Investigation of Modeling technique for Laser Welds in Crash Analyses

Recently, interest in the laser welding to assemble components of the auto-body has increased in the automotive industry due to its productivity, efficiency and reliability. When car crash occurs, crash performance and deformation mode of the auto-body are changed according to the location and shape of laser welds. In order to understand the crash behavior of auto-body through the FE analysis, the laser welded parts should be modeled physically compatibly and simply. This paper evaluates the compatible FE modeling technique for laser welds in crash analyses. A single laser welded part in a stich shape is modeled by a group of numerous beam elements or hexahedron elements. FE analyses of cross tension test and lap-shear test under the quasi-static condition were carried out according to the number of elements, panel mesh size, and the relative position of the laser weld to the panel mesh. From the comparison between experiment and analysis results which are load and displacement curve, suitable modeling technique, which has hardly influence on analysis results, for laser welds in crash analyses is suggested

Dynamic Material Properties of the Heat-Affected Zone (HAZ) in a Resistance Spot Weld

This paper propose a methodology to identify the dynamic material properties of the HAZ near the base metal in a resistance spot weld at various strain rates. The mechanical properties of the HAZ of SPRC340R were obtained by fabricating thermal simulated HAZ specimens which have similar hardness and microstructure as the actual weld HAZ near the base metal. The thermal simulated HAZ specimens are fabricated using the Material Thermal Cycle Simulator (MTCS). Then, dynamic tensile tests are performed at various strain rates of 0.001 /sec to 100 /sec. Finite element analysis of tensile-shear tests were done under the static and dynamic loading conditions to verify the validity and effectiveness of thermal simulated HAZ properties. Load and displacement curves were obtained with and without applying the material properties of HAZ. The curves are compared to the experimental data. The amount of errors between the analysis and experiment were reduced when the material properties of thermal simulated HAZ were applied to the HAZ. The comparison demonstrates that the dynamic material properties obtained from thermal simulated HAZ specimens are valid for the analysis of spot welded specimens

Auto-body Crash Analyses Considering Dynamic Failure of a Spot Weld

In order to get more effective and precise simulation results on the crash analyses of auto-body components, it is needed to adopt the dynamic material properties and the history of fabrication. A resistance spot weld in general finite element models is described as a rigid beam without failure model of a spot weld at the location of the weld. For more accurate crash analyses, not only the dynamic material properties and the forming effect of each auto-body component but also an appropriate description method of a spot weld in the finite element model and the dynamic failure model of a spot weld should be considered in the crash analyses. In this paper, the numerical simulation is carried out considering the dynamic material properties, forming effect of each auto-body component, and the dynamic failure model of a spot weld. A resistance spot weld is characterized as a beam element connecting two shell elements of each sheet at the location of the weld. Comparison between physical crash tests of the front side member and crash analyses is investigated. This study performed is to examine the effect of physical material properties, the fabrication history, and the assembly method on the crash analyses results such as the reaction force, the crushing distance and the deformed shape of auto-body components. The analysis results demonstrate that the accurate prediction of crash analyses results on the front side member is achieved