Influence of Strain Rate and Waveshape on Environmentally-Assisted Cracking during Low-Cycle Fatigue of a 304L Austenitic Stainless Steel in a PWR Water Environment

Abstract

In this paper, the low cycle fatigue resistance of a 304L austenitic stainless steel in a simulated pressurized water reactor (PWR) primary water environment has been investigated by paying a special attention to the interplay between environmentally-assisted cracking mechanisms, strain rate, and loading waveshape. More precisely, one of the prime interests of this research work is related to the consideration of complex waveshape signals that are more representative of solicitations encountered by real components. A detailed analysis of stress-strain relation, surface damage, and crack growth provides a preliminary ranking of the severity of complex, variable strain rate signals with respect to triangular, constant strain-rate signals associated with environmental effects in air or in PWR water. Furthermore, as the fatigue lives in PWR water environment are mainly controlled by crack propagation, the crack growth rates derived from striation spacing measurement and estimated from interrupted tests have been carefully examined and analyzed using the strain intensity factor range ΔKε. It is confirmed that the most severe signal with regards to fatigue life also induces the highest crack growth enhancement. Additionally two characteristic parameters, namely a threshold strain εth* and a time T*, corresponding to the duration of the effective exposure of the open cracks to PWR environment have been introduced. It is shown that the T* parameter properly accounts for the differences in environmentally-assisted growth rates as a function of waveshape.

Influence of mean stress and pressurized water reactor environment on the fatigue behavior of a 304L austenitic stainless steel

“…The fitting curves presented in Figure 8F were obtained by integrating the fatigue crack growth rates described by a Paris–Erdogan‐type equation 29 expressed as a function of the strain intensity factor range Δ K ε (Equation 4). The use of this parameter was proposed by Kamaya and Kawakubo 30,31 for austenitic stainless steels and was used in previous research of the same material in similar test conditions 10,32,33 …”

Metal Plasticity and Fatigue at High Temperature

“…As a part of this Special Issue, researchers were invited to submit their innovative research papers aimed at providing a state-of-the-art knowledge on the topic of metal plasticity, creep deformation and fatigue strength of metals operating at high temperatures, with emphasis on both experimental characterization and numerical modeling of material behavior. A total of eleven research papers were published [1][2][3][4][5][6][7][8][9][10][11].…”

“…Poulain et al [4] examine the dependence and interaction between the effect of pressurized water reactors environment, strain rate and shape of loading waveform on the LCF resistance of a 304L steel in terms of stress-strain response, crack growth, fatigue life and fracture surfaces morphology.…”

“…Papers in this Special Issue addressed different types of material, from stainless steel studied by [1,2,4,10], to aluminum alloys investigated by [3,6,9], Ni-based supper alloy in [8], spheroidal graphite iron by [7], and copper alloy discussed in [11].…”

“…The developed constitutive methods have, in most cases, been compared to experimental data obtained with tensile tests [3], fatigue tests [3,4,8], TMF tests [6,7], creep tests [2], and stress relaxation, aging tests presented in [9].…”