• International Journal of Aeronautical and Space Sciences
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• 제15권1호
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• pp.32-43
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• 2014

Automatic fiber placement (AFP) has become a popular processing technique for composites in the aerospace industry, due to its ability to place prepregs or tapes precisely in the exact position when complex parts are being manufactured. This paper presents the design, analysis, and manufacture of an AFP mandrel for composite aircraft fuselage skin fabrication. According to the design requirements, an AFP mandrel was developed and a numerical study was performed through the finite element method. Linear static load analyses were performed considering the mandrel structure self-weight and a 2940 N load from the AFP machine head. Modal analysis was also performed to determine the mandrel's natural frequencies. These analyses confirmed that the proposed mandrel meets the design requirements. A prototype mandrel was then manufactured and used to fabricate a composite fuselage skin. Material load tests were conducted on the AFP fuselage skin curved laminates, equivalent flat AFP, and hand layup laminates. The flat AFP and hand layup laminates showed almost identical strength results in tension and compression. Compared to hand layup, the flat AFP laminate modulus was 5.2% higher in tension and 12.6% lower in compression. The AFP curved laminates had an ultimate compressive strength of 1.6% to 8.7% higher than flat laminates. The FEM simulation predicted strengths were 4% higher in tension and 11% higher in compression than the flat laminate test results.

• 한국해양공학회지
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• 제18권5호
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• pp.43-49
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• 2004

The lightness of components required in the automobile and machine industry necessitates the use of high strength components. In particular, the fatigue failure phenomena, which occurs when using metal, increases the danger to human life and property. Therefore, antifatigue failure technology is an integral part of current industries. Currently, the shot peening is used for removing the defect from the surface of steel, while improving the fatigue strength on surface. Therefore, in this paper, the effect of compressive residual stress of spring steel(JISG SUP-9) by shot-peening on fatigue crack growth characteristics in a stress ratio(R=0.1, R=0.3, R=0.6) was investigated, giving consideration to fracture mechanics. By using the methods mentioned above, following conclusions are drawn: (1) The fatigue crack growth rate(da/dN) of the shot-peening material was lower than that of the un-peening material and in stage I, ΔKth, the threshold stress intensity factor of the shot-peen processed material is high in critical parts, unlike the un-peening material. Also m, fatigue crack growth exponent and number of cycle of the shot-peening material, was higher than that of the un-peening material, as concluded from effect of da/dN. (2) Fatigue life shows more improvement in the shot-peening material than in the un-peening material, and the compressive residual stress of surface on the shot-peen processed operate resistance of fatigue crack propagation.

• Safety and Health at Work
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• 제10권1호
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• pp.114-121
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• 2019

Background: The photolithography process in the semiconductor industry uses various chemicals with little information on their constitution. This study aimed to identify the chemical constituents of photoresist (PR) products and their by-products and to compare these constituents with material safety data sheets (MSDSs) and analytical results. Methods: A total of 51 PRs with 48 MSDSs were collected. Analysis consisted of two parts: First, the constituents of the chemical products were identified and analyzed using MSDS data; second, for verification of the by-products of PR, volatile organic compounds were analyzed. The chemical constituents were categorized according to hazards. Results: Forty-five of 48 products contained trade secrets in amounts ranging from 1 to 65%. A total of 238 ingredients with multiple counting (35 ingredients without multiple counting) were identified in the MSDS data, and 48.7% of ingredients were labeled as trade secrets under the Korea Occupational Safety and Health Act. The concordance rate between the MSDS data and the analytical result was 41.7%. The by-product analysis identified 129 chemicals classified according to Chemical Abstracts Service No., with 17 chemicals that are carcinogenic, mutagenic, and reprotoxic substances. Formaldehyde was found to be released from 12 of 21 products that use novolak resin. Conclusion: We confirmed that several PRs contain carcinogens, and some were not specified in the toxicological information in the MSDS. Hazardous chemicals, including benzene and formaldehyde, are released from PRs products as by-products. Therefore, it is necessary to establish a systematic management system for chemical compounds and the working environment.

