Simulated and experimental analysis on serrated chip formation for hard milling process

Significance 

Ideally, hard milling is a specialized machining process that allows machine shops to mill parts that have a hardness higher than 50HRC. Currently, with the imminent advancement of high-performance cutting tools and high-speed machine tools, hard milling process has become more popular in the fields of manufacturing high precision automotive and molding components. The process itself is ecofriendly, of high-throughput, cost effective and achieves the desired surface quality. However, the process suffers from several shortfalls, namely: the onset of serrated chip ties up with cutting forces, tool-chip interface temperature and surface quality as well as dynamic behavior of cutting system. A focus on serrated chip formation reveals that much experimental work has been carried out in a bid to comprehend the chip formation mechanism and its associated physical phenomena.

A plethora of literature exists where each work depicts a different approach focused at comprehending various shortfalls of the cutting process. Unfortunately, very limited studies have investigated the milling process with focus being the formation mechanism of serrated chip.

Therefore, deep understanding and optimizing of cutting parameters is of great interest; thus, it is imperative to explore the serrated chip formation with respect to physical aspects encountered in milling processes. In this view, a group of researchers from the School of Mechanical Engineering at Shandong University: Binxun Li, Qing Zhang and Luli Li and led by Professor Song Zhang proposed to concurrently simulate by finite element method and experimentally investigate the effects of cutting speed on chip characteristics. Their main objective concerned the serrated chip formation accompanying micro-cracks and physical phenomena which was achieved using finite element method (FEM). Their work is currently published in Journal of Manufacturing Processes.

To begin with, the research team proposed a hard-milling simulation model based on Johnson-Cook visco-plastic constitutive material model combined with Johnson Cook damage accounting for shear localization. Secondly, the researchers validated the proposed FE model using acquired experimental results.

The authors reported that the predicted results were in good agreement with experimental results regrading chip morphology and cutting forces. Further, the physical phenomena governing the formation of serrated segment and micro-cracks were discussed and clarified deeply through FE analysis. Additionally, the localized plastic strain state on the machined surface associated with serrated segment formation was observed and identified.

In summary, the study by Professor Song Zhang and his research group introduced a simplified 2D FE model to investigate the serrated chip formation concerning the occurrence of micro-cracks and variation of physical phenomenon during hard milling of AISI H13 steel. To validate their model, the researchers carried out hard milling experiments. Overall, in an interview with Advances in Engineering, Professor Song Zhang, the lead author emphasized that their work, on one hand could deepen the understanding of the formation mechanism of serrated segment; while still, the results obtained could offer guidance for cutting parameters optimization and desired machined surface integrity control.

Simulated and experimental analysis on serrated chip formation for hard milling process - Advances in Engineering

About the author

Song Zhang is currently a full professor at School of Mechanical Engineering, Shandong University. He received his BE (1991) and ME (1994) in mechanical engineering from Shandong polytechnic University, China. He earned his Ph.D. degree in mechanical engineering from Shandong University in 2004, and then he has a position as a lecture in Shandong University. Prior to joining Shandong University, he worked as a mechanical engineer in JIER Machine-tool Group Co., Ltd. for seven years. From Aug. 2007 to Aug. 2008, he went to the University of Alabama for one-year visiting research supported from the China Scholarship Council.

His current research interests include high-efficiency machining mechanism and machined surface integrity of difficult-to-machined materials (hardened steels, Nickel-based alloys, and Titanium alloys), dynamic analysis and optimal design of CNC machine tools, energy efficiency management of machining process, and so on. He has authored or coauthored more than 100 papers in refereed journals, and he was recognized as a Taishan Distinguished Professor in Shandong University in 2017.

About the author

Mr. Binxun Li is currently a Ph.D. candidate at the School of Mechanical Engineering, Shandong University. He received his Master degree from University of Science and Technology, Liaoning. His research interests include surface integrity, simulating modelling and materials characterization in hard milling process. He has published 9 technical articles, including about 8 journal articles and 1 conference paper.

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About the author

Mr. Qing Zhang is currently a Ph.D. candidate at the School of Mechanical Engineering, Shandong University. His research interests include numerical modeling of 3-dimensional machined surface topography and finite element simulation in hard milling of hardened steels.

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About the author

Miss Luli Li is currently an assistant engineer of COMAC Shanghai Aircraft Manufacturing Co., Ltd. She received her Master degree from Shandong University in 2019. Her research interests include theoretical and finite element analysis about machining processes.

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Reference

Binxun Li, Song Zhang, Qing Zhang, Luli Li. Simulated and experimental analysis on serrated chip formation for hard milling process. Journal of Manufacturing Processes, volume 44 (2019) page 337–348.

Go To Journal of Manufacturing Processes

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