• Journal of the Korean Society for Advanced Composite Structures
• /
• v.3 no.1
• /
• pp.8-15
• /
• 2012

The initial clamping forces of high strength bolts depending on different faying surface conditions drop within 1,000 hours regardless of loading, any other external force or loosening of the nut. This study is focused on an expectation model for relaxation of high strength bolt, which is confined to creep on coated faying surfaces after initial clamping. The range of this experiment is limited to estimate the relaxation of bolted joints coated by inorganic zinc primer. The candidate bolts were dacro-coated tension control bolts. The parameters of coated thickness for the faying surface were 96, 168,and $226{\mu}m$ respectively. From experiments, it exhibited that the logarithmic function for creep strain was derived due to the parameter of coating thickness. By using the creep strain, subsequently the quantitative model for estimating long term relaxation of high strength bolt can be taken with the elapsed time. The experimental results showed that the relaxation after the initial clamping of high strength bolt rose to a much higher range from 10% to 18% due to creep of the coating as the coating thickness was increased. This study showed that the clamping force reflecting relaxation after the elapse of constant time can be calculated from the initial clamping force of high strength bolt.

• Journal of Korean Society of Steel Construction
• /
• v.20 no.3
• /
• pp.399-407
• /
• 2008

The clamping of torque shear bolt is based on KS B 2819. It was misunderstood that the tension force of the TS bolt was induced generally at the break of pin-tail specified. However, the clamping forces on slip critical connections do not often meet the intended tension, as it considerably varies due to torque coefficient dependent on temperature variables despite the break of the pin tail. In this study, the tension of torque shear bolts were compared with two types of high-strength hexagon bolts by temperature parameters from ${-10^{\circ}C}$ to ${50^{\circ}C}$. Torque shear bolts showed that the average clamping force increased to 20kN as the temperature increased. In case of galvanized high-strength hexagon bolts, the average clamping forces at $0^{\circ}C$, $20^{\circ}C$, $50^{\circ}C$ were recorded over standard bolt tension, 178kN, and the worst standard deviation was 50kN. In case of high-strength hexagon bolts, ave rage clamping forces increased as the temperature went up, and the worst standard deviation was 33kN lower than that of galvanized high-strength hexagon bolts. As for the turn-of-the-nut method, at nut rotation of ${90^{\circ}}$, two types of high-strength hexagon bolts did not met the intended design bolt in tension, 162kN.it is neccessary to re-evaluate the range of turn of nut, ${120^{\circ}{\pm}30^{\circ}}$.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.36 no.4
• /
• pp.221-232
• /
• 2023

This paper presents a novel convolutional neural network (CNN)-based approach for predicting bolt clamping force in the early bolt loosening state of bolted structures. The approach entails tightening eight bolts with different clamping forces and generating frequency responses, which are then used to create a similarity map. This map quantifies the magnitude and shape similarity between the frequency responses and the initial model in a fully fastened state. Krylov subspace-based model order reduction is employed to efficiently handle the large amount of frequency response data. The CNN model incorporates a regression output layer to predict the clamping forces of the bolts. Its performance is evaluated by training the network by using various amounts of training data and convolutional layers. The input data for the model are derived from the magnitude and shape similarity map obtained from the frequency responses. The results demonstrate the diagnostic potential and effectiveness of the proposed approach in detecting early bolt loosening. Accurate bolt clamping force predictions in the early loosening state can thus be achieved by utilizing the frequency response data and CNN model. The findings afford valuable insights into the application of CNNs for assessing the integrity of bolted structures.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2012.05a
• /
• pp.1055-1056
• /
• 2012

• Bulletin of the Korean Chemical Society
• /
• v.31 no.7
• /
• pp.2077-2080
• /
• 2010

• Proceedings of the KIPE Conference
• /
• 1999.07a
• /
• pp.622-625
• /
• 1999

This paper introduces a novel zero-voltage switching (ZVS)) pulse width modulation (PWM) active clamping dc-to-dc boost converter. This technique presents ZVS commutation without additional voltage stress and a significant increase in the circulating reactive energy throughout the converter. Therefore, all of the losses for the switches are minimized, and high power density system can be realized. The characteristics are verified through simulation and experimental results.

• The Korean Journal of Ceramics
• /
• v.5 no.1
• /
• pp.87-90
• /
• 1999

It was suggested that tape casting method can be used to fabricate high-temperature electrostatic chucks(HTESC) based on a metal substrate coated with a glass-ceramic insulating layer. The adhesion of the coating was excellent such that it was able to withstand temperature cycling to over $300^{\circ}C$ without spalling. The electrostatic clamping pressure reached a very high value of about 9 torr at 600V and generally followed the theoretical voltage-squared curve. Based on these results, we believe that we successfully developed a viable technique for manufacturing low cost HTESC.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.10a
• /
• pp.209-210
• /
• 2006

• Proceedings of the KWS Conference
• /
• 2007.11a
• /
• pp.88-90
• /
• 2007

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2011.06a
• /
• pp.319-320
• /
• 2011