• Journal of Welding and Joining
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• v.24 no.3
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• pp.27-33
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• 2006

Structural stress approach is well known as a mesh-size insensitive fatigue assessment method by using finite element analyses. It is, however, difficult to estimate the structural stress (SS) at weld end points due to stress singularities when shell elements are used. In this study, fatigue evaluations with longitudinal load carrying box fillet weldment under out-of-plane bending load have been performed by using virtual node method (VNM) in order to avoid the problem, which is called the weld end effect. Various combinations of virtual node parameters, such as reference point and virtual node locations, are investigated for the estimation of proper structural stress values applying VNM in a systematic manner. The appropriate guidance of virtual node parameter has been offered for the fillet weldment considered in the study. The structural stress values obtained by VNM have also been validated by comparing the result with finite element model including weld bead. Moreover, the fatigue strength of the fillet weldment based on the equivalent structural stress is shown to be consistent with the master S-N curve.

• Journal of Industrial Technology
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• v.21 no.B
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• pp.213-222
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• 2001

In the study, the fatigue strength improvement and mechanism have been estimated by the Spot-Heating treatment on welded bead toes. For this, web-gusset specimens were made without residual stresses and the others with residual stresses imposed by Spot-Heating. The 4-point bending tests were performed in order to estimate the effect of spot-heating on fatigue strength and fatigue characteristics quantitatively for non load-carrying fillet welded joints subjected to pure bending. As a result of fatigue test, fatigue strength of As-Welded specimen for non load-carrying fillet welded joints subjected to pure bending has satisfied the grade of fatigue prescribed in specifications of korea, AASHTO and JSSC. As compare with As-Welded specimen and Spot-Heating specimen have increased about 20% for the fatigue strength at $7.7{\times}10^6$ cycles. The Spot-Heating by reformation of the residual stress on welded bead toes has greatly affected the fatigue crack propagation life, but has slightly affected the fatigue crack initiation life.

• Journal of Ocean Engineering and Technology
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• v.17 no.2
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• pp.72-76
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• 2003

This paper presents the design concept and operation results of float-off for FSO (340,000 DWT Class, ELF AMENAM KPONO Project) built on the ground, without dry dock facilities. It was the first attempt to build FSO, completely, on the ground and launch it using DBU (Double Barge Unit, which was connected by rigid frame structure.) The major characteristics of FSO, which are similar to general VLCC type hull, including topside structure, weigh 51,000 metric ton. In order to have sufficient stability during the deck immersion of DBU, while passing through a minimum water plane area zone, proper trim control was completed with LMC (Load Master Computer). The major features of the monitoring system include calculation for transverse bending moment, shear force, local strength check of each connector, based on component stress, and deformation check during the load-out and float-off. Another major concern during the operation was to avoid damages at the bottom and sides of FSO, due to motion & movement after free-floating; therefore, adequate clearances between DBU and FSO were to be provided, and guide posts were installed to prevent side damage of the DBU casings. This paper also presents various measures that indecate the connector bending moment, damage stability analysis, and mooring of DBU during float off.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.6
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• pp.321-330
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• 2023

In this study, the structural performance of the specimen fabricated through 3D printing was evaluated through monotonic loading experiments analysis to apply to 3D printed structures. The compression and flexural experiments were carried out, and the experimental results were compared to the finite element model results. The loading directions of specimens were investigated to consider the capacity of specimens with different curing periods, such as 7 and 28 days. As a result, the strength tended to increase slightly depending on the stacking direction. Also, between the 3D-printed panel composite and the non-reinforced panel, the bending performance depended on the presence or absence of composite reinforcement.

