New approach of effective weld layout on vehicle body structure

The automotive industry is an important sector increasingly for developing country economies. In our country, automotive sector is one of the leading sectors in manufacturing industry. Competition within this sector is increasing rapidly. Therefore, efficient use of resources and shortening of the production time are very important factors. The most important material is steel in the automotive industry. Steel is widely preferred today due to material technology and production costs in despite of be aimed lighter vehicles for saving fuel. The steel industry has remarkable price performance and recycling possibilities. The joining of steel sheets is often done by welding in the automotive field. A resistance spot welding is used commonly. A commercial vehicle has on average around 3000 or 8000 spot welds. The number of spots is affected production times and production costs significantly. This issue has become increasingly important in recent years. For this reason, automotive main industrial companies continue to work on this issue. In this thesis, the spot welds on the commercial vehicle which is modelled with full-scale finite element have examined. The goal of this thesis is to obtain the optimal layout of the spot welds on the vehicle without any loss of structural strength and rigidity in addition to what is mentioned to reduce number of the spot welds. In order to determine the optimal layout of the spot welds, the vehicle model is filled with spot welds as many as possible in consideration of production constraints of welding. The spot welds which work efficiently are determined after topology optimization analysis. Effective spot welds will be preserved on the car. However, spot welds that do not work efficiently will be removed from the car. This approach is called density method in the topoloy optimization methodology. The new layout of the spot welds is revealed. The new layout of the spot welds should not cause any deterioration on performance of the vehicle to achive success criterion of the torsional, bending and modal analysis. Some loading scenario, constraints and acceptance are used during topology optimization to meet this criterions. As a result of the analysis, the number of the spotwelds is reduced 20%. There is almost 1-2% change in the bending and torsion stiffness. Also the results of the deflection and stress have no significant change. It can be expressed that the spot weld optimization has been applied to the vehicle model successfully. In conclusion, the number of spotwelds is an important issue for vehicle costs and production time. For this reason, the topic of the thesis has offered new approaches to give effective results in general terms.