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  • 1.
    Barlo, Alexander
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Sigvant, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Islam, Md. Shafiqul
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Perez, Ll
    RISE, Sweden.
    Olofsson, E.
    Volvo Cars, Gothenburg, Sweden..
    Al-Fadhli, M.
    Volvo Cars, Olofstrom, Sweden..
    Tuan Pham, Quoc
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Odenberger, E-L
    RISE, Sweden.
    Proposal of a New Tool for Pre-Straining Operations of Sheet Metals and an Initial Investigation of CR4 Mild Steel Formability2023Ingår i: 42ND CONFERENCE OF THE INTERNATIONAL DEEP DRAWING RESEARCH GROUP / [ed] Asnafi, N Lindgren, LE, IOP PUBLISHING LTD , 2023, Vol. 1284, artikel-id 012079Konferensbidrag (Refereegranskat)
    Abstract [en]

    With the increased focus on reducing carbon emissions in the automotive industry, more advanced materials are introduced to reduce the vehicle weight, and more complex component geometries are designed to both satisfy customer demands and to optimize the vehicle aerodynamically. With the increase in component complexity, the strain paths produced during the forming operation of car body components often display a highly non-linear behavior which makes the task of failure prediction during the manufacturing feasibility studies more difficult. Therefore, CAE engineers need better capabilities to predict failure induced by strain path nonlinearity. This study proposes a new tool designed for creating bi-linear strain paths, by performing a pre-strain of a sheet large enough to cut out Nakajima specimens to perform the post-straining in any direction. From five pre-straining tests the tool present a stable pre-straining operation with a uniform strain field in a radius of 100 [mm] from the centre, corresponding to the region of interest of a Nakajima specimen. From the five pre-strained samples, different Nakajima specimens are cut transverse and longitudinal to the rolling direction and a failure prediction approach in an alternative, path independent evaluation space was used to predict the onset of necking with promising results.

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  • 2.
    Barlo, Alexander
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Sigvant, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Kesti, V.
    SSAB Europe Oy, Finland..
    Islam, Md. Shafiqul
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Tuan Pham, Quoc
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Determination of Edge Fracture Limit Strain for AHSS in the ISO-16630 Hole Expansion Test2023Ingår i: 42ND CONFERENCE OF THE INTERNATIONAL DEEP DRAWING RESEARCH GROUP / [ed] Asnafi, N Lindgren, LE, IOP PUBLISHING LTD , 2023, Vol. 1284, artikel-id 012027Konferensbidrag (Refereegranskat)
    Abstract [en]

    With the increased demand for application of sustainable materials and lightweight structures, the sheet metal forming industry is forced to push existing materials to the limits. One area where this is particular difficult is when it comes to assessing the formability limit for sheet edges. For decades, the ISO-16630 Hole Expansion Test (HET) has been the industry standard for expressing the edge formability of sheet metals through the Hole Expansion Ratio (HER). However, in recent years, this test has been criticized for its high scatter in results for repeated experiments. This scatter has been suspected to be caused by the operator-reliant post-processing of the test, or variations in the cutting conditions for the different test specimens. This study investigates the impact of shifting the evaluation point of the test from the through-thickness crack to the onset of surface failure on the reported scatter, as well as performs inverse modeling of the Hole Expansion Test to obtain an edge limit strain value.

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  • 3.
    Barlo, Alexander
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Sigvant, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Manopulo, Niko
    AutoForm Development GmbH, CHE.
    Islam, Md. Shafiqul
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Failure Prediction of Automotive Components Utilizing a Path Independent Forming Limit Criterion2022Ingår i: Key Engineering Materials / [ed] Vincze G., Barlat F., Trans Tech Publications Inc., 2022, s. 906-916Konferensbidrag (Refereegranskat)
    Abstract [en]

    An area in the automotive industry that receives a lot of attention today is the introduction of lighter and more advanced material grades in order to reduce carbon emissions, both during production and through reduced fuel consumption. As the complexity of the introduced materials and component geometries increases, so does the need for more complex failure prediction approaches. A proposed path-independent failure criterion, based on a transformation of the limit curve into an alternative evaluation space, is investigated. Initially, the yield criterion used for this transformation of the limit curve was investigated. Here it was determined that the criterion for the transformation could not be decoupled from the material model used for the simulation. Subsequently, the approach using the transformed limit curve was tested on an industrial case from Volvo Cars, but a successful failure prediction was not obtained. © 2022 The Author(s). Published by Trans Tech Publications Ltd, Switzerland.

