• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.1
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• pp.82-87
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• 2012

For different ferrite-pearlite matrix structure, contain more than 90% spheroidal ratio of graphite, GCD 45-3, GCD 50, GCD 60 series and 70%, 80%, 90% spheroidal ratio of graphite, GCD 40, GCD 45-1, GCD 45-2 series, this paper has carried out rotary bending fatigue test, estimated maximum and mean size of spheroidal graphite, investigated correlation. It was concluded as follows. (1) Fatigue limit in $10^7$cycles and numbers of spheroidal graphite per 1$mm^2$ was linear relation. (2) projection area of graphite can be used to predict fatigue limit of Ductile Cast Iron. The Statistical distribution of extreme values of projection area of defects may be used as a guideline for the control of inclusion size in the steelmaking processes.

• Steel and Composite Structures
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• v.4 no.3
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• pp.227-246
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• 2004

This paper presents a moment-curvature method that accounts for the strength deterioration of steel at elevated temperature in estimating the response of steel beams exposed to fire. A modification to the EC4 method is proposed for a better estimation of the temperature distribution in the steel beam supporting a concrete slab. The accuracy of the proposed method is verified by comparing the results with established test results and the nonlinear finite element analysis results. The beam failure criterion based on a maximum strain of 0.02 is proposed to assess the limiting temperature as compared to the traditional criteria that rely on deflection limit or deflection rate. Extensive studies carried out on steel beams with various span lengths, load ratios, beam sizes and loading types show that the proposed failure criterion gives consistent results when compared to nonlinear finite element results.

• Geomechanics and Engineering
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• v.15 no.4
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• pp.937-945
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• 2018

A probabilistic study of a reinforced earth wall in a frictional soil using the surface response methodology (RSM) is presented. A deterministic model based on numerical simulations is used (Abdelouhab et al. 2011, 2012b) and the serviceability limit state (SLS) is considered in the analysis. The model computes the maximum horizontal displacement of the wall. The response surface methodology is utilized for the assessment of the Hasofer-Lind reliability index and is optimized by the use of a genetic algorithm. The soil friction angle and the unit weight are considered as random variables while studying the SLS. The assumption of non-normal distribution for the random variables has an important effect on the reliability index for the practical range of values of the wall horizontal displacement.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.06b
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• pp.8-18
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• 1998

The effect of press warm forming in cylindrical deep drawing of stainless-aluminum clad sheet metals are examined . The temperature of die and blank holder is varied from room temperature to 20$0^{\circ}C$, while the punch is kept cooled during test to increase the fracture strength of workpiece on the punch corner area. Test materials chosen for experiments are STS304-Al050-STS304, STS304-A1050-STS430-, STS304 and Al050 metals and teflon film as a lubricant is used on both sides of a workpiece. The limit drawing ration as well as quality of drawn cups (distribution of thickness and hardness)are investigated and discussed.

• Journal of Korean Society for Quality Management
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• v.33 no.1
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• pp.1-10
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• 2005

This paper develops a new VSI $\={X}-CRL$ synthetic control chart that considers convenience of use in the field, and perception of change of process applying VSI techniques to synthetic control chart, simultaneously. We found the optimal sampling interval and various control limit factor of the suggested chart using markov chain. Comparison and analysis is carried out between synthetic VSI $\={X}-CRL$ chart and other chart in the statistical aspect; $\={X}$ control chart, VSI $\={X}$ chart, another synthetic chart. In case that the process follows normal distribution, the proposed VSI $\={X}-CRL$ synthetic control chart in detecting process mean shift showed the best performance in aspect of statistical performance, regardless of control limit L of CRL/S control chart.

• Journal of Korean Society for Quality Management
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• v.20 no.2
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• pp.11-20
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• 1992

We discuss the feed back control of the on-line QC in the Taguchi method. Taguchi(1982) used the assumptions that the quality characteristics follow an uniform distribution and the Brownian motion to draw the loss function and proposed ${\Delta}/3$ or ${\Delta}$ for the initial control limit. Adams and Woodall(1989) also proposed a different procedure but using the same loss function. We propose, in this paper the new loss function under the assumption of mainly Brownian motion and compare the results with the results of the above.

• Economic and Environmental Geology
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• v.20 no.3
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• pp.159-168
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• 1987

Some physico-chemical properties such as surface area, moisture content, cation exchange capacity, swelling rate, pH, viscosity and liquid limit have been determined for evaluation of Cabentonite deposit occurring in four localities; Yonil, Gampo, Haseo and Pohang, in Gyeongsang-do. Montmorillonite contents can be derived from surface area measurement. Enhancement of liquid limit values and swelling volume were observed in the samples which had higher exchangeable Na ion and finer particle-size distribution. Identical results were observed even in the Na-exchanged samples. This suggests that aggregation effects have a great influence on physico-chemical properties. Aggregation of montmorillonite were controlled not only burial depth but also composition of exchangeable cation. Consequently, sample occurred in Yonil area where has the greatest burial depth in the area show somewhat lower physico-chemical properties than those of samples occurred in the other localities. However, the basic test applied in this study provides very useful preliminary information relating to its commercial potential.

• Proceedings of the Korean Reliability Society Conference
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• 2000.04a
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• pp.63-70
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• 2000

Brown and Proschan(1983) introduced a model for imperfect repair. At each feilure of a device, with probability p, it is repaired completely or replaced with a new device(perfect repair), and with probability 1 - p, it is returned to the functioning state, but it is only recovered to its condition just prior to failure(imperfect repair or minimal repair). In this paper, we limit the number of consecutive minimal repairs by n. We find some useful properties about ${\mu}$$\_$k/, the expected time between the k-th and the (k + 1)-st repair under the assumption that only minimal repairs are performed. Then, we assign cost to each repair and find the value of n which minimizes the long-run average cost for a fixed p under the condition that distribution F of the device is DMRL.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.45
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• pp.319-328
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• 1998

In this paper, the design of ALT(Accelerated Life Test) requires a sampling plan based on failure-censored(Type II censored) ALT with lognormal life distribution. Specially the environmental effect of products has been emphasized, so we considered the upper life limit as well as lower life limit in the ALT sampling plan. The optimal plan with a high stress and a low stress is used as test plan, and the total sample size for test and lot acceptability constant which minimize an asymptotic variance of maximum likelihood estimator of assumed model parameters and satisfy the given producer's risk and customer's risk are drawn out. These values can be acquired by means of the computer program that we coded for resolving the difficulty and complexity of calculation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.132-137
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• 2002

The mold transformers have been widely used in underground substations in large building and have some advantages in comparison to oil-transformer, that is low fire risk, excellent environmental compatibility, compact size and high reliability. In addition, the application of mold transformer for outdoor is possible due to development of epoxy resin. The mold transformer generally has cooling duct between low voltage coil and high voltage coil. A mold transformer made by one body molding method has been developed for small size and low loss. The life of transformer is significantly dependent on the thermal behavior in windings. To analyse winding temperature rise, many transformer designer have calculated temperature distribution and hot spot point by finite element method(FEM). Recently, numerical analyses of transformer are studied for optimum design, that is electric field analysis, magnetic field, potential vibration, thermal distribution and thermal stress. In this paper, the temperature distribution of 50 kVA pole mold transformer for power distribution are investigated by FEM program and the temperature rise test of designed mold transformer carried out and test result is analyzed compare to simulation data. In this result, the designed mold transformer is satisfied to limit value of temperature and the other property is good such as voltage ratio, winding resistance, no-load loss, load loss, impedance voltage and percent regulation.