1. 4/29/2002, Monday Environment-Assisted Cracking Chapter 11

2. Environment Assisted Cracking Natural environment: Moist air, natural water, seawater No single fracture micro-mechanism that is characteristic of EAC

3. Stress Corrosion Cracking (SCC) Stress corrosion cracking (SCC) is the formation of brittle cracks in a normally sound material through the simultaneous action of a tensile stress and a corrosive environment.

4. Mechanical Chemistry The mechanics of growing cracks with their singular stress and strain fields is intermingled with the chemical action of adsorbing and diffusing chemical species.

5. Initial Stress Intensity Factor Grow to critical dimensions

6. Three Stages of SCC

7. Fracture Criterion No failure even after exposure under stress to aggressive environment Sub-critical crack growth with fracture occurring after a curtain loading period in an aggressive environment Immediate fracture

8. Hydrogen Embrittlement A seemingly small change in the environment can cause a large effect. AISI 4340 alloy steel + hydrogen gas AISI 4340 alloy steel + oxygen gas

9. Hydrogen Sources Steel casting: dissolved hydrogen in the molten metal Electroplating: cathodic charging Welding from electrode cover material or from residual water

10. Radiation Damage Monte Carlo Method