摘要
对高速铣削的切屑进行了微观组织研究,建立了切削要素、切屑形态、切削力、表面粗糙度等因素之间的关系。研究发现,切削速度越高,热量向外扩散的时间越少,聚集在剪切带内的热量越多,剪切带内发生动态再结晶的可能性也就越高,大量的热量促进了剪切带内的热塑性失稳,进而使绝热剪切带产生的频率大幅度提高,切屑的锯齿化程度也就随之加大;计算了不同切削条件下绝热剪切带中心的温度、热量扩散速度等,发现热量扩散速度远低于其变形速度,进而证明了高速切削钛合金Ti-6Al-4V时,绝热剪切带内发生了动态再结晶现象。考虑到再结晶软化效应对材料本构的影响情况,建立了改进J-C本构模型,该模型用两个表达式表述不同临界应变值区间范围的材料本构特征,理论计算证明了改进J-C本构比J-C本构更准确。
The microstructure of chips in high-speed milling is analyzed, and the relationship between the cutting factors, chip formation, cutting force and surface roughness is established. It is found that the higher cutting speed is the less time heat spreads, the more heat in the shear zone gathers, the higher the possibility of occurrence of dynamic recrystallization in shear zone gets. A large amount of heat promotes the thermoplastic instability within the shear zone, the frequencies of the adiabatic shear band and the degree of serrated chip increase. The temperature and the cooling rate in adiabatic shear band are calculated, and it is found that deformation time is much lower than the cooling time. It is proved that dynamic recrystallization phenomenon occurs in high speed milling. The modeling of new developed J-C constitutive model which considers recrystallization softening effect is built; it has two expressions according to the different characteristics of material constitutive during critical strain values. Theoretical calculations proved that the developed J-C constitutive is more suitable than J-C constitutive.
出处
《机械工程学报》
EI
CAS
CSCD
北大核心
2015年第3期196-205,共10页
Journal of Mechanical Engineering
基金
国家自然科学基金(51275490)
山西省回国留学人员科研(2013-086)
中北大学校基金资助项目
