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首页> 外文学位 >Mechanical integrity of plasma-sprayed hydroxyapatite coatings on titanium-6 aluminum-4 vanadium implants.
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Mechanical integrity of plasma-sprayed hydroxyapatite coatings on titanium-6 aluminum-4 vanadium implants.

机译：钛6铝4钒植入物上等离子喷涂的羟基磷灰石涂层的机械完整性。

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摘要

Plasma-sprayed hydroxyapatite (HA) coated Ti-6Al-4V is a promising material for biomedical implants. Successful applications of this implant material rely on fundamental understandings of the microstructure characteristics and mechanical behavior of the HA coating. The objectives of the present work are (1) to characterize the heterogeneous features of the HA coating, (2) to quantify the elastic/plastic behavior of the HA coating, and (3) to systematically examine in vitro mechanical integrity of the HA coating under various loading conditions.; The microstructure characterization of the as-sprayed HA coating demonstrates that it exhibits two distinctive regions on its cross-section, i.e. a crystalline ribbon-like region surrounded by a relatively smooth amorphous region. The OH and O concentrations are also found to decrease with depth from the surface of the HA coating and reach a minimum at the coating/substrate interfaces.; A feasible approach that combines the indentation tests with nonlinear finite element modeling has been developed to estimate the elastic/plastic constitutive relation of HA coatings on Ti-6Al-4V substrates. The results show that the Ramberg-Osgood constitutive equation properly describes the deformation behavior of the HA coating.; Experiments revealed that conventional cyclic bending tests cannot effectively evaluate the fatigue resistance of the HA coating on Ti-6Al-4V in both air and simulated body fluid (SBF). Alternative approaches including Hertzian indentation and a new shear test method were employed. The fatigue tests of the coating under cyclic Hertzian indentation revealed that the fatigue damage of the HA coating is more severe in SBF than in air, and thin HA coating exhibits less fatigue damage than thick HA coating. The new shear test method was developed to test coatings on metal substrates. This method generates almost the same shear loading on coatings as that in conventional tests and possesses such advantages as simplicity, ease of alignment and use, and the ability to test coatings with different thicknesses. Using the new shear test method, the nominal interfacial shear strength has been evaluated. The coating resistance to cyclic shear loading has been also characterized by the shear stress amplitude versus cycle to failure for the coating samples that failed within 10 7 cycles as well as by the residual nominal interfacial shear strength for the coating samples that survived 107 cycles. A fatigue failure mechanism of interfacial micro-flaw coalescence was suggested based on the fact that the interface between the coating and substrate does not fully bond.
机译：等离子喷涂的羟基磷灰石（HA）涂覆的Ti-6Al-4V是用于生物医学植入物的有前途的材料。这种植入材料的成功应用取决于对HA涂层的微观结构特征和机械性能的基本了解。本工作的目标是（1）表征HA涂层的异质特征；（2）量化HA涂层的弹性/塑性行为；以及（3）系统地检查HA涂层的体外机械完整性在各种负载条件下。喷涂的HA涂层的微观结构表征表明，它在其横截面上表现出两个不同的区域，即被相对光滑的非晶区域包围的结晶带状区域。还发现，OH和O的浓度随着距HA涂层表面的深度而降低，并在涂层/基材界面处达到最小值。已经开发了一种将压痕测试与非线性有限元建模相结合的可行方法，以估算Ti-6Al-4V基体上HA涂层的弹性/塑性本构关系。结果表明，Ramberg-Osgood本构方程正确地描述了HA涂层的变形行为。实验表明，常规的循环弯曲试验无法有效地评估空气和模拟体液（SBF）中的Ti-6Al-4V上的HA涂层的耐疲劳性。替代方法包括赫兹压痕和新的剪切试验方法。循环赫兹压痕下的涂层疲劳测试表明，SBF中HA涂层的疲劳损伤比空气中严重，薄HA涂层的疲劳损伤比厚HA涂层小。开发了新的剪切测试方法以测试金属基材上的涂层。该方法在涂层上产生的剪切载荷几乎与常规测试中相同，并具有诸如简单，易于对准和使用以及测试不同厚度涂层的能力等优点。使用新的剪切测试方法，已经评估了名义界面剪切强度。涂层对循环剪切载荷的抵抗力还通过在10 7个循环内失效的涂层样品的剪切应力幅度与失效循环的比值以及在107个循环中幸存的涂层样品的残余标称界面剪切强度来表征。基于涂层与基体之间的界面未完全结合的事实，提出了界面微缺陷结合的疲劳破坏机理。

著录项

  • 作者

    Zhang, Chenge.;

  • 作者单位

    Hong Kong University of Science and Technology (Hong Kong).;

  • 授予单位 Hong Kong University of Science and Technology (Hong Kong).;
  • 学科 Engineering Biomedical.; Engineering Mechanical.; Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2000
  • 页码 171 p.
  • 总页数 171
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 生物医学工程;机械、仪表工业;工程材料学;
  • 关键词

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