• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1914-1917
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• 2005

Recently, the reliability evaluation and analysis are applied for many industrial products, and many products are required to guarantee in quality and in efficiency. The purpose of this paper is to present some of reliability evaluation methodologies that are applicable to machine tools. Especially ATC(Automatic Too Changer), which is core component of line center, was chosen as the target of the reliability evaluation and analysis. The scope of research is reliability prediction, reliability test and evaluates their results. The results of this research has shown the failure rate, MTBF(Mean Time Between Failure), reliability for those components and real tests reliability through constructed reliability test-bed. It is expected that proposed methodologies will increase reliability for high speed line center.

• Journal of Korean Institute of Industrial Engineers
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• v.38 no.1
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• pp.7-16
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• 2012

Manufacturing system design poses many challenges for new factory construction. Factories producing the same product may nevertheless have different layouts. The machining line of the engine shop in an automotive factory is a typical flow line, but the layout concept of the line varies among factories. In this paper, a simulation study on the design concept of the manufacturing system for automotive engines is discussed. For comparison, three types of real engine block lines in different factories are analyzed, and three structures of parallel lines are extracted. The effects of failure distribution on the performance measures of three types of parallel line structures are investigated, and some insights are offered regarding the layout concept.

• Magazine of the Korean Society of Agricultural Engineers
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• v.35 no.3
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• pp.47-62
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• 1993

The laboratorv model test was carried out to investigate the behavior of pore water pressure, the critical amount of rainfall for slope failure, the pattern of failure, and the variation of seepage line at the slope with the uniform material of embankment by changing the slope angles and rainfall intensities. The results were was summarised as follows : 1.At the beginning stage of rainfall, the negative pore pressure appeared at the surface of slope and the positive pore pressure at the deep parts. But, the negative one turned into the positive one as the rainfall continued and this rapidly increased about 50 to 100 minutes before the slope failure. 2.The heavier the rainfall intensity, the shorter the time, and the milder the slope, the longer the time took to reach the failure of slope. 3.As the angle of the slope became milder, the critical amount of rainfall for slope failure became greater. 4.Maximum pore water pressure was 10 to 40g/cm$^2$ at the toe of slope and 50 to 90g/cm$^2$at the deep parts. 5.In the respect of the pattern of slope failure, surface failure of slope occurred locally at the toe of slope at the A-soil and failure of slope by surface flow occurred gradually at the top part of slope at the B-soil. 6.As the rainfall continued and the saturation zone in the embankment was formed, the seepage line went rapidly up and also the time to reach the total collapse of slope took longer at the B-soil. 7.As the position of the seepage line went up and the strength parameter accordingly down, the safety factor was 2.108 at the A-soil and 2.150 at the B-soil when the slope occured toe failure. Minimum safety factor was rapidly down to 0.831 at the A-soil and to 0.936 at the B-soil when the slope collapsed totally at the top part of slope.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.113-118
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• 1993

A method for approximating the failure surfaces for columns in compression and biaxial bending was proposed by using the moments along the line of a diagonal of the section. This method showed the better approximations for the failure surfaces of columns than the method of ACI. To calculate the moments along the line of a diagonal of the section, an approximate method which is not influenced by the number of steel s and the location of inner steels was proposed This method gave satisfactory approximations for practical sections of columns.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.677-682
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• 1998

Concrete is an inhomogeneous material consisting of larger aggregates and sand embedded in a cement paste matrix. In this study, an acoustic emission technique has been used to clarify the microscope failure mechanisms of concrete under three point bending test. AE source location has also been done to monitor the activities of internal damage and the progress of microscopic failure path during the loading. The relationship between AE characteristic and microscopic and microscopic failure mechanism is discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.2022-2032
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• 1999

In recent years, the subject of remaining life assessment has drawn considerable attention in the power generation industry. In power generation systems a variety of structural components, such as steam pipes, turbine rotors, and superheater headers, typically operate at high temperatures and high pressures. Thus a life prediction methodology accounting for fracture and rupture is increasingly needed for these components. For accurate failure assessment, in addition to the single parameter such as K or J-integral used in traditional fracture mechanics, the second parameter like T-stress describing the constraint is needed. The most critical defects in such structures are generally found in the form of semi-elliptical surface cracks in the welded piping-joints. In this work, selecting the structures of surface-cracked plate and straight pipe, we first perform line-spring finite element modeling, and accompanying elastic-plastic finite element analyses. We then present a framework for including constraint effects (T-stress effects) in the R6 failure assessment diagram approach for fracture assessment.

