Papers by Author: Tim Medhurst

Abstract: The influence of forming on the cyclic behaviour of various thin sheet metals with austenitic phases is looked into, with the main focus lying on the variation of cyclic parameters and the progression of work hardening over the materials’ fatigue life. There is a marked interaction of hardening due to increased dislocation density resulting from forming and hardening due to cyclic straining under varying strain amplitudes of strain controlled LCF testing. This is strongly dependant on the degree of forming and the amplitude of the following cyclic loading. Also, the temperature influence during forming of addtional forming elements in a temperature controlled die on the fatigue performance of austenitic and complex three phase steels was analysed, showing a marked influence of the forming temperature on the fatigue performance, enabling positive effects to be achieved by choosing suitable material specific forming temperatures.

Abstract: The advantages of low heat joining techniques, such as low distortion and little influence on the local material properties due to the low introduced amount of heat, shall be made usable for the manufacture of high strength structures by increasing the process reliability. The dependency between the parameters of the joining process, the seam geometry, the type of solder, the load type und the fatigue life especially of soldered structure with local strengthening shall be examined to allow a calculative estimation of the part’s life.

Abstract: A fast transfer of new manufacturing- and material technologies to actual design use is only to be expected if calculation concepts exist, which allow an easy estimation of the parts’ strength properties. This Collaborative Research Project (CRP) will develop new manufacturing and joining techniques to create high strength structures by adjusting the local strength properties of parts. These types of structures are usually loaded dynamically. To specifically optimise the fatigue behaviour, stiffness and weight of a structure, the influences of locally strengthening manufacturing processes must be considered in the fatigue life calculation concept. It is the goal of this project to include a simulation of the fatigue behaviour in the process simulation of manufacturing. Recently research on the influence of local strengthening by cold forming on fatigue life was undertaken in cooperation within another research project. The fatigue life calculation of sheet metal structures can be based on a calculation concept developed in CRP 362, subproject C5, which takes into account the influence of forming, [1,2,3,4]. This concept shall be extended to incorporate the effects of local martensite forming in the cold formed areas.