• Korean Journal of Materials Research
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• v.11 no.4
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• pp.266-271
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• 2001

Effect of Cd addition on the stress corrosion cracking(SCC) resistance of Al-Cu-Mn cast alloy was investigated by C-ring test and electrical conductivity measurement. With increasing Cd contents, the electrical conductivity and the SCC resistance were increased. The PFZ and coarse precipitates along the grain boundary were observed from TEM micrographs. The fracture made of the alloys was confirmed as intergranular type and showed brittle fracture surface. As a result, it was concluded that the SCC mechanism of these alloys is the anodic dissolution model. The maximum hardness was increased from 127Hv in the Cd-free alloy to 138∼145Hv in the Cd addition alloys.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.655-662
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• 2014

This study conducted tensile tests on an Alloy 690TT tube at room temperature (RT) and at $343^{\circ}C$ using tube- and ring-type specimens to investigate the stress-strain behavior and tensile properties of a steam generator (SG) tube in the axial and circumferential directions at RT and at the design temperature of a nuclear power plant (NPP). The results of the axial tensile test showed that yield point phenomena appeared at both RT and $343^{\circ}C$, and serrated flow in the stress-strain curve appeared at $343^{\circ}C$. Yield and tensile strengths for both directions were clearly lower at $343^{\circ}C$ compared to RT; however, the elongations were approximately the same at both test temperatures. Regardless of the test temperature, the strengths in the circumferential direction were lower by approximately 5~10 % than those in the axial direction. In addition, the test data revealed that the reduction in the yield and tensile strengths of the Alloy 690TT SG tube with the test temperature was more significant than that estimated by the temperature correction factor of ASME Sec.II.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.46-51
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• 2019

Intermittent CSR testing was used to investigate the degradation of a NBR O-ring, and also the prediction of its life-time. An intermittent CSR jig was designed taking into consideration the O-ring's environment under use. Degradation of O-rings by thermal aging was observed between $40^{\circ}C$ and $120^{\circ}C$. O-rings showed non-linear degradation behavior under $80^{\circ}C$. At 20% of failure condition, predicted life-times were 32.5 years by Arrhenius plot and 22.6 years by WLF plot.

• International Journal of Highway Engineering
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• v.7 no.2 s.24
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• pp.97-107
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• 2005

Since the purpose of wheel tracking test is to find out relative difference of mixture's rut resistance, the wheel is an important part in the test for obtaining a consistent output. This study is performed to examine efficiency of different wheel material, rubber and steel in wheel tracking test. The rubber was inserted as a ring on the outer face of the steel wheel, and thickness of rubber ring was 15mm and 7.5mm and 0mm (steel wheel without rubber), making the total outer diameter 200mm. The objective of this study was to select reliable wheel material type in wheel tracking test at $60^{\circ}C$ based on variance in output (rut depth and dynamic stability) and correlation with SD (deformation strength). The result of regression analysis of rut depth with Sd showed that $R^2$ values of wheel rubber thickness of 15mm, 7.5mm and 0mm were 0.7, 0.8 and over 0.9, respectively. In a case of steel wheel (0mm), the highest $R^2$ value was 0.9569. Therefore, the wheel without rubber ring was the best in output consistency level and coefficient of determination $(R^2)$ with deformation strength. Therefore, the steel wheel without rubber ring is suggested as the best choice for wheel tracking test of asphalt concrete.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1015-1021
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• 2010

In this study, the effect of the C/SiC composition ratio on the impact damage of a reaction sintered SiC (RS-SiC) plates was evaluated. An impact test was conducted by using an air gun. The impacter used was a steel ball with a diameter of 2 mm, and the impact velocities were 113, 122, and 180 m/s. The RS-SiC plates were $20\times20\times3$ mm with different C/SiC composition ratios. The ring crack diameters damaged by a steel ball were determined using SEM images. It was observed that the maximum diameter increased with increasing impact velocity, and it rapidly changed with increasing C/SiC composition ratio because of the effect of residual Si and the variation flexural strength. Cone cracks were formed in the case of C/SiC composition ratios of 0.4~0.5, this indicated that the impact damage changed from a ring crack to a cone crack in this critical range of C/SiC composition ratios. The C/SiC composition ratio of 0.3 was determined to be the optimal ratio for the RS-SiC manufacturing process.

