Volume 13, Issue 6 (November 1985)
Design and Use of a Load Monitoring Environmental Test Chamber for Stress Corrosion Testing
This paper gives the construction details and materials used to make an environmental test chamber for stress corrosion cracking tests in which the load on the specimen can be continuously monitored. The design is such that 1T, 0.75T, and 0.5T CT and WOL specimens can be tested in most environments up to pressures of 0.8 MPa (100 psig) and in the temperature range of 0 to 100°C. The apparatus can be used to measure the stress intensity K and the crack length in a test specimen at any time. Consequently crack growth rate as a function of applied stress intensity and the threshold stress intensity KIscc can be obtained. A conceptual compromise in the design stemmed from the requirement of (1) a highly rigid loading system to simulate a bolt load test, and (2) the inclusion of a reasonably sensitive, low rigidity load cell in the loading train. In order to optimize the design, the load cells manufactured at the Westinghouse R&D Center were carefully evaluated. It was concluded that conventional strain gages are sensitive to the local environment (temperature and humidity) and that considerable care is required to limit errors in long term measurements.