ارزیابی فرسودگی اتصالات جوش داده شده
Abstract
1-Introduction
2-Experimental investigations
3-Numerical investigation
4-Evaluation
5-Conclusions
Acknowledgements
References
Abstract
The electromagnetic pulse technology (EMPT) is a joining process similar to the explosion welding. In the process, a flyer-sheet is accelerated towards a target-sheet using electromagnetic fields. During impact high normal and lateral contact forces are generated which join the sheets on an atomic level. This process can be automated for joining thin sheets and is therefore especially suited for mass production, e.g. in the automotive industry. The resulting joints are not comparable to ones made by common MIG/MAG or laser welding processes since no heat is induced. This leads to the question if the standard approaches to assess the weld in terms of their fatigue behavior can be used also and if a reliable fatigue assessment can be achieved. In the paper, the fatigue strength of EMPT-welded connections under constant amplitude loading is presented. Common assessment approaches like the notch stress approach are applied to assess the fatigue life. A comparison between numerically derived fatigue life and experimental tests shows a good agreement and proves the applicability of established approaches
Introduction
Welding is an important joining technique which is commonly used to join two parts of equal material. In common welding technologies, such as GMAW or laser welding, the material is heated above the melting point. During solidification the materials are joined. These most common welding processes come along with some disadvantages. Due to the localized heat input and the yielding of the material during heating and cooling distortion as well as residual stresses may be induced. These implications lead to further problems in the assembling of structures as well as a decrease in the static and fatigue strength. In addition, a heterogeneous material is generated which exists of the weld metal, the heat affected zones and the base metal. Such a joint shows usually a lower strength compared to the base metal. Further disadvantages of the common processes are the long joining times as well as environmental and health issues due to the welding fumes. Another way to join two materials but to avoid some of the mentioned side-effects is the welding method called electro-magnetic pulse technology (EMPT) or magnetic pulse welding (MPW). It is based on the very high acceleration of one metal sheet called flyer upon an static metal sheet called target with an electro-magnetic pulse. This joining techniques is from the physical principles closely related to the explosion welding which is a proven and reliable method of joining plates mainly of different materials, e.g. copper to steel [1].