The Experts below are selected from a list of 10527 Experts worldwide ranked by ideXlab platform
Deguang Shang - One of the best experts on this subject based on the ideXlab platform.
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notch Stress strain estimation method based on Pseudo Stress correction under multiaxial thermo mechanical cyclic loading
International Journal of Solids and Structures, 2020Co-Authors: Deguang Shang, Long Xue, Lingwan Wang, Jin CuiAbstract:Abstract In this paper, a notch Stress correction method based on the structural yield surface is proposed, in which the actual Stress increment at the notch root can be obtained by multiplying two quantities, that is, the Pseudo Stress increment and the ratio of the slopes of the material and structural Stress-strain curves. In the proposed method, the influence of temperature on the notch Stress correction can be taken into account, and no iteration is required during the calculation process. Moreover, based on the proposed notch correction method and a unified viscoplastic constitutive model at high temperature condition, a notch Stress-strain estimation method is developed under multiaxial thermo-mechanical cyclic loading. In order to assess the prediction accuracy of the proposed method, the calculated results are correlated to those from thermal-structural non-linear finite element analysis under various proportional and non-proportional mechanical loadings at non-isothermal high temperature condition. The comparison between the calculated and analyzed results shows that the proposed method can precisely estimate the notch Stress and strain under multiaxial thermo-mechanical cyclic loading.
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new Pseudo Stress correction method for estimating local strains at notch under multiaxial cyclic loading
International Journal of Fatigue, 2017Co-Authors: Zhiqiang Tao, Deguang Shang, Yujuan SunAbstract:Abstract A notch correction method is proposed under multiaxial cyclic loading, in which the real Stress increments can be directly obtained by correcting the Pseudo Stress increments at the notch. Moreover, the proposed method does not inherently restrict the direction and magnitude of real backStress increment in the real Stress space. Additionally, on the basis of Kanazawa et al.’s model, the proposed method utilizes Pseudo notch strains in replacement of measured strains to take account of the additional hardening due to the non-proportionality of external loadings. Based on the proposed correction method integrated with constitutive equations using Garud’s hardening model, a notch Stress-strain estimation methodology is developed to calculate the local elastic-plastic Stress-strain responses at the notch area. The presented methodology does not require iteration. The applicability of the presented methodology was verified by the experimental data of TC21 titanium alloy notched tubular specimens in this study and SAE 1070 steel notched shaft specimens from the literature. The results showed that the calculated notch strains correlate well with the measured strains under proportional and non-proportional loadings.
Ali Fatemi - One of the best experts on this subject based on the ideXlab platform.
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multiaxial variable amplitude fatigue life analysis using the critical plane approach part ii notched specimen experiments and life estimations
International Journal of Fatigue, 2017Co-Authors: Nicholas R. Gates, Ali FatemiAbstract:Abstract While part I of this paper was focused on evaluating multiaxial variable amplitude fatigue life estimations for un-notched specimens, part II extends the same critical plane-based analysis procedures to situations involving notched specimens. In addition to the factors considered in the un-notched analyses, local Stress concentrations, Stress gradient effects, and changes in local Stress state must also be accounted for in the presence of a notch. This was accomplished in the current study by coupling the Theory of Critical Distances point method with a Pseudo Stress-based plasticity modeling technique. Then, a modified version of the Fatemi-Socie parameter was used to calculate fatigue damage, and changes in life estimation accuracy were studied with respect to the consideration of transient material deformation behavior, crack initiation definition, and damage summation rule. Results from the notched specimen analyses were also compared to those for un-notched specimens, and some discussion is provided. While the effect of transient deformation behavior and crack initiation definition were found to be relatively small for the loading histories used in this study, changing the critical damage sum at failure had a much greater impact on life estimations. Although some of the analysis procedures investigated were able to estimate nearly all fatigue lives within a factor of 3 of experimental results, several areas were identified where there is potential for even further improvements to be made. These include issues related to the accuracy of life estimation curves, damage calculation models, and/or the modeling of material deformation behavior.
