پياده سازي آسيب خستگي كم چرخه با كار سختي همسان و سينماتيكي

چكيده انگليسي :

73 Implementation of Low Cycle Fatigue Damage with Isotropic and Kinematic Hardening Negar Akbarian Dehkordi n akbareiandehkordi@me iut ac ir 21th January 2013 Department of Mechanical Engineering Abstract Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisors Mohammad Mashayekhi mashayekhi@cc iut ac ir Abstract Internal damage can caused due to the presence and development of microscopic cracks and cavities that eventually cause to part fracture For most metallic materials the damage behavior is a combination of brittle and ductile response and contribution of each mode is to a significant extent dependent on the temperature and loading rate One of the most important mode of material deterioration in metal is fatigue damage It is observed in mechanical components subjected to a large number of load and or temperature cycles Low cycle fatigue failures may occure when stractures are subjected to heavy cyclic loadings which induce irreversible strains on small or large scale giving rise to damage up crack initiation and propagation Generally in low cycle fatigue the number of cycles to rupture is low lower than 104 cycles The main objective of this study is to evaluation of low cycle fatigue damage under cyclic loading An elastic plastic damage coupled constitutive model is implemented in ABAQUS via its user subroutine UMAT This model is applied to low cycle fatigue problems In low cycle fatigue damage exists the plastic deformation in material Damage mechanics models based on continuum damage mechanics CDM are the most useful tools in evaluation of fatigue behavior in ductile material The metallic plasticity models exhibiting nonlinear isotropic hardening nonlinear kinematic hardening Chaboche Marquis model and ductile damage Lemaitre Chaboche model is studied in detail under isothermal and small strain conditions The nonlinear kinematic hardening model originally due to Armstrong and Frederick has proven powerful in modelling cyclic plasticity for metals Continuum Damage Mechanisms which represents a local approach to failure is one of the most promising tools used to predict macro crack initiation and propagation In this study the coupled approach is used to solve the nonlinear equations The material behavior is modeled by constitutive equations taking into account its progressive deterioration The microscopic deterioration of a representative volume element is modelled by a continuous in space and time variable defined at macro scale and referred to as the damage variable The ultimate phase of the damage evolution is detected by a local criterion and corresponds to the failure of the representative volume element and hence to a macro crack initiation The spatial evolution of the completely damaged zone corresponds to the propagation of the macro crack The evaluate the accuracy of the subroutine the results are compared with the references The results of low cycle fatigue life prediction of a gas valve membrane and fracture location are in a good agreement with experimental Key Words damage mechanics low cycle fatigue life prediction cyclic loadingPDF created with pdfFactory trial version www pdffactory com

اكبريان، نگار

پياده سازي آسيب خستگي كم چرخه با كار سختي همسان و سينماتيكي

تخمين عمر