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  • 1.
    Bertoni, Marco
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Pezzotta, Giuditta
    University of Bergamo, ITA.
    Scandella, Beatrice
    Uiversity of Bergamo, ITA.
    Wall, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Jonsson, Pontus
    Dynapac Compaction Equipment, SWE.
    Life cycle simulation to support cross-disciplinary decision making in early PSS design2019In: Procedia CIRP, Elsevier, 2019, Vol. 83, p. 260-265Conference paper (Refereed)
    Abstract [en]

    The development of early-stage simulation capabilities is a critical step in the quest for ‘frontloading’ early stage PSS design activities, reducing the cost and risk for rework associated with sub-optimal decisions. This paper describes how life cycle simulations, based on a Discrete Event approach, can be applied to support cross-disciplinary decision making in PSS design, facilitating the identification of the most valuable hardware configuration for a given business model. The proposed approach is exemplified in a case study related to the design of a zero-emission asphalt compactor, which is part of a product-oriented and use-oriented PSS offer. Co-located physical meetings and interviews with industrial practitioners highlight the role played by the simulation as an enabler for leveraging tacit knowledge sharing across roles and disciplines in the organization, making possible to explore the design space with more rigor. They further reveal the need to exploit data mining techniques and to develop new constructs able to inform decision makers of maturity and impact of models used in a specific decision scenario.

  • 2.
    Bertoni, Marco
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Wall, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Bertoni, Alessandro
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Model Driven Decision Arena: an aerospace study2018In: Proceedings of the International Design Conference / [ed] D. Marjanović, M. Štorga, S. Škec, N. Bojčetić, N. Pavković (eds.), The Design Society, 2018, Vol. 1, p. 171-182Conference paper (Refereed)
    Abstract [en]

    The concept of Decision Theatre (DT) is of great interest to leverage knowledge sharing in early stage design decision events. Yet, few contributions show how to configure a DT to support design space exploration and concept selection in cross-functional teams. This paper describes the development of a model-driven decision arena (MDDA) for aero-engine sub-system design. After presenting the descriptive study findings, it illustrates the overall logic of the MDDA environment and exemplifies its use in a case study related to the design of a turbine real structure (TRS) for commercial use.

  • 3. Broman, Göran
    et al.
    Jönsson, Anders
    Wall, Johan
    Englund, Thomas
    Introductory Optimisation Study of a Rammer Soil Compactor Machine2001Conference paper (Refereed)
    Abstract [en]

    Rammer compactor machines perform dynamic soil compaction. 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 and a procedure for optimisation as design parameters are changed during product development. In this paper a theoretical model of the rammer machine in combination with a soil model is described. This multi-body dynamics system is solved numerically. The system is non-linear and chaotic behaviour is possible. This parameter sensitivity emphasises the need for this kind of simulations in the product development process. A fairly regular behaviour is necessary for a predictable and safe operation. Parameter combinations giving too irregular behaviour are non-feasible. The energy transfer rate from the rammer machine into the soil is used as the objective function for optimisation. Multi-start Sequential Quadratic Programming for optimum search is used. To cover the design space well a Uniform Experimental Design is used for selection of starting points. This procedure proves to work well for the problem of this introductory study. The study shows a significant potential for improved compaction capacity although considering only the three design parameters that are most easily changed in practice. Approximately the same optimum is obtained both for operation on soft soil and hard soil, so a good all-round design seems possible. Including this theoretical support in the product development process should make it much more effective in finding optimum designs, also for other machines of similar type.

