• Journal of Welding and Joining
• /
• 제33권4호
• /
• pp.50-56
• /
• 2015

In general, discontinuity of metallurgical and structural points of weld zone could decline the fatigue strength. For the lightweight trend, the AHSS application in automotive chassis is in-progress. However, there are few research reports on AHSS welds fatigue strength in especially automotive chassis parts. Therefore, in this study, we evaluated the effects of the factors affecting the AHSS welding fatigue strength. As the result, the stress concentration of weld bead is the most important factor for welding fatigue strength. For the enhancement of welding fatigue strength, we focused on reducing the stress concentration of the welding beads. So, we applied and proved the plasma welding process and GTAW (Gas Tungsten Arc Welding) dressing method. It was verified by uniaxial fatigue specimen, fatigue performance increased from 40 to 60% by applying TIG dressing method compared to the conventional GMAW (Gas Metal Arc Welding). These results could be recommended the enhancement of fatigue performance of AHSS.

• 한국기계가공학회지
• /
• 제16권2호
• /
• pp.1-6
• /
• 2017

In this paper, we present a study concerning the design of a 400 N class side thruster for small ships. The side thrusters used in Korea are imported from abroad. The performance and durability of the imported products employed in Korea are not adequate, therefore the side thrusters which will be suitable for Korean domestic needs to be re-designed. The strength calculation of the side thruster was performed by KS standard. Strength calculation and design were made to meet design requirements. Structural analysis and safety factor analysis were carried out to confirm the validity of strength calculations and design. After manufacturing the bevel gear, a back lash test was conducted. We also conducted a no-load test, a rated load, and an overload test for a performance test and a durability test of the design while satisfying the design conditions.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
• /
• pp.598-598
• /
• 2013

The short lifetime of Proton Exchange Membrane Fuel Cell (PEMFC) is the one of the main problems to be solved for commercializing. Especially, the weak adhesion between metal nanoparticles and supports deteriorate the performances of nanocatalysts, therefore, it is considered to be a major failure mechanism. Using force-distance spectroscopy of atomic force microscopy (AFM), we characterized the adhesion between Pt nanoparticles and carbon supports that is crucially related to the durability for membrane fuel cell (MFC) electrode. In our study, force distance curves measured with Pt coated AFM cantilever, mimicking the behavior of corresponding nanoparticles on carbon supports, leads to the adhesion between metal nanoparticles and carbon supports. We found that theadhesion between Pt and HNO3-treated carbon is enhanced by a factor of 4, compared to Pt and bare carbon support, that is consistent with the macroscopic durability test of PEMFC. The higher adhesion between Pt and HNO3-treated carbon can be explained in light of the stronger chemical interaction by C/O functional groups.

• 접착 및 계면
• /
• 제7권4호
• /
• pp.60-64
• /
• 2006

In modern vehicle construction the search for means of weight reduction, improving durability, increasing comfort and raising body stiffness are issues of priority to the design engineer. The intelligent usage of many materials such as high strength steel, light-alloys and plastics enables a significant vehicle weight reduction to be achieved. The classical joining techniques used in the automobile industry need to be newly-evaluated since they often do not present workable solutions for such mixed-material connections, for example aluminium/steel. Calculation/simulation methods have made progress as a key factor for broader and more cost-effective implementation of structural bonding. This will lead to reduction of spotwelds and accelerate the car development. A special focus of the paper is the use of high strength steel grades. It will be shown that adhesive bonding is a key tool for yielding the potential of advanced high strength steel for low gauging without compromising the stiffness. The latest status of adhesive development has been described. Improvements with physical strength and glass temperature as well as of process relevant properties are shown. Also the situation regarding occupational hygiene is treated, showing that by further spotweld point reduction the emission around the working area can be even lowered against the current praxis. High performing lightweight design cannot longer do without high performing crash durable adhesives.

• 한국건축시공학회지
• /
• 제9권1호
• /
• pp.81-87
• /
• 2009

The purpose of this study is to investigate the sulfate attack resistance of concrete using the EAF(electric arc furnace) Slag as fine aggregate. In order to figure out the effects of magnesium sulfate solution on the durability of concrete using the EAF Slag as fine aggregate, the experiments for the immerging test in the 10% magnesium sulfate solution was executed by selecting factors such as aging processes, replacement ratio(0, 10, 20, 30, 50%), and duration of immerging. The specimens were made with various EAF slag replacements for fine aggregates and with W/C ratio fixed 0.45. compressive strength and S.D.F(Sulfate Deterioration Factor), weight change, and SEM(Scanning Electron Microscope) were tested. From the test results, EAF slag aggregate treated with accelerated aging is better than treated with air aging. The compressive strength and resistance to the sulfate attack is slightly improved with an increase in the EAF slag aggregate treated with accelerated aging replacement for aggregate.

