Study on the Optimal Groove Shape and Glue Material for Fiber Bragg Grating Measuring Bolts

Abstract

Fiber Bragg grating (FBG) measuring bolts, as a useful tool to evaluate the behaviors of steel bolts in underground engineering, can be manufactured by gluing the FBG sensors inside the grooves, which are usually symmetrical cuts along the steel bolt rod. The selection of the cut shape and the glue types could perceivably affect the final supporting strength of the bolts. Unfortunately, the impact of cut shape and glue type on bolting strength is not yet clear. In this study, based on direct tension tests, full tensile load–displacement curves of rock bolts with different groove shapes were obtained and analyzed. The effects of groove shape on the bolt strength were discussed, and the stress redistribution in the cross-section of a rock bolt with different grooves was simulated using ANSYS. The results indicated that the trapezoidal groove is best for manufacturing the FBG bolt due to its low reduction of supporting strength. Four types of glues commonly used for the FBG sensors were assessed by conducting tensile tests on the mechanical testing and simulation system and the static and dynamic optical interrogators system. Using linear regression analysis, the relationship between the reflected wavelength of FBG sensors and tensile load was obtained. Practical recommendations for glue selection in engineering practice are also provided.

Monitoring and correction of the stress in an anchor bolt based on Pulse Pre‐Pumped Brillouin Optical Time Domain Analysis

“…The closer to the exposed end of the anchor, the greater was the difference in the shear stress ratio, indicating that the anchor slot would cause local stress concentration. The difference between the true value and the measured value was similar to the theoretical calculation result of Zhao . However, theoretical calculation shows that the ratio of the measured value of the stress distribution along the bolt to the true value is constant, which is inconsistent with the experimental result.…”

“…On this basis, different levels of axial force were determined during the pulling process and the shear stress distribution along the GFRP anchor was calculated. Zhang et al conducted direct tension tests of rock bolts with different grooves and analyzed the full tensile load‐displacement curves of rock bolts with different groove shapes. The influence of groove shape on bolt strength was discussed.…”

Fiber Bragg Grating Monitoring of Full-bolt Axial Force of the Bolt in the Deep Strong Mining Roadway

“…To investigate the influence of different slotting shapes on the strength of the rod, the ANSYS finite element analysis software is an effective simulation method, and can assess the strength and damage of the materials by the stress concentration and strain of the materials under stress. Zhao et al [ 27 ] used the static analysis module of the ANSYS software to investigate the strength of different groove-shaped bars without in situ stress. However, in the process of deep mining, the characteristics of “three highs and one disturbance” are particularly obvious, and the analysis of the strength of the rod under high ground pressure and disturbance stress is insufficient.…”

Structural Design and Application of Desensitized FBG Force-Measuring Bolt

“…Liang Minfu et al [ 20 ] designed the FBG Bolt Force Sensor by using cantilever beam and diaphragm as elastic components. Zhao Yiming et al [ 21 ] studied the influence of groove shape on the strength of FBG-FMB, and provided practical suggestions for pasting glue in engineering practice. Wang Peng et al [ 22 ] designed a full-length anchored FBG-FMB and monitoring system after deriving the conversion equation between the axial force of the bolt and the FBG wavelength variation.…”