  • 4.
    Byggeth, Sophie
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Ny, Henrik
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Wall, Johan
    Broman, Göran
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Robèrt, Karl-Henrik
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Introductory Procedure for Sustainability-Driven Design Optimization2007Conference paper (Refereed)
    Abstract [en]

    In response to the increasingly competitive global market, there is a growing interest in design optimization. Being able to include aspects of socio-ecological sustainability in product design should aid companies to both improve current competitiveness and to identify viable long-term investment paths and new business opportunities in the evolving sustainability-driven market. A case study of a water jet cutting machine is used to illustrate a new iterative optimization procedure that combines a technical assessment with a sustainability assessment. Sustainability assessment methods/tools are first used to identify prominent sustainability problems from present-day flows and practices (“societal indicators”) and to generate ideas of long-term solutions and visions. Based on this, preliminary ideas about likely desirable changes in machine properties are obtained. Technical investigations are then performed to assess if/how these particularly desirable changes in machine properties could in principle be realized through changes in design variables. After that, obtainable changes are fed back to a new and more refined sustainability assessment to find out the societal implications of these changes. This may in turn result in other desirable design changes, which may call for a new and more refined technical assessment, etcetera. The experience from the case study indicates that the suggested integrated and iterative working procedure should be able to add information about socio-ecological impacts of product properties and influence design criteria used in prioritisation situations during product development.

  • 5. Englund, Thomas
    et al.
    Wall, Johan
    Ahlin, Kjell
    Broman, Göran
    Automated updating of simplified component models for exhaust system dynamics simulations2002Conference paper (Refereed)
    Abstract [en]

    To facilitate overall lay-out optimisation simplified component models for dynamics simulations of automobile exhaust systems are desired. Such optimisation could otherwise be computationally expensive, especially when non-linear analyses are necessary. Suggestions of simplified models of the mufflers and the catalyst are given. To account for the flexibility at the connections between those components and the pipes short beam elements with individual properties are introduced at these locations. An automated updating procedure is developed to determine the properties of these beam elements. Results from an experimental modal analysis are used as the reference. The theoretical model of the exhaust system is built in the finite element software ABAQUS. The updating procedure uses the sequential quadratic programming algorithm included in the Optimization Toolbox of the software MATLAB to minimise the sum of the differences between experimentally and theoretically obtained natural frequencies. Constraints are used on the correlation between the experimentally and theoretically obtained mode shapes by considering the MAC-matrix. Communication between the two software packages is established by an in-house MATLAB script. The correlation between results from the updated theoretical model and the experimental results is very good, which indicates that the updating procedure works well.

  • 6. Englund, Thomas
    et al.
    Wall, Johan
    Ahlin, Kjell
    Broman, Göran
    Dynamic characteristics of a combined bellows and liner flexible joint2004In: Journal of Automobile Engineering, ISSN 0954-4070 , Vol. 218, no 5, p. 485-493Article in journal (Refereed)
    Abstract [en]

    A bellows combined with an inside liner and an outside braid is commonly used as a flexible joint in automobile exhaust systems to reduce transmission of engine movements to the exhaust system. It greatly influences the dynamics of the complete system. Understanding of its dynamic characteristics and a modelling method that facilitates systems simulation are therefore desired. This has been obtained in earlier works for the bellows itself. In this work an approach to the modelling of the combined bellows and liner joint is suggested and experimentally verified. Simulations and measurements show that the liner adds significant non-linearity and makes the characteristics of the joint complex. Results are presented for the axial and the bending load cases. In torsion, influence of the liner is negligible. Peak responses are significantly reduced when the excitation level approximately corresponds to the friction limit of the liner. The complexity of the combined bellows and liner joint is important to know of and consider in exhaust system design and proves the necessity of including a model of the liner in the theoretical joint model when this type of liner is present in the real joint to be simulated.

  • 7. Englund, Thomas
    et al.
    Wall, Johan
    Ahlin, Kjell
    Broman, Göran
    Significance of non-linearity and component-internal vibrations in an exhaust system2002Conference paper (Refereed)
    Abstract [en]

    To facilitate overall lay-out optimisation inexpensive dynamics simulation of automobile exhaust systems is desired. Identification of possible non-linearity as well as finding simplified component models is then important. A flexible joint is used between the manifold and the catalyst to allow for the motion of the engine and to reduce the transmission of vibrations to the rest of the exhaust system. This joint is significantly non-linear due to internal friction, which makes some kind of non-linear analysis necessary for the complete exhaust system. To investigate the significance of non-linearity and internal vibrations of other components a theoretical and experimental modal analysis of the part of a typical exhaust system that is downstream the flexible joint is performed. It is shown that non-linearity in this part is negligible. It is also shown that shell vibrations of the catalyst and mufflers as well as ovalling of the pipes are negligible in the frequency interval of interest. The results implies, for further dynamics studies, that the complete system could be idealised into a linear sub-system that is excited via the non-linear flexible joint, that the pipes could be modelled with beam elements and that the other components within the linear sub-system could also be modelled in a simplified way. Such simplified component models are suggested. The agreement between theoretical and experimental results is very good, which indicates the validity of the simplified modelling.

