Vibration Control of Weakly Rigid Casing Based on Gasbag-rubber Damping Flexible Fixture

Combustion chamber casing is a key component of aeroengine, because of its poor rigidity, severe chattering occurs during milling, which seriously affects the surface quality and processing efficiency of the casing, and the existence of geometric nonlinear problems in the machining process makes it difficult to predict machining vibration. Therefore, it is of great significance to study the vibration law of thin-walled casing and reduce machining vibration. Aiming at the problem of vibration control of thin-walled casing, this paper proposes a new type of gasbag-rubber damping flexible fixture, which differ from the ordinary rigid fixture, this fixture has adjustable clamping force and good vibration damping ability. The key factors affecting the vibration response of the thin-walled casing are studied through establishing an equivalent dynamic model of the workpiece-fixture system. The research results show that the gasbag-rubber damping flexible fixture can effectively provide support stiffness, which is beneficial to reduce the vibration of the workpiece during processing; According to the actual thickness of different workpieces, the appropriate gasbag pressure is recommended to give play to the vibration damping performance of the fixture; It is recommended that the thickness of the rubber damping block in practice is 8~12mm. The research work in this paper has important guiding significance for the design and use of the gasbag-rubber damping flexible fixture, and provides an effective theoretical prediction for the vibration of the thin-walled casing.

Prediction of Frequency Response Function for Cylindrical Thin-Walled Workpiece with Fixture Support Constraints

Auxiliary fixtures are widely used to enhance the rigidity of cylindrical thin-walled workpieces (CTWWs) in the machining process. Nevertheless, the accurate and efficient prediction of frequency response function (FRF) for the workpiece-fixture system remains challenging due to the complicated contact constraints between workpiece and fixture. This paper proposes an analytical solution for the comprehensive FRF analysis of the CTWW-fixture system. Firstly, based on the vector mechanics, the mode shape functions of the workpiece are presented using the classical theory of thin shell. The variable separation method is utilized to deal with the inter-mode coupling of the workpiece. Secondly, the motion equation of the CTWW with fixture constraints is established using analytical mechanics from the viewpoint of energy balance. Finally, the FRFs of the CTWW-fixture system are derived by means of modal superposition. Experimental modal tests verify that the predicted FRFs are in good agreement with the measured curves.

Adaptive CNC Machining Process Optimization of Near- net- shaped Blade based on Machining Error data Flow Control

Adaptive CNC machining process is one of the efficient processing solution for near- net- shaped blade, this study proposes an adaptive computer numerical control (CNC) machining process optimization scheme based on multi-process machining errors data flow control. The geometric and mechanical models of the multi-process adaptive CNC machining process are firstly constructed. The multi-process machining error data flow and the process system stiffness of near- net- shaped blade are then experimentally explored. The machining error flow collaborative control of the near- net- shaped blade multi-process CNC machining is finally realized by the adaptive CNC machining process under the premise of sufficient stiffness of the blade- fixture system. The results show that the dynamic displacement response of the blade multi-process CNC machining process is controlled within 0.007mm. The optimized adaptive CNC machining process based on the multi-process geometric machining error data flow control and the sufficient stiffness of blade- fixture system can realize the multi-process machining error control and high-precision machining of near- net- shaped blade. The process chain of the optimized adaptive CNC machining process is reduced by 87% compared with the low melting point alloy pouring process and 50% compared with adaptive CNC machining process of the twice on-machine measurement on the blade body.

Research on Machining Errors Control by Adaptive CNC Machining Process for Near-Net-Shaped Jet Engine Blades

This study proposes an adaptive CNC machining process based on on-machine measurement to control the machining error of near-net-shaped blades. The multi-source and multi-process machining error transmission model of a near-net-shaped blade is established, and the reduction effect of the machining error transmission chain by the adaptive CNC machining process is qualitatively analyzed based on the machining error transmission flow model. The effects of the adaptive CNC machining process on the positioning benchmark error, machining position error, and machining contouring error are explored based on an experiment for the adaptive CNC machining process. In particular, the ability of the adaptive CNC machining process to cooperatively control the blade position error and the contouring error is discussed in relation to the stiffness of the blade-fixture system. The results show that the adaptive CNC machining process can reasonably reduce the machining errors caused by the positioning benchmark. The final deviation band of the blade body is reduced by 60% based on this adaptive CNC machining process. The adaptive CNC machining process can optimize the contouring error and the position error of the blade tenon root with only the stiffness of the blade-fixture system prerequisite being ensured. The adaptive CNC machining process has the excellent ability to control machining errors to improve the machining quality of the blade.

Application of Alternative Support Fixture System in Vibration Suppression of Thin-Walled Parts

The machining vibration of thin-walled parts affects the quality of the products. Thus, this paper proposes a new alternative support fixture system for vibration suppression of thin-walled parts. The system includes two movable supporting heads, which are periodically repositioned along the machining path in the form of alternating support to support the area close to the cutter, so as to improve the rigidity of the actual machining position of the thin-walled part. Around this new system, a dynamic model is established to analyze the workpiece vibration. Takeing as an example simply suppoted thin-plate, the influence of the supporting head’s location, stiffness coefficient and damping coefficient on vibration suppression are numerically analyzed in this paper. The result of the simulation demonstrates the alternative support fixture system is effective in vibration suppression of thin-walled parts.