Investigation of electrical chatter in bifurcated contact receptacles

Electrical switches are often subjected to shock and vibration environments, which can result in sudden increases in the switch's electrical resistance, referred to as “chatter”. This paper describes experimental and numerical efforts to investigate the mechanism that causes chatter in a contact pair formed between a cylindrical pin and a bifurcated receptacle. First, the contact pair was instrumented with shakers, accelerometers, laser doppler vibrometers, a high speed camera, and a “chatter tester” that detects fluctuations in the contact's electrical resistance. Chatter tests were performed over a range of excitation amplitudes and frequencies, and high speed video from the tests suggested that “bouncing” (i.e. loss of contact) was the primary physical mechanism causing chatter. Structural dynamics models were then developed of the pin, receptacle, and contact pair, and corresponding modal experiments were performed for comparison and model validation. Finally, a high-fidelity solid mechanics model of the contact pair was developed to study the bouncing physics observed in the high speed videos. Chatter event statistics (e.g. mean chatter event duration) were used to compare the chatter behavior recorded during testing to the behavior simulated in the high-fidelity model, and this comparison suggested that the same bouncing mechanism is the cause of chatter in both scenarios.