  • 8.
    Jaghbeer, Yasmeen
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Strategic Sustainable Development.
    Hallstedt, Sophie
    Blekinge Institute of Technology, Faculty of Engineering, Department of Strategic Sustainable Development.
    Larsson, Tobias
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Wall, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Exploration of Simulation-Driven Support Tools for Sustainable Product Development2017In: Procedia CIRP / [ed] Tim C. McAloone, Daniela C.A. Pigosso, Niels Henrik Mortensen and Yoshiki Shimomura, Elsevier, 2017, Vol. 64, p. 271-276Conference paper (Refereed)
    Abstract [en]

    Global society is encountering many challenges such as climate change, resource depletion, etc., which comes with a set of challenges and opportunities for businesses. Applied research in operational tools and methods that support sustainable product- and service systems innovation, aims to strengthen businesses to overcome these challenges. In recent years, several tools and methods have been developed in the sustainable product development field with focus on modelling and digitalization. This paper explores how sustainability has been integrated in modelling and simulation, and presents results from a literature review with the purpose of highlighting opportunities and challenges in the field. Furthermore, an initial model-based engineering support toolbox (MBE) is presented, with focus on support tools for socio-ecological sustainability integration in the early product development stages.

  • 9. Jönsson, Anders
    et al.
    Wall, Johan
    Broman, Göran
    A Virtual Machine Concept for Real-Time Simulation of Machine Tool Dynamics2005In: International journal of machine tools & manufacture, ISSN 0890-6955, E-ISSN 1879-2170, Vol. 45, no 7, p. 795-801Article in journal (Refereed)
    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.

  • 10.
    Massimo, Panarotto
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Wall, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Larsson, Tobias
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Simulation-driven design for assessing strategic decisions in the conceptual design of circular PSS business models2017In: Procedia CIRP: The 9th CIRP IPSS Conference: Circular Perspectives on Product/Service-Systems, Elsevier, 2017, Vol. 64, p. 25-30Conference paper (Refereed)
    Abstract [en]

    Due to ever increasing challenges faced by our global society, circular design and the idea of product-service systems (PSS) isgaining traction within businesses. However, ‘predicting’ the value of a future PSS solution in the early design phases is difficult,since it requires the ability to balance long term potential with short term decisions. Modelling and simulation is believed to beable to support this challenging task. A simulation framework for circular design of PSS is presented. The simulation processenables the comparison between functional and non-functional performances and their life cycle contributions depending on adefined PSS-like business model strategy. Such integrated simulation framework is intended to exploit engineering modelsoutside their specific discipline, enabling cross-functional collaboration and help decision makers understand how a design cancontribute in satisfying customer and stakeholders needs during the lifecycle of a PSS.

  • 11.
    Pilthammar, Johan
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Wall, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Sigvant, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Framework for Simulation-Driven Design of Stamping Dies Considering Elastic Die and Press Deformations2017In: PROCEEDINGS OF THE 20TH INTERNATIONAL ESAFORM CONFERENCE ON MATERIAL FORMING (ESAFORM 2017) / [ed] Brabazon D.,Ul Ahad I.,Naher S., American Institute of Physics (AIP), 2017, Vol. 1896, article id 010001Conference paper (Refereed)
    Abstract [en]

