• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.651-658
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• 2021

Because bolts with anti-loosening coatings are used mainly for joining safety-related components in automobiles, accurate automatic screening of these coatings is essential to detect defects efficiently. The performance of the convolutional neural network (CNN) used in a previous study [Identification of bolt coating defects using CNN and Grad-CAM] increased with increasing number of data for the analysis of image patterns and characteristics. On the other hand, obtaining the necessary amount of data for coated bolts is difficult, making training time-consuming. In this paper, resorting to the same VGG16 model as in a previous study, transfer learning was applied to decrease the training time and achieve the same or better accuracy with fewer data. The classifier was trained, considering the number of training data for this study and its similarity with ImageNet data. In conjunction with the fully connected layer, the highest accuracy was achieved (95%). To enhance the performance further, the last convolution layer and the classifier were fine-tuned, which resulted in a 2% increase in accuracy (97%). This shows that the learning time can be reduced by transfer learning and fine-tuning while maintaining a high screening accuracy.

• Structural Engineering and Mechanics
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• v.26 no.6
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• pp.673-685
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• 2007

Reinforced concrete beams can be strengthened in a structural retrofit process by attaching steel plates to their sides by bolting. Whilst bolting produces a confident degree of shear connection under conditions of either static or seismic overload, the plates are susceptible to local buckling. The aim of this paper is to investigate the local buckling of unilaterally-restrained plates with point supports in a generic fashion, but with particular emphasis on the provision of the restraints by bolts, and on the geometric configuration of these bolts on the buckling loads. A numerical procedure, which is based on the Rayleigh-Ritz method in conjunction with the technique of Lagrange multipliers, is developed to study the unilateral local buckling of rectangular plates bolted to the concrete with various arrangements of the pattern of bolting. A sufficient number of separable polynomials are used to define the flexural buckling displacements, while the restraint condition is modelled as a tensionless foundation using a penalty function approach to this form of mathematical contact problem. The additional constraint provided by the bolts is also modelled using Lagrange multipliers, providing an efficacious method of numerical analysis. Local buckling coefficients are determined for a range of bolting configurations, and these are compared with those developed elsewhere with simplifying assumptions. The interaction of the actions in bolted plates during buckling is also considered.

• Journal of the Korean GEO-environmental Society
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• v.8 no.1
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• pp.49-55
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• 2007

In order to utilize treads of waste tire as reinforcement material it is necessary to know the interface friction angle between tread surfaces and soil and tensile strength of connection joint of tire treads. In this research large direct shear tests were performed to get the interface friction angle between the inner and outer surfaces of treads and soil for different degree of compaction. From the large direct shear tests, the ratio of interface friction angle to the shear friction angle of sand, ${\delta}/{\phi}$, were 1.06 in outside surface of tire tread and 0.93 in inside surface of tire tread. For weathered granite soil the ratio of interface friction angle was 0.98 and 0.92 for outside and inside of tread, respectively. Also tensile tests were performed using universal testing machine for the connection joint of treads and Tirecell units using bolts. The tensile strength of connection joint increased with the number of bolts and with the sizes of washers. Connection by polypropylene ropes showed lower strength than those of bolts.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.6
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• pp.529-536
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• 2015

A defect could be generated in bolts for a use of oil filters for the manufacturing process and then may affect to the safety and quality in bolts. Also, fine defects may be imbedded in oil filter system. So it is very important that such defects be investigated and screened during the multiple manufacturing processes. Therefore, in order effectively to evaluate the fine defects, the FEM simulations were performed to make characterization in the crack detection of the bolts and the parameters such as number of turns of the coil, the coil size, applied frequency were calculated based on the simulation results. Simulations were carried out for the defect signal of eddy current probe. Exciter and receiver were utilized. In this paper, the FEM simulations were performed in both bobbin-type and pancake-type probe, both probes were optimized under Eddy current FEM simulations and the results of calculation were discussed.

