What can be done about stress corrosion cracking?

Stress corrosion cracking involve a number of factors that are often overlooked. Among the major ones are tensile stress, material susceptibility and aggressive environment, the combination of which can lead to slow crack growth with velocities ranging from about 10(-3) to 10 mm/h. Eventually fast crack propagation can result that should be avoided. Past efforts have been spent mostly on mitigation methods at the macroscopic scale by application of the fracture mechanics discipline, in particular the parameter K-ISCC where the subscript SCC stand for stress corrosion cracking. It has been used as a threshold value for SCC below which the macro-crack damage is no longer detectable although micro- and nano-damage continue to prevail. Micrographs, however, show that cracks of the order of nanometers may not be the answer. Still smaller defects may have occurred owing to chemical effects, in particular chemical decomposition. It is thought that the interaction of temperature and time effects can influence the behavior of electrons. They are known to play an active role in the stress corrosion process. One of the least understood problems in material degradation is that due to stress corrosion associated with the generation of nuclear power, not to mention the added effect of irradiation. The US-China seminar selected this subject as a joint effort to study this area in more depth with the aid of high resolution microscopes and advances in quantum mechanics. It is withn this objective that this presentation has been made.