Understanding asperity flattening is vital for a reliable macro-scale modeling of friction and wear. In sheet metal forming processes, sheet surface asperities are deformed due to contact forces between the tools and the workpiece. In addition, as the sheet metal is strained while retaining the normal load, the asperity deformation increases significantly. Deformation of the asperities determines the real area of contact which influences the friction and wear at the tool-sheet metal contact. The real area of contact between two contacting rough surfaces depends on type of loading, material behavior, and topography of the contacting surfaces. In this study, an experimental setup is developed to investigate the effect of a combined normal load and sub-surface strain on real area of contact. Uncoated and zinc coated steel sheets (GI) with different coating thicknesses, surface topographies, and substrate materials are used in the experimental study. Finite element (FE) analyses are performed on measured surface profiles to further analyze the behavior observed in the experiments and to understand the effect of surface topography, and coating thickness on the evolution of the real area of contact. Finally, an analytical model is presented to determine the real area contact under combined normal load and sub-surface strain. The results show that accounting for combined normal load and sub-surface straining effects is necessary for accurate predictions of the real area of contact.

了解粗糙平坦度对于可靠的摩擦磨损宏观模型至关重要。在钣金成形过程中，由于工具与工件之间的接触力，钣金表面的凹凸会变形。另外，由于在保持正常载荷的同时使金属薄板变形，因此粗糙变形显着增加。凹凸的变形决定了实际的接触面积，该面积会影响工具薄板金属接触处的摩擦和磨损。两个接触的粗糙表面之间的实际接触面积取决于载荷的类型，材料的行为以及接触表面的形貌。在这项研究中，开发了一个实验装置来研究法向载荷和地下应变的组合对实际接触面积的影响。在实验研究中使用具有不同涂层厚度，表面形貌和基材的未涂层和锌涂层钢板（GI）。对测量的表面轮廓进行有限元（FE）分析，以进一步分析在实验中观察到的行为，并了解表面形貌和涂层厚度对实际接触区域演变的影响。最后，提出了一个解析模型来确定法向载荷和地下应变共同作用下的实际面积接触。结果表明，要准确预测实际接触面积，必须考虑到法向载荷和地下应变共同作用的影响。对测量的表面轮廓进行有限元（FE）分析，以进一步分析实验中观察到的行为，并了解表面形貌和涂层厚度对实际接触区域演变的影响。最后，提出了一个解析模型来确定法向载荷和地下应变共同作用下的实际面积接触。结果表明，要准确预测实际接触面积，必须考虑到法向载荷和地下应变共同作用的影响。对测量的表面轮廓进行有限元（FE）分析，以进一步分析在实验中观察到的行为，并了解表面形貌和涂层厚度对实际接触区域演变的影响。最后，提出了一个解析模型来确定法向载荷和地下应变共同作用下的实际面积接触。结果表明，要准确预测实际接触面积，必须考虑到法向载荷和地下应变共同作用的影响。