• Title, Summary, Keyword: Vickers hardness

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

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    • 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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A study on Weibull Probability Statistics Characteristics for Vickers Hardness of Degraded Stainless Steel (열화된 스테인리스강의 비커스 경도에 대한 와이블 확률 통계 특성에 관한 연구)

  • Nam, Ki-Woo;Cho, Sung-Duck;Kim, Seon-Jin;Ahn, Seok-Hwan
    • Journal of Power System Engineering
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    • v.21 no.5
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    • pp.79-85
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    • 2017
  • Vickers hardness is an important material in the design and reliability is required. Therefore, these values are very important as the basic data for design, manufacture and development, and the identification of quantitative probability distribution characteristics such as mean and dispersion is a very important parameter in design. In this study, Vickers hardness was measured after artificially heat-treated in the temperature range 753K, where chrome depletion near the grain boundary occurred for three kinds of stainless steels, and the Vickers hardness were evaluated. From the results, Vickers hardness increased with increasing heat treatment temperature. In Weibull distribution for Vickers hardness, the dispersion of STS310S at 813K and 873K was small, and the dispersion of STS316L at 753K, 933K and 993K was small. Also, STS347H exhibited the lowest dispersion at 753K in three kinds of stainless steels. The scale parameter increased with increasing heat treatment temperature in three kinds of stainless steels.

Hydrogen Embrittlement Evaluation of Subsurface Zone in 590DP Steel by Micro-Vickers Hardness Measurement (미소경도 측정에 의한 590DP강 Subsurface Zone 내 수소취성 평가)

  • Choi, Jong-Un;Park, Jae-Woo;Kang, Kae-Myung
    • Korean Journal of Materials Research
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    • v.21 no.11
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    • pp.581-586
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    • 2011
  • This study describes a hydrogen embrittlement evaluation of the subsurface zone in 590DP steel by micro-Vickers hardness measurement. The 590DP steel was designed to use in high-strength thin steel sheets as automotive materials. The test specimens were fabricated to 5 series varying the chemical composition through the process of casting and rolling. Electrochemical hydrogen charging was conducted on each specimen with varying current densities and charging times. The relationship between the embrittlement and hydrogen charging conditions was established by investigating the metallography. The micro-Vickers hardness was measured to evaluate the hydrogen embrittlement of the subsurface zone in addition to the microscopic investigation. The micro-Vickers hardness increased with the charging time at the surface. However, the changing ratio and maximum variation of hardness with depth were nearly the same value for each test specimen under the current density of 150 mA/$cm^2$ and charging time of 50 hours. Consequently, it appears that hydrogen embrittlement in 590DP steel can be evaluated by micro-Vickers hardness measurement.

Statistical Properties of Vickers Hardness of Post Weld Heat Treated Friction Welded Parts in Alloy718 (Alloy718 마찰용접 후열처리재의 비커스 경도의 통계적 성질)

  • Kong, Yu-Sik;Kwon, Hyeok-Yong;Kim, Seon-Jin
    • Journal of Ocean Engineering and Technology
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    • v.23 no.6
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    • pp.105-110
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    • 2009
  • The objective of this paper is to investigate the statistical properties of Vickers hardness (HV) for friction welded parts in a Ni-based super alloy (Alloy718). In the case of post weld heat treatment (PWHT) parts, hardness tests were repeated for three different applied loads, 100, 200, and 300 g, with a duration time of 10 seconds. The arithmetic means of the Vickers hardness in heat affected zone (HAZ) materials were smaller than those of the base metal (BM) in all of the applied loads. The coefficient of variation (COV) for the BM and HAZ decreased by increasing the applied load. The probability distribution of the Vickers hardness followed the Weibull distribution well. The distribution of the Vickers hardness was not found to be symmetric. The shape parameter and scale parameter increased by increasing the applied load at both the BM and HAZ.

Weibull Statistical Analysis of Micro-Vickers Hardness using Monte-Carlo Simulation (몬테카를로 시뮬레이션에 의한 미소 비커스 경도의 Weibull 통계 해석)

  • Kim, Seon-Jin;Kong, Yu-Sik;Lee, Sang-Yeal
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.4
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    • pp.346-352
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    • 2009
  • In the present study, the Weibull statistical analysis using the Monte-Carlo simulation has been performed to investigate the micro-Vickers hardness measurement reliability considering the variability. Experimental indentation test were performed with a micro-Vickers hardness tester for as-received and quenching and tempering specimens in SCM440 steels. The distribution of micro-Vickers hardness is found to be 2-parameter Weibull distribution function. The mean values and coefficients of variation (COV) for both data set are compared with results based on Weibull statistical analysis. Finally, Monte-Carlo simulation was performed in order to evaluate the effect of sample size on the micro-Vickers hardness measurement reliability. For the parent distribution with shape parameter 30.0 and scale parameter 200.0 (COV=0.040), the number of sample data required to obtain the true Weibull parameters was founded by 20. For the parent distribution with shape parameter 10.0 and scale parameter 200.0 (COV=0.1240), the number of sample data required to obtain the true Weibull parameters was founded by 30.

