New total joint replacement prostheses often use ultra-high molecular weight polyethylene (UHMWPE) in load bearing components. Design engineers need to understand the stress and strain distributions in order to extend device life.
PolymerFEM used the PolyUMod® Three Network constitutive material model to represent the UHMWPE and determine the stresses and deformations within a total knee replacement component. Many medical devices, such as artificial discs and hip implants, contain components made from UHMWPE due to its good mechanical and wear characteristics. Like all thermoplastics, this material can undergo yielding and viscoplastic flow. The material can also be degraded due to wear and fatigue loading. These characteristics of the material response are important for the function and lifetime of the medical device.
The improved PolyUMod constitutive model provided more accurate design stresses and strains. The above figure shows the stress contours in the UHMWPE bearing component.