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.377-384
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• 2011

Recently, for the purpose of reducing work terms and improving performance for construction work, various methods in structure field were developed. This included the HRC system which is applicable to a typical structure (e.g., parking and office building). The HRC system introduced the Gerber Joint to raise structural efficiency and used connection plate to bolt HRC composite beam to H beam in the construction field. In this research, the experimental tests for six specimens, which were in the same field conditions, were conducted with several parameters such as the length and height of the connection plate and the number of stub bolts. The test result was compared with those made by current design codes for the deflection and strains of the main bar. Within the given load, the integration of concrete in beam and connection plate, welded with stud bolts, was verified.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.573-578
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• 1998

Recently, the Carbon Fiber Sheet(CFS) is widely used to strengthen the RC beams. But the behaviour of the RC beams which is strengthened with the CFS is not clearly defined yet. So, in this study we experimented with simply supported RC beams strengthened with the CFS, under monotonic loads. We included three parameters in this experiment which are the number of the sheets, the length of the sheets, and the existence of the anchor bolts. We investigated the strength effect of the RC beams by adhesion of the CFS, and the strengthening effect of CFS as to the respective parameters.

• Journal of the Korea Furniture Society
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• v.28 no.4
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• pp.259-267
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• 2017

Furniture should change according to space. Therefore, it is important that the flexibility of the furniture, the functional efficiency, the economical efficiency and the convenience of the furniture of today. These characteristics are also important for seminar tables that are used temporarily by a large number of people. The seminar furniture currently in use has no shielding plate, there are two forms of table and shielding plate folding table. Therefore, in this research, furniture design and product development that can complement the shortcomings of the seminar furniture currently in use were done. Analysis of problems through overseas investigation and domestic market research, design planning and design, and prototyping. We have sought to optimize the volume by applying the characteristics of RTA furniture to develop a lightweight, lightweight, lightweight, easy to install and easy to use shielding plate, and open and closed system. Basically developed two types of shielding board seminar table basic shape and Roll Screen type, we expanded the scope of application such as each color and pattern. In order to reduce the weight, we replaced the parts such as anchor bolts and hinges and the shielding plate with Roll Screen and pursued volume optimization. As a result of this research, it is expected that the system of mechanisms such as packaging standardization and damage prevention for weight reduction and volume optimization will contribute to building competitiveness by domestic office prefabricated furniture industry's original technology.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.8
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• pp.819-825
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• 2009

An open frame structure is fastened by bolt joints for strength and shock attenuation. Therefore the full finite element model of an open frame structure should be properly modeled including bolt joints for strength analysis of the frames and joint assemblies which are operated under multi-loading conditions such as driving, drop, inertia and torsional loads. Then the joints and frames must satisfy the specified allowable strength constraints. Because the full finite element model has a large number of elements to perform strength analysis, a detailed fine bolt analysis seems to be very expensive. Therefore bolts of the full finite element model are approximately modeled by coupling method to constrain degree of freedoms between adjacent nodes. However, the coupling method can exaggerate stress results at the constrained nodes. Thus a detailed bolt analysis and a theoretical/experiential formula of bolts for a worst bolt joint are performed using reaction force applied both bolt and bolt joint. Finally, the results from the two methods are compared and discussed to verify the safety of the open frame structure.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.523-528
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• 2008

An open frame structure is fastened by bolt joints for strength and shock attenuation. Therefore the full finite element model of an open frame structure should be properly modeled including bolt joints for strength analysis of the frames and joint assemblies which are operated under multi-loading conditions such as driving, drop, inertia and torsional loads. Then the joints and frames must satisfy the specified allowable strength constraints. Because the full finite element model has a large number of elements to perform strength analysis, a detailed fine bolt analysis seems to be very expensive. Therefore bolts of the full finite element model are approximately modeled by constraints equations to constrain degree of freedoms between adjacent nodes. However, the constraints equation method can exaggerate stress results at the constrained nodes. Thus a detailed bolt analysis and a theoretical/experiential formula of bolts for a worst bolt joint are performed using reaction force applied both bolt and bolt joint. Finally, the results from the two methods are compared and discussed to verify the safety of the open frame structure.

• Journal of the Korean Society for Advanced Composite Structures
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• v.5 no.4
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• pp.36-43
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• 2014

In this study, circular sectional concrete-filled tube(CFT) column-to-foundation connections were numerically investigated in order to improve their structural details. A inner reinforced specimen with high-tension bolts and inner deformed bars was adopted from a previous experimental study to make the numerical model. The validity of the numerical method was verified through comparing the experimental results with the analysis's ones. In order to optimize design variables about the inner reinforced model, a number of numerical analyses were conducted for various variables. Finally, this study suggested the optimum variables about the reinforced circular sectional CFT column-to-foundation connections.