Material Removal Mechanism Of Laser-Assisted Micro-Milling TC4 Based On Chip Morphology

When machining titanium alloy,the chips are often saw-toothed.Due to the alternating effects of thermal softening,strain hardening,or the occurrence of periodic cracks,serrated chips exhibit a very obvious regularity.It plays an important role in exploring the mechanism of material removal during cutting.Laser-assisted micro-milling uses laser preheating to soften materials,thereby improving the machinability of difficult-to-machine materials such as titanium alloys,improving machining quality,improving chip morphology and reducing cutting forces,and significantly increasing tool life.The introduction of an external heat source makes the removal mechanism of titanium alloy processing that is already very complicated more complicated.This thesis focuses on the chip morphology produced by LAMM of Ti6Al4 V material.During the formation of serrated chips,the adiabatic shear phenomenon that occurs between the serrated units has very important theoretical value and engineering application value.Firstly,the tool-chip friction characteristics were studied.Taking the local shear flow stress of chips in the chip area during processing and the constant friction coefficient in the sliding area as unknown parameters,a tool-chip friction model was established.By studying the temperature rise caused by three heat sources such as friction,shearing and laser irradiation,the temperature field model of the tool-chip contact surface was established,and the influence of temperature on the chip was explored.Then,two-dimensional cutting simulations of micro-milling and laser-assisted micro-milling are performed on Ti6Al4 V materials respectively.First describe the laser parameters with secondary development technology,and input the temperature field information after laser scanning into the two-dimensional simulation to obtain the chip morphology of LAMM.The chip morphology,cutting force,temperature field and stress obtained by micro-milling simulation and laser-assisted micro-milling simulation were compared and analyzed to further reveal the chip forming mechanism.Finally,taking chip morphology,cutting force and processing quality as the evaluation criteria,the comparison experiment between micro-milling and laser assisted micro-milling was completed to study the influence of process parameters on chip morphology,chip sawtooth degree,sawtooth frequency,sawtooth Angle and other geometric characteristics.The change of chip morphology and cutting force were determined by scanning electron microscope and other instruments,and the theoretical and simulation results were further verified according to the experimental results,and the significance test was completed.