretical model and simulation procedure for prediction of the dynamic behaviour of the machine. To be useful for optimisation as design parameters are changed during product development the theoretical model and simulation procedure must be verified. By concurrently working with theoretical modelling, simulations, experimental verifications, and optimisation an efficient analysis support for product development is achieved. This co-ordination works both ways in an iterative manner. Experimental investigations are used to verify theoretical models and simulations. Theoretical models and simulations are used to design good experiments. This Complete Approach concept makes better decisions possible earlier in the development process, resulting in decreased time to market and improved quality. In this paper the Complete Approach concept is described. It is applied on a rammer soil compactor machine. An introductory iteration, with emphasis on the experimental part, is described. In the experimental set-up the rammer foot is attached to a linear spring foundation. This eliminates uncertainties related to soil modelling and makes a check of the model of the machine itself possible. The good agreement between theoretical and experimental results indicates that the theoretical model and simulation procedure should be useful for introductory optimisation studies. Reasons for the discrepancy are discussed and suggestions for improvements of both the theoretical model and the experimental set-up in coming iterations are given.

  • 154. Jönsson, Anders
    et al.
    Broman, Göran
    Bathelt, Jens
    Implications of modelling one-dimensional impact by using a spring and damper element2005Inngår i: Proceedings of the Institution of mechanical engineers. Proceedings part K, journal of multi-body dynamics, ISSN 1464-4193, E-ISSN 2041-3068, Vol. 219, nr 7, s. 299-305Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A spring and damper contact force element is often used for modelling impact in multi-body dynamics. The related condition for transition between contact and non-contact is, however, inconsistently implemented in the literature and commercial software. This comparative study aims to clarify the implications of four commonly used transition conditions. Principal differences are discussed and, by simulation of a typical system, it is shown that there are significant differences in the dynamics of the system depending on the different conditions. Two of them give unrealistic contact forces and should imply incorrect prediction of system dynamics in most applications. This suggests that it is important to review results obtained from using these conditions and to eliminate them from commercial software. A discussion of the two other conditions culminates in a recommendation.

  • 155. Jönsson, Anders
    et al.
    Broman, Göran
    Engström, Anders
    Modelling of a Soil Compaction Tamping Machine using Simulink1999Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A theoretical model for the dynamic behaviour of a soil compaction tamping machine is derived. The Matlab toolbox Simulink is used to solve the equations of motion. Simulink is used because it is possible to combine the kinetic model of the machine with a more complex FE-model. The theoretical model has been verified experimentally, where the soil compaction tamping machine was run on a simulated soil material. The agreement between the simulation and the experiment is very good, which implies that this simplified model of the machine can be used for a more complete study of the total system, including a more correct soil model.

  • 156. Jönsson, Anders
    et al.
    Broman, Göran
    Östholm, Stefan
    Multidisciplinary Simulation of Active Control of Machine-Tool Vibration in Turning2000Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The increasing computer power in modern manufacturing machines has given the possibility to integrate advanced computer based control systems. In this work a simulation model for active control of machine-tool vibration in turning operations is described. The model contains both the mechanical structure and the control system. The simulation is done with and without active control. The structure vibration is suppressed by simulating actuators. The simulation is done to get a first indication of the potentials of a proposed new tool holder design and to test the usability of such multidisciplinary simulations as a supporting tool for product development. The results show that it is possible to simulate the total system. The vibrations of the tool holder tip could be decreased significantly by using reasonable forces. The software used was found to be very user friendly and to be able to perform such coupled simulations in this way during product development must be considered to be a great advantage.

  • 157. Jönsson, Anders
    et al.
    Broman, Göran
    Östholm, Stefan
    Multidisciplinary Simulation of Active Control of Machine-Tool Vibration in Turning2000Inngår i: System and Control:Theory and Applications, ISSN 960-8052-11-4, s. 61-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The increasing computer power in modern manufacturing machines has given the possibility to integrate advanced computer based control systems. In this work a simulation model for active control of machine-tool vibration in turning operations is described. The model contains both the mechanical structure and the control system. The simulation is done with and without active control. The structure vibration is suppressed by simulating actuators. The simulation is done to get a first indication of the potentials of a proposed new tool holder design and to test the usability of such multidisciplinary simulations as a supporting tool for product development. The results show that it is possible to simulate the total system. The vibrations of the tool holder tip could be decreased significantly by using reasonable forces. The software used was found to be very user friendly and to be able to perform such coupled simulations in this way during product development must be considered to be a great advantage.

  • 158. Jönsson, Anders
    et al.
    Wall, Johan
    Broman, Göran
    A Virtual Machine Concept for Real-Time Simulation of Machine Tool Dynamics2005Inngår i: International journal of machine tools & manufacture, ISSN 0890-6955, E-ISSN 1879-2170, Vol. 45, nr 7, s. 795-801Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When designing CNC machine tools it is important to consider the dynamics of the control, the electrical components and the mechanical structure of the machine simultaneously. This paper describes the structure and implementation of a concept for real-time simulation of such machine tools using a water jet cutting machine as an application. The concept includes a real control system, simulation models of the dynamics of the machine and a virtual reality model for visualisation. The real-time capability of the concept, including the simulation of electrical and rather detailed mechanical component models is proofed. The validation process indicates good agreement between simulation and measurement, but suggests further studies on servo motor, connection and flexibility modelling. However, already from the initial simulation results presented in this paper it can be concluded that the influence of structural flexibility on manufacturing accuracy is of importance at desired feeding rates and accelerations. The fully automated implementation developed in this work is a promising base for dealing with this trade-off between productivity and accuracy of the manufacturing process through multidisciplinary optimisation.

  • 159. Kamakura, Tomoo
    et al.
    Nomura, Hideyuki
    Akiyama, Masahiko
    Hedberg, Claes
    Parametric Sound Fields Formed by Phase-inversion Excitation of Primary Waves2011Inngår i: Acta Acustica united with Acustica, ISSN 1610-1928 , Vol. 97, nr 2, s. 209-218Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two planar ultrasound pro jectors having identical rectangular apertures were placed side by side. Both pro jectors radiated bifrequency primary waves in air. The frequencies were 26 and 28 kHz, and the initial phases were different. Two driving modes were considered, namely, conventional in-phase driving and phase-inversion driving. The spatial profiles of sound pressure fields were measured along and across the sound beam axis for the primary waves and a difference in frequency waves of 2 kHz. The second and third harmonic components of the difference frequency waves were also measured. The pressure levels of the primary waves were considerably suppressed near the beam axis owing to phase cancellation when the driving signals were phase-inversed, i.e., 180 degrees out of phase. The beam pattern of the difference frequency was, however, almost the same as that for the case in which the signals were in phase. Interestingly, the harmonic pressure amplitudes of the difference frequency were reduced by more than 10 dB. The validity of the experimental results were confirmed based on their good agreement with the theoretical predictions based on the Khokhlov-Zabolotskaya-Kuznetsov equation.

