New method to evaluate fracture toughness of case-hardened steel

A new method is proposed for the evaluation of the fracture toughness of case-hardened steel. The proposed method uses the concept of the elastic unloading compliance method. The principle of this method is that cracks with different lengths will show different elastic unloading compliance values, and vice versa. Lastly, the correctness of the proposed method is verified by measuring the elastic unloading compliance value using a series of specimens with given crack lengths.