• Fashion & Textile Research Journal
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• v.10 no.3
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• pp.389-393
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• 2008

The purpose of this study is to provide beauticians with the fundamental material for them to use effectively heat permanent wave and satisfy their customers. It carried out an experiment with hair of a woman in her late twenties to investigate the change of physical and morphologic characteristics by its water content when performing heat permanent wave. It evaluated the water content as 0g, 1g, 2g, 3g and 4g respectively when performing the heat permanent wave on hair, then it compared and observed the wave type, tensile strength and elongation for its physical change also observed the morphologic change by scanning electronic microscope and transmission electronic microscope. The result of experiment on the physical specificity revealed that the wave was the most ideal when the water content was 2 g. The material with much water content made wave but the result was not satisfied. In the case of hair with water content of nearly 0g didn't make wave. In terms of tensile strength and elongation, the tensile strength was generally reduced as hair was damaged, on the contrary, the elongation was increased. It observed the change of morphologic characteristic and got the result that the damage on hair cuticle was deepen as its water content was decreased. It also showed the result that damage happened on hair cuticle more than hair cortex with the observation of fine structure on hair section by transmission electronic microscope. Generally chemical treatment damaged hair. Under consideration of this aspect, the ultimate goal of this thesis is to minimize the damage of hair caused by chemical treatment and get the satisfaction on the hair style. The result of experiment presented that the hair showed the best result when its water content was 2 g.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.1
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• pp.7-14
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• 2023

We investigated the effect of multiple tempering on the microstructure and mechanical properties of AISI 4340 steel. The austenitized and quenched AISI 4340 steels were tempered at 550, 600, and 650℃ for 1, 2, and 4 h by single-tempering (ST). The multiple tempering was conducted for 4 h by double-tempering (DT, 2 h + 2 h), and quadruple-tempering (QT, 1 h + 1 h + 1 h + 1 h). As tempering temperature increases, yield strength and ultimate tensile strength decrease and elongation increases due to recovery and recrystallization of martensite and coarsening of carbides. At 550℃, as the number of tempering cycles increases, the yield strength and tensile strength decrease at the expense of fracture elongation. At 600 and 650℃, the yield strength and tensile strength increase with increasing the number of tempering cycles while fracture elongation maintains similar values. The multiple tempering at the same tempering time of 4 h improves the modulus of toughness at all tempering temperatures, which is presumed to be due to the change in carbide precipitation behavior by multiple tempering.

• The Journal of Korean Academy of Prosthodontics
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• v.19 no.1
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• pp.17-27
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• 1981

This study was conducted to determine the chemical composition and the mechanical properties of four commercially available low gold-based crown and bridge alloy produced in Korea. Four dental casting gold-silver-palladium alloys, i.e., A, B, C and D (code of alloys) were selected for the evaluation of chemical composition, ultimate tensile strength, elongation. values and Vickers hardness. The chemical composition of test specimens was analyzed by both emission spectrography and wet gravitation method with a 1.5gm of low gold ingot. The tensile properties and Vickers hardness was determined with cast specimens treated in following three conditions; as-cast, softening heat treatment and hardening heat treatment. The tensile testing bars were cast in accordance with the model designed by Gettleman and Harrison (1969) which was modified from the A. D. A. Specification No. 14 for dental chromium-cobalt casting alloy. Nine tensile test specimens were made from a split silicone mold for each of the test alloys to the size of 2.5mm in diameter and a gauge length of 10mm. All four alloys were handled in accordance with conventional methods used in Type III gold alloys. Ultimate tensile strength and elongation were measured on an Instron Universal Tensile Testing Machine (Model 1125, Japan) operated at a crosshead rate of 0.1cm/min. Elongation values were measured using Digital Measuring Microscope (MS-152, FUSOH, Japan). Vickers hardness was determined with a Vickers Hardness Tester (Model VKH-l, Japan) at a 1.0kg load on a mounted tensile test specimen. The following results were obtained from this study; 1. All tested alloys were composed of Au, Ag, Pd, Cu, Zn and Fe in common. The composition rate of gold for all four alloys was found in the range of $42{\sim}47$ weight % as shown below. Alloy A; Au 45%, Ag 40.2%, Pd 5.76%, others 9.04%. Alloy B; Au 47.1%, Ag 29.03%, Pd 6.98%, others 16.92%. Alloy C; Au 45%, .Ag 26.9%, Pd 6.83%, others 21.07%. Alloy D; Au 41.8%, Ag 34.4%, Pd 6.95%, others 16.85%. 3. The ultimate tensile strength of the four alloys was in the range of $31{\sim}82kg/mm^2$. The test results were shown in the below order from the highest value; As-cast condition; D, B, C, A. Softening heat treament; B, C, D, A. Hardening heat treatment; D, B, C, A. 4. The test :results of the elongation rate for each alloy were in the range of $0.5{\sim}18%$. The test results were shown in the below order from the highest value; As-cast condition; A, D, B, C. Softening heat treatment; A, C, D, B. Hardening heat treatment; C, D, B, A. 5. Vickers hardness for each of the four alloys was in the range of $120{\sim}230$. The test results were shown in the below order from the highest value; As-cast condition; C, B, D, A Softening heat treatment; D, B, C, A. Hardening heat treatment; D, A, C, B. 6. There were no differences in the physical properties between as-cast condition and softening heat treatment.

