Pipe pressure test stress-rupture curve

Sufficient data for HDPE geomembrane materials are not usually available from pipe pressure tests which would enable a direct extrapolation of the stress-rupture curve at 23 °C or 40 °C according to the instmctions of ISO 9080 for small stresses and longer times. The emphasis is on the brittle branch of the stress-rupture curve which results from brittle failures and determines the failure behaviour at small stresses and extremely long service lifetimes. However, one can use the experience accumulated with HDPE materials over many decades (Schulte 1997 Krishnaswamy 2005) and fall back on the extrapolation factors of DIN 16887 or ISO 9080 which were checked by measured stress-rupture data of polyethylene pipes. These factors Ke give the time limits of a permissible extrapolation of the stress-rupture curves in the following sense. Let us assume that hoop stress versus times-to-failure data are measured at several higher test tempera-... 

Pressure, describes how to test individual pipe specimens and is applicable to both thermoplastic and reinforced thermosetting/resin pipe materials. ASTM D2837 requires that a minimum of 18 failure points as well as a specific distribution of failure points be obtained to develop a full hydrostatic stress rupture curve for a material at a specific temperature. This distribution is shown in Table 32.1. 

In 1984, the GRI published a study that compared and ranked several commercially extruded polyethylene piping materials produced after 1971 [64]. Again, the materials tested were identified by codes. Stress rupture tests were performed using methane and nitrogen as the internal pressure medium and air as the outside environment. Several stress rupture curves showed early transitioning from ductile to brittle failure modes. 

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