Determination of the Paris’ law constants by means of infrared thermographic techniques

Determination of the Paris’ law constants requires the continuous measure of the crack length. This measure has usually been performed using methods based on electric potential differences or by means of correlations between crack length and the compliance of the specimen.

Bearing in mind that the crack tip undergoes a temperature rise due to the corresponding stress concentration and the generation and growth of a plastic zone, it is possible, using infrared thermographic techniques, to quantify the crack growth. Thus, in this paper, the fatigue crack propagation behaviour of a polyamide has been characterised by determining the Paris’ law constants with the aid of thermographic tools. The values obtained by means of this methodology have been compared with those resulting from the use of conventional measurement techniques.