• Korean Journal of Materials Research
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• v.13 no.10
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• pp.683-690
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• 2003

The high strength low alloy(HSLA) steels microalloyed with Nb, Ti and V have been widely used as the automobile parts to decrease weight of vehicles. The effects of process conditions are investigated in the aspects of the precipitation behavior and the mechanical properties of HSLA steel microalloyed with Nb and Ti using TEM, SANS and mechanical testing. When Ti was added to a 0.07C-1.7Mn steel which was coiled at $500^{\circ}C$, the specimen revealed the property of higher tensile strength of 853.1 MPa and the stretch-flangeability of 60%. The stretch-flangeability was increased up to 97.8% for coiling temperature above $700^{\circ}C$. The precipitation hardening cannot be achieved in the 0.045C-1.65Mn steel which was the lower density of fine precipitates. However, the 0.07C-1.7Mn steels containing Nb and/or Ti which was coiled at X$/^{\circ}C$ have a high precipitates density of $2${\times}$10^{ 5}$/$\mu$㎥. The high strength of these steels was attributed to the precipitation hardening caused by a large volume froction of (Ti, Nb)C precipitates with a size below 5 nm in ferrite matrix.

• The Research Journal of the Costume Culture
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• v.7 no.5
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• pp.165-176
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• 1999

The purpose of this study was to evaluate the effect of various knitted fabrics of sports socks on their properties of hygiene and stability. Seventeen men\`s sports socks to represent five groups with different fiber content, knit structure, yarn fineness, and finishing were used. Properties of hygiene and stability of socks were determined. The results were as follows ; 1. Evaluation of Water, vapor and heat transport properties in socks with varing fiber content showed that cotton 100% socks had the highest drop absorbency, wickability, water absorbency and water retention. Polypropylene 100% socks had an excellent wickability and moisture permeability. Acrylic blend socks had the highest thermal resistance. 2. The greatest knit stretch and knit growth of socks having lower power were found to be with cotton 100% socks had the lowest stretch. Acrylic blend socks had a excellent stretch but low fabric growth, which could give a good fir sensation during wear. 3. The commerical antimicrobial finished socks showed excellent durability after repeated cycles of laundering. 4. Length and width shrinkages were found in all laundered samples during initial cycles due to rearrangement by mechanical relaxation. Shrinkages showed no further changes and reached equilibriums after 5 cycles. Cotton 100% or cotton blend socks showed lower dimensional stability than other socks during fabric care.

• Korean Journal of Materials Research
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• v.1 no.3
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• pp.115-124
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• 1991

In this study, the relationship between mechanical properties and the effects of second phase in tri-phase steel which was composed of ferrite-martensite-bainite was investigated. In order to obtain different microstructure of ferrite+martensite(DP), ferrite+bainite(F+B), and ferrite+martensite+bainite(TP, different heat treatment has been accomplished. The effects of volume fraction and microstructure of each specimen were studied on tensile property, Charpy impact energy and stretch-flangeability. As the bainite content in triphase steels increased, the tensile strength, and yield strength decreased as well as the reduction of area and strength-uniform elongation increased. However, ferrite-bainite steel had high yield ratio and yield point elongation. The Charpy impact energy of TP and F+B steel was higher than that of DP steel. In addition, the characteristics of hole expanding limit($\lambda$) of TP steel and F+B steel were higher than that of DP steel. These mechanical properties of tri-phase steel have been improved, because bainite could be deformed easily within ferrite matrix. The effect of bainite on ductility in tri-phase steel has been found to be favorable. In this experiment, tri-phase steel contained within 27% bainite volume fraction had good nechanical properties and superior stretch-flangeability.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.6
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• pp.777-787
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• 1985

The study is concerned with the analysis of flanging as a sheet metal working process. In terms of mechanics, the flanging process can be divided into two groups, i.e, shrink flanging and stretch flanging. In this study, the shrink flanging process is analyzed by using the proposed energy criterion and the forming limit is found for the process. The forming limit for stretch flanging is also found by employing the neckind theory. Experiments are carried out for both processes. Approximate forming limits are obtained from the experiments. An approximate method to calculate the punch force is proposed and the computed results are compared with the experimental results. It is shown that there are good agreements in forming limits and punch forces between theory and experiments.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.4
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• pp.413-420
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• 2012

An aluminum foil-laminated sheet is a laminated steel sheet on which aluminum foil is adhesively bonded. It is usually used on the outer panel of home appliances to provide an aluminum feeling and appearance on the surface of the product. The delamination of aluminum foil is one of the main problems during the stretch forming process. The purpose of this study is was to determine the delamination limit of an aluminum foil-laminated sheet in the stretch forming process. The delamination was dependent on the bonding strength between aluminum foil and steel sheet. The fracture behavior of the interface between the aluminum foil and the steel sheet was described by a cohesive zone model. A finite element was conducted with the cohesive zone model to analyze the relationship between the delamination limit and the bonding strength of the interface. The interface bonding strength was evaluated by lap shear and T-peel test. The delamination limit of the aluminum foil-laminated sheet was determined by using the bonding strength of the steel sheet. The delamination limit was also verified by the Erichsen test.

