M206 Dependence of Low-cycle Fatigue Behavior on Plastic Strain Amplitude in ECAPed Ferritic Stainless Steel

In February/March 2007, The NRC issued Regulatory Guide “RG1.207” and Argonne National Laboratory issued NUREG/CR-6909 that is now applicable in the US for evaluations of PWR environmental effects in fatigue analyses of new reactor components. In order to assess the conservativeness of the application of this NUREG report, Low Cycle Fatigue (LCF) tests were performed by AREVA NP on austenitic stainless steel specimens in a PWR environment. The selected material exhibits in air environment a fatigue behavior consistent with the ANL reference “air” mean curve, as published in NUREG/CR-6909. LCF tests in a PWR environment were performed at various strain amplitude levels (± 0.6% or ± 0.3%) for two loading conditions corresponding to a simple or to a complex strain rate history. The simple loading condition is a fully reverse triangle signal (for comparison purposes with tests performed by other laboratories with the same loading conditions) and the complex signal simulates the strain variation for an actual typical PWR thermal transient. In addition, two various surface finish conditions were tested: polished and ground. This paper presents the comparisons of penalty factors, as observed experimentally, with penalty factors evaluated using ANL formulations (considering the strain integral method for complex loading), and on the other, the comparison of the actual fatigue life of the specimen with the fatigue life predicted through the NUREG report application. For the two strain amplitudes of ± 0.6% and ± 0.3%, LCF tests results obtained on austenitic stainless steel specimens in PWR environment with triangle waveforms at constant low strain rates give “Fen” penalty factors close to those estimated using the ANL formulation (NUREG/6909). However, for the lower strain amplitude level and a triangle loading signal, the ANL formulation is pessimistic compared to the AREVA NP test results obtained for polished specimens. Finally, it was observed that constant amplitude LCF test results obtained on ground specimens under complex loading simulating an actual sequence of a cold and hot thermal shock exhibits lower combined environmental and surface finish effects when compared to the penalty factors estimated on the basis of the ANL formulations. It appears that the application of the NUREG/CR-6909 in conjunction with the Fen model proposed by ANL for austenitic stainless steel provides excessive margins, whereas the current ASME approach seems sufficient to cover significant environmental effects for representative loadings and surface finish conditions of reactor components.

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Neutron Diffraction Study of Low-Cycle Fatigue Behavior in an Austenitic–Ferritic Stainless Steel

Acta Metallurgica Sinica (English Letters) ◽

10.1007/s40195-015-0319-4 ◽

2015 ◽

Vol 28 (10) ◽

pp. 1247-1256

Author(s):

Ming-Wei Zhu ◽

Nan Jia ◽

Feng Shi ◽

Bjørn Clausen

Keyword(s):

Stainless Steel ◽

Neutron Diffraction ◽

Diffraction Study ◽

Ferritic Stainless Steel ◽

Low Cycle Fatigue ◽

Fatigue Behavior ◽

Neutron Diffraction Study ◽

Cycle Fatigue

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Dynamic Strain Aging during Low Cycle Fatigue Deformation in Prior Cold Worked 316L Stainless Steel

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.261-263.1129 ◽

2004 ◽

Vol 261-263 ◽

pp. 1129-1134

Author(s):

Seong Gu Hong ◽

Soon Bok Lee

Keyword(s):

Stainless Steel ◽

Plastic Strain ◽

Strain Aging ◽

Loading Condition ◽

316L Stainless Steel ◽

Low Cycle Fatigue ◽

Plastic Strain Amplitude ◽

Dynamic Strain ◽

Cycle Fatigue ◽

Cold Worked

Low cycle fatigue (LCF) tests were carried out in a wide temperature range (20°C-650°C)at strain rates of 1×10-4/s-1×10-2/s for 17% cold worked (CW) 316L stainless steel to investigate the conditions for the occurrence of dynamic strain aging (DSA) and its effects on material properties during LCF deformation. DSA introduced anomalous changes of LCF properties, and the DSA regime under LCF loading condition coincided with that in tensile loading condition. During LCF deformation, dynamic stain aging can be manifested in the forms of the occurrence of the plateau or the peak in the variation of cyclic peak stress with temperature, the negative temperature dependence of plastic strain amplitude or softening ratio, the negative strain rate sensitivity, and the negative strain rate dependence of plastic strain amplitude or softening ratio.

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Low-cycle fatigue behavior of extruded Al-7Zn-2Mg-1.5Cu-0.2Sc-0.1Zr alloy at room and low temperatures

MATEC Web of Conferences ◽

10.1051/matecconf/201816522001 ◽

2018 ◽

Vol 165 ◽

pp. 22001

Author(s):

Zhu Qingyan ◽

Chen Lijia ◽

Xu Chengji ◽

Che Xin ◽

Li Feng

Keyword(s):

Low Temperature ◽

Strain Amplitude ◽

Low Cycle Fatigue ◽

Fatigue Behavior ◽

Aging Treatment ◽

Cyclic Hardening ◽

Strain Ratio ◽

Plastic Strain Amplitude ◽

Total Strain ◽

Cycle Fatigue

Due to the low density and high specific strength, aluminum alloys have been considered for automotive and aerospace applications. The aluminum components usually service in the conditions of low temperature and dynamic loading. Therefore, the research on the low temperature fatigue performances of Al alloys has great significance. The lowcycle fatigue tests for the extruded Al-7Zn-2Mg-1.5Cu-0.2Sc-0.1Zr alloy subjected to solution plus aging treatment have been conducted at 25°C and -40°C, respectively. The strain ratio and cyclic frequency applied in the low-cycle fatigue test were -1 and 0.5Hz, respectively. The experimental results show that at 25°C, the alloy exhibits the cyclic hardening at the total strain amplitudes of 1.0% and 1.2%, and the cyclic stabilization at the total strain amplitudes of 0.4%, 0.6% and 0.8%. At -40°C, however, the cyclic stability is observed during whole fatigue deformation at the total strain amplitudes of 0.4%, 0.5%, 0.6%, 0.7% and 0.8%. The relationship between the elastic strain amplitude, plastic strain amplitude and reversals to failure can be described by Basquin and Coffin-Manson equations, respectively. In addition, the observation results of fatigue fracture surfaces reveal that the cracks initiate at the free surface of fatigue specimen and propagate in a transgranular mode.

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