Session: CS-17-02 EAF Testing Outcomes

Paper Number: 105889

105889 - Influence of Insensitive Strain Region for Strain Rate on Fatigue Life of Stainless Steel in Pwr Primary Water Environment 

It has been shown that the degree of fatigue life reduction due to the pressurized water reactor (PWR) environment depends on strain rate. It was reported that the strain rate had little influence when the strain was smaller than a threshold value, which was referred to as the insensitive region. This study aimed at revealing the insensitive region corresponds to the region when crack mouth was closed and crack mouth opened when the applied stress reached zero from negative value. The tests were conducted using cylindrical hollow specimens of Type 316 stainless steel. Some tests were conducted using the material with additional cold working of 20% by tensile tests. The strain rates were changed at pre-determined strain, at which the stress was deduced to be zero. The strain range of the tests were 1.2%. The test results revealed that the fatigue life was not affected by the strain rate at the insensitive strain region. The fatigue life was almost the same regardless of the strain rate at the insensitive region. Also, the insensitive strain region could be determined by the zero-stress assumption, in which the crack mouth opened when the stress reached zero. The results implied that the insensitive strain region corresponded to the crack mouth opening behavior. The threshold strain might be determined by assuming crack mouth opening at zero stress. The strain rate less than the during crack mouth closing had no influence on the fatigue life.

Presenting Author: Masayuki Kamaya Institute of Nuclear Safety System, Incorporated

Presenting Author Biography: Dr. Kamaya is research engineer working for Institute of Nuclear Safety System in Japan.
Also, he is visiting Professor of University of Fukui
Dr. Kamaya’s research covers fatigue, material strength, structural integrity and electron backscatter diffraction.
He has published more than 100 research papers in these fields.
He is chairman of working group on fatigue evaluation procedure of JSME (Japan Society of Mechanical Engineers).

Authors:

Masayuki Kamaya Institute of Nuclear Safety System, Incorporated