Search Results

Recent trends in mechanical engineering are focusing on optimization of components with respect both to weight and lifetime by using numerical simulation even in the early design stages. For a reliable prediction of in service performance by simulation, both loading as well as different damage and failure mechanisms that may be activated during operation have to be known. In mechanical engineering applications, cyclic loadings are most common. In many assemblies of moving components, contact problems under various lubrication conditions are lifetime-limiting. There, relative motion of contacting bodies combined with high loads transmitted via the contact surface lead to fretting fatigue failure. In this contribution a few selected results of a currently conducted research project are presented. The aim of this study was to examine the material behavior of a surface stressed steel. The influence of the Fretting regime on fatigue properties has been investigated.

Aluminum high-pressure die casting (HPDC) is used to reduce the cost and weight of various components in the automotive industry. The main problem with HPDC components is related to inherent flaws (porosity, oxide skins, etc.) that are difficult to avoid. The fatigue of aluminum HPDC parts is typically calculated using two S–N curves; one accounts for flaws in the bulk material and the other for the pore-free surface layer. This does not provide an accurate estimate for computation of the lifetime or safety against failure of the component. This paper presents a unique way to compute the fatigue safety factor taking into account the pore distribution of the component. The material model used is the so-called Kitagawa-Haigh diagram. The pore model provides a statistical distribution of pores within a defined region in the component.

This paper is concerned with the evaluation of the fatigue life and fracture mechanisms of a hypoid gear tooth root. The common milling manufacturing method for hypoid gear wheels is compared to the potentials of the innovative manufacturing method orbital forging. Extensive material and geometry analysis are performed and the local fatigue strength of the case hardened steel 18CrNiMo7-6 used in serial production is compared to the orbital forged and case hardened JIS steel SCM420H. Therefore a unique single contact engagement test procedure for hypoid gear wheels has been developed. The present investigations indicate a high potential for using orbital forging in the serial production. However, for an expected significant increase of the tooth root load carrying capacity due to the positive effects of forging (e.g. compressive residual stress, fiber orientation) and reaching the required geometry accuracy the process orbital forging has to be optimized in further steps.