Impression Creep Workshop Agreement Activity

Abstract

Abstract Impression creep testing is now an established, small-scale testing technique in which the indentation rate of a rectangular indenter can be converted into an equivalent uniaxial creep strain rate. Its increasing use and practical application to power plants has led to a need for standardization. This paper reports on activity by six laboratories currently using the technique to produce a CEN Workshop Agreement covering this testing methodology. Consensus is being sought on the details of the test itself, both in the form of the original single step test and in the form of the more complex stepped stress test, which can provide data at multiple test conditions in the same specimen. Associated matters being addressed include the standardization of specimen and indenter sizes; a standard methodology for measuring the indentation rate and the creep strain rate, with an appropriate validity check; and an agreement on a pretest rig hysteresis check. A further activity will define a maximum indentation depth, supported by finite element analysis. The agreed impression creep test procedure will be used in an interlaboratory “Round Robin” exercise on selected materials.