Cutting Mechanism Of Aerospace Light Alloy Based On Ductile Failure

Aerospace titanium alloy and aluminum alloy are widely used in the aviation, aerospace and civil industry. Normaly, the machining of aerospace structure requires high machining accuracy and high efficiency. Therefore, the study of aerospace titanium alloy and aluminum alloy machining mechanism (including the chip morphology, force and temperature) has great meaning to improve the manufacturing technology in aerospace and other industry.The stress-strain relationship was analyzed under the thermo-elastic-plastic condition firstly. An energy-based ductile failure material model was developed according to the stress-strain response of material ductile failure process. In modeling, the Johnson-Cook model was used to characterize the plastic deformation process, and the ductile failure iniation and evoulation criteria were applied to characterize the ductile failure process.The energy-based ductile failure model was applied to simulate Ti-6Al-4V alloy orthogonal cutting process. The simulation result demonstrates that the mesh characteristic dimension has greater influence on the simulated cutting force and chip morohology. In order to reduce the influence of the mesh dimension, a ductile failure energy density method was proposed in the failure evoulation stage. The developed method can provide an efficient modeling method for the cutting process finite element simulation.A serious of Ti-6Al-4V alloy orthogonal cutting experiments were proposed to investigate the segmented chip morphology. The characteristic dimensions of the segmented chip were analyzed by the metallographic of the chip section. Meanwhile, the energy-based ductile failure model was applied to simulate the Ti-6Al-4V alloy orthogonal cutting. The simulated chip morphology and cutting force show good agreement with experimental result. In addition, some extremely high speed Ti-6Al-4V alloy cutting simulations were carried out, and the variation of the segmented chip under these conditions was analyzed.The simulated stress, strain, temperature, strain gradient and temperature gradient along adiabatic shear band were analyzed. A phenomena of"same tendency but lag slightly"was found in the relationship between the strain and temperature, and also between the strain gradient and temperature gradient, which demonstrates that the thermo-softening effect predominates over the effect of strain hardening along the adiabatic shear band, resulting in the formation of segmented chip. These phenomena gave a new evidence of thermoplastic instability theory.The aluminum alloy 2A12 micro-cutting simulation was proposed by the ductile failure material model. In order to acquire accurate simulation result, the steady state characteristics of the micro-cutting process was analyzed by the simulated heat flux and micro-cutting force. In addition, a high-speed response thermocouple was applied to measure the temperature in the micro-cutting process. The temperature at tool tip and the workpiece surface were acquired at the same condition. The variation of the temperature at tool and workpiece surface under different conditions was disccused. Meanwhile, the micro-cutting FEA was applied to predict the temperarure distribution, the predicted results agreed well with the experimental value. Meanwhile, the influence of cutting temperature on specific cutting energy, tool-chip interaction and chip morphology were analyzed.