Low cycle fatigue analysis of temperature and frequency effects in eutectic solder alloy

Low cycle isothermal mechanical fatigue testing of a eutectic alloy 63Sn/37Pb was carried out in a systematic manner over a wide range of frequencies (10−4–1 Hz) and temperatures (−40 to 150°C) with the total strain set at different values (1–50%). The low cycle fatigue behavior of the eutectic solder was found to be strongly dependent on test temperature and frequency. If the Coffin–Manson model is used to describe such fatigue behavior, the fatigue exponent m and ductility coefficient C in the model are found to be a function of temperature and frequency rather than numerical constants. The plastic flow law was employed to explain the temperature and frequency dependence. The frequency-modified Coffin–Manson model was tried and found to be able to eliminate the frequency dependence of the numerical “constants” but not the temperature dependence. To have a full description of the temperature- and frequency-dependent fatigue behavior, a set of empirical formulae was derived based on the frequency-modified Coffin–Manson model.