Ruisong Jiang

Mechanisms and FEM Simulation of Chip Formation in Orthogonal Cutting In-Situ TiB2/7050Al MMC

The in-situ TiB2/7050Al composite is a new kind of Al-based metal matrix composite (MMC) with super properties, such as low density, improved strength, and wear resistance. This paper, for a deep insight into its cutting performance, involves a study of the chip formation process and finite element simulation during orthogonal cutting in-situ TiB2/7050Al MMC. With chips, material properties, cutting forces, and tool geometry parameters, the Johnson–Cook (J–C) constitutive equation of in-situ TiB2/7050Al composite was established. Then, the cutting simulation model was established by applying the Abaqus–Explicit method, and the serrated chip, shear plane, strain rate, and temperature were analyzed. The experimental and simulation results showed that the obtained material’s constitutive equation was of high reliability, and the saw-tooth chips occurred commonly under either low or high cutting speed and small or large feed rate. From result analysis, it was found that the mechanisms of chip formation included plastic deformation, adiabatic shear, shearing slip, and crack extension. In addition, it was found that the existence of small, hard particles reduced the ductility of the MMC and resulted in segmental chips.

Evaluation of Residual Stress Distribution and Relaxation on In Situ TiB2/7050 Al Composites

Interior residual stresses induced by quenching may cause distortion during subsequent machining processes. Hence, various strategies have been employed to relieve the interior residual stress, such as stretching, post treatment, and other techniques. In this study, the stress distribution inside TiB2/7050 Al composite extrusions was investigated and the effects of different methods on relieving the quenching-induced stress were compared. Firstly, three TiB2/7050 Al composite extrusions were treated by stretching, stretching and heat treatment, and stretching and cold treatment processes, respectively. Then, the multiple-cut contour method was employed to assess the residual stresses in the three workpieces. Experimental results indicate that the interior stress of TiB2/7050 Al composite extrusions after stretching ranges from −89 MPa to +55 MPa, which is larger than that in 7050 aluminum alloy, which ranges from −25 Pa to +25 MPa. The heat treatment performs better than the cold treatment to reduce the post-stretching residual stress, with a reduction of 23.2–46.4% compared to 11.3–40.8%, respectively. From the stress map, it is found that the stress distribution after the heat treatment is more uniform compared with that after the cold treatment.

Model reconstruction in adaptive machining for near-net-shape rolling compressor blades

ABSTRACT Because of its high productivity, the near-net-shape rolling process has received much attention for the manufacture of compressor blades of gas-turbine. However, due to the inherent characteristic of the rolling process, the material forced outward at the edges of the rolling blade still needs to be removed. Since each blade suffers from a different surface deformation within the tolerance zone, edges machined based on the nominal CAD model may not transition to the blade body smoothly. To solve this problem, an adaptive modelling method for machining surfaces of near-net-shape rolling blades is proposed. Through a rigid transformation and a subsequent deformation adjustment, each reference curve of the nominal CAD model can be registered to the corresponding measurement point set without losing its original shapes seriously, and then be used as the sectional curve of machining surfaces. Finally, the proposed method is verified on some blades, and the experimental results show that the edges milled with the reconstructed machining surfaces can transition to the blade body smoothly and accurately.