• Journal of the Korean Society for Precision Engineering
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• v.17 no.2
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• pp.137-143
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• 2000

An automobile clutch diaphragm spring is operating in a closed clutch housing under high temperature and subject to high stress concentration in driving condition, which frequently causes cracks and fracture. The material of spring is required to possess sufficient fatigue strength and tenacity, which depend largely on the condition of tempering heat treatment. In this paper, specimens are made under a number of different tempering temperatures md tested to find the optimal tempering heat treatment condition. The experiments include the verification of microscopic structure, hardness, tensile strength, fatigue crack growth rate, stress intensity factor range and residual stress. Also, decarbonization, which occurs in actual heat treatment process, is measured and allowable decarbonization depth is studied by durability test.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.217-222
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• 1994

Generally speaking, grouting on the base stabilizes the ground as the aspects of mechanic and engineering properties, with drilling hole at any depth of the earth, and pressuring the cement milk or special chemical grouting material in it. The purpose of grouting on the base is waterproofness and solidification of the ground by earth concreting that the cement milk pass through paticles of soil or crack of rock. This report shows the fundamental properties of microcement compared with those of ordinary portland cement in a point of grouting. It also describes that experimental applications on the treatment of the weathered rock at the constructior of Taegu subway and Boryong earth filled dam site, south of chungchung province, resulted in success.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1772-1777
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• 2007

This paper provides plastic limit loads of pipes with constant-depth, circumferential part-through surface cracks under combined pressure and bending. A key issue is to postulate discontinuous hoop stress distributions in the net-section. Validity of the proposed limit load solutions is checked against the results from three-dimensional (3-D) finite element (FE) limit analyses using elastic-perfectly plastic material behavior.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1830-1835
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• 2007

In the present work, the effect of strength mismatch on plastic limit loads is quantified for strength-mismatched plates with constant-depth surface cracks under tension, via three-dimensional, small strain elastic-perfectly plastic finite element analyses. Relevant variables related to plate and crack geometries are systematically varied, in addition to the weld width. An important finding is that a parameter related to the weld width-to-ligament ratio is proposed, based on which limit loads can be uniquely quantified. The proposed limit load solutions is a valuable input to estimate nonlinear fracture mechanics parameters based on the reference stress approach.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.14-18
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• 1995

Although structural ceramics have excellent mectanical properties, it is very difficult to grind with high efficiency and high quality because of their high strength, hardness, and brittleness. Unfortunately machined ceramics often contain surface damages such as micro fracture and crack on account of brittle fracture. Therefore, is is important to minimize the brittle fracture. The present paper examines grinding characteristics of representative structural ceramics,such as Al /sab 2/O /sab 3/, SiC, Si /sab 3/ N /sab 4/. Effects of grinding variables including table speed and depth of cut on the grinding performance were investigated. Experimental results show that the surface quality is related to the specific grindings energy. The higher specific energy results in the better surface quality.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.10 no.1
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• pp.56-63
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• 2014

In this research, burst tests for axial notched steam generator tubes were conducted. To measure the burst pressure of notched tubes, a burst testing system was manufactured. The tests were conducted under internal pressure at room temperature. Part-through-wall and through-wall notches which have various geometries with different depths and lengths were machined by electro-discharged-machined(EDM) method. The burst pressure decreased exponentially with increasing notch length and decreased almost linearly with increasing notch depth. A comparison of the burst pressure with existing burst pressure solutions for cracked tube show that the existing solution agree well with the test results.

• Structural Engineering and Mechanics
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• v.34 no.4
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• pp.475-490
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• 2010

It is the intention of this study to synthesize the effects of double-edge cracks on the dynamic characteristics of a beam. The stiffness matrix is first determined for a Timoshenko beam containing two same-line edge cracks. The presented model is then developed for elements with two parallel double-sided cracks, considering the interaction between the stress fields of adjacent cracks. Finally, a finite element code is implemented, to examine the influence of depth and location of double cracks, on the natural frequencies of the damaged system.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.665-670
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• 1999

The shear behavior and strength of simply supported reinforced concrete deep beams with web opening subject to concentrated loads have been investigated experimentally on the effects of structural parameters such as location of web opening and reinforcements. A total of 12 specimens were tested at the laboratory under two-point top loading. The shear span-to-depth ratio was taken constantly 0.8, and various types of reinforcements based on truss models were adopted. In the tests, the effects of location, reinforcements of web openings on the shear behavior, and crack initiation and propagation have been carefully checked and analyzed. The test results have been compared with the formulas proposed currently being used and analyzed by nonlinear finite element method. Shear strengths obtained from the tests showed good matches with Kong and Ray's equation, and also with the results calculated by nonlinear finite element method.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.263-266
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• 2005

Recently, many researches for high-strength and high-durability concrete structure have remarkably been studied by adopting new construction material, fiber reinforced polymer (FRP). In connection with these research trend, the shearing capacity of concrete beams reinforced by GFRP stirrup which is developed in this study was evaluated. Experimental variables are span to depth ratio and spacing of shear reinforcement for test. In the result of test, the crack pattern, failure mode and shear load between shear steel reinforcement specimen and GFRP stirrup reinforcement specimen showed similar structural tendency. Therefore, it was investigated that the adaptability of shear-reinforced concrete structure with GFRP stirrup will be improved with further researches of shear design variables.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.303-308
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• 2000

During the past few decades, several composite steel-concrete structural systems have been used and the demand of SRC (Steel Reinforced Concrete) structure increases on the construction of coping structures. But drying shrinking of concrete which is not uniform and the additional restraining effects of encased steel in concrete may cause the crack which leads to harmful damage to structure. In this study, specimens were made to show the restraining effects of embeded-steel in concrete and the differential drying shrinkage strains at various position of concrete were measured and analysed by Compensation Line Method. The results showed that there were remarkable difference in the drying shrinkage according to 속 depth of the concrete, and the tensile stress of the concrete near to encased steel showed the significant amount of stress contrary to 속 specimen which has no embeded-steel.