A MODEL OF THE ENVIRONMENTALLY AFFECTED GROWTH OF FATIGUE CRACKS

The process of damage accumulation and crack growth under a combinatio n of cyclic loads and environmental effects (the so-called corrosion f atigue) are considered. The equilibrium and energy balance relations i n the ''solid with cracks-load'' system are supplemented by equations which describe the process of damage accumulation at the crack tips an d their continuation. In addition to a phenomenological measure of the microdamage of mechanical origin, parameters characterizing the chang e in the properties near the contact surface due to physicochemical fa ctors are introduced. The model takes into account the influence of ex tremal stresses of the cycle, the loading frequency and the parameters of the environment (such as the concentration of the corrosive agent or pH value), and the influence of the initial conditions on the rate of crack growth, the level of damage and the effective concentration r atio on the moving front, as well as the total time to fracture, measu red both in number of cycles and in units of time. The model gives a s atisfactory description of the behaviour of corrosion fatigue cracks. (C) 1998 Elsevier Science Ltd. All rights reserved.