• Journal of Advanced Marine Engineering and Technology
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• v.22 no.2
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• pp.139-145
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• 1998

Filament winding method is widely used for composite fabrications using low viscosity liquid for-mation and processing asymmetrical structures of pressure vessel pipe rocket motor case etc. The filament winding method is affected by several parameters such as pot life of process time viscosi-ty of resin filament winding temperature and schedules curing condition and post curing condi-tion of resin. To develope high functional composite materials the rotation(5, 15, 20, 30rpm) of the winding machine was controlled by D.C motor. And the wiper to give proper tension was equipped between strand and resin bath. The resin is hooked by the design wiper. The adequate cure schedule was found by DSC. NOL ring test is carried out to investigate the basic physical properties such as design technology. The void contents in filament winding is generally higher than that of the prepreg laminated plate. These high contents of void can make a crack in resin in spite of low deformation. These problem was solved by giving tension in processing. To improve the characteristics of fiber volume fraction void contents resin/fiber bonding the winding speedc is changed under constant tension. It was found that resin impregnation was not different from in fiber contents void contents at the range of 0.5~1kg tension but it was found that resin was not impregnated at the above of 1.5kg tension. In burst test a pure PE liner was failed at a nozzle part under the $14kg/\textrm{cm}^2$ pressure but a pressure vessel of CNG was failed at a cylinder part under the $200kg/\textrm{cm}^2$ pressure.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.997-1002
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• 2012

With the increasing demand for lightweight materials to reduce fuel consumption, especially in the transportation industry, magnesium alloys are being widely studied. However, there are several limitations to the large-scale application of magnesium alloys in a structure because of their low formability and strong anisotropy. In order to take into account both the strong anisotropy and tension-compression asymmetry of AZ31 sheet alloy, the Cazacu-Plunkett-Barlat yield criterion (Cazacu, 2006) was adopted in material modeling. The variation of the anisotropic coefficients that describe the yield surface evolution of AZ31 is optimized using an interpolation function based on specific calibration results. It generates continuous yield surfaces, which makes it possible to describe different hardening rates in tension and compression as well as the tension-compression asymmetry of magnesium alloys. The performance of the CPB06 yield criterion for simulating an axial crushing test was tested and compared with that of the Hill (1948) yield criterion.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.12
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• pp.3010-3017
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• 2000

For integrity evaluation of cracked or damaged structures, fracture toughness test results in ASTM are widely used. The fracture toughness values of the structures are used as an effective design criterion in nuclear plants and aircraft structures. Sometimes the difference of P-$\delta$ curve trend during the unloading /reloading cycle in the fracture toughness test using partial unloading compliance was observed. The phenomenon as a possible source of error in determining fracture toughness may be caused by the residual stress during unloading work-hardening and bucking of a specimen. Therefore, we evaluate the effect of bucking and compressive residual stress during the K-R and J-R testing using a finite element method.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.576-580
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• 2008

Rubber material properties and useful life evaluation are very important in design procedure to assure the safety and reliability of the rubber components. In this paper, the evaluation of characteristics and useful life prediction of rubber component for elevator cabin were experimentally investigated. The material test and accelerated heat-aging test were carried. Rubber material constants were obtained by curve fittings of simple tension, pure shear and bi-axial tension test data. Heat aging test results changes as the threshold are used for assessment of the useful life and time to threshold value were plotted against reciprocal of absolute temperature to give the Arrhenius plot. By using the rubber material and component test several useful life prediction equations for rubber component were proposed. Predicted useful life of rubber component for elevator cabin agreed fairly with the experimental lives.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.3
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• pp.1-6
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• 2019

Wettability is an important factor to decide solderability of solder, flux, other soldering-related materials and soldering conditions. The wettability also affects the reliability of solder joint. Wetting balance test is a good method for quantitatively measuring wettability between solder and substrate. The wetting balance test is easy to reproduce the wetting experiment and to measure the wetting time and force. And this test provides wetting curve to calculate the surface tension of the molten solder. Development of new solder has been continued in accordance with various and harsh environment in the electronics industry. In this paper, the principle of wetting balance test and recent research issues including nano-composite solder are explained.

