• Title, Summary, Keyword: Hardness Test

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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.

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.

Analysis on the Results of the Rockwell Hardness Round Robin Test (로크웰 경도도 순회 비교측정 결과에 대한 분석)

  • Bahng, G.W.;Tak, N.H.
    • Journal of the Korean Society for Heat Treatment
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    • v.14 no.5
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    • pp.275-281
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    • 2001
  • To improve the reliability of hardness test results, Rockwell hardness round robin test was carried out for 10 laboratories. The test condition was the same with the ISO(International Standards Organization) standards. Korea Research Institute of Standards and Science(KRISS) supplied the hardness standard blocks and an indenter to laboratories for the measurement. The participating laboratories measured hardness of the specified areas on the blocks for 6 times with their own indenter as well as common indenter, respectively, and reported the results to KRISS. The result showed that quite large amount of the differences came from the indenter and it is necessary to change indenter with better quality for improved reliability in hardness measurement.

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Mechanical Properties of Minerals in Daejeon Granite According to Depths by Dynamic Ultra-micro Hardness (동적 초미소 경도법에 의한 심도별 대전화강암 내 광물들의 역학적 특성)

  • Choi, Junghae;Shin, Juho;Jang, Hyongdoo;Kang, Seong-Seung
    • Tunnel and Underground Space
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    • v.27 no.3
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    • pp.172-184
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    • 2017
  • The hardness and mechanical properties of the minerals in the Daejeon granite according to depths were investigated by indentation test, load-unload test, and cycle test of dynamic ultra-micro hardness. As a result of the tests, it was possible to classify into three mineral groups (Group-1, -2, -3). The Martens hardness was not significantly different between 41 m and 223 m depths in three mode tests. Nevertheless, they showed in the order of a cycle test < load-unload test < indentation test. Considering the average Martens hardness, elastic modulus, and indentation work for each mineral group, their boundaries were relatively clear. In conclusion, A relatively accurate hardness of minerals can be obtained by three mode tests of dynamic ultra-micro hardness. In addtion, it was possible to characterize the elastic modulus and the elastic-plastic properties of the minerals from the load-unload and cycle tests.

The Effect of Test Variables on the Accuracy of Equo-Tip Hardness (Equo-Tip 경도값에 미치는 실험변수의 영향)

  • Nahm, S.H.;Jeon, S.B.;Kim, J.J.
    • Journal of the Korean Society for Heat Treatment
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    • v.3 no.2
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    • pp.32-36
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    • 1990
  • For the accurate measurements of hardness in a material, it is necessary to have a thorough understanding of the effects of test variables on the accuracy of hardness value. For the rebound hardness test, major test variables are the radius of hammer ball tip, type of backing materials, size and roughness of the specimen. In this study, effects of these variables on Equo-Tip hardness value were investigated. Hardness measurements were carried out using WC balls with various sizes of worn-ot zone. The sample materials chosen for the experiments were commercial standard hardness blocks and SM45C steel bars subjected to either normalization or quench and temper treatments. As backing materials, aluminum, steel and rubber plates were used in all the experiments. Experimental results show that for the accurate measurements of Equo-tip hardness, it is necessary to use the hammer ball with a worn-out zone parameter of less than 0.23, and the recommended minimum thickness and width of the specimen are 25mm and 70mm, respectively. Further for the surface preparation, the specimens need to be polished with an emery paper of No. 400 or finer, and for the backing matrials, it is recommended to use steels or rubbers.

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A Study on the Analysis of Plastic Zone in Carbon Steel after Strain Aginig (변형시효처리한 탄소강의 소성역 해석에 관한 연구)

  • 손세원;이진수;장정원
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.933-937
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    • 1996
  • In this paper, the behavior of plastic zone in the notch tip was studied under Loye's Micro Vickers Hardness Measurement Method. The direction forming maximum plastic zone was estimated by finite element analysis. In the experiments, cold rolling sheet SGCD3, SK5 and hot rolling sheet SS41, S4SC was used to study the influence of carbon contents on plastic zone. The standard hardness test specimen and the notch hardness test specimen was made and loaded cyclically. The specimen was aged to stabilize the hardness. After aging treatment, the notch specimen was made and simple tension load of 50% yield strength was applied. The hardness test at the notch tip until the hardness data of standard hardness specimen was checked was performed.

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Preparation and Erosion Properties of Reaction-Bonded SiC Reinforced by Carbon Fiber (탄소섬유로 강화된 반응소결 SiC 제조 및 Erosion 특성)

  • 송진웅;임대순;김형욱
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.258-264
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    • 1998
  • Three kinds of reation-bonded SiC that reaction-bonded SiC(RBSC), RBSC reinforced by carbon fiber and RBSC reinforced by activated carbon fiber were prepared for investigating the change of erosion properties. The characteristics of microstructures and the phases have been investigated by using scanning electron microscope and XRD analysis. The hardness test, toughness test and erosion test were camed out. In the cases with no carbon fiber, those kind of specimens had the highest result of hardness test and the lowest result of toughness test. With the increase of carbon fiber content, The hardness and the weight loss were decreased but the toughness was increased in the cases with carbon fiber In the cases with activated carbon fiber those specimens had the highest result of toughness test and the lowest result of hardness test with 30% contents of activated carbon fiber.

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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.

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 Estimation of Compressor Journal for a Use of Instrumented Indentation Techniques (계장화 압입시험법을 이용한 차량용 컴프레서 저널 경도 평가)

  • Kwak, Sung-Jong;Jin, Ji-Won;Kim, Tae-Seong;Noh, Ki-Han;Kang, Ki-Weon
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.21 no.3
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    • pp.376-381
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    • 2012
  • This paper deals with application of instrumented indentation technique for quality inspection methodology for automobile component. For this, the instrumented indentation tests were performed the normal and cracked compressor journal, which is made from spheroidal graphite cast iron and utilized in air-conditioning system. And the Brinell hardness was estimated using the unloading slope and maximum indentation force. With the aid of Normal distribution, this Brinell hardness was statistically compared and analyzed with hardness measured by indentation hardness tests. Also, application possibility of reliability-based quality inspection criteria for compressor journal was evaluated through the probabilistic analysis for the Brinell hardness estimated by instrumented indentation technique.