VHCF-behavior of helical compression springs made of different materials

This paper reports on procedure and preliminary research results of long-term fatigue tests up to a number of 109 cycles on shot peened helical compression springs with two basic dimensions, made of three different spring materials. The corresponding research project was initiated together with a working group of the Association of German Springs’ Industry (VDFi – Verband der Deutschen Federnindustrie). The test springs were manufactured of oil hardened and tempered SiCr- and SiCrV-alloyed valve spring steel wires and of a stainless steel wire with diameters of 1.6 mm and 3.0 mm and finally shot peened. Fractured test springs were investigated by stereo-microscope, Scanning Electron Microscope (SEM) and by means of metallographic microsections in order to analyse the fracture behavior and the failure mechanisms. It becomes obvious that the various spring types in test exhibit different fatigue properties and also different failure mechanisms in the VHCF regime.