• Title, Summary, Keyword: hardness

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Wear Behavior as Hardness Difference of Material in the Dry Sliding Wear Tests of Using Leaf-Spring (판스프링을 사용한 건식마모실험에서 재료경도에 따른 마모거동)

  • Kim, Jung-Hyun
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.17 no.3
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    • pp.27-33
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    • 2008
  • It is shown that the rate of wear can be related to 'index of wear intensity' using a leaf-spring in the disc on disk on wear tests. Since both upper and lower specimens have used the same hardness values, equivalent hardness of 'the index of wear intensity' used the mean hardness value of specimens. This index is derived from the external variables of load, sliding speed and the hardness of the sliding pairs. The wear behavior as the hardness of the sliding elements on the dry wear has been investigated using a disc on disc configuration. The materials of the specimens are used as ten kinds along their hardness. Using experimental data, we figured the relationship between wear rate and index of wear intensity. A newly wear equation had been derived the result using a leaf-spring in disc on disc wear system.

Study on the Mechanical Properties and Microstructure of Nickel Sulfamate Electroform (니켈쌀파메이트 전주층의 물성과 미세구조)

  • 김인곤
    • Journal of the Korean institute of surface engineering
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    • v.37 no.1
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    • pp.40-48
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    • 2004
  • Hardness and internal stress are very important in nickel electroforming. Nickel sulfamate bath has been widely used in electroforming because of its low internal stress and moderate hardness. Nickel sulfamate bath without chloride was chosen to investigated the effect of plating variable such as temperature, PH, current density and sodium naphthalene trisulfonate as addition agent on the hardness and internal stress. It was found that hardness increased with increasing temperature and decreasing current density and ranged from 150∼310 DPH. The hardness was highest at $55^{\circ}C$ and 10∼40 mA/$\textrm{cm}^2$. The internal stress increased with increasing current density and decreasing temperature. It was minimum at PH 3.0∼3.8. Low internal stress within $\pm$1,500 psi was obtained at both $50^{\circ}C$ and $55^{\circ}C$ in 10-20 mA/$\textrm{cm}^2$. The addition of sodium naphthalene trisulfonate was found to be effective in refine columnar grains thus resulted in decreasing internal stress, increasing hardness and improving brightness.

A Study of Unlubricated Sliding wear of materials as hardness difference (경도의 차이에 따른 재료들의 비윤활 미끄럼 마모에 대한 연구)

  • Kim, Jung-Hyun
    • Journal of the Korean Society of Industry Convergence
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    • v.7 no.4
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    • pp.369-376
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    • 2004
  • It is shown that the rate of wear can be related to on 'index of wear intensity'. Since both upper and lower specimens have used the same hardness values, equivalent hardness of 'index of wear intensity' used the mean hardness value of specimens. This index is derived from the external variables of load, sliding speed and the hardness of the sliding pairs. The wear behavior as the hardness of the sliding elements on the dry wear has been investigated using a disc on disc configuration. The materials of the specimens are used as ten kinds along their hardness. Using experimental data, we figured the relationship between wea rate and index of wear intensity. The result had been derived a newly wear equation in disc on disc wear system.

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Hardness Analysis of Surface Treated Magnesium Alloy using Laser Induced Breakdown Spectroscopy (레이저 플라즈마 분광분석법을 이용한 표면처리 된 마그네슘 합금 표면의 경도 분석)

  • Kang, Dongchan;Kim, Joohan
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.24 no.6
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    • pp.625-631
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    • 2015
  • The hardness of surface treated magnesium alloy was evaluated using laser induced breakdown spectroscopy. The surface of the specimen was hardened mechanically, and the hardness profiles were measured using a traditional measurement technique. A laser beam was irradiated to generate a plasma, and the peaks of the components of the specimen were analyzed. A wavelength of 333.66 nm and 293.65 nm were selected as the atomic and ionic peaks, respectively. The ratios of the ionic peak to the atomic peak were obtained so as to compare the hardness profile. As the depth increased, the ratio decreased. These results are in good agreement with the previous hardness measurement results. It can be considered that this technique could be applied for remote and time-efficient hardness measurement.

Rockwell Hardness Modeling Using Volumetric Variable (체적변수를 이용한 로크웰 경도 모델링)

  • Chin, Do-Hun;Oh, Sang-Rok;Yoon, Moon-Chul
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.22 no.3
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    • pp.394-401
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    • 2013
  • A new Rockwell hardness (HRC) model using a volumetric parameter by a least square and fractal interpolation method is suggested. The results are also investigated in comparison to real measured hardness data. For this purpose, the measurement of an indented volume is performed using a confocal laser scanning microscope (CLSM), and the captured height encoded image (HEI) is used as an original surface for the calculation of the indented volume. After configuring the surface, the constructed volume is calculated and used as an independent variable for HRC hardness modeling. The hardness model is established using an experimental modeling technique involving a least square algorithm and fractal interpolating model, and this suggested model can be used to reliably predict the Rockwell hardness. These techniques can also be applied to the modeling of the Brinnell and Vickers hardnesses using a volumetric variable.