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Notch deformation and Stress gradient effects in multiaxial fatigue
Theoretical and Applied Fracture Mechanics, 2016Co-Authors: Nicholas R. Gates, Ali FatemiAbstract:Abstract This paper investigates notch mechanics under multiaxial fatigue loading conditions with respect to notch Stress–strain estimation rules and Stress gradient effects. A Pseudo Stress-based plasticity modeling technique, incorporating a structural yield surface concept, was applied to predict local Stress distributions for a 2024-T3 aluminum alloy notched tubular specimen, as well as for two different AISI 1141 steel alloy notched shaft specimen geometries. Stress–strain predictions were generated for several nominal loading conditions and compared to nonlinear FEA solutions. Most predictions were found to be within ±15% error for loading levels relevant to typical fatigue loading applications. To evaluate Stress gradient models, fatigue life predictions were performed for each specimen geometry using Neuber’s rule with fatigue notch factor, as well as several different interpretations of Theory of Critical Distances (TCD) approaches. The effect of critical distance value on life predictions was also studied. The Fatemi–Socie critical plane damage parameter was used to calculate fatigue lives. While the TCD approaches were found to provide improved multiaxial fatigue data correlation when compared to fatigue notch factor, negligible differences between the different TCD approaches were observed. Life prediction trends were found to be consistent regardless of notch geometry and material, thus suggesting some generality of the findings.
Yujuan Sun - One of the best experts on this subject based on the ideXlab platform.
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new Pseudo Stress correction method for estimating local strains at notch under multiaxial cyclic loading
International Journal of Fatigue, 2017Co-Authors: Zhiqiang Tao, Deguang Shang, Yujuan SunAbstract:Abstract A notch correction method is proposed under multiaxial cyclic loading, in which the real Stress increments can be directly obtained by correcting the Pseudo Stress increments at the notch. Moreover, the proposed method does not inherently restrict the direction and magnitude of real backStress increment in the real Stress space. Additionally, on the basis of Kanazawa et al.’s model, the proposed method utilizes Pseudo notch strains in replacement of measured strains to take account of the additional hardening due to the non-proportionality of external loadings. Based on the proposed correction method integrated with constitutive equations using Garud’s hardening model, a notch Stress-strain estimation methodology is developed to calculate the local elastic-plastic Stress-strain responses at the notch area. The presented methodology does not require iteration. The applicability of the presented methodology was verified by the experimental data of TC21 titanium alloy notched tubular specimens in this study and SAE 1070 steel notched shaft specimens from the literature. The results showed that the calculated notch strains correlate well with the measured strains under proportional and non-proportional loadings.
B Atzori - One of the best experts on this subject based on the ideXlab platform.
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a simple and efficient reformulation of the classical manson coffin curve to predict lifetime under multiaxial fatigue loading part ii notches
Journal of Engineering Materials and Technology-transactions of The Asme, 2009Co-Authors: L Susmel, Giovanni Meneghetti, B AtzoriAbstract:The present study is concerned with the use of the modified Manson-Coffin curve method to estimate the lifetime of notched components subjected to multiaxial cyclic loading. The above criterion postulates that fatigue strength under complex loading paths can efficiently be evaluated in terms of maximum shear strain amplitude, provided that the reference Manson-Coffin curve used to predict the number of cycles to failure is defined by taking into account the actual degree ofmultiaxiality/nonproportionality of the Stress/ strain state damaging the assumed crack initiation site. The accuracy and reliability of the above fatigue life estimation technique was checked by considering about 300 experimental results taken from the literature. Such data were generated by testing notched cylindrical samples made of four different metallic materials and subjected to in-phase and out-of-phase biaxial nominal loading. The accuracy of our criterion in taking into account the presence of nonzero mean Stresses was also investigated in depth. To calculate the Stress/strain quantities needed for the in-field use of the modified Manson-Coffin curve method, notch root Stresses and strains were estimated by using not only the well-known analytical tool due to Kottgen et al. (1995, "Pseudo Stress and Pseudo Strain Based Approaches to Multiaxial Notch Analysis," Fatigue Fract. Eng. Mater. Struct., 18(9), pp. 981-1006) (applied along with the ratchetting plasticity model devised by Jiang and Sehitoglu (1996, "Modelling of Cyclic Ratchetting Plasticity, Part 1: Development and Constitutive Relations. Transactions of the ASME," ASME J. Appl. Mech., 63, pp. 720-725; 1996, "Modelling of Cyclic Ratchetting Plasticity, Part I: Development and Constitutive Relations," Trans. ASME J. Appl. Mech., 63, pp. 720-725)) but also by taking full advantage of the finite element method to perform some calibration analyses. The systematic use of our approach was seen to result in estimates falling within an error factor of about 3.
