Patent ID: 6935185

Claim:
An accelerated method of determining or predicting failure time in polyethylene materials, comprising selecting an anticipated or desired failure time for a polyethylene material specimen; conducting a PENT (Pennsylvania Notched Test) on the specimen according to ASTM F1473-01 for a time equivalent to the time at Min δ R , wherein Min δ R =minimum displacement rate in millimeters and time is measured in hours, that corresponds to the anticipated or desired failure time; and either determining that, (a) if failure has occurred, PENT failure time is before the anticipated or desired failure time, and (b) if failure has not occurred, cryogenically fracturing the specimen to determine whether slow crack growth has occurred, such that (i) if slow crack growth has occurred, PENT failure time is greater than time at Min δ R but less than anticipated or desired failure time, and (ii) if slow crack growth has not occurred, PENT failure time is greater than anticipated or desired failure time; or predicting PENT failure time by using either Min δ R or time at Min δ R , as appropriate, in one of the following formulas: Failure Time=0.2667(Min δ R ) −0.9401 [Formula 1] wherein R is 0.9916; and Failure Time=3.8272 (time at Min δ R ) 1.0348 [Formula 2] wherein R is 0.9805.