Effects of cracks on contacts operating under high contact force

Cracks in silver tin oxide contacts were produced by varying cone angles during cold heading. The investigation examined which factors affected material erosion and contact reliability. The results indicated that crack size alone did not accelerate material erosion during electrical testing. The electrical loads used (inductive and resistive) during testing did not have an effect on contact performance when cracks were present on the contact´s head and contact force was maintained at 0.32 lbs./146 grams. Alternating the temperature (68°F (20°C) and 257°F (125°C)) every 25,000 and 62,500 cycles during inductive and resistive load did not affect contact material erosion. The factors which degraded contact material erosion were crack size, electrical load (inductive/resistive) and contact closing force.