• Title, Summary, Keyword: hardness

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A Study on the Establishment of Shore Hardness Standards (쇼어경도표준의 확립에 관한 연구)

  • Bahng, G.W.;Tak, Nae-Hyung;Bong, Haheon
    • Journal of the Korean Society for Heat Treatment
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    • v.15 no.3
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    • pp.127-135
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    • 2002
  • Shore hardness test was developed in 1906 to overcome the limit of Brinell hardness test. However, the detailed requirements on the tester was not clearly specified except the scale, i.e., 100 HS for high carbon steel and 10 HS for soft brass. As a result, the shore hardness was used for quite long time without well established standards. For the establishment of hardness standards, standard tester, standard procedure, and standard hardness block must be provided. So far the standard of Shore hardness was maintained by correlating Shore hardness scale to Vickers hardness through converting equation. This is the so called converted Shore hardness and it is not the true Shore hardness standard strictly. In this paper, the possibility of establishing Shore hardness standard based on the Shore standard hardness tester is reported.

Discussion on Hardness Measuring of Bearing Steel by X-ray Diffraction (X선회절에 의한 베어링강의 경도측정에 대한 고찰)

  • 이한영
    • Tribology and Lubricants
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    • v.18 no.3
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    • pp.187-193
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    • 2002
  • The half-value breadth off-ray diffraction profile line is generally used for a factor in nondestructive hardness measuring method of steel. In this paper, the problem in using the half-value breadth for the hardness measuring method is evaluated in strain hardened steel. And new hardness measuring method using residual stress is proposed X-ray diffraction test after rolling contact fatigue test of ball bearing with inner race of various hardness are carried out to measure the distribution of residual stress and half-value breadth from surface. The result of this study shows that there is little correlation between half-value breadth and hardness in the higher strength region and in the region increasing the hardness by strain hardening. But the magnitude of residual stress on/under race after rolling contact fatigue test becomes clearly to be correlative with hardness. Thus, it is concluded that the hardness of strain hardened steel can be estimated by this relationship between residual stress and hardness.

A Study on Hardness and Effective Strain of Cold-Worken Products (냉간 가공 제품의 경도와 유효 변형률에 관한 연구)

  • Choi, Young;Park, Jun-Hong
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.9
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    • pp.142-148
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    • 2004
  • It is already known that hardness number of cold-forged product is in close conjunction with its effective strain. This paper presents the method to predict the relation between effective strains and hardness by using FE-simulation of hardness test from the conception that hardness indicates resistance to plastic deformation. The results of FE-simulation for the materials are compared with those of experiments and also compared with those of experiments in reference to show the feasibility of the proposed method. In addition, the present method was applied to the cold-forged product to verify the relation between hardness and effective strain. As a result, the predicted hardness number by the present method is in good agreement with experimental values. Prediction of hardness fur a cold-forged product comes to be possible by estimating the relation between effective strain and hardness using the proposed method in this study.

Hardness Distribution and Microstructures of Electric Resistance Spot Welded 1GPa Grade Dual Phase Steel (1GPa급 DP강 전기저항점용접부의 경도분포와 미세조직의 상관관계)

  • Na, Hye-Sung;Kong, Jong-Pan;Han, Tae-Kyo;Chin, Kwang-Geun;Kang, Chung-Yun
    • Journal of Welding and Joining
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    • v.30 no.2
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    • pp.76-80
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    • 2012
  • In this study, the effect of the welding current on the hardness characteristics and microstructure in the resistance spot welding of 1GPa grade cold-rolled DP steel was investigated, Also, correlation between the hardness and microstructure was discussed. In spite of the change in the welding current, the hardness distributions near weld was similar. the hardness in the HAZ and the fusion zone was higher than that of the base metal and the hardness in the fusion zone was variated with the location. Especially, the hardness of HAZ adjacent to the base metal showed maximum value, and softening zone in the base metal adjacent to HAZ was found. With the increasing of welding current, there were no difference in maximum hardness and average hardness in the fusion zone were, but the hardness of the softening zone reduced. The difference in the hardness in each location of weld due to grain size of prior austenite. The softening of the base metal occurred by tempering of the martensite.

Studying Hardness Meter Spring Strength to Understand Hardness Distribution on Body Surfaces

  • Arima, Yoshitaka
    • Journal of Acupuncture & Meridian Studies
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    • v.10 no.5
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    • pp.340-345
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    • 2017
  • Introduction: For developing a hardness multipoint measurement system for understanding hardness distribution on biological body surfaces, we investigated the spring strength of the contact portion main axis of a biological tissue hardness meter (product name: PEK). Methods: We measured the hardness of three-layered sheets of six types of gel sheets ($90mm{\times}60mm{\times}6mm$) constituting the acupuncture practice pads, with PEK measurements of 1.96 N, 2.94 N, 3.92 N, 4.90 N, 5.88 N, 6.86 N, 7.84 N, 8.82 N, and 9.81 N of the main axis spring strength. We obtained measurements 10 times for the gel sheets and simultaneously measured the load using a digital scale. We measured the hardness distribution of induration embedded and breast cancer palpation models, with a main axis with 1.96 N, 4.90 N, and 9.81 N spring strengths, to create a two-dimensional Contour Fill Chart. Results: Using 4.90 N spring strength, we could obtain measurement loads of ${\leq}3.0N$, and the mean hardness was 5.14 mm. This was close to the median of the total measurement range 0.0 -10.0 mm, making the measurement range the largest for this spring strength. We could image the induration of the induration-embedded model regardless of the spring strength. Conclusion: Overall, 4.90 N spring strength was best suited for imaging cancer in the breast cancer palpation model.

