A B S T R A C T This paper describes the experimental studies carried out on cracked austenitic stainless steel pipe and pipe welds under bending loads. Pipe welds were produced by gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW). Fracture resistance curves for pipe and pipe welds were compared. Results indicate that the fracture resistance of pipe and pipe weld (GTAW) is comparable but that of pipe weld (GTAW+SMAW) is inferior. Cracks do not deviate from their original plane during propagation as observed in the cases of carbon steel pipe and pipe welds. The fracture resistance of pipe welds does not depend on the loading histories to which it has been subjected prior to fracture test. Initiation and crack propagation were observed prior to the maximum moment. An existing limit load expression is applicable for the pipe base material but gives non-conservative results for the pipe welds. Multiplication factors have been suggested for the pipe welds for evaluation of limit loads using the existing expression. Fracture resistance for the pipe and compact tension specimens have also been compared for base material and welds.Keywords austenitic stainless steel; gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW); fracture resistance; limit load; pipe; pipe welds.
I N T R O D U C T I O NModern design and safety considerations require satisfaction of leak-before-break (LBB) criteria for high-energy piping system of nuclear power plants. Evaluation of the fracture the resistance of components and its point of instability is necessary for the demonstration of the safety case. High-energy piping systems in these plants use ductile and strain hardening materials. Fracture resistance of such materials can be characterized by the J-integral parameter, which takes into account extensive plastic deformation ahead of the defect under loading condition. A component integrity test program was started in Bhabha Atomic Research Centre (BARC), Mumbai to evaluate the application of LBB design criteria to the main heat transport system piping of the advanced heavy water reactors. Generally the fracture resistance of the material is evaluated according to the guidelines given in ASTM E1820 1 for semi ductile materials. But use of test results obtained using compact tension specimen, as in the ASTM E1820 standard, in component analysis remains subjective for Correspondence: P.K. Singh. E-mail: pksingh@barc.gov.in highly ductile materials because of the following reasons. Firstly, minimum thickness requirement for the determination of valid J IC is very high whereas pipes are usually much thinner. Secondly, the range of stable crack growth obtained from the standard compact tension (CT) or three-point bend (TPB) specimens is a few millimetres, which is small compared to that observed in components. Thirdly, there is a considerable range of scatter in the fracture toughness data of welds in the standard specimen test because of limited stable crack growth. Austenitic stainless steel material is one ...