• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.4
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• pp.107-113
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• 2011

Coolant rubber hoses for automotive radiators under thermal and mechanical loadings can be degraded and thus failed due to the influences of the locally formed electricity. In this study, an advanced test method was developed to simulate the failure problem of the rubber hose. For carbon black filled EPDM (ethylene-propylene dine monomer) rubber used as a radiator hose material the ageing behaviors by the electro-chemical stresses combined with a tensile strain were analyzed. As the tensile strain increased, the current of the rubber specimen reduced indicating an increase of the internal defects and electrical resistance of the rubber specimen. Elongation at break and IRHD hardness rapidly decreased with increasing the ageing time. Both electro-chemical stress and mechanical tensile stress clearly accelerated the degradation of EPDM rubber.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.2
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• pp.239-246
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• 2003

This paper proposes engineering estimation equations of elastic-plastic J and COD fur axial through-wall cracked pipes under internal pressure. Based on detailed 3-D FE results based on deformation plasticity, the plastic influence functions for fully plastic J and COD solutions are tabulated as a function of the mean radius-to-thickness ratio, the normalized crack length. and the strain hardening. Based on these results, the GE/EPRI-type J and COD estimation equations are proposed and validated against the 3-D FE results based on deformation plasticity. For more general application to general stress-strain laws or to complex loading, the developed GE/EPRI-type solutions are re-formulated based on the reference stress concept. Such a reformulation provides simpler equations for J and COD, which are then further extended to combined internal pressure and bending. The proposed reference stress based J and COD estimation equations are compared with elastic-plastic 3-D FE results using actual stress-strain data for Type 316 stainless steels. The FE results for both internal pressure cases and combined internal pressure and bending cases compare very well with the proposed J and COD estimations.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.136-139
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• 2003

The combined effect of bioaugmentation of dechlorinating bacterial cultures and addition of iron powder (Fe$^{0}$ ) on reductive dechlorination of tetrachloroethylene (PCE) and other chlorinated ethylenes in a artificially contaminated soil slurry (60$\mu$mo1es PCE/kg soil) were tested. Two different anaerobic bacterial cultures, a pure bacterial culture of Desulfitobacterium sp. strain Y-51 capable of dechlorinating PCE to cis-1, 2-dechloroethylene (cis-DCE) and the other enrichment culture PE-1 capable of dechlorinating PCE completely to ethylene, were used for the bioaugmentation test. Both treatments introduced with the strain Y-51 and PE-1 culture (3mg dry cell weight/kg soil) showed conversion of PCE to cis-DCE within 40 days. The treatments added with Fe$^{0}$ (0.1 -1.0 %(w/w)) alone to the soil slurry resulted in extended PCE dechlorination to ethylene and ethane and the, dechlorination rate depended on the amount of Fe$^{0}$ added. The combined use of the bacterial cultures with Fe$^{0}$ (0.1-1.0%) showed the higher PCE dechlorination rate than the separated application and the pattern of PCE dechlorination and end-product formation was different from those of the separated application. These results suggested that the combined application of Fe$^{0}$ and the bactrial culture, specially the complete dechlorinating enrichment culture such as PE-1 culture, would be practically effective for remediation of PCE contaminated soil.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.15 no.2
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• pp.31-39
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• 2019

Cracked component analysis is needed for structural integrity analysis under seismic loading. Under large amplitude cyclic loading conditions, the change in material properties can be complex, depending on the magnitude of plastic strain. Therefore the cracked component analysis under cyclic loading should consider appropriate cyclic hardening model. This study introduces a procedure for determining an appropriate cyclic hardening model for cracked component analysis. The test material was nuclear-grade TP316 stainless steel. The material cyclic hardening was simulated using the Chaboche combined hardening model. The kinematic hardening model was determined from standard tensile test to cover the high and wide strain range. The isotropic hardening model was determined by simulating C(T) test under cyclic loading using ABAQUS debonding analysis. The suitability of the material hardening model was verified by comparing load-displacement curves of cyclic C(T) tests under different load ratios.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.10a
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• pp.461-468
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• 1998