Estimation of Hardness using DEFORM$^{TM}$ in SKH9 High Speed Steel (DEFORM$^{TM}$을 이용한 SKH9 고속도공구강의 경도 예측)

  • Park, Joon Hong;Sung, Jang Hyun;Kim, Young Hee;Lee, Hae Woo;Jeon, Eun Chan;Park, Young Chul
    • Journal of the Korean Society for Heat Treatment
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    • v.20 no.4
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    • pp.175-180
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    • 2007
  • The hardness of cold-forged products is in close relationship with its effective strain. This study presented the estimating method of hardness for cold-forged SKH9 products without hardness tests in view of resistance to plastic deformation using finite element code, DEFORM$^{TM}$. The flow stress equation obtained from the compression test was only used as a basic data to estimate the relationship between effective strain and hardness. In addition, this new estimating method was applied to the cold-forged product which was widely used in industrial field to show the feasibility. As a result, the predicted hardness numbers through FE simulation showed good agreement with the measured hardness numbers. It is possible to estimate the hardness not by hardness tests, but by only computer simulations for the deformed products. Also, effective strain values were possibly estimated by measuring hardness numbers, and vice versa.

The Relation between Applied Stress and Rebound Hardness Values (부가응력과 반발경도와의 관계)

  • Nahm, S.H.;Kim, S.C.;Jeon, S.B.
    • Journal of the Korean Society for Heat Treatment
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    • v.8 no.4
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    • pp.318-325
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    • 1995
  • Information of change of hardness values during applying load is needed often to control the quality of metal products efficiently, but the relation between applied stress and hardness has not been established. In this paper the theoretical relation between the rebound hardness and stress was examined briefly and the experiment was performed with some materials. Materials used in test were mild steel(SB41), 7-3 brass and copper, which were widely used in the commercial plants. Hardness was measured during stress applied using the Equo-Tip hardness tester as a kind of rebound hardness tester. Hardness values decreased as tensile stress increased, the decreasing rate was effected by the Young's modulus of each material, and the rebound hardness values showed linear relationship with the applied stress in elastic region.

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Effects of Substrate Hardness on the Hardness and Adhesion of TiN Deposited by R.F. PACVD (R.F. PACD에 의하여 증착된 TiN의 경도와 밀착력에 미치는 모재 경도의 영향)

  • Kim, S.K.;Kim, M.I.
    • Journal of the Korean Society for Heat Treatment
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    • v.4 no.1
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    • pp.19-29
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    • 1991
  • This study was to investigate the influence of the substrate hardness on the hardness and adhesion of TiN thin film deposited by R.F. PACVD. Although the substrate hardness changed, chemical composition, stoichiometry and structure of TiN thin film did not change. ISE index was 1.96-1.99 for the substrate and was 1.57-1.79 for TiN thin film. And ISE index of TiN thin film was inverse proportion to the substrate hardness. When the substrate hardness was low, TiN thin film had many cracks around the indentation. But as the substrate hardness increased, TiN thin film had a few cracks and the deformation was limited within indentation. In having measured the adhesion of TiN thin film by SAT, the critical load (Lc) generally increased as the substrate hardness decreased.

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Determination of Brinell Hardness through Instrumented Indentation Test without Observation of Residual Indent (계장화압입시험법을 이용한 비압흔관찰 브리넬 경도 평가)

  • Kim, Sung-Hoon;Choi, Yeol;Kwon, Dong-Il
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.5
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    • pp.578-585
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    • 2004
  • Hardness test is performed for determination of the other properties, such as strength, wear resistance and deformation resistance, as well as hardness itself. And it is performed for prediction of residual lifetime by analysis of hardness reduction or hardness ratio. However, hardness test has limitation that observation of residual indent is needed for determination of hardness value, and that is the reason for not to be widely used in industrial field. Therefore, in this study, we performed researches to obtain Brinell hardness value from quantitative numerical formula by analysing relationship between indentation depths from indentation load-depth curve and mechanical properties such as work hardening exponent, yield strength and elastic modulus.

Relationship between Barcol hardness and flexural modulus degradation of composite sheets subjected to flexural fatigue

  • Sakin, Raif
    • Steel and Composite Structures
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    • v.19 no.6
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    • pp.1531-1548
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    • 2015
  • The aim of this study is to investigate the relationship between Barcol hardness (H) and flexural modulus (E) degradation of composite sheets subjected to flexural fatigue. The resin transfer molding (RTM) method was used to produce 3-mm-thick composite sheets with fiber volume fraction of 44%. The composite sheets were subjected to flexural fatigue tests and Barcol scale hardness measurements. After these tests, the stiffness and hardness degradations were investigated in the composite sheets that failed after around one million cycles (stage III). Flexural modulus degradation values were in the range of 0.41-0.42 with the corresponding measured hardness degradation values in the range of 0.25-0.32 for the all fatigued composite sheets. Thus, a 25% reduction in the initial hardness and a 41% reduction in the initial flexural modulus can be taken as the failure criteria. The results showed that a reasonably well-defined relationship between Barcol hardness and flexural modulus degradation in the distance range.