• 소성∙가공
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• 제11권2호
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• pp.138-146
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• 2002

This paper is concerned with the simulation-based process design method involved non-steady state problem of tension levelling considering the elasto-plastic hardening behavior of a metallic strip by a commercial code ABAQUS/Standard. The tension levelling process is peformed to elongate the strip plastically in combination of tensile and bending strain by a controlled manner so that all longitudinal fibers in the strip have an approximately equal amount of length and undesirable strip shapes are corrected to the flat share. Objectives of this paper are the development of a general method for the design of a tension leveller by a finite element method and parameter studies for the deisgn variables such as the applied tension, the roll intermash includes the determination of the steady state using the simple unit of the tension levelling line and the effect of the finite element mesh size on the amount and distribution of the strain calculated. The analysis provides the information about the intermesh effect on the amount and final shapes of the strip and distribution of the strain in order to determine the amount elongation for correction of the irregular share.

• 대한기계학회논문집
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• 제15권2호
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• pp.693-702
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• 1991

The existence of residual stress in the circumferential butt welded pipes is one of the most important problems concerning stress corrosion cracking in service. In this paper, the residual stress distributions in three kinds of circumferential butt welded pipes were measured by the hole drilling strain gage method and calculation using finite element method is performed and its results are compared with the experiments. At the inner surface of the pipe region near the center line of welding is under high tensile residual stress. However, as the distance from the center line of welding increases, the tensile component decreases and finally becomes compressive residual stress at region far away from the center line of welding. The longitudinal residual stress at the outer surface is compressive regardless of the diameter of pipe and the circumferential stress is changed rom compressive to tensile as pipe diameter increases. The results also demonstrate that the residual stress is mainly caused by self restraint bending force in the pipe welding.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.583-588
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• 2007

This paper investigates the vibration characteristics of a wire-bonding transducer horn for high speed welding devices. The sample wire-bonder uses the input frequency of 136 kHz. The ultrasonic excitation causes the various vibrations of transducer horn and capillary. The vibration modes and frequencies close to the exciting frequency are identified using ANSYS. The nodal lines and amplification ratio of the ultrasonic horn are also obtained in order to evaluate the bonding performance of the sample wire-bonder system. The FEM results and experimental results show that the sample wire-bonder system uses the bending mode of 136 kHz as principal motion for bonding. The major longitudinal mode exists at 119 kHz below the excitation frequency. It is recommeded that the sample system is to set the excitation frequency at 119 kHz to improve bonding performance.

• Journal of Welding and Joining
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• 제21권7호
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• pp.34-41
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• 2003

Weld quality monitoring and seam tracking along the butt-joint lengthwise to the tube axis are studied. The material of tube is 60kg/$\textrm{mm}^2$ grade steel sheet, and the longitudinal butt-joint is shaped by 2 roll bending machine. The tube with a thickness of 1.5mm, diameter of 105.4mm and length of 2000mm is successfully obtained by the $CO_2$ laser welding system equipped with a seam tracker and plasma sensor. Experimental results show that the developed welding system can be used for the precision seam tracking and the real-time monitoring of weld quality, and the laser welded tube can be used for car body md component after tubular hydroforming.

• 콘크리트학회지
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• 제10권6호
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• pp.233-240
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• 1998

구조역학에 기초한 보의 종방향 휨모멘트변화율과 전단력의 관계와 본 연구자가 이전에 발표한 아취모델을 이용하여 복부보강이 안된 철근콘크리트 보의 전단강도 예측식을 제안하였다. 이론적으로 유도된 본 연구의 전단강도식은 주로 실험결과에 기초한 ACI 318 전단강도식과 비슷한 형태이다. 본 연구에서 제안한 식은 콘크리트 압축강도, 주인장철근비 및 전단지간대 유효높이의 비가 주변수이며, 보작용과 아취작용의 조합에 의한 철근콘크리트 보의 전단저항메카니즘이 합리적으로 반영되어 있다. 본 연구에서 제안한 전단강도식은 ACI 318 전단강도식 및 Zsutty의 전단강도식과 함께 기존의 실험결과와 비교되었다.

