An Investigation on Spot Weld Modelling for Crash Simulation with LS-DYNA
Because of weight reduction necessities, high-strength steels are more and more widely used in bodyin-white (BiW) structures in recent years. Concerning the behaviour of such structures during a car crash the joints between high-strength materials are seen as critical points. Therefore the properties of welded joints, especially the failure behaviour at high velocities have to be taken into consideration during the development phase. In this paper, we present an overview on the current activities at the DaimlerChrysler AG regarding investigations on spot weld failure behaviour. A suitable model that is able to represent the failure behaviour of spot welds in BiW structures and that is independent of mesh sensitivity has been developed. An elasto-plastic material model based on von Mises plasticity (MAT_100) has been further enhanced with a new failure criterion. The model has been implemented into LS-DYNA. The material as well as the failure behaviour is verified and calibrated through precision experiments conducted on specimen level and later validated on component level.
Accurate Spot Weld Testing for Automotive Applications
Typical vehicles contain more than 3000 spot welds—whose failure must be accurately predicted in crash simulations. A new test method is proving useful for accurately defining spot weld failure parameters.
Ultimate Strength of Resistance Spot Welds Subjected to Combined Tension and Shear
A new test setup and data concerning the ultimate strength behavior of resistance spot welds in a mild strength steel subjected to combined tension and shear loads are presented. A test plan based on a design of experiments (DOE) with three design factors (coupon width, coupon length, and nugget diameter) was conducted to investigate the influence of the factors on the ultimate strength of the resistance spot welds under different loading angles. In this program, test loads were monotonically applied to the resistance spot weld at a specific angle until the load carrying capacity of the resistance spot weld was exceeded. It was found that the nugget diameter contributes the most (more than 70%) to the total variation of the recorded ultimate strength and that the coupon length has little effect. A deterministic ultimate strength model was proposed to take into account the interaction of in-plane shear and 90° out-of-plane tensile loading in the resistance spot weld. A reliability model was also demonstrated to evaluate the ultimate strength of a single resistance spot weld.