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  • 4.
    Barlo, Alexander
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Sigvant, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Perez, L.
    RISE IVF AB.
    Islam, Md. Shafiqul
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    A Study of the Boundary Conditions in the ISO-16630 Hole Expansion Test2022Ingår i: INTERNATIONAL DEEP-DRAWING RESEARCH GROUP CONFERENCE (IDDRG 2022) / [ed] Thuillier, S Grolleau, V Laurent, H, Institute of Physics (IOP), 2022, Vol. 1238Konferensbidrag (Refereegranskat)
    Abstract [en]

    As new and more advanced sheet metal materials are introduced to the market, more accurate techniques for determination of failure limits are needed. One area that needs attention is edge formability, where the ISO-16630 standardized Hole Expansion Test currently is used to express this through the Hole Expansion Ratio. Over the years, this standard has been criticized for producing a large scatter in repeated tests. This paper investigates a new setup for the Hole Expansion Test which introduces draw beads into the setup to ensure sufficient restraining of the specimen during the test in an effort to reduced the scatter. In total 62 tests of a DP800 steel alloy were executed, but a large scatter in the results were still seen. It was therefore concluded that a lack of restraining force in the Hole Expansion Test was not the primary cause of the reported scatter seen in other tests.

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  • 5.
    Chezan, A. R.
    et al.
    Tata Steel R&D, Netherlands..
    Atzema, E. H.
    Tata Steel R&D, Netherlands.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Sigvant, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Material variability effects on automotive part production process2023Ingår i: 42ND CONFERENCE OF THE INTERNATIONAL DEEP DRAWING RESEARCH GROUP / [ed] Asnafi, N Lindgren, LE, IOP PUBLISHING LTD , 2023, Vol. 1284, artikel-id 012037Konferensbidrag (Refereegranskat)
    Abstract [en]

    The current efforts to reduce the carbon footprint throughout the chain in the automotive industry by increased use of recycled materials poses new challenges for materials production and their use. The increase of steel scrap fraction in the current primary steel making processes, used for producing steel sheet metal for automotive components, possibly affects the material properties variability beyond the limits observed in the materials produced today despite mitigating actions in steel production. In this paper material variability increase was modelled by selecting deterministic values outside the range of the material grade used to design and manufacture an automotive part. The values were selected from an experimental data set representing the cold rolled mild steels material class range. The effects were studied numerically on a reverse engineered model of an existing automotive part production process. It was found that the manufacturing feasibility in this particular case is mainly affected by the weighted average plastic strain ratio and less by the degree of planar anisotropy.

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  • 6.
    Manopulo, N.
    et al.
    AutoForm Dev GmbH, CHE.
    Chezan, A. R.
    Tata Steel, NLD.
    Atzema, E.
    Tata Steel, NLD.
    Anfruns, I. Picas
    Tata Steel, NLD.
    Carleer, B.
    AutoForm Engn Deutschland GmbH, DEU.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Sigvant, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    On the mechanics of edge cracking and the reliable determination of edge formability limits2021Ingår i: INTERNATIONAL DEEP-DRAWING RESEARCH GROUP CONFERENCE (IDDRG 2021) / [ed] Liewald, M, Karadogan, C, IOP PUBLISHING LTD , 2021, Vol. 1157, artikel-id 012055Konferensbidrag (Refereegranskat)
    Abstract [en]

    Blanked edge surfaces are rough and hardened. They therefore lead to inhomogeneous deformation on the edge, which can trigger localization within the shear affected zone (up to few mm from the edge). The size and extent of these phenomena are primarily a function of the shearing process and are only marginally coupled to the global/homogeneous deformation behavior of the blank A direct numerical simulation of such local deformation effects would require a prohibitively high resolution to capture the microgeometry of the edge and thus remains unfeasible in the current industrial practice. A predictive model can therefore only be achieved by determining limit strains on the edge, which are compatible with the homogeneous numerical framework used. The present contribution aims discussing the basic mechanics of edge cracking based on tensile tests with edges blanked with different die clearances. The local and global strain evolutions in the vicinity of the edge are analysed and a new evaluation procedure is proposed for the reliable determination of limit strains. The application of this method in industrial context is also discussed.

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  • 7.
    Ottosson, P.
    et al.
    RISE AB, Div Mat & Prod, Sweden.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik. Volvo Cars, Sweden.
    Wiklund, D.
    RISE AB, Div Mat & Prod, Sweden.
    Skare, T.
    RISE AB, Div Mat & Prod, Vallaregatan 30, SE-29338 Olofstrom, Sweden..
    Sigvant, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Substitutive models of press deflections for efficient numerical die cambering2023Ingår i: 42ND CONFERENCE OF THE INTERNATIONAL DEEP DRAWING RESEARCH GROUP / [ed] Asnafi, N Lindgren, LE, IOP PUBLISHING LTD , 2023, Vol. 1284, artikel-id 012060Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cost and time for stamping die tryouts are significant within the car industry. A major contributing factor is that elastic deflections of stamping dies and presses are usually not considered during the virtual die design and forming simulation phase. Active surfaces of stamping dies are only cambered based on previous experiences of tool types and stamping presses. However, almost all stamping dies and presses are unique, and available experiences are not valid for new sheet materials. This leads to component deviations and often several loops of tool adjustments are needed. Previously partners within the SMART Advanced Manufacturing research project CAMBER have developed advanced deflection measuring devices to quantify the elastic deformations of stamping presses. Using these measurements, cambering methodologies can be utilized in sheet metal forming simulations. In this paper numerical substitutive stamping press models are described which are capable of compensating for measured stamping press dynamics. The result show that a numerical compensated tool can improve the contact by over 80% compared to the corresponding contact without compensation.

