Analysis and assessment of residual stress components normal to the surface by X-ray diffraction techniques

由于所使用的x射线穿透深度小，在衍射残余应力分析中，大多数情况下假设平面表面平行残余应力状态，忽略可能存在的垂直于表面的应力分量。然而，这种假设往往是有问题的，其后果也难以评估。在本项目中，使用不同类型的衍射残余应力分析，将分析样品表面法向的残余应力分量的特征材料状态，并描述它们的深度分布。研究将集中在接触加载后的材料状态，这在工业实践中非常重要，例如在驱动技术或工件与工具之间的相互作用中。将系统地研究加载条件、材料微观结构和表面法向残余应力分量之间的关系。将应用不同的互补衍射技术进行应力分析：包括电解表面层去除在内的传统方法，包括同步辐射在内的改变x射线信息深度的特殊技术，以及对变形材料体积的特殊制备部分的测量。将研究具有不同显微组织的普通碳钢。静态和振荡接触载荷都会产生残余应力状态。通过这种方式，在明确的条件下，材料状态、加载条件和产生的垂直于表面的残余应力之间的相关性将被评估。

Due to the small penetration depth of the X-rays used, in case of diffraction residual stress analysis, in most cases a plane surface parallel residual stress state is assumed neglecting possibly existing stress components normal to the surface. This assumption, however, is often questionable and consequences are difficult to assess. In the present project using different types of diffraction residual stress analyses residual stress components normal to the sepecimens surface will be analysed for characteristic materials states and their depth distributions will be described. Investigations will focus on materials states after contact loading, which is very important in industrial practice, e. g. in drive technology or in interactions between workpiece and tools.Correlations between loading conditions, materials microstructures and residual stress components normal to the surface will systematically be studied. Different complementary diffraction techniques for stress analysis will be applied: conventional methods including electrolytical surface layer removal, special techniques to vary the information depths of the X-rays used including synchrotron radiation as well as measurements on specially prepared sections of the deformed materials volumes. Plain carbon steels with different microstructures will be investigated. Residual stress states will be produced by static and oscillating contact loading. In this way under well defined conditions the correlations between materials states, loading conditions and resulting residual stresses normal to the surface will be evaluated.