| The sawtooth chip produced in the condition of high speed cutting with difficult-to-machining materials can influence the process quality of workpiece. The production of sawtooth chip and the adiabatic shearing phenomenon are colsely interrelated. By the study of formation process and microscopic mechanism of adiabatic shear band (ASB) in chips, it is benefit for understanding the chip formation in high speed cutting and improving the processing technology. In this paper, using the methods of microstructure observation, microcosmic theoretic analysis and computer simulation, the adiabatic shear behavior during orthogonal cutting of hot-working die steel (4Cr5MoSiV1) is investigated. The main research contents are summarized as follows:1. Through experiment of high speed orthogonal cutting, the chip evolution processes of macroscopic shape and microscopic characteristic under the different cutting conditions are observed. The macroscopic shape of chips mainly experienced these stages: long-belt chip,loose and spiral chip,spring-type chip,arc-slice chip and granular chip. The microscopic characteristic of chip goes through four stages which are the ribbon chips,the critical sawtooth chip,the deformed band sawtooth chip and the transformed band sawtooth chip.2. Combining with adiabatic shear theory under high strain rate condition, the analysis of microscopic experiment in adiabatic shear band is carried. This research focuses on the following things: the degree of chip deformation; the characteristics and distribution regularity in ASB; the effect of cutting conditions on ASB and the distribution of microhardness in ASB.3. To simulate high speed orthogonal cutting of 4Cr5MoSiV1 hardened steel, a commercial FE code (ABAQUS/Explicit) has been used. Based on the finite element analysis, the formation mechanism of sawtooth chip and the changes of thermodynamic parameters in adiabatic shear band are disclosed, as well as researching the effect of main cutting parameters on sawtooth chip.
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