Metal Plasticitymi@se.ed.cn
Metal Plasticity
OutlineIntroduction（引言）·1D plasticity theory（一维塑性）·Roughvaluesofyieldstress（常用工程材料屈服应力值）·3Dplasticitytheory（三维塑性理论）·Decompositionof strain（应变分解）·Yield criterion（屈服判据）·Yield surface（屈服面）·Isotropic strainhardening（各向同性强化）·Kinematic strain hardening（运动强化）·Principalofmaximumplasticresistance（最大塑阻原理）·Lawofplasticflow（塑性流动定律）·Elastic unloadingconditions（弹性卸载的条件）2
Outline • Introduction（引言） • 1D plasticity theory（一维塑性） • Rough values of yield stress（常用工程材料屈服应力值） • 3D plasticity theory（三维塑性理论） • Decomposition of strain（应变分解） • Yield criterion（屈服判据） • Yield surface（屈服面） • Isotropic strain hardening（各向同性强化） • Kinematic strain hardening（运动强化） • Principal of maximum plastic resistance（最大塑阻原理） • Law of plastic flow（塑性流动定律） • Elastic unloading conditions（弹性卸载的条件） 2
Lntroduction. Linear elastic first: Plastic (permanent deformation); Unloadingfollows linear curve; Relaxation; Creep; Bauschinger effect; Cyclichardening/softening, Rate, loading history and temperatureHold atdependentconstant stressStressHoldatconstantstrainLinearUnloadingelasticStrainPermanentstrain3
• Linear elastic first; Plastic (permanent deformation); Unloading follows linear curve; Relaxation; Creep; Bauschinger effect; Cyclic hardening/softening; Rate, loading history and temperature dependent Introduction 3
Lntroduction.In 1930's,Taylorand scientists experimentallymeasured theresponseofthin-walled tubes under combined torsion, axial loading, and hydrostatic pressure.: Hydrostatic stress has no effects on plastic deformation..Plastic behavior doesn't induce volume change of a material.: Plastic deformation is caused by shearing of atomic planes via propagation of atype of lattice defects called dislocations.: During plastic loading, the principal components of the plastic strain rate tensorare parallel to the components of stress acting on the solid.Levy-Mises flow rule relates the principal plastic strain increment to theprincipal stresses.def - delldep -deidel-dspC,-0u-d1C-Omdislocation4
• In 1930’s, Taylor and scientists experimentally measured the response of thinwalled tubes under combined torsion, axial loading, and hydrostatic pressure. • Hydrostatic stress has no effects on plastic deformation. • Plastic behavior doesn’t induce volume change of a material. • Plastic deformation is caused by shearing of atomic planes via propagation of a type of lattice defects called dislocations. • During plastic loading, the principal components of the plastic strain rate tensor are parallel to the components of stress acting on the solid. • Levy–Mises flow rule relates the principal plastic strain increment to the principal stresses. Introduction 4 p p p p p p I II II III III I I II II III III I d d d d d d
Introduction: Decomposition of strain, yield criteria, strain hardeningrules, plastic flow rule, elastic unloading criterion. We restrict attention to small deformations (≤10%)9,80OmetalQyoEECo1 &pE5
• Decomposition of strain, yield criteria, strain hardening rules, plastic flow rule, elastic unloading criterion • We restrict attention to small deformations (≤10%). Introduction 5