"Accurate material models are critical for any CAE analysis," Steven Sheng, Formability Engineer, General Motors

The 1st GALM summit on Modeling, Simulation and Crash Testing Of Automotive Lightweight Materials will come to Detroit, Michigan on 26-27 January 2016 and bring with it 20+ case studies from OEMs, software developers and material experts. Covering the most important areas from cost efficiency and accuracy in modelling aluminum and composite properties to predicting lightweight material life-cycles and accurate crash simulation, experts at the top of their field will assess the best practices for accurately and efficiently modeling and simulating lightweight materials. Key OEM speakers of the congress include General Motors, Toyota and Honda.

Steven Sheng has worked on a wide variety of sheet metal forming projects at various tier suppliers and is now working as a formability engineer at the General Motor Company. Steven's work particularly focuses on FEM simulation based stamping feasibility analysis, process design, and project management, as well as testing and modeling sheet metal materials. He is one of the key speakers in the Modeling, Simulation and Crash Safety Congress.

An excerpt from his Pre-Conference Interview:

Your presentation at the Crash Simulation Summit will look at the question of predicting fracture in warm forming magnesium alloys. Could you briefly outline the concept for readers and what new knowledge they will be able to take away with them?

Steven Sheng: A method to represent forming limit for warm forming Mg alloy sheet material will be presented. In the method, the strain rate and temperature effect is presented concisely by a single parameter of Zener-Hollomon parameter. Thus, the forming limit can be represented as a Forming Limit Surface.

Traditionally, Forming Limit Curves (FLCs) are used to identify fracture/necking failure in sheet metal forming. At elevated temperatures, the Mg alloys exhibit strong rate sensitivity and thus many FLCs are needed to represent different forming conditions. Those FLCs are not only costly to be obtained but also inconvenient to be used in FEM simulations. In this presentation, a new method to represent forming limit for warm forming Mg alloy sheet material will be introduced. In the method, the strain rate and temperature effect is presented concisely by a single parameter of Zener-Hollomon parameter. Thus, the forming limit can be represented as a Forming Limit Surface.

Since only one surface is needed, the method could reduce the efforts of laboratory testing and provide a convenient tool in the development of thermal forming processes. The usefulness of the Forming Limit Surface is demonstrated by predicting fracture in warm forming magnesium alloy AZ31B in isothermal conical cup test and non-isothermal round cup draw test.

What do you see as the most important hurdles to overcome in implementing CAE and FAE technologies for safety testing of lightweight materials? What optimizations need to be implemented?

Steven Sheng: The accuracy of simulation result, which is affected by many factors, such as material modeling, mesh quality, accuracy of algorithm etc.. The product development can be regarded as a multi-objective optimization problem. Thus, a multi-objective optimization solver, which can be adapted with different CAE solvers, is needed.

What are some of the potential applications and implications of improved material models and more accurate safety simulations to the manufacture of lightweight vehicles?

Steven Sheng: The accuracy of CAE prediction depends on material modeling. Accurate material models are critical for any CAE analysis.

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