    Sheet metal forming (SMF) simulations are used extensively throughout the development phase of industrialstamping dies. In these SMF simulations, the die and press are normally considered as rigid. Previous research has howevershown that elastic deformation in these parts has a significant negative impact on process performance. This paperdemonstrates methods for counteracting these negative effects, with a high potential for improved production support anda reduced lead time through a shorter try-out process. A structural finite element model (FE-model) of a simplified die isstudied. To account for elastic deformation, the blankholder surfaces are first virtually reworked by adjusting the nodalpositions on the die surfaces attaining a pressure distribution in accordance to the design phase SMF simulations with rigidsurfaces. The elastic FE-model with reworked surfaces then represents a stamping die in running production. The die isnow assumed to be exposed to changed process conditions giving an undesired blankholder pressure distribution. Thechanged process conditions could for example be due to a change of press line. An optimization routine is applied tocompensate the negative effects of the new process conditions. The optimization routine uses the contact forces acting onthe shims of the spacer blocks and cushion pins as optimization variables. A flexible simulation environment usingMATLAB and ABAQUS is used. ABAQUS is executed from MATLAB and the results are automatically read back intoMATLAB. The suggested optimization procedure reaches a pressure distribution very similar to the initial distributionassumed to be the optimum, and thereby verifying the method. Further research is needed for a method to transform thecalculated forces in the optimization routine back to shims thicknesses. Furthermore, the optimization time is relativelylong and needs to be reduced in the future for the method to reach its full potential.

  • 12.
    Tatipala, Sravan
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Pilthammar, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering. Volvo Cars.
    Sigvant, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering. Volvo Cars.
    Wall, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Johansson, Christian
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Introductory study of sheet metal forming simulations to evaluate process robustness2018In: IOP Conference Series: Materials Science and Engineering, Institute of Physics Publishing (IOPP), 2018, Vol. 418, article id 012111Conference paper (Refereed)
    Abstract [en]

    The ability to control quality of a part is gaining increased importance with desires to achieve zero-defect manufacturing. Two significant factors affecting process robustness in production of deep drawn automotive parts are variations in material properties of the blanks and the tribology conditions of the process. It is imperative to understand how these factors influence the forming process in order to control the quality of a formed part. This paper presents a preliminary investigation on the front door inner of a Volvo XC90 using a simulation-based approach. The simulations investigate how variation of material and lubrication properties affect the numerical predictions of part quality. To create a realistic lubrication profile in simulations, data of pre-lube lubrication amount, which is measured from the blanking line, is used. Friction models with localized friction conditions are created using TriboForm and is incorporated into the simulations. Finally, the Autoform-Sigmaplus software module is used to create and vary parameters related to material and lubrication properties within a user defined range. On comparing and analysing the numerical investigation results, it is observed that a correlation between the lubrication profile and the predicted part quality exists. However, variation in material properties seems to have a low influence on the predicted part quality. The paper concludes by discussing the relevance of such investigations for improved part quality and proposing suggestions for future work.

  • 13. Wall, Johan
    Dynamics Study of an Automobile Exhaust System2003Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Low vibration levels are a critical objective in automobile exhaust system design. It is therefore important for design engineers to be able to predict, describe and assess the dynamics of various system design proposals during product development. The aim of this thesis is to provide a deeper understanding of the dynamics of automobile exhaust systems to form a basis for improved design and the development of a computationally inexpensive theoretical system model. Modelling, simulation and experimental investigation of a typical exhaust system are performed to gain such an understanding and to evaluate modelling ideas. Special attention is given to the influence of the bellows-type flexible joint on the dynamics of the exhaust system. The investigations show that the exhaust system is essentially linear downstream of the flexible joint. Highly simplified finite element models of the major components within this part are suggested. These models incorporate adjustable flexibility in their connection to the exhaust pipes and a procedure is developed for automatic updating of these parameters to obtain better correlation with experimental results. The agreement between the simulation results of the updated models and the experimental results is very good, which confirms the usability of these models. Furthermore, the investigations show the great reduction of vibration transmission to the exhaust system that the bellows-type joint, either with or without an inside liner, gives in comparison with a stiff joint. For the combined bellows and liner joint, vibration transmission is, however, higher than for the bellows alone. Inclusion of the liner also makes the exhaust system behaviour significantly non-linear and complex, whereas the system behaviour proves to be essentially linear when the joint has no liner. This shows the importance of including a model of the liner in the theoretical system model when the liner is present in the real system. The choice of whether or not to include a liner in the real system is obviously a complex issue. The advantages of reduced bellows temperature and improved flow conditions should be weighed against the disadvantages found in this work. By combining the above findings it is concluded that in coming studies of how engine vibrations affect the exhaust system, the latter may be considered as a linear system if the flexible joint consists of a bellows. If the joint also includes a liner, the system may be considered as a linear subsystem that is excited via a non-linear joint.

