Fretting loading, contact conditions

The establishment of the interrelationships between polymer fracture properties and contact fatigue behaviour requires some knowledge of the contact stress field. The specificity of fretting loading is that, depending on the applied contact load and imposed relative displacement, two different contact conditions can be achieved within the interface [54,55] (Fig. 5) ... 

Fig. 5 Schematic description of the contact conditions encountered under small amplitude cyclic lateral micro-motions (fretting). S is the applied lateral displacement, Q is the lateral force and P is the applied constant normal load. The elliptic and trapezoidal Q(S) loops correspond to partial slip and gross slip condition respectively...

Current-time transients of NiP, NiPSiClO, NiPSiCSO and NiPSiC200 coatings under tribocorrosion conditions in 0.6 M NaCl (conditions contact configuration ball-on-plate coated steel as plate and corundum ball (5 mm 0) as counter body load 8 N frequency 2 Hz stroke length 1 mm number of fretting cycles 3500.Tests were conducted with an impressed anodic potential of + 400 mV vs. SCE) (Malfatti et a ., 2009). 

One major benefit of bonded joints is their superior fatigue resistance compared with mechanically fixed assemblies. The dynamic performance of anaerobic adhesives has been assessed. It has been proposed that, since the adhesive makes intimate contact with the metal surface, it fills all the micro-roughness in the surface, so ensuring that the bond line is completely filled. This means that loads, particularly compressive loads, are more evenly distributed over the joint area in comparison with mechanically assembled parts, especially when these are interference fitted. In the latter case there is rarely more than 20% of the available bond area actually in contact. In addition, the ingress of air is suppressed and fretting corrosion is eliminated. The net result is a superior performance under demanding dynamic conditions. 

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