• Journal of Welding and Joining
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• 제29권4호
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• pp.61-66
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• 2011

The purpose of this study is to develop improved boom structures with reliable fatigue strength of weldment and lower production cost. For that purpose, multi-body dynamic analysis was performed to evaluate forces acting on arm & boom cylinders and joints of boom structure during operation of an excavator for three working postures, then stress analysis was made to investigate stress distribution around diaphragms at the bottom plate of boom structures which was known to be susceptible to fatigue failures of welded joints, and finally boom structures with optimum arrangement of diaphragms was proposed. This work mainly consists of the following two parts: part 1 focuses on multi-body dynamic analysis of excavators during operation and part 2 includes evaluations of fatigue strength of welded joints for modified boom structures.

• Computers and Concrete
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• 제3권1호
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• pp.17-28
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• 2006

Replacement of actual stress distribution in a reinforced concrete (RC) flexural member with a simpler geometrical shape, which maintains magnitude and location of the resultant compressive force, is an acceptable conceptual trick. This concept was originally perfected for normal strength concrete. In recent years, high strength concrete (HSC) has been introduced and widely used in modern construction. The stress block parameters require updating to account for special features of HSC in the design of flexural members. In future, more varieties of concrete may be developed and a corresponding design procedure of RC flexural members will be required. The usual practice is to conduct large number of experiments on various sizes of specimen and then evolve an empirical relation. This paper presents a numerical procedure through which the stress block parameters can be numerically derived for a given strain ratio variation. The material model for concrete is presented and computational procedure is described. This procedure is illustrated with several variations of strain ratio. The advantages of numerical procedure are that it costs less and it can be used with new material models for any new variety of concrete.

• Structural Engineering and Mechanics
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• 제24권2호
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• pp.137-154
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• 2006

The reliable pushover analysis of RC structures requires a realistic prediction of moment-curvature relations, which can be obtained by utilizing proper constitutive models for the stress-strain relationships of laterally confined concrete members. Theoretical approach of Mander is still a single stress-strain model, which employs a multiaxial failure surface for the determination of the ultimate strength of confined concrete. Alternatively, this paper introduces a simple and practical failure criterion for confined concrete with emphasis on introduction of significant modifications into the two-parameter Drucker-Prager model. The new criterion is only applicable to triaxial compression stress state which is exactly the case in the RC columns. Unlike many existing multi-parameter criteria proposed for the concrete fracture, the model needs only the compressive strength of concrete as an independent parameter and also implies for the influence of the Lode angle on the material strength. Adopting Saenz equation for stress-strain plots, satisfactory agreement between the measured and predicted results for the available experimental test data of confined normal and high strength concrete specimens is obtained. Moreover, it is found that further work involving the confinement pressure is still encouraging since the confinement model of Mander overestimates the ultimate strength of some RC columns.

• 산업기술연구
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• 제22권A호
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• pp.185-192
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• 2002

The performance of old and the new concrete construction depends upon bond strength between old and the new concrete. Current adhesive and strength measurement method ignores the effect of stress concentration from shape of specimens. Therefore, this research calculates stress concentration coefficient as the ratio of drilling depth to drilling diameter($h_s/D$), the ratio of overlay thickness to drilling diameter($h_0/D$), the ratio of steel disk thickness to drilling diameter(t/D), the ratio of overlay elastic modulus to substrate modulus($E_1/E_0$), the distance from core to corner border(L_$_{corner}$) and the distance between cores(L_$_{coic}$) vary. The finite element method is adapted to analysis The results from 'the F.E.M analysis are as follows. The stress concentration effects can be minimized when the ratio of drilling depth to drilling diameter($h_s/D$) is 0.20~0.25, the elastic modulus ratio($E_1/E_0$) is 06~1.0, and the ratio of steel disk thickness to drilling diameter(t/D) is 3.0. The overlay thickness, the distance from specimens to corner border(L_$_{corner}$), the distance between cores(L_$_{coic}$) almost do not affect to the stress concentration.

