Our laboratories use two main techniques for fatigue testing - tensile and flexural.
Tensile Fatigue Testing
Tensile fatigue can be carried out to internal procedures using dumbbell specimens which can be moulded or machined. Testing is carried out by applying a cyclic stress between zero and the target stress; typical conditions are a square wave at 1Hz.
Flexural Fatigue Testing
Flexural fatigue can be carried out to internal procedures using rectangular section specimens. These can be moulded or machined using our in-house equipment. Testing is carried out by applying a cyclic stress in four point bend between zero and the target stress; typical conditions are a square wave at 1Hz.
A range of target stresses are used to generate failure times from 100s to 106s. This generates a plot of fatigue stress versus log failure time.
- A minimum of 20 data points are required to produce a fatigue plot.
- Plots can be generated over a range of temperatures up to 80°C.
Using fatigue testing to predict longer failure
It's possible to use this data to predict when failure would occur during an extended period. To do this, the fatigue versus log failure time needs to be produced over at least three different temperatures. The failure prediction is then made using the lower temperature by time-temperature superposition.