3 compares the failure time behavior, using the standard PENT and CDNT geometries, with respect to [M.sub.e].
Figure 4 shows the failure times measured using the PENT and CDNT test as function of the probability of tie molecules formation, evaluated using the PSP2 parameter.
Failure times using both geometries, PENT and CDNT, were plotted versus [G.sub.p] in Fig.
Two different geometries, the standard and an alternative called CDNT, were successfully employed in the PENT test to evaluate the failure times of ten polyethylene resins in the range of PE-80 and PE-100 degrees.
3, the CDNT specimen is a rectangular bar with a symmetrical notch machined around the circumference at the midpoint.
CDNT samples were prepared from three different Australian pipe grade materials and two different PE materials from USA.
CDNT specimens were produced by regrinding PE pipes at room temperature and then comppession molding reground material into rectangular plaques.
Following the procedure outlined by Pandya and Williams , a circumferential notch was introduced into molded CDNT specimens with a single-point cutting tool of tip radius [less than or equal to]20 [micro]m.
Figure 4 shows how the time to failure in the CDNT test varies with static applied stress for the different PE materials assessed.
5 show scanning electron images of the failure ligament from CDNT tests on PE 3 (AUS) and PE 1 (AUS) samples.
While craze strength data was readily obtained using the CDNT test, the problem is to relate the uniform tensile stress state that exists in CDNT specimens to the actual stress state in the craze zone that is formed in other component geometries.
Following the reasoning outlined earlier, the time dependence of the reference stress is assumed to be the same as the time dependence of craze stress determined using the CDNT test.