Use of FE-analysis for predicting and verifying the design of an automotive component forming process with special regard to macro geometric defects

Sammanfattning: This thesis includes four appended papers. The thesis describes the challenges and advantages of the use of FE-analysis in the design of a component forming process in the automotive industry. Today, shortened lead-times in the automotive industry have dramatically increased the need for more efficient development methods in each stage of the process development chain. In order to decrease the long lead-time for producing a forming tool, sheet-metal-forming simulation was introduced. To successfully implement sheet-metal-forming simulation it is important to establish an efficient exchange of information. Efficient information handling will also generate a more accurate basis for decisions aimed at reducing the number of changes in the development phase to achieve the specified automotive part or process. Efficient information exchange can be established by using a database where animations from the sheet-metal-forming simulations are stored. The database should be accessible from the Internet in order to enable direct investigation and analysis by authorised persons. Today, sheet-metal-forming simulations are able to predict e.g. thinning, cracks and forces with high accuracy. The investigation showed that sheet-metal-forming simulation is superior in reducing lead-time and costs compared with the use of try-out tools. The Karafillis-Boyce (1993) material model has been implemented in the explicit, dynamic software LS- DYNA A special optimisation program, written in the programming language C, was developed to find proper parameters for the above-mentioned material model. The results showed that the model by Karafilli and Boyce provided superior results compared with the models by Barlat and Uan (1989), and Hill (1948), respectively. There are two important phenomena that sheet-metal-forming simulation cannot yet adequate predict, namely surface defects and springback. The accuracy regarding the prediction of surface defects and springback was evaluated by analysing a double curved sheet-metal part. This part resembled the area around the fuel filler lid. Based on this model, experiments and sheet-metal-forming simulations were performed and the results were compared. The results showed that, while sheet-metal-forming simulation could not adequately predict the magnitudes of the defects, it could successfully predict the location of the defects.