Vorhersage des Ermüdungsbruchs

疲劳断裂的预测

• 批准号: 64100804
• 负责人: Professor Dr. Karl Maier, since 7/2009
• 金额: --
• 依托单位: Helmholtz-Institut für Strahlen- und Kernphysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2008
• 资助国家: 德国
• 起止时间: 2007-12-31 至 2010-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/64100804?language=en
• 关键词: Vorhersage; des; Erm; dungsbruchs

Failure of construction parts due to fatigue is a phenomenon well known to the public. After severe accidents of airplanes, trains and cars, it is widely discussed. From our daily experience we know that in repeatedly loaded metals, alloys and polymers the lifetime is finite.Since almost 150 years the lifetime of construction parts is determined employing destructive test series like the Wöhler-test, where a huge number of identical samples has to be tested in a very time-consuming way. Up to the present these methods have not changed in principle. The general goal of this project is the development of a new reliable method for the prediction of the remaining useful lifetime of mechanically loaded components. On a microscopic scale material fatigue is based on accumulation of dislocations and other defects in the lattice. Already in the early stages of fatigue – within the first couple of load cycles – a significant increase of the defect density can be observed nondestructively by Positron Annihilation Spectroscopy (PAS). The transition from the state of normality (fatigued but stable properties) to failure is directly correlated to the local defect density, which is experimentally accessible by the S-parameter. Assuming that failure occurs, when the defect density exceeds a critical value locally, it can be employed as a precursor for failure. Our goal is a robust and broadly applicable method for an extrapolation of failure from an early state of fatigue.In some special cases the experimental results obtained with PAS are already sufficient for a prediction of fatigue failure. But a general technique of failure prediction is far from trivial and will only be possible by a combination of experimental methods and a model describing the accumulation of defects during fatigue. With such a model we do not intend a detailed description of dislocations on the microscopic scale. Instead, the existing knowledge of plasticity theory should be implemented as simple as possible but accurate enough to describe the evolution of the defect density during a huge number of fatigue cycles. As a first approach a model based on a cellular automaton was developed in a diploma thesis. In the present state the model could already reproduce some aspects of fatigue: the accumulation of defects and the local transition from elastic deformation to plastic flow. But in the present state idealized simple material properties and transition functions are implemented. For a sufficient modeling of fatigue the model has to improved essentially and validated by experimental data.

由于疲劳而导致的建筑部件失败是公众众所周知的现象。在严重的飞机，火车和汽车发生了严重的事故之后，对此进行了广泛讨论。从我们的日常经验来看，我们知道，在反复装载的金属，合金和聚合物中，生命周期是有限的。在近150年的时间里，施工零件的寿命被确定，采用了诸如Wöhler测试的破坏性测试系列，其中必须以非常耗时的方式进行大量相同的样品。到目前为止，这些方法原则上没有改变。该项目的一般目标是开发一种新的可靠方法，用于预测机械加载的组件的剩余使用寿命。在微观尺度上，材料疲劳是基于晶格中位错和其他缺陷的积累。在疲劳的早期阶段 - 在前几个载荷周期内，可以观察到缺陷密度的显着增加。通过正电子歼灭光谱（PAS）无损害。从正态性状态（疲劳但稳定的特性）到失败的过渡与局部缺陷密度直接相关，该局部缺陷密度在实验上可以通过S参数访问。假设发生故障发生，当缺陷密度在本地超过临界值时，它可以作为故障的前体进行。我们的目标是一种可靠且广泛的方法，用于推断从疲劳的早期状态外推断失败。在某些特殊情况下，使用PAS获得的实验结果已经足以预测疲劳失败。但是，一般的失败预测技术远非微不足道，只有通过实验方法和描述疲劳期间缺陷准确性的模型的组合才有可能。通过这样的模型，我们不打算在微观量表上详细描述错位。取而代之的是，应尽可能简单地实现现有的可塑性理论知识，但足够准确，以描述大量疲劳周期中缺陷密度的演变。作为第一种方法，基于细胞自动机的模型是在文凭论文中开发的。在当前状态下，模型已经可以再现疲劳的某些方面：缺陷的准确性以及从弹性变形到塑料流的局部过渡。但是在当前状态下，实施了理想化的简单材料属性和过渡功能。为了进行足够的疲劳模型，该模型必须通过实验数据进行基本和验证。