Gencur S J, Rimnac C M, Kurtz S M
Musculoskeletal Mechanics and Materials Laboratories, Departments of Orthopaedics and Mechanical and Aerospace Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7222, USA.
Biomaterials. 2003 Oct;24(22):3947-54. doi: 10.1016/s0142-9612(03)00277-1.
Highly crosslinked UHMWPEs have demonstrated improved in vitro wear properties; however, there is concern regarding loss of fracture resistance and ductility. The goals of this study were to evaluate the micromechanisms of failure under uniaxial tension and to determine the effect of gamma radiation-induced crosslinking and post-irradiation thermal processing on the estimated fracture toughness (Kc) of UHMWPE. Kc was estimated for two conventional and two highly crosslinked UHMWPE materials from tensile tests. A 32% decrease in Kc was found following crosslinking at 100kGy. The highly crosslinked materials also exhibited less ductile fracture behavior. Kc was slightly dependent on displacement rate but was insensitive to changes in crystallinity (and thus, to thermal processing). The same basic failure mechanism, microvoid nucleation and slow coalescence followed by comparatively rapid fracture after the defect reached a critical size, was observed for all of the conventional and highly crosslinked UHMWPE specimens. These observations will be used in the development of a theoretical failure model for highly crosslinked UHMWPE, which, in conjunction with a validated constitutive model, will provide the tools for predicting the risk of failure in orthopaedic components, fabricated from these new orthopaedic bearing materials.
高度交联的超高分子量聚乙烯（UHMWPE）已表现出改善的体外磨损性能；然而，人们担心其抗断裂性和延展性会降低。本研究的目的是评估单轴拉伸下的失效微观机制，并确定γ辐射诱导交联和辐照后热处理对UHMWPE估计断裂韧性（Kc）的影响。通过拉伸试验估算了两种传统和两种高度交联的UHMWPE材料的Kc。在100kGy交联后，发现Kc降低了32%。高度交联的材料还表现出较少的韧性断裂行为。Kc略微依赖于位移速率，但对结晶度的变化（因此，对热处理）不敏感。对于所有传统和高度交联的UHMWPE试样，观察到相同的基本失效机制，即微孔形核和缓慢聚结，随后在缺陷达到临界尺寸后相对快速地断裂。这些观察结果将用于开发高度交联UHMWPE的理论失效模型，该模型与经过验证的本构模型相结合，将为预测由这些新型骨科轴承材料制造的骨科部件的失效风险提供工具。
