Papers by Keyword: High Tension Bolt

Abstract: In order to secure the uniformity and to reduce the scattering of torque coefficient value, which is a decisive factor in the quality of high tension bolt nut and washer sets, effort is required from the manufacturer to standardize manufacturing process and to continuously improve the quality.

Abstract: Because the fastener tension of high strength bolt, nut, and washer set is subject to the environmental factors such as temperature, humidity and storage period, extreme care should be taken during the joining and storage of such products. In case quality change is anticipated, the parts shall certainly be inspected.

Abstract: The use of steel plates has been greatly increased in bridge construction, particularly for long-span bridges, and connections between the plates are made usually using high-tension bolts. However, the specifications on the use of large-sized high-tension bolts are not adequately stated in the currently available construction manuals. In order to provide further information on the use of the large-sized high-tension bolts, this study experimentally investigated the relaxation and slip behavior of M30 bolts with varying bolt size and plate thickness. In addition, numerical evaluation using FEM was performed to investigate the compressive stress occurred on the inside of bolt hole. The analyzed results were compared with the stress distribution measured from strain gages attached on the bolts and bolt holes. From the study presented herein, it was found that the relaxation was increased as the size of bolt increased, and that the M30 high-tension bolts developed slip coefficient greater than 0.4. The thickness of plate did not significantly affect the compressive stress distribution around the bolt holes.

Abstract: Elastic properties of high tension bolt are evaluated non-destructively by measuring acoustic longitudinal and shear wave velocities using mode-converted ultrasound. Mode-converted longitudinal and shear waves along bolt are captured to calculate acoustic wave velocities and determine elastic constants such as Young’s modulus and Bulk modulus based on acoustoelasticity. Ray analysis to select a specific mode conversion from longitudinal mode to shear mode is carried out and discussed with experimental results. From experiment results of maximum 5% of measurement error, it is shown that the proposed mode-converted ultrasonic technique is very effective and sensitive enough to characterize mechanical modulus of high-tension bolts quantitatively.

Abstract: High-tension bolts have been used widely for the clamping of many kinds of large structures. In these bolts, the estimation of clamping force has been regarded as the main issue in the evaluation of clamping condition. This paper proposes a method using ultrasonic wave, which is based on the dependency of sound speed on the stress. In order to verify the usefulness of the proposed method, two kinds of experiments are carried out. The first one involves the measurement of sound speed when the bolt is stressed by the tension tester, and here, the relationship between the exact axial force and sound speed is calibrated. The result shows good agreement with the expected linear relationship between sound speed and axial stress. The second experiment involves the measurement of axial stress by the proposed method when the bolt is stressed by the torque wrench. The results are coincident to the strain gage measurement. From these results, we can conclude that the proposed method is indeed useful in evaluating clamping force in high-tension bolts.