Analytical solution of isothermal fatigue crack growth in solid cylinder

Abstract

Nowadays many industries deal with components which are subjected to high loads at elevated temperatures than before due to the increasing requirements regarding weight and performance. The simplest process to check the behaviour of the material at high temperature is the isothermal fatigue (IF), by designing a fatigue cycle at constant and uniform temperature to estimate stress-strain required to predict fatigue life of the material. Generally it is assumed that the maximum temperature in the loading cycle represents the most damaging condition likely to be experienced during service life of the component. An empirical IF model for solid cylinder subjected to constant temperature superimposed with sinusoidal mechanical load applied at different stress levels is being proposed. Linear equations are developed to describe the severity of the temperature gradient, thermal stresses, and stress and strain intensity factors through the solid cylinder wall as function of time. Results show the effect of temperature can be explained as increase in von Mises thermal stress increase as a function of increasing temperature. The highest stress at 400 °C recorded is due to inherent hardness increase of the material indicated by high modulus of elasticity. The mechanical stress is more effective than thermal loading and results show that the stress intensity factor decreases with temperature, except at 400 °C (due to hardness increase).