Additional testing

Fatigue crack propagation

ASTM E647

The test is sub-contracted to a vendor in the US and will be conducted on an Instron closed-loop servo-hydraulic test machine using a constant load amplitude, with a minimum-to-maximum load ratio R= 0.1. All tests will be conducted in ambient air at a test frequency of 3 Hz. A compressed air jet will be used to keep the specimen cool throughout testing.

The loading waveform will be sinusoidal. Measurement of crack length, a, will be made with a travelling microscope and recorded relative to the number of loading cycles, N, and will be used to determine the fatigue crack growth rate, delta a/delta N.

The crack length and the number of cycles will initially be recorded approximately every 0.2 mm. When the 0.2 mm of crack growth is reached in less than 100 cycles, the measurements will be taken at 0.1 mm intervals.