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한국산업표준(KS)에 따른 로크웰 경도 시험기의 불확도 산정에 관한 연구
탁내형,방건웅 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.3
Recently, uncertainty of hardeness became a major concern for the people working on the laboratory evaluation and accreditation. It is required to indicate uncertainty of hardness tester on the report after calibration. In addition to this, uncertainty of certified hardness reference block is also required to indicate on the certification sheet. Method on the evaluation of uncertainty in hardness measurement is agreed only recently for Rockwell hardness C scale. In this paper, a preliminary calculation of uncertainty based on type B evaluation has been made for hardness testers which satisfies the requirements of Korean Standards. It was found that the tolerance limit of mean value specified in KS should be increased to be compatible with the calculated uncertainty.
브리넬 경도 표준 시험기 및 압입 자국 자동 측정장치의 특성 평가에 대한 연구
방건웅,탁내형 한국열처리공학회 1999 熱處理工學會誌 Vol.12 No.4
Evaluation of Brinell standard hardness tester was carried out to secure its application as a national standard for Brinell hardness. Accuracies and reliabilities in load application, indenter diameter and indentation measurement were tested through evaluation of these components. The accuracies of load application for various loading conditions were within the limit of ISO and KS specifications. Errors in the indentation measurement due to the difference in personnel characters were successfully removed by utilising automatic indentation measurement system. In overall. the tester and the indentation measuring system were found to be eligible as a national standard of Brinell hardness.
브리넬 경도 표준 시험기 및 압입자국 자동 측정 장치의 장기 안정도 평가와 최적 시험조건에 관한 연구
황농문,방건웅,탁내형 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.1
Evaluation of long term stability of the Brinell standard hardness tester was carried out to secure its application as a national standard in Brinell hardness. Accuracy and repeatability in load application were tested through evaluating errors in hardness measurement of certified reference blocks. All of those requirements in KS as well as ISO specifications were satisfied by this standard hardness tester. In addition to this, long term stability test of automatic indentation measurement system was carried out. The scattering range was almost the same with its error range. To figure out an optimum test condition for better repeatability and long term stability, the effect of load variation, load application speed and time have been studied using orthogonal array experimental plan. It was found that the best combination is 30㎛/s of load application speed and 25 seconds of load application time.
방건웅(G . W . Bahng),탁내형(N . H . Tak),(T . Poizin) 한국열처리공학회 2001 熱處理工學會誌 Vol.14 No.6
N/A For the establishment of the world wide unified scales of the Rockwell hardness test with conical indenters, round robin test was carried from 1998 to 2000. The pilot laboratory was MPA-NRW and 12 laboratories from 11 countries participated in this RRT Rockwell hardness of 74 specially prepared blocks was measured for the scales of C, A, D, 45N, 30N, and 15N and the results were compared. It was found that the geometric form of indenter affects on the results very significantly and standardization in the measurement and evaluation of indenter should be established in short time for the reliable hardness measurement. KRISS showed good results in general for all of the ranges except 15N scale which showed relatively large difference compare to the mean value. It was concluded that poor control in loading velocity of the dash pot was the major reason.
방건웅(G. W. Bahng),탁내형(Nae Hyung Tak),봉하헌(Ha Heon Bong) 한국열처리공학회 2002 熱處理工學會誌 Vol.15 No.3
N/A 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.
방건웅(G . W . Bahng),탁내형(N . H . Tak) 한국열처리공학회 2001 熱處理工學會誌 Vol.14 No.5
N/A 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 report the results to KRISS. The result showed that quits 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.