Stress Relaxation as Used in Underhood Component Design Verification

Bench testing is a critical step in the design verification process of underhood components. The challenge to the test engineer in developing a component test is to both simulate in-use conditions and to establish useful and measurable performance criteria.

The primary performance criteria for a sealing system, as in a rocker cover, is its ability to maintain a minimum sealing force necessary to prevent leakage. Compressive stress relaxation has been shown to be an important test for evaluating sealing materials and through the ASTM E-328 test method, a complete sealing system assembly can be evaluated.

A test system has been developed to measure compressive stress relaxation of actual components and component assemblies under a variety of environmental conditions. The system was used to verify the design of a rocker cover assembly for its ability to maintain a minimum sealing force under simulated engine operating conditions.