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Application of damage mechanics for fatigue life assessment.

机译：损伤力学在疲劳寿命评估中的应用。

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摘要

Traditional multiaxial fatigue assessment models are based on the definition of an equivalent uniaxial measurement of the stress and strain tensors in the critical region of the studied component. An equivalent uniaxial criterion is then used to assess the fatigue life. In this thesis, we study a new approach based on Continuum Damage Mechanics theory. The introduction of the Continuum Damage Mechanics (CDM) in late 1970s to model fatigue has opened a new arena of research for developing a suitable model for multiaxial fatigue. In CDM, constitutive equations are derived by using internal variables under the framework of the thermodynamics to simulate the degradation of the material responses due to damage causing phenomenon. The main advantage of this approach is that, once the constitutive laws are derived, they can be used to model the damage behavior of the material under different damage causing modes with the appropriate calibration.; In this work the locally coupled analysis proposed by J. Lemaitre [1990] has been adopted, as a post-processor of the FE analysis. The SAE1045 HR shaft has been used as the example case for the analysis and the results have been compared with the experimental results of Fash [1985]. This work focuses on the identification of the model parameters as formulated by Lemaitre. It is shown that the initial identification procedure proposed by Lemaitre leads to results poorly correlated with experimental findings. A new methodology for the identification of Lemaitre model parameters is proposed, it uses the Coffin-Manson relation for the uniaxial case. The approach is applied to the SAE1045 HR steel and it is shown that an excellent correlation can be achieved in the uniaxial case. With the calibrated parameters, the model's performance for multiaxial loading has improved. (Abstract shortened by UMI.)
机译：传统的多轴疲劳评估模型基于对所研究部件的关键区域中的应力和应变张量的等效单轴测量的定义。然后使用等效的单轴准则来评估疲劳寿命。本文研究了一种基于连续体损伤力学理论的新方法。 1970年代后期引入连续损伤力学（CDM）来模拟疲劳，为开发适用于多轴疲劳的模型开辟了一个新的研究领域。在CDM中，通过在热力学框架内使用内部变量来推导本构方程，以模拟由于破坏现象引起的材料响应的退化。这种方法的主要优点是，一旦得出了本构定律，就可以通过适当的校准将它们用于对材料在不同损伤模式下的损伤行为进行建模。在这项工作中，采用了J. Lemaitre [1990]提出的局部耦合分析作为有限元分析的后处理程序。以SAE1045 HR轴为例进行分析，并将结果与​​Fash [1985]的实验结果进行了比较。这项工作着重于Lemaitre制定的模型参数的识别。结果表明，Lemaitre提出的初始鉴定程序导致结果与实验结果的相关性很差。提出了一种识别Lemaitre模型参数的新方法，该方法将Coffin-Manson关系用于单轴情况。该方法应用于SAE1045 HR钢，结果表明，在单轴情况下可以实现出色的相关性。通过校准的参数，该模型在多轴载荷下的性能得到了改善。 （摘要由UMI缩短。）

著录项

  • 作者

    Rahman, Md. Mustaqur.;

  • 作者单位

    University of Windsor (Canada).;

  • 授予单位 University of Windsor (Canada).;
  • 学科 Engineering Civil.; Engineering Mechanical.
  • 学位 M.A.Sc.
  • 年度 2005
  • 页码 129 p.
  • 总页数 129
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 建筑科学;机械、仪表工业;
  • 关键词

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