Effect of Specimen Geometry on the Predicted Mechanical Behavior of Polyethylene Pipe Material¹

The primary objective of the present paper is to depict the mechanical behavior of high density polyethylene (HDPE) pipes under different loading conditions with different specimen geometries to provide the designer with reliable design data relevant to practical applications. Therefore, it is necessary to study the effect of strain rate, ring configuration, and grip or fixture type on the mechanical behavior of dumb-bell-shaped (DBS), and ring specimens made from HDPE pipe material. DBS and ring specimens are cut from the pipe in longitudinal and circumferential (transverse) directions, respectively. On the other hand, the ring specimen configuration is classified into two types; full ring (FR), and notched ring (NR) (equal double notch from two sides of NR specimen) specimens according to ASTM D 2290-12 standard. Tensile tests are conducted on specimens cut out from the pipe with thickness of 10 mm at different crosshead speeds (10–1000 mm/min), and ambient temperature, T_a = 20 °C to investigate the mechanical properties of DBS and ring specimens. In the case of test specimens taken from the longitudinal direction from the pipe, a necking phenomenon before failure appears at different locations along the gauge section. On the other hand, the fracture of NR specimens occurs at one notched side. The results demonstrated that the NR specimen has higher yield stress than DBS and FR specimens at all crosshead speeds. The present experimental work reveals that the crosshead speed has a significant effect on the mechanical behavior of both DBS and ring specimens. The fixture type plays an important role in the mechanical behavior for both FR and NR specimens at all crosshead speeds.