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Research Papers

Dynamics Modeling and Analysis of Thin-Walled Aerospace Structures for Fixture Design in Multiaxis Milling

[+] Author and Article Information
Mouhab Meshreki

Aerospace Manufacturing Technology Center, National Research Council Canada, 5145 Decelles Avenue, Montreal, QC, H3T 2B2, Canada; Department of Mechanical Engineering, McGill University, 817 Sherbrooke Street West, Montreal, QC, H3A 2K6, Canadamouhab.meshreki@nrc.ca

József Kövecses

Department of Mechanical Engineering and Centre for Intelligent Machines, McGill University, 817 Sherbrooke Street West, Montreal, QC, H3A 2K6, Canadajozsef.kovecses@mcgill.ca

Helmi Attia

Aerospace Manufacturing Technology Center, National Research Council Canada, 5145 Decelles Avenue, Montreal, QC, H3T 2B2, Canada; Department of Mechanical Engineering, McGill University, 817 Sherbrooke Street West, Montreal, QC, H3A 2K6m Canadahelmi.attia@nrc.ca

Nejah Tounsi

Aerospace Manufacturing Technology Center,  National Research Council Canada, 5145 Decelles Avenue, Montreal, QC, H3T 2B2, Canadanejah.tounsi@nrc.ca

J. Manuf. Sci. Eng 130(3), 031011 (May 16, 2008) (12 pages) doi:10.1115/1.2927444 History: Received December 18, 2006; Revised January 23, 2008; Published May 16, 2008

Milling of thin-walled aerospace structures is a critical process due to the high flexibility of the workpiece. Current practices in the fixture design and the choice of cutting parameters rely solely on conservative guidelines and the designer’s experience. This is a result of the lack of computationally efficient dynamic models to represent the dynamic response of the workpiece during machining, and the interaction between the workpiece, fixture and the cutting forces. This paper presents a novel dynamic formulation of typical thin-walled pockets encountered in aerospace structures. It is based on an analytical description of a five-sided pocket using a plate model. An off-line calibration of the model parameters, using global and local optimization, is performed in order to match the dynamic response of the pocket structure. The developed simplified model is based on Rayleigh’s energy method. Various pocket shapes are examined under different loading conditions and compared to finite element (FE) predictions and experimental results. In both cases, the results obtained by the developed model are in excellent agreement. This proposed approach resulted in one to two orders of magnitude reduction in computational time when compared to FE models, with a prediction error less than 10%.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Generalized pocket shape

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Figure 4

Plate representation

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Figure 5

Schematic of the plate/pocket side illustrating the location of the applied force and the output points for the response

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Figure 6

Plate verification comparison of the plate response using FE and the analytical model under sinusoidal load: FE plate (solid line); analytical plate (dotted line)

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Figure 7

Effect of fixture layout on the dynamic response of a pocket

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Figure 8

Asymmetric pocket dimensions

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Figure 9

Asymmetric pocket-plate response versus FE pocket response at different locations under sinusoidal load (300rad∕s) applied at the center of the pocket side/plate: FE pocket side (thick line); calibrated plate (thin line)

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Figure 10

Asymmetric pocket-plate response versus. FE pocket response at different locations under sinusoidal load (3770rad∕s) applied at the center of the pocket side/plate: FE pocket side (thick line); calibrated plate (thin line)

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Figure 11

Measured machining force

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Figure 12

Asymmetric pocket-plate response versus FE pocket response at different locations under actual machining load applied at the center of the pocket side/plate: FE pocket side (thick line); calibrated plate (thin line)

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Figure 13

Correlation of the calibrated torsional spring stiffness and the wall thickness

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Figure 14

Flexible square pocket-plate response versus FE pocket response at different locations under sinusoidal load applied at the center of the pocket side/plate: FE pocket side (thick line); calibrated plate (thin line)

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Figure 15

Dimension representation of the experimental pockets

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Figure 16

Comparison of the responses from experiment, FE model, and plate model for Pocket 1

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Figure 17

Comparison of the responses from experiment, FE model, and plate model for Pocket 2

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Figure 2

A plate representing a sidewall of the pocket

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Figure 3

Flowchart for the integration of the dynamic model in the analysis of fixtures

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