烧结钢的应力-弹性及塑性应变曲线的制作与评价

Preparation and evaluation of stress-elastic and plastic strain diagrams of sintered steels

根据拉伸试验(TT)得到的应力-应变曲线和通过声音脉冲方法(APM)得到的声速,计算并比较了烧结钢的弹性模量(E)和泊松比(ν)。Err和νTT的值分别小于EAPM和νAPM,这是因为在烧结钢的应力-应变中不仅包含了弹性应变,而且也包含了塑性应变。利用由EAPM和νAPM的值计算得到的纵向和横向弹性应变,从纵向和横向应力-应变中分离出纵向和横向的塑性应变。在小应变时烧结钢没有显示线性应力-应变的情况下,可以很简单地由纵向塑性应力表中求出弹性极限或0.2%的屈服强度。对于同样的应力,每个样品的弹性应变和塑性应变的不同,可以由基于孔隙特征(孔隙的大小、形状、相互连接及微观结构的不同)的模型来解释。

The differences in Young＇ s moduli （ E ） and Poisson＇ s ratios （ v ）, calculated by the stress-strain diagrams from tensile testing （TT） and the sound velocities from an acoustic pulse method （APM）, of sintered steels were compared. The values of ETT and VTT were smaller than those of EAPM and vAPM,respectively,because not only the elastic strain, but also the plastic strain are included in the stress-strain diagram of the sintered steels. Furthermore, by using the longitudinal and transverse elastic strains calculated from the values of EAPM and vAPM, the longitudinal and transverse plastic strains were separated from the stress-longitudinal and transverse strain diagrams. Consequently,the elastic limit or 0.2 % yield strength was simply defined from the stress-longitudinal plastic strain diagram,in the case of the sintered steels which does not show a linearity of stress - strain diagram at the lower stresses. The differences in the elastic and plastic Strains versus stress of each sample were explained on the basis of the pore characteristics, such as size, shape, and interconnection, and microstructures.