Many components in engineering applications are subjected to multiple and uncorrelated loads during service‐life. Thus, multiaxial stress states with rotating principal axis may occur. For this special case of multiaxial and non‐proportional stresses the results of many fatigue assessment methods which are used in the industrial practice are of poor quality. Fatigue lifetimes of shoulder shafts (quenched and tempered steel) are estimated on the basis of the extended short crack model in combination with a multiaxial notch approximation. This approach shows a high accuracy but the precise modelling of non‐proportional hardening effects requires a complex plasticity model. Therefore, a simplified approach for considering non‐proportional hardening is introduced. Thus, the calculation method gets applicable in the engineering practice. Results are compared to well‐established engineering approaches. Furthermore, new component tests on die‐cast housings with two load channels under constant and variable amplitude loading are presented and discussed. The loads are applied in‐phase (proportional) as well as out‐of‐phase, which results in a high non‐proportional stress path at the crack initiation site. The effects of multiaxial and non‐proportional stress states seem to play a minor role in the fatigue assessment of die‐cast housings.

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A scalar measure, which describes the non-proportionality of local stress paths in engineering applications, is introduced. For this purpose the moment of inertia approach by Meggiolaro is modified in a way that the stress time history is evaluated in a tresca-stress-space. This modification makes the non-proportionality factor invariant with respect to the coordinate system. An optimization procedure is implemented to derive a test setup for new component tests with 2 load channels. The aim of the planned tests is to get a high non-proportionality at the potential crack initiation site. It is not possible to obtain a high non-proportionality factor at the failure location without selective weakening of the component (housing of a rear axle steering). Therefore specific areas of the structure are cut out and the optimization procedure is repeated. As a result of the optimization a test setup with high local non-proportionality at the potential crack initiation site is achieved for the weakened structure. Another setup with slightly less non-proportionality but with a very localized damage is derived. This setup is preferred, because of the robustness in the physical test.

The automotive industry is currently undergoing far-reaching structural changes. Automobile manufacturers are pursuing intensive scientific research and technological development in the field of alternative drive systems, such as electric powertrains. If electric car batteries are charged with regenerative generated electricity, their emission output is zero (from a well-to-wheel view). Furthermore, electric drives have very high efficiency. At cold temperatures, however, the battery power drops due to energy-intensive loads, such as the heating of the passenger compartment, and this consequently reduces the range dramatically. Therefore, the focus of this research work is external energy supply for the required heat capacity. The auxiliary energy may be generated by renewable energy technologies in order to further improve the CO₂ balance of electric vehicles. The paper deals with the design, application, and testing of a biofuel-operated heater to heat the passenger compartment of a battery-powered electric car (a Renault ZOE R240). The practical use of the heating system is analyzed in several test drives, performed during winter 2018. The results as well as the range extension of the electric car that can be achieved by substituting the on-board heating system by the fuel-operated heater are quantified herein.

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