A quantitative study of the tribological size effect in microforming with a multi-region FEA model

作者：Kim Hong Seok^*

来源：Tribology International, 2015, 90: 104-112.

DOI：10.1016/j.triboint.2015.04.016

• Microforming
• Size effect
• Tribology
• Lubricant pockets

Microforming technologies are very suited for the mass production of microscale products. However, the industrial applications of microforming processes are still limited, because the so-called size effects make it difficult to understand and predict the deformation behavior of the material in microforming. In this study, the scaled upsetting experiments of disks were performed to investigate the tribological size effect in microforming. A simple multi-region FEA model was utilized to determine the frictional properties of the material at the dry and lubricated interface conditions and to verify the open and closed lubricant pockets theory. The general trend of increasing friction with decreasing specimen size can be expressed quantitatively from the experimental and numerical results. The increasing fraction of the open lubricant pockets in microforming was identified as the major reason for the size effect phenomenon in friction. It was found that when this fraction exceeds a certain critical value, the lubrication effect becomes negligible due to the high frictional stress of the open lubricant pockets. It is expected that this research provides the in-depth understandings on the friction size effect in microforming to establish the design guidelines and optimize the process parameters cost-effectively.

• 出版日期2015-10