Abstract
Quantifying bolt tension and ensuring that bolts are appropriately tightened for large-scale civil infrastructures are crucial. This study investigated the feasibility of employing the surface acoustic wave (SAW) for quantifying the bolt tension via finite element modeling. The central hypothesis is that the real area of contact in a bolted joint increases as the tension or preload is increased, causing an acoustical signature change. The experimentally verified 3-D simulations were carried out in two steps: A preload was first applied to the bolt body to simulate the realistic behavior of bolted joint; and the SAW propagation was then excited on the top surface of the plate to reflect from the bolted joint. The bolt tension value was varied between 4 and 24 kN (properly tightened bolt) in the steps of 4 kN to study the effect of the bolt tension. The results indicate an increased reflected wave amplitude and a gradual phase shift, up to 0.5 µs, as the bolt tension increased. Furthermore, the result shows that the distance between the first reflected wave and the source becomes shorter as the preload increases, as hypothesized. A 1.9 mm difference in the distance between the maximum and minimum preload was observed. As part of this study, the simulation results were also compared with the experimental results, and a good agreement between the simulation and experiments was demonstrated.
Highlights
The health of bolted joints depends mainly on the status of the threaded fastener since the fastener is responsible for holding two structural components together
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The study investigated the surface acoustic wave (SAW) reflection caused by the real contact area, which is located at the interface between the bolt head and plate surface
Summary
The health of bolted joints depends mainly on the status of the threaded fastener since the fastener is responsible for holding two structural components together. The measurement accuracy of this standard methodology can be low due to disregarding the friction between the bolt thread and the nut [2,3] Another example of a measurement technique that operates by contacting the bolt is the acoustoelastic effect based method [4]. The authors experimentally investigated an alternative method to quantify bolt tension without contacting the bolt using a synthetic phased-array surface acoustic wave (SAW) operating at 5 MHz [6]. This study takes the investigation of this technique to the level by exploring the use of ultrasonic waves to quantify the bolt tension via simulating the surface acoustic wave (SAW) propagation over the bolted joint surface. The preload value was varied between 4 and 24 kN in the steps of 4 kN
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