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  • 8.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik. Volvo Cars.
    Towards Virtual Tryout and Digital Twins: Enhanced Modeling of Elastic Dies, Sheet Materials, and Friction in Sheet Metal Forming2020Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Konkurrens och komplexitet ökar ständigt inom den globala bilmarknaden. För att skapa konkurrensfördelar behöver företag som verkar på marknaden fokusera på teknikutveckling, vilket i sin tur ökar produkternas värde för konsumenterna. Samtidigt som man utvecklar det tekniska innehållet i sina produkter så är det lika viktigt att utveckla sina tillverkningsprocesser. Välutvecklade tillverkningsprocesser möjliggör produktion av tekniskt avancerade, och attraktiva produkter, till en konkurrenskraftig kostnad.

    En viktig process, som denna avhandling fokuserar på, är pressning av plåt. Plåtformningsprocessen simuleras sedan ett par decennium tillbaka med Finita Element (FE) simuleringar. Man kan på så sätt prediktera form, töjningar, tjocklek, återfjädring, rynkor, risk för försträckning och sprickor m.m. En faktor som för tillfället inte inkluderas i näst intill alla plåtformningssimuleringar är elastiska press- och verktygsdeformationer. Detta begränsar möjligheterna att använda plåtformningssimulering för virtuell inprovning och att skapa pålitliga digitala tvillingar. Elastiska deformationer hanteras istället manuellt under, den oftast långa och dyra, inprovningsfasen.

    Detta projekt visar på vikten av att inkludera press- och verktygsdeformationer genom simuleringar av verkliga pressverktyg. I de simulerade fallen är det inte möjligt att uppnå bra resultat för inprovning och produktionssupport utan att inkludera verktygsdeformationer i modellen.

    CAD-modeller finns för nästan alla pressverktyg idag. Strategier för att inkludera elastiska verktygsgeometrier i simuleringar presenteras. Modellerna är enkla att skapa och snabba att lösa. Kompletta CAD-modeller av pressar är inte lika vanligt. Metoder för att mäta upp pressar och inkludera i simuleringar är därför också presenterade, tillsammans med exempel på andra metoder från vetenskaplig litteratur. En standardiserad metod för plåtformningsindustrin är av intresse.

    Simuleringar med elastiska verktyg ger endast pålitliga resultat om plåt och friktion representeras på ett bra sätt. Speciellt friktion är starkt beroende av verktygsdeformationer då kontakttryck är en viktig faktor i friktionsmodeller. Material- och friktionsmodeller vilar på väl fungerande metoder för karaktärisering utifrån god experimentell data.

    Plåtformningssimuleringar med elastiska verktyg, tillsammans med pålitliga modeller av plåtmaterial och friktionssystem, har en stor potential att reducera ledtiden för pressverktyg. Dessa metoder kommer också att vara viktiga i skapandet av digitala tvillingar av verktyg och pressar.

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  • 9.
    Pilthammar, Johan
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Allesson, Sara
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik. (student).
    Lind, Markus
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik. (student).
    Schill, Mikael
    Dynamore Nordic.
    Sigvant, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Sjöblom, Viktor
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik. (student).
    A Complete and Rapid Simulation Method for Virtual Try-out of Stamping Dies Considering Elastic DeformationsManuskript (preprint) (Övrigt vetenskapligt)
  • 10.
    Pilthammar, Johan
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik. Volvo Cars.
    Andreasson, Eskil
    Tetra Pak.
    Surpassing Threshold Concepts within Engineering Mechanics Interactive Computer Aided Learning (CAL) to support the learning process2022Ingår i: Högskolepedagogisk debatt, ISSN 2000-9216, nr 2, s. 77-98Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    This paper is based on a scientific literature review and interviews with teachers and researchers active in the area of Engineering Mechanics in Swedish higher education. The paper aims to identify and highlight troublesome knowledge and threshold concepts within the field of Engineering Mechanics. Moreover, the ambition is to present ideas of how to overcome these identified threshold concepts. Recent scientific research acknowledges many benefits of introducingdigital and interactive tools, denominated Computer Aided Learning (CAL), at an early stage. Digital and interactive tools can help engineering students overcome threshold concepts. A selection of these digital tools is discussed in this paper. The study concludes that elearning is an efficient way to enhance and complement the learning process. It also makes teaching material available from anywhere, at any time. Hence, students can individually adjust their learning pace. The interviews with teachers contributed to a clearer view of how dig-ital tools can be utilized and transform learning in mechanical engineering.Master students in mechanical engineering are expected to create, operate, and understand advanced digital tools. However, on the B.Sc. level, the implementation of digital tools seems to be scarce. Instead, textbooks, exercises with pen and paper, and traditional teaching are the preferred tools for learning. Implementing digital and interactive computer tools already on a basic teaching level (B.Sc.) can assist students to understand complex theories and overcome threshold concepts.

