请教一个关于应力类型的名词！！微急~~谢谢~~

The individual stress components (S11,S12,etc.) may have magnitudes that exceed the value of the current yield stress; however the Mises stress at an integration point can never exceed the current yield stress of the element's material since the material was assumed to be perfectly plastic at this stress magnitude. However, the extrapolated nodal values reported in a contour plot may do so.
上面一段话中“The individual stress components ”，这个是什么应力呢？最近在做翻译，很是头痛啊。
谢谢~~~~~~