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Novel Ring Compression Test Method to Determine the Stress-Strain Relations and Mechanical Properties of Metallic Materials
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作者 Guangzhao Han lixun cai +4 位作者 Chen Bao Bo Liang Yang Lyu Maobo Huang Xiaokun Liu 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2021年第6期114-125,共12页
Although there are methods for testing the stress-strain relation and strength,which are the most fundamental and important properties of metallic materials,their application to small-volume materials and tube compone... Although there are methods for testing the stress-strain relation and strength,which are the most fundamental and important properties of metallic materials,their application to small-volume materials and tube components is lim-ited.In this study,based on energy density equivalence,a new dimensionless elastoplastic load-displacement model for compressed metal rings with isotropy and constitutive power law is proposed to describe the relations among the geometric dimensions,Hollomon law parameters,load,and displacement.Furthermore,a novel test method was developed to determine the elastic modulus,stress-strain relation,yield and tensile strength via ring compression test.The universality and accuracy of the method were verified within a wide range of imaginary materials using finite element analysis(FEA),and the results show that the stress-strain curves obtained by this method are consistent with those inputted in the FEA program.Additionally,a series of ring compression tests were performed for seven metallic materials.It was found that the stress-strain curves and mechanical properties predicted by the method agreed with the uniaxial tensile results.With its low material consumption,the ring compression test has the potential to be as an alternative to traditional tensile test when direct tension method is limited. 展开更多
关键词 Ring compression Energy density equivalence Stress-strain relation STRENGTH Metallic material
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Novel method for measuring surface residual stress using flat-ended cylindrical indentation
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作者 Guangzhao HAN lixun cai Xiaokun LIU 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2024年第8期486-495,共10页
Instrumented indentation is a promising technique for estimating surface residual stresses and mechanical properties in engineering components.The relative difference between the indentation loads for unstressed and s... Instrumented indentation is a promising technique for estimating surface residual stresses and mechanical properties in engineering components.The relative difference between the indentation loads for unstressed and stressed specimens was selected as the key parameter for measuring surface residual stresses in flat-ended cylindrical indentations.Based on the equivalent material method and finite element simulations,a dimensionless mapping model with six constants was established between the relative load difference,constitutive model parameters,and normalized residual stress.A novel method for measuring the surface residual stress and constitutive model parameters of metallic material through flat-ended cylindrical indentations was proposed using this model and a mechanical properties determination method.Numerical simulations were conducted using numerous elastoplastic materials with different residual stresses to verify the proposed model;good agreements were observed between the predicted residual stresses and those previously applied in finite element analysis.Flat-ended cylindrical indentation tests were performed on four metallic materials using cruciform specimens subjected to various equibiaxial stresses.The results exhibited good conformance between the stress–strain curves obtained using the proposed method and those from traditional tensile tests,and the absolute differences between the predicted residual stresses and applied stresses were within 40 MPa in most cases. 展开更多
关键词 Instrumented indentation Residual stress Finite element simulation Equivalent material method Mechanical property
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A Semi-analytical Model of Maximal First Principal Stress at Mode I Crack Tip
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作者 Simiao Yu lixun cai 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2024年第5期798-811,共14页
The first principal stress plays a key role in ductile fracture processes.Investigation of the distribution and evolution of the first principal stress at the crack tip is essential for exploring elastoplastic fractur... The first principal stress plays a key role in ductile fracture processes.Investigation of the distribution and evolution of the first principal stress at the crack tip is essential for exploring elastoplastic fracture behaviors.A semi-analytical model was developed in this study to determine the maximal first principal stress at the mode I crack tip with 3D constraints for materials following the Ramberg-Osgood law.The model,based on energy density equivalence and dimensional analysis,was validated through finite element analysis(FEA)of various materials and geometric dimensions of specimens with mode I cracks,under over 100 different types of working conditions.The dimensionless curves of maximal first principal stress versus load,as predicted by the model,agreed well with the FEA results,demonstrating the accuracy and applicability of the model.This research can provide a basis for future theoretical predictions of crack initiation and propagation. 展开更多
关键词 Mode I crack 3D constraints Ramberg-Osgood law Energy density equivalence First principal stress