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  • 11.
    Pilthammar, Johan
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik. Volvo Cars, Department 81110 Strategy & Concept, SWE.
    Banabic, Dorel
    Tech Univ Cluj Napoca, ROU.
    Sigvant, Mats
    Volvo Cars, Department 81110 Strategy & Concept, SWE.
    BBC05 with non-integer exponent and ambiguities in Nakajima yield surface calibration2021Ingår i: International Journal of Material Forming, ISSN 1960-6206, E-ISSN 1960-6214, Vol. 14, nr 4, s. 577-592Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reliable sheet metal forming simulations depend on accurate descriptions of real process conditions. These conditions include material behavior, lubrication systems, tool deformations, press dynamics, and more. Research on material models is the most mature area for describing these conditions in a reliable way. Several advanced and flexible models exists. This study focuses on two versions of yield criteria for sheet materials that are assumed to follow the plane stress assumption: the BBC05 model with integer exponent and the BBC05 model with non-integer exponent. The literature has previously described the BBC05 model with integer exponent. This paper elaborates on a modified version with non-integer exponent that offers more flexibility in the mathematical description. Furthermore, it outlines the implementation of this material model and similar yield criteria as user subroutines in finite element software. As mathematical flexibility increases, it enables more physically correct material approximations. However, it also becomes more challenging to calibrate because of ambiguities due to a larger number of mathematical variables. These ambiguities is demonstrated by using a Nakajima test without lubrication during inverse modeling of parameters for the BBC05 model. It shows that it is impossible to accurately identify the physically correct combination of friction coefficient and the yield surface exponent, k, using strain distributions and punch force. It is suggested to use two Nakajima tests in the inverse modeling process where friction can be neglected due to testing conforming to ISO12004-2. One test that corresponds to equi-biaxial strain of the sheet, and one that corresponds to plane strain in the transverse direction of the sheet. By utilizing these samples in the inverse modeling it is possible to separate friction from the exponent k. A non-integer value of k is found to yield the most reliable prediction of strains and forces in the simulations, thereby also demonstrating the need of flexible yield surface models such as BBC05 with non-integer exponent, YLD2000, Vegter and more advanced yield criteria.

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  • 12.
    Pilthammar, Johan
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik. Volvo Cars, SWE.
    Schill, Mikael
    Dynamore Nordic.
    Sigvant, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik. Volvo Cars, SWE.
    Sjöblom, Viktor
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik. (Student).
    Lind, Markus
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik. (Student).
    Simulation of Sheet Metal Forming using Elastic Stamping Dies2019Ingår i: Proc. of the 12th European LS-DYNA Conference 2019, 2019, 2019Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Simulation of sheet metal forming is one of the major applications of LS-DYNA. Today, a majority of the forming industry is using Finite Element models to design the stamping dies in order to prevent excessive thinning, wrinkling and producing parts within tolerance by compensating for springback deformation. All these simulations are made using the assumption of rigid forming surfaces. Depending on the type of press, tool design and sheet metal part, this assumption could prove to be incorrect which yields a forming result that depends on the elastic deformation of the stamping die and in some cases the entire stamping press. Such deformations are usually compensated during die try-out by manual rework which is costly and time consuming.

    This paper presents the result of a study performed at Volvo Cars press shop in Olofström, Sweden, aiming at determining computational methods to introduce elastic stamping dies in the sheet metal forming simulations in order to minimize manual rework by performing a virtual tryout of the stamping die. The methodology to model the stamping die and the forming surfaces in LS-DYNA are presented and a simulation model is gradually improved from using nominal rigid CAD surfaces through scanned tool surfaces and finishing with an elastic model of the stamping die assembly. The part used in the study is the side door inner for Volvo XC90 and comparisons are continuously made between simulations results and measurements on parts from running production.

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    Simulation of Sheet Metal Forming using Elastic Stamping Dies
  • 13.
    Pilthammar, Johan
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Sigvant, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Islam, Md. Shafiqul
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Schill, M.
    Dynamore Nord, Sweden.
    Sjoblom, S.
    Blekinge Tekniska Högskola. student.
    Sjoblom, V.
    Blekinge Tekniska Högskola. student.
    Lind, M.
    Blekinge Tekniska Högskola. student.
    An overview of Methods for Simulating Sheet Metal Forming with Elastic Dies2023Ingår i: 42ND CONFERENCE OF THE INTERNATIONAL DEEP DRAWING RESEARCH GROUP / [ed] Asnafi, N Lindgren, LE, IOP PUBLISHING LTD , 2023, Vol. 1284, artikel-id 012054Konferensbidrag (Refereegranskat)
    Abstract [en]