• 한국정밀공학회지
• /
• 제26권6호
• /
• pp.114-121
• /
• 2009

Mobile phone is a representative personal communication tool among wireless communication devices. Recently, with the miniaturization and light-weight trend of mobile phone, the vibration motor has been replaced by coin type. The required performances of coin type vibration motor needed by user are long life, higher vibration, and thin thickness. Also the most important factor determines the performance of vibration motor is long-term reliability, which is mainly related to PCB plating technique for commutator. In this study, three types of fault were categorized to analyze the cause for malfunction of vibration motor. And, hardness and surface morphology on plating surface are also investigated to optimize the plating method and plating conditions. As a result, new plating method and conditions were proposed to increase the durability of PCB commutator.

• 한국도로학회논문집
• /
• 제19권5호
• /
• pp.153-162
• /
• 2017

PURPOSES : This study was conducted to analyze the effects arising from extending the duration of nighttime road construction on improving road quality and durability. METHODS : Most previous studies estimating the social cost of various construction conditions did not consider road pavement cooling time as a factor in improving road pavement quality. This study investigated the feasibility of achieving higher road quality and durability by extending the duration of nighttime road construction time extension. For this investigation, the effects of such an extension on traffic conditions were analyzed based on micro-simulation studies and scenario-based cost-benefit analyses, using factors including traffic volume, delay, construction cost, and road pavement cooling time. RESULTS : The results of the traffic simulation studies and cost-benefit analyses indicate that the current road construction method that emphasizes completing nighttime road construction by 6 a.m. reduces pavement life while causing relatively little traffic delay. If the night construction time is instead extended to 2 p.m., road pavement lifetime is increased, reducing road re-construction cost. These savings are greater than the cost of congestion arising from extending the duration of nighttime construction. CONCLUSIONS : The current nighttime construction durations need to be extended in order to efficiently manage roads and reduce road management costs.

• 한국안전학회지
• /
• 제30권6호
• /
• pp.102-109
• /
• 2015

In this study, on the basis of the results of the field survey and the theoretical consideration for Korean Standard Specification for concrete durability and maintenance, the following conclusions are derived. From the survey, the prediction equation of carbonation depth for the southwest region in Korea is experimentally proposed, $y_p=5.865{\sqrt{t}}$, which predicts about 60mm of the carbonation depth for the concrete structures of 100 years, a 1st class of target endurance period, under a combined deterioration environment like a marine environment. Considering that the marginal value for a carbonation depth limitation under very severely marine environment is 25mm, in accordance with the Specification, it is found that the predicting carbonation depth for the concrete cover depths, 100mm and 60mm are 63mm and 29.4mm, respectively. In conclusion, according to the equation and the Specification, it is strongly required that the reinforced concrete structures with the cover depth under 100mm have to make a protection from combined deterioration factors by any methods like a surface coating, an increment of cover depth or an application of a special concrete.

• 한국의류산업학회지
• /
• 제13권4호
• /
• pp.538-547
• /
• 2011

The purpose of this study was to examine the evaluations and attitudes of workers in low temperature storages of discount stores toward their uniforms by carrying out a field study and a survey. The effects of evaluation attributes on their attitudes were also investigated. In this study, the reference of the evaluation of uniforms was based on the concepts of serviceability, which implies the fitness for purpose of products and consists of durability, care, comfort and aesthetic appearance. Of 400 questionnaires, 253 of them were used for data analysis. The data were analyzed by descriptives, t-test, factor analysis, reliability test and regression analysis with SPSS 12.0. As a result, it showed that workers have set low values on easy care, physiological comfort, aesthetic appearance and durability among the evaluation attributes. In attitudes toward the uniforms, emotional attitude was negative whereas behavioral attitude positive. It appeared that the evaluation attributes had influence on the attitude toward the uniforms and esthetic appearance among the attributes had the biggest effects on the workers' attitude. In conclusion, it was found that the discount store uniforms should be improved in the aspects of easy care and physiological comfort, and focused on the esthetic appearance for workers' positive attitudes to their uniforms.

• 보존과학연구
• /
• 통권30호
• /
• pp.125-136
• /
• 2009

Stone cultural heritages in Korea have a severe damages from chemical and biological weathering because most of them have been situated in outdoors without any suitable protection systems, and this in turn causes deformation and structural damage. To counteract these problems and increase durability, various kinds of conservation materials are used in the conservation and restoration treatments. However until now there are not many practical and technological experiments on this subject. This paper attempts quantitative evaluation of effectiveness about chemical of ethylsilicate based resin for sandstone in Yeongyang-gun. It takes a long time to evaluate durability and side effect after conservation materials treatment. So we use artificial weathering through freezing§ thawing experimental method. As a result of this experiment, porosity and absorptance increased, and elastic wave speed, elastic modules, unconfined compression strength and tensile strength decreased more than before. This study plans to make a scientific method study about weathering factor and mechanism, and to deduce correlation between artificial weathering and natural weathering.