Snap-Fit Joints for Plastics - A Design Guide - MIT

More documents

Recommendations

Info

Both Mating Parts Elastic E With all the examples of snap joints mentioned so far, the stiffer of the two mating parts was assumed to be absolutely rigid. Consequently, the more flexible of the two com-ponents was theoretically deformed by the full amount of the undercut. Where both parts are deformable, however, the sum of these deformations is equal to the undercut, i.e., each deformation is smaller. The mating force and the deformations occurring in two flexible mating parts can be determined most simply by using a graph. For this purpose, the transverse force for each component is determined as a function of deflection on the assumption that the other component is absolutely rigid; a "deflective curve" is then plotted for each mating part as shown in Fig. 29a and b. These "deflection curves" are then superimposed (Fig. 29c). The point of intersection of the two curves gives the actual deflection force P and the deflections y 1 and y 2. With the aid of these quantities P, y 1 and y 2, the individual strains and the mating force can then be determined without diff i c u l t y, as described earlier. Fig. 29: Determination of deformation and transverse force when both mating parts are flexible Page 24 of 26 Snap-Fit Joints for Plastics - A Design Guide 25
a dimensions b dimensions c distance between outer fibre and neutral fibre d diameter at the joint di internal diameter do external diameter Eo modulus of elasticity (intrinsic tangential modulus) ES secant modulus F friction force G shear modulus H height thickness at the root IP polar moment of inertia K geometric factor for ring segments 1 length, length of lever arm N normal force due to insertion P deflection force R resultant insertion force r radius t wall thickness W mating force X geometric factor for annular snap joint index W=shaft index N=hub y undercut, deflection Z axial section modulus 26 Symbols F Health and Safety Information � angle of inclination �' return angle � distance of snap-fitting groove from the end � strain �Pm maximum allowable strain �ult strain at break �y yield strain � angle of twist � shear strain µ friction coefficient � Poisson's ratio P angle of repose � stress � arc angle of segment Appropriate literature has been assembled which provides information pertaining to the health and safety concerns that must be observed when handling Bayer products, appropriate industrial hygiene and other safety precautions recommended by their manufacturer should be followed. Before working with any product mentioned in this publication, you must read and become familiar with available information concerning its hazards, proper use and handling. This cannot be overemphasized. Information is available in several forms, such as Material Safety Data Sheets and Product Labels. Consult your Bayer Representative or contact the Product Safety Manager for the Bayer MaterialScience within Bayer’s Corporate Occupational and Product Safety Department, Bayer Materi a l S c i e n c e L L C, 100 Bayer Road, Pittsburgh, PA 15205 -9741, (412) 777-2000. Page 25 of 26 Snap-Fit Joints for Plastics - A Design Guide
Page 2 and 3: The illustration above shows a phot
Page 4 and 5: Types of snap joints A wide range o
Page 6 and 7: Torsion snap joints The tor-sion sn
Page 8 and 9: Cantilever Snap Joints B Design Hin
Page 10 and 11: Geometric factors K and Z for ring
Page 12 and 13: Deflection force Using the equation
Page 14 and 15: Fig. 17: Relationship between defle
Page 16 and 17: Calculation example I snap-fitting
Page 18 and 19: Torsion Snap Joints C Deflection In
Page 20 and 21: Annular Snap Joints D Permissible u
Page 22 and 23: If the tube is rigid and the hollow
Page 26: The manner in which you use and the

Snap-Fit Joints for Plastics - A Design Guide - MIT

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?