    Sheet metal forming (SMF) simulations are traditionally carried out with rigid active forming surfaces. This means that the elasticity and dynamics of presses and die structures are ignored. The only geometries of the tools included in the simulations are the active forming surfaces. One reason for this simplification is the large amount of computational power that is required to solve finite element (FE) models that incorporates elastic stamping dies. Another reason is the lack of die CAD models before the later stages of stamping projects. Research during the last couple of decades indicated potential large benefits when including elastic dies in SMF simulations. For example, for simulating die try-out or for Digital Twins of presses and dies. Even though the need and potential benefits of elastic dies in simulations are well known it is not yet implemented on a wide scale. The main obstacles have been lacking data on presses and dies, long simulation times, and no standardized implementation in SMF software. This paper presents an overview of existing methods for SMF simulations with elastic dies and discuss their respective benefits and drawbacks. The survey of methods shows that simulation models with elastic tools will be needed for detailed analyses of forming operations and also for purposes like digital twins. On the other hand, simplified and robust models can be developed for non-FEA users to carry out simple one-step compensation of tool surfaces for virtual spotting purposes. The most promising and versatile method from the literature is selected, modified, and demonstrated for industrial sized dies.

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  • 14.
    Pilthammar, Johan
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Sigvant, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Islam, Md. Shafiqul
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Schill, M.
    Dynamore Nord, Sweden..
    Sjoblom, S.
    Blekinge Tekniska Högskola. student.
    Sjoblom, V.
    Blekinge Tekniska Högskola. student.
    Lind, M.
    Blekinge Tekniska Högskola. student.
    Three Industrial Cases of Sheet Metal Forming Simulations with Elastic Dies2023Ingår i: 42ND CONFERENCE OF THE INTERNATIONAL DEEP DRAWING RESEARCH GROUP / [ed] Asnafi, N Lindgren, LE, IOP PUBLISHING LTD , 2023, Vol. 1284, artikel-id 012055Konferensbidrag (Refereegranskat)
    Abstract [en]

    Previous research and experience points to many advantages if sheet metal forming is simulated with elastic dies. Some areas that are enabled by simulations with elastic dies are virtual spotting, improved digital twins, and improved production support. A promising method was selected from the literature, and after important modifications it is deemed to be fast and robust for simulating industrial sized dies. The method consists of meshing die solids with a coarse mesh to represent the structural behaviour of the die. The forming surfaces are then represented by a fine shell mesh connected to the solid mesh by tied contacts with an offset. With additional modifications to reduce solver time this yields a robust and flexible way of modelling sheet metal forming with elastic dies. There is an increase in preprocessing and simulation time compared to using rigid tools, but industrial dies can now be modeled within an hour and solved within a working day. It is also easy to update the model by replacing separate parts such as die solids or forming surfaces. One of the main criteria in favor of the selected approach is the realistic modeling of blankholder and cushion systems. In this paper simulations of three industrial cases are demonstrated: one case of virtual die spotting and two cases of production support. The three cases demonstrate the importance and potential of using elastic dies during virtual die tryout, production support, and for cases like digital twins and production control.

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  • 15.
    Pilthammar, Johan
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Sigvant, Mats
    Volvo Cars, SWE.
    Kao-Walter, Sharon
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Including die and press deformations in sheet metal forming simulations2016Ingår i: NUMISHEET 2016: 10TH INTERNATIONAL CONFERENCE AND WORKSHOP ON NUMERICAL SIMULATION OF 3D SHEET METAL FORMING PROCESSES, PTS A AND B / [ed] Cardoso, RPR Yoon, JW Dick, RE Neto, ES DeSa, JMAC Adetoro, OB, IOP PUBLISHING LTD , 2016, artikel-id UNSP 032036Konferensbidrag (Refereegranskat)
    Abstract [en]

    Structural analysis, in Abaqus, of a stamping die and subsequent morphing of the tool surfaces in AutoForm were performed to improve a sheet metal forming simulation. First, the tool surfaces of the XC90 rear door inner were scanned. They were not matching when the die was unloaded and could therefore not give any satisfying results in sheet metal forming simulations. Scanned surface geometries were then added to a structural FE-model of the complete stamping die and some influential parts of the production press. The structural FE-model was analysed with Abaqus to obtain the structural deformations of the die. The calculated surface shapes were then transferred to AutoForm where a forming simulation was performed. Results from the different sheet metal forming simulations were compared to measured draw in curves and showed a substantial increase in accuracy and ability to analyse dies in running production when the morphed surfaces were used.

