• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.319-324
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• 2004

In this study, the high strength and superior toughness spring steels as the suspension material, used for automobile and railroad industries were utilized to carry out the following investigations. Corrosion times were controlled in 7, 14, 30 and 60days to examine the relation between corrosion pit and compressive residual stress in the static corrosion environment after shot peened. And then corrosion current and corrosion potential were measured for every 24 hours to investigate the corrosion mechanism. Shot peened material shows the low or rate of corrosion current as compared with unpeened material. In case of peened material which has the highest residual stress, it has a low corrosion current density.

• 열처리공학회지
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• 제12권1호
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• pp.40-46
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• 1999

Rotary bending fatigue tests were carried out to investigate the improvement of fatigue limit in annealed and austempered spheroidal graphite cast iron. Main results obtained are as follows. (1) The tensile strength(hardness) of Series C is higher than that of Series B, and fatigue limits are 245MPa in Series C, 230MPa in Series B and 195MPa in Series A, respectively. (2) The fatigue limits of Series B and Series A are mainly governed by the resistance to fatigue crack initiation. Whereas, the fatigue limit of Series C is governed by the resistance to fatigue crack initiation and growth. The defect size and the resistance to crack initiation and growth should be considered to clarify the fatigue properties in spheroidal graphite cast iron. (3) Improvement of fatigue limit by half-austempering is more reasonable than that of full-austempering treatment in multi defective materials as spheroidal graphite cast iron.

• Journal of Welding and Joining
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• 제4권3호
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• pp.43-49
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• 1986

Weldability of the TMCP steel manufactured by controlled rolling followed by accelerated cooling process was investigated. For comparison, two other steel plates produced by different manufacturing processes were selected; normalized and controlled rolled. Tandem submerged arc welding with both side one run technique was carried out. The results of this study can be summarized as follows; TMCP steel having the lowest carbon equivalent shows the best combination of mechanical properties, not only in the base metal but also in the heat affected zone. In the HAZ, the accelerated colling effect imarted on the trengthis releved by the weld thermal cycles, and thus the strength of the welded joint decrease substantially accompanied with the fracture in the HAZ. On the other hand, not only the softening but the fine microstructure can preserve the high toughness of TMCP steel in the HAZ.

• 한국세라믹학회지
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• 제33권4호
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• pp.418-424
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• 1996

(Ti.W)C complex carbide was synthesized by self-propagating high temperature synthesis (SHS) chemical furnace. Attempt to find the optimal condition for synthesis of (Ti.W)C the effects of molar ratio of Ti:W:C on the synthesized powders and mechanical properties were investigated, Optimum molar ratio of these synthe-sized powder was Ti:W:C=0.7:0.2:1.0 The bulk density M,O.R Hardness Fracture toughness of (Ti.W)C complex carbide sintered at 200$0^{\circ}C$ for 60 min by hot-pressing under the pressure of 20 MPa were 7.6g/cm3, 475 MPa, 17,.7 GPa respectively.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 춘계학술대회 논문집
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• pp.156-163
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• 1997

Recently, attempts have been made to be join ceramics to metals in order to make up for the brittleness of ceramics. The difference in the coefficients of linear expansion of the two materials joined at high temperature will cause residual stress, which has a strong influence on the strength of the bonded joints. In this paper, the residual stress distribution and stress intensity factors of the ceramic/metal bonded joints were analyzed by 2-dimensional elastic boundary element method. Fracture toughness tests of ceramic/metal bonded joints with an interface crack were carried out. So the advanced method of quantitative strength evaluation for ceramic/metal bonded joints is to be suggested. Fracture surface and crack propagation path were observed using scanning electron microscope.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.379-382
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• 2004

Abrasive jet machining (AJM) has a large number of parameters such as powder flow rate, air pressure, diameter of abrasive, stand off distance, material hardness and fracture toughness, etc. It is not easy matter to control those parameter. To achieve high accurate machining, in this study, Taguchi method was used to select process parameters. The objective of the optimization was to get higher material removal rate (MRR). From the experiments and analysis, some process parameters were found to make efficient machining.

• 한국안전학회지
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• 제14권3호
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• pp.18-24
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• 1999

This paper were performed to evaluate the elastic-plastic fracture toughness $J_IC$ by the unloading compliance method for 1/2 CT specimen of A5083-H112 aluminum alloy. A modified offset method for negative crack growth effect is presented and compared with Voss offset method. We found that the modified offset method presented can be used efficiently for a determination of the stable crack onset. The $J_IC$ by Voss offset method can be overestimated, but the suggested offset method showed a high reliability within 5% of tolerence from the results by the multi-specimen method.

• International Journal of Precision Engineering and Manufacturing
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• 제4권1호
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• pp.30-36
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• 2003

Brittle materials such as glasses and ceramics, which are very weak under impact loading, show fragile failure mode due to their low fracture toughness and crack sensitivity. When brittle materials are subjected to impact by small spheres, high contact pressure occurs at the impacted surface causing local damage on the specimen. This damage is a dangerous factor in causing the final fracture of structures. In this research, the crack propagation process of soda-lime glass by the impact of small spheres is explained and the effects of several constraint conditions for impact damage were studied by using soda-lime glass; that is, the effects for the materials and sizes of impact ball, thickness of specimen and residual strength were evaluated. Especially, this research has focused on the damage behavior of ring cracks, cone cracks and several other kinds of cracks.

• Tribology and Lubricants
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• 제16권2호
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• pp.84-90
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• 2000

High Temperature wear behavior of plasma sprayed zirconia coatings containing up to 10 mol% of Fe$_2$O$_3$ were investigated. The wear test results showed that the addition of Fe$_2$O$_3$ particles to zirconia improved the wear resistance and lowered the coefficient of friction. Optimum concentration of Fe$_2$O$_3$ was about 5 mol%. Similar degradation behavior was observed at about 40$0^{\circ}C$ for both zirconia and Fe$_2$O$_3$ added zirconia coatings. The results indicated that stabilization of tetragonal phase and changes in mechanical properties such as hardness and toughness were responsible for tribological behavior of plasma sprayed zirconia contain Fe$_2$O$_3$.

• Computers and Concrete
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• 제16권1호
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• pp.1-16
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• 2015

The proposed techniques to strengthen concrete members such as steel plates, polymers or concrete have important deficiencies in adherence and durability. The use of UHPFC plates can overtake effectively these problems. In this paper, the possibility of using UHPFC to strengthen RC beams under torsion is investigated. Four specimens of concrete beams reinforced with longitudinal bars only were tested under pure torsion. One of the beams was considered as the baseline specimen, while the others were strengthened by ultra-high-performance fiber concrete (UHPFC) on two, three, and four sides. Finite element analysis was conducted in tandem with experimental work. Results showed that UHPFC enhances the strength, ductility, and toughness of concrete beams under torsional load, and that finite element analysis is in good agreement with the experimental data.