Crack and Void Healing in Metals

Abstract

Metals are known to degrade, or even worse, lose functionality during service [1, 2]. The major factors shortening the service life of these materials are internal defects, such as cracks and voids [3, 4]. These internal defects are very difficult to detect, and even more difficult to repair [5–7]. During service, they might coalesce into a major crack, leading to failure [8]. When damage defects are generated in materials, the internal energy of the material increases together with some entropy increment, that is, the system is in a metastable state of the thermodynamic equilibrium. If some energy is imported from the environment, the system can overcome the energy barrier and automatically evolve along the way of minimizing the total Gibbs free energy of the system, so that the defects could be self healed [9–11] and the material performance can be partially restored [12–14]. It is therefore essential to understand the evolution of defects so that the healing mechanisms can be understood and employed to achieve the desired specific engineering requirement. In this chapter, we will first discuss the details of the healing processes of cracks by finite element (FE) modeling. Next, void healing processes will be analyzed and some analytical solutions are presented. From the numerical and analytical analyses, the parameters controlling the rate of the healing processes are derived.