During the cooling process of the molten material, residual stresses appear because the reduced volume of the cooled material cannot fully fill the space formerly occupied by the molten material. The morphology in and around the weld is formed by different factors depending on the material and process parameters. Different morphological structures relate to different mechanical properties. The process parameters and the welding results including morphology and residual stress are linked together. In this article, residual stresses and the mechanical properties of a hot-plate-welded polypropylene specimen with 0.1 wt.-% content of carbon black are investigated in relation to the morphology. Different measurement positions and joining displacements of parts to be joined result in different residual stress states and morphological structures. The higher the joining displacement, the higher the residual stress. Investigations of the morphology show a relation between the size of the alpha spherulites and the joining displacement. Diffractions patterns of wide-angle X-ray scattering (WAXS) are not able to resolve the beta phase of the specimen.

中文翻译：

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用热板焊接研究聚丙烯中的残余应力

在熔融材料的冷却过程中，由于减小的冷却材料的体积不能完全填充先前由熔融材料占据的空间而出现残余应力。取决于材料和工艺参数，焊缝内部和周围的形态是由不同的因素形成的。不同的形态结构涉及不同的机械性能。工艺参数和焊接结果（包括形态和残余应力）链接在一起。在本文中，研究了炭黑含量为0.1 wt .-％的热板焊接聚丙烯试样的残余应力和力学性能与形貌的关系。不同的测量位置和待接合零件的接合位移会导致不同的残余应力状态和形态结构。连接位移越大，残余应力越高。形态研究表明，α球晶的尺寸与结合位移之间存在关系。广角X射线散射（WAXS）的衍射图不能分辨样品的β相。