• Journal of Powder Materials
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• v.24 no.3
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• pp.235-241
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• 2017

Titanium alloys have high specific strength, excellent corrosion and wear resistance, as well as high heat-resistant strength compared to conventional steel materials. As intermetallic compounds based on Ti, TiAl alloys are becoming increasingly popular in the aerospace field because these alloys have low density and high creep properties. In spite of those advantages, the low ductility at room temperature and difficult machining performance of TiAl and $Ti_3Al$ materials has limited their potential applications. Titanium powder can be used in such cases for weight and cost reduction. Herein, pre-forms of Ti-Al-xMn powder alloys are fabricated by compression forming. In this process, Ti powder is added to Al and Mn powders and compressed, and the resulting mixture is subjected to various sintering temperature and holding times. The density of the powder-sintered specimens is measured and evaluated by correlation with phase formation, Mn addition, Kirkendall void, etc. Strong Al-Mn reactions can restrain Kirkendall void formation in Ti-Al-xMn powder alloys and result in increased density of the powder alloys. The effect of Al-Mn reactions and microstructural changes as well as Mn addition on the high-temperature compression properties are also analyzed for the Ti-Al-xMn powder alloys.

• Journal of the Korean Society of Clothing and Textiles
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• v.39 no.1
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• pp.63-76
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• 2015

This study conducted a survey to gauge the buying and wearing propensities of wearers of leg guards made for baseball catchers, as well as product characteristics of preferred leg guards. Data from the survey were analyzed to obtain basic data for the development of an advanced leg guard design. Degree of compression, horizontal distance, cross section view and outline 3D sketch were also analyzed from the 3D data of leg guards; in addition, mobility and kinematic analysis were conducted through a wearing test. The survey indicated that imported products dominate the current retail market because they are appreciated by customers in terms of fit, price, brand, and protection. Representative complaints of products were discomfort, pressure, and the heavy-weight of the leg guards in general attributed to overall structure and 3D shape. When the pressure was lower on the front area of knee, it feels better to wear and the average knee angular velocity during the up and down motion increased, which suggests a better design from a kinematic point of view. The knee is the primary part of the body responsible for any movement of the lower limbs; consequently, the degree of compression and support stability of the leg guards near the knee area are important factors to evaluate the performance of leg guards. The results of our study indicate significant opportunities for improvement in product design and the development of baseball leg guards along with an ergonomic design that considers the mobility of the knee, skin deformations is necessary to improve performance. The process followed in this study will be applicable to studies on other personal protective equipment for sports.

• Transactions of Materials Processing
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• v.21 no.1
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• pp.13-18
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• 2012

During warm forging, materials are formed in the temperature range of $300^{\circ}C\sim900^{\circ}C$. In this temperature range, the friction between the forging die and the material is very high and has a negative effect on the forming process causing severe die wear and possible defects in the component because of stick-slip. Thus, lubrication characteristics are a very important factor for productivity during warm forging. In this paper, ring compression experiments were conducted to estimate the friction factor between the die and the materials as the main factor in characterizing the lubricant. Also, ring tests using normal graphite power as a lubricant coating system were compared with tests using nano graphite powder. The results confirm that the nano graphite is superior to the normal graphite in view of its lubricating effect. In addition, the friction factor (m) was estimated with respect to the amount of the nano graphite content in the lubricant. With 10 % nano graphite the friction factor had the lowest value as compared to other amounts. It can be concluded that the amount of the nano graphite in the coating system can be optimized to obtain the best lubrication condition between the die and the material using ring test experiments.

• Fashion & Textile Research Journal
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• v.23 no.5
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• pp.624-633
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• 2021

This study was intended to compare the comfort of wearing each type of commercially available bralette. The trial wearing experiment was conducted on five women in their 20s who wear an average Korean bra size of 70A. The experimental bralettes were of four types: a bralette with both hooks and pads and a bralette without both, a bralette with hooks but no pads, and a bralette with pads but no hooks. The wearing test results are as follows. First, in terms of functional satisfaction, the padded bralette provided the greatest satisfaction in supporting the chest from the bottom up and bringing it to the center, and the bralette without the pad provided the least satisfaction. In addition, the level of convenience of attaching/detaching was about twice as high in the bralette with hooks than those without hooks. Chest compression was found to be greater in bralettes without hooks than in those with hooks. In terms of the pressure on the shoulder strap and on the lower chest band, it was found that bralettes with hooks had a greater sense of pressure than those without. In the appearance characteristics test, the unpadded bralettes scored higher than the padded one in the matter of feeling embarrassed, because in unpadded bralettes, the nipples were exposed underneath the clothes . This study is meaningful in classifying the design of the bralette and evaluating the fit for each design in the absence of prior research on the bralette.

• Fashion & Textile Research Journal
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• v.21 no.4
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• pp.488-496
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• 2019

This study investigated if the proper pressure level on the wrist tendon area and muscle area of the lower arm are within the same range by examining the responses of blood flow and subjective evaluation. Subjects consisted of 18 males in their 20s, and the experimental bands were custom-made by applying size measurements of each subject. In the experiment, a total of 5 steps were selected by reducing 10 (Step 1) to 50 (Step 5)% from the original body size in the circumferential direction. Blood flow was measured with a sensor attached to the tip of the finger inside the right hand while sitting in a chair for 15 minutes. Blood velocity began to increase (0.82 kPa) when the wrist circumference around tendon area was reduced by 20% (Step 2) and reached its maximum (1.72 kPa) at Step 4. However, the preferred subjective pressure was 1.36 kPa, which was less than the maximum pressure value of 1.72 kPa for Step 4. Blood velocity began to increase when pressure on the muscle area was 1.38 kPa and reached its maximum at 2.16 kPa; however, the most preferred clothing pressure was 1.71 kPa. The results of this study showed that the appropriate pressure level was higher in the muscle area than in the wrist tendon of the lower arm and indicated that graduated compression is favorable.