• 한국해양공학회지
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• 제13권2호통권32호
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• pp.51-57
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• 1999

In this study, one side fillet welded T-joint, used in box type girder and other welding structure, was investigated by stress analysis and bending fatigue test without edge preparation, with variation of joint shape. The purpose of this study is to give the welding condiltion and design standard on manufacturing one side fillet welded T-joint. As a result, the following conclusions were obtained. 1) In one side fillet welded T-joint, the larger the leg length and the penetration depth, the greater the bending fatigue strength because reduction of stress and strain on toe and root. The increase of the longitudinal leg length rather than vertical leg length contributed to the increase in bending fatigue strength. 2) In one side fillet welded T-joint without edge preparation, both general manual welding and general automatic welding were carried out with same condition. In this case, automatic welding showed deeper penetration and more increased longitudinal leg length than manual welding, so that automatic welding offers greater bending fatigue strength. 3) For one side fillet welded T-joint without edge preparation with automatic welding, the ratio(h/t) of the leg length(h) and the main plate thickness(t) in which toe crake can occur was 1.0 over.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1024-1030
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• 2007

We studied on the characteristics of many kinds of tank cars carrying hazard materials and performed structural strength evaluation for tank of asphalt tank car using finite element analysis. We analyzed the tank strength according to JIS E 7102(Design Method for Tanks of Tank Cars). It was found that the maximum stress obtained at the area supported by the saddle is much lower than the yield stress and the criteria of JIS E 7102.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.470-474
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• 1997

Since the ceramic/metal joints is joined at high temperature, the residual stress will develop during when cooled from bonding temperature due to remarkable difference of thermal expansion coefficient between creamic and metal. Moreover, the edge of jointed interface makes singular stress field in the ceramic/metal joints and this singular stress field much influences on the strength of joints. In this study, The influence of residual stress, mechanical load and repeat thermal sysle was estimated in the ceramic/metal joints. According to this influence, the change of singular stress field was analyed and then strength test, X-ray measurement are performed.

• 구강회복응용과학지
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• 제19권3호
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• pp.139-151
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• 2003

This study was to evaluate and to compare the compressive strength and the displacement effecting the abutment or the residual ridge which are transformed by the angle and the heights of the konus denture inner crown when restorating the unilateral konus denture by using the mandibular canine and the 1st premolar as an abutment. The author made 9 different models for different inner crown heights and konus angles. The inner crown height were divided to 5mm, 6mm, and 7mm and konus angles was divided to $4^{\circ}$, $6^{\circ}$, and $8^{\circ}$. And then in each model, 5kg of $15^{\circ}$ mesial load was stressed on the central fossa of the 1st premolar and the 1st molar. The stresses and displacement were measured using the finite element analysis. The results were as follows 1. The maximum compressive strength was shown on the connective area of the abutment and the denture base. 2. As the angle of the inner crown becomes increased, the compressive strength was shown smaller. 3. As the height of the inner crown becomes increased, the maximum compressive strength was shown smaller while the compressive strength of the root apex and the residual ridge showed larger. 4. When the stress was loaded only on the 1st premolar, the more compressive strength was concentrated on the root apex area of the 1st premolar. 5. When the stress was loaded only on the 1st premolar, the compressive strength was concentrated uniformly on the abutment and the residual ridge. 6. When the stress was loaded only on the 1st molar, the maximum displacement was shown on the distal part of the residual ridge.

• 한국포장학회지
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• 제7권2호
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• pp.25-30
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• 2001

Corrugated board is composed of cellulose fibers which are arranged with the same direction as the board manufactured. The direction is classified with machine direction (MD) and cross-machine direction (CD). Therefore, corrugated board is orthotropic material that has totally different strength properties at each direction and especially, at machine direction, the mechanical properties of fiberboard is superior. The compression strength of the corrugated fiberboard boxes is very important information to the manufacturers and the end users. This study was carried out to design the optimum pattern, size, and location of ventilating hole for ventilating container through the finite element analysis. The optimum pattern and location of ventilating and hand hole were vertical oblong, a short distance to the right and left from the center of panel, and center or a short distance to the top of both sides, respectively. We identified the effect on both stress dispersion and stress level from the analysis of redisigned hand hole.

• International Journal of Aeronautical and Space Sciences
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• 제16권4호
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• pp.537-547
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• 2015

A Monte Carlo (MC) simulation was conducted to predict the reliability of a newly developed pyrotechnic pin puller. The reliability model is based on the stress-strength interference model that states that failure occurs if the stress exceeds the strength. In this study, the stress is considered to be the energy consumed by movement of a pin shaft, and the strength is considered to be the energy generated by pyrotechnic combustion for driving the pin shaft. Failure of the pin puller can thus be defined as the consumed energy being greater than the generated energy. These energies were calculated using a performance model formulated in the previous study of the present authors. The MC method was used to synthesize the probability densities of the two energies and evaluate the reliability of the pin puller. From a probabilistic perspective, the calculated reliability was compared to a deterministic safety factor. A sensitivity analysis was also conducted to determine which design parameters most affect the reliability.