  • 160. Kao-Walter, Sharon
    A Visit to M.V. Lomonosov Moscow State University (June 2002)2002Annet (Annet vitenskapelig)
  • 161. Kao-Walter, Sharon
    Mechanical and Fracture Properties of Thin Al-foil2001Rapport (Annet vitenskapelig)
    Abstract [en]

    Mechanical and fracture behaviour of thin Aluminium foil (with a thickness of 6-9 mm) was studied. Tensile tests and fracture toughness tests of different material thickness and different specimen size have been performed. Results influence by the size of specimen has been discussed.

  • 162. Kao-Walter, Sharon
    On the Fracture of Thin Laminates2004Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis concerns mechanical and fracture properties of a thin aluminium foil and polymer laminate that is widely used as packaging material. The possibility of controlling the path of the growing crack propagation by adjustment of the adhesion level and the property of the polymer layer is investigated. First, the fracture process of the aluminium foil is investigated experimentally. It is found that fracture occurs at a much lower load than what is suggested by standard handbook fracture toughness. Observations in a scanning electron microscope with a tensile stage show that small-scale stable crack growth occurs before the stress intensity factor reaches its maximum. An examination using an optical profilometric method shows almost no plastic deformation except for in a small necking region at the crack tip. However, accurate predictions of the maximum load are obtained using a strip yield model with a geometric correction. Secondly, the mechanical and fracture properties of the laminate are studied. A theory for the mechanics of the composite material is used to evaluate a series of experiments. Each of the layers forming the laminate is first tested separately. The results are analysed and compared with the test results of the entire laminate with varied adhesion. The results show that tensile strength and strain at peak stress of the laminate, with or without a crack, increase when the adhesion of the adhesive increases. It is also found that a much larger amount of energy is consumed in the laminated material at tension compare with the single layers. Possible explanations for the much higher toughness of the laminate are discussed. Finally, the behaviour of a crack in one of the layers, perpendicular to the bimaterial interface in a finite solid, is studied by formulating a dislocation superposition method. The stress field is investigated in detail and a so-called T stress effect is considered. Furthermore, the crack tip driving forces are computed numerically. The results show that the analytical methods for an asymptotically small crack extension can also be applied for a fairly large amount of crack growth. By comparing the crack tip driving force of the crack deflected into the interface with that of the crack penetrating into the polymer layer, it is shown how the path of the crack can be controlled by selecting a proper adhesion level of the interface for different material combinations of the laminate.

  • 163.
    Kao-Walter, Sharon
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Andreasson, Eskil
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Ståhle, Per
    Micro-mechanism of Thin and Laminated Packaging Material during Fracture2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fracture path of a polymer coated and uncoated aluminium foil (about 6-7 um) is followed in a Scanning Electron Microscope. The crack length and applied load were measured during crack initiation and growth. The specimens’ cross section were then studied using the optical profilometric method to exam the deformed surface. For the uncoated Al-foil, no fracture surface can be observed. Fracture seems to occur through so-called necking. This behaviour was successfully modelled by a modified strip yield model. It leads to a conclusion that the crack tip is preceded a substantial plastic zone as compared with the crack length. The result was then compared to a polymer coated Al-foil. Further more, similar experimental works were performed on a polymer coated and uncoated Polypropylene. The results were discussed and compared to the cases with Al-foil layer.

  • 164. Kao-Walter, Sharon
    et al.
    Dahlström, J.
    Karlsson, T.
    Magnusson, A.
    A study of the relation between mechanical properties and adhesion level in a laminated packaging material2004Inngår i: Mechanics of composite materials, ISSN 0191-5665, E-ISSN 1573-8922, Vol. 40, nr 1, s. 29-36Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The mechanical properties of a laminate consisting of aluminum-foil, adhesive, and polymer layers were studied in relation to the adhesion level. A special application for liquid-food packaging materials was considered. In experiments, laminates with and without adhesive layers were tested. Tensile tests were first run for every layer of the laminate, and the data obtained were then used in analyzing the results of tensile tests on the entire laminate, as well as in theoretical and finite-element calculations. Relations between different mechanical properties (such as Young's modulus, the peak stress, and the strain at the peak stress) and the adhesion level were analyzed. It was found that the tensile strength and the strain at the peak stress increased with adhesion level. Only slight differences in Young's modulus were observed at different adhesion levels.

  • 165.
    Kao-Walter, Sharon
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Hu, Min
    Walter, Mats
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Leon, Armando
    A Comparison of 2-zone and 3-zone Models in Tearing based on Essential Work of Fracture2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Two different models (2-zone and 3-zone) for describing the deformation and fracture behavior of tearing ligament was compared and discussed based on the experimental results made by Kim et al. The models are based on the Essential Work of Fracture approach for predicting the specific total work of fracture along the tear path across plastic zones. The experiment and analysis were based on 2-leg trousers tear specimen. The materials chosen in this work were PET (0.508 mm). The results showed that the accuracy of 3-zone model was higher than 2-zone model. It was found that this difference is because the 2-zone model did not consider the plastic deformation caused by loading prior to tearing. Also a finite element model was created to simulate the behavior around the crack tip.

  • 166. Kao-Walter, Sharon
    et al.
    Huang, Yayu
    From Friendship Provinces to University Teacher/Student Exchange2009Konferansepaper (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    The establishment of the province friendship between Blekinge (Sweden) and Yunnan (China) has lead to a coperation agreement between two local Universities: Blekinge Institute of Technology and Kunming University of Science and Technology. It leads to the development of the cooperation of two provices in the fields of culture, business and education.

  • 167. Kao-Walter, Sharon
    et al.
    Levin, M.L.
    Petronyuk, J.S.
    Walter, Mats
    Acoustic imaging internal microstructure of a packaging material2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Microstructure of a paper-based packaging material was studied by acoustic microscopy method. The laminate structure of the packaging material contains paperboard, polymer and aluminium, which are widely used for aseptic liquid food package. The method has also been used to detect delaminations inside the material. The results show the possibility to study the micro structural features of paperboard, polymer and aluminium foil layered materials by applying the high-resolution ultrasonic acoustic microscopy. The potential for visualization defects in the body of this kind of materials is discussed in order to further develop the Non-Destructive Testing (NDT) method in food packaging industries.

