• Wind and Structures
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• v.21 no.6
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• pp.709-726
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• 2015

In this study, a novel vision-based bolt-loosening monitoring technique is proposed for bolted joints connecting tubular steel segments of the wind turbine tower (WTT) structure. Firstly, a bolt-loosening detection algorithm based on image processing techniques is developed. The algorithm consists of five steps: image acquisition, segmentation of each nut, line detection of each nut, nut angle estimation, and bolt-loosening detection. Secondly, experimental tests are conducted on a lab-scale bolted joint model under various bolt-loosening scenarios. The bolted joint model, which is consisted of a ring flange and 32 sets of bolt and nut, is used for simulating the real bolted joint connecting steel tower segments in the WTT. Finally, the feasibility of the proposed vision-based technique is evaluated by bolt-loosening monitoring in the lab-scale bolted joint model.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.353-361
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• 1989

A parametric study of load distribution in bolt-nut joints is performed by the method of finite element contact analysis. The contacting surface is assumed unbonded and frictionless. Multi-body contact analysis is performed in elastic region under the assumption of axi-symmetric stress state. Load acting on the first thread from the fastened plate is much greater than that on the other threads in the standard setting. But the load distribution is shown to be improved by making the center of contact force acting on the nut surface move outwards. Such a modification is possible by enlarging the gap between bolt shank and fastened plate or by inserting suitable washers. Shape modification of the standard nut by the making a groove and a step on the nut surface is also suggested, which results in almost uniform load distribution and considerable decrease in the maximum stress of the joint.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.8
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• pp.205-212
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• 2003

In this study, in order to investigate a modeling technique of the structure with bolted joints, four kinds of finite element model are introduced; a solid bolt model, a coupled bolt model, a spider bolt model, and no bolt model. All proposed models take account on prestrained effect and contact behavior of flanges to be joined. Among these models, a solid bolt model, which is modeled by using a 3-D solid element and a surface-to-surface contact element between the head/nut and the flange interfaces, has the best accurate responses compared with the experimental results. In addition, coupled bolt model, which couples the degree of freedom between the head/nut and the flange, shows the best effectiveness and usefulness in view of computational time and memory usage. Finally, the bolt model proposed here is adopted for structural analysis of a large diesel engine of a ship consisting of several parts which is connected by long stay bolts.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.326-328
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• 2006

• Composites Research
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• v.36 no.4
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• pp.259-263
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• 2023

This study investigated the open hole tensile (OHT) properties of carbon fiber/epoxy composites and compared them to bolt joint tensile (BJT) properties. The net nominal modulus and strength (1376 MPa) were found to be higher than the gross nominal strength (1041 MPa), likely due to increasing hole size. The OHT and BJT specimens exhibited similar stiffness, as expected without bolt rotation causing secondary bending. OHT specimens experienced a sharp drop in stress indicating unstable crack propagation, delamination, and catastrophic failure. BJT specimens failed through shear out on the bolt side and bearing failure on the nut side, involving fiber kinking, matrix splitting, and delamination, resulting in lower strength compared to OHT specimens. The strength retention of carbon fiber/epoxy composites with open holes was 66%. Delamination initiation at the hole's edge caused a reduction in the stress concentration factor. Filling the hole with a bolt suppressed this relieving mechanism, leading to lower strength in BJT specimens compared to OHT specimens. Bolt joint efficiency was calculated as 15%. The reduction in strength in bolted joints was attributed to fiber-matrix splitting and delamination, aligning with Hart Smith's bolted joint efficiency diagram. These findings contribute to materials selection and structural reliability estimation for carbon fiber/epoxy composites. They highlight the behavior of open hole and bolt joint configurations under tensile loading, providing valuable insights for engineering applications.

• Structural Engineering and Mechanics
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• v.55 no.3
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• pp.639-654
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• 2015

Bolted joints are essential elements of mechanical structures and metal constructions. Although their static behaviour is fairly well known, their dynamic behaviour due to shocks and vibrations has been less studied, because of the large size of the finite element models needed for a detailed simulation. This work presents four different simplified models suitable for studying the dynamic behaviour of an elementary bolted joint. Three of them include contact elements to allow sliding of the screw head and the nut on the assembled parts, and the last one allows rotation between screw and nut. A penalty approach based on the Coulomb friction model is used to model contact. The results show that these models effectively represent the dynamic behaviour, with different accuracy depending on the model details. The last model simulates the self loosening of a bolt subjected to transversal vibrations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1363-1366
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• 2005

The tiebar is used by joint for keeping from deformation by conserving tensile load between two structure. The tiebar, bolt joining type, is combined by tiebar and clevis like bolt and nut. By coupled, it maintains tensile load. While it goes through repeated load, it occurs to loose because joining force between clevis and nuts is reduced. So, continuos maintenance is needed such as making tighter periodically, repairing the broken part and so on. For that reason, this paper calculates necessary torque unfastening joint for conventional tiebar and presenting tiebar theoretically and then consider the reason that conventional bolt-typed tiebar unties. Also, through vibration untied test for two types of tiebar we confirm that presenting tiebar have a improvement of unfastening when we compare with the conventional one.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5838-5842
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• 2011

The study mainly aims to explore how deterioration of motor control center, namely MCC, and vibration put impact on temperature of bus bar as well as temperature change of bolt-nut joint. The motor control center consists of three internal parts (i.e. R, S, T) which are for motor operation of high capacity. Two dimensional mechanism for measuring temperature was designed and manufactured with infrared temperature sensor. Installing it in inner motor control center enabled researcher to monitor temperature of bus bar as well as amount of change of current regularly. Temperature change of bus bar according to load was primarily examined based on a bolted joint in the experiment. It was clearly verified that temperature change of bus bar was proportional to current consumption. Therefore, installing non-contact two dimensional mechanism for measuring temperature in motor control center would be expected to prevent temperature rise owing to overload current and power outage as well as fire accident which can be triggered by poor electrical contact.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.6 no.2
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• pp.3-8
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• 2007

Nonlinear property and contact matter are analyzed about the pipe applied with internal pressure through this study. The weakest part and its safety can be examined. Maximum equivalent stress is shown at the contact surface between bolt and nut. The value of contact stress with the pressure of 12MPa is increased 1.4 times as large as that with no pressure. The maximum contact pressure is shown at the clamp corner of the external surface on pipe. The value of contact pressure with the pressure of 12MPa is increased 1.4 times as large as that with no pressure. The radial deformation with no pressure is also increased greatly at the middle part of internal surface on pipe. But this maximum deformation on pipe with the pressure of 12MPa is shown at the part far away the support of pipe. This value is increased 5.7 times as large as that value with no pressure. As contact status, the sticking occurs most at the external surface of pipe. It also tends to occur at the contact surface between bolt and nut. At the external surface of pipe, the sticking in case of the pressure of 12MPa occurs more than that in case of no pressure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2356-2363
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• 2015

This study deals the optimization design with the simulation based design of a coil spring inserted into the lock nut for preventing the screw thread from loosening at the bolted joint when the high-strength steel bolt with the property class of 10.9 is used and the screw torque of 640 to 800 (Nm) is applied. In this study, structural analysis of assembly composed of bolt, nut and coil spring is carried out to evaluate its safety factors on the basis of the equivalent stress with commercial finite element analysis software. And the design strategy to extract the design improvement from these simulation results is established. An iterative process performed with the proposed design strategy is also proposed for improving the performance of the existing design. At the proposed procedure, the feasible design parameters using response surface method are found, and then these parameters are verified to be optimal or not by comparing with the response values and the simulation results obtained from the feasible parameters.