Congratulations Johan Pilthammar, PhD!

Congratulations Johan Pilthammar, PhD!

Johan Pilthammar successfully defended his PhD thesis “Towards Virtual Tryout and Digital Twins: Enhanced Modeling of Elastic Dies, Sheet Materials, and Friction in Sheet Metal Forming” in COVID-19 style with some local people keeping distance and web casting the presentation and also having grading committee and opponent taking part online. The thorough questioning of Johan’s PhD thesis was done by Prof. Wolfram Volk (Technische Universität München, Germany).

Abstract

Competition and complexity in the global car market are continuously increasing. To gain an edge in the market while making a profit, each competitor in the market needs a strong focus on technology development. Such a focus will increase the value of the product for the customers. On top of the challenges of developing the technical content of the cars, it is equally important to develop the manufacturing processes. This will enable the production of technically advanced and attractive products at a competitive cost.

An important manufacturing process within the automotive industry, and the focus of this PhD thesis, is sheet metal forming (SMF). The SMF process has been simulated for the past few decades with finite element (FE) simulations, whereby factors such as shape, strains, thickness, springback, risk of failure, and wrinkles can be predicted. A factor that most SMF simulations do not currently include is die and press elasticity, limiting the reliability of SMF simulations for virtual die tryout and digital twins. This factor is instead handled manually during the die tryout, which is time-consuming and expensive.

The importance of accurately representing press and die elasticity in SMF simulations is the focus of this research project. The objective is to achieve virtual tryout and production support through SMF simulations that consider elastic die and press deformations. Accurate simulations of die tryout, or dies in running production, are found to be impossible without the inclusion of reliable representations of elastic dies and presses.

Accurate CAD models of stamping dies are common. Strategies are presented for how to include them in SMF simulations models that are easy to set up and fast to solve. Full representations of presses are rarer. Methods for measuring and inverse modeling the elasticity of presses are therefore presented together with an overview from the literature of other methods. A unified method that is reliable and cost-efficient for the stamping industry is of high interest.

SMF simulations with elastic dies will only yield accurate predictions if reliable models of sheet materials and lubrication systems are included. Friction in particular is highly dependent on die deformations since contact pressure is an important parameter in determining the friction level. Reliable models for both friction and sheet materials are dependent on accurate experimental data and characterization methods.

Including elastic die and press deformations in SMF simulations, together with reliable representations of friction and sheet materials, has immense potential to reduce the lead time of stamping dies. The simulation methods that include elasticity will also be vital for more accurate digital twins of press lines.

Download full thesis here: http://urn.kb.se/resolve?urn=urn:nbn:se:bth-20047

Nailing it

After detailed scrutiny by the opponent, and follow-up questioning by the grading committee consisting of:

  • Prof. Malin Åkermo, Kungliga Tekniska Högskolan
  • Prof. Niclas Strömberg, Örebro Universitet
  • Dr. Roald Lingbeek, Autoliv B.V. & KG, Tyskland

the audience had the chance to put forward some questions.

The grading committee then had their discussion and eventually delivered the verdict; a clear PASS!

Johan then finally got the chance to nail his thesis to the wooden plank, signalling that it is DONE!

Nailing the thesis!

Supervisors of the research has been Professor Sharon Kao-Walter and PhD Mats Sigvant.

We gratulate our newest PhD on such an important milestone in his research career!

Johan with supervisors, grading committee, opponent and department head Johan Wall.

For more information, PhD Johan Pilthammar, johan.pilthammar@volvocars.com.

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