• Journal of Welding and Joining
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• 제20권2호
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• pp.95-101
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• 2002

After high power lasers are avaliable in the commercial market, the number of applications of the laser welding has been increased in manufacturing industries. Although the tailored blank laser welding of butt jointed steel sheets is well known recently in the automotive industries, the lap joint laser welding is a new technology to the automotive manufacturing people as well as the design people. But the deep penetration laser welding seems to be preferred to the partial penetration welding for the lap joint welding in the automotive manufacturers because the partial penetration is a serious deflect for the butt joint. In this study, the feasibility of partial penetration welding fur the lap joint $CO_2$ laser welding was studied fur the 1mm thick 390MPa high strength steel sheets for automotive bodies. The process window of the lap joint partial penetration welding was obtained from experiments with the gap size and the welding speed as process parameters. The partial penetration welding was found excellent on the basis of the tensile shear strength and sectional geometry. The bead width, input energy Per volume, tensile-shear strength, deformation energy and the sectional geometries after tensile-shear tests of partial penetration welded specimens are compared with those of full penetration welded specimens with a series of gaps and welding speeds.

• 한국도로학회논문집
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• 제19권5호
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• pp.33-42
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• 2017

PURPOSES : The purpose of this study is to suggest the construction and quality control method for the re-repair of a deteriorated partial depth repair for sections of Portland cement concrete pavement. METHODS : An experimental construction was conducted to extend the repair width for removing an existing repair section. A removal method was used to ensure early performance for a deteriorated partial depth repair section. Bond strength and split tensile strength were measured at the near vertical interface layer between the existing pavement and repair material. The area was analyzed for various conditions such as the extended repair area and the removing method of the existing repair section. RESULTS : As a result of analysis of bond strength and split tensile strength, the bonding performance of a milling removed section was improved over a cutting and hand breaker removed section. The bond strength was analyzed to increase slightly as the extended repair width for removing the existing repair section increased. The split tensile strength did not show a clear relationship to an increased extended repair width of an existing removed repair section. CONCLUSIONS : The milling removal method should be applied in the removal of existing deteriorated partial depth repair sections. The extended repair width for a re-repair section should be wider than the existing partial depth repair with at least a 75-mm length and width for the bond strength and the split tensile strength.

• 한국강구조학회 논문집
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• 제12권3호통권46호
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• pp.231-238
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• 2000

본 연구는 용접지단부의 후처리 결과, 상대적으로 피로강도가 낮아진 용접루트부에 초점을 맞추었다. 용접루트부의 피로강도를 향상시키기 위하여 부분용입용접을 실시한 십자 리브 시험체와 보통의 필렛용접이음 십자 리브 시험체를 대상으로 피로시험을 행하였다. 그 결과, 부분용입용접을 한 시험체이더라도 용접그대로인 시험체의 경우는 보통의 필렛용접이음과 거의 동등한 피로강도를 보였다. 이것은 피로파괴가 지단부로부터 시작되었기 때문에 용접루트부의 보강책인 부분용입용접의 효과가 나타나지 않았다고 생각된다. 이에, 지단부의 피로파괴를 막기 위해 지단부를 후처리시킨 부분용입용접이음 시험체를 대상으로 피로시험을 한 결과, 보통의 필렛용접이음보다 상당한 피로강도 향상을 보였다. 그러므로 본 연구는 지단부로부터 피로균열 발생을 억제한다면, 부분용입용접이음으로 루트부의 피로강도를 향상시켜, 결국 전체적인 파단수명을 향상시킬 수 있을 것으로 생각한다.

• Journal of the Korean Wood Science and Technology
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• 제41권2호
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• pp.100-104
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• 2013

Bearing occurs by the rotations of members induced from horizontal or vertical load at traditional wooden joint in frame. The bearing between wooden members is not occurring at the whole surface of joint, but occurring only at the particular bearing area. In this study, partial bearing according to the different grain direction was evaluated. The partial compressive strength showed 3 times higher than pure compressive strength perpendicular to grain, 1.5 times higher than parallel to grain and 3.3 times higher than both of them. It is expected that this result can be very importantly applied when evaluating and analyzing the actual behavior of traditional wooden mortise and tenon joint.

