张俊教授应邀参加6th International Symposium on Micro/Nano Mechanical Machining and Manufacturing
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发布时间：2021-10-30
发布时间：2021-10-30
文章标题：张俊教授应邀参加6th International Symposium on Micro/Nano Mechanical Machining and Manufacturing
内容：
2021年10月27日~29日，由北京理工大学与日本精密工学会纳米机械加工委员会联合发起和主办，国家自然科学基金委员会与日本学术振兴会共同资助，重庆大学、中国机械工程学会成组与智能集成技术分会、北京理工大学重庆创新中心协办的第六届“微细/纳米机械加工与制造国际研讨会（International Symposium on Micro/Nano Mechanical Machining and Manufacturing, ISMNM2021）”在中国重庆与日本宫城县两地采用线上线下相结合的方式同步举办。ISMNM2021的研讨主题包括：微细/纳米机械加工制造技术、微细切削刀具设计理论与制造技术、超精密加工及装备、微机械系统与智能装备、微细切削与磨粒加工技术、微细模具制造技术、微成形加工技术、微装配与集成技术以及微测试与试验技术。会议旨在深入交流该领域的国际学术前沿与研究热点，为国内外学者和工程专家提供一个展示最新研究成果、促进国际合作的交流平台，推动我国微细/纳米机械加工与制造技术的可持续发展。
张俊教授受邀参会，并围绕切削全过程的微观组织演变介绍了相关的研究进展，报告题目为“Exploration of Microstructure Evolution for Whole Cutting Process”，内容吸引了众多与会人员的关注。
摘要：In the cutting process, microstructure of workpiece material is a bridge between process parameters and surface mechanical properties. The study of its evolution process also helps to understand the removal mechanism of materials. However, offline material characterization can only obtain the final microstructure distribution results without its evolution process. This study provides an effective whole-process, multi-stage analysis method based on a multiscale simulation of microstructure evolution dominated by dynamic recrystallization mechanism: Firstly, a finite element (FE) model of cutting process, which incorporates a dislocation density based constitutive relation, is put forward considering the grain distribution of the workpiece material. The physical parameter distribution of macroscale and grain morphology of mesoscale is obtained. Based on cellular automata (CA) method and hybrid dynamic recrystallization mechanism model, the simulation of grain size and orientation evolution of chip and machined surface is realized. Secondly, chip material is divided into preloading, loading and unloading segments according to different loading state along its flow direction. Grain refinement simulation of the three segments is conducted respectively with different physical field distribution (strain, strain rate and temperature) as boundary condition. The microstructure parameter evolution rule (grain size, dynamic recrystallization fraction，geometrically necessary dislocation density) of primary shear zone and tool-chip interface is analyzed. Finally, microstructure gradient distribution characteristics of the machined surface of OFHC copper and Ti6Al4V alloy is carried out according to both experimental and computational results. The essential reason for surface texture discrepancy between two workpiece materials is revealed from the perspective of dislocation glide, twin formation, recrystallized grain nucleation and growth. This study lays a theoretical foundation for both understanding the physical nature of material removal and regulating the surface texture and mechanical properties of machined surfaces.