New energy-based low cycle fatigue model for reactor steels

Fekete, Balázs

doi:10.1016/j.matdes.2015.04.039

Cited by 18 publications

(12 citation statements)

References 30 publications

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“…The plastic strain energy of a fatigue cycle is defined by the area bounded by the hysteresis loop in the cyclic stress-strain curve [31], as illustrated in Figure 2.1. The plastic strain energy can be calculated by simply integrating the stress-strain plot.…”

Section: Wf=wpmentioning

confidence: 99%

3D-FE Modeling of 316 SS under Strain-Controlled Fatigue Loading and CFD Simulation of PWR Surge Line

Mohanty

Barua

Listwan

et al. 2017

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In financial year 2017, we are focusing on developing a mechanistic fatigue model of surge line pipes for pressurized water reactors (PWRs). To that end, we plan to perform the following tasks: (1) conduct stress-and strain-controlled fatigue testing of surge-line base metal such as 316 stainless steel (SS) under constant, variable, and random fatigue loading, (2) develop cyclic plasticity material models of 316 SS, (3) develop one-dimensional (1D) analytical or closed-form model to validate the material models and to understand the mechanics associated with 316 SS cyclic hardening and/or softening, (4) develop three-dimensional (3D) finite element (FE) models with implementation of evolutionary cyclic plasticity, and (5) develop computational fluid dynamics (CFD) model for thermal stratification, thermal-mechanical stress, and fatigue of example reactor components, such as a PWR surge line under plant heat-up, cooldown, and normal operation with/without grid-load-following. This semi-annual progress report presents the work completed on the above tasks for a 316 SS laboratory-scale specimen subjected to strain-controlled cyclic loading with constant, variable, and random amplitude. This is the first time that the accurate 3D-FE modeling of the specimen for its entire fatigue life, including the hardening and softening behavior, has been achieved. We anticipate that this work will pave the way for the development of a fully mechanistic-computer model that can be used for fatigue evaluation of safety-critical metallic components, which are traditionally evaluated by heavy reliance on time-consuming and costly test-based approaches. This basic research will not only help the nuclear reactor industry for fatigue evaluation of reactor components in a cost effective and less time-consuming way, but will also help other safety-related industries, such as aerospace, which is heavily dependent on test-based approaches, where a single full-scale fatigue test can cost millions of dollars and require years of effort to conduct. Toward our goal of demonstration of fully mechanistic fatigue evaluation of reactor components, we also started work on developing a component-level computer model of reactor components, such as 316 SS surge line pipe. This requires developing a thermal-mechanical stress analysis model of the reactor surge line, which, in turn, requires time-dependent temperature and stratification information along the boundary of the pipe. Toward that goal, CFD models of surge lines are being developed. In this report, we also present some preliminary results showing the temperature conditions along the surge line wall under reactor heat-up, cooldown, and steady-state power operation.

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Section: Wf=wpmentioning

confidence: 99%

3D-FE Modeling of 316 SS under Strain-Controlled Fatigue Loading and CFD Simulation of PWR Surge Line

Mohanty

Barua

Listwan

et al. 2017

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“…Many experimental results show that the hysteresis energy has a power law relationship with the failure life in fatigue tests:

Δ ω_{p} \cdot {(N_{f})}^{β} = C

where Δω p is the plastic strain energy density defined as the area of the stress–strain curve. It can be determined as follows if a material satisfies the Masing's hypothesis:

Δ ω_{p} = \frac{1 - n'}{1 + n'} Δ σ \cdot Δ ε_{p l}

where Δ σ is the stress range of the stabilized (half‐life) cycle and n ′ is the cyclic strain hardening exponent, and it is described by Ramberg–Osgood relationship for the cyclic stress–strain behaviour:

\frac{Δ ε_{p l}}{2} = {(\frac{Δ σ}{2 K})}^{\frac{1}{n'}}

in which Δ ε pl is the plastic strain range, Δ σ is the stress range and K the is cyclic strength coefficient.…”

Section: A New Model Based On the Energy Methodsmentioning

confidence: 99%

“…Many experimental results show that the hysteresis energy has a power law relationship with the failure life in fatigue tests [21][22][23] :…”

Section: A N E W M O D E L B a S E D O N T H E E N E R G Y M E T H O Dmentioning

confidence: 99%

A new energy‐based method to evaluate low‐cycle fatigue damage of AISI H11 at elevated temperature

Luo

Wang

et al. 2017

Fatigue Fract Eng Mat Struct

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AISI H11 (X38CrMoV5‐1) hot‐work tool steel is widely used for making extrusion tools because of its good mechanical properties at high temperature and moderate cost. To predict its lifetime, an energy conservation‐based model was proposed in this paper by introducing the damage rate, which is expressed as the product of damage force and plastic strain rate. The strain‐controlled low‐cycle fatigue tests were conducted to obtain the parameters of the proposed model, while the stress‐controlled low‐cycle fatigue tests were used to validate the proposed model. The results demonstrate that the proposed model is accurate and reliable. Furthermore, the local misorientation was investigated by electron backscatter diffraction to analyse the correlation between the microstructure evolution and the cyclic behaviour, and crack propagation behaviour was identified.

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“…A unified design methodology, applicable to high-cycle fatigue and low-cycle fatigue, was recently proposed by Pei and Dong [21] and Pei et al [22], suggesting the use of an equivalent structural strain parameter (∆E) in combination with a master ∆E − N curve for assessing the fatigue life of a structural component. Alternatively, an energy-based approach has also been proposed for low-cycle fatigue, that relates the dissipated energy per load cycle to the number of cycles to failure [23,24].…”

Section: Introductionmentioning

confidence: 99%

Ultra low-cycle fatigue performance of S420 and S700 steel welded tubular X-joints

Chatziioannou

Karamanos

Huang

2019

International Journal of Fatigue

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The present study is motivated by the need for improving the fatigue performance of offshore wind energy structural systems. In particular, the ultra low-cycle fatigue performance of welded tubular X-joints is examined, motivated by the need of safeguarding the integrity of offshore platforms under extreme loading conditions. The welded specimens are manufactured using hot-rolled tubes of steel grade S420 and S700, and represent X-brace joints of a bottom-fixed offshore wind tubular jacket, with scaling factor of 1:3. Seven specimens are tested under strong fully-reversed cyclic in-plane bending, leading to through-thickness fatigue cracking within less than 100 cycles, simulating extreme loading conditions. The experimental results indicate that X-joints manufactured from both steel grades exhibit similar structural response, in terms of ultra low-cycle fatigue. Rigorous finite element models are also developed, with emphasis on constitutive modeling, to simulate the cyclic loading procedure, providing very good comparisons in terms of load-displacement response and local strain predictions during the initial loading cycles. The experimental data are compared with a large dataset of low-cycle fatigue experiments on welded components, reported in the literature for mild and high-strength steel materials, as well as with existing design provisions. The results indicate similar performance of high-strength steel and mild steel welded connections, and are compared with stress-based and strain-based design methodologies in predicting the number of cycles to failure in the ultra low-cycle fatigue regime.

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New energy-based low cycle fatigue model for reactor steels

Cited by 18 publications

References 30 publications

3D-FE Modeling of 316 SS under Strain-Controlled Fatigue Loading and CFD Simulation of PWR Surge Line

3D-FE Modeling of 316 SS under Strain-Controlled Fatigue Loading and CFD Simulation of PWR Surge Line

A new energy‐based method to evaluate low‐cycle fatigue damage of AISI H11 at elevated temperature

Ultra low-cycle fatigue performance of S420 and S700 steel welded tubular X-joints

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