  • 168. Kao-Walter, Sharon
    et al.
    Mfoumou, Etienne
    Laksman, Efraim
    Stress Relaxation of a Paper Sheet under Cyclic Load: An Experimental and Theoretical Model2010Inngår i: Materials Sciences and Applications, ISSN 2153-117X, E-ISSN 2153-1188, Vol. 1, nr 6, s. 317-322Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mechanical experiments have been performed to study the dynamic stress relaxation of a paper sheet material mainly used in food packaging industry. The material was cyclically tensile-loaded with a strain range between 2.4% and 4%. The time period for each cycle was 400 seconds. It was found that stress will decrease when the number of cycles increases in the case of upper load and vice versa in the case of lower load. At the same time, the stress to strain curves followed the same pattern as the one from the previous cycle. The stress relaxation behavior of each cycle has been analyzed and the dynamic relaxation modulus was derived. An improved model is proposed to describe the dynamic relaxation behavior of the paper sheet. This model shows a very good fit to the experimental results and trends of prediction are observed. Furthermore, the physical description of this model and the variation by the cycles is discussed.

  • 169.
    Kao-Walter, Sharon
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Mfoumou, Etienne
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Ndikontar, Maurice
    Mechanical Properties and Life-Cycle Sustainability Aspects of Natural Fibre2012Inngår i: Advanced Materials Research, TRANS TECH PUBLICATIONS LTD , 2012, Vol. 347-353, nr Part 1-7, s. 1887-1893Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In order to understand the basic definition of the natural material, references of recently published articles were studied. From these articles, the definition of different terms like renewable material, recyclable material, biodegradable material, sustainable material and finally natural material were collected. Furthermore, a classification of natural fibre was drawn. One of these natural fibres - the coconut was chosen for a more detail analysis in mechanical point of view. An integrated method to analyse the sustainability of the coconut fibre as one of the blend components in building construction will be suggested. Finally, several uses of the fibre are reviewed.

  • 170. Kao-Walter, Sharon
    et al.
    Ståhle, Per
    Fracture Behavior of an Ultra Thin Al-foil- Measuring and Modelling of the Fracture Process2001Konferansepaper (Fagfellevurdert)
  • 171. Kao-Walter, Sharon
    et al.
    Ståhle, Per
    Chen, S.H.
    A Finite Element Analysis of a Crack Penetrating or Deflecting into an Interface in a Thin Laminate2006Inngår i: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 312, s. 173-178Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The crack tip driving force of a crack growing from a pre-crack that is perpendicular to and terminating at an interface between two materials is investigated using a linear fracture mechanics theory. The analysis is performed both for a crack penetrating the interface, growing straight ahead, and for a crack deflecting into the interface. The results from finite element calculations are compared with asymptotic solutions for infinitesimally small crack extensions. The solution is found to be accurate even for fairly large amounts of crack growth. Further, by comparing the crack tip driving force of the deflected crack with that of the penetrating crack, it is shown how to control the path of the crack by choosing the adhesion of the interface relative to the material toughness.

  • 172. Kao-Walter, Sharon
    et al.
    Ståhle, Per
    Hägglund, Rickard
    Fracture toughness of a laminated composite2003Inngår i: Fracture of Polymers, Composites and Adhesives II, Elsevier , 2003, s. 355-364Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    The fracture toughness of a polymer-metal laminate composite is obtained by mechanical testing of a specimen containing a pre-crack. The result is compared with a calculated fracture toughness based on the measured fracture toughness of the individual layers. The laminate is a material used for packaging. It consists of a thin aluminium foil and a polymer coating. A centred crack panel test geometry is used. Each of the layers forming the laminate is also tested separately. It is observed that the load carrying capacity increases dramatically. At the strain when peak load is reached for the laminate only aluminium is expected to carry any substantial load because of the low stiffness of the LDPE. However, the strength of the laminate is almost twice the strength of the aluminium foil. The reason seems to be that the aluminium forces the polymer to absorb large quantities of energy at small deformation. The result is compared with the accumulated toughness of all involved layers. A more elaborate model is proposed in the light of non-linear material behaviour and development of a fracture process zone at the crack tip. Possible fracture of the interface between the layers is discussed.

  • 173. Kao-Walter, Sharon
    et al.
    Tryding, Johan
    Fracture mechanics of materials: From steel to packaging material2007Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The application of fracture mechanics started during the 20th century. By natural reason, most of the early research has been related to e.g. construction and defence industries. The fracture mechanics theories have been developed based on materials used by these industries, e.g. metals, plastic, concrete and soil materials. Later, along with the development of composite materials (and now even nano-materials), fracture mechanics theory was extended to include the fracture behaviour in composite materials. Nowadays, packaging industries utilize the fracture theories to enhance the package quality and cut the costs. Paper based packages for liquid food in ambient climate have been built up by the combination of paper, plastic and aluminium-foil. Research in this area has been done by the authors. It is found that many fracture related problems that occurs in the making of liquid food packages can be analyzed by the theory of fracture mechanics. However, it is the authors experience that to fully understand the interaction of the materials leading to fracture in the package laminate, further research in fracture of laminate is needed.

  • 174. Kao-Walter, Sharon
    et al.
    Walter, Mats
    Dasari, A
    Leon, Armando
    Tearing and Delaminating of a Polymer Laminate2011Inngår i: Key Engineering Materials, ISSN 1013-9826 , Vol. 465 , s. 169-174Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The fracture behaviour of laminated materials was studied in this work. The materials used in this work were low-density polyethylene (LDPE) laminated on polyethylene (PET). The thickness of the LDPE was 27 μm and the PET was 100 μm. Experiments were performed by using a 2-leg trousers specimen to analyse the tearing behaviour of the laminate in relation to the delamination. A clear delamination zone was observed during the crack propagation by tearing. Furthermore, a finite element calculation was performed to simulate the behavior around the crack tip during the tearing. A correlation between adhesion and crack propagation was discussed. Finally, the theory of Essential Work of Fracture (EWF) was used for predicting the specific total work of fracture along the tear path across the plastic zones.

  • 175. Kao-Walter, Sharon
    et al.
    Walter, Mats
    Muhammadi, A.B.
    Tensile and Tearing Fracture Behaviour of Food Packaging Laminate2007Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Fracture behaviour of laminated food packaging materials is studied. The materials used in this work were the single layer of Aluminium foil (Al-foil), Low density polyethylene (LDPE) and the lamination of these single layers. Experiments were performed by applying the centred crack specimen as well as the 2-leg trousers specimen. It was observed that the load carrying capacity increased for the tensile and decreased for the tearing specimen when the two layers are laminated together. It was also found that in the case of tearing the crack growth was not only initiated by shear stress but also by normal stress. A modified strip yield model and the essential work of fracture theory were used to analyze the deformation and the fracture behaviour. The initial crack growth of the single layers and the laminate during the tensile and tearing were compared and investigated.

