Abstract The low cycle fatigue and low cycle fatigue-creep behaviours of P92 steel with strain-control mode and fully inverse loading waveforms at the temperature of 630 °C were investigated. A typical cyclic softening behaviour of P92 steel was observed. As the hold time was introduced at the tensile peak and compressive valley strains, the failure cycle was reduced and the stress reduction became more obvious with the increasing hold time because of the improvement in creep deformation. Moreover, a modified combined kinematic and isotropic hardening model by introducing a non-linear interaction damage accumulation constitutive model was proposed to capture the loop stress-strain behaviour until fracture and predict the failure life as the applied strain amplitudes and duration periods changed. The validation results showed that the accelerated cyclic softening and the greatly reduced failure cycle as the duration periods prolonged under the low cycle fatigue-creep interaction conditions were well described by the modified model.
Last. Hongyang Jing(TJU: Tianjin University)H-Index: 25
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Abstract The creep properties of the P92 steel were evaluated by small punch creep (SPC) tests and uniaxial creep (UC) tests. In addition, finite element (FE) methods using different creep damage models were adopted to analyze the variation of creep damage and deformation process for SPC tests, and the validity of FE methods was confirmed by the comparison of experimental deformation and damage accumulation. The rupture time, fracture positions and crack growth behaviors were dependent on the cr...
Abstract Based on existing lifetime and damage models a new approach is developed for the assessment of creep-fatigue lifetime of components made out of cyclic softening steel, in particular EUROFER97. For the application of the new creep-fatigue rules among others lifetime data from special tests, in particular creep tests on pre-fatigued specimens are required. Therefore, a test matrix is proposed and conducted for EUROFER97 in which the efforts are minimized by utilizing the Monkman-Grant rel...
Last. Jianbo Yu(SHU: Shanghai University)H-Index: 11
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Abstract Total strain-controlled creep-fatigue tests were performed for a directionally solidified Ni-based superalloy at 850 °C in air. Dwell times of 0, 1, 2, 3, 5, and 8 min were introduced at the tensile peak for each cycle. The results demonstrated that the fatigue life firstly decreased and then slightly increased with increasing dwell time. The fatigue life showed a minimum at a dwell time of 3 min. The initial softening rate was faster than the subsequent softening rate when dwell times ...
Last. Chun-Lin Wang(Ministry of Education)H-Index: 11
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AbstractAluminum has been increasingly used in space, building, and other structures owing to its light weight and high durability. The cyclic plasticity of aluminum is of great importance for the ...
Last. Yong Jiang(Nanjing Tech University)H-Index: 9
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Low cycle fatigue (LCF) and creep fatigue interaction (CFI) behaviour of P92 steel welded joint were investigated experimentally and numerically. Strain-controlled LCF tests at different strain amplitudes and CFI tests at different peak strain holding time were conducted. Evolutions of cyclic stress response, mean stress, and creep strain during cycling were described, in which the influence of strain amplitude and holding time were investigated. A specific heat treatment process was proposed to...
Last. Wei Sun(University of Nottingham)H-Index: 31
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Abstract This paper presents an elasto-viscoplastic finite element modelling framework including the associated UMAT codes to investigate the high-temperature behaviour of a gas turbine rotor steel. The model used in the FE study is an improved and unified Chaboche–Lemaitre model which combines a power flow rule with non-linear anisothermal evolution of isotropic and kinematic hardening. The computational methodology is a three-dimensional framework following an implicit formulation and based on...
#1Ulrich Führer(KIT: Karlsruhe Institute of Technology)H-Index: 2
#2Jarir Aktaa(KIT: Karlsruhe Institute of Technology)H-Index: 25
Abstract Ferritic-martensitic (F/M) steels are a common choice for high-pressure, high-temperature boilers and steam piping in power plants, but cyclic softening without saturation is a major degradation mechanism of F/M steels. This degradation mechanism is more pronounced and complex under creep-fatigue loadings. For reliable, but not overly conservative design a better understanding of this phenomenon is necessary. The intent of this work is to characterize and model the softening and lifetim...
