Papers by Keyword: Machining Distortion

Abstract: The workpiece distortion that occurs during machining, can lead to a large increase in the number of the scrap parts. Residual stresses are the main cause of these distortions and they are generally present in both forging and casting products. In order to obtain the desired microstructure and mechanical properties, the workpiece is subjected to heat treatment before being worked. Quenching produces residual stresses that exist throughout a large percentage of the casting or forging part. Distortion occurs as a result of removing stressed material from the workpiece. The component will re-equilibrate and distort as each layer of stressed material is machined away. This paper describes a procedure development for distortions numerical analysis on a SAF2507 casting bulk workpiece. A solubilization heat treatment has been simulated, in order to predict the bulk residual stresses distribution. Different metal cutting processes have been considered to measure the numerical distortions induced in the workpiece.

Abstract: Machining distortion analysis and control are the kernel problem in manufacturing industry recently. This paper take face milling as research object, a finite element model for 3D milling process is set up based on some key techniques including cutter feed trajectories representations, cutter tooth-workpiece engagement model etc; Then the optimum LS-SVM model which can express the transitive relationship between cutting parameters and distortion error is set up; The cutting parameters optimization model based on controlling the machining distortion is founded by seeing the optimum LS-SVM model as the main objective function, meanwhile, an effective multi-objective optimization algorithm is proposed by coupling particle swarm algorithm and gray relevancy analysis, this algorithm can change the multi-objective optimization problem into optimizing the gray relevancy value effectively. As an example, the feasibility of proposed machining distortion controlling approach is verified.

Abstract: Machining-induced distortion of large monolithic parts with thin walled structures creates problems in aircraft manufacturing industry. Typical monolithic beams of airframe are machined by NC machine and machining distortions are recorded. Thin walled structures are prone to distortions and dimensional instabilities due to internal stresses; therefore, stress-relieved vibration method is applied to reduce the internal stresses in blank material and results in better machining performance and dimension stability. But vibration stress-relief method doesn’t work always due to unknown reasons. Machining simulations in ANSYS are performed to predict the residual stress-induced machining distortion and simulation result is compared with the machining measurements to validate the simulation process. Cutting simulations have been executed by the element deactivation technique after developing the initial residual stresses via sequential coupled field analysis. The possibility of residual stress being relieved more reasonably and less distortion by optimized machining sequence through simulation is discussed.

Abstract: A physics-based material processing simulation is approached to research the machining distortion for high speed milling of titanium alloy aircraft monolithic component by the finite element method (FEM). Several mechanics models, such as material constitutive model, material removal model, and cutting loads application model, have been implemented to improve the accuracy of finite element simulation. The distortion result of aircraft monolithic component resulting from FEM show a good agreement with the experiment result. The research result shows that the distortion law of titanium alloy aircraft monolithic component is bending distortion and protruding upward, and the maximum distortion dimension lies in the middle of monolithic component.

Abstract: A physics-based material processing simulation is approached to research the machining distortion for titanium alloy aircraft monolithic component by the finite element method (FEM). Several key technologies, such as material constitutive model, material removal methodology of machining process, determination and application of cutting loads, have been implemented to improve the accuracy of finite element simulation. To verify the FEM result, an experiment is carried out. The distortion position and dimension of aircraft monolithic component resulting from FEM show a good agreement with the experiment result, which indicates that the key technologies presented in the paper are practicable and can be used to simulate the machining process of monolithic component to predict its distortion.

Abstract: The presence of residual stress in aircraft aluminum components can give rise to distortion after machining. Excessive distortion may result in the rejection of a part or the need for costly and time-consuming rework prior to placement in service. The purpose of this research was to develop a methodology for the prediction of machining-induced distortions of residually stressed aircraft aluminum components. Numerical simulation results show that the magnitude of machining distortion is strongly related to the square root of Stain Energy Density W or Stress Range σ . The experimental results demonstrate good agreement with the predicted machining distortions of 7075T73 bulkheads. It included that the original residual stress in the blocks of aircraft aluminum component is one of key factors to cause machining distortion.