  • 176.
    Kao-Walter, Sharon
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    You, Zhong
    Jiang, Xun
    Katangoori, Rahul Reddy
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Stress and Stability Analysis of a Building Column with a Pre-folded Origami Pattern2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A tubular structure by applying the pre-folded origami pattern has been developed at the department of Engineering Science, University of Oxford (see Figure 1). Most of the application is in vehicles. For further application possibility in the fields of Building, bridge, Subway or underground structure, stress and stability analysis were performed. Different cases were calculated by theory of instability and Finite Element Method. Different design solutions were introduced and their strength and stability properties were compared by loading the structure with a compression force on the top of the column. The objective of this work is to find a good solution in safety, sustainability and economy point of view. Failure risk due to the eventually pre-crack in structure will also be discussed by the theory of fracture mechanics.

  • 177. Karlsson, Anna
    et al.
    Törlind, Peter
    Johansson, Christian
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Managing Rejected Ideas from Projects— A Way to Avoid Idea Cemeteries2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An often neglected topic in idea management research is the continuity and stability of current idea management practices. This study addresses this topic by following a hand-over of ideas from a project to the line organization in a company. Moreover, idea portfolios are proposed and empirically explored as a means of managing and further developing these ideas. This particular idea-capturing scheme is believed to incorporate both codification and personalization approaches in the management of ideas. Twenty-one (21) semi-structured interviews, as well as observations, were conducted during a year, both before and during the implementation of idea portfolios at the company. Results from the study show the importance of considering the recipient of a codification effort in order for codification to become a constructive element rather than a barrier. Another finding is that different stages of maturity and levels of activity should be handled when managing ideas. Therefore, an idea portfolio is something of a hybrid between an idea bank and a register of on-going activities. Managing ideas in a transparent way was also shown to have its pros and cons. Increased transparency can both provide enhanced legitimacy for working with an idea, and increase the accountability of an idea, and can therefore be perceived as an obstacle. Finally, the shared responsibility of an idea that is the consequence of working with an idea portfolio can make the line manager something of an “accomplice”. This in turn helps in propelling the development of the idea forward.

  • 178.
    Karlsson, Hampus
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Karlsson, Anton
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Konceptutveckling av en caterpillar med inriktning på kvalitet: En utvecklingsprocess2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    When transporting a sea cable, what is commonly called a caterpillar is used, but the most common said is a cable tensioner. These machines can be found in a flurry of different variants, where there are a multitude of competitors, which applies demands to having an extremely distinctive machine. Therefore  from  a  market  analysis  it  have  been  identified  that  a  lack  of  quality  regarding  the machines are a factor. A poor quality shortage that usually occurs in hard weather conditions, but this is something that should not happen as it may lead to machine breakdown.

    Semcon AB in Karlskrona constructs and then collaborates with Ronneby Svets & Smide, who manufacture cable carousels, armrests and other equipment for the cable industry but not the cable tensioner that are ordered separately by external companies. This is the background to why the project is created because Semcon sees a need to eliminate this bottleneck and also expand their product portfolio for customer recovery. The aim it therefore, together with Semcon, develop a new concept for a completely  new cable tensioner with given preferences, rough drawing and selection of qualitative features for the machine in order to be competitive with its future overall solution for the cable industry.   

    To find a solution to the described problem, a product development process has been followed to establish  structure.  The  process  include  a  planning,  concept  development,  design  and  detailed development phase. From the first phase, a wide understanding of how the complex machine works and where its deficiencies may be. Even hidden customer needs in form of interviews with cable manufacturers in Karlskrona and with industries that handle sea cable were conducted to get a broader spectrum. The needs are transformed into specifications to generate concepts based on the rankings of the measurably formulated specifications. Followed up by an evaluation where the best concepts were taken to the design phase and detailed development. All design calculations have been made, either by hand or with computer-based programs.  

    The work has resulted in an innovative concept of a whole cable tensioner with all key components, rough drawing, together with a new thinking solution regarding the contact face between the cable and the machine, developed through experiments and theory studies. As this project is very broad, the overall project has been divided into two master thesis works and all electronics are handles by  an  electrical/automation  company.  Therefore,  for  a  broader  understanding  and  information about functionality, reference is made to the second project “Konceptutveckling kring funktionerna hos en kabeldragare” authored by Anton Hansson.  

    It is extremely important to mention that the outcome of this project is intended to be a concept for a new innovative cable tensioner. This means that with future work on the concept, which includes  continued  depth  of  calculation  and  further  contact  with  suppliers,  can  provide  an opportunity  to  manufacture  the  generated  concept.  Another  development  area  Semcon  must proceed with is to review the safety routines of the machine. The authors of this report believe that a highly competitive solution has been presented, and that work contributes to a strong foundation for  the  development  of  transporting  sea  cable  technology  in  the  future  with  the  help  of  this innovative concept.

  • 179.
    Katangoori, Rahul Reddy
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Kao-Walter, Sharon
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    You, Zhong
    Conceptual study on an origami patterns of type I tapered square tub with and without a crack2013Inngår i: Applied Mechanics and Materials, Trans Tech Publications, Switzerland , 2013, Vol. 275-277, s. 184-188Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Thin-walled tubes with origami patterns are popular design for the energy observing devices. However, less study has been done when they subjected to cracks. In this work, the origami square tube with different height to wall thickness ratio are first studied to investigate the collapse modes and deformation mode. Further more, stress concentration areas are identified by numerical simulations. Finally, horizontal and vertical crack was implemented in one of the side in order to study the effect on the deformation mode.

  • 180. Khamuknin, Alexander
    et al.
    Bertoni, Marco
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Eres, Hakki Murat
    Avoiding Resonant Frequencies in a Pipeline Application by Utilising the Concept Design Analysis Method2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Avoiding disasters due to the problems stemming from resonance is a major concern in any construction project. This becomes particularly important for oil and gas pipeline systems as some damages may lead to leakage of flammable fluids, explosions, fires, destruction and loss of life. The proximity to the natural frequencies of forced frequencies (frequency ratio) normally leads to intolerant resonant vibrations and catastrophic failures. A relevant case study on a partial pipeline design with an unacceptable level of frequency ratio is presented. In order to assess the overall design merit of the case study, the Concept Design Analysis (CODA) method is utilised to map captured Customer Needs (CNs) into Engineering Characteristics (ECs). As the frequency ratio is an important EC of the whole system, the improved CODA method for the pipeline design introduces an avoidance type merit function that allows excluding a range of relevant ECs. This improved CODA method is demonstrated in a model whereby certain frequency ratios are successfully avoided in the final design.