• Computers and Concrete
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• 제26권5호
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• pp.385-395
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• 2020

The influence of combination of nano silica and silica fume, as partial cement replacement materials, on the properties of concrete has been studied through the measurement of compressive strength. The compressive strength of concrete in terms of mean, standard deviation and with-in-test coefficient of variation related to the variation in the nominated parameters have also been developed. The compressive strength data developed experimentally has been analyzed using normal-probability distribution and partial safety factors of composite concretes have been evaluated by using first order second moment approach with Hasofer Lind's method. The use of Nano silica and silica fume in concrete decreases the partial safety factor of concrete i.e., increase the reliability of concrete. The experimental results show that the properties of concrete having nano silica and silica fume in combination were better than that of a plain concrete. The SEM test results showing the level of Ca(OH)₂ in plain concrete and consumption level Ca(OH)₂ of concrete containing nano silica & silica fume have also been presented.

• 소성∙가공
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• 제25권6호
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• pp.396-401
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• 2016

Recently, Multi-strength hot stamping process has been widely used to achieve lightweight and crashworthiness in automotive industry. In concept of multi-strength hot stamping process, process design of tailor rolled blank(TRB) in partial heating is difficult because of thickness and temperature variation of blank. In this study, springback prediction of TRB in partial heating process was performed considering its thickness and temperature variation. In partial heating process, TRB was heated up to $900^{\circ}C$ for thicker side and below $Ac_3$ transformation temperature for thinner side, respectively. Johnson-Mehl-Avrami-Kolmogorov(JMAK) equation was applied to calculate austenite fraction according to heating temperature. Calculated austenite fraction was applied to FE-simulation for the prediction of springback. Experiment for partial heating process of TRB was also performed to verify prediction accuracy of FE-simulation coupled with JMAK equation.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 추계 학술논문 발표대회
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• pp.215-216
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• 2011

This study investigates the effect of partial replacement with cement on the properties of blast furnace slag-based mortar. Recycled fine aggregate with various contents was used to activate the hydration of blast furnace slag in the mortar and compared its effect on strength development. Results showed that increasing cement and recycled fine aggregate increased the strength of mortar specimens. However, this study found that the mortar made with partial replacement of river sand with recycled fine aggregate of 20% developed a similar strength to the strength that cement with 10% can achieved.

• Journal of the Korean Wood Science and Technology
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• 제23권2호
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• pp.37-46
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• 1995

The substitution of carboxymethylated hydroxyl group in pulp revealed more hydrophilic than hydroxyl group. And then fibers were more flexible, swell more which leads to better conformation between fibers in turn this raise paper strength. In this paper, we tried to chemical modifyings of recycled fiber, OCCs(old corrugated containers). Many researchers have examined chemical modification of papermaking fiber by partial carboxymethylation(PCM) using a organic solvent processes. We made modified PCM processes adapted waters m replace of the organic solvent. Our testings for the optimum conditions on the new method, conditions as reaction time, temperature, liquor ratios were designed likely plant system. Freenesses(SR$^{\circ}$) were increased following on carboxyl content of the samples. Handsheets of untreated samples and partial carboxymethylated OCCs were made by optimum conditions on different concentrations of the reagent. As results, maximum 25% strength increasing effects were obtained by the new method.

• 한국세라믹학회지
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• 제21권1호
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• pp.51-59
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• 1984

In this paper mechanical properties of reaction-bonded silicon nitride are studied with the variation of initial nitrogen partial pressure. At 1, 25$0^{\circ}C$ the amount of nitridation and the nucleation of nitride increase linearly with the nitrogen partial pressure increase. After the nitridation is completed the density of nitride and modulus of rupture at room temperature are increased with the amount of nitridation. When the partial pressure of nitrogen is 0.5 atm the specimen show the optimum properties that is the highest density of nitride and modulus of rupture. Also the microstructure of $\alpha$-matte is deveoped very well at that pressure of nitrogen which contributes to the strength development of specimen. It is shown that with proper control of initial partial pressure of nitrogen high strength silicon nitride body can be manufactured for dynamic applications.

• 콘크리트학회논문집
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• 제17권1호
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• pp.149-155
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• 2005

The purpose of this study is to investigate the flexural strengthening effects of CF(Carbon Fiber) sheet for the full-scale RC beams with multi-layer CF sheets. The partial strength reduction factors of CF sheets are suggested from the full-scale RC beams tests strengthened with multi-layer CF sheets up to six layers as well as material tests. From the material tensile tests, it was observed that the average tensile strengths of CF sheets per layer are decreased as the number of CF sheets is increased. Also the steep strength reductions of CF sheets in material test results at rupture are observed compared with the structural tests results for the full-scale RC beams strengthened with multi-layer CF sheets. Finally, the partial strength reduction factors far CF sheets up to six layers are suggested considering the effects of multi-layer and unit weight of CF sheets.