  • 16.
    Pilthammar, Johan
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Sigvant, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Kao-Walter, Sharon
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Introduction of elastic die deformations in sheet metal forming simulations2018Ingår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 151, nr S1, s. 76-90Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Simulations of sheet metal forming (SMF) with finite element models (FE-models) for stamped parts in the car industry are useful for detecting and solving forming problems. However, there are several issues that are challenging to analyze. Virtual tryout and analyzes of stamping dies in running production are two important cases where many of these challenging issues are present. Elastic deformations of dies and press lines and a physically based friction model is often missing when these types of cases are analyzed. To address this, this research aims to develop a method wherein the results of two separate FE-models are combined to enable SMF simulations with the inclusion of elastic tool and press deformations. The two FE-models are one SMF model with two-dimensional (2D) rigid tool surfaces and one structural model of the die and press. The structural model can predict surface shapes and pressure distributions for a loaded stamping die. It can also visualize relatively large and unexpected deformations of the die structure. The recommended method of transferring the deformations from the structural model to the 2D surfaces is through an FE technique called submodeling. The subsequent SMF simulations show that the method for calculating and using the deformed surfaces together with the TriboForm friction model yields a result that matches measured draw-in and strains. It is verified that the ability to virtually deform a die and include the resulting geometry in forming simulations is of high importance. It can be used for the virtual tryout and optimization of new dies or analyses of existing dies in running production. It is suggested that future research focus on a more efficient and automated workflow. More experimental data and simulations are also needed to verify the assumptions made for the simulation models. This will enable the method to be adopted in a reliable way for standard SMF simulations. © 2017.

  • 17.
    Pilthammar, Johan
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Skare, T.
    RISE IVF AB, Div Mat & Prod, SWE.
    Galdos, L.
    Mondragon Unibertsitatea ESP.
    Frojdh, K.
    Proximion AB, SWE.
    Ottosson, P.
    RISE IVF AB, Div Mat & Prod, SWE.
    Wiklund, D.
    RISE IVF AB, Div Mat & Prod, SWE.
    Carlholmer, J.
    RISE IVF AB, Div Mat & Prod, SWE.
    Sigvant, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Ohlsson, M.
    RISE IVF AB, Div Mat & Prod, SWE.
    Saenz de Argandona, E.
    Mondragon Unibertsitatea, ESP.
    Abbasi, F.
    Mondragon Unibertsitatea, ESP.
    Sarasua, O.
    Fagor Arrasate S Coop, ESP.
    Garro, A.
    Koniker S Coop, ESP.
    Rutgersson, W.
    Cascade Control AB, SWE.
    New press deflection measuring methods for the creation of substitutive models for efficient die cambering2021Ingår i: INTERNATIONAL DEEP-DRAWING RESEARCH GROUP CONFERENCE (IDDRG 2021) / [ed] Liewald, M, Karadogan, C, IOP PUBLISHING LTD , 2021, Vol. 1157, artikel-id 012076Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cost and time for die tryout are significant within the car industry, and elastic deflections of dies and presses are most commonly not considered during the virtual die design and forming simulation phase. Because of this, active surfaces of stamping dies are only cambered based on previous experiences of tool types and presses. However, almost all stamping dies and presses are unique, and available experiences are not valid for new materials. Partners within the Eureka SMART Advanced Manufacturing research project CAMBER have developed advanced deflection measuring devices to quantify the elastic deformations of presses. Using these measurements, cambering methodologies can be utilized in sheet metal forming simulations. Important breakthroughs in recent years enabling the cambering methodology consists of efficient simulation strategies for full scale simulations with elastic dies and optimization techniques for creating substitutive press structures based on measurements. Furthermore, modem press deflection measurement methods are beneficial in applications such as Industry 4.0, predictive maintenance, product quality control, etc. through a more advanced understanding and live monitoring of the press system.

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  • 18.
    Sigvant, M.
    et al.
    Volvo Cars, SWE.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Hol, J.
    TriboForm Engn, NLD.
    Wiebenga, J. H.
    TriboForm Engn, NLD.
    Chezan, T.
    Tata Steel, NLD.
    Carleer, B.
    AutoForm Engn, DEU.
    van den Boogaard, A. H.
    Univ Twente, NLD.
    Friction and lubrication modelling in sheet metal forming simulations of the Volvo XC90 inner door2016Ingår i: NUMISHEET 2016: 10TH INTERNATIONAL CONFERENCE AND WORKSHOP ON NUMERICAL SIMULATION OF 3D SHEET METAL FORMING PROCESSES, PTS A AND B / [ed] Cardoso, RPR Yoon, JW Dick, RE Neto, ES DeSa, JMAC Adetoro, OB, IOP PUBLISHING LTD , 2016, artikel-id UNSP 032090Konferensbidrag (Refereegranskat)
    Abstract [en]

    The quality of sheet metal formed parts is strongly dependent on the friction and lubrication conditions that are acting in the actual production process. Although friction is of key importance, it is currently not considered in detail in stamping simulations. This paper presents project results considering friction and lubrication modelling in stamping simulations of the Volvo XC90 inner door. For this purpose, the TriboForm software is used in combination with the AutoForm software. Validation of the simulation results is performed based on door-inner parts taken from the press line in a full-scale production run. The project results demonstrate the improved prediction accuracy of stamping simulations.

