分布式光纤裂缝检测的有限元分析及试验

对分布式光纤裂缝检测技术中光纤-混凝土复合体的微观力学行为进行了分析. 考虑了 涂覆-护套、护套-混凝土双界面的状态非线性，混凝土采用双线性各向同性强化模型以消减 局部应力集中，避免护套-混凝土之间的过度穿透. 采用试验确定的接触对力学参数，用ANSYS 进行了数值模拟，得到了光纤-混凝土复合体的微观应力分布及光纤的曲率分布. 定量分析了 缝宽与弯曲损耗的关系，计算结果与试验结果符合较好，从理论上验证了光纤布置方式、护 套厚度对传感灵敏度和动态范围的影响，为分布式光纤裂缝检测技术提供了修正的微观力学 分析理论和方法.

NONLINEAR FINITE ELEMENT ANALYSIS AND EXPERIMENTS OF DISTRIBUTED FIBER OPTIC SENSOR SYSTEM FOR CRACK DETECTION

The micro-mechanical behaviors of fiber-concrete complex in the technology of distributed fiber optic sensor system for crack detection were investigated. 3-D nonlinear numerical simulation was performed with ANSYS, considering the nonlinear interfaces of coating-sheath and sheath-concrete. The bilinear isotropic hardening model was applied for concrete to relax local stress concentration and avoid excessive penetration between the sheath and the concrete. The mechanical parameters of contact pairs were determined by tests. The microscopic stress distribution in fiber-concrete complex and curvature distribution of fiber were obtained. The relationship between crack width and bending loss was analyzed quantitatively. The computational results have shown a good accordance with experimental results. The influences of fiber layout and sheath thickness on sensing sensitivity and dynamic range have been proved theoretically. Meanwhile, an improved micromechanical analysis was developed for the technology of distributed fiber optic sensor system for crack detection.