DIN EN ISO 7539-6:2012-01

This part of ISO 7539 covers procedures for designing, preparing and using precracked specimens for investigating susceptibility to stress corrosion. Recommendations concerning notched specimens are given in Annex A. Because of the need to confine plasticity at the crack tip, precracked specimens are not suitable for the evaluation of thin products, such as sheet or wire; they are generally used for the evaluation of thicker products including plates, bars and forgings. They can also be used for parts joined by welding. Precracked specimens can be loaded with equipment for application of a constant load or can incorporate a device to produce a constant displacement at the loading points. Tests conducted under increasing displacement or increasing load shall be carried out in accordance with ISO 7539-9. A particular advantage of precracked specimens is that they allow data to be acquired from which critical defect sizes, above which stress corrosion cracking can occur, can be estimated for components of known geometry subjected to known stresses. They also enable rates of stress corrosion crack propagation to be determined. This data can be taken into account when monitoring parts containing defects during service. This document (EN ISO 7539-6:2011) has been prepared by ISO/TC 156 "Corrosion of metals and alloys", the secretariat of which is held by SAC (People's Republic of China) and has been adopted by CEN/TC 262 "Metallic and other inorganic coatings", the secretariat of which is held by CEN (United Kingdom). The responsible German standardization committee is NA 062-01-71 AA "Korrosion und Korrosionsschutz" ("Corrosion and corrosion protection") at the Materials Testing Standards Committee (NMP).