Due to the size effect phenomenon, the conventional friction models commonly used in metal forming are not accurate for use in micro-metal forming. In this study, the frictional size effect, as one of the most important phenomena in micro-metal forming, has been investigated. Different frictional models developed based on open and closed lubricant pockets theory have been investigated in both dry and lubricated frictional conditions. Those models use a scale parameter to quantify friction on the micro-scale and a real contact area to calculate the friction force at contacting surface. The models were implemented into ABAQUS finite element package via the VFRIC_COEF subroutine interface. The ring compression test with specimens of different sizes was used to determine the parameters of the models. By reducing the dimensions of the specimens in the ring compression test, no size effect was observed in dry friction conditions. However, in the lubricated frictional conditions, it was observed that the coefficient of friction increased significantly with reducing the specimen size. As the dimensions of the specimen decrease and the scale parameter approaches 1, the gap between the coefficient of friction curves increases significantly, and the coefficient of friction converges to those obtained in dry friction conditions.

由于尺寸效应现象，金属成形中常用的传统摩擦模型不适用于微金属成形。在这项研究中，对摩擦尺寸效应作为微金属成形中最重要的现象之一进行了研究。基于开放和封闭润滑剂腔理论开发的不同摩擦模型已经在干摩擦和润滑摩擦条件下进行了研究。这些模型使用尺度参数来量化微观尺度上的摩擦，并使用实际接触面积来计算接触表面的摩擦力。该模型通过 VFRIC_COEF 子程序接口实现到 ABAQUS 有限元包中。采用不同尺寸试样的环压缩试验来确定模型的参数。通过减小环压缩试验中样品的尺寸，在干摩擦条件下没有观察到尺寸效应。然而，在润滑摩擦条件下，观察到摩擦系数随着试样尺寸的减小而显着增加。随着试件尺寸减小、尺度参数接近1，摩擦系数曲线之间的差距显着增大，摩擦系数收敛于干摩擦条件下的摩擦系数。