A Study on Statistical Properties of Vickers Hardness of Friction Welded Parts in Alloy718 Steel (Part 1. As-welded) (Alloy718 마찰용접재의 비커스 경도의 통계적 성질에 관한 연구 (As-welded 재의 경우를 중심으로))

  • Kwon, Hyeok-Yong;Choi, Sung-Yoong;Lee, Sang-Yeal;Kong, Yu-Sik;Kim, Seon-Jin
    • Journal of Ocean Engineering and Technology
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    • v.22 no.5
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    • pp.87-93
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    • 2008
  • The objective of this paper is the investigation of the statistical properties of Vickers hardness (HV) of friction welded parts in nickel based super resisting steel, alloy 718 steel. First, we examine the statistical properties on the case of as-welded parts. Several Virkers indentations were made under same nominal conditions. This was repeated for three different applied loads, 100, 200 and 300g with a duration time, 10 second. The arithmetic mean of Vickers hardness in base metal (BM) materials is larger than that of HAZ in all applied loads. The measure of dispersion, that is, the coefficient of variation (COV) for BM and HAZ is decreased by increasing with the applied load. The distribution of Vickers hardness was not found to be symmetric type. The probability distribution of Vickers hardness was well followed Weibull distribution. The shape parameter and the scale parameter (characteristic hardness) are increased by increasing with the applied load, as both BM and HAZ.

The effect of wear on the damage of slitting knife (Slitting Knife의 손상에 미치는 마모의 영향)

  • Nam, Ki-Woo;Kim, Cheol-Soo;Ahn, Seok-Hwan
    • Journal of Power System Engineering
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    • v.20 no.4
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    • pp.5-11
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    • 2016
  • This study analyzed the damage to a slitting knife after cutting steel sheets. Damages to the structure were observed and wear tests were conducted. In addition, the degradation on the damaged and undamaged parts was compared with a micro Vickers hardness test. Weibull statistical analysis was carried out in order to evaluate the reliability of the micro Vickers hardness measured data. Spalling of the edge portion occurred by degradation during use over a long period. Rough parts in the specimens were caused by damage because the slitting knife was used for 1 year. The friction coefficient and wear loss at the damaged parts of the knife edge were slightly larger from shock due to repetitive cutting operation. The micro Vickers hardness followed a two-parameter Weibull probability distribution.

A Behavior of Embrittlement at the Subsurface Zones of Multiphase Steels Charged with Hydrogen (수소주입시킨 다상조직강의 Subsurface Zone 내 취성화 거동)

  • Kang, Kae-Myung;Park, Jae-Woo;Choi, Jong-Un
    • Journal of the Korean institute of surface engineering
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    • v.46 no.1
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    • pp.48-53
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    • 2013
  • In the present work, it was investigated a behavior of hydrogen embrittlement at the subsurface zones of 590 DP steels by using the micro-Vickers hardness test. The micro-Vickers hardnessess of DP steels were measured to evaluate the degree of embrittlement as the effective hardening depths of subsurface zones with hydrogen charging conditions. The results showed that the distributions of micro-Vickers hardness in width varied from maximum hardness 239.5 Hv to minimum hardness 174 Hv, while the depth of effective hardening layer at the subsurface zones of DP steels was from $320{\mu}m$ to $460{\mu}m$ with hydrogen charging conditions, respectively. It was proposed that the distribution of microhardness be used as the evaluation index of the degree of embrittlement. But the variations of martensite volume fractions were not affected along depth of hardening at the same changing time, hydrogen charging times were appeared as an effective factor of the degree of embrittlement. Therefore, the micro-Vickers hardness test is an attractive tool for evaluation of hydrogen embrittlement at the subsurface zones of these DP steels.

A Study on new Photoinitiator of Visible Light Dental Composite Resin (치과용 가시광선 중합형 복합수지의 새로운 광개시제에 관한 연구)

  • Choi, Yong-Seok;Sun, Gum-Ju
    • Journal of Technologic Dentistry
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    • v.23 no.2
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    • pp.49-59
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    • 2002
  • The photopolymerization efficiency and surface hardness of composite resin containing 1,2-phenylpropanedione (PD) and diacetyl (DA) as photoinitiators were studied by IR and Vickers hardness and the results were compared with that of camphorquinone (CQ). Relative photopolymerization efficiency of the photoinitiators increased in the order of DA < CQ < PD. Vickers hardness of composite resin containing the photoinitiators increased in the order of CQ < PD < DA. Thus, PD is a new visible light photoinitiator for dental composite resin with higher photopolymerization efficiency and surface hardness than that of CQ. Mechanical properties such as Vickers hardness, diametral tensile strength, and flexural strength of the experimental resin composite prepared by addition of the photosensitizer into a resin of bis-GMA improved with increasing the photosensitizer content and irradiation time. The resin composite of bis-GMA containing DA or PD shows better mechanical properties than that of CQ.

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