温度与拉力对EMI损伤检测技术的影响及补偿方法

发布时间：2019-06-06 08:13

【摘要】：土木工程结构在服役过程中不可避免的会受到各种不利因素的影响,可能造成结构的损伤,这种损伤的积累会使结构产生安全隐患,甚至导致整体结构的破坏。为能够及时了解结构的健康状态,结构健康监测系统应运而生。其中基于压电阻抗EMI(Electro-Mechanical Impedance)的损伤检测技术以其独特的优势引起了许多专家学者关注,近年来发展十分迅速。而EMI损伤检测技术会受到包括温度和外力等等外部因素的影响。本文在前人研究基础上综合理论分析、实验研究、数据处理等手段,针对EMI损伤检测技术的外部影响因素进行以下几方面的研究工作。 1.通过研究温度对压电材料PZT(Piezoelectric)参数的影响,从理论上探究了温度对EMI损伤检测技术的影响,并进行了实验验证。对比分析了不同温度工况下测得导纳曲线的变化规律,随着温度的升高导纳曲线整体趋势不变,但是导纳曲线峰值对应的频率会减小,同时导纳曲线峰值会变大。再对实验所测数据进行RMSD(Root Mean Square Deviation)损伤指标分析,得出温度的改变会使得相同健康状态下的RMSD指标发生变化,导致对结构健康状态的误判。 2.在一维EMI理论模型的基础上增加了拉力作用,并推导了拉力作用下结构导纳的表达式,从理论上分析了拉力对EMI损伤检测技术的影响。再针对拉力荷载作用下的EMI损伤检测技术进行了实验研究。分别对无损钢梁和损伤后的钢梁施加不同拉力,分析不同拉力工况对导纳曲线及RMSD指标的影响。相同健康状态下拉力的增大会导致结构导纳值的减小,同时会导致RMSD损伤指标的增大。再分析损伤前后RMSD指标的变化以及拉力对损伤指标的影响。通过损伤前后RMSD指标的变化能够检测出结构的损伤,但当损伤程度不变结构承受拉力时,拉力的变化同样会引起损伤指标的变化,导致对结构健康状态的误判。 3.针对温度对EMI损伤检测技术的影响,采用了有效频率偏移EFS(Effective Frequency Shift)方法对EMI技术进行温度补偿。通过EFS方法对不同温度下结构的导纳信息进行处理,补偿了温度对导纳曲线横向及纵向的影响。通过对比分析补偿前后RMSD指标,可以明显看出经过补偿后的RMSD指标一定程度上减小了温度引起的指标变化。将加入了EFS补偿方法的EMI损伤检测检测技术运用到实际工程中。首先对无损伤和有损伤发生的桥梁结构进行监测,对比分析了不同时间不同温度下导纳变化及RMSD指标的变化。再用EFS方法对无损和损伤处的导纳信息进行处理,发现经过补偿后的RMSD指标可以更加有效的判断结构损伤发生及发展。 4.针对拉力因素对EMI损伤检测技术的影响,采用RBF(Radial Basis Function)神经网络的方法进行拉力补偿。针对拉力影响实验,对实验测试的健康状态下导纳信息进行RBF神经网络进行训练及仿真。利用仿真所得结果可以预测在不同拉力作用下健康状态下的导纳信息。再将拉力作用下实测的导纳信息与预测值对比,通过RMSD指标的分析即可有效判断结构的健康状态。
[Abstract]:In the course of service, it is inevitable that the civil engineering structure will be affected by various adverse factors, which may cause damage to the structure. The accumulation of the damage can cause the structure to have potential safety hazards, and even lead to the destruction of the whole structure. In order to be able to understand the health status of the structure in time, the structure health monitoring system comes into being. Among these, the damage detection technology based on Electro-mechanical Impedance has caused many experts and scholars to pay close attention to its unique advantages, and has developed very quickly in recent years. And the emi damage detection technique may be affected by external factors including temperature and external force, and the like. In this paper, on the basis of the previous research, the research work of the following aspects is carried out on the external influence factors of the EMI damage detection technology by means of theoretical analysis, experimental research and data processing. 1. Based on the influence of temperature on the parameters of PZT (PZT), the influence of temperature on the detection technology of EMI was investigated theoretically, and the experiment was carried out. The change law of the admittance curve under different temperature conditions is compared and analyzed, and the overall trend of the admittance curve is not changed with the increase of the temperature, but the frequency of the peak of the admittance curve can be reduced, and the peak of the admittance curve will change. The RMSD (Root Mean Square Devation) damage index of the experiment data is analyzed to obtain the change of the temperature, which results in the change of the RMSD index in the same healthy state, which leads to the mistake of the health state of the structure. 2. The tensile force is increased on the basis of one-dimensional EMI theory model, and the expression of the structure admittance under the action of tension is derived, and the detection technology of the tensile force on the EMI damage is theoretically analyzed. The influence of the method on the detection of the EMI damage under the action of the tensile load is also described. Apply different tension to the non-destructive steel beam and the damaged steel beam respectively, and analyze the admittance curve and the RMSD index under different tension conditions. The effect of the tensile force in the same healthy state results in a reduction in the admittance value of the structure, which can lead to the damage index of the RMSD. The change of RMSD and the damage index before and after injury were analyzed. The damage of the structure can be detected by the change of the RMSD index before and after the injury, but when the damage degree is not the same, the change of the tensile force can cause the change of the damage index, resulting in a healthy state of the structure. 3. Based on the influence of temperature on the detection technology of EMI, the effective frequency shift (EFS) method is used to the EMI technology. the admittance information of the structure at different temperatures is processed by the EFS method, and the lateral direction of the temperature to the admittance curve is compensated, It can be seen that the RMSD index after compensation has reduced the temperature to a certain extent by comparing the RRMSD index before and after the compensation. The change of the index will be applied to the EMI damage detection and detection technology with the EFS compensation method. In the actual project, the bridge structure with no damage and damage is first monitored, and the change of the admittance and the RMSD at different temperatures are compared and analyzed. The change of the index is used to process the admittance information of the damage and damage by the EFS method, and it is found that the compensated RMSD index can more effectively judge the structural damage. Occurrence and development.4. Based on the influence of the tension factor on the detection technology of EMI, the RBF (Radial Basis Function) neural network is used. Under the influence of the tensile force, the admittance information in the healthy state of the experimental test is RBF neural network. The training and simulation are carried out. The simulation results can be used to predict the health-like under different tensile forces. The admittance information under the state of tension is compared with the predicted value of the measured admittance information under the action of the pulling force, and can be effectively judged through the analysis of the RMSD index.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU317

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