• Structural Engineering and Mechanics
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• v.28 no.3
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• pp.281-294
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• 2008

In this paper, linear elastic isotropic structures under the effects of both stochastic operators and stochastic excitations are studied. The analysis utilizes the spectral stochastic finite elements (SSFEM) with its two main expansions namely; Neumann and Homogeneous Chaos expansions. The random excitation and the random operator fields are assumed to be second order stochastic processes. The formulations are obtained for the system solution of the two dimensional problems of plane strain and plate bending structures under stochastic loading and relevant rigidity using the previously mentioned expansions. Two finite element programs were developed to incorporate such formulations. Two illustrative examples are introduced: the first is a reinforced concrete culvert with stochastic rigidity subjected to a stochastic load where the culvert is modeled as plane strain problem. The second example is a simply supported square reinforced concrete slab subjected to out of plane loading in which the slab flexural rigidity and the applied load are considered stochastic. In each of the two examples, the first two statistical moments of displacement are evaluated using both expansions. The probability density function of the structure response of each problem is obtained using Homogeneous Chaos expansion.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1326-1330
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• 2008

The failure mode of steel road wheels in a vehicle is cracks from ventilation hole through to contact plane on steel wheel's disc plate. But a number of cracks of Cornering Fatigue Limit Test is on contact plane near to wheel nut mounting area, even though it's satisfied with specified cycles. So this paper searches out causes to improve durability and reliability of C.F.T by uni-axial bending moment test. The verified cause is a "fretting" on contact area of steel wheel. In result, this paper suggests a solution to prevent a fretting by inserting a damping shim, 0.7mm between steel wheel contact areas. Therefore this paper makes it possible to move crack position of C.F.T in steel wheel from contact plane to vehicle's failure mode.

• Structural Engineering and Mechanics
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• v.51 no.1
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• pp.111-130
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• 2014

The aim of this study is to investigate the effects of the beam aspect ratio(L/h), hole diameter, hole location and stacking layer sequence ($[0/45/-45/90]_s$, $[45/0/-45/90]_s$ and $[90/45/-45/0]_s$) on natural frequencies of glass/epoxy perforated beams under room and high (40, 60, 80, and $100^{\circ}C$) temperatures for the common clamped-free boundary conditions (cantilever beam). The first three out of plane bending free vibration of symmetric laminated beams is studied by Timoshenko's first order shear deformation theory. For the numerical analyses, ANSYS 13.0 software package is utilized. The results show that the hole diameter, stacking layer sequence and hole location have important effect especially on the second and third mode natural frequency values for the short beams and the high temperatures affects the natural frequency values significantly. The results are presented in tabular and graphical form.

• Proceedings of the KWS Conference
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• 2002.05a
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• pp.178-181
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• 2002

This is a partial report of the investigation of fatigue behaviour of hollow section T-joints with circular brace members and rectangular chord members (CRHS). Hot spot stresses and the stress concentration factors (SCFs) were determined experimentally. Fatigue testing was carried out under constant amplitude loading in air. The experimental SCF values for CRHS joints were found to be below those of circular-to-circular (CCHS) and rectangular-to-rectangular (RRHS) hollow section joints. The fatigue strength referred to experimental hot spot stress was in reasonably good agreement with current fatigue design codes for tubular joints.

• Tribology and Lubricants
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• v.15 no.2
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• pp.141-149
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• 1999

Fracture, fatigue and wear characteristics of Al-Si alloy used for compressor are experimentally studied. Plane strain fracture toughness test is carried out using three point bending specimen. Fatigue test is performed under constant loading condition and wear test is carried out as a function of sliding velocity and applied load. To obtain the crack propagation characteristics and wear mechanism of Al-Si alloy, fracture and worn surfaces are investigated using SEM. It is verified that fracture and fatigue strength of Al-Si alloy are improved by the fine microstructure of alloy. The wear behavior and specific wear amount of Al-Si alloy are not dependent on the microstructure but on a function of the silicon content. Anodizing on the surface of Al-Si alloy, surface hardness and wear characteristics are improved.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.480-483
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• 2005

A roll forming process is developed for an automotive part of high strength steel. Forming rolls are designed through the plane strain elastic-plastic finite element analysis to estimate the springback. It is assumed that the process can be approximated as a series of multi-step bending processes. Then the 3D elastic-plastic finite element analysis with the solid element is carried out for the designed roll forming process. The prototype roll forming machine and the forming rolls are made and the experiments are carried out. The results of the analysis and the experiments are compared.