  • 14. Wall, Johan
    Simulation-Driven Design of Complex Mechanical and Mechatronic Systems2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Effective and efficient product development is critical to business success on the increasingly competitive global market, and simulation has proven to support this in many sectors. The aim of this thesis is to study how properties of complex mechanical and mechatronic systems can be more efficiently and systematically predicted, described, assessed and improved in product development. The purpose is to elaborate an approach that can, rather than only verifying solutions that are already decided upon, support dialogues with customers, stimulate creation of new concepts and provide guidance towards more optimised designs, especially in early development stages. This is here termed simulation-driven design. To be useful for this, product models and simulation and optimisation procedures must be efficient, that is, they must accurately answer posed questions and point towards better solutions while consuming an acceptable amount of time and other resources. In this thesis a coordinated approach to create such efficient decision support is elaborated. This is done by action research through two industrial case studies; an automobile exhaust system representing a complex mechanical system and a water jet cutting machine representing a mechatronic system. The general knowledge gained from these case studies should be a good base for coming implementation of this approach as an inherent working routine in companies developing complex mechanical and mechatronic products. A specific result is a validated virtual model of the exhaust system, which facilitates fast structural dynamics simulation of customer proposed design layouts. It is also shown that the non-linear flexible joint between the manifold and the rest of the exhaust system makes the system behaviour complex. This has resulted in an additional general research question, namely how systems that are linear, except for small but significant non-linear parts, can be simulated in an efficient way. Another specific result is a validated real-time virtual machine concept for simulation of the water jet cutting machine, which facilitates early-stage design optimisation. As the mechanics and the control system are considered simultaneously, interaction effects can be utilised. An introductory optimisation study shows a significant potential for improved manufacturing accuracy and a more light-weight design. This potential would not likely have been found through a conventional sequential design approach. The results of this thesis indicate that there is a great potential for improved product development performance in small and medium-sized companies. By incorporating modern simulation support these companies can improve their competitiveness as well as contribute to improved resource efficiency of society at large. In doing so, it is important to find a good balance between model fidelity, validity and cost for achieving a relevant decision support. The coordinated approach to simulation-driven design elaborated in this thesis is a promising and systematic way of finding this balance.

  • 15.
    Wall, Johan
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Bertoni, Marco
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Larsson, Tobias
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    A model-driven decision arena: Augmenting decision making in early design2018In: Proceedings of NordDesign: Design in the Era of Digitalization, NordDesign 2018, The Design Society, 2018, Vol. Code 141730Conference paper (Refereed)
    Abstract [en]

    A wide variety of expert competencies, transcending traditional disciplines, are needed to foresee and evaluate the impact of decisions in the conceptual phase of engineering design. Where this previously was a trade-off regarding design and development of the pure physical artefact it is now a complex ambiguity game involving all disciplines touching a solution during its lifecycle, due to the movement towards integrated product-service solutions. Gathering the involved, normally diverse, group of stakeholders in a collaborative setting for design exploration exercises, sharing knowledge and values, is believed to augment decision making ability in early design. A model-driven environment for collaborative decision making is proposed as a solution that potentially may help harvesting these benefits. In this environment stakeholders interact with each other using digital models, model generated information, simulation data and product data collected in the field in order to evaluate design proposals by playing out potential usage scenarios and investigating cause and effect relationships. Initial work on conceptualizing, developing, and testing such an environment is done through a pilot study based on two industrial use cases. The development process iteratively unveils demands and constraints related to the environment. These discoveries go hand in hand with developing an infrastructure regarding both hardware and software as well as required human resources in a functional environment. Fully realizing the envisioned model-driven environment for collaborative decision making entails new ways of working requiring new knowledge as well as technological innovation. In that aspect, environment infrastructure and usage are elaborated on and direction for further research and development is indicated.

