材料性能Ch1_UniaxialMechanicalProperties.pptVIP

Ch.1 Mechanical Properties 材料的力学性能 Varying but characteristic types of curves shown by different materials 　　　　 Yield point criteria /屈服标准 In Engineering, ??? (1)Proportional limit 比例极限??应力-应变曲线上符合线 性关系的最高应力，国际上常采用σp表示，超过σp时即认为材料开始屈服。 ??? (2)Elastic limit 弹性极限??以不出现残留的永久变形为标准，材料能够完全弹性恢复的最高应力。国际上通常以σel表示。应力超过σel时即认为材料开始屈服。 ??? (3)Yield point/onset of plastic deformation to a degree 屈服强度??以规定发生明显的残留变形为标准，如通常以0.2%残留变形的应力作为屈服强度，符号为σ0.2或σys。 （中高碳钢、无屈服点，以产生一定的微量塑性变形的抗力的极限应力值来表示。） Factors influencing yield strength Intrinsic/内在因素： Bonding states, Microstructure, Crystalline structure, Atoms type (结合键、组织、结构、原子本性) Strain hardening/形变硬化 Mechanism of strain hardening Tensile strength Necking/抗拉强度与颈缩条件 Prerequisite for necking /颈缩条件 At the point the maximum of stress reaches, thus, dF=0 ??????dF=d(S·A)=AdS+SdA=0 (面积A与真实应力S ) then? -dA/A=dS/S ??? volume constant theory/体积不变定理 dL/L=-dA/A=dε Thus,? dS/dε=S, equally, n=eb ?This is the prerequisite for necking/这就是出现颈缩的判据 1. True fracture strength/真实断裂强度 Idealistic crystalline materials’ TFS/理想晶体脆性（解理）断裂的理论强度。 3.Theoretical fracture strength for a cracked crystal/含裂纹材料理论断裂强度（格里匪斯裂纹理论） Energy storageconversion in materials deformation/材料变形过程的能量转换(应力与应变的综合)  Resilience/回弹性/顺应力 Resilience is the capacity of a materials to absorb energy when it is deformed elastically and then, upon unloading, to have this energy recovered. Modulus of resilience, Ur /弹性比功 Anelasticity /非理想弹性Internal Damping /内耗 Anelasticity/滞弹性 The property of a solid in which deformation depends on the time rate of change of stress as well as on the stress itself. Viscoelasticity/粘弹性 pseudoelasticity/伪弹性 Pseudoelasticity, sometimes called superelasticity, is an elastic (reversible) response to an applied stress, caused by a phase transformation. Example: shape memory alloys--形状记忆合金 Bauschinger effect/包申格效应 Toughness, static toughness/静力韧度 韧度: 材料断裂前吸收塑性变形功和断裂功的能力。 材料的韧性用韧度度量(习惯上，