Fatigue Test

In the fatigue test the long-term behavior of a foam under constant mechanical loading is tested, representing for example the loading of a vehicle seat during a journey.
 
This test is described in ISO 3385 and several in-house standards. First the indentation hardness and specimen thickness of the unloaded seat cushion are measured. Next the foam is loaded – tens of thousands of times. This can take place in a normal climate or under specified moisture and temperature conditions. Following long-term loading and after a holding period the specimen thickness and compression stress value are measured again. The results are hardness loss and thickness loss.
 
Zwick produces an electromechanical testing machine which permits suitably high rates of loading and can be used both for determining indentation hardness and compression hardness and for repeated loading.