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Creep behavior of plasma sprayed NiCr and NiCrAl coating-based systems

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Acta Metallurgica Sinica(English Letters) 2011年第3期24卷 183-189页

作者： shan-tung tu Key Laboratory of Safety Science of Pressurized System Ministry of EducationEast China University of Science and Technology

The creep behavior of the plasma sprayed NiCr and NiCrA1 coating/Nickel alloy 690 substrate systems at 1033 K was investigated. Results showed that there was almost no difference in the creep lives between the NiCr and NiCrA1 coated specimens at a given stress level, since the contents of Cr used in the NiCr and NiCrA1 powders are almost same. The relationship between the minimum creep rate and the applied stress followed the well-known Norton＇s power law, εmin=Aσ^n, with the values of A=2.66×10^-16 MPa^-n·h^-1 and n=6.48. The relation between the applied stress and time to rupture of the coated specimens can be estimated by using Larson-Miller equation. The θ projection method can be used to accurately characterize the creep behavior of the coated specimens.

关键词： Creep Coating θ projection method Minimum creep strainrate

Creep crack growth in a Cr-Mo-V type steel: experimental observation and prediction

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Acta Metallurgica Sinica(English Letters) 2011年第2期24卷 81-91页

作者： shan-tung tu Key Laboratory of Safety Science of Pressurized System Ministry of Education School of Mechanical and Power Engineering East China University of Science and Technology

In this study, the creep crack growth （CCG） properties and fracture mechanism of a Cr-Mo-V steel at 566 C in compact tension （CT） specimens were investigated, and the CCG rate was predicted by using the NSW model. The results show that the CCG rate measured by CT specimens is much lower than that predicted by the NSW model under plane-strain state. This means that the NSW model prediction for the CCG rate of the steel is over-conservative. In addition, the CCG rate da/dt versus C measured by the experiments shows the piecewise linear relation on log-log scale instead of a single linear relation predicted by the NSW model. The main reasons for these results are that the actual creep fracture mechanism of the steel and the actual creep crack tip stress field in the CT specimens have not been fully captured in the NSW model. The experimental observation shows that the creep crack propagates in a discontinuous way （step by step） at meso-scale, and the cracks at micro-scale are usually formed by the growth and coalescence of voids on grain boundaries. The NSW model based on the creep ductility exhaustion approach may not correctly describe this creep fracture process. In addition, the opening stress and triaxial stress ahead of crack tips calculated by three-dimensional finite element method is lower than those predicted by the HRR stress field which is used in the NSW model under plane-strain state. The use of the high HRR stress field will cause high CCG rates. The change in the creep fracture mechanism at micro-scale in different ranges of C may cause the piecewise linear relation between the da/dt and C . Therefore, it is necessary to study the actual CCG mechanism in a wide range of C and the actual creep crack tip stress field to establish accurate CCG prediction models.

关键词： Creep crack growth Prediction NSW model Fracture mechanism Finite element method

Foreword for the special issue of the 7th China-Japan bilateral symposium on high temperature strength of materials

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Acta Metallurgica Sinica(English Letters) 2011年第2期24卷 I0001-I0002页

作者： shan-tung tu Yukio TAKAHASHI East China University of Science and Technology Central Research Institute of Electric Power Industry

The 7th China-Japan Bilateral Symposium on High Temperature Strength of Mate- rials was held at Dalian, China, during the period August 23-27, 2010. The symposium was co-organized by the High Temperature Strength and Materials Committee, the So- ciety of Materials, Chinese Mechanical Engineering Society and the Committee on High Temperature Strength of Materials, the Society of Materials Science Japan.

关键词： 7th China-Japan bilateral symposium on high temperature strength of materials lecture Japan friendship

Determination of multiaxial stress rupture criteria for creeping materials:A critical analysis of different approaches

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Journal of Materials Science & Technology 2023年第6期137卷 14-25页

作者： Kun Zhang Jian-Ping Tan Wei Sun Kamran Nikbin shan-tung tu Key Laboratory of Pressure Systems and Safety(Ministry of Education) School of Mechanical and Power EngineeringEast China University of Science and TechnologyShanghai200237China Department of Mechanical Materials and Manufacturing EngineeringUniversity of NottinghamNottinghamNG72RDUK Department of Mechanical Engineering Imperial College LondonLondonSW72AZUK