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Semi-analytical model for flat indentation of metal materials and its applications 被引量:12
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作者 Xiaokun LIU lixun cai +1 位作者 Hui CHEN Shuqian SI 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2020年第12期3266-3277,共12页
The increasing use of small material components in a wide range of industrial fields necessitates the development of an accurate and robust indentation testing method.To this end,this paper proposes an Energy-density-... The increasing use of small material components in a wide range of industrial fields necessitates the development of an accurate and robust indentation testing method.To this end,this paper proposes an Energy-density-equivalence for a Flat Indentation(E-FI)model based on the energy density equivalent principle.The proposed model describes the relationships among the material parameters of Hollomon's power law(H-law),flat indenter diameter,energy,and indentation displacement.An E-FI Method(E-FIM)that determines the H-law parameters of materials through the indentation test is also developed.The energy-displacement curves forward-predicted by the E-FI model(based on known H-law parameters of materials)and the H-law parameters of materials given by the E-FIM(based on known energy-displacement curves)are consistent with the results of Finite Element Analysis(FEA)and the H-law parameters of materials used as the input for FEA,respectively.Using E-FIM,the goodness of fit for both stress–strain curves with H-law,predicted based on the displacement with 2%signal interference,and that for stress–strain curves without interference is more than 0.98.The stress–strain relations predicted by E-FIM were consistent with the results obtained via uniaxial tensile tests of ten ductile materials. 展开更多
关键词 Energy-density-equivalence Flat indentation Power-law material Semi-analytical model Stress–strain relationship
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Improved normalization method for ductile fracture toughness determination based on dimensionless load separation principle 被引量:11
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作者 Chen Bao lixun cai +2 位作者 Kaikai Shi Chen Dan Yao Yao 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2015年第2期168-181,共14页
This study successfully deals with the inhomogeneous dimension problem of load separation assumption, which is the theoretical basis of the normalization method. According to the dimensionless load separation principl... This study successfully deals with the inhomogeneous dimension problem of load separation assumption, which is the theoretical basis of the normalization method. According to the dimensionless load separation principle, the normalization method has been improved by intro- ducing a forcible blunting correction. With the improved normalization method, the J-resistance curves of five different metallic materials of CT and SEB specimens are estimated. The forcible blunting correction of initial crack size plays an important role in the J-resistance curve estima- tion, which is closely related to the strain hardening level of material. The higher level of strain hardening leads to a greater difference in JQ determined by different slopes of the blunting line. If the blunting line coefficient recommended by ASTM E1820-11 is used in the improved nor- realization method, it will lead to greater fracture resistance than that processed by the blunting line coefficient recommended by ISO 12135-2002. Therefore, the influence of the blunting line on the determination of JQ must be taken into full account in the fracture toughness assessment of metallic materials. 展开更多
关键词 dimensionless load separation improved normalization method dimension inho-mogeneous J-resistance curve forcible blunting correction
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Prediction of fatigue crack growth rate for smallsized CIET specimens based on low cycle fatigue properties 被引量:2
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作者 Chen BAO lixun cai Kaikai SHI 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2018年第4期740-748,共9页
Based on experiments of low cycle fatigue for 5083-H112 aluminum alloy, two energybased predictive models have been introduced to predict the fatigue crack growth behaviors of traditional Compact Tension(CT) and sma... Based on experiments of low cycle fatigue for 5083-H112 aluminum alloy, two energybased predictive models have been introduced to predict the fatigue crack growth behaviors of traditional Compact Tension(CT) and small-sized C-shaped Inside Edge-notched Tension(CIET)specimens with different thicknesses and load ratios. Different values of the effective stress ratio U are employed in the theoretical fatigue crack growth models to correct the effect of crack closure.Results indicate that the two predictive models show different capacities of predicting the fatigue crack growth behaviors of CIET and CT specimens with different thicknesses and load ratios.The accuracy of predicted results of the two models is strongly affected by the method for determination of the effective stress ratio U. Finally, the energy-based Shi&Cai model with crack closure correction by means of Newman's method is highly recommended in prediction of fatigue crack growth of CIET specimens via low cycle fatigue properties. 展开更多
关键词 CIET specimen Crack closure correction Energy-based fatigue crack growth predictive model Low cycle fatigue 5083-H112 aluminum alloy
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Theoretical model and testing method for ball indentation based on the proportional superposition of energy in pure elasticity and pure plasticity 被引量:2
