• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.10
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• pp.52-58
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• 2020

Bellows are corrugated mechanical elements used to absorb displacements or vibrations caused by temperature changes, pressure, earthquakes, waves, etc., which are welded to flanges or directly connected to pipes. Expansion joint bellows must not only be designed to sufficiently withstand the internal pressure of the pipes but also accommodate axial, transverse, and rotational deformations to minimize the transfer of forces to the sensitive components of the system. Bellows have various types of corrugations, but U-type bellows are most commonly used in general piping systems. In this study, the behavior of U-shaped one-, two-, and three-ply bellows with the same inner diameter under pressure and forced displacement was analyzed using the finite element method. The results were compared with the design formula in the Expansion Joint Manufacturers Association (EJMA)'s code. Manufacturer data were used for the applied pressure and force displacement. The behavioral characteristics of the three cases were compared via structural analysis because the stress levels will be different for each model, even if they have the same inner diameter. Since the analytical model has an axisymmetric shape but displacement occurs in the transverse direction, the finite element model was composed of 1/2 of the whole model, and ANSYS Workbench 17.2 was employed for the analysis.

• Journal of Korean Society on Water Environment
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• v.29 no.6
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• pp.754-761
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• 2013

Urban floods are usually caused by the lack of drainage capacity. Hence, sewer capacity expansion methodology by replacing small pipes with bigger ones is primarily applied as a flood control measure. However, this approach is often unreasonable because of the costs and time involved. Thus, the installation of underground rainwater storage tanks with the two advantages of flood control and water conservation is proposed. This study compared the effectiveness of flood control by both the sewer expansion methodology and rainwater storage tanks using the Storm Water Management Model. Three cases were simulated in this study. The first case analyzed flood reduction by the storm sewer expansion methodology. The simulation results indicate that the overflow volume from manholes was reduced by 49% with this methodology. The second case analyzed flood reduction by installation of rainwater storage tanks. The simulation results indicate that the overflow volume was reduced by 62%. However, these two cases could not prevent urban floods completely. Hence, the third case analyzed the joint application of the storm sewer expansion methodology and rainwater storage tanks. In this simulation, flooding did not occur. Consequently, the results of this study clearly show that underground rainwater storage tanks are more effective for flood control than capacity expansion of storm sewer. Furthermore, the joint application of these two flood control measures is more effective than their separate application.

• Proceedings of the Korean Reliability Society Conference
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• 2004.07a
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• pp.221-226
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• 2004

The thermal stresses induced by difference in Coefficient of Thermal Expansion between FR-4 board and 63Sn-37Pb solder joint directly affect the reliability of 63Sn-37Pb solder joint. This research, thus, focuses to investigate the crack initiation and propagation behavior around solder joint by imposing a designed Acceleration Life Test Procedure on solder joint by using a newly manufactured Thermal Impact Experimental Apparatus. The fracture mechanism of the solder joint was found to be highly influenced by thermal stresses. The reliability of solder joint was evaluated by using a failure probability model in terms of varying parameters such as frequency and temperature. The relationship between failure probability and safety factor was also studied.

• Journal of Welding and Joining
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• v.17 no.6
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• pp.78-83
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• 1999

Solder joint is the weakest part which connects in mechanically and electronically between package body and PCB(Printed Circuit Board). Recently, the reliability of solder joint become the most critical issue in surface mounted technology. The solder joint interconnection between plastic package and PCB is susceptible to shear stress during thermal storage due to the mismatch in coefficient of thermal expansion between plastic package and PCB. A general computational approach to determine the effect of solder joint shape on the fatigue life presented. The thermal fatigue life was estimated from the engelmaier equation which was obtained from the temperature cycling loading($-65^{\circ}C$ to $150^{\circ}C$). As result of the simulation, TSOP structure has the shortest thermal fatigue life and the same structure Copper lead has 2.5 times as much fatigue life as Alloy 42 lead. In BGA structure, fatigue life time extended 80 times when underfill material exists.

