Minimum Fretting Amplitude in Medium Force for Connector Coated Material and Pure Metals

For automotive applications, the mechanical behaviour of the contact area under vibrations is one of the key factors for connector reliability. Such vibrations are typically in the range of 10-2000 Hz and result in displacements of only a few microns, at the contact interface. In the present study, a bench test has been developed to control more representative motions down to 1 μm. The objective is to determine the minimum amplitude for fretting-corrosion degradation based on the evolution of contact resistance and to study the effects of the material, the contact force, the coating for these low displacement amplitudes. To obtain the limit of the appearance of fretting, a sub-micrometer incrementing displacement amplitude methodology was applied on high stiffness bench test including a double PZTactuator. It was found that the fretting degradation starts to occur from 2 μm to 6 μm when the contact force is from 0.5 N to 2.5 N with a tin coated terminal. Moreover pure copper, tin and nickel have similar amplitude fretting limits while noble metals confirm the absence of fretting up to 10 μm amplitude and for a large number of operations (10⁶ cycles). Best fitting of the obtained minimum fretting amplitude data to Mindlin equation is discussed and improved by correcting factor.