• Geomechanics and Engineering
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• v.11 no.2
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• pp.177-195
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• 2016

To secure the stability of geotechnical infrastructures and minimize failures during the construction process, a number of support systems have been introduced in the last several decades. In particular, stabilization methods using steel bars have been widely used in the field of geotechnical engineering. Rock bolt system is representative support system using steel bars. Pre-stressing has been applied to enhance reinforcement performance but can be released because of the failure of head or anchor sections. To overcome this deficiency, this paper proposes an innovative support system that can actively reinforce the weak ground along the whole structural element by introducing an active tension bolt containing a spring unit to the middle of the steel bar to increase its reinforcement capacity. In addition, the paper presents the support mechanism of the active tension bolt based on a theoretical study and employs an experimental study to validate the performance of the proposed active tension bolt based on a down-scaled model. To examine the feasibility of the active tension unit in a pillar, the paper considers a pullout test and a small-scale experimental model. The experimental results suggest the active tension bolt to be an effective support system for pillar reinforcement.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.8
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• pp.680-688
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• 2001

In this paper, the fuzzy control with variable input gain is applied to maintain the consistent tension in the process of taking up and releasing texture. In the process of discharging web on one side rolling it on another, the take-up drum gets smaller on the release drum side as it gets bigger on the rolling side, thus it is necessary to change the balance of velocity between the sides. In order to solve the problem a tension controller is necessary. The PI control method has been employed to maintain the consistent tension, but the PI control method produces a problem which requires an experienced worker with the traits of the machine, in order to perform the fine adjustments according to the environment of the process. For solving the above problem, we apply fuzzy control to the tension system, in order to produce a uniform roll. For the performance test, the fuzzy controller does not need to revise the parameters. Therefore the fuzzy controller exhibits an excellent additivity for the tension system where the system is changed with time.

• Journal of the Korean Geotechnical Society
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• v.34 no.4
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• pp.13-25
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• 2018

When deformation occurs on slope reinforced with anchor, shear stress and bending stress are applied on the shear surface along the slip surface and increase of the shear deformation causes the tension force variation of the anchor. In this study, shear test was performed by measuring the tension force of the anchor by inducing shear deformation in vertical direction of the anchor using a large-scale direct shear test equipment in order to confirm the tension force variation of the anchor induced by shear deformation. The shear test was performed for 8 conditions which were classified according to the anchor reinforcement, separation distance (1D, 2D, 4D) from the shear surface to bonded part and the lateral-pressure condition (0.1 MPa, 0.2 MPa) of adjacent ground. As a result of the shear test, it was found that the separation distance and the lateral-pressure condition affect the shear force of the ground reinforced by anchor and the tension force of the anchor, and experimentally verified that the shear force variation is related to axial force variation of the anchor head and tip. Therefore, it was confirmed that the behavior of the bonded part induced by the shear deformation can be indirectly predicted by analyzing the tendency of the tension force variation of the anchor head.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.156-159
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• 2008

This paper introduces a remained tensile force estimation method using SI technique based on evolutionary algorithm for externally prestressed tendon. This paper applies the differential evolutionary scheme to SI technique. A virtual model test using ABAQUS 3 dimensional frame model has been made for this work The virtual model is added to the tensile force(28.5kN). Two set of frequencies are extracted respectively from the virtual test and the self-coding FEM 2 dimension model. The estimating tendon tension for the FEM model is 28.31kN. It is that the error in the tendon tension is 1% through the differential evolutionary algorithm. The errors between virtual model and the self-coding FEM model are assumed as the model error.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.60-64
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• 2001

In this paper, the tension-compression fatigue test method and the fatigue life characteristics of carbon fabric/epoxy laminate coupon are presented. To avoid the buckling during the compression, a proper design for the test coupons is essential. The critical buckling loads for the coupons are calculated by assuming the coupons as columns under two types of fixed conditions. The first is that both ends of each coupon are perfectly clamped, the second is that both ends of each coupon are simply supported. The strain-load curves are obtained by compressing the representative coupons, on each surface of which a strain gage is attached. The buckling loads obtained from the tests are all between the two calculated critical buckling loads. All the coupons are broken by the compression during the fatigue tests. It is estimated to be the reason that the fatigue load causes delamination before the eventual failure of each coupon, and sequentially the micro-buckling in the delaminated region drives each coupon into fatigue failure during the compression. The S-N curve, the fatigue life characteristics of carbon fabric/epoxy is obtained.