• Journal of the Korean Society of Clothing and Textiles
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• v.36 no.4
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• pp.371-381
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• 2012

This study investigates quantitative wear training effects and involved 15 participants from a previous study (part 1) in May to September 2009. Before wear training, the subjects' rectal temperature, skin temperature, heart rate, blood pressure and local sweating were measured for 1 hour in a climate chamber ($39{\pm}1^{\circ}C$, $65{\pm}5%RH$, 0.3m/s) to evaluate heat tolerance. Subsequently, the subjects were divided into 3 groups that consisted of 5 participants. Group N (control-group) dressed the participants so that they felt comfortable (or cool). Group W and MW where participants underwent regular wear training for 10 weeks (5 days a week a total of 50 times). The intensity of the wear training for the participants of group MW was stronger than that for group W. A heat-tolerance experiment was performed after wear training. The results were as follows: 1. The participants of groups W and MW felt more comfortable after wear training than before wear training in the case of warmer $T_{cl}$. However, no significant differences were observed before and after wear training for group N. 2. The heat tolerance of the participants of groups W and MW was higher after wear training than before wear training. However, no significant difference was noted in this regard for group N. 3. The results showed the wear training effect (based on quantitative guidelines). The results show that the predicted optimal temperature inside clothing can enhance heat tolerance.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.5
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• pp.40-47
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• 2003

This study examined the improved effect of wear tolerance of warm-season turfgrass overseeded with cool-season turfgrasses. Also, it investigated the improved effect of crumb rubber on wear tolerance and the difference anmong cultivars regarding the wear of Zoysia spp. In wear experiment during summer, the warm-season turfgrass overseed with cool-season turfgrasses had a higher visual rating on the ground than the monostand of Cynodon dactylon. Moreover, in wear experiment in winter, barrenness showed significant progress in the monostand of C. dactylon, while the barrenness did not appear at all in overseeded turf with cool-season turfgrasses. As a result of investigating the bulk density was increased in the monostand of C. dactylon, but not in the overseed turf with cool-season turfgrasses. From the above result, the wear tolerance effcect of turfgrasses appeared year round through warm-season and cool-season turfgrass mixtures. Also, it was found that the method of topdressing crumb rubber on the ground was effective as a physical assistant device alleviating damage of turfgrasses. The possibility of improving wear tolerance was accepted by adding soil amendments such as perlite, pamis, etc., in order to promote the growth of turfgrass.

• Journal of the Korean Society of Clothing and Textiles
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• v.19 no.3
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• pp.504-515
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• 1995

This study was performed to investigate that wear training using thermal insulation with clothes has the effect on the human thermoregulatory response, especially on the heat tolerance. Twelve men and women in twenties wert divided into the control group, the training groups and each group except the control group had participated in wear training. The heat tolerance was assessed in all subjects who had participated in the experiment carried out in hot environment(40$\pm$1$^{\circ}C$, 50$\pm$5%RH) by such parameters as rectal temperature, skin temperature, systolic blood pressure, diastolic blond pressure, plume rate, total sweat volume, local sweat volume, subjective sensation, and the differences of heat tolerance in each group were compared. The results were as follows: In hot environment(4$0^{\circ}C$) the changing width of rectal temperature was decreased in the control and the heavy clothing group. Forehead and abdomen temperature in hot environment were significantly decreased after the training. Sweat rate was higher after the training than before. In all experimental groups, systolic and diastolic blood pries.;uses in hot environment(4$0^{\circ}C$) were significantly decreased after the training.

• Weed & Turfgrass Science
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• v.5 no.2
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• pp.88-94
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• 2016

Vehicular traffic on turf results in loss of green cover due to direct tearing of shoots and indirect long-term soil compaction. Protection of turfgrass crowns from wear could increase the ability of turf to recover from heavy traffic. Plastic turfpavers have been installed in trafficked areas to reduce soil compaction and to protect turfgrass crowns from wear. The objectives of this study were to evaluate traffic performance of turfgrasses (Zoysia matrella and Axonopus compressus) and soil mixture (high, medium and low sand mix) combinations on turf-paver complex. The traffic performance of turf and recovery was evaluated based on percent green cover determined by digital image analysis and spectral reflectance responses by NDVI-meter. Bulk density cores indicated significant increase in soil compaction from medium and low sand mixtures compared to high sand mixture. Higher reduction of percent green cover was observed from A. compressus (30-40%) than Z. matrella (10-20%) across soil mixtures. Both turf species displayed higher wear tolerance when established on higher sand (>50% sand) than low sand mixture. Positive turf recovery was also supported by complementary spectral responses. Establishment of Zoysia matrella turf on turfpaver complex using high sand mixture will result in improved wear tolerance.

• Journal of the Korean Society of Clothing and Textiles
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• v.36 no.3
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• pp.259-268
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• 2012

This study suggests quantitative guidelines for inside clothing temperatures to improve the heat tolerance of 20's females in summer. First, the inside clothing temperatures ($T_{cl}$) of each subject was measured in daily use. The subjects were asked to record subjective thermal sensations, clothing items worn, clothing weight, and activities during an experiment designed to determine the comfort zone of $T_{cl}$. In a thermally neutral state, the comfort zone of $T_{cl}$ was decided on a mean value $T_{cl}{\pm}1{\sigma}$. Second, the subjects were asked to wear clothing that would enable them to feel 'slightly warm but still comfortable'. The rest of the processes were the same as previous steps that were designed to understand the way and degree of clothing control. The comfort zone of $T_{cl}$ was decided in the same manner as the previous step. The two comfort zones were combined and named the combined comfort zone of the definitive comfort zone. The results were as follows: 1. Thermally comfortable $T_{cl}$, Hcl were $34.0{\pm}1.1^{\circ}C$, $40{\pm}9%%RH$ and the thermally comfortable ambient climate was $25.0{\pm}1.6^{\circ}C$, $53{\pm}7%$RH. 2. When subjects were asked to wear 'slightly warm but still comfortable', there were difference in thermally comfortable $T_{cl}$, clothing weight and clothing layer by subject. 3. In this study, the optimal $T_{cl}$ was decided on the mid-point of the definitive comfort zone of $T_{cl}$.