• Journal of Mechanical Science and Technology
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• v.16 no.7
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• pp.902-910
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• 2002

Cast stainless steel may experience embrittlement when it is exposed approximately to 300$\^{C}$ for a long period. In the present investigation, the three classes of the thermally-aged CF8M specimen were prepared using an artificially-accelerated aging method. After the specimens were held for 300, 1800 and 3600hrs. at 430$\^{C}$, respectively, the specimens were quenched in water which is at room temperature. Load versus load line displacement curves and J-R curves were obtained using the unloading compliance method. talc values were obtained using the ASTM E813-87 and ASTM E 813-81 methods. In addition to these methods, talc values were obtained using the SZW (stretch zone width) method described in JSME S 001-1981. The results of the unloading compliance method are J$\_$Q/=543.9kJ/㎡ for virgin materials. The values of J$\_$IC/ for the degraded materials at 300, 1800 and 3600hrs. are obtained 369.25kJ/㎡, 311.02kJ/㎡, 276.7kJ/㎡, respectively. The results obtained by the SZW method are compared with those obtained by the unloading compliance method. Both results are quite similar. Through the elastic-plastic fracture toughness test, it is found that the value of loc is decreased with an increase of the aging time.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2007.11a
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• pp.67-68
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• 2007

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.5
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• pp.393-401
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• 2000

To define the postnatal changes in ANP secretion in response to mechanical stretch and atrial compliance, experiments have been done in perfused nonbeating rabbit atria with different ages: 1-day, 1-, 2-, 3-, 4-, and 8-wk-old. In 1-day-old-rabbits, an increase in intraatrial pressure resulted in an increase in atrial volume, which was higher than that in 1-wk-old rabbits. Increases in atrial volume stimulated the secretion of ANP with concomitant translocation of extracellular fluid (ECF) into the atrial lumen. However, mechanically stimulated ECF translocation was lower in 1-day-old rabbits than that in 1-wk-old rabbits. Therefore, positive relationship between mechanically stimulated ECF translocation and ANP secretion was shifted upward in 1-day-old rabbits, as compared to 1-wk-old rabbits. Changes in atrial volume and ECF translocation were gradually increased with aging and reached the peak value at 4 wk. The stretch-induced ANP secretion in terms of ECF translocation (the interstitial ANP concentration) was also increased with aging and reached the peak value at 4 wk. The interstitial ANP concentration was dependent on the atrial content of ANP. These data suggest that the higher level of atrial ANP secretion is related to the postnatal changes in atrial volume and unidentified factor.

• The Korean Journal of Physiology and Pharmacology
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• v.18 no.6
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• pp.503-508
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• 2014

Spontaneous myometrial contraction (SMC) in pregnant uterus is greatly related with gestational age and growing in frequency and amplitude toward the end of gestation to initiate labor. But, an accurate mechanism has not been elucidated. In human and rat uterus, all TRPCs except TRPC2 are expressed in pregnant myometrium and among them, TRPC4 are predominant throughout gestation, suggesting a possible role in regulation of SMC. Therefore, we investigated whether the TRP channel may be involved SMC evoked by mechanical stretch in pregnant myometrial strips of rat using isometric tension measurement and patch-clamp technique. In the present results, hypoosmotic cell swelling activated a potent outward rectifying current in G protein-dependent manner in rat pregnant myocyte. The current was significantly potentiated by $1{\mu}M$ lanthanides (a potent TRPC4/5 stimulator) and suppressed by $10{\mu}M$ 2-APB (TRPC4-7 inhibitor). In addition, in isometric tension experiment, SMC which was evoked by passive stretch was greatly potentiated by lanthanide ($1{\mu}M$) and suppressed by 2-APB ($10{\mu}M$), suggesting a possible involvement of TRPC4/5 channel in regulation of SMC in pregnant myometrium. These results provide a possible cellular mechanism for regulation of SMC during pregnancy and provide basic information for developing a new agent for treatment of premature labor.

• Physical Therapy Korea
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• v.2 no.2
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• pp.73-84
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• 1995

Spasticity has been defined as a motor disorder characterised by a velocity-dependent increase in tonic stretch reflexes with exaggerated tendon jerks resulting in hyperexcitability of the stretch reflexes as one component of the upper motor neuron syndrome. Weakness and loss of dexterity, however, are considered to be more disabling to the patient than changes in muscle tone. The discussion includes the important role that alterations in the physiology of motor units, notably changes in firing rates and muscle fiber atrophy, play in the manifestation of muscle weakness. This paper considers both the neural and mechanical components of spasticity and discusses, in terms of clinical intervention, the implications arising from recent research. Investigations suggest that the resistance to passive movement in individuals with spasticity is due not only to neural mechanisms but also to changes in mechanical properties of muscle. The emphasis is on training the individual to gain control over the muscles required for different tasks, and on preventing secondary and adaptive soft tissue changes and ineffective adaptive motor behaviours.