• 한국의류산업학회지
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• 제17권4호
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• pp.597-603
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• 2015

This study investigates the actual domestic and overseas cyclewear wearing conditions for male high school cyclists. The study results provide factors and degree of dissatisfaction as basic data for cyclewear development. This study was conducted on 35 male high school cyclists (freshman to seniors) by a questionnaire and interview method. Study results were: Male high school cyclists considered functionality as most important when they bought cyclewear and the brand they most often bought was a cheap domestic brand. Dissatisfaction with the crotch, thigh circumference and minimum leg circumference was higher than other parts during wearing. A cyclist is more sensitive to wear because they require more lower body motion than other parts. Cyclewear should be: less transformed even by frequent laundering, made of breathable material and use a sewing technique that minimizes air resistance and increases fit the body. Functional pads ergonomically designed with high tactile materials should be developed to prevent 'saddle sore' and groin soreness region that happens because of a lower body bending posture when cycling. A follow-up study is recommended to further develop excellence in cyclewear functionality and dimension suitability for male high school cyclists through the size system.

• 한국의류산업학회지
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• 제10권1호
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• pp.68-75
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• 2008

Demands and attempts to express Korean traditional beauty are increasing. Some schools choose the uniform in designs expressing the image of Hanbok, but recently there is a few increment of wearing the uniforms. For the improvement of the uniforms, first of all, the shape and the clothing materials of the uniforms should be considered. We have compared and analyzed the shape and the clothing materials of the uniforms reflecting the image of Hanbok, according to seasons and clothing items. The uniforms reflecting the image of Hanbok were worn in eight schools and all of them are Saenghwal Hanbok style. The shape of Saenghwal Hanbok school uniforms showed both Korean style and western style characteristics. Korean style characteristics were expressed through the appearance-related parts while western style characteristics showed through the performance-related parts such as open/closure method, armhole pattern and straight sleeve line. It was shown that girls' uniforms are more diverse and similar to the western style uniforms than boys' uniforms. It was found that most of the clothing material were synthetic fiber or mixture of natural/synthetic fiber, and polyester was shown to be used most.

• 한국기계가공학회지
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• 제21권1호
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• pp.49-55
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• 2022

Recently, the automobile industry has continued to demand lighter materials owing to international environmental regulations and increased convenience. To address this demand, aluminum parts have increased in popularity and are mainly developed and produced through hot forging and cold pressing. However, because this method has low yield and low production efficiency, a new manufacturing method is desirable. In this study, the water capacity efficiency of an aluminum inner tie rod socket was investigated using cold forging that provided a high yield and excellent production efficiency. Mechanical properties were derived through tensile testing of 6110A aluminum materials, and critical fracture factor and process analysis based on experimental data were carried out. The optimized process was applied as a prototype using cold multi-stage forging, and based on the derived results, the formability, productivity, and material efficiency of aluminum inner tie rod socket parts using this cold forging process was verified.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1992년도 추계학술대회 논문집
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• pp.136-144
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• 1992

Recently, Silicon Nitrde ceramic is regarded as the representative engineering ceramic with the excellent mechanical properties and many functions for mechanical components and parts among various kinds of ceramics in the mechanical industry. But, during the manufacturing of engineering ceramics, there is many volumetric shrinkage coupled with a distortion of the parts which is produced. Due to the requirement for high accuracy of size, form, and surface finish of the components, machining is needed surely. Nowdays, grinding with a resin bond type diamond wheels has been generally applied to machining of the engineering ceramics in the whole world because that it can be conveniently proceeded for workers to dress of tool and made with high reliability in producing factories among many bond type super-abrasive wheels yet. It is important task for attaining prescribed mechanical components with high reliability to observe the grinding mechanism of ceramics as like generation of cracks and chipping of material during process. Because they considerably effects on the strength characteristic of machined mechanical components. In this study, various surface grinding experiments using resin bond type diamond wheels are carried out for Silicon Nitride ceramic. Grinding mechanism of ceramics is observed experimentally and the relationship with various conditions is also attained. Form this experimental study, some useful machining data and information to determine proper machining condition for grinding of Silicon Nitride ceramic is obtained.

