THE FREQUENCY ROLE ON CYCLIC DAMAGE - REFLECTION ON ELECTRONIC MATERIALS DEVICES

Frequency effects in fatigue as related to structural reliability of e lectronic materials/devices still remain a long term goal. Here, compl exities arise by realizing that more than a single time dependent micr omechanism might dominate. To achieve some progress, intensive experim ental activities were conducted in different crystal - structures and in non-metallic systems. The study found that at least in metals, unde r isothermal conditions, the fatigue crack propagation rate (FCPR) act ually increased as the frequency decreased even without environmental interactions. These effects become substantial in materials in which t he activation enthalpy for deformation exceeded values of about 0.5e.v , which accentuated at low temperatures. In metals, these issues are a nalyzed in the light of crack-tip dislocation-interaction model with e mphasis to some proposed constitutive equations. Attempts for more rea listic simulation techniques in metals, ceramics and polymers might gi ve insights into the generic frequency effects in cyclic damage.