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RESEARCH PAPERS

Development of Analytical Model of Cantilever Hook Performance

[+] Author and Article Information
Gaurav Suri

 Deere & Co., Des Moines Works, 825 SW Irvindale Street, Ankeny, IA

Anthony F. Luscher

 The Ohio State University, 204 ABB Building 1, 650 Ackerman Road, Columbus, OH

J. Mech. Des 128(2), 479-493 (Jun 19, 2005) (15 pages) doi:10.1115/1.2168468 History: Received March 25, 2004; Revised June 19, 2005

With an increase in the use of polymeric materials in commercial products, snap-fits are attracting increased attention as alternatives to other, more traditional, joining methods. The field of snap-fit design is receiving greater attention as an engineering and research activity. Research in this area has focused on the development of performance models for individual features and heuristics for the design of snap-fit assemblies. An improved analytical model for cantilever hook snap-fit features is developed in this study. The modeling approach is a significant improvement over currently available analytical design equations. The model captures the effect of a snap-fit’s catch in causing contact forces to be offset from the beam’s neutral axis. Beam rotation, influence of axial force, and moment components on beam deformation are also incorporated by formulating a set of equations that model the system in its deformed configuration. The equation system is iteratively solved for several such configurations to model insertion and retention processes for snap-fits. The axial force component, which has been hitherto ignored in analytical design equations, is found to have significant effect on predicted snap-fit performance. The design space of cantilever hook features is explored by varying input design parameters. The model shows excellent agreement with experimental results, especially for low and medium retention angle snap-fit features. However, for high retention angle snap-fits, more accurate governing equations are required. Suggestions for possible improvements and future research directions are provided.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Cantilever hook and mating part

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Figure 2

Loss-of-engagement failure in cantilever hook snap-fits

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Figure 3

Cantilever hook model illustration

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Figure 4

Algorithmic flowchart of analytical cantilever hook model

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Figure 5

Typical model results of for insertion, illustrating the variation in different quantities during the insertion process

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Figure 6

Typical cantilever hook model predictions for insertion and retention, respectively

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Figure 7

Comparison of typical insertion force curves obtained using the two different beam formulations adopted in this work. Relevant catch dimensions were y=2.54mm, α=45deg, β=87deg, and μ=0.4.

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Figure 8

Comparison of different output variables for insertion obtained using the two different beam formulations. Relevant catch dimensions were y=2.54mm, α=45deg, β=87deg, and μ=0.4.

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Figure 9

Typical retention force curves for two cantilever hooks with different retention angles, obtained using the two beam formulations. Relevant catch dimensions are: y=1.524mm, α=45deg, μ=0.1, and β=60deg, 89deg, respectively.

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Figure 10

Comparison of different output variables for retention obtained using the two different beam formulations. Relevant catch dimensions were y=2.54mm, α=45deg, β=89deg, and μ=0.1.

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Figure 11

Predicted influence of various design quantities on insertion force curves for cantilever hook features. Results incorporate effect of Fa.

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Figure 12

Predicted influence of various design quantities on retention force curves for cantilever hook features. Results incorporate effect of Fa.

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Figure 13

Comparison of model predictions to experimental test results for a low retention angle, low catch offset cantilever hook

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