  • 181.
    Kianian, Babak
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Larsson, Tobias
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Tavassoli, Mohammad
    Blekinge Tekniska Högskola, Sektionen för management.
    Manufacturing Renaissance: Return of manufacturing to western countries2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Manufacturing Renaissance, i.e. return of manufacturing to west, has been recently observed. This paper analyzes the patterns observed within each of the four main drivers behind this new phenomenon and delves more deeply into the driver that centers on the new manufacturing technologies such as Additive Manufacturing (AM) and 3D Printing. Next, this paper will make the case that the location of manufacturing will be in west, relying on the established theory that has been able to explain the location of manufacturing, i.e. Product Life Cycle Model (PLC).

  • 182.
    Kianian, Babak
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Tavassoli, Sam
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för industriell ekonomi.
    Larsson, Tobias C
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    The Role of Additive Manufacturing Technology in job creation: an exploratory case study of suppliers of Additive Manufacturing in Sweden2015Inngår i: Procedia CIRP, Elsevier , 2015, Vol. 26, s. 93-98Konferansepaper (Fagfellevurdert)
    Abstract [en]

    his paper investigates how Additive Manufacturing (AM) technologies, as a process innovation, may contribute to a job creation. Further, the various mechanisms in which AM may contribute to an increase in job creation as well as the types of jobs are analyzed. The analysis also goes beyond AM technologies and incorporates other non-technological factors which foster job creation, i.e. higher wages in BRIC countries, lower quality in BRIC countries, and a rising demand for western-made products. The analysis is based on a case study and the data collected was through interviews with three prominent actors within the AM technologies field in Sweden: technology developers, leading suppliers and users. The main findings indicate that AM (i) contributes to job creation in both the manufacturing sector and in the service sector, (ii) does not bring back mass production jobs from emerging economies such as BRIC, (iii) contributes to job creation in product development stages (e.g. rapid prototyping), and (iv) contributes to job creation in production stages of low-volume batches mainly of complex products. The findings also suggest there are barriers for full exploitation of AM in several areas, including education systems.

  • 183.
    Knutsson, Simon
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Larmark, Daniel
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Modular Communications Relay for Autonomous Quarry Operation2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Today’s quarries face a change in the operational processes, where the development of automated transport systems and machines have intensified the necessity for reliable and stable data transfer. Within the dynamic environment, with piles building up suddenly, frequently changing mining faces due to blasting, as well as a frequently changing general environment that affect the network coverage negatively, there is a need for a solution that can adapt to the changing environment.

    The aim of this research has been to investigate the requirements for a dynamic infrastructure, and develop a platform based on today’s available technical solution components that can act as a dynamic platform for the evolving autonomous quarry. This by also reducing the time the worker is exposed to the harsh environment that the quarry presents.

    The research was conducted through a combination of a product development strategy and Design Research Methodology to develop a concept that fulfills the customer needs that are identified. An iterative process, where the needs were translated in to prototypes, has created learnings through every step of the development process.

    The result is a relocatable platform for communications relay, which is mounted on a trailer with a fixed mast to distribute short-wave communications in the area where the mobile unit is needed. The trailer is equipped with a four-point leveling system that also act as a stabilization system for the unit and ensures that the platform maintains a horizontal plane at all times. This platform is a first step towards a fully autonomous management of the communication infrastructure which in the future will be needed when a stable process and connection is necessary in the frequently changing environment. The relocatable platform is a necessity for adaption of the short-wave communication in the constantly changing environment.

    Since this is a first iteration and concept in the development of a dynamic platform, extensive field tests are required to determine which subcomponents are in need of further development or optimization. The completed prototype for the platform is functional and field ready for further testing in its real environment for further collecting of data points. This concept is a subcomponent of a larger system, where the goal is to increase the productivity and reduce the environmental impact from today’s quarry industry. Through reduction of human interaction and management of the relocation of the mobile unit, the workers safety is increased and the harsh environmental exposure is reduced.

  • 184.
    Kodavati, Venkata Seshank
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Buraga, Devi Prasad
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Study of Numerical Model Parameters and Crack Tip of a Packaging Materials2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Packaging industries widely use Low-Density Polyethylene (LDPE) in manufacturing different types of containers to store the food products. They are difficult to model numerically in order to have similar experimental response. This research deals with the study of numerical material model parameters of continuum LDPE. It is carried out with the help of experiments along with the numerical simulation of LDPE. Study of stress-strain distribution at crack tip and elements close to the tip is carried out in the LDPE material with the pre-existing center crack with varying lengths. By implementing an optimization algorithm and automating the simulation with the help of python code, we obtain a set of parameters. This obtained data for the material can be used directly for numerical simulation in the future without carrying out additional experimental studies. After implementing the optimization algorithm is also validated, against the results that were close to the experimental response. 

  • 185. Lagö, Thomas L
    et al.
    Olsson, Sven
    Håkansson, Lars
    Claesson, Ingvar
    Design of an Efficient Chatter Control System For Turning and Boring2002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the turning operation chatter or vibration is a frequent problem, which affects the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. In all cutting operations like turning, boring and milling vibrations are induced due to the deformation of the workpiece. This implies several disadvantages, economical as well as environmental. Many different solutions to minimize the problem have been developed but the fundamental problem is still there. The true nature of the vibrations, its causes, and implications were revealed in a doctor’s thesis in 1999. This has led to a break through in this research area. Since then, through recent research results at Blekinge Institute of Technology, a new approach to controlling vibrations in cutting operations in a lathe has been implemented in a product called ActicutTM, developed by Active Control Sweden AB. This new method controls vibrations in the cutting direction.

  • 186. Lagö, Thomas L
    et al.
    Olsson, Sven
    Håkansson, Lars
    Claesson, Ingvar
    Performance of a Chatter Control System for Turning and Boring Applications2002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the turning operation chatter or vibration is a frequent problem, which affects the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. In all cutting operations like turning, boring and milling vibrations are induced due to the deformation of the workpiece. This implies several disadvantages, economical as well as environmental. Many different solutions to minimize the problem have been developed but the fundamental problem is still there. The true nature of the vibrations, its causes, and implications were revealed in a doctor’s thesis in 1999, [1]. This has led to a break through in this research area. Since then, through recent research results at Blekinge Institute of Technology, a new approach to controlling vibrations in cutting operations in a lathe has been implemented in a product called Acticut®, developed by Active Control Sweden AB. This new method controls vibrations in the cutting direction using embedded sensors and actuators and a filtered-x LMS algorithm. This paper will discuss the application but also the algorithm and its main numerical properties to accomplish a good result, still maintaining its stability properties.

