Nano and Microscale Mechanisms of Fatigue, Fracture and Wear in Polyethylene

聚乙烯疲劳、断裂和磨损的纳米和微观机制

• 批准号: 0505272
• 负责人: Lisa Pruitt
• 金额: $ 30.99万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2010-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0505272&HistoricalAwards=false
• 关键词: Nano; Microscale; Mechanisms; Fatigue; Fracture

Nano and Microscale Mechanisms of Fatigue, Fracture and Wear in PolyethylenePI: Lisa Pruitt, Departments of Bioengineering and Mechanical Engineering, UC BerkeleyCollaborator: Anuj Bellare, Department of Orthopedic Surgery, Harvard Medical SchoolAbstractThis research establishes the fundamental link between microstructure and cyclic damage mechanisms in advanced polymers used in structural and medical applications. An illustration of this problem with worldwide significance is found in total joint replacements where ultra-high molecular weight polyethylene (PE) is used as the bearing surface and serves to replace diseased or damaged cartilage. In this application, PE sustains large cyclic contact stresses as the joint is articulated and the polymer is set in motion against a polished metal or ceramic component. In these prostheses, the polyethylene component usually articulates against a metallic or ceramic component, which leads to the generation of wear debris. Submicrometer size particulate debris is known to cause bone resorption and implant loosening, necessitating early revision surgery to replace the implant. In recent years, radiation crosslinking has emerged as a processing technique that can dramatically decrease the generation of particulate wear of polyethylene. This has led to its implementation in the processing of acetabular cups for total hip replacement prostheses. However, there are concerns about its use in knees and shoulders where high contact stresses are expected. This concern is valid as radiation crosslinking decreases certain mechanical properties, such as ultimate tensile properties, fracture toughness and resistance to fatigue crack propagation. Fatigue strength is the most important property from a clinical standpoint since these load-bearing components are subjected to cyclic loads. In this study, the investigator and her collaborator are using novel processing conditions that combine radiation crosslinking with high pressure, gas assisted processing techniques to improve the performance of PE as a bearing material. The processing of polyethylene using a pressurized soluble gas leads to improvement in fusion of polyethylene resin particles and improves tensile, fracture and fatigue properties. This is coupled with crosslinking that provides wear resistance. In this work, the researchers (I) fabricate bulk components of polyethylene using (a) radiation crosslinking, (b) gas-assisted processing utilizing carbon dioxide and an inert diluent and (c) high pressure processing in the presence of an inert gas, and combinations thereof; (II) characterize the morphology at the nano- and micro- scales and (III) evaluate concomitant mechanical properties of all types of polyethylene by conducting short term tensile and fracture toughness tests, long-term fatigue tests, and measurement of the tribological properties at nanoscale and microscale using nanoindentation and wear tests. The novelty of this interdisciplinary work stems from multiscale experimental studies that yield insight into the fundamental mechanisms of fatigue, fracture and wear in advanced polymers such as PE. The intellectual merit of this work is the systematic evaluation of morphology and micromechanisms of fatigue, fracture, and wear at the nanoscale and microscale levels. The broad impact of this work extends to clinical orthopedics, polymer materials science, mechanical engineering and bioengineering. This study involves the synergy of bioengineering, mechanical engineering, materials science and medicine, and provides educational opportunities at all levels including undergraduates, graduates, postdocs, and faculty.

聚乙烯疲劳、断裂和磨损的纳米和微观机制PI：Lisa Pruitt，加州大学伯克利分校生物工程和机械工程系合作者：Anuj Bellare，哈佛医学院整形外科系摘要这项研究建立了先进的微观结构和循环损伤机制之间的基本联系用于结构和医疗应用的聚合物。这个具有世界意义的问题的一个例证是在全关节置换术中发现的，其中超高分子量聚乙烯（PE）被用作支撑表面并用于替换患病或受损的软骨。在此应用中，当接头铰接且聚合物相对于抛光金属或陶瓷部件运动时，PE 承受较大的循环接触应力。在这些假体中，聚乙烯组件通常与金属或陶瓷组件进行关节连接，这会导致磨损碎片的产生。已知亚微米尺寸的颗粒碎片会导致骨吸收和植入物松动，因此需要早期修复手术来更换植入物。近年来，辐射交联作为一种加工技术出现，可以显着减少聚乙烯颗粒磨损的产生。这导致其在全髋关节置换假体的髋臼杯加工中得到应用。然而，人们担心它在预计会产生高接触应力的膝盖和肩膀上的使用。这种担忧是合理的，因为辐射交联会降低某些机械性能，例如极限拉伸性能、断裂韧性和抗疲劳裂纹扩展能力。从临床角度来看，疲劳强度是最重要的特性，因为这些承载部件要承受循环载荷。在这项研究中，研究人员和她的合作者正在使用新颖的加工条件，将辐射交联与高压气体辅助加工技术相结合，以提高 PE 作为轴承材料的性能。使用加压可溶性气体加工聚乙烯可改善聚乙烯树脂颗粒的熔合，并改善拉伸、断裂和疲劳性能。这与提供耐磨性的交联相结合。在这项工作中，研究人员 (I) 使用 (a) 辐射交联、(b) 利用二氧化碳和惰性稀释剂进行气体辅助加工以及 (c) 在惰性气体存在下进行高压加工来制造聚乙烯本体组件，及其组合； (II) 表征纳米和微米尺度的形态，(III) 通过进行短期拉伸和断裂韧性测试、长期疲劳测试以及摩擦学性能测量来评估所有类型聚乙烯的伴随机械性能。使用纳米压痕和磨损测试进行纳米级和微米级。这项跨学科工作的新颖性源于多尺度实验研究，这些研究深入了解了聚乙烯等先进聚合物的疲劳、断裂和磨损的基本机制。这项工作的智力价值是在纳米级和微米级水平上系统评估疲劳、断裂和磨损的形态和微观机制。这项工作的广泛影响延伸到临床骨科、高分子材料科学、机械工程和生物工程。 这项研究涉及生物工程、机械工程、材料科学和医学的协同作用，并为包括本科生、研究生、博士后和教师在内的各个层次提供教育机会。