Purpose of the test
Fatigue tests determine the long-term behavior of foam under constant mechanical load. For example, it represents the load applied to a vehicle seat when a car is being driven.
A fatigue test is described in ISO 3385, ASTM D3574 and in many factory standards. Indentation hardness and specimen thickness are first measured on an unloaded seat cushion. In the second step the foam is loaded several tens of thousands of times. This load can be applied under normal climate conditions or under defined humidity and temperature conditions. Following continuous load application and after a certain holding period, the specimen thickness and compressive stress value are measured again. The results are the specimen reduction in hardness and thickness.
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For fatigue tests, ZwickRoell offers an electromechanical testing machine that permits high loading rates. This testing machine can be used for determining both indentation hardness and compression stress value and for repeated loading.