The frequency role on cyclic damage: Reflection on electronic materials/devices

Frequency effects in fatigue as related to structural reliability of electronic materials/devices still remain a long term goal. Here, complexities arise by realizing that more than a single time dependent micromechanism might dominate. To achieve some progress, intensive experimental activities were conducted in different crystal - structures and in non-metallic systems. The study found that at least in metals. under isothermal conditions, the fatigue crack propagation rate (FCPR) actually increased as the frequency decreased even without environmental interactions. These effects become substantial in materials in which the activation enthalpy for deformation exceeded values of about 0.5e.v, which accentuated at low temperatures. In metals, these issues are analyzed in the light of crack-tip dislocation-interaction model with emphasis to some proposed constitutive equations. Attempts for more realistic simulation techniques in metals, ceramics and polymers might give insights into the generic frequency effects in cyclic damage.