线黏弹性端接布拉格光纤光栅传感器应变传递机理

Strain Transfer Mechanism of End-Bonding Fibre Bragg Grating Sensors Based on Linear Viscoelasticity

端接光纤光栅应变传感器具有无多峰、栅区不直接受力和各点受力相等等优点,在基片式和夹持式等传感器封装中得到广泛应用。但黏接层的剪切变形会导致光纤光栅测量应变与基体结构应变不同,从而产生应变测量误差。实际使用中,需要准确获得黏接层剪切变形影响下光纤光栅应变与基体结构应变的函数关系,以提高应变的测量精度。为此,推导了线黏弹性表面黏贴式端接光纤光栅应变传递方程,建立了瞬时响应和准静态响应下光纤光栅和基体之间的平均应变传递模型。讨论分析了影响平均应变传递率的因素,给出明显优于栅区黏接式光纤光栅应变传感器的黏接层参数的影响规律。通过有限元仿真验证了理论方程的有效性。该模型为端接光纤光栅应变传感器的设计与应用提供依据。

The end-bonding fiber Bragg grating （FI3G） sensors have many advantages such as no multiple peaks, no direct force in grating area and all points suffering the same stress, which are widely used to the packaging of substrate-type, clamp-type and other types of sensors. However, the shear deformation in the adhesive layer results in the difference between FBG strain and matrix strain, and thus the strain measurement error is introduced. In the practical applications, it is necessary to precisely obtain the function relationship between the FI3G strain and the matrix strain under the influence of the shear deformation in the adhesive layer to improve the measurement accuracy of strain. For this purpose, the strain transfer equation of end-bonding FBGs based on linear viscoelasticity is derived and the average strain transfer models between fiber grating and matrix under instantaneous response and quasi-static response are developed. The parameters that influence the average strain transfer rate are discussed and analyzed. The influence law of the adhesive layer parameters with which the grating is obviously superior to that of a grating-bonding FBG sensor is demonstrated. The validity of the theoretical equation is verified by the simulation by the finite element method, and the proposed model provides a theoretical basis for the design and application of end-bonding FBG strain sensors.