  • 187. Leon, Armando
    Non-Linear Vibration and Dynamic Fracture Mechanics of Bridge Cables2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In the present work, the non-linear vibrations and the corresponding dynamic fracture mechanics of cables of cable-stayed bridges are studied. The cables are among the most critical components in cable-stayed bridges and there are different damage sources such as corrosion, vibration, fatigue and fretting fatigue that can significantly affect them, thereby reducing the cable’s service life and even producing their failure. Cable-Parametric Resonance is the specific non-linear vibration studied in this research. This type of vibration occurs due to displacements presented at the cable supports. These displacements are induced by the wind and traffic loads acting on the pylon and deck of the bridge. Under certain conditions, unstable cable-vibration of significant amplitude can be registered. Therefore, numerical and experimental analyses are carried out in order to describe this phenomenon and to determine the corresponding instability conditions. Two non-linear models of cable-parametric resonance are studied to predict the cable response. In the simulation method, the non-linear components are treated as external forces acting on the linear systems, which are represented by Single Degree of Freedom systems and described by digital filters. A clear non-linear relationship between the excitation and the cable response is observed in the simulations and the experiments. The corresponding experimental analysis is based on a scaled model (1:200) of the Öresund bridge and a good agreement between the numerical and experimental results is found. After obtaining the relationship between the cable response and the excitation, the cable instability conditions are determined. This is done by finding the minimum displacement required at the cable supports in order to induce nonlinear cable vibration of considerable amplitude. The instability conditions are determined within a wide range of excitation frequencies and conveniently expressed in a simplified and practical way by a curve. The determination process is rather fast and offers the possibility to evaluate all bridge cable stays in a rather short time. Finally, the dynamic fracture mechanics of the cable is considered by studying the fracture toughness characteristics of the material under dynamic conditions. Finite Element simulations on a pre-cracked three-point bending specimen under impact loading are performed. The observed cable instability is equivalently considered as the associated response to impact load conditions, and a crack as a defect on the wires of a cable stay. The simulations are based on an experimental work by using the Split Hopkinson pressure bar (Jiang et al). The dynamic stress intensity factor KI(t) up to crack initiation is then obtained by different methods. The numerical estimations based on the specimen’s crack tip opening displacement (CTOD) and mid-span displacement were closest to the experimental results. It is observed that a better estimation of the dynamic stress intensity factor relies on a proper formulation of the specimen’s stiffness.

  • 188.
    Leon, Armando
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Ahlin, Kjell
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Kao-Walter, Sharon
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    On Determining Instability Conditions for Stay Cables Subjected to Parametric Resonance2009Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Parametric Resonance Vibration in cables of cable-stayed bridges is mainly studied when the excitation frequency is close to or twice the cable natural frequency. It is, however, important to consider other cases for this frequency relationship, since among other factors, cable-parametric resonance vibrations are strongly depending on the displacement amplitude at the cable supports. Consequently, the present research work is focused on determining, by experimental and numerical analysis, the instability conditions for stay cables subjected to parametric resonance within a wide range of frequency ratios. This is accomplished, by finding the minimum displacement required at the cable supports in order to induce non-linear vibration of considerable amplitude at the cable. Once the cable characteristics (geometry, material properties, inherent damping and initial tensile preload) are known, the instability conditions are identified and expressed in a simplified and practical way in a diagram. Numerical results are compared to those obtained by experimental analysis carried out on a simplified scaled model (1:200) of the Öresund Bridge. A good agreement between numerical and experimental results is found.

  • 189. Leon, Armando
    et al.
    Josefsson, Andreas
    Ahlin, Kjell
    Simulations and Identification of Non-Linear Models for Cables of Cable-Stayed Bridges2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Simulations and identification of non-linear parameters are applied on two models that describe the vibration due to parametric resonance in cables of cables-stayed bridges. The aim of this work is to study the dynamic response predicted by the two models under random excitation, as well as to develop a suitable strategy for system identification from random data. In one model the parametric excitation is treated as an arbitrary displacement introduced in one end of the cable. In the second model, such excitation is coming from an external force acting on the pylon or deck of the bridge to which the cable is coupled. The pylon or deck is modeled as a Single Degree of Freedom System. In both models the cable response is obtained by a simulation method based on digital filters. The studied identification technique is based on random excitation. In this method the non-linearity is modeled as a feedback forcing term acting on an underlying linear system or systems and the parameter estimation is performed in the frequency domain by using conventional MI/SO techniques.

  • 190. Lichtenberg, Alexandra
    et al.
    Gurimaraes, Patricia
    Podsedkowska, Heleen
    Planning for Sustainable Mobility with Personal Rapid Transit in Small European Cities2010Konferansepaper (Fagfellevurdert)
  • 191.
    Lindahl, Pia
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Approaching Strategic Sustainable Materials Management2013Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Society’s sustainability challenges relatedto materials management have been an area of concern for policymakers, industry and the public for decades. However, if those challenges are managed in a strategic way, they are not only aproblem, but could also bring in new opportunity for companies and other organizations to improve their competitiveness through developingproduct-service systems that promote sustainable development of society. The overall aim of this thesis is to explore how aframework for strategic sustainable development (FSSD) can support the development and design of sustainable materials management strategies in product innovation. This is achieved by four studies investigating howsustainability considerations are, or could be, integrated in decisions regarding materials selection. The studies are informed by the FSSD, Maxwell’s model for qualitative research design and the design research methodology. The first study is a theoretical discussion which provides a base for the following three exploratory studies. The exploratory studies have, through literature reviews and semi-structured interviews, investigated general sustainabilityconsiderations in companies, made a comparison of the strategic potential of two product improvement strategies and finally studied what considerations that are in focus and what types of solutions that are revealed when companies apply a strategic sustainability perspective to materials management. The studies have shown that decisions regarding materials management often arebased on compliance with legislation and on avoiding substances with characteristics commonly considered problematic (such as toxicity, persistency, etc.), and that decision support regarding how materials could be managed in a sustainable way are lacking. However, the results also include some examples from companies that have successfully developed pro-active strategies towards sustainable materials management. They have approached this through managing materials in closedtechnical loops, enabled material substitution through value chain collaboration and reduced material flows through new and innovative design. Most importantly, they have assessedactions not only regarding their potential to reduce a selection of current socio-ecological impacts but also regarding their potential to link toforthcoming actions towards the full scope of socio-ecological sustainability. Through this approach, they have found several ways by which materials with characteristics that are commonly considered problematic can be. The results highlight the possibility of enabling sustainable materials management practices by using a strategic sustainability perspective in combination with material characteristics knowledge and that a static division of “sustainable” vs. “unsustainable” materials (e.g., through lists of forbidden and allowed materials) is not necessarily serving the purpose in the best way. More subtle considerations are needed. By not applying a strategic sustainability perspective to materials management, organizations risk using “sustainable” materials in unsustainable ways or phasing out “unsustainable” materials that, managed differently, could be helpful for sustainable development. Developing decision support for materials management that integrates this new way of thinking will be the focus of future work.

