Meaning
Permanent reduction in the mechanical force exerted by a spring contact occurs over time when subjected to repeated temperature changes or mechanical loads. This cyclic contact stress relaxation leads to a decrease in the pressure required to maintain a low-resistance electrical connection. Plastic deformation replaces elastic strain as the material undergoes internal structural changes.
High-temperature environments accelerate the process by allowing atoms to migrate within the metal lattice.
Thermal Influence
Heat acts as a primary catalyst for the loss of spring energy in copper alloys. Elevated temperatures lower the yield strength of the material.
Material Fatigue
Repeated expansion and contraction cycles cause the spring member to settle into a new neutral position with less stored energy. While initial designs account for static relaxation, cyclic contact stress relaxation introduces a dynamic variable that complicates end of life predictions for automotive or industrial sensors. The contact force may drop below the minimum threshold required to pierce through surface oxidation.
A connector rated for 100 grams of force might retain only 60 grams after 500 thermal cycles between extreme limits. Success depends on selecting materials with high thermal stability such as beryllium copper or specialized stainless steels.
Interface Stability
Maintaining a stable electrical path requires a minimum normal force to prevent micro-fretting. If the force decays measurably, the contact becomes susceptible to vibration-induced intermittency. Mechanical testing validates that the remaining force stays within the specified qualification limits.
