Development of a Kic Stress-Corrosion Test Specimen

摘要

A study was made to develop a KsubIC stress-corrosion test that would be suitable for investigating the phenomenon that the effective fracture toughness of certain materials may be reduced if a flaw in the material can extend by stress corrosion to a critical size. The results of the study indicate that by appropriate modification, the standard KsubIC slow-bend fracture-toughness test can be used to demonstrate the effect of stress corrosion on fracture toughness. The modification consists of notching the specimen face so that plane-strain fracture can be obtained in relatively small specimens of tough materials. The fatigue-cracked area is surrounded by the appropriate corrosive environment and the specimen is dead-weightloaded as a cantilever beam. Preliminary results on a 12Ni-5Cr-3Mo maraging steel (yield strength of about 175 ksi and Charpy V-notch energy absorption of about 35 ft-lb) have shown that this steel failed by plane-strain fracture at values ranging from 0.8 KIC at 10 hours to 0.3 KIC at 400 hours when the fatigue crack was exposed under stress to synthetic sea water. To date, similar failures have not been observed in the 5Ni-Cr-Mo-V experimental HY-130/150 steel after more than 500 hours in test. (Author)