CRACK-GROWTH MEASUREMENTS ON COMPONENTS UNDER CYCLIC LOADING - COMPARISON OF DIFFERENT METHODS

The cyclic crack growth behaviour was measured by means of d.c. potent ial drop, a.c. potential drop, ultrasonic and crack-opening displaceme nt (COD) methods. The methods were applied to component tests on strai ght pipes with an outer diameter of approximately 800 mm and a wall th ickness of approximately 50 mm. The pipes were subjected to constant i nternal pressure (about 15 MPa) and either an alternating (or pulsatin g) or a quasi-static bending moment using d.c. potential drop, a.c. po tential drop, ultrasonic and flaw-opening (COD) methods. The efficienc y of the particular methods has been proved by comparison with fractog raphical analysis of the fracture surfaces.