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作者 Shuqian SI lixun cai +2 位作者 Hui CHEN Chen BAO Xiaokun LIU 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2022年第2期141-153,共13页
For a homogeneous,continuous,and isotropic material whose constitutive relationships meets with the Ramberg-Osgood law(R-O law),the energy in the elastoplastic indentation with a ball indenter was theoretically analyz... For a homogeneous,continuous,and isotropic material whose constitutive relationships meets with the Ramberg-Osgood law(R-O law),the energy in the elastoplastic indentation with a ball indenter was theoretically analyzed,and the proportional superposition of energy in pure elasticity and pure plasticity during indentation was considered based on the equivalence of energy density.Subsequently,a Proportional Superposition-based Elasto Plastic Model(PS-EPM)was developed to describe the relationships between the displacement and the load during the ball indentation.Furthermore,a new test method of Ball Indentation based on Elastoplastic Proportional Superposition(BI-EPS)was developed to obtain the constitutive relationships of R-O law materials.The load–displacement curves predicted using the PS-EPM model were found to agree closely with the Finite Element Analysis(FEA)results.Moreover,the stress vs.strain curves predicted using the BI-EPS method were in better agreement with those obtained by FEA.Additionally,ball indentation was performed on eleven types of metal materials including five types of aluminum alloys and six types of steel.The test results showed that the stress vs.strain relationships and the tensile strength values predicted using the proposed BI-EPS method agreed well with the results obtained using conventional uniaxial tensile tests. 展开更多
关键词 Ball indentation Energy density Proportional superposition of elasticity and plasticity Stress vs.strain relationships Testing method Theoretical model
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Residual stress indentation model based on material equivalence 被引量:2
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作者 Xiaokun LIU lixun cai Hui CHEN 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2022年第8期304-313,共10页
A novel residual stress indentation model for conical indentation loading is proposed to describe the relationship between the residual stress,material constitutive parameters,load,and displacement for materials with ... A novel residual stress indentation model for conical indentation loading is proposed to describe the relationship between the residual stress,material constitutive parameters,load,and displacement for materials with a uniaxial constitutive relationship that obeys Hollomon’s power law(H-law).The novel model was established based on the principle that the equivalent material without residual stress corresponds to the original material with residual stress,conical indentation theoretical model based on energy density equivalence,and an assumed power-law relationship between the dimensionless residual stress and relative difference of the yield stresses of the equivalent material and original material.Sixty imaginary H-law materials with ten equibiaxial and ten uniaxial residual stresses were investigated by Finite Element Analysis(FEA).The residual stresses predicted by the novel model from the indentation load–displacement curves simulated for the imaginary materials are in close agreement with those applied by the FEA.Finally,indentation tests for Cr12Mo V steel,45 steel,and 6061-T6511 aluminum alloy were carried out on their specimens without residual stress and their bending specimens with equibiaxial and uniaxial residual stresses.The residual stresses predicted by the novel model according to the indentation load–displacement test curves are in good agreement with those applied by the tests. 展开更多
关键词 Conical indentation Equivalent material Finite element analysis Residual stress Theoretical model
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Estimation of Fracture Toughness for A508-III Steel in Ductile-to-Brittle Transition Region Using a Strain-Energy–Density-Based Fracture Failure Model
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作者 Yuanjun Wu Chen Bao +2 位作者 lixun cai Kaiqing Wang Xiao Liu 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2022年第5期834-841,共8页
According to the assumption of intrinsic relationship between ultimate strain energy density and microcrack nucleation,this work developed a fracture failure model to estimate the fracture toughness of A508-III steel ... According to the assumption of intrinsic relationship between ultimate strain energy density and microcrack nucleation,this work developed a fracture failure model to estimate the fracture toughness of A508-III steel in the ductile-to-brittle transition region.The fracture toughness and uniaxial tension tests at different temperatures were carried out to determine the relationship between nucleation parameter and ultimate strain energy density,from which the evolutions of fracture toughness of A508-III ferritic steel for different cumulative failure probabilities at different temperatures were predicted.The fracture failure model can well describe the fracture toughness distribution of A508-III steel in the ductile-to-brittle transition region.Compared with the master curve method,this model has better temperature adaptability.It is more convenient to calibrate the parameters of this model compared with the traditional Beremin model,and without complex finite element analysis. 展开更多
关键词 Fracture toughness Cumulative failure probability A508-III steel Ductile-to-brittle transition region
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