论文部分内容阅读
本文采用光弹贴片法研究材料在静拉伸及疲劳负荷下的屈服过程。试验表明:金属材料不管它是否具有明显的屈服点,在拉伸过程中,首先在应力集中处发生局部的宏观屈服,然后塑性应变区沿试样标距扩展,其塑变过程是相同的。不同材料具有不同的塑性传播特性。黄铜的塑性传播速度很快,16Mn双相态则很慢。多数材料只从少数应力集中区开始屈服;而球铁则有很多屈服策源地。材料在静屈服点以下循环加载时,亦经受着类似的塑性传播过程。但其传播特点还要受到材料在疲劳过程中硬化、软化行为的影响,应变在试样标距范围内分布是不均匀的。所以通常测得的疲劳硬化、软化曲线只反映了试样标距范围内的宏观平均值,并不能真实反映材料的硬化、软化行为。
In this paper, the photoelastic method is used to study the yield process of materials under static tension and fatigue loading. Experiments show that the metallic material, regardless of whether or not it has a distinct yield point, undergoes local macro-yielding at the stress concentration point first, and then the plastic strain zone extends along the gauge length of the specimen during the stretching process. The plastic deformation process is the same. Different materials have different plasticity propagation characteristics. Plastic propagation of brass fast, 16Mn biphasic state is very slow. Most materials only yield from a few stress concentration areas; while ductile iron has many yield sources. When the material is cycled under static yielding point, it undergoes a similar plastic propagation process. However, its propagation characteristics are affected by the hardening and softening behavior of the material during the fatigue process. The strain distribution in the gauge length of the sample is not uniform. Therefore, the measured fatigue hardening and softening curve usually only reflect the macroscopic average value within the gauge range of the sample, and can not truly reflect the hardening and softening behavior of the material.