Ultra High Molecular Weight Polyethylene (UHMWPE) has been successfully used as a bearing material in total joint arthroplasty for the last 4 decades [1] but about 5%–10% of the implants undergo revision surgery in the first 10 years of implantation [2]. Crack initiation from a stress-concentration design feature (e.g., a sharp corner of a locking mechanism on an acetabular component) has been observed to lead to catastrophic failure in-vivo [3]. Therefore, it is important to understand crack initiation from clinically relevant notches to mitigate the risk of component fracture. UHMWPE is a semi-crystalline polymer and little is known about the physical mechanisms governing crack tip phenomena. The time dependent theoretical expression of fracture mechanics indicates that the critical fracture energy (Jc) varies with crack initiation time (ti) with an exponent ‘n’ (Equation 1).

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