  • 19.
    Sigvant, Mats
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Falk, Johannes
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Experiments and FE-simulations of stretch flanging of DP-steels with different shear cut edge quality2017Ingår i: Journal of Physics: Conference Series / [ed] Volk W., Institute of Physics Publishing , 2017, Vol. 896, nr 1, artikel-id 012101Konferensbidrag (Refereegranskat)
    Abstract [en]

    Dual-Phase (DP) steels are today used in the automotive industry due to its large strength to weight ratio. However, the high strength of DP-steel does have a negative impact on the general formability in sheet metal forming. Unfavourable process conditions in the press shop will, on top of this, reduce the formability of DP-steels even more. This paper addresses the problem of edge fracture in stretch flanges in sheet metal parts made of DP-steel. The experimental part involves tests of ten different DP590 and DP780 steel grades with three different shear cut qualities. The influence on the fracture strain of the sample orientation of the shear cut are also studied by facing the burr away or towards the punch and testing samples with the cut edge parallel with the rolling direction and the transverse direction. The strains are measured with an ARAMIS system in each test, together with punch displacement and punch force. All tests are then simulated with AutoFormplus R7 and the results from these simulations are compared with the experimental results in order to find the appropriate failure strain for each combination of supplier, coating, thickness and shear cut quality. © Published under licence by IOP Publishing Ltd.

  • 20.
    Sigvant, Mats
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Hol, J.
    TriboForm Engineering, NLD.
    Wiebenga, J. H.
    TriboForm Engineering, NLD.
    Chezan, T.
    Tata Steel, NLD.
    Carleer, B.
    AutoForm Engineering, DEU.
    Van Den Boogaard, A. H.
    University of Twente, NLD.
    Friction in Sheet Metal Forming Simulations: Modelling of New Sheet Metal Coatings and Lubricants2018Ingår i: IOP Conference Series: Materials Science and Engineering, Institute of Physics Publishing , 2018, Vol. 418, nr 1, artikel-id 012093Konferensbidrag (Refereegranskat)
    Abstract [en]

    The quality of sheet metal formed parts is strongly dependent on the tribology and friction conditions that are acting in the actual forming process. These friction conditions are then dependent on the tribology system, i.e. the applied sheet material, coating and tooling material, the lubrication and process conditions. Although friction is of key importance, it is currently not considered in detail in sheet metal forming simulations. The current industrial standard is to use a constant (Coulomb) coefficient of friction, which limits the overall simulation accuracy. Since a few years back there is an ongoing collaboration on friction modelling between Volvo Cars, Tata Steel, TriboForm Engineering, AutoForm Engineering and the University of Twente. In previous papers by the authors, results from lab scale studies and studies of a door-inner part in Volvo Cars production have been presented. This paper focuses on the tribology conditions during early tryout of dies for new car models with an emphasis on the effect of the usage of new steel material coatings and lubricants on forming results. The motivation for the study is that the majority of the forming simulations at Volvo Cars are performed to secure the die tryout, i.e. solve as many problems as possible in forming simulations before the final design of the die and milling of the casting. In the current study, three closure parts for the new Volvo V60 model have been analysed with both Coulomb and TriboForm friction models. The simulation results from the different friction models are compared using thickness measurements of real parts, and 3D geometry scanning data of the parts. Results show the improved prediction accuracy of forming simulations when using the TriboForm friction model, demonstrating the ability to account for the effect of new sheet metal coatings and lubricants in sheet metal forming simulations. © Published under licence by IOP Publishing Ltd.

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  • 21.
    Sigvant, Mats
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Hol, J.
    TriboForm Engineering, NLD.
    Wiebenga, J. H.
    TriboForm Engineering, NLD.
    Chezan, Toni
    Tata Steel, NLD.
    Carleer, Bart
    AutoForm Engineering Deutschland GmbH, DEU.
    Van Den Boogaard, A. H.
    University of Twente, NLD.
    Friction in Sheet Metal Forming: Forming Simulations of Dies in Try-Out2018Ingår i: Journal of Physics: Conference Series, Institute of Physics Publishing , 2018, nr 1Konferensbidrag (Refereegranskat)
    Abstract [en]

    The quality of sheet metal formed parts is strongly dependent on the tribology and friction conditions that are acting in the actual forming process. This paper focuses on the tribology conditions during early try-out of dies for new car models. The motivation for the study is that the majority of the forming simulations at Volvo Cars are performed to secure the die try-out, i.e. solve as many problems as possible in forming simulations before the final design of the die and milling of the casting. In the current study, three closure parts for the new Volvo V60 model have been analysed with both Coulomb and TriboForm friction models. The simulation results from the different friction models are compared using thickness measurements of real parts, and 3D geometry scanning data of the parts. Results show the improved prediction capability of forming simulations when using the TriboForm friction model, demonstrating the ability to accurately describe try-out conditions in sheet metal forming simulations. © 2018 Institute of Physics Publishing. All rights reserved.

