TWI Industrial Member Report Summary 92/1979
By S Tsuru and S J Garwood
The time dependent ductile fracture of two line pipe steels to API 5LX-X65 was investigated. Tests were carried out under both load and displacement control.
Under constant load conditions, specimens showed time dependent crack growth at loads above the load necessary for the initiation of ductile tearing. There would appear to be a threshold load below which failure of the testpieces does not occur even though some time dependent crack extension may result.
A static load-displacement curve is assumed in order to discuss the mechanism of time dependent ductile fracture. Using this approach the importance of load in time dependent fracture is emphasised.
Under constant displacement conditions, no obvious time dependence was observed. This indicates that time dependent ductile fracture does not occur under fixed grip conditions for the materials employed in this programme of tests.