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a simple and efficient reformulation of the classical manson coffin curve to predict lifetime under multiaxial fatigue loading part ii notches
Journal of Engineering Materials and Technology-transactions of The Asme, 2009Co-Authors: L Susmel, Giovanni Meneghetti, B AtzoriAbstract:The present study is concerned with the use of the modified Manson-Coffin curve method to estimate the lifetime of notched components subjected to multiaxial cyclic loading. The above criterion postulates that fatigue strength under complex loading paths can efficiently be evaluated in terms of maximum shear strain amplitude, provided that the reference Manson-Coffin curve used to predict the number of cycles to failure is defined by taking into account the actual degree ofmultiaxiality/nonproportionality of the Stress/ strain state damaging the assumed crack initiation site. The accuracy and reliability of the above fatigue life estimation technique was checked by considering about 300 experimental results taken from the literature. Such data were generated by testing notched cylindrical samples made of four different metallic materials and subjected to in-phase and out-of-phase biaxial nominal loading. The accuracy of our criterion in taking into account the presence of nonzero mean Stresses was also investigated in depth. To calculate the Stress/strain quantities needed for the in-field use of the modified Manson-Coffin curve method, notch root Stresses and strains were estimated by using not only the well-known analytical tool due to Kottgen et al. (1995, "Pseudo Stress and Pseudo Strain Based Approaches to Multiaxial Notch Analysis," Fatigue Fract. Eng. Mater. Struct., 18(9), pp. 981-1006) (applied along with the ratchetting plasticity model devised by Jiang and Sehitoglu (1996, "Modelling of Cyclic Ratchetting Plasticity, Part 1: Development and Constitutive Relations. Transactions of the ASME," ASME J. Appl. Mech., 63, pp. 720-725; 1996, "Modelling of Cyclic Ratchetting Plasticity, Part I: Development and Constitutive Relations," Trans. ASME J. Appl. Mech., 63, pp. 720-725)) but also by taking full advantage of the finite element method to perform some calibration analyses. The systematic use of our approach was seen to result in estimates falling within an error factor of about 3.
Jin Cui - One of the best experts on this subject based on the ideXlab platform.
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notch Stress strain estimation method based on Pseudo Stress correction under multiaxial thermo mechanical cyclic loading
International Journal of Solids and Structures, 2020Co-Authors: Deguang Shang, Long Xue, Lingwan Wang, Jin CuiAbstract:Abstract In this paper, a notch Stress correction method based on the structural yield surface is proposed, in which the actual Stress increment at the notch root can be obtained by multiplying two quantities, that is, the Pseudo Stress increment and the ratio of the slopes of the material and structural Stress-strain curves. In the proposed method, the influence of temperature on the notch Stress correction can be taken into account, and no iteration is required during the calculation process. Moreover, based on the proposed notch correction method and a unified viscoplastic constitutive model at high temperature condition, a notch Stress-strain estimation method is developed under multiaxial thermo-mechanical cyclic loading. In order to assess the prediction accuracy of the proposed method, the calculated results are correlated to those from thermal-structural non-linear finite element analysis under various proportional and non-proportional mechanical loadings at non-isothermal high temperature condition. The comparison between the calculated and analyzed results shows that the proposed method can precisely estimate the notch Stress and strain under multiaxial thermo-mechanical cyclic loading.
