• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.3
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• pp.405-413
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• 1997

In the present paper, it is attempted to reconfirm the "Intelligent" material properties using both the sintered TiNi/Al(1100) matrix composite made by powder metallurgy method and the squeeze-casted TiNi/Al6061 specimens. A metal matrix composite is, its fault has been considered to deteriorate a strength of composite by heating residual stress of the matrix. Therefore, it is necessary to remove a tensile residual stress, to produce the strength of a composite better. On the contrary, if compressive residual stress happens in matrix of composite in place of tensile residual stress, it will make the strength of composite better. So that, this paper introduce the development of a high strength of composite, by using compressive residual stress well, on the study. By using these specimens, shape memory strengthening effects in tensile strength and fatigue crack propagation above inverse transformation temperature of TiNi fiber were investigated. We occurs the prestrain and volume fraction for to discuss the effects of a composite strength. Moreover, by SEM observation, the effect of the residual stress at the interface between Al matrix and TiNi fiber and some brittle precipitation layers such as inter metallic compounds on fracture mechanisms was discussed metallurgically.urgically.

• Steel and Composite Structures
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• v.33 no.4
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• pp.489-507
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• 2019

In order to obtain high bearing capacity and good ductility simultaneously, a structural column with hybrid normal and high strength steel (HNHSS) welded box section has been developed. Residual stress is an important factor that can influence the behaviour of a structural member in steel structures. Accordingly, the magnitudes and distributions of residual stresses in HNHSS welded box sections were investigated experimentally using the sectioning method. In this study, the following four box sections were tested: one normal strength steel (NSS) section, one high strength steel (HSS) section, and two HNHSS sections. Based on the experimental data from previous studies and the test results of this study, the effects of the width-to-thickness ratio of plate, yield strength of plate, and the plate thickness of the residual stresses of welded box sections were investigated in detail. A unified residual stress model for NSS, HSS and HNHSS welded box sections was proposed, and the corresponding simplified prediction equations for the maximum tensile residual stress ratio (${\sigma}_{rt}/f_y$) and average compressive residual stress ratio (${\sigma}_{rc}/f_y$) in the model were quantitatively established. The predicted magnitudes and distributions of residual stresses for four tested sections in this study by using the proposed residual stress model were compared with the experimental results, and the feasibility of this proposed model was shown to be in good agreement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2277-2286
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• 2002

The application of bonded dissimilar materials to industries as automobiles, aircraft, rolling stocks, electronic devices and engineering structures is increasing gradually because these materials, compared to the homogeneous materials, have many advantages for material properties. In spite of such wide applications of bonded dissimilar materials, the evaluation method of quantitative strength considering the stress singularities for its bonded interface has not been established clearly. In this paper, the stress singularity for Bctors and the stress intensity factors were analyzed by boundary element method(BEM) for the scarf joints of Al/Epoxy with and without a crack, respectively. From static fracture experiments of the bonded scarf joints, a fracture criterion and a evaluation method of interface strength in bonded dissimilar materials were proposed and discussed.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.6
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• pp.59-66
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• 2001

Fatigue strength of the welding structure is governed by the residual stress at the weldment toe and static tensile overloads were known as relieving the residual stresses. In this study, static tensile overloads were applied to the welding structures which caused the relief of residual stresses. The amount of residual stress relief was found as proportional to the change of fatigue limit at the given conditions. Based on the fact of the proportionality between the change of fatigue limit and that of residual stress, simple measurement technique is proposed. Modified stress-life curves base on proposed technique gave good agreement with test results.

• Geotechnical Engineering
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• v.3 no.2
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• pp.41-54
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• 1987

Although natural soil deposits hat.e been consolidated under Ko-stress system, the soil behavior has been predicted in laboratory from the results of tests performed on specimens consolidated under an isotropic stress s).stem. A series of undrained triaxial compression tests are performed on remolded specimens of clay consolidated under both types of stress systems, and the results at.e compared. One dimensional consolidation history induces anisotropy in clalrs, which is called as the stress induced anisotropy. However, if the clays would be reconsolidated under isotropic stress system. the anisotropy of undrained stress비h would be decreased with decrease of overconsolidation ratio. Undrained shear strength of norma]Iy consolidated clay depends on consolidation methods. Both the Rutledge hypothesis and the study of Henkel and Sowa do not agree with the test results obtained in this paper. In addition, a new theory is explained about the relationships between consolidation stresses, water contents and undiained shear strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.141-142
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• 2010

This study is related with assumption of stress block parameter for high-strength concrete. The equivalent stress distribution block of KCI design code isn't matched with the real stress distribution of high strength concrete. In this study, we tried to suggest new type of stress block parameter based on both previous test data and theoretical process.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.91-93
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• 2005

The purpose of this study is to evaluate effects of stiffener configuration welded to the plate on the fatigue strength. Nominal stress and hot spot stress for the stiffened plate under pure bending condition were evaluated using FEA and experiment and fatigue test for each specimen was performed. For S and SD type, the fatigue strength increase with a decrease in the nominal stress and hot spot stress. D type with doubler plate was found to have the lowest value of nominal and hot spot stress for a given condition. However its fatigue strength was smaller than the others.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.6
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• pp.97-103
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• 2008

In general, the strength of gears is calculated using the formula of AGMA or JGMA. But these formula can not be applied directly to the strength calculation of the rack and pinion of steering gear assay, because of complex tooth and contact shapes. So Lewis bending stress and Hertzian contact stress formula are generally used for the design of rack and pinion of steering gear assay. But these formula do not also give the exact stress of rack and pinion. In this paper, comparing the finite element analysis results and the experimentally measured values, it is shown that the finite element modeling technique of the rack and pinion of steering assay is reasonable.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.265-270
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• 2007

According to previous research, welding-induced residual stresses in steel structures can significantly affect the fatigue behaviour. Usually, high tensile residual stresses up to the yield strength are conservatively assumed at the weld toes. This conservative assumption can result in misleading fatigue assessments. Thee welding-induced residual stresses need be known in advance for a reliable fatigue assessment, which becomes possible to an increasing extent by numerical welding simulation. In this study, a fatigue Analysis technique for steel structures with welding induced residual stress is presented. First, We calculate the history of temperature according with welding process. Secondly, residual stress with a welding thermal history was evaluated by non-linear thermal stress analysis and lastly, fatigue strength is estimated with modified Goodman equation which can consider the effect of mean stress level.

• Computers and Concrete
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• v.16 no.3
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• pp.449-466
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• 2015

This paper aims to study the local bond stress-slip behavior of reinforcing bars embedded in lightweight aggregate concrete (LWAC). The experimental variables of the local bond stress-slip tests include concrete strength (20, 40 and 60 MPa), deformed steel bar size (#4, #6 and #8) and coarse aggregate (normal weight aggregate, reservoir sludge lightweight aggregate and waterworks sludge lightweight aggregate). The test results show that the ultimate bond strength increased with the increase of concrete compressive strength. Moreover, the larger the rib height to the diameter ratio ($h/d_b$) of the deformed steel bars is, the greater the ultimate bond stress is. In addition, the suggestion value of the CEB-FIP Model Code to the LWAC specimen's ultimate bond stress is more conservative than that of the normal weight concrete.