Materials in engineering applications are rarely *** reality,failures under multiaxial loading has been widely observed in engineering *** life prediction of a component under multiaxial stresses has long been a challenging issue,particularly for high temperature *** distinguish the mode of failure ranging from a maximum principal stress intergranular damage to von Mises effective stress rupture mode a multiaxial stress rupture criterion(MSRC)was originally proposed by Sdobyrev and then Hayhurst and Leckie(SHL MSRC).A multiaxial-factor,α,was developed as a result which was intended to be a material constant and differentiates the bias of the MSRC between maxi-mum principal stress and effective *** success of the SHL MSRC relies on accurately calibrating the value ofαto quantify the multiaxial response of the material/geometry *** find a more suitable approach for determining MSRC,the applicability of different methods are *** that the resulting analysis of the various approaches can be affected by the creep failure mechanism,princi-ples in the determination of MSRC with and without using continuum damage mechanics approaches are *** viability of uniaxial material parameters in correlating withαthrough the analysis of available data in literature is also *** is found that the increase of the uniaxial creep dam-age tolerance parameterλis accompanied bythe decreaseof theα-value,whichimplies thatthe creep ductility plays an important role in affecting the multiaxial rupture behavior of materials.

关键词： Multiaxial stress rupture criterion Creep failure mechanism Uniaxial parameter Creep damage tolerance parameter Continuum damage mechanics

Low-cycle fatigue life prediction of a polycrystalline nickel-base superalloy using crystal plasticity modelling approach

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Journal of Materials Science & Technology 2020年第3期38卷 28-38页

作者： Guang-Jian Yuan Xian-Cheng Zhang Bo Chen shan-tung tu Cheng-Cheng Zhang Key Laboratory of Pressure Systems and Safety Ministry of EducationSchool of Mechanical and Power EngineeringEast China University of Science and TechnologyShanghai 200237China The Institute for Advanced Manufacturing and Engineering Faculty of EngineeringEnvironment and ComputingCoventry UniversityCoventry CV65LZUK AECC Commercial Aircraft Engine Co.LTD Shanghai Engineering Research Center for Commercial Aircraft EngineShanghai 201108China

A crystal plasticity model is developed to predict the cyclic plasticity during the low-cycle fatigue of GH4169 *** plastic slip and energy dissipation as fatigue indicator parameters(FIPs)are used to predict fatigue crack initiation and the fatigue life until *** show that fatigue damage is most likely to initiate at triple points and grain boundaries where severe plastic slip and energy dissipation are *** predicted fatigue life until failure is within the scatter band of factor 2 when compared with experimental data for the total strain amplitudes ranging from 0.8%to 2.4%.Microscopically,the adjacent grain arrangements and their interactions account for the stress *** addition,different sets of grain orientations with the same total grain numbers of 150 were generated using the present *** show that different sets have significant influence on the distribution of stresses between each individual grain at the meso-scale,although little effect is found on the macroscopic length-scale.

关键词： Crystal plasticity Fatigue Finite element Life prediction Micro-mechanics Nickel-base superalloy

Effect of Stress Ratio on the Fatigue Crack Propagation Behavior of the Nickel-based GH4169 Alloy

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Acta Metallurgica Sinica(English Letters) 2017年第9期30卷 809-821页

作者： Shen Ye Jian-Guo Gong Xian-Cheng Zhang shan-tung tu Cheng-Cheng Zhang Key Laboratory of Pressure Systems and Safety Ministry of EducationSchool of Mechanical and Power EngineeringEast China University of Science and TechnologyMeilongRoad 130Xuhui DistrictShanghai 200237People'sRepublic of China AECC Commercial Aircraft Engine Co.LTD ShanghaiEngineering Research Center for Commercial Aircraft EngineShanghai 201108People's Republic of China

The fatigue crack growth behavior of the newly developed GH4169 nickel-based alloy at a maximum stress of 700 MPa and different stress ratios was investigated in the present work employing the specimens with a single micro- notch at a frequency of 129 Hz at room temperature. The results demonstrate a typical three-stage process of fatigue crack propagation processing from the microstructurally small crack （MSC） stage to the physically small crack （PSC） stage, and finally to the long crack stage. The crack growth rate in the MSC stage is relatively high, while the crack growth rate in the PSC stage is relatively low. A linear function of crack-tip reversible plastic zone size was proposed to predict the crack growth rate, indicating an adequate prediction solution.

