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Steel wire ropes offer manufacturer-independent safety performance, while the durability performance can be different. To assess the damage status of a wire rope during its service, fail-safe methods are used, so it is necessary to know the progression of the damage to apply them. This paper proposes an analytical method for estimating the fatigue life of steel wire ropes. Using a dimensionless analysis, the characteristic damage curve of each rope category has been suggested, setting the basis of a predictive maintenance procedure extendable to all areas of rope application where bending fatigue is the first discard criterion for rope replacement. Rotary bending fatigue tests are performed on different rope construction specimens, and the evolution of broken wires is monitored. It has been demonstrated that the trend of breakage level is exponential with time, regardless of the type of rope and the stress level imposed.

Rolling contact fatigue phenomenon was investigated on unfilled PEEK and on three different PEEK composites: 10% carbon micro-fiber, graphite and PTFE filled matrix, 30% carbon micro-fiber filled matrix, 30% glass micro-fiber filled matrix. For this aim, roller-shaped specimens were machined from extruded bars of these materials and subjected to rolling contact tests at different contact pressure levels by means of a four roller machine. Contact pressure-life diagrams and wear rates were so obtained and compared, highlighting a relationship with monotonic and hardness materials properties. Microscopic observations of contact surfaces and transversal section of the specimens also allowed observing the damage mechanisms occurred in the materials tested and the effects of the filler. In particular way, deep radial cracks appeared on unfilled PEEK, while spalling and delamination phenomena where found on composites. Diffuse microcracks were found at the filler-matrix interface of the composites specimens, confirming that the fatigue life of these materials is essentially determined by the crack propagation phase, also under rolling contact loading.

Byline: G. Donzella, A. Pola, L. Solazzi, G.P. Marconi The aim of this work is to examine the residual stress distribution in carburised steel components subjected to shot peening. A numerical model of the shot peening was developed by means of the ABAQUS explicit code, taking into account the variation in the material mechanical properties from the surface towards the core, defined on the base of the microhardness profile experimentally measured. The rate dependent hardening of the material was also considered for these analyses, together with the softening due to the heat generation during the impact. The model was verified by experimental residual stress measurements carried out on disk specimens, carburised and shot peened as in a typical industrial application. The analyses, repeated for different values of shot velocity and dimensions, show the influence of these parameters and that of the carburising depth on the final residual stress distribution.