• 한국안전학회지
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• 제23권2호
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• pp.14-20
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• 2008

The objective of this study is to examine fatigue strength of the welded details. In order to attain the goal of this study, the bending fatigue tests was performed for four kinds of welded details used in steel bridges, such as in-plane gusset, out-of-plane gusset, cruciform, and cover plate. The effect of the length of welded attachment on fatigue strength was greater in out-of-plane gusset than in in-plane gusset. The fatigue strength of welded details with short attachment was superior to that with long attachment. Fatigue strength of welded details with transversely loaded welds was lower than that with longitudinally loaded welds, and those results were not satisfied with AASHTO specifications. For the fatigue strength of cover plate, cover plate with rectangular section was superior to that with tapered section. It was found that the fatigue crack initiates at the points of stress concentration which are the boundary between the base metal and the bead of weld in the part of the longitudinal edge of attachment, and propagates first along the boundary and along the perpendicular to the direction of the principle stress in the base metal of welded tip.

• 복합신소재구조학회 논문집
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• 제1권1호
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• pp.9-15
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• 2010

In this paper, A reinforced concrete slab bridges is analyzed by the composite laminates theory. Both the geometry and the material of the cross section of the reinforced concrete slab bridge are considered symmetrical with respect to the mid-surface so that the bending extension coupling stiffness, Bij = 0, and D16 = D26 = 0. Each longitudinal and transverse steel layer is regarded as a lamina, and material constants of each lamina is calculated by the use of rule of mixture. This slab with simple support is under uniformly distributed vertical and axial loads. In this paper, the finite difference method and specially orthotropic laminates theory are used for analysis. The result of specially orthotropic laminates theory analysis is modified to obtain the solution of the beam analysis. The result of this paper can be used for reinforced concrete slab analysis by the engineers with undergraduate study in near future.

• Steel and Composite Structures
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• 제9권5호
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• pp.397-418
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• 2009

Eight panel specimens were tested in one-way bending to study the behaviour and capacity of composite slab joists consisting of cold-formed steel C-sections and concrete. Various shear transfer mechanisms were implemented on the C-section flange embedded in the concrete to provide the longitudinal shear resistance. Results showed that all specimens reached serviceability limit state while in elastic range and failure was ductile. Shear transfer achieved for all specimens ranged from 42 to 99% of a full transfer while specimens employed with shear transfer enhancements showed a greater percentage and therefore a higher strength compared with those relying only on surface bond to resist shear. The implementation of pre-drilled holes on the embedded flange of the steel C-section was shown to be most effective. The correlation study between the push-out and panel specimens indicated that the calculated moment capacity based on shear transfer resistance obtained from push-out tests was, on average, 10% lower than the experimental ultimate capacity of the panel specimen.

• Structural Engineering and Mechanics
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• 제68권4호
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• pp.485-495
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• 2018

This paper presents the results of an experimental study on the structural performance of an innovative GFRP-concrete composite beam construction, which is reinforced with longitudinal GFRP pultruded box-profile and transverse steel stirrups. GFRP perfobond (PBL) shear connectors are employed to enhance the bonding performance between the GFRP profile and the concrete portion. To investigate the shear and flexural performance of this composite system, eight specimens were designed and tested under three-point and four-point bending. The main variables were the height of the composite beam and the shear span-to-depth ratio. The test results indicated that bonding cracks did not occur at the interface between the GFRP profile and the concrete until the final stage of the test. This shows that the specimens performed well as composite beams during the test and that the GFRP PBL connectors were reliable. Based on the test results, two calculation methods were used to determine the flexural and shear capacity of the composite beams. A comparative study of the test and theoretical results suggests that the proposed methods can reasonably predict both the flexural and shear capacities of the specimens, whereas the provisions of ACI 440 are relatively conservative on both counts.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권2호
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• pp.127-136
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• 2016

Springing is the resonance phenomenon of a ship hull girder with incoming waves having the same natural frequency of the ship. In this study, a simple and reliable calculation method was developed based on quadratic strip theory using the Timoshenko beam approach as an elastic hull girder. Second-order hydrodynamic forces and Froude-Krylov forces were applied as the external force. To improve the accuracy of the strip method, the variation in the added mass along the ship hull longitudinal direction, so called tip-effect, was considered. The J-factor was also employed to compensate for the effect of three-dimensional fluid motion on the two-node vibration of the ship. Using the developed method, the first- and second-order vertical bending moments of the Flokstra ship were compared. A comparative study was also carried out for a uniform barge ship and a 10,000 TEU container ship with the respective methods including the J-factor and tip-effect.