Enhancement of joinability and joint characteristics in mechanical joining processes by tailor heat-treated aluminium semi-finished products

汽车工业对减轻汽车重量同时提高碰撞安全性的要求越来越高，需要新的设计方法。一种强度更高的钢铝混合材料为这两个问题提供了可能的解决方案。然而，材料组合也与连接技术的新挑战有关。在这种情况下，近年来机械连接工艺的使用得到了广泛的研究。然而，正如人们所知的，从目前的技术水平来看，高强度材料的连接还不是无限的可能。因此，研究项目的目的是通过使用局部短期热处理来增强高强度异种材料的接合性和由此产生的结合强度。7000系列铝合金在短期热处理过程中产生的软化效应可用于改善位于冲孔侧的高强度铝材料的物料流动。在基础科学研究的基础上，分析了定制热处理毛坯对连接过程和连接点结合强度的影响。这代表了定制热处理半成品的一个新的应用领域，到目前为止，它只用于扩大零件制造的成形极限。通过分析剪切-夹紧过程中复杂的物料流动，建立对剪切-夹紧过程的整体认识。考虑到所涉及的相互作用，应根据短期热处理和剪切-夹紧过程的数值模型确定连接区理想的强度分布。通过试验研究，验证数值计算结果，确定接头的力学性能和强度。

The increasing demands on the automotive industry to reduce the vehicle weight and simultaneously increase the crash safety require new design approaches. A material mix of steel and aluminum with increased strengths provides a possible solution for both problems. However, a material mix is also associated with new challenges for joining technology. In this context the use of mechanical joining processes has been intensively investigated in recent years. However, as it is known from the state of the art, the joining of high-strength materials is not yet unlimited possible. Therefore, the aim of the research project is the enhancement of joinability and the resulting bonding strength of high-strength dissimilar materials by the use of a local short-term heat treatment. The softening effect that occurs during the short-term heat treatment of aluminum alloys of the 7000 series can be used to improve the material flow of the high-strength aluminum material located on the punch side. Based on fundamental scientific investigations, the influence of tailor heat-treated blanks on the joining process and on the bonding strength of the joining point will be analyzed. This represents a new field of application for tailor heat-treated semi-finished products, which until now have only been used to expand the forming limits in part manufacturing. By analyzing the complex material flow in the shear-clinching process, a holistic process understanding will be established. Taking into account the interactions involved, an ideal strength distribution in the joining zone should be determined based on numerical models of the short-term heat treatment and the shear-clinching process. By means of experimental investigations the numerical results should be validated and the mechanical properties and the joint strength should be identified.