An Experimental Study on the Relation between Flow Stress and Vickers Hardness (유동응력과 비커스경도의 관계 실험적 연구)

  • 이충호
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.65-68
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    • 1997
  • Vickers hardness is defined as indenting force per unit area indented by a pyramid-shaped diamond at the hardness test. It is well known that Vickers hardness has a direct relation with the flow stress of the strain-hardened material. This relation was theoretically investigated and the result was summerized in a form of algebraic equation in the last paper. In the present paper and experimental validation of this theoretical relation is given along with mathematical formulas for conversion of Vickers hardness into the flow stress in the strain-hardened material for practical use.

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A Study on the Theoretical Relation between Flow Stress and Vickers Hardness (유동응력과 비커스경도의 이론적 관계 연구)

  • 이충호
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.69-72
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    • 1997
  • The indentation process in the Vickers hardness test is a kind of controlled local plastic deformation. Vickers hardness is defined as indenting force per unit area indented by a pyramid-shaped diamond at the hardness test. That is a measure of mechanical resistance against indentation of a rigid body into the deformable material. Therefore it is well known that Vickers hardness has a direct relation with the flow stress of the strain-hardened tmaterial. This relation is theoretically investigated and the result is given for use in practice.

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Hardness Prediction and First Principle Study of Re-123(Re = Y, Eu, Pr, Gd) Superconductors

  • Liu, Weiwei;Zhou, Y.P.;Feng, X.L.
    • Bulletin of the Korean Chemical Society
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    • v.30 no.12
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    • pp.3016-3020
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    • 2009
  • The chemical bond parameters of Y-123, Eu-123, Pr-123 and Gd-123 compounds have calculated using the chemical bond theory of complex crystals. Their hardness have been predicted by the chemical bond definition of hardness. The calculated results indicate that the Ba-O and RE-O types of bond have a lower covalent character and the Cu-O types of bond have greater covalency. The hardness values increase as the unit cell volume of the rare earth superconductor structures decrease.

A Study on the Heat Treatment Effect of SCM Series Gear (SCM계 기어의 열처리 효과에 관한 연구)

  • Ahn, Min-Ju;Ahn, In-Hyo;Zhang, Qi;Lyu, Sung-Ki
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.10 no.2
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    • pp.84-89
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    • 2011
  • This paper studied the carburizing of chromium molybdenum steel which the heat treatment effect of gear geometric tolerance, OPD, Runout, the surface hardness, the maximum hardness, the core hardness and the bending fatigue strength were investigated. Firstly, the deformation is observed, and the results of circularity, squareness, OPD and Runout of SCM822, SCM425, and SCM415 are obtained in order. Secondly, in order to investigate the gear hardness, the surface hardness, the maximum hardness and the core hardness of SCM822, SCM425, and SCM415 are obtained; and the surface hardness of SCM822 is about 10% higher than SCM415's, and about 3% higher than SCM425's. Thirdly, the fatigue strength of SCM822 is about 10% higher than SCM415's, and about 7% higher than SCM425's in the fatigue test results. At last, for the purpose of the minimum deformation of heat treatment, and also the improvement of fatigue strength, the best gear material is SCM822 in this test.

The Effect of Midsole Hardness of Running Shoe on Fatigue of Lower Extremity Muscles and Impact Force (런닝화의 미드솔 경도가 하지 근육의 피로와 충격력에 미치는 영향)

  • Kim, Eonho;Lim, Kyuchan;Cho, Seunghyun;Lee, Kikwang
    • Korean Journal of Sport Biomechanics
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    • v.29 no.3
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    • pp.167-172
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    • 2019
  • Objective: The aim of this study was to investigate the effect of midsole hardness of running shoe on muscle fatigue and impact force during distance running. Method: Ten healthy college recreational runners who were performing distance running at least three times a week participated in this experiment. They were asked to run for 15 minutes in the treadmill at 10 km/h with running shoes having three different types of midsole hardness (Soft, Medium, Hard). EMG signal and insole pressure were collected during the first and last one minute for each running trials. Data were analyzed using a one-way analysis of variance (ANOVA) with repeated measures. Results: Midsole hardness did not affect the consistency of stride length. For the median frequency of the EMG signal, only VL was affected by midsole hardness; that of medium was greater than other midsoles (p<.05). The loading rate of impact forces increased by midsole hardness (p<.01). Conclusion: Although soft midsole could attenuate impact forces at heel contact, it might have a negative effect on the fatigue of muscle which could decelerate the body after heel contact. Therefore, it is necessary to select the optimum hardness of midsole carefully for both reduction impact forces and muscle fatigue.