• Korean Journal of Materials Research
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• v.2 no.2
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• pp.133-142
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• 1992

The slow strain-rate test($1{\times}10^{-4}~1{\times}10^{-7}sec^{-1}$) was performed to understand the tensile properties of chopped strand glass mat/polyester composite in air and synthetic sea water. (pH 6.0, 8.2, 10.0) For the tested composite subjected to tensile loading in air and synthetic sea water (ph 6.0, 8.2, 10.0), the tensile properties are a little decreased as strain rate decrease and a little decrease in stiffness is observed in $1{\times}10^{-7}sec^{-1}$. The tensile properties were some changed in case the pH value in synthetic sea water is varied.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.11
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• pp.3433-3440
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• 1996

This paper was investigation of the stres corrosion cracking(SCC) mechanism and the properties of corrosion fracture surface of glass fiber reinforced plastics(GFRP) produced by hand lay up(HLU) method in synthetic sea water. Test material is GFRP, that was used vinylester type epoxy acrylate resin and an unsaturated polyester as the matrix and the chopped strand mat(CSM) type E-glss fiber as the reinforcement. The slow strain rate test(SSRT) was performed on dry, wet and saturated wet specimens in sea water. Here the pH concentration of synthetic sea water was 8.2 and the strain rate is 1 x $10^{-6}$($sec^{-1}$) and test temperature ranges varied from $-60^{\circ}C$ to $80^{\circ}C$. It could be confirmed the fact that wet specimens tested at a particular test temperature ranges were appeared the eviences of SCC such as con-planar, mirror and hackle zone. Moreover, SCC of GFRP in sea water was characterised by falt fracture surfaces with only small amounts of fiber pull-out, in partial.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.12
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• pp.1864-1870
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• 2004

A spot welded structures have an influence on a diverse climatic situation, for instance temperature, humidity and precipitation. In addition factors of environmental pollution such as acid rain, that courses corrosion, have the tendency to increase. But spot welded structures strength is affected by humidity and environment temperature. Therefore, it is important to evaluate effect of temperature and water immersion on strength properties of spot welded part. In this study, the strength distribution of spot welded plates is evaluated the environmental temperature of zinc coated steel plates. Test is conducted with welded part immersed in distilled and synthetic sea water. Specimens are immersed into water for 10, 100, 500 and 1000 hours to evaluate the offsets of water immersion time on tensile-shear strength under the conditions of -40, 0, 20 and 5$0^{\circ}C$. From this result, spot welded specimens with 5 mm clearance have lower tensile-shear strength in the distilled water or synthetic sea water than without clearance. And they have lower tensile-shear strength under -4$0^{\circ}C$ and over 5$0^{\circ}C$.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.358-363
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• 2003

Spot welded structure is operated in diverse situation because of temperature, humidity and precipitation. In addition factors of environmental pollution such as acid rain, that courses corrosion, have the tendency to increase, But spot welded structure strength is affected by dampness and environment temperatures. Therefore, it is important to evaluate effect of temperature of spot welded part, In this study, the strength distribution of spot welded plates is evaluated about the environmental temperature of zine coated steel plates and test is conducted with welded part immersed in distilled and synthetic sea water. Specimens are immersed into water for 10, 100, 500 and 1000hours to evaluate the effects of water immersion time on tensile-shear strength under the conditions of -40, 0, 20 and $50^{\circ}C$. Strength is evaluated by tensile-shear test. The conditions of spot welding are 240kgf electrode force, 10KA welding current with 0 and 5mm clearance. From this study, spot welded specimens with clearance have lower tensile-shear strength in the distilled water or synthetic sea water comparing with spot welded specimens without clearance. And they have lower tensile-shear strength under $-40^{\circ}C$ and over $50^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1351-1360
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• 1993

The fatigue behavior of GFRP composites is affected by environmental parameters. Therefore, we have to study on effect of sea water on fatigue behavior of GFRP composites as to maintain the safety and confidence in design of ocean structure of GFRP. In this paper, we investigated the fatigue properties of chopped strand glass mat/polyester composite in synthetic sea water. (pH 8.2) In case of the glass fiber (CSM type) reinforced polyester composite materials, the fatigue crack in the both dry and wet specimens tested in air or synthetic sea water occurred at the initial of cycle. Thereafter, it was divided with two regions that one decreased with the crack extension and the other increased with the crack extension. The transition point occurred during the crack propagation shifted to high ${\Delta}K$ value as load increase but its point is not changed regardless of immersion or test environment under a constant load. The synthetic sea water degrades the bond strength between fiber and matrix, thereby the tendency of rapid deceleration and acceleration of the crack growth was appeared.

