• Title/Summary/Keyword: Continuous indentation test technique

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Derivation of work-hardening exponent using continuous indentation technique (연속압입시험법을 이용한 가공경화지수의 유도)

  • Jeon, Eun-Chae;Ahn, Jeong-Hoon;Kwon, Dong-Il
    • Proceedings of the KSME Conference
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    • 2000.11a
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    • pp.256-261
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    • 2000
  • In this study, we derived work-hardening exponent using continuous indentation test technique. Continuous indentation test technique is a powerful method to evaluate mechanical properties, such as hardness, modulus, ${\sigma}-{\varepsilon}$ curves and etc. It has many merits conventional indentation test has. The relationship between true stress and mean contact pressure and between strain and indentation depth were derived. While the indenter pushes the materials, the region around the indenter is deflected elastically. It is called elastic deflection. And pile-up phenomenon related to plastic deformation around the indenter increased the contact depth, and sink-in phenomenon decreases. So we calibrated contact depth change by considering elastic deflection and pile-up/sink-in. Using calibrated contact depth we redefined the relationship between true stress and mean contact pressure and between strain and contact depth. Through these relationship we could derive work-hardening exponent by analyzing load-depth curves. And it showed good agreement with tensile test results.

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Application of Continuous Indentation Technique for Reliability Evaluation in Power Plant Facilities (발전설비 주요배관 신뢰도 확보를 위한 연속압입시험 적용)

  • Park, Sang-Ki;Ahn, Yeon-Shik;Jung, Gye-Jo;Cho, Yong-Sang;Choi, Yeol
    • Journal of the Korean Society for Nondestructive Testing
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    • v.24 no.2
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    • pp.158-162
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    • 2004
  • Reliability of welded structures in power plant facilities is very important, and their reliability evaluation requires exact materials properties. But, the conventional PQR (Procedure Qualification Record) can hardly reflect the real material properties in the field because the test is only done on specimens with simulated welding. Therefore, a continuous indentation technique is proposed in this study for simple and non-destructive testing of in-field structures. This test measures the indentation load-depth curve during indentation and analyzes the mechanical properties such as the yield strength, tensile strength and work hardening index. This technique has been applied to evaluate the tensile properties of the weldment in the main steam pipe and hot reheater pipe in power plants under construction and in operation.

Determination of New Parameter for Materials Degradation Using Continuous Indentation Testing Technique (연속압입 시험기법을 이용한 석유화학설비 경년손상의 새로운 평가변수 고찰)

  • Jang, Jae-Il;Choi, Yeol;Son, Dongil;Lee, Yun-Hee;Kwon, Dongil;Kim, Jeoung-Tae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.5
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    • pp.881-889
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    • 2002
  • Newly developed continuous indentation technique has made nondestructive assessment of tensile properties possible. The present study was undertaken to determine new parameters for indicating time-dependent material degradation of petro-chemical plant. Continuous indentation tests were performed for Cr-Ni steel and Cr-Mo steel which are widely used as facilities of petro-chemical plant. From the results, it was found that yield strength and tensile strength cannot be used as general degradation parameters because the changes in the strengths with aging time didn't show any tendency. On the other hand, work hardening exponent and yield ratio showed consistent tendency with increasing aging time. Therefore, nam attention of this work was paid on them as new degradation parameters, and the in-field applicability of the parameters was evaluated and discussed.

Evaluation of Flow Properties of Steel Using Advanced Indentation System (비파괴적 연속압입시험 기법을 응용한 구조용 강의 소성 물성 평가)

  • Jang, J.I.;Son, D.I.;Choi, Y.;Park, S.C.;Kwon, D.I.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2002.05a
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    • pp.191-194
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    • 2002
  • The tensile properties of materials can be obtained just in accordance with conventional tensile testing methods which are described in several standards. However, the standard testing methods cannot be applicable due to the destructive testing procedure and specimen size requirement for some cases including on-service facility materials. Therefore, simple, non-destructive and advanced indentation technique was proposed. This test measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation and fracture. In this paper, the research trend of non-destructive evaluation of tensile properties using advanced indentation system and its application fields are reviewed and discussed.

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Evaluation of Reliability for Welded thick steel joint (후판 강용접부의 신뢰성 평가)

  • 최원두;이영호;길두송;박상기
    • Proceedings of the KWS Conference
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    • 2004.05a
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    • pp.327-329
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    • 2004
  • Reliability evaluation of the welded structure for industrial structures/facilities such as power plant and petro-chemical refinery facilities is very important, and especially the reliability diagnosis of the structure is based on the exact evaluation of materials properties. But, the conventional Pre-Qualification test had the difficulty of evaluating the real material properties in the field because the test was made on the specimen with the simulated welding for the in-field welding condition. Therefore, a continuous indentation technique was proposed for simple and non-destructive testing of in-field structures and for selective testing of local range such as heat affected zone and weldment.

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