Papers by Keyword: Cyclic Plasticity

Abstract: In the present paper, the Preisach model of hysteresis is extended to structural analysis of trusses damaged under cyclic loading in plastic range. Parameters for the Preisach model of cyclic plasticity are obtained from uniaxial loading experiment. Damage, as a consequence of micro cracks appearance due to alternating loading in plastic domain, is modeled using brittle elements according to Preisach procedure. Results of this research are compared with the already existing in the literature. In the paper examples of trusses under various cyclic loadings are presented.

Abstract: This paper describes fully implicit stress integration scheme for Yoshida’s 6th order yield function combined with Yoshida-Uemori kinematic hardening model and its consistent tangent matrix. Cutting plane method was employed for accurate integrations of stress and state variables appeared in Yoshida-Uemori model. In the present scheme, equivalent plastic strain, stress tensor and all the state variables are treated as independent variables in order to handle the 6th order yield function which is not the J2 yield function, and the equilibriums for each variables are solved for the stress integration. Subsequently, exact consistent tangent matrix which is necessary for implicit static finite element simulation was obtained. The proposed scheme was implemented into finite element code LS-DYNA and deep drawing process for aluminum alloy sheet was calculated. The earing appearance after drawing was compared with the experiment.

Abstract: A finite element procedure is implemented for the elastic-plastic analysis of carbon steels subjected to reciprocating fretting contacts. The nonlinear kinematic hardening rule based on Chaboche model is used to model the cyclic plastic behavior in fretting contacts. The results show that accumulation of plastic strains, i.e. ratchetting, may occur near the contact edge while elastic shakedown is likely to take place in substrate.

Abstract: This paper is focused on the correct description of stress-strain behavior of the R7T steel. An experimental study on the wheel steel specimens including uniaxial as well as multiaxial tests has been conducted. The main attention was paid to such effects as ratcheting and nonproportional hardening of the material. A cyclically stable behavior of the steel under higher amplitude loading was found. The MAKOC model, which is based on AbdelKarim-Ohno kinematic hardening rule and Calloch isotropic hardening rule, has been applied in subsequent finite element simulations. The numerical results show very good prediction of stress-strain behaviour of the wheel steel.

Abstract: Two homogeneization approaches are used in order predict the cyclic elastic-plastic behaviour of 316L(N) polycrystals, either

Abstract: For engineering structures subjected to cyclic load, fatigue failure normally occurs at geometrical discontinuities such as holes and notches. In aircraft structures, such locations may experience occasional severe loading that can cause appreciable local plastic deformation. This poses a significant challenge to fatigue life modelling. For such locations subjected to variable amplitude loading of a large number of cycles, the numerical analysis of fatigue life requires an accurate and robust model for cyclic plasticity, in order to reliably determine the stress and strain response. In this paper, we explore the potential of a nonlinear kinematic hardening model in improving fatigue life analysis. The work is motivated by the inability of an existing strain-life model to capture the difference in fatigue damages caused by an unclipped and clipped service load spectrum. Preliminary results show that the strain-life method based on the nonlinear kinematic hardening model was able to qualitatively demonstrate the trend in fatigue life for two critical locations analysed, and it was able to give much improved quantitative prediction for one location. Further work is under way to verify the model against more test data and to improve its capability in dealing with material cyclic softening or hardening behaviour.

Abstract: Fatigue testing was conducted on AZ31B-H24 magnesium alloy in strain-control condition. An unusual asymmetric shape of the hysteresis loop was the key feature of the cyclic behavior. A continuum-based cyclic plasticity model was developed to follow the asymmetric hardening behavior of wrought magnesium alloys. The proposed model was implemented in a UMAT subroutine to run with Abaqus/Standard. It was demonstrated that the UMAT was able to follow the cyclic hardening behavior of AZ31B under uniaxial loading. An energy-based damage parameter was proposed for estimating the fatigue crack initiation life. The developed UMAT along with the proposed damage parameter were used for fatigue modeling of an automotive substructure made of magnesium. It was shown that the proposed asymmetric model was more promising than a symmetric model.

Abstract: This contribution presents main results of experimental tests realized on smooth specimens made of ST52 steel under strain controlled uniaxial cyclic loading and compares these results with numerical simulations performed using a modified Chaboche model by finite element method. The effects of NonMasings behavior, memorization, cyclic hardening/softening and mean stress relaxation have been studied at room temperature. The experiments were realized on the reconstructed hydraulic fatigue testing machine INOVA 100 at the Laboratory of modern materials testing and defectoscopy of VŠB-TU Ostrava. Developed mixed hardening material model includes a memory surface stated in stress-space, which makes possible to significantly improve prediction of effects studied.

Abstract: The current paper reports the results of a numerical simulation and experiment of ratcheting behavior of pressurized straight pipe under reversed bending. A nonlinear isotropic/ kinematic (combined) hardening model is implemented into finite element program ANSYS by writing own user subroutine in FORTRAN language. The results of the numerical simulation is compared with experimental data. A reasonable agreement is noticed between the experimental and the numerical results for the ratcheting behavior of the pressurized straight pipe subjected to reversed bending.

Abstract: The paper compares numerical simulation with experimental results of pressurized elbow piping subjected to reversed in-plane bending in elastoplastic domain. The modified AbdelKarim-Ohno model is implemented into finite element program ANSYS by writing own user subroutine in FORTRAN language. The modified AbdelKarim-Ohno model may improve the prediction accuracy of ratcheting behavior of pressurized elbow under cyclic loading.