• 한국산업융합학회 논문집
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• 제26권3호
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• pp.421-431
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• 2023

Recently, the destructive power of typhoons is continuously increasing due to the influence of global warming. In a situation where the installation of floating wind turbines is increasing around the world, concerns about the huge loss and collapse of floating offshore wind turbines due to strong typhoons are deepening. Regarding to the safe operation of the floating offshore wind turbine, the development of a new type of disconnectable mooring system is required. A new fairlead chain stopper considered in this study is devised to more easily attach or detach the floating offshore wind turbine with mooring lines comparing to other disconnectable mooring apparatuses. In order to investigate the structural safety of the initial design of fairlead chain stopper that can be applied to MW-class floating type offshore wind turbine, scale-down structural models were produced using a 3-D printer and structural tests were performed on the models. For the structural tests of the scale-down models, tensile specimens of acrylonitrile butadiene styrene material that was used in the 3-D printing were prepared, and the material properties were evaluated by performing the tensile tests. The finite element analysis of fairlead chain stopper was performed by applying the material properties obtained from the tensile tests and the same load and boundary conditions as in the scale-down model structural tests. Through the finite element analysis, the structural weak parts on the fairlead chain stopper were reviewed. The structural model tests were performed considering the main load conditions of fairlead chain stopper, and the test results were compared to the finite element analysis. Through the results of this study, it was possible to experimentally verify the structural safety of the initial design of fairlead chain stopper. It is also judged that the study results can be usefully used to improve the structural strength of fairlead chain stopper in a detailed design stage.

• 복식문화연구
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• 제10권2호
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• pp.132-145
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• 2002

This study conducted a questionnaire survey of family restaurant employees in Seoul on their satisfaction and preference in working uniforms, and analysed the result to suggest adequate designs to serve the purposes of uniforms. The result is as follows - First, many pointed out a need to improve generally showing a low satisfaction with varying degrees according to sexes and ages. More women complained about colors, designs, materials and sizes than men did, and young employees in their twenties wanted better designs, colors and sizes in the order while those in their thirties and forties were dissatisfied mostly with materials. The need fur the improvement was focused on function and designs, and as for uniform materials, perspiration absorbency had the highest level of dissatisfaction. Second, about 40% of the respondents said the skirt width, pants length, and sleeve width were trio small or too big, therefore it is vital to improve uniform sizes. Third, the employees on duty felt uncomfortable mostly when they sat, and the neck and armhole parts were the most uncomfortable. The most easily tainted parts were in the order of the collar, front hem, and sleeve seam for upper garments, and the hip, bottom hem, and pleats for lower ones. Therefore it is required to develop functional uniforms considering the body features and momentum. Fourth, the most preferred material was that guaranteed easy movement and good air-permeability, and colors were in the order of white, beige and black for upper garments, and black, beige and blue for lower ones. And plain, natural and stripped patterns were preferred by both men and women. As seen so far, restaurant employees were mostly dissatisfied with the design, movement, and function of their uniforms demanding functional ones made of better and comfortable material. Uniform designs were suggested based on the analysis of the demonstrative rese.

• 한국의류산업학회지
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• 제22권5호
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• pp.628-638
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• 2020

This study develops a cool-touch functional Dancesport top for middle-aged women by using cool-touch materials in areas where surface temperature becomes high after exercise. The post-exercise surface temperature of the developed research product was compared and analyzed. In addition, subjective evaluation of cool-touch as well as appearance and movement evaluations were performed. The results are as follows. In designing the research product, a detachable neckband was made using highly-preferred hydrated polymer crystals. A material with high moisture absorption speed was also used in F1, S1, under arm and B5, while a material with good thermal conductivity was used in other parts of the bodice. Deodorant tape with antibacterial and deodorant effects was incorporated in the armpit for additional comfort. As for wear evaluation of the research product, significant differences were found in 10 areas using a material with high moisture absorption speed to compare and analyze the post-exercise surface temperatures of the clothing. The temperature difference between the compared top and the research product in the neckband area was 9.16℃, demonstrating clear cool-touch function in using cool-touch material. In the subjective evaluation of cool-touch function, the results showed high scores when asked about the efficiency of the detachable neckband and the ease of movement when wearing the product. In the appearance evaluation, significant differences were found in 11 items, including redundant folds, tightfit, fit, and design line. The overall mean score of the movement evaluation was 4.6, indicating excellent function for movement.