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首页> 外文会议>International Workshop on Opto-Electronic Sensor-Based Monitoring in Geo-Engineering; 20071018-19; Nanjing(CN) >Multiscale aspects of monitoring geo-engineering structural systems: theory and methodology
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Multiscale aspects of monitoring geo-engineering structural systems: theory and methodology

机译：监测地球工程结构系统的多尺度方面：理论和方法

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摘要

The physical meaning of monitored field data is one of the uncertainties that prevails in non-destructive detection (NDD) of defects. This is especially true for the surveillance of geo-engineering systems that are expected to function over an extended period of time such as millions of cycles in fatigue where small defects may grow into critical sizes that will cause damage and render the structure out of commission. A critical issue involved in the development of NDD model is the gradual degradation of the material properties in time. This effect is demonstrated by the dual scale micro/macro cracking model employing the parameter ko that varies statistically in a random manner with normal distribution because material microsctructure interacts with the changing geometry of the growing defect. The mean and deviation of the normal distribution are shown to alter the range of the crack growth range up to the design life. Adjustment of the governing parameters may appear to be unmanageable at first.However, they can be determined after a few trials based on the prescribed design conditions for the tolerable crack size and the elapsed time or cycles that can be pre-set as required by inspection. The procedure is illustrated using the fracture control methodology applied to assure safety of the commercial aircrafts. The inspection period is set by the crack length versus time record that is not so readily and clearly identifiable in geo-engineering systems where the fatigue crack growth behavior is considerably more irregular than that in high strength metal alloys. To this end, monitoring of the local compliance or stiffness may be more appropriate. A dual scale micro/macro crack growth model is then used to translate the data into a form that can define the damage threshold based on the local compliance. The results are valid for any shape of the representative block that contains the defect(s) under sinvestigation. Verification of the proposed procedure canbe demonstrated in the laboratory.
机译：监控现场数据的物理意义是缺陷的非破坏性检测（NDD）中普遍存在的不确定性之一。对于预期将在较长时间段内运行的地球工程系统（例如数百万次疲劳循环）的监视尤其如此，其中小缺陷可能会增长到临界尺寸，从而导致损坏并导致结构无法使用。 NDD模型开发涉及的一个关键问题是材料性能随时间逐渐下降。这种双重效应通过使用参数ko的双尺度微/宏裂纹模型得到证明，该参数以正态分布以随机方式在统计上变化，因为材料的微结构与不断变化的缺陷几何形状相互作用。结果表明，正态分布的平均值和偏差会改变裂纹扩展范围，直至设计寿命。起初无法调节控制参数，但是可以在规定的设计条件下进行几次试验后确定，以允许的裂纹尺寸和可根据检查要求预先设置的经过时间或周期。使用确保商业飞机安全的断裂控制方法对程序进行了说明。检验周期是由裂纹长度与时间的关系来确定的，在土工工程系统中，疲劳裂纹扩展行为比高强度金属合金明显更不规则，因此在土工工程系统中无法轻易而清晰地确定。为此，监视局部顺应性或刚度可能更合适。然后，使用双尺度微观/宏观裂纹扩展模型将数据转换为可以基于局部依从性定义损伤阈值的形式。该结果对于包含缺陷的代表性块的任何形状均有效。所提议程序的验证可以在实验室中进行证明。

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