  • 16. Wall, Johan
    et al.
    Englund, Thomas
    Ahlin, Kjell
    Broman, Göran
    Influence of a bellows-type flexible joint on exhaust system dynamics2004In: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991, Vol. 218, no 12, p. 1473-1478Article in journal (Refereed)
    Abstract [en]

    Most modern cars have a bellows-type flexible joint between the manifold and the catalytic converter to allow for thermal expansion and to decouple large engine movements and vibrations from the rest of the exhaust system. To obtain better understanding of the influence of this joint, the dynamic response of a typical exhaust system is studied when excited via different joint configurations. Measurements show the great order of reduction of vibration transmission to the exhaust system that a bellows joint, with and without an inside liner, gives in comparison with a stiff joint. For the combined bellows and liner joint vibration transmission is however higher than for the bellows alone. Together with some other aspects this makes the choice of including a liner in the exhaust system application complex. For a system in general the possibility of tuning the friction limit of the liner, to minimise overall vibrations through friction based damping, depends on how close to ideal the excitation source is and its location. Anyhow, the combined bellows and liner joint makes the exhaust system behaviour significantly non-linear, whereas the system behaviour proves to be essentially linear when the bellows has no liner, which imply that the liner needs to be included in theoretical models when present in the real system.

  • 17. Wall, Johan
    et al.
    Englund, Thomas
    Ahlin, Kjell
    Broman, Göran
    Modelling of multi-ply bellows flexible joints of variable mean radius2003Conference paper (Refereed)
    Abstract [en]

    Bellows flexible joints are included in automobile exhaust systems to allow for engine movements and thermal expansion and to reduce vibration transmission. Generally the joint consists of a flexible bellows, an inside liner and an outside braid. In this work the bellows is considered. A straightforward way to model the bellows is to use shell finite elements. Due to the convoluted geometry of the bellows that procedure requires however a high number of elements, meaning that the bellows model would constitute a large part of the model of the exhaust system. For more effective dynamics simulations a beam finite element representation of the bellows has been presented in a prior work. This modelling procedure was implemented in the commercial software I-DEAS and was verified against experimental results available in the literature for single-ply bellows of constant mean radius. This paper suggests adjustments by which this procedure can be extended to model also multi-ply bellows of variable mean radius. Experimental investigations of a double-ply bellows having decreasing mean radius towards its ends are included for verification. The agreement between theoretical and experimental results is very good, implying that the suggested extension of the modelling procedure is valid. It is also shown that the procedure can easily be implemented into other commercial software (in this case ABAQUS). The experimental investigation reveals an intriguing resonance frequency shift at small excitation force levels. Although considered to be of minor significance for the present application of the bellows, a hypothetic qualitative explanation to the observed phenomenon is given.

  • 18. Wall, Johan
    et al.
    Englund, Thomas
    Berghuvud, Ansel
    Identification and Modelling of Structural Dynamics Characteristics of a Water Jet Cutting Machine2004Conference paper (Refereed)
    Abstract [en]

    Dynamic characteristics of a water jet cutting machine, to be used in a virtual machine implemented in an analysis tool for engineering design, are derived. Machine users need for more cost effective production put demands on faster cutting. Faster cutting results in higher dynamic loads. As a consequence, problems with unwanted vibrations that decrease cutting precision may occur. Prediction of such potential problems is facilitated by an analysis tool for evaluation of suggested design solutions early in the product development process. The present work contributes to ongoing development of such an analysis tool for design engineers. An iterative approach including both theoretical and experimental analysis is applied in order to derive a structural dynamics model of the studied machine. A complex dynamic behaviour of the machine is found. High correlation between results obtained from theoretical and experimental modal analysis implies that the developed model can be used with confidence in future studies of the machine’s total system behaviour.

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