  • 192.
    Lindahl, Pia
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för strategisk hållbar utveckling.
    Robèrt, Karl-Henrik
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för strategisk hållbar utveckling.
    Ny, Henrik
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för strategisk hållbar utveckling.
    Broman, Göran
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för strategisk hållbar utveckling.
    Strategic sustainability considerations in materials management2014Inngår i: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 64, nr feb 2014, s. 98-103Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Increasing awareness in business and society regarding socio-ecological impacts related to society's use of materials is a driver of new materials management practices. The aim of this study is to gain insight into what considerations come into focus and what types of solutions are revealed when companies apply a strategic sustainability perspective to materials management. Through literature reviews and semi-structured interviews we found that the companies studied have assessed material choices and related management actions, not only regarding their potential to reduce a selection of current socio-ecological impacts, but also regarding their potential to link to future actions to move towards the full scope of socio-ecological sustainability. Through this approach, these companies have found several ways through which materials with characteristics that are commonly considered problematic can be managed sustainably by making strategic use of some of these “problematic” characteristics and other characteristics of the materials. For example, a material associated with problems at end of life, could be managed in closed loops facilitated by the persistence of the material. Based on the findings, we conclude that by not applying a strategic sustainability perspective to materials management, organizations risk phasing out materials perceived to be unsustainable which, managed differently, could be helpful for sustainable development.

  • 193. Lindberg, Gustav
    et al.
    Shokry, Abdallah
    Reheman, Wureguli
    Lunds universitet, LTH, SWE.
    Svensson, Ingrid
    Determination of diffusion coefficients in bovine bone by means of conductivity measurement2014Inngår i: International Journal of Experimental and Computational Biomechanics, ISSN 1755-8743, Vol. 2, nr 4, s. 324-342Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Measuring the diffusivity of various substances in cortical bone is in general difficult. For instance, making use of micro computed tomography requires agents that can be separated from bone, blood and other substances that exist in cortical bone. Here a more easily accessible method is presented. A series of cortical bovine bone samples were put in a saturated solution of potassium chloride for a time period that was long enough for the samples to be regarded as saturated. The samples were removed from the solution and moulded in polyester leaving only the radial directions open. In the next step, the bone samples were put in distilled water and the conductivity of the water was registered over time. An analytical model fulfilling Ficks law was introduced and by means of Kalman filtering an estimation for the diffusion coefficient of potassium chloride in bovine bone is presented.

  • 194. Lindberg, Vanja
    First principles study of CO reactivity on metallic nano particles2007Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The activity of a surface is determined by the local electronic structure. When nano particles are adsorbed, the catalytic properties will change. Surfaces with adsorbed nano particles often show a significantly higher chemical reactivity than the clean counterpart. Gold, for instance, shows an extra high activity towards many reactions, such as low-temperature catalytic combustion, partial oxidation of hydrocarbons and CO oxidation when dispersed as ultra-fine particles on metal oxide surfaces. In the case of CO oxidation, the activity has been observed to depend critically on the nano particle size, the nature of the support and the detailed synthetic procedure. Since it has been observed experimentally that the chemical reactivity of a nanoparticulated surface tend to depend on the size of the adatom structures, suggesting a quantum size effect, we find it well motivated to perform a theoretical investigation with focus on the cluster-size dependence. We have chosen to model CO interaction with sodium nano particles with focus on small particles, containing only a few atoms, since we expect the eventual quantum effects to be most pronounced for these. Further, we limit our investigation to unsupported nano particles because our previous investigations [1] have shown that it is predominately states localized to the nano particle region that contribute to the local electronic structure above the particle itself. The calculations have been performed in the context of density functional theory applying the MIKA real-space program package [2], using norm-conserving pseudo-potentials for the molecule. The nano particle has been modeled as a cylindrically symmetric quantum dot. For further details, see [3,4]. Our results show that the charge transfer between the nano particle and the CO molecule depends critically on the nano particle size, and that this dependence is intimately connected to the local electronic structure at the point where the molecule approaches the particle. The key factor for charge transfer turns out to be the presence of states with the symmetry of the chemically active molecular orbital at the Fermi level. [1] T. Torsti, V. Lindberg, M. J. Puska ,and B. Hellsing, Phys. Rev. B 66, 235420 (2002). [2] M. Heiskanen, T. Torsti, M. J. Puska, and R. M. Nieminen, Phys. Rev. B 63, 245106 (2001). [3] V. Lindberg and B. Hellsing, J. Phys. Condens. Matter 17, S1075 (2005). [4] V. Lindberg, T. Petersson, and B. Hellsing, Surf. Sci. 600, 6 (2006).

  • 195. Magnevall, Martin
    Methods for Simulation and Characterization of Nonlinear Mechanical Structures2008Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Trial and error and the use of highly time-consuming methods are often necessary for modeling, simulating and characterizing nonlinear dynamical systems. However, for the rather common special case when a nonlinear system has linear relations between many of its degrees of freedom there are particularly interesting opportunities for more efficient approaches. The aim of this thesis is to develop and validate new efficient methods for the theoretical and experimental study of mechanical systems that include significant zero-memory or hysteretic nonlinearities related to only small parts of the whole system. The basic idea is to take advantage of the fact that most of the system is linear and to use much of the linear theories behind forced response simulations. This is made possible by modeling the nonlinearities as external forces acting on the underlying linear system. The result is very fast simulation routines where the model is based on the residues and poles of the underlying linear system. These residues and poles can be obtained analytically, from finite element models or from experimental measurements, making these forced response routines very versatile. Using this approach, a complete nonlinear model contains both linear and nonlinear parts. Thus, it is also important to have robust and accurate methods for estimating both the linear and nonlinear system parameters from experimental data. The results of this work include robust and user-friendly routines based on sinusoidal and random noise excitation signals for characterization and description of nonlinearities from experimental measurements. These routines are used to create models of the studied systems. When combined with efficient simulation routines, complete tools are created which are both versatile and computationally inexpensive. The developed methods have been tested both by simulations and with experimental test rigs with promising results. This indicates that they are useful in practice and can provide a basis for future research and development of methods capable of handling more complex nonlinear systems.

