Broutman, Edwards, Shah, Palermo
Design & Testing # 1998 Gothenburg
The Alternate Methods Committee of the Plastics Pipe Institute's Hydrostatic Stress Board (HSB) has initiated development of an alternate method for determining the hydrostatic design basis (HDB) for plastic piping materials. After reviewing several test methods, the plane-strain tensile method, developed by Choi and Broutman [1,2,3], was chosen as the test method most likely to succeed in generating the same HDB as determined from testing pressurized pipe specimens. The plane-strain tensile specimen is grooved on both faces to create a biaxial stress in the groove area. The biaxial stress achieved in the test specimen closely approximates the biaxial stress ratio found in pressurized pipe specimens. The samples are loaded in uniaxial tension at different stress levels until failure (creep-rupture). The data are then analyzed per ASTM D2837 or IS0 9080, similar to hydrostatic pressure test data. In order to demonstrate the general applicability of this method to piping materials, three different materials were chosen for the test program, each having a PPI listing at both room temperature and an elevated temperature. A high density polyethylene (HDPE), a CPVC, and a polyamide (PA) 11 were selected as the materials for this study. Testing was performed at 23°C for all three materials, and at 60°C for the HDPE, 82.2"C for the C ~ V C , and 82.2"C for the PA 11, for a total of six materialitemperature conditions. The test data are presented and compared to the pipe test data generated previously on the respective pipe specimens.
