||Gasket Designers, Resilient-Material and FEA Specialists Sought to Develop Standard
Task Group F03.20.20 on Dynamic Spring Rate (DSR) invites stakeholders to participate in the creation of a new standard test method that will predict and quantify DSR. The proposed Standard Test Method for Determination of Dynamic Spring Rate of Gasket Materials will help to comparatively evaluate materials and predict real-world performance over an extended period of time.
The task group seeks participation from gasket designers and individuals with expertise in resilient materials and predictive techniques such as FEA [finite element analysis].
For the purpose of the F03.20.20 task group, DSR, or resilience, can be defined as the ability of a gasket material to accommodate Z-axis direction motion between two flanges, said the task group chairman, Stephen Bond, Ph.D., manager, Materials Development Lab, Federal-Mogul Sealing Systems, Skokie, Ill. Continuous load-deflection-recovery type tests (at a constant strain rate) are an improvement over single point compressibility/recovery. Dynamic spring rate testing further refines material evaluation by introducing cyclic loading and unloading at frequencies approaching real world applications.
Task group member John Michna, programmer analyst, Technical Systems and Services, Federal-Mogul Sealing Systems, said real-world performance is the accurate simulation of the actual operating environment of the gasket or sealing member, and the determination of how the gasket will behave under these conditions.
Bond said the proposed method will foster improved design. This method will help gasket design engineers select gasket materials with more predictive in-service properties, he said, permitting development of more robust designs with fewer iterations.
There may be no such thing as an absolute 'good or 'bad dynamic spring rate, he explained. In cylinder head gaskets for example, materials with low spring rates (relatively large motion at a given load) tend to crack combustion seals ('armors).
Gasket design can accommodate practically any kind of spring rate, Bond continued. What appears more important is the constancy or stability of the spring rate. After an initial settling in period, how well does a gasket material maintain a constant dynamic spring rate? Spring rate stability is a good predictor of long term gasket sealing performance.
The task group will focus on predictive testing, rather than more traditional test methods related to quality control. New methods proposed will help predict and quantify functional performance in defined environments, task group members said.
To participate or obtain further technical information, contact Stephen Bond, Ph.D., Materials Development Lab, Federal-Mogul Sealing Systems, Skokie, Ill. (phone: 847/568-2387). Committee F03 meets April 23-25 in San Antonio and Oct. 15-17 in Norfolk, Va. For meeting or membership details, contact Jim Olshefsky, ASTM technical committee manager (phone: 610/832-9714). //
Copyright 2002, ASTM