A Research on Stress-Induced Deformation of Thin Copper Substrate in Double-Sided Lapping

Double-sided lapping is an ultra-precision machining method capable of obtaining high-precision surface. However, during the lapping process of thin pure copper substrate, the workpiece will be warped due to the influence of residual stress-related, including the processing stress and initial residual stress, which will deteriorate the flatness of the workpiece and ultimately affect the performance of components. In this study, finite element method (FEM) was adopted to study the effect of residual stress-related on the deformation of pure copper substrate during double-sided lapping. Considering the initial residual stress of the workpiece, the stress caused by the lapping and their distribution characteristics, a prediction model was proposed for simulating workpiece machining deformation in lapping process by measuring the material removal rate of the upper and lower surfaces of the workpiece under the corresponding parameters. The results showed that the primary cause of the warping deformation of the workpiece in the double-sided lapping is the redistribution of initial residual stress caused by uneven removal of double-sided material. The finite element simulation results were in good agreement with the experimental results.

Residual Stress Analysis of a 2219 Aluminum Alloy Ring Using the Indentation Strain-Gauge Method

Aerospace thin-walled rings are vulnerable to machining distortion during the manufacturing process. Various research results show that the main factor causing machining deformation is initial residual stress inside the blank. In this study, the residual stress of a 2219 aluminum alloy ultra-large rolling ring was measured by using the indentation strain-gauge method. Results showed the maximum residual maximum principal stress was +265 MPa and stress distribution was uneven. To homogenize the initial residual stress of the ring, an expansion method is proposed based on the principle of pre-stretching plate, and the feasibility of the expansion method was analyzed by establishing a simplified theoretical model of ring. A FE (Finite Element) model was established to investigate residual-stress evolution during the rolling ring and the expanding ring process. The expansion simulation results show that the reduction rates of residual stress were greater than 40% and the maximum residual stress was only 65 MPa.

ANALYSIS OF THE PROCESSING SEQUENCE ON AIRFRAME STRUCTURES MACHING DEFORMATION

In order to reveal the influence of different processing procedures on the machining deformation of the whole structure of aviation frame type, a prediction model for the deformation of frame type integral structure caused by initial residual stress was established based on finite element. According to the deformation law of frame parts caused by initial stress of blank, the deformation of whole structure parts based on aviation frame is minimized. The influence of processing process on deformation of frame structure is studied. The results show that when removing the frame material, the deformation of the workpiece can be slowed down by first removing the area with large deformation and relatively concentrated material. And symmetrical removal of the frame material can also slow the deformation of the workpiece.

ANALYSIS OF THE PROCESSING SEQUENCE ON AIRFRAME STRUCTURES MACHING DEFORMATION

In order to reveal the influence of different processing procedures on the machining deformation of the whole structure of aviation frame type, a prediction model for the deformation of frame type integral structure caused by initial residual stress was established based on finite element. According to the deformation law of frame parts caused by initial stress of blank, the deformation of whole structure parts based on aviation frame is minimized. The influence of processing process on deformation of frame structure is studied. The results show that when removing the frame material, the deformation of the workpiece can be slowed down by first removing the area with large deformation and relatively concentrated material. And symmetrical removal of the frame material can also slow the deformation of the workpiece.

Effect of Initial Residual Stress on Machining Deformation of a Casing Part

Initial residual stress of blank is the main cause for the workpiece machining deformation. Based on the simplified equivalent model and the finite element analysis method, the effects of initial residual stress in bidirectional, axial direction and tangential direction on the deformation of an aluminum alloy conical case were studied respectively. The deformations of case were judged by flatness and roundness error of the end face of the case. From the results, it can be seen that the influence of the initial axial residual stress on the roundness error of the end face is greater than that of the radial residual stress; among all the errors, the roundness error of the large end face is much larger than that of other errors. It is shown that the roundness error of the large end face and the initial axial residual stress of the workpiece are the most important issues to be controlled in actual machining process. This conclusion has certain guiding significance for practical application.