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  • 22.
    Sigvant, Mats
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Hol, Jeroen
    TriboForm Engineering, NLD.
    Wiebenga, J. H.
    TriboForm Engineering, NLD.
    Chezan, T.
    Tata Steel, NLD.
    Carleer, Bart
    AutoForm Engineering, DEU.
    Van Den Boogaard, A. H.
    University of Twente, NLD.
    Friction and lubrication modeling in sheet metal forming simulations of a Volvo XC90 inner door2016Ingår i: IOP Conference Series: Materials Science and Engineering, 2016, Vol. 159, nr 1, artikel-id 012021Konferensbidrag (Refereegranskat)
    Abstract [en]

    The quality of sheet metal formed parts is strongly dependent on the tribology, friction and lubrication conditions that are acting in the actual production process. Although friction is of key importance, it is currently not considered in detail in stamping simulations. This paper presents a selection of results considering friction and lubrication modeling in sheet metal forming simulations of the Volvo XC90 right rear door inner. For this purpose, the TriboForm software is used in combination with the AutoForm software. Validation of the simulation results is performed using door inner parts taken from the press line in a full-scale production run. The results demonstrate the improved prediction accuracy of stamping simulations by accounting for accurate friction and lubrication conditions, and the strong influence of friction conditions on both the part quality and the overall production stability. © Published under licence by IOP Publishing Ltd.

  • 23.
    Sigvant, Mats
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Hol, Johan
    TriboForm Engineering, NLD.
    Wiebenga, J. H.
    TriboForm Engineering, NLD.
    Chezan, Toni
    Tata Steel Europe Limited, GBR.
    Carleer, Bart
    AutoForm Engineering, DEU.
    van den Boogaard, Ton
    University of Twente, NLD.
    Friction in sheet metal forming: Influence of surface roughness and strain rate on sheet metal forming simulation results2019Ingår i: Procedia Manufacturing / [ed] Duflou, JR; Carette, Y; Fratini, L; Micari, F; Merklein, M; Hagenah, H, Elsevier B.V. , 2019, Vol. 29, s. 512-519Konferensbidrag (Refereegranskat)
    Abstract [en]

    The quality of sheet metal formed parts is strongly dependent on the tribology and friction conditions that are acting in the actual forming process. These friction conditions are then dependent on the tribology system, i.e. the applied sheet material, coating and tooling material, the lubrication and process conditions. Although friction is of key importance, it is currently not considered in detail in sheet metal forming simulations. The current industrial standard is to use a constant (Coulomb) coefficient of friction, which limits the overall simulation accuracy. Since a few years, back there is an ongoing collaboration on friction modelling between Volvo Cars, Tata Steel, TriboForm Engineering, AutoForm Engineering and the University of Twente. In previous papers by the authors, results from lab scale studies and studies of body parts at Volvo Cars, both parts in early tryout for new car models as well as parts in production have been presented. However, the introduction of a new friction model in the sheet metal forming simulations forces the user to gain knowledge about accurate values for new input parameters and question current modeling assumptions. This paper presents results from studies on the influence on the sheet metal forming simulation results from stamping die surface roughness and introduction of strain rate sensitivity in the sheet material model. The study will use a FE-model of a part presented in previous papers. © 2019 The Authors. Published by Elsevier B.V.

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    Friction in sheet metal forming
  • 24.
    Sigvant, Mats
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Tatipala, Sravan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Andreasson, Eskil
    Tetra Pak Packaging Solutions, SWE.
    SMART STAMPING: IMPROVED QUALITY IN STAMPING BY MODEL DRIVEN CONTROL2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Sheet Metal Forming is a very complex manufacturing process with a number of non-linearities, e.g. large deformations, localisation, elastic-plastic materials, pressure and velocity dependant friction conditions and structural deficiencies in the die and press, present and interacting simultaneously. This leads to disturbances in running production that results in production waste, e.g. down time for the press line and cost for rework and scrapping of parts. These production problems are also hard to understandand solve based on experience and analytical models due to the presence of several non-linearities. An alternative is to try to solve these problems proactively before they occur. This could be done with model based control by creating a digital twin of the die-set and the press line. Therefore, a virtual production process is developed to be able to use as knowledge building and as engineering tool during development, manufacturing, issue resolution and optimization. In this paper presents the authors ideas and plans for research and other activities within the area of model based control of sheet metal forming.

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  • 25.
    Tatipala, Sravan
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Pilthammar, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik. Volvo Cars.
    Sigvant, Mats
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik. Volvo Cars.
    Wall, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Johansson, Christian
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Introductory study of sheet metal forming simulations to evaluate process robustness2018Ingår i: IOP Conference Series: Materials Science and Engineering, Institute of Physics Publishing (IOPP), 2018, Vol. 418, artikel-id 012111Konferensbidrag (Refereegranskat)
    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.

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