当前基于视场分离技术的光学引伸计只能提高单个方向的应变测量精度，而在与之垂直方向上的测量精度不够高，即无法同时实现双向高精度应变测量，限制了其应用范围。因此，提出了一种双向视场分离技术，该技术由4个相同斜方棱镜旋转而成，并与远心镜头结合，设计了一种双向高精度光学引伸计。开展了不锈钢试样的循环加载实验来验证上述光学引伸计相较于普通光学引伸计的优越性。此外，还进行了不锈钢试件的4次单轴拉伸实验，该双向光学引伸计与电测法所测得的弹性模量和泊松比的最大误差分别为0.62%和2.86%，4次平均误差分别为0.41%和1.38%，表明该光学引伸计具有很高的应变测量精度。

声表面波(SAW）器件广泛应用于极端环境传感, 硅酸镓镧(LGS）是常用高温压电晶体, 但高温下应变胶因结合力导致应变传递效果不佳。该文研究了高温环境下应变传感的过渡层薄膜技术, 提出了一种新的过渡层薄膜解决方案及其工艺技术, 可实现高温应变胶水传递应变更稳定的效果。结果表明, 采用溅射Al再氧化可显著提升LGS与高温胶的结合力, 从而实现很好的应变传递, 使用这种过渡层实现了500 ℃下超大量程(1 000 με）测量。

A new and easy-to-fabricate strain sensor has been developed, based on fiber Bragg grating (FBG) technology embedded into a thermoplastic polyurethane filament using a 3-dimensional (3D) printer. Taking advantage of the flexibility and elastic properties of the thermoplastic polyurethane material, the embedding of the FBG provides durable protection with enhanced flexibility and sensitivity, as compared to the use of a bare FBG. Results of an evaluation of its performance have shown that the FBG sensors embedded in this way can be applied effectively in the measurement of strain, with an average wavelength responsivity of 0.013 5 nm/cm of displacement for tensile strain and –0.014 2 nm/cm for compressive strain, both showing a linearity value of up to 99%. Furthermore, such an embedded FBG-based strain sensor has a sensitivity of ~1.74 times greater than that of a bare FBG used for strain measurement and is well protected and suitable for in-the-field use. It is also observed that the thermoplastic polyurethane based (TPU-based) FBG strain sensor carries a sensitivity value of ~2.05 times higher than that of the polylactic acid based (PLA-based) FBG strain sensor proving that TPU material can be made as the material of choice as a “sensing” pad for the FBG.

针对光纤光栅应变计无法同时准确测量结构表面多个方向应变的问题, 该文设计了一种基于光纤布喇格光栅(FBG)的三向应变计。三向应变计采用圆环状基底结构, 并在基底上封装了3根互成角度的FBG, 适用于结构表面3个方向应变的同步测量。对封装后的应变计进行性能测试, 并进行了同电阻应变片的对比实验。结果表明, 应变计具有良好的线性, 最大迟滞误差为6.1%, 应变灵敏度在0°和90°方向分别提高约2.3倍和1.4倍。随着载荷的增加, 应变计的测量误差逐渐减小, 载荷大于1.5 kg后测量误差控制在±5%。

针对现有视场分离技术在实现过程中存在的复杂调节问题，提出了一种基于双斜方棱镜成像的视场分离方法，并形成一种高精度光学引伸计。该方法在简化调节步骤的同时，能够将引伸计的标距提高数倍，并与远心镜头结合，减少离面位移对二维数字图像相关（2D-DIC）的影响。分别开展了单轴拉伸实验和连续加载-卸载实验来验证该方法的可行性和准确性。实验结果表明：该方法得出的应变与电测法结果非常吻合，应变均方根误差均不超过3 με。因此所提出的基于双斜方棱镜的视场分离式光学引伸计是一种易于安装集成的高精度应变测量技术。