• Journal of the Korea Fashion and Costume Design Association
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• v.23 no.3
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• pp.1-10
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• 2021

Harnesses are used in a variety of industries, such as rescue operations, medicine, and entertainment. However, conventional harnesses have problems as they are uncomfortable to wear and causes continuous pain. Therefore, in this study, the load and pressure applied to the body in the flying state when using a conventional harness were measured in real time and the distribution change was observed. Load and pressure were measured using a modified corset harness, a pressure sensor, and a human mannequin to measure the maximum and average pressure on the waist. As a result, it was confirmed that the load concentrated on the waist in the flying state was 104 N, and the pressure was applied to the left and right sides was 800 kPa or greater. The pressure distribution showed a pressure of 3-45 kPa in 73% in all measurable pressures. The results of the load and pressure distribution are presented as basic data for improving the wearability and reducing the discomfort of harnesses in the future, aid in the development of a harnesses that can minimize discomfort for various activities, and increase the concentration on experiential activities. In addition, using the CLO 3D program, which is a 3D virtual wearing system, a harness was put on a virtual model, and the compression level was checked and compared with the actual pressure distribution. As a result of comparing the measured pressure values in the flying state with the clothing pressure wearing the harness in the CLO 3D program, the total pressure value was found to be about 68% of the actual measured value. This helps develop a harness that can minimize discomfort during activities by predicting the load and pressure on the body by first applying new designs to a virtual wearing system during development. These new harness patterns can solve the problems of conventional harnesses.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.51-52
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• 2002

We report results on microtribological studies of chemically grafted nanoscale polymer layers of different architecture with thickness below 30 nm. We have fabricated the molecular lubrication coatings from elastomeric tri-block copolymers and tested two different designs of corresponding nanocomposite coatings. We observed a significant reduction of friction forces and an increase of the wear stability when a minute amount of oil was trapped within the grafted polymer layer. These polymer gel layers exhibited a very steady friction response and a small value of the coefficient of friction as compared to the initial polymer coating. A polymer 'triplex' coating has been formed by a multiple grafting technique. The unique design of this layer Includes a hard-soft-hard architecture with a compliant rubber interlayer mediating localized stresses transferred through the topmost hard layer. This architecture provides a non-linear mechanical response under a normal compression stress and allows additional dissipation of mechanical energy via the elastic rubber interlayer.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.966-970
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• 2011

The thermo-mechanical interaction between brake block and wheel tread during braking has been found to cause thermal crack on the wheel tread. Due to thermal expansion of the rim material, the thermal cracks will protrude from the wheel tread and be more exposed to wear during the wheel/block contact than the rest of the tread surface. The wheel rim is in residual compression stress when is new. After service running, the region in the tread has reversed to tension. This condition can lead to the formation and growth of thermal cracks in the rim which can ultimately lead to premature failure of wheel. In the present paper, the thermal cracks of railway wheel, one of severe damages on the wheel tread, were evaluated to understand the safety of railway wheel in running condition. The residual stresses for damaged wheel which are applied to tread brake are investigated. Mainly X-ray diffusion method is used. Under the condition of concurrent loading of continuous rolling contact with rails and cyclic frictional heat from brake blocks, the reduction of residual stress is found to correlate well with the thermal crack initiation.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.7
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• pp.529-534
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• 2016

During the past few years, several incidents of freight car wheel failure during operation have occurred due to fatigue crack and overheating from braking. Tensile residual stress on the wheel tread creates an environment conducive to the formation of thermal cracks that may threaten the safety of train operations. It is important to investigate the residual stress on wheels in order to prevent derailment. In the present paper, the residual stress on wheels is measured using the x-ray diffraction system and the residual stress is analyzed using FEM. The result shows that the residual stress on the wheel rim is lower than that on the wheel tread center and the stress on over-braked wheels changes from compression residual stress to tensile residual stress.

• Korean Journal of Human Ecology
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• v.11 no.1
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• pp.79-93
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• 2002

The purpose of this study was to determine the effect of dynamic characteristics of knitted fabrics on the clothing pressure of foundation. Five knitted fabrics of foundation were selected by different fiber types and blended ratios for the study. The dynamic characteristics of foundation wears made with five different fabrics were measured by KES-FB system method. The results of this study were as follows: 1. The tensile linearity and resilience of f1 were lower than those of other samples. While the tensile resistances of f1, f2 and f4 samples were high, the coefficients of friction of them were low. The bending rigidity and geometric roughness of f5 were higher than the others. 2. The clothing pressure of f3 all-in-one sample was the highest, and followed by f5, f4, f2 and f1, respectively. This result showed that the compression resilience affected on the clothing pressure greatly. 3. In terms of the clothing pressure by posture, the clothing pressure at $90^{\circ}$ bending posture was the highest and followed by that at standing and one-leg-up, respectively. The back part of abdomen was pressured most at $90^{\circ}$ bending posture.