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光纤布拉格光栅(FBG)应变测量是基于光栅受到轴向应变作用时其波长将会发生相应变化。但在复杂应力状态下,由于横向效应的存在,光纤布拉格光栅的安装方位对光纤应变测量产生影响。通过理论推导和实验分析验证了安装方位对光纤应变测量的影响,并以单向应力状态为例,导出应变测量误差与光纤布拉格光栅安装方位的关系曲线:光纤的轴向与主应力的夹角60°附近,误差急剧增大,可使测量结果严重失真。为消除安装方位引起的误差,给出了复杂应力状态的应变测量修正公式。
Fiber Bragg Grating (FBG) strain measurements are based on the grating whose axial strain changes its wavelength accordingly. However, due to the lateral effect, the installation orientation of fiber Bragg gratings can affect the optical fiber strain measurement under complex stress conditions. The effect of installation orientation on optical fiber strain measurement is verified by theoretical derivation and experimental analysis. Taking unidirectional stress state as an example, the relation between strain measurement error and fiber Bragg grating mounting orientation is deduced: the angle between the axial direction of optical fiber and the principal stress 60 ° near the sharp increase in error, can seriously distort the measurement results. In order to eliminate the error caused by the installation orientation, the strain measurement correction formula of complex stress state is given.