  • 196. Magnevall, Martin
    Simulation and Experimental Methods for Characterization of Nonlinear Mechanical Systems2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Trial and error and the use of highly time-consuming methods are often necessary for investigation and characterization of nonlinear systems. However, for the rather common case where a nonlinear system has linear relations between many of its degrees of freedom there are opportunities for more efficient approaches. The aim of this thesis is to develop and validate new efficient simulation and experimental methods for characterization of mechanical systems with localized nonlinearities. The purpose is to contribute to the development of analysis tools for such systems that are useful in early phases of the product innovation process for predicting product properties and functionality. Fundamental research is combined with industrial case studies related to metal cutting. Theoretical modeling, computer simulations and experimental testing are utilized in a coordinated approach to iteratively evaluate and improve the methods. The nonlinearities are modeled as external forces acting on the underlying linear system. In this way, much of the linear theories behind forced response simulations can be utilized. The linear parts of the system are described using digital filters and modal superposition, and the response of the system is recursively solved for together with the artificial external forces. The result is an efficient simulation method, which in conjunction with experimental tests, is used to validate the proposed characterization methods. A major part of the thesis addresses a frequency domain characterization method based on broad-band excitation. This method uses the measured responses to create artificial nonlinear inputs to the parameter estimation model. Conventional multiple-input/multiple-output techniques are then used to separate the linear system from the nonlinear parameters. A specific result is a generalization of this frequency domain method, which allows for characterization of continuous systems with an arbitrary number of localized zero-memory nonlinearities in a structured way. The efficiency and robustness of this method is demonstrated by both simulations and experimental tests. A time domain simulation and characterization method intended for use on systems with hysteresis damping is also developed and its efficiency is demonstrated by the case of a dry-friction damper. Furthermore, a method for improved harmonic excitation of nonlinear systems using numerically optimized input signals is developed. Inverse filtering is utilized to remove unwanted dynamic effects in cutting force measurements, which increases the frequency range of the force dynamometer and significantly improves the experimental results compared to traditional methods. The new methods form a basis for efficient analysis and increased understanding of mechanical systems with localized nonlinearities, which in turn provides possibilities for more efficient product development as well as for continued research on analysis methods for nonlinear mechanical structures.

  • 197. Magnevall, Martin
    et al.
    Josefsson, Andreas
    Ahlin, Kjell
    Experimental Verification of a Control Algorithm for Nonlinear Systems2006Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    When using electrodynamic vibration exciters to excite structures, the actual force applied to the structure under test is the reaction force between the exciter and the structure. The magnitude and phase of the reaction force is dependent upon the characteristics of the structure and exciter. Therefore the quality of the reaction force i.e. the force applied on the structure depends on the relationship between the exciter and structure under test. Looking at the signal from the force transducer when exciting a structure with a sine wave, the signal will appear harmonically distorted within the regions of the resonance frequencies. This phenomenon is easily observed when performing tests on lightly damped structures. The harmonic distortion is a result of nonlinearities produced by the shaker when undergoing large-amplitude vibrations, at resonances. When dealing with non-linear structures, it's of great importance to be able to keep a constant force level as well as a non-distorted sine wave in order to get reliable results within the regions of the resonance frequencies. This paper presents the method and results from an experimental test creating a nondistorted excitation signal with constant force level.

  • 198. Magnevall, Martin
    et al.
    Josefsson, Andreas
    Ahlin, Kjell
    On Nonlinear Parameter Estimation2006Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The industrial demand on good dynamical simulation models is increasing. Since most structures show some form of nonlinear behavior, linear models are not good enough to predict the true dynamical behavior. Therefore nonlinear characterization, localization and parameter estimation becomes important issues when building simulation models. This paper presents identification techniques for nonlinear systems based on both random and harmonic excitation signals. The identification technique based on random excitation builds on the well known reverse-path method developed by Julius S. Bendat. This method treats the nonlinearity as a feedback forcing term acting on an underlying linear system and the parameter estimation is performed in the frequency domain by using conventional MISO/MIMO techniques. Although this method provides a straightforward and systematic way of handling nonlinearities, it has been somewhat limited in use due to the complexity of creating uncorrelated inputs to the model. As is shown in this paper, the parameter estimation will not be improved with conditioned inputs and the nonlinear parameters and the underlying linear system can still be estimated with partially correlated inputs. This paper will also describe a parameter estimation method to be used with harmonic input signals. By using the principle of harmonic balance and multi-harmonic balance it is possible to estimate an analytical frequency response function of the studied nonlinear system. This frequency response function can, in conjunction with measured nonlinear transfer functions, be used to estimate the nonlinearity present in the system. This method is also applicable on nonlinear systems with memory, e.g. systems with hysteresis effects. The above mentioned methods are applied to multi-degree-of-freedom and single-degree-of-freedom systems with different types of nonlinearities. Also, techniques for locating nonlinearities are discussed.

  • 199. Magnevall, Martin
    et al.
    Josefsson, Andreas
    Ahlin, Kjell
    Parameter Estimation of Hysteresis Elements Using Harmonic Input2007Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The industrial demand on good dynamical simulation models is increasing. Since most structures show some form of nonlinear behavior, linear models are not good enough to predict the true dynamical behavior. Hysteresis is a highly nonlinear phenomenon which occurs in for example dampers and mechanical joints. This paper presents a method for parameter estimation on nonlinear systems under harmonic excitation. By using the principle of harmonic balance or multi harmonic balance a theoretical frequency response function of the studied system can be estimated. This frequency response function can, in conjunction with measured nonlinear transfer functions, be used to make parameter estimations of the nonlinearity present in the system. A major benefit using this method is the ability to use arbitrary nonlinear functions. This means that the method can be applied to nonlinear systems with memory, for instance systems with hysteresis effects. The method is applied to both simulated systems and an experimental test rig.

  • 200.
    Magnevall, Martin
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för matematik och naturvetenskap.
    Josefsson, Andreas
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Ahlin, Kjell
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Broman, Göran
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Nonlinear structural identification by the "reverse Path" spectral method2012Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 331, nr 4, s. 938-946Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When dealing with nonlinear dynamical systems, it is important to have efficient, accurate and reliable tools for estimating both the linear and nonlinear system parameters from measured data. An approach for nonlinear system identification widely studied in recent years is "Reverse Path". This method is based on broad-band excitation and treats the nonlinear terms as feedback forces acting on an underlying linear system. Parameter estimation is performed in the frequency domain using conventional multiple-input-multiple- output or multiple-input-single-output techniques. This paper presents a generalized approach to apply the method of "Reverse Path" on continuous mechanical systems with multiple nonlinearities. The method requires few spectral calculations and is therefore suitable for use in iterative processes to locate and estimate structural nonlinearities. The proposed method is demonstrated in both simulations and experiments on continuous nonlinear mechanical structures. The results show that the method is effective on both simulated as well as experimental data.

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