• Clinics in Shoulder and Elbow
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• v.12 no.2
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• pp.207-214
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• 2009

Purpose: In arthroscopic rotator cuff repairs there are generally weak link in tendon suture interface, arthroscopic rotator cuff repairs can have higher retear rates than open repairs. The purpose of this study was to compare the strength of UU (Ulsan University) suture than open modified MA (Mason-Allen) suture when suture anchored into bone. Materials and Methods: The human supraspinatus tendons were harvested from the shoulder of the cadaver and split in 2 times, producing four tendons per one shoulder, for a total of 24 specimens. Two suture configurations (UU, MA) were randomized and checked on each set of tendons. Specimens were cyclically loaded under force control between 5 and 30 N at 0.25 Hz for fifty cycles. Each specimen was loaded to failure under displacement control at 1 mm/sec. Cyclic elongation, peak to peak displacement, stiffness, ultimate tensile load, mode of failure were checked. Results: No significant difference was found between two suture configuration with respect to peak to peak displacement, cyclic elongation, and stiffness. With regard to ultimate failure load, there were no significant difference statistically between the UU suture and modified MA suture (109.4 N, 110.6 N). The most common mode of failure between both sutures was suture pull-out through the tendon. Conclusion: The UU suture and modified MA suture produced similar biomechanical properties.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.2
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• pp.101-106
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• 1982

This study was undertaken to determine tensile properties and low-cycle fatigue behavior of 0.6%C high carbon steel used of structural purposes at temperatures up to 500.deg.C. In the low-cycle fatigue test the upper limit was decided by elongation(i.e. the total strain range), while the lower limit was defined by the load (i.e. zero load). The following results were obtained. Both, the ultimate tensile strength and low-cycle fatigue resistance attain the maximum values near 250.deg.C. Above this temperature the values decrease rapidly as the temperature increases. The low-cycle fatigue resistance decreases whenever there is an increase of the total strain range. Because the hardness of cycle fatigued specimen correlates cyclic hardening and cyclic softening, therefore the hardness of cycle fatigued specimen is smaller than that of the nonfatigued specimen at room temperature and 500.deg.C but much larger than the hardness of the nonfatigued specimen near 250.deg.C.

• Korea-Australia Rheology Journal
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• v.11 no.4
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• pp.293-304
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• 1999

Refinements of classical theories for entangled or crosslinked polymeric systems have led to incommensurable models for rubber networks and polymer melts, contrary to experimental evidence, which suggests a great deal of similarity. Uniaxial elongation and compression data of linear and branched polymer melts as well as of crosslinked rubbers were analyzed with respect to their nonlinear strain measure. This was found to be the result of two contributions: (1) affine orientation of network strands, and (2) isotropic strand extension. Network strand extension is caused by an increasing restriction of lateral movement of polymer chains due to deformation, and is modelled by a molecular stress function which in the tube concept of Doi and Edwards is the inverse of the relative tube diameter. Up to moderate strains, $f^2$ is found to be linear in the average stretch for melts as well as for rubbers, which corresponds to a constant tube volume. At large strains, rubbers show maximum extensibility, while melts show maximum molecular tension. This maximum value of the molecular stress function governs the ultimate magnitude of the strain-hardening effect of linear and long-chain branched polymer melts in extensional flows.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.159-162
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• 1999

This study has been performed to investigate forming limit of PCM(Pre-Coated Metal) widely using appliances. Die set was made for deep drawing test and some PCMs were inrectangular deep drawing test in no-lubricant 20% clearance some die materials(STD11(TiCN) STD11(HrC60) STD11(TD) AMOCO and 6mm/sec punch speed. and Ericshen test was performed in regular conditions In this experiment forming limit forming characteistics superior die materials and fracture of PCMs been investigated. In results tested PCMs have lower forming limit than base material because lower elongation ultimate strength than base material And two-fracture types - occurring band and flaking - of PCMs have been investiqated.

• Journal of Powder Materials
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• v.13 no.6 s.59
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• pp.427-431
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• 2006

Mg-4.3Zn-0.7Y (at%) alloy powders were prepared using an industrial scale gas atomizer, followed by warm extrusion. The powders were almost spherical in shape. The microstructure of atomized powders and those extruded bars was examined using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscope (EDS) and X-ray Diffractometer (XRD). The grain size of the powders was coarsen as the initial powder size increased. After the extrusion, the grain size became fine due to the severe plastic deformation during the extrusion with the ratio of 10:1. Both the ultimate strength and elongation were enhanced with the decrease of initial particle size.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.345-347
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• 2007

The microstructures and mechanical properties with the different Sc content of AA2519 FSW joint were investigated in this study. The sound FSW joints were obtained under applied all welding conditions such as the Sc content and the tool rotation speed. The grain size of the stir zone decreased slightly with increasing the Sc content. And the ultimate tensile strength increased and elongation decreased with increasing the Sc content. The intermetallic compound contained the Sc is considered to bring out the improvement of mechanical property in FSW joint.

• Journal of Powder Materials
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• v.14 no.2 s.61
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• pp.140-144
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• 2007

Using Spark Plasma Sintering process (SPS), consolidation behavior of gas atomized $Mg_{97}Zn_1Y_2$ alloys were investigated via examining the microstructure and evaluating the mechanical properties. In the atomized ahoy powders, fine $Mg_{12}YZn$ particles were homogeneously distributed in the ${\alpha}-Mg$ matrix. The phase distribution was maintained even after SPS at 723 K, although $Mg_{24}Y_5$ particles were newly precipitated by consolidating at 748 K. The density of the consolidated bulk Mg-Zn-Y alloy was $1.86g/cm^3$. The ultimate tensile strength (UTS) and elongation were varied with the consolidation temperature.