In this paper strain ratcheting in cold expanded flat plate of Al-alloy 2024-T3 in double shear lap joints was studied both experimentally and numerically. In the experimental part, two types of symmetric strain-controlled and asymmetric stress-controlled cyclic tests were performed. Also, the cold expanded double shear lap joints subjected to cyclic stress-controlled tests. The required parameters for simulating the cyclic plastic behaviour of Al-alloy 2024-T3 were obtained on the basis of the ...
#1Dan Liu(Cant.: University of Canterbury)H-Index: 4
#2Dirk J. Pons(Cant.: University of Canterbury)H-Index: 16
Background Creep and fatigue damages in metals are known to interact and then lead to aggregated damage. While models exist for fatigue, creep and creep-fatigue, no models cover all 3 load regimes. Also, a heat treatment–related parameter is not well included in most creep-fatigue models. Need There is a need to develop a creep-fatigue equation, which covers the full loading regime from pure fatigue to pure creep, and creep-fatigue. Also needed is inclusion of a heat treatment–related parameter....
#1J. Veerababu(RRC: Indira Gandhi Centre for Atomic Research)H-Index: 5
#2Sunil Goyal(RRC: Indira Gandhi Centre for Atomic Research)H-Index: 15
Last. K. Laha(RRC: Indira Gandhi Centre for Atomic Research)H-Index: 21
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Abstract In the present study, low cycle fatigue (LCF) behaviour of tungsten (W) alloyed 9Cr steel (Grade 92 steel) base metal and its weld joints has been investigated. LCF tests on both base metal and weld joint were conducted under fully reversed, total axial strain control mode employing a triangular waveform at 823 K, under a constant strain rate of 3 × 10−3 s−1 with strain amplitudes varying from ±0.25% to ±1%. Both base metal and weld joint exhibited continuous softening with the weld joi...
Abstract Finite element simulations of the temperature-dependent stress-strain response in the elastoplastic region of a material usually involve incremental procedures based on the Newton–Raphson iterative scheme. Although essential to obtaining the correct result, iterations inherently extend the computational time of the simulations. In order to increase the computational effectiveness of such finite element simulations, a novel solution technique is presented here, which introduces a closed-...
Last. Peter K. Liaw(UT: University of Tennessee)H-Index: 94
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Abstract High total strain-controlled creep-fatigue tests of 1.8% were performed for a directionally-solidified Ni-based superalloy, DZ445, at 900 °C in air. Dwell times of 0, 2, and 5 min. were introduced at the tensile peak strain for each cycle. Experimental results show a decrease in fatigue life with increasing dwell time. The significant cyclic softening is observed after the application of the dwell time. The mean compressive stress and large plastic-strain accumulation are produced due t...
Last. Jiewei Lin(TJU: Tianjin University)H-Index: 8
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Abstract The crack growth behavior of Hastelloy X under creep-fatigue interaction at high temperature is investigated by a nonlinear creep-fatigue interaction damage model. Multiaxial stress is considered both in the fatigue and creep damage models. The effect of the variance of fatigue damage parameters is analyzed in a quantitative method and some linear effects were observed. The influence of hold time, crack depth ratio and load level on the crack growth behavior are studied and results unde...
#1Jianfeng Mao(Zhejiang University of Technology)H-Index: 10
#2Xiangyang Li(Zhejiang University of Technology)H-Index: 2
Last. Zhenyu Ding(Zhejiang University of Technology)H-Index: 5
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Abstract In this paper, the creep fatigue test at 550–650 °C of P92 steel is carried out, which not only reveals the damage evolution mechanism, but also analyzed the creep fatigue behaviors. The influence of temperature, load holding time and pre-fatigue damage on the creep fatigue behavior of P92 steel was studied in detail. The effects of the temperature and holding time on the hysteresis loops of stress–strain are evaluated quantitatively. Actually, the load holding time mainly affects the s...