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Framework for Simulation-Driven Design of Stamping Dies Considering Elastic Die and Press Deformations
Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.ORCID iD: 0000-0002-6526-976X
Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
2017 (English)In: 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, Published 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.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2017. Vol. 1896, article id 010001
Series
AIP Conference Proceedings, ISSN 0094-243X
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:bth-15392DOI: 10.1063/1.5008124ISI: 000419825000167ISBN: 9780735415805 OAI: oai:DiVA.org:bth-15392DiVA, id: diva2:1153437
Conference
20th International ESAFORM Conference on Material Forming, Dublin
Funder
VINNOVA, 2016-03324Available from: 2017-10-30 Created: 2017-10-30 Last updated: 2018-01-25Bibliographically approved
In thesis
1. Elastic Press and Die Deformations in Sheet Metal Forming Simulations
Open this publication in new window or tab >>Elastic Press and Die Deformations in Sheet Metal Forming Simulations
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Never before has the car industry been as challenging, interesting, and demanding as it is today. New and advanced techniques are being continuously introduced, which has led to increasing competition in an almost ever-expanding car market. As the pace and complexity heightens in the car market, manufacturing processes must advance at an equal speed.

An important manufacturing process within the automotive industry, and the focus of this thesis, is sheet metal forming (SMF). Sheet metal forming is used to create door panels, structural beams, and trunk lids, among other parts, by forming sheets of metal in press lines with stamping dies. The SMF process has been simulated for the past couple of decades with finite element (FE) simulations, whereby one can predict factors such as shape, strains, thickness, springback, risk of failure, and wrinkles. A factor that most SMF simulations do not currently include is the die and press elasticity. This factor is handled manually during the die tryout phase, which is often long and expensive.

The importance of accurately representing press and die elasticity in SMF simulations is the focus of this research project. The research objective is to achieve virtual tryout and improved production support through SMF simulations that consider elastic die and press deformations. Loading a die with production forces and including the deformations in SMF simulations achieves a reliable result. It is impossible to achieve accurate simulation results without including the die deformations.

This thesis also describes numerical methods for optimizing and compensating tool surfaces against press and die deformations. In order for these compensations to be valid, it is imperative to accurately represent dies and presses. A method of measuring and inverse modeling the elasticity of a press table has been developed and is based on digital image correlation (DIC) measurements and structural optimization with FE software.

Optimization, structural analysis, and SMF simulations together with experimental measurements have immense potential to improve simulation results and significantly reduce the lead time of stamping dies. Last but not least, improved production support and die design are other areas that can benefit from these tools.

Abstract [sv]

Aldrig tidigare har bilindustrin varit så utmanande, intressant och spännande som idag. Ny och avancerad teknik introduceras i en allt snabbare takt vilket leder till ständigt ökande konkurrens på en, nästan ständigt, ökande bilmarknad. Den ständigt ökande komplexiteten ställer även krav på tillverkningsprocesserna.

En viktig process, som denna licentiatuppsats fokuserar på, är pressning av plåt. Tillverkningstekniken används för att forma plåtar till dörrpaneler, strukturbalkar, motorhuvar, etc. Plåtar formas med hjälp av pressverktyg monterade i plåtformningspressar. 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 hanteras istället manuellt under, den oftast långa och dyra, inprovningsfasen.

Detta projekt har visat på vikten av att representera press och verktygsdeformationer i plåtformningssimuleringar. Detta demonstreras genom en analys av ett verkligt pressverktyg som belastas med produktionskrafter. Det är inte möjligt att uppnå bra simuleringsresultat utan att inkludera verktygsdeformationer i simuleringsmodellen.

Uppsatsen beskriver även numeriska metoder för att optimera och kompensera verktygsytor mot press och verktygsdeformationer. För att dessa kompenseringar ska stämma är det viktigt att man representerar både verktyg och press på ett korrekt sätt. Förslag på en metod för att mäta och inversmodellera pressdeformationer har utvecklats, metoden är baserad på mätningar med DIC-systemet ARAMIS och optimering i FE-mjukvaror.

Optimering, strukturanalys, och plåtformningsanalys tillsammans med experimentella mätningar har en stor potential att förbättra plåtformningssimuleringar samt reducera ledtiden för pressverktyg. Sist men inte minst, andra positiva effekter är en enklare och smidigare konstruktionsprocess och förbättrad produktionssupport.

Place, publisher, year, edition, pages
Karlskrona: Blekinge Tekniska Högskola, 2017
Series
Blekinge Institute of Technology Licentiate Dissertation Series, ISSN 1650-2140 ; 2
Keywords
Sheet Metal Forming, Stamping Die, Stamping Press, Structural Analysis, Finite Element Simulation, Optimization, Digital Image Correlation, Inverse Modeling
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:bth-15481 (URN)978-91-7295-345-1 (ISBN)
Presentation
2017-12-14, 10:00 (Swedish)
Opponent
Supervisors
Funder
VINNOVA, 2016-03324
Available from: 2017-11-10 Created: 2017-11-10 Last updated: 2017-12-08Bibliographically approved

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Wall, JohanSigvant, Mats

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