• Journal of Mechanical Science and Technology
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• v.15 no.10
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• pp.1380-1385
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• 2001

This paper evaluates the fatigue fracture behavior of a chopped strand glass mat/polyester composite both in ai, and sea water, Bending fatigue (R=-1) was performed on dry and wet specimens, that is respectively in air and sea water. Where the pH concentration of sea water was controlled to 6.0,8.2, 10.0 and the wet specimens were immersed in the sea waters for 4 months. Throughout the tests, fatigue cracks both in the dry and wet specimens, tested in the air or sea water, occurred at the beginning of the cycle, followed by either of two regions one decreasing and the other increasing as the crack growth rate increases.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.2
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• pp.185-194
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• 2016

It is essential for generating the synthetic image to test and evaluate a guided missile system in the hardware-in-the-loop simulation. In order to make the evaluation results to be more reliable, the extent of fidelity and rendering performance of the synthetic image cannot be left ignored. There are numerous challenges to simulate the LWIR sensor signature of sea surface depending on the incident angle, especially in the maritime environment. In this paper, we investigate the key factors in determining the apparent temperature of sea surface and propose the approximate formula consisting of optical characteristics of sea surface and sky radiance. We find that the greater the incident angle increases, the larger the reflectivity of sea surface, and the greater the water vapor concentration in atmosphere increases, the larger the amount of sky radiance. On the basis of this information, we generate the virtual maritime environment in LWIR region using the SE-WORKBENCH, physically based rendering software. The margin of error is under seven percentage points.

• Proceedings of the KWS Conference
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• 1994.10a
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• pp.64-67
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• 1994

• Bulletin of the Korean Chemical Society
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• v.21 no.9
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• pp.855-859
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• 2000

An application of synergistic solvent extraction for the etermination of trace lithium in sea water has been studied by forming an adduct complex of thenoyltrifluoroacetone (TTA) and trioctylphosphine oxide (TOPO) in a solvent. The interference by major constituents in sea water was eliminated by phosphate precipitation. Ex-perimental conditions such as solution pH, concentrations of TTA and TOPO etc. were optimized in synthetic sea water with similar compositionto its natural counterpart. To eliminate the interference, 1.38g of ammoni-um dihydrogen phosphate and 2.5 mL of ammonia water were added into 100 mL of thediluted solution at $60^{\circ}C$ to form the phosphate precipitates of Ca2+ and Mg2+ ions. After the pH of this filtrate was adjusted to 8.0, 10.0 mL of m-xylene containing 0.1 M TTA and 0.05 M TOPO was added to the solution in a separatory funnel, and the solution was shaken vigorously for 20 minutes. The solvent was separated from the aqueous solution, and 20 uL of m-xylene solution was injected into a gaphite tube to measure the absorbance by GF-AAS. The detection limit was 0.42 ng/mL. Lithium was determined within the range of 146 to 221 ng/mLin Korean coast-al sea waters, and the recoveries in the spiked samples were 94 to 106%.

• Journal of Welding and Joining
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• v.13 no.1
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• pp.78-88
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• 1995

This paper was performed to study the utility of the SP(small punch) test and the AE(acoustic emission) test in the evaluation of SCC(stress corrosion cracking) susceptibility for parent metal and bond line of HT80 steel-weld joint by SAW(submerged arc welding) with the various pH values. The loading rate used was 3*10$^{-4}$ mm/min and the corrosive environment used was synthetic sea water during the SP test and the AE test. According to the test results, the SCC susceptibility of the parent metal was increased in the order of pH6.0, pH8.2 and pH10.0. On the other hand, the bond line showed almost the same high SCC susceptibility in all pH concentrations. Synthetically, from the results of the SCC susceptibility, the macro- and micro-SEM observation, the microfracture behaviors by AE test and the relationship between SCC susceptibility and displacement at incipient failure, .delta.$_{i.f-AE}$, it can be concluded that the SP test and the AE test are the good test methods to evaluate the SCC susceptibility for parent metal and bond line of the weld joint with the change of environmental factors.