Offshore Technology Research Center

 

OTRC Project Summary

Project Title:

A Finite Element Study of Crack Initiation and Growth in Hyperelastic Materials

Prinicipal Investigators:

Eric Becker

Sponsor:

National Science Foundation

Completion Date:

March 1994

Final Report ID#

B53(Click to view final report abstract)

Many engineering applications require the use of elastomers as structural components.  One important application of elastomers as vital structural elements is in elastomeric bearings.  A bearing may consist of a single rubber pad or the bearing may be laminated in which case the rubber pads are layered with steel shims.  Elastomeric bearings are used as connections between a solid rocked motor casing and the motor nozzle.  The bearings allow the nozzle to gimbal which subject to high compressive loads due to rocket thrust.  Bearings are also used in deep-water tension leg oil platforms.   In this case, the bearings do no allow the tendons connecting the platform to the ocean floor to carry moments as the platform sways with the current.  In civil engineering applications, elastomeric bearings are used to isolate the deformations of an elevated road from the supporting structure. In all of these examples, the service life of the elastomeric components may b limited by the growth of fatigue cracks due to cyclic compressive and shear loading.  Thus, an understanding of crack initiation and growth in elastomers is imperative for accurate prediction of the component lifetime.

Determining the fatigue life of elastomeric components is a difficult task due to the highly non-linear aspects of the problem including large strains, contact and friction, and non-linear material behavior.  An investigation was conducted to examine the capabilities and limitations of commercial finite element codes in predicting crack initiation and growth in elastomeric components. Also included in this analysis are methods of modeling cracks and crack growth as well as techniques for interpreting the finite element output.  The studies contained in this project focus on elastomeric disks loaded in pure compression.

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