PSI - Issue 19

Masaru Bodai et al. / Procedia Structural Integrity 19 (2019) 64–72 Bodai,M et al. / Structural Integrity Procedia 27 (2019) 000 – 000

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2

Nomenclature

a ： C ：

Crack depth (mm)

Half of crack length (mm) da⁄dN ： Fatigue crack growth rate (m/cycle) E ： Young ’ s modulus (MPa) F m ： Membrane stress function F bg ： Bending stress function H ： Temperature function ∆ K ： Stress intensity factor range (MPa √ m) N ： Number of cycles N f ： Fatigue life N Through-wall ： Fatigue life at through-wall crack Q ： Flaw shape function R ： Stress ratio R 0 ： Radius of pipe (mm) T c ： Temperature ( ℃ ) t ： Thickness (mm) x ：

Distance through the wall from surface (mm)

ε a ： ε m ： σ ：

Strain amplitude (%)

Mean strain (%)

Stress (MPa) ∆ σ m ： Membrane stress range (MPa) ∆ σ bg ： Bending stress range (MPa) σ u ： Tensile strength (MPa) σ x ： Axial stress (MPa)

1. Introduction

The JSME S NC1 Codes for Nuclear Power Generation Facilities - Rules on Design and Construction for Nuclear Power Plants- (2016) (hereinafter, JSME Design & Construction Code) stipulates design fatigue curves that basically come from the ASME design fatigue curves of the 1983 Winter Addenda. On the other hand, NUREG/CR 6909 Rev.0 (2007) developed new design fatigue curves and the ASME B&PV Code Section III incorporated the design fatigue curve for austenitic stainless steels in NUREG/CR-6909 Rev.0 at 2009 addenda. The JSME Committee on Power Generation Facility Codes established Task Group on Fatigue Evaluation and this task group concluded the necessity of new design fatigue curves to obtain an accurate fatigue life. This task group was terminated and Subgroup on Fatigue Evaluation was established in 2017. This subgroup is developing new fatigue evaluation method including design fatigue curves (Asada et al., 2019). Also, the Design Fatigue Curve (DFC) subcommittee was established in the Atomic Energy Research Committee in the Japan Welding Engineering Society from August 2011 to March 2013 (Phase I) (Asada et al., 2013, 2015, 2018) and the DFC subcommittee Phase II was followed from April 2013 to March 2016. The DFC1 and DFC2 subcommittees have developed a new fatigue evaluation method and produced beneficial outcomes. To support this study, a Japanese utility project performed not only large scale fatigue tests using austenitic stainless steel piping and carbon and low-alloy steel flat plates (Bodai et al., 2018), (Takanashi et.al. 2018) but also fatigue tests using small specimens to obtain not only basic data but also fatigue data of mean stress effect and surface finishing effect (Wang et al., 2018). Those test results were provided to the DFC2 subcommittee and utilized the above studies. The previous paper (Bodai et al., 2018) reported the relation between the best-fit curve of austenitic stainless steels and the fatigue test data for the large scale piping (NPS 8, Schedule 160) of austenitic stainless steel. Also, the