Strain measurement is an essential part of structural health monitoring (SHM). The objective of the study is to propose a new method to measure strain on the surface of a structure. The speeded‐up robust feature (SURF) method was applied to detect and trace feature points in microimages that were obtained using a smartphone with a compact microscope. Subsequently, the average displacement of feature points in microimages was calculated before and after deformation. Finally, the average strain of a certain distance in the structure surface was obtained. An experiment was performed to measure the average strain in an optical fiber of certain length and compare the data with that measured by the fiber Bragg granting (FBG) to verify the accuracy of the proposed method. Additionally, a water drop loading experiment was performed on the optical fiber to test the sensitivity of the proposed method. The results indicated that the strain measured by the smartphone with a compact microscope was in agreement with the FBG data. The error analysis illustrates the maximum error of the data measured by the two methods is 6με, and this can satisfy the requirements of civil engineering. The result of the water drop experiment reveals that the entire process of loading via water drops can be measured by the proposed method, and strain increases with the drops of water. The experimental results verify that the feasibility of the proposed method can satisfy the needs of structural health monitoring for general buildings.

中文翻译：

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基于带显微镜的智能手机拍摄的微图像的应变测量的准确性和敏感性分析

应变测量是结构健康监测（SHM）的重要组成部分。该研究的目的是提出一种测量结构表面应变的新方法。加速鲁棒特征（SURF）方法用于检测和跟踪使用紧凑型显微镜的智能手机获得的微图像中的特征点。随后，计算变形前后的微图像中特征点的平均位移。最后，获得结构表面一定距离的平均应变。进行了一项实验，以测量一定长度的光纤中的平均应变，并将该数据与通过光纤布拉格授权（FBG）测量的数据进行比较，以验证所提出方法的准确性。另外，在光纤上进行了水滴加载实验，以测试该方法的灵敏度。结果表明，通过智能手机使用紧凑型显微镜测量的应变与FBG数据一致。误差分析表明，两种方法测得的数据最大误差为6με，可以满足土木工程的要求。水滴实验的结果表明，通过所提出的方法可以测量通过水滴加载的整个过程，并且应变随着水滴的增加而增加。实验结果证明了该方法的可行性，可以满足一般建筑物结构健康监测的需要。结果表明，通过智能手机使用紧凑型显微镜测量的应变与FBG数据一致。误差分析表明，两种方法测得的数据最大误差为6με，可以满足土木工程的要求。水滴实验的结果表明，通过所提出的方法可以测量通过水滴加载的整个过程，并且应变随着水滴的增加而增加。实验结果证明了该方法的可行性，可以满足一般建筑物结构健康监测的需要。结果表明，通过智能手机使用紧凑型显微镜测量的应变与FBG数据一致。误差分析表明，两种方法测得的数据最大误差为6με，可以满足土木工程的要求。水滴实验的结果表明，通过所提出的方法可以测量通过水滴加载的整个过程，并且应变随着水滴的增加而增加。实验结果证明了该方法的可行性，可以满足一般建筑物结构健康监测的需要。水滴实验的结果表明，通过所提出的方法可以测量通过水滴加载的整个过程，并且应变随着水滴的增加而增加。实验结果证明了该方法的可行性，可以满足一般建筑物结构健康监测的需要。水滴实验的结果表明，通过所提出的方法可以测量通过水滴加载的整个过程，并且应变随着水滴的增加而增加。实验结果证明了该方法的可行性，可以满足一般建筑物结构健康监测的需要。