• Title, Summary, Keyword: Indentation

Search Result 767, Processing Time 0.055 seconds

Considerations on an Oriental Medical Doctor like Indentation System (한의사 맥진 가압력 재현에 대한 고찰)

  • Lee, Jeon;Woo, Young-Jae;Jeon, Young-Ju;Lee, Yu-Jung;Ryu, Hyun-Hee;Kim, Jong-Yeol
    • Korean Journal of Oriental Medicine
    • /
    • v.14 no.3
    • /
    • pp.113-119
    • /
    • 2008
  • In pulse diagnosis, the indentation pressure is one of the most important factors as well as the change of pulse shape and the distribution of pressure via time. But, on the oriental medical doctor's indentation pressure control, the understandings of the neurophysiological meanings and mechanisms have been lacked. So, in this paper, we considered on these issues and then proposed a proper system which can imitate the OMD's indentation pressure control mechanisms. As a result, both tactile information and kinesthetic information were found to be essential to the indentation pressure control so that a system, which can measure both the physical indent pressure and the displacement of an indentation arm, has been proposed. With this proposed system, while the indentation was being controlled through the moving step number of the step motor, the physical indentation pres sure and displacement of the indentation arm were measured. From these measured data, the relationships between the moving step number and both physical indentation pressure and displacement were revealed to have linear characteristics in early phase and to have nonlinear characteristics in latter phase. Additionally, three types of graph were generated whose X axis means the moving step number, the physical indentation pressure and the displacement respectively and Y axis means the pulse pressure. By comparing these graphs, we come to conclude that different concepts on indentation pressure control cause different diagnostic results on floating/sinking degrees for the same subject. Consequently, an indentation system for the pulse diagnosis should be able to provide both the tactile information and kinesthetic information, that is, the physical indentation pressure and the displacement of the indentation arm. In future, the proposed system should be optimized to the pulse diagnosis environment and how to combine the both information for more reliable diagnosis should be studied.

  • PDF

Performance analysis of spherical indentation process during loading and unloading - a contact mechanics approach

  • Gandhi, V.C. Sathish;Kumaravelan, R.;Ramesh, S.
    • Structural Engineering and Mechanics
    • /
    • v.52 no.3
    • /
    • pp.469-483
    • /
    • 2014
  • In an indentation approach, the smooth rigid spherical ball penetrated into a deformable flat is considered for the study based on contact mechanics approach. The elastic-plastic frictionless spherical indentation analysis has been under taken in the finite element analysis using "ABAQUS" and experimental study. The spherical indentation has been studied for the materials like steel, aluminium, copper and brass with an identical spherical indenter for diverse indentation depths. The springback analysis is executed for studying the actual indentation depth after the indenter is unloaded. In the springback simulation, the material recovers its elastic deformation after the indenter is unloaded. The residual diameter and depth of an indentation for various materials are measured and compared with simulation results. It shows a good agreement between the simulation and an experimental studies.

Evaluation of Flow Stress using Geometric Conditions of Ball Indentation Tests (볼 압입 시험의 기하학적 조건과 유동 응력 곡선의 관계에 관한 연구)

  • 이병섭;이호진;이봉상
    • Transactions of Materials Processing
    • /
    • v.12 no.4
    • /
    • pp.328-333
    • /
    • 2003
  • Ball indentation tests have been used to estimate the mechanical properties of materials by several investigators. In this study, load-depth curves from ball indentation tests were analyzed using the geometric conditions of the contact between ball and specimen. A series of numerical calculations and experimental results showed that the contact load-depth curves could be simplified by linear functions. Once we obtained the contact indentation depth from linearizing the experimental indentation curves, the estimation process of the flow properties became straight-forward and the scatter of results could be drastically reduced.

Enhanced Spherical Indentation Techniques for Property Evaluation (향상된 구형 압입 물성평가법)

  • Lee, Hyung-Yil;Lee, Jin-Haeng
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.31 no.4
    • /
    • pp.461-471
    • /
    • 2007
  • In this work, indentation theory of Lee $et al.^{(1)}$ for 6% indentation of indenter diameter is extended to an indentation theory for 20% indentation. For shallow indentation, the effect of friction on load-depth curve is negligible, but different materials can show nearly identical load-depth curves. On the basis of this observation, a new numerical approach to deep indentation techniques is proposed by examining the finite element solutions. With this new approach, from the load-depth curve, we obtain stress-strain curve and the values of Young's modulus, yield strength and strain-hardening exponent with an average error of less than 3%.

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
    • /
    • v.21 no.3
    • /
    • pp.376-381
    • /
    • 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.