• Geomechanics and Engineering
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• v.14 no.4
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• pp.367-376
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• 2018

Samples composed of coal and rock show different mechanical properties of the pure coal or rock mass. For the same coal seam with different surrounding rocks, the frequency and intensity of rock burst can be significantly different in. First, a method of measuring the strain variation of coal in the coal-rock combined sample was proposed. Second, laboratory tests have been conducted to investigate the influences of rock lithologies, combined forms and coal-rock height ratios on the deformation and failure characteristics of the coal section using this method. Third, a new bursting liability index named combined coal-rock impact energy speed index (CRIES) was proposed. This index considers not only the time effect of energy, but also the influence of surrounding rocks. At last, a new approach considering the influences of roof and/or floor was proposed to evaluate the impact capability of coal seam. Results show that the strength and elastic modulus of coal section increase significantly with the coal-rock height ratio decreasing. In addition, the values of bursting liability indexes of the same coal seam vary greatly when using the new approach. This study not only provides a new approach to measuring the strain of the coal section in coal-rock combined sample, but also improves the evaluation system for evaluating the impact capability of coal.

• Structural Engineering and Mechanics
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• v.41 no.4
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• pp.509-525
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• 2012

In recent years, CFRP material usage in strengthening applications gradually became widespread. Especially, the studies on the strengthening of shear deficient reinforced concrete beams with CFRP strips are chosen as a subject to numerous experimental studies and research on this subject are increased rapidly. The most important variable, that is affected on the failure mode of CFRP strips and that is needed for determining the shear capacity of the strengthened reinforced concrete beams, is the strain distribution between CFRP strips and concrete. Numerous experimental studies are encountered in the literature about the determination of strain distribution between CFRP strips and concrete. However, these studies mainly focused on the CFRP strips under axial tension. There are very limited numbers of experimental and analytic studies examining the strain distribution between concrete and CFRP strips, which are under combined stresses due to the effects of shear force and bending moment. For this reason, existing experimental study in the literature is used as model for ANSYS finite element software. Nonlinear finite element analysis of RC beams strengthened against shear with CFRP strips under reverse cyclic loading is performed. The strain distributions between CFRP strips and concrete that is obtained from finite element analysis are compared with the results of experimental measurements. It is seen that the experimental results are consisted with the results derived from the finite element analysis and important findings on the strain distribution profile are reached by obtaining strain values of many points using finite element method.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10b
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• pp.1018-1021
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• 1988

This study is concerned with modeling an elastomer constitutive relation by utilizing the truncated Volterra series. Actual experimental data from the Instron Tester are obtained for combined input, i.e. constant strain rate followed by a constant strain input. These data are then estimated for step inputs and utilized for the truncated Volterra series models. One second order and one third order truncated Volterra series models have been employed to estimated the force-displacement relation which is one of the prominent properities to characterize the viscoelastic material. The third order Volterra series model has better results, compared with those of the second order Volterra series model.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.04a
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• pp.47-52
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• 1992

The entire nonlinear behavior of reinforced concrete frames up to collapse, is analyzed by the displacement control method and the combined layered and nonlayered method. All of the rigidities of section are calculated approximately by a sum over all the layers for the layered method, are used the integral values over the cross section area for the nonlayered method. The spurious sensitivity to the chosen element size in the result of analysis by finite element method for the materials with strain-softening can be overcome by modifying the strain distribution based on the concept of fracture energy at plastic hinge considering the applied axial load.

• Journal of the Korean Society of Safety
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• v.8 no.4
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• pp.16-20
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• 1993

The combined effect of increased pressure/temperature and the reduced material thicknesses act to increase the stress on the radiator componets. The design life of the radiator is influenced by the cyclic stresses and corrosion, which act to weaken the materials, radiator mechanical failure occurs when a tube or solder Joint ruptures, causing coolant loss or insufficient heat rejection. Therefore, in this study, through strain measurement of the tubes in copper/brass radiator, the strain distribution of the tubes in radiator as function of temperature and pressure is obtained.