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Research Papers

Development of a New Model for the Varying Dynamics of Flexible Pocket-Structures During Machining

[+] Author and Article Information
Mouhab Meshreki

 Aerospace Manufacturing Technology Centre, National Research Council Canada, 5145 Decelles Avenue, Montreal, Quebec, Canada, H3T 2B2mouhab.meshreki@cnrc-nrc.gc.ca

Helmi Attia

 Fellow ASME Aerospace Manufacturing Technology Centre, National Research Council Canada, 5145 Decelles Avenue, Montreal, Quebec, Canada, H3T 2B2, Department of Mechanical Engineering, McGill University, Montreal, Quebec, Canadahelmi.attia@cnrc-nrc.gc.ca

József Kövecses

Mem. ASME Department of Mechanical Engineering and Centre for Intelligent Machines,  McGill University, 817 Sherbrooke St. West, Montreal, Quebec, Canada H3A 2K6jozsef.kovecses@mcgill.ca

J. Manuf. Sci. Eng 133(4), 041002 (Jul 20, 2011) (14 pages) doi:10.1115/1.4004322 History: Received March 01, 2011; Revised May 16, 2011; Published July 20, 2011; Online July 20, 2011

Many of the aerospace components are characterized by having pocket-shaped thin-walled structures. During milling, the varying dynamics of the workpiece due to the change of thickness affects the final part quality. Available dynamic models rely on computationally prohibitive techniques that limit their use in the aerospace industry. In this paper, a new dynamic model was developed to predict the vibrations of thin-walled pocket structures during milling while taking into account the continuous change of thickness. The model is based on representing the change of thickness of a pocket-structure with a two-directional multispan plate. For the model formulation, the Rayleigh–Ritz method is used together with multispan beam models for the trial functions in both the x- and y-directions. An extensive finite element (FE) validation of the developed model was performed for different aspect ratios of rectangular and nonrectangular pockets and various change of thickness schemes. It was shown that the proposed model can accurately capture the dynamic effect of the change of thickness with prediction errors of less than 5% and at least 20 times reduction in the computation time. Experimental validation of the models was performed through the machining of thin-walled components. The predictions of the developed models were found to be in excellent agreement with the measured dynamic responses.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Illustrative 3D sketch of aerospace structural components

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Figure 2

Illustration for the representation of a pocket with a multispan plate

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Figure 3

Illustration of the change of thickness formulation for the MS-VT model

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Figure 4

Effect of nonsymmetric and symmetric change of thickness on the response of a rectangular plate

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Figure 5

Representation of the dimensions of the generalized pocket used for the validation of the MS-VT model

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Figure 6

Comparison of the responses of pocket 6 predicted by the FE and the MS-VT models under a sinusoidal load (1256 rad/s)

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Figure 7

Comparison of the responses of pocket 6 predicted by the FE model and the MS-VT model for Case A: Vertical strip

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Figure 8

Comparison of the responses of pocket 6 predicted by the FE model and the MS-VT model for Case D: L-shaped strip

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Figure 12

The results for the displacements of test case 4.0-3.2, at a tool-path depth of 20.0 mm

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Figure 11

The results for the displacements of test case 3.2-2.4, at a tool-path depth of 16.0 mm

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Figure 10

The results for the displacements of test case 3.2-2.4, at a tool-path depth of 10.0 mm

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Figure 9

Dimensions of the rectangular pocket in millimeter

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