• Geomechanics and Engineering
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• v.30 no.3
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• pp.219-231
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• 2022

Geotechnical materials such as silt, fine sand, or coarse granular soils may be unstable under undrained shearing or during rainfall infiltration starting an unsaturated state. Some researches are available describing the instability of coarse granular soils in drained or undrained conditions. However, there is a need to investigate the instability mechanism of unsaturated silty soil considering the effect of degree of compaction and net confining stress under partially and fully drained conditions. The specimens in the current study are compacted at 65%, 75%, & 85% degree of compaction, confined at pressures of 60, 80 & 120 kPa, and tested in partially and fully drained conditions. The tests have been performed in two steps. In Step-I, the specimens were sheared in constant water content conditions (a type of partially drained test) to the maximum shear stress. In Step-II, shearing was carried in constant suction conditions (a type of fully undrained test) by keeping shear stress constant. At the start of Step-II, PWP was increased in steps to decrease matric suction (which was then kept constant) and start water infiltration. The test results showed that soil instability is affected much by variation in the degree of compaction and confining stresses. It is also observed that loose and medium dense soils are vulnerable to pre-failure instability i.e., instability occurs before reaching the failure state, whereas, instability in dense soils instigates together with the failure i.e., failure line (FL) and instability line (IL) are found to be unique.

• Journal of Information Technology Services
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• v.4 no.1
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• pp.1-13
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• 2005

Many buying and selling companies have participated in B2B electronic commerce in order to boost sales and cut down purchase prices respectively. There are some studies on buying and selling companies performances of using B2B e-marketplaces which provide electronic B2B transaction services such as finding transaction partners, providing on-line transaction process like auctioneering, etc. This study investigates the critical failure factors against B2B e-marketplace in other words B2B market-maker or B2B intermediary. We proposed 4 hypotheses asserting that 4 critical failure factors make reverse effects on B2B intermediary performances. We adopt the Balanced Score Card (BSC) framework to evaluate B2B intermediary performance. Data were collected from 46 respondents of B2B intermediaries in Korea. Analyses showed that traditional off-line B2B practices like refunding to buyer or transactions without legal documents and low quality of product information and catalog are critical failure factors against B2B intermediary performance.

• Journal of Welding and Joining
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• v.11 no.1
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• pp.21-32
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• 1993

A cracking failure of a austenitic stainless steel elbow in a naphtha cracking line in a petrochenmical plant occurred, resulting in leakage of organic compound flowing inside the elbow. Due to the failure, emergency shutdown of the plant was enforced to repair the troubled part of the line. The repair cost as well as production loss during the unscheduled plant shutdown has cost the company a great amount of financial loss. In this studies, a failure analysis of the cracked elbow was performed using NDT, chemical analysis, microstructural analysis including optical microscopy as well as scanning electron microscopy with EPMA, mechanical testings such as tensile testing, hardness testing and Charphy impact test fractography. The results indicated that several problems such as a welding defect and presence of a detrimental phase which was found to be relate to improper postforming heat treatment process was identified and the failure was concluded to be due to a low temperature embrittlement of the defect-containing elbows.

• Journal of the Korea Concrete Institute
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• v.11 no.3
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• pp.181-192
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• 1999

The progressive failure following strain localization in concrete can be analyzed effectively using finite element modeling of fracture process zone of concrete with a finite element embedded discontinuity. In this study, a finite element with embedded discontinuous line is utilized for the analysis of progressive failure in concrete. The finite element with embedded discontinuity is a kind of discrete crack element, but the difficulties in discrete crack approach such as remeshing or adding new nodes along with crack growth can be avoided. Using a discontinuous shape function for this element, the displacement discontinuity is embedded within an element and its constitutive equation is modeled from the modeling of fracture process zone. The element stiffness matrix is derived and its dual mapping technique for numerical integration is employed. Then, a finite element analysis program with employed algorithms is developed and failure analysis results using developed finite element program are verified through the comparison with experimental data and other analysis results.