关键词： Fatigue crack Crack growth rate Stress ratio Nickel-based alloy

Effects of Stress Level and Stress State on Creep Ductility:Evaluation of Different Models

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Journal of Materials Science & Technology 2016年第8期32卷 695-704页

作者： Jian-Feng Wen shan-tung tu Fu-Zhen Xuan Xue-Wei Zhang Xin-Lin Gao Key Laboratory of Pressure Systems and Safety (Ministry of Education) School of Mechanical and Power Engineering East China University of Science and Technology Department of Materials Science and Engineering Texas A&M UniversityCollege Station Department of Mechanical Engineering Southern Methodist University

The last few decades have witnessed an increasing emphasis on the development of strain-based ap- proach for predicting the creep life or damage of components operating at elevated temperatures. Creep ductility, as a key parameter in this approach, may vary with a number of factors including strain rate, state of stress, operating temperature, material microstructure, etc. The present paper, however, is focused on reviewing the state-of-the-art understanding of the effects of stress level and stress state on the creep ductility. Mechanisms involving the void growth and coalescence are presented to describe the role of stress level in the variation of uniaxial creep ductility. The prediction capacity of existing empirical duc- tility models is also assessed in light of uniaxial test data. On the other hand, a vast body of multiaxial creep test data, collected from open literature, is utilized to examine the influence of the state of stress on the creep ductility. Then, a variety of multiaxial ductility factor models are introduced and evaluated with the available experimental data. Finally, a brief discussion on the dependence of creep ductility on the stress triaxiality and Lode parameter, predicted by numerical methods, is provided.

关键词： Creep Creep ductility Multiaxial stress state Ductility exhaustion

A novel hole cold-expansion method and its effect on surface integrity of nickel-based superalloy

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Journal of Materials Science & Technology 2020年第24期59卷 129-137页

作者： XianCao Ping ZhangShuang Liu Xue-Lin Lei Run-Zi Wang Xian-Cheng Zhang shan-tung tu Key Laboratory of Pressure Systems and Safety Ministry of EducationSchool of Mechanical and Power EngineeringEast China University of Science and TechnologyShanghai 200237China

Preferred surface integrity around the hole wall is one of the key parameters to ensure the optimized performance of hole components for nickel-based *** novel hole cold expansion technique introduced in this work involves the laser texturing process(LTP)followed by the Hertz contact rotary expansion process(HCREP),where the cylindrical sleeve is the critical component connecting the abovementioned two *** purpose of LTP is to obtain the most optimized strengthened cylindrical sleeve surface,preparing for the following ***,the HCREP acts on the nickel-based hole components by the rotary extruding movements of the strengthened sleeve and conical mandrel *** compared to the as-received GH4169 material,the surface integrity characterization for the strengthened hole shows that a plastic deformation layer with finer grains,higher micro-hardness,deeper compressive residual stress(CRS)distribution and lower surface roughness is formed at the hole *** addition,transmission electron microscope(TEM)observations reveal the microstructure evolution mechanism in the strengthened *** refinement near the hole wall is regarded as the fundamental reason for improving the surface integrity,where the aggregated dislocations and recombined dislocation walls can be clearly observed.

关键词： Cold expansion process Laser texturing process Surface integrity Microstructure evolution

Microstructural Evolution, Mechanical Properties and Thermal Stability of Gradient Structured Pure Nickel

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Acta Metallurgica Sinica(English Letters) 2019年第8期32卷 951-960页

作者： Xiao Li Bo Guan Yun-Fei Jia Yun-Chang Xin Cheng-Cheng Zhang Xian-Cheng Zhang shan-tung tu Key Laboratory of Pressure Systems and Safety Ministry of EducationSchool of Mechanical and Power EngineeringEast China University of Science and TechnologyShanghai 200237China School of Materials Science and Engineering Chongqing UniversityChongqing 400044China AECC Commercial Aircraft Engine Co.LTD Shanghai Engineering Research Center for Commercial Aircraft EngineShanghai 20110&China

The microstructural evolution of pure nickel treated by deep rolling(DR)technique with different indent depths was investigated by means of optical microscopy and transmission electron *** surface roughness,hardness and residual stress distribution along the depth from surface were ***,the DR-treated sample was annealed at temperatures from 300 to 700℃for 2 *** results reveal that dislocation movements are the fundamental mechanisms of gradient grain refinement during the DR *** increasing indent depth of the DR,the gradient microhardness on the cross section of sample significantly increases,the maximum compressive residual stress decreases,and the affecting region of residual stress *** results of thermal stability depict that the microstructure can be stable as temperature up to 300℃,and the abnormal grain growth and annealing twins are observed at 600℃.

关键词： Deep rolling Pure nickel-Microstructural evolution Mechanical properties Thermal stability