• Journal of Advanced Marine Engineering and Technology
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• v.15 no.4
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• pp.29-45
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• 1991

Lip type stern tube sealing systems have used in almost all the middle or large ships which are being constructed in these days. It seems that the pressure fluctuation of the seal ring interspace, the cross-section profile and the materials quality of the seal rings have great effects on the sealing fuction of this sealing system. In this paper, the mechanical movement of lip seal ring which plays the most important role in stern tube sealing system and the possibility of leakage caused by pressure fluctuation are studied by theory and experiment. Using the finite element method for the axi-symetric object which receives the torsional load, the displacement and stress analysis of the seal rings, and also the possibility of crack occurance is checked by theoretical analysis. If the force which seal ring lip periphery receives is too small, there will be the possibility of leakage caused by the pressure fluctuation of the seal ring interspace, and if this force is too large, the frictional force between the seal ring and the liner will become problematical. The possibility of leakage caused by hardening of seal ring materials and creep phenomena of tested seal rings are also examined. The trial seal rings were designed and manufactured using the program of displacement and stress analysis developed in this study and the experimental apparatus to test the trial seal rings was also designed and manufactured. This trial seal rings were fitted in the experimental apparatus which was made in the same form as an actual stern tube. The one side of this apparatus was filled with sea water and the other side of it was filled with the lubricating oil. The leakage of oil and sea water was checked and the temperature was measured, rotating the propeller shaft at the constant velocity by D.C. motor. It was proved that the trial seal rings made in Viton rubber functioned excellenty but the trial seal rings made in N.B.R. rubber had problem in its durability.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.7
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• pp.1044-1051
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• 2009

During contact between surfaces, there is wear and the generation of wear. The particles contained in the lubricating oil carry detailed and important monitoring information about the condition of the machine. Therefore, this paper was undertaken for the Ferrography system of wear debris generated from a lubricated moving machine surface. The lubricating wear test was performed under different experimental conditions using the Falex wear test of the Pin and V-Block types by Ti(C,N) coated. It was shown from the test results that wear particle concentration(WPC), wear severity index(Is) and size distribution have come out all higher with increases in sliding friction time. With the Ferrogram thin leaf wear debris as well as ball and plate type wear particles were observed.

• Corrosion Science and Technology
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• v.3 no.1
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• pp.6-13
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• 2004

The effect of inhibitors on the electrochemical behavior and the stress corrosion cracking resistance of Alloy 600(UNS N06600) was evaluated in 10% sodium hydroxide solution at $315^{\circ}C$. The specimens of a C-ring type for stress corrosion cracking test were polarized at 150 mV above the corrosion potential for 120 hours with and without inhibitors such as titanium oxide, titanium boride and cerium boride. The chemical compositions of the films formed on the crack tip in the C-ring specimens were analyzed using a scanning Auger electron spectroscopy. The cerium boride, the most effective, was observed to decrease the crack propagation rate more than a factor of three compared with that obtained in no inhibitor solution. It was found that the changes of the active-passive transition potentials and the film compositions were related to the resistance to stress corrosion cracking in high temperature caustic solution.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.383-388
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• 2001

Effects of particle property variation of cone crack shape according to impact velocity in silicon carbide materials were investigated. The damage induced by spherical impact having different material and size was different according to materials. The size of ring cracks induced on the surface of specimen increased with increase of impact velocity within elastic contact conditions. The impact of steel particle produced larger ring cracks than that of SiC particle. In case of high impact velocity, the impact of SiC particle produced radial cracks by the elastic-plastic deformation at impact regions. Also percussion cone was formed from the back surface of specimen when particle size become large and its impact velocity exceeded a critical value. Increasing impact velocity, zenithal angle of cone cracks in SiC material was linearly decreasing not effect of impact particle size. An empirical equation, $\theta=\theta_{st}-\upsilon_p(180-\theta_{st})(\rho_p/\rho_s)^{1/2}/415$, was obtained from the test data as a function of quasi-static zenithal angle of cone crack($\theta_{st}$), the density of impact particle(${\rho}_p$) and specimen(${\rho}_s$). Applying this equation to the another materials, the variation of zenithal angle of cone crack could be predicted from the particle impact velocity.

• Corrosion Science and Technology
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• v.2 no.2
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• pp.82-87
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• 2003

Stress corrosion cracking of Alloy 600 and Alloy 690 has been studied with a C-ring specimen in 1%, 10% and 40% NaOH at $315^{\circ}C$. SCC test was performed at 200 mV above corrosion potential. Initial stress on the apex of C-ring specimen was varied from 300 MPa to 565 MPa. Materials were heat treated at various temperatures. SCC resistance of Ni-$_\chi$Cr-10Fe alloy increased as the Cr content of the alloy increased if the density of an intergranular carbide were comparable. SCC resistance of Alloy 600 increased in caustic solution as the product of coverage of an intergranular carbide in grain boundary, intergranular carbide thickness and Cr concentration at grain boundary increased. Low temperature mill annealed Alloy 600 with small grain size and without intergranular carbide was most susceptible to SCC. TT Alloy 690 was most resistant to SCC due to the high value of the product of coverage of an intergranular carbide in grain boundary, intergranular carbide thickness and Cr concentration at grain boundary. Dependency of SCC rate on stress and NaOH concentration was obtained.