Derivation of work-hardening exponent through indentation contact detph analysis (압입접촉깊이 분석을 통한 가공경화지수의 유도)

  • Jeon, Eun-Chae;Ahn, Jeong-Hoon;Choi, Yeol;Kwon, Dong-Il
    • Proceedings of the KSME Conference
    • /
    • /
    • pp.523-528
    • /
    • 2001
  • In this study we tried to determine the work-hardening exponent using continuous indentation test. Work-hardening exponent, which was determined by Hollomon equation, in tensile test, is an important parameter to determine plastic deformation and brittle/ductile property of materials. For using Hollomon equation, true stress and true strain were defined by indentation depth and indentation load. Using them the new equation, which is constituted by indentation depth, indentation load and work-hardening exponent, was induced. Indentation depth was calibrated because of elastic deflection and pile-up/sink-in phenomena. Work-hardening exponents of various steels derived by it showed good agreement to the results of tensile tests. In addition to experiments, FEM simulation was accomplished to investigate changes of real contact depth with materials properties changes. Through this simulation it is concluded that the real contact depth is changed by Y/E value which affect the early stage of indentation, and work-hardening exponent which the latter stage.

  • PDF

Analytical Approaches of Surface-Local Deformations for the Measurement of Indentation Hardness (압입경도 측정을 위한 표면변형 분석기법 비교)

  • Lee, Yun-Hee;Kim, Kuk-Hwan;Nahm, Seung-Hoon;Kwon, Dongil
    • Korean Journal of Metals and Materials
    • /
    • v.47 no.7
    • /
    • pp.416-422
    • /
    • 2009
  • Approaches for analyzing indentation hardness are still controversial, although the instrumented indentation technique has been generalized as one powerful method that can record surface deformation behaviors. Material pile-ups around the indenter/surface contact region make the conventional Oliver and Pharr's analysis on the instrumented indentation curve inaccurate. Thus, in order to prove the validity of the hardness analyses, five approaches were applied to the experimental data obtained from fused quartz and (100) monocrystalline tungsten specimens; an elastic recovery analysis on instrumented indentation curves, three indentation work analyses on the unit plastic volume, and a differentiation analysis on remnant indentation morphologies were tried. Five kinds of indentation hardness overlapped on one result plot showed the validity of each analysis. The modified indentation work approach based on a new definition of plastic volume showed consistent results with those from the Oliver-Pharr's and image differentiation methods. In the case of pile-up accompanying deformation, the Oliver-Pharr's and image differentiation methods showed the upper and lower limits of indentation hardness, respectively.

Influence of Indenter Tip Geometry and Poisson's Ratio on Load-Displacement Curve in Instrumented Indentation Test (계장화 압입시험의 하중-변위 곡선에 미치는 선단 형상 및 푸아송비의 영향)

  • Lee, Jin Haeng
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.38 no.9
    • /
    • pp.943-951
    • /
    • 2014
  • The tip geometries of the pyramidal and conical indenters used for micro/nano-indentation tests are not sharp. They are inevitably rounded because of their manufacturability and wear. In many indentation studies, the tip geometries of the pyramidal indenters are simply assumed to be spherical, and the theoretical solution for spherical indentation is simply applied to the geometry at a shallow indentation depth. This assumption, however, has two problems. First, the accuracy of the theoretical solution depends on the material properties and indenter shape. Second, the actual shapes of pyramidal indenter tips are not perfectly spherical. Hence, we consider the effects of these two problems on indentation tests via finite element analysis. We first show the relationship between the Poisson's ratio and load-displacement curve for spherical indentation, and suggest improved solutions. Then, using a possible geometry for a Berkovich indenter tip, we analyze the characteristics of the load-displacement curve with respect to the indentation depth.

Crack Growth Retardation Effect and Metallographic Observation of Aluminum Alloy Plate with Pre-Indentation (예비압입에 의한 알루미늄 합금 판재의 균열성장 지연효과 및 금속조직 변화)

  • 황정선;조환기;윤용인
    • Journal of the Korea Institute of Military Science and Technology
    • /
    • v.6 no.4
    • /
    • pp.73-79
    • /
    • 2003
  • Fatigue test is conducted to see the effect of pre-indentation on the fatigue crack retardation of Al5052-H18 plate. Metallographic observation is introduced to deduce the relationship between fatigue crack retardation and fracture appearance with indentation. The grain size of the specimen becomes smaller with the increase of indentation force and the plastic zone is formed with the decrease of grain size. The fatigue striations are appeared densely as the Indentation force becomes higher. Metallographic observation and fatigue test results show that the indentation force has the limited value in improving fatigue crack retardation. Important point to retard the fatigue crack growth is that the crack growth path should pass through the indented area.

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
    • /
    • /
    • pp.191-194
    • /
    • 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.

  • PDF