• Journal of Industrial Technology
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• v.26 no.B
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• pp.127-134
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• 2006

As material needs have been increasing with recent economic growth, it is a current tendency that the magnitude of load applied to structure has been rising. With improved technique of product materials, steel and concrete have been stranger than ever so the danger of fatigue damage increases as permanent action of repeated loads. In case of deformed steel bars widely used in reinforced concrete structure, when they are product in factory, there will exist same parts connecting the steels. Such connections are easy to be weakened by permanent action of repeated loads. It is a real condition in Korea that there is lack of research of it. As a result of estimating fatigue characteristic of Pressure Welded joints with the steels that are oftenly used and producted in domestic it is showed that there are no remarkable difference in fatigue strength. Because there is no detail which is refered in Civil Specification, this paper will be the basic data being added in later Specification.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.359-364
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• 2004

We investigated the effect of weld details on fatigue behavior of a material, JIS SM 490 A, with yielding strength of about 350 MPa and tensile strength of about 520 MPa. Tensile tests, instrumented indentation tests and fatigue tests were carried out on double V-grooved butt weld plates such as reinforcement removed, as-welded and weld toe ground. In addition plates with transverse fillet welded web, load carrying cruciform fillet welded plates, non-load-carrying cruciform fillet welded plates and longitudinal butt welded plates were tested. S-N curves for the above specimens were obtained and analyzed

• Elastomers and Composites
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• v.52 no.2
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• pp.114-130
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• 2017

Enhancing the properties of rubber, such as the tensile strength, modulus, and wear abrasion, by the addition of carbon black and silica as fillers is very important for improving the performance of rubber products. In this review, we summarize the general features of 'the reinforcement of rubber by fillers' and the equations for representing the reinforcement phenomena. The rubber reinforcement was attributed to enhancement of the following: the rubber, bound rubber, formation of networks, and combination between rubber chains and silica followed by entanglement. The reinforcement capability of silica species with different surface and networked states demonstrated the importance of the connection between the silica particles and the rubber chains in achieving high reinforcement. The model involving combination followed by entanglement can provide a plausible explanation of the reinforcement of rubber by carbon black and silica because the combination facilitates the concentration of rubber chains near the filler particles, and entanglement of the rubber chains around the filler particles enforces the resistance against deformation and breakage of rubber compounds, resulting in high reinforcement.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.667-674
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• 1992

Recently advantages in composite and light weight material technique have led to the increased use of structural adhesives in various industries. In spite of such wide application of the adhesive joints, the evaluation method of fracture strength and design methodology of them, have not been established. In this study finite element method, theoretical and experimental analyses were investigated according to changes of lap length and adhesive for adhesive single-lap joint. As the results, the strength evaluation of adhesive joint by conventional nominal stress, was pointed out inadequate strength evaluation and design method regardless stress singularity, stress distribution and crack propagation in its adhesive layer. Also, it was examined the problems to apply fracture mechanics by means of static and fatigue test.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.10
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• pp.5290-5298
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• 2013

In order to apply a mechanical deck joint to the prefabricated steel grid composite decks, shear resistance of a joint composed of concrete shear key and high-tension bolt is experimentally evaluated by the push-out test. Shear resistance evaluated by the test is compared with resistance estimated by empirical and design equations based on the shear friction theory. Test results show that joint specimens bonded by epoxy have about 10% more shear resistance than specimens with strengthened shear key by steel plates, but in the case of specimens with strengthened shear key there is smaller resistance deviation than specimens bonded by epoxy. In comparison with resistances estimated by empirical and design equations, the deck joint can be safely designed. But because the existed shear resistance of deck joint is underestimated by the ACI-318, application of the LRFD design equation could be more reasonable.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.111-124
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• 2004

This research is a part of a research program to verify the seismic performance of circular reinforced concrete bridge columns with respect to longitudinal steel connection details under cyclic lateral load. A total of 21 column specimens were constructed and tested. Main variables in this test program were longitudinal steel connection details(continuous, lap-spliced, and mechanically connected), confinement steel ratio, and axial force ratio, etc. The test results of the columns with different longitudinal steel connection details showed different failure mode, strength degradation, and seismic performance. From the quasi-static test, it was found that the columns with all longitudinal reinforcement lap-spliced showed significantly reduced ductility. However, seismic performance of the columns with half of longitudinal reinforcement lap-spliced showed limited ductility but much more ductile behaviour than the columns with all longitudinal reinforcement lap-spliced. It was also found that the seismic performance, failure mode and strength degradation of columns with mechanical connected longitudinal reinforcement were similar to those of columns with continuous longitudinal reinforcement.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.150-153
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• 2006

The purpose of this research is focused on evaluating the flexural behavior of reinforced concrete beam having 22mm diameter re-bars by lapping methods. To compare the existent lapping method with mechanical lapping methods, four cases of concrete beams were tested to be failed flexurally by monotonic loading. Based on test results, the relations between load and displacement, ductility, maximum load was comparatively analyzed. The structural performance on four cases of members were evaluated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1179-1185
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• 2011

Cold and hot-rolled carbon steel sheets are commonly used in railroad cars or commercial vehicles such as the automobile. The sheets used in these applications are mainly fabricated by spot welding, which is a type of electric resistance welding. However, the fatigue strength of a spot-welded joint is lower than that of the base metal because of high stress concentration at the nugget edge of the spot-welded part. In particular, the fatigue strength of the joint is influenced by not only geometrical and mechanical factors but also the welding conditions for the spot-welded joint. Therefore, there is a need for establishing a reasonable criterion for a long-life design for spot-welded structures. In this thesis, ${\Delta}P-N_f$ relation curves have been used to determine a long-life fatigue-design criterion for thin-sheet structures. However, as these curves vary under the influence of welding conditions, mechanical conditions, geometrical factors, etc. It is very difficult to systematically determine a fatigue-design criterion on the basis of these curves. Therefore, in order to eliminate such problems, the welding residual stresses generated during welding and the stress distributions around the weld generated by external forces were numerically and experimentally analyzed on the basis of the results, reassessed fatigue strength of gas welded joints.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.561-565
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• 2010

Stainless steel sheets are widely used as structural materials for the manufacture of railroad cars and commercial vehicles. These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding. For the fatigue design of gas welded joints such as fillet joints and plug joints, it is necessary to obtain information on the stress distribution at the weldment and the fatigue strength of the gas welded joints. Moreover the influence of the geometrical parameters corresponding to the gas welded joints on the stress distribution and fatigue strength must be evaluated. ${\Delta}P-N_f$ curves were obtained from the data recorded in fatigue tests. Using these results, the ${\Delta}P-N_f$ curves were rearranged according the relation between $\Delta\sigma-N_f$ and the maximum stress at the edge of the fillet welded joint.

• Resources Recycling
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• v.24 no.6
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• pp.45-53
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• 2015

There are few studies on the effects of different sources of PVC scraps generated after the end-of-life PVC products and these scraps are used to prepare PVC products of low quality. In this paper, rigid PVC scraps from different sources such as clothes, pipes, and others were investigated to incorporate into virgin PVC compounds as a part of efforts to recycle various PVC scraps effectively. It was found that the tensile strength and impact strength of the PVC compounds generally decreased with increasing the content of PVC scraps. The impact properties of scrap were in order of CC > PC > RC, tensile strength were PC > CC > RC and Vicat softening temperature shows no specific tendency. CC scraps contents of 50 phr of virgin PVC resin showed 80 %, and PC scrap with 50 phr of virgin resin showed 50% of the mechanical properties with virgin PVC.