• Steel and Composite Structures
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• v.46 no.4
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• pp.539-551
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• 2023

In order to study the fire resistance of castellated composite beams with ortho-hexagonal holes and different beam-end restraints, temperature rise tests with constant load were conducted on full-scale castellated composite beams with ortho-hexagonal holes and hinge or rigid joint constraints to investigate the temperature distribution, displacement changes and failure patterns of castellated composite beams with two different beam-end constraints during the whole course of fire. The results show that (1) During the fire, the axial pressure and horizontal expansion deformation generated in the rigid joint constrained composite beam were larger than those in the hinge joint constrained castellated composite beam, and their maximum horizontal expansion displacements were 30.2 mm and 17.8 mm, respectively. (2) After the fire, the cracks on the slab surface of the castellated composite beam with rigid joint constraint were more complicated than hinge restraint, and the failure more serious; the lower flange and web at the ends of the castellated steal beams with hinge and rigid joint constraint produced serious local buckling, and the angles of the ortho-hexagonal holes at the support cracked; the welds at both ends of the castellated composite beam with rigid joint constraint cracked. (3) Based on the simplified calculation method of solid-web composite beam, considering the effect of holes on the web, this paper calculated the axial force and displacement of the beam-end constrained castellated composite beams under fire. The calculation results agreed well with the test results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.1
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• pp.176-187
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• 2001

Most bridges have expansion joints to accommodate thermal expansion and contraction without inducing large forces in the bridges. To evaluate the effects of earthquake-induced at expansion joints of concrete bridges, the first part of this paper deals with a collinear impact between concrete segments, which have the same cross section but different lengths. Especially, impact force, momentum, strain energy and kinetic energy are formulated in mathematically. These results are then used in the second part of this paper to simulate a realistic yet simple analysis of seismic pounding in concrete bridges. Analysis of seismic pounding in idealized concrete bridges is carried out by using a simple lumped-mass model and rationally determined values of the coefficient of restitution and the duration of impact.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.806-811
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• 2004

Currently, in the design criteria for the high speed railway bridges, the maximum distance between bridge expansion joint is limited to 80m using a continuous welded mil, in order to limit the additional stress in the rail due to the rail-bridge interaction. In the past study on the resonance effect of HSR train, it is known that the reduction of resonance and dynamic responses of bridge deck occurs at the specific expansion length of 28.05m and 46.75m. In this study, the stability of track structure on the HSR bridges with expansion length of 90m has checked by finite element method. And the track behavior including mil stresses and relative displacements are compared to the current state of track structures on the bridge system with 80m long expansion length.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.3
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• pp.177-197
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• 2011

In this study, a series of fire experiments under $HC_{inc}$ and ISO834 (duration of 4 hour) fire scenarios were carried out for three different types of fire protection measures for the segment joint to evaluate their applicabilities to an immersed tunnel. The experimental results revealed that an expansion joint installed to allow relative movements between concrete element ends in an segment joint is the most vulnerable to a severe fire. For the fire protection measure where the originally designed steel plates at an expansion joint arc replaced by fire-resistant boards, the experiments showed that they cannot achieve good fireproofing performance under both $HC_{inc}$ fire scenario and ISO834 (4 hour) fire scenarios since the installation of fire-resistant boards results in the reduction of the sprayed fire insulation thickness. On the other hand, the application of modified bent steel plates replacing the original steel plates was proved to be very successful in fireproofing of the expansion joint due to more sprayed materials filled in bent steel plate than in the original design concept as well as higher adhesion between the steel plate and the sprayed fire insulation layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.11a
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• pp.49-54
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• 1993

This paper discusses the reliability of solder joints of electronic devices on printed circuit board. Solder application is usually done by screen printing method for the bonding between outer leads of devices and thick film(Ag/Pd) pattern on Hybrid IC as wel1 as Cu lands on PCB. As result of thermal stresses generated at the solder joints due to the differences of thermal expansion coefficients between packge body and PCB, Micro cracking often occurs due to thermal fatigue failure at solder joints. The initiation and the propagate of solder joint crack depends on the environmental conditions, such as storage temperature and thermal cycling. The principal mechanisms of the cracking pheno- mana are the formation of kirkendal void caused by the differences in diffusion rate of materials, ant the thermal fatigue effect due to the differences of thermal expansion coefficient between package body and PCB. Finally, This paper experimentally shows a way to supress solder joints cracks by using low-${\alpha}$ PCB and the packages with thin lead frame, and investigates the phenomena of diffusion near the bonding interfaces.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.749-752
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• 1996

A computer program was developed for the static analusis of a bridge expansion joint mechanism, which is called lazy-tong joint. I t was modelled as a plane truss and statically determinate structure under the assumption of small expansion in bridge girder. The applied load was assumed as a maxium wheel load exerted by a 40th tandem axied tractor-semitrailer truck. By using the developed computer program, reaction forces, axial and bending stresses, deflections, and critical buckling load, etc. of each structural member were analyzed. And they showed good agreement with those analyzed by the comercial F.E.M S/W, ANSYS.