Local stress of polyethylene spherulites under uniaxial stretching in small strain domain has been investigated by in-situ wide angle X-ray diffraction (WAXD) in comparison with macroscopic stress. Particular attention is paid to the elastic strain range. The local stress in equatorial and polar regions both increase in absolute value and follow a linear relation versus macroscopic stress. However, local stress turns out to be heterogeneous over the whole spherulites volume. The polar region shows higher local stress than equatorial region. Moreover, local stress along the a and b crystallographic axes in the crystalline lamellae enable determining the local stress triaxiality which is heterogenous. The increase of crystallinity promotes stress distribution heterogeneity throughout the spherulites. The origin of these phenomenon are discussed in terms of crystalline network percolation and effect of amorphous layer that modifies the local mechanical behavior. The present study provides a useful means for achieving the scale transition between the micro and the macro structural levels that is necessary for the modeling of the mechanical behavior of semi-crystalline polymers via micromechanical approaches.

与宏观应力相比，通过原位广角X射线衍射（WAXD）研究了在小应变域中单轴拉伸下聚乙烯球晶的局部应力。特别要注意弹性应变范围。赤道和极地区域的局部应力绝对值都增加，并且与宏观应力呈线性关系。但是，局部应力在整个球晶体积上是不均匀的。极地地区显示出比赤道地区更高的局部应力。此外，沿a和b的局部应力晶体薄片中的晶体学轴使得能够确定异质的局部应力三轴性。结晶度的增加促进了整个球晶的应力分布异质性。这些现象的起源是根据晶体网络的渗透和非晶层的作用来改变局部机械行为的。本研究提供了一种有用的手段，可以实现微观结构和宏观结构水平之间的尺度转换，这是通过微机械方法对半结晶聚合物的机械行为进行建模所必需的。