Edwards, Broutman, Choi
Posters - Additional Information # 2001 Munich
The Alternate Methods Committee of the Plastics Pipe Institute’s Hydrostatic Stress Board (HSB) has completed development of an alternate method for determining the hydrostatic design basis (HDB) for plastic piping materials. The initial work was reported at Plastic Pipes X, in Sweden in 1998.1 An ASTM test method has also been developed, ASTM F 2018, “Standard Test Method for Time-to-Failure of Plastics Using Plane Strain Tensile Specimens.” This test method generates a Strength Design Basis or SDB, which will be included in PPI TR-3 and TR-4 for moulding applications. This work is based on a method developed by Choi and Broutman,2-4 and has been successful in generating an SDB that is the same as the HDB 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 uni-axial tension at different stress levels until failure (creep-rupture). The data are then analysed per ASTM D2837 or ISO 9080, similar to hydrostatic pressure test data.