• Asian Journal of Turfgrass Science
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• v.26 no.2
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• pp.116-122
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• 2012

The study was conducted to know whether turfgrass wear tolerance, growth, and quality could be improved by the application of silicon and potassium. First, turf responses to silicate and potassium were evaluated by several parameters such as, turf visual quality, root length, shoot density, and dry weight under the field condition. Second, turf responses to traffic frequencies were examined by turf growth (root) length, shoot density and dry weight) and soil hardness under the field condition. Finally, under traffic stress condition, the effects of silica and potassium application on wear tolerance were evaluated through the methods described above. Creeping bentgrass (Agrostis stolonifera) rooting were significantly improved by silica. The root length was enhanced by an increase in potassium silicate application. Certain level of light traffic is beneficial while frequent traffic cause serious adverse effect on visual quality of bentgrass. Under a traffic stress condition with 10 times of footing a day for 30 days, silica and potassium increased turf visual quality by 6.38% and 10.25% respectively when compared to the control. Silica and potassium treatment on trafficked plot increased turf visual quality by 11.4% and 10.2% respectively in comparison with the control with significant reduction of wear injury from the traffic. A co-application of potassium silicate with potassium sulfate provided the enhanced visual quality of turf as compared to application of silica or potassium fertilizer, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.9
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• pp.1736-1745
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• 2002

The objective of this study is to predict the roll wear in hot rod rolling process. In this study hot rod rolling process for round and oval passes has been investigated. In order to predict the roll wear, the wear model is reformulated as an incremental form and then wear depth of roll is calculated at each deformation step on contact area using the results of finite element analysis, such as relative sliding velocity and normal pressure at contact area. Archard's wear model was applied to predict the roll wear. To know the thermal softening of DCI (Ductile Cast Iron) roll according to operating conditions, high temperature micro hardness test is executed and a new wear model has been proposed by considering the thermal softening of DCI roll expressed in terms of the main tempering parameter curve. 3D wear program developed in this study might be used for adjusting the gap of rolls to set up a suitable rolling schedule for keeping dimensional tolerance of the product.

• Tribology and Lubricants
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• v.25 no.4
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• pp.256-260
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• 2009

Fretting is a kind of wear which effects on reliability and durability. When machine parts are joined joint in parts such as a bolt or a rivet or a pin, fretting phenomenon is occurred by micro relative movement. When fretting occurs in joint parts, there is wear which is the cause of fatigue crack. Recently, although the ways of assessment of fatigue and damage tolerance are established, there is no way to evaluate fatigue crack initiation life by fretting phenomenon. Consequently, the prediction of life and prevention plan caused by fretting are needed to improve reliability. The objective of this paper is to predict fretting wear by using a experimental method and contact analysis considering wear process. For prediction of fretting wear volume, systematic and controlled experiments with a disc-plate contact under gross slip fretting conditions were carried out. A modified Archard equation is used to calculate wear depths from the contact pressure and stroke using wear coefficients obtained from the disc-plate fretting tests.

• Journal of Korean Institute of Industrial Engineers
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• v.39 no.3
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• pp.149-155
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• 2013

Electric discharging machining (EDM) is commonly adopted to machine the precise and tiny part when it is difficult to meet the productivity and the tolerance by the conventional cutting method. The die-sinking EDM method works well to machine the micro-parts and the perpendicular wall of die and mould, whereas EDM drilling, called super drill, is excellent to machine the deep and narrow hole regardless the material hardness and the hole location. However, the electrode wear is rapid compared to the conventional cutting tool and makes it difficult to control the electrode feeding and to machine precisely. This paper presents an efficient method to estimate the electrode wear using hole pass-through experiment while the stochastic method is used to compensate for the estimation model. To validate the proposed method, the commercial EDM drill machine is used. The experiment result shows that the electrode wear amount can be predicted very precisely.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.11
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• pp.47-54
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• 1999

Tool wear is one of major causes occurring defectives in NC machining. In this paper we developed an automatic tool compensation system for the NC lathe machining. The system compensates machining error without any help of operators whenever the specification of a part is out of a tolerance. The configuration of the automatic compensation system consists of a NC lathe, an autoloader, a sensor, and a PLC. The system is operated as follows. A workpiece loaded by the autoloader is machining on the NC lathe. Once the workpiece is machined to be turned to a part, it is moved onto the sensor to be measured. If the sensor detects a part out of tolerance, a tool compensation is made in the NC controller. The system gives a help in increasing the productivity by reducing occurrence of defective parts as well as by eliminating time for the tool compensation. Besides the productivity increase, the system calculates cumulative usage time of the tool and notices the tool replace time to a worker by an alarm signal. A case is introduced to show that the system can be applied effectively in a shop.