Material Behavior of UHMWPE

Conventional and highly crosslinked UHMWPE materials exhibit similar qualitative behavior as a result of the underlying similarities of the material microstructures. In this section we examine the behavior of four different UHMWPE materials to illustrate the characteristic material response of UHMWPE. This data will also be used as the basis for the development of material models in the rest of the review. Two of the four materials were conventional UHMWPE and two were highly crosslinked UHMWPE. All materials were created from the same lot of ram-extruded GUR 1050 (Eigure 14.1). 

The first conventional UHMWPE material was a control, virgin, unirradiated material. The second conventional UHMWPE material was gamma-radiation sterilized in nitrogen with a dose of 30 kGy (referred to as 30 kGy, Y-N2). The two highly crosslinked UHMWPEs were both gamma irradiated with an absorbed dose of 100 kGy. One of the crosslinked materials was heat treated until the specimen center reached 110°C for 2 hours (referred to as 100 kGy, 110°G). The second was heat treated at 150°G for 2 hours (referred to as 100 kGy, 150°G). The degree of crystallinity of the four material types was determined by differential scanning calorimetry (DSC), see Table 14.2. 

Representative experimental uniaxial tension data for the four UHMWPE materials. The tension experiments were [jerformed at a displacement rate of 75 mm/minute. 

Influence of different strain rates on the cyclic compression behavior of GUR 1050 (100 kCy, I 10°C). 

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Under what circumstances might an analyst consider using linear elasticity to simulate the material behavior of UHMWPE ... 

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