• 제목/요약/키워드: Indentation Depth

검색결과 127건 처리시간 0.029초

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

  • 이병섭;이호진;이봉상
    • 소성∙가공
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    • 제12권4호
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    • pp.328-333
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    • 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.

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
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    • 제52권3호
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    • pp.469-483
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    • 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.

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

  • 전은채;안정훈;최열;권동일
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집A
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    • pp.523-528
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    • 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.

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

  • 이병섭;이호진;이봉상
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2003년도 춘계학술대회논문집
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    • pp.291-294
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    • 2003
  • Ball indentation tests have been used to estimate the mechanical properties of materials by some investigators. In this study, load-depth curves from ball indentation tests have been analysed using the geometric conditions of ball indentation. Series of numerical calculations and experimental results showed that those curves could be simplified by linear functions. After linearizing the indentation curves, the estimation process of the flow properties became straight forward and the scatter of results could be drastically reduced.

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

  • 이형일;이진행
    • 대한기계학회논문집A
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    • 제31권4호
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    • pp.461-471
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    • 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%.

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

  • 전은채;안정훈;권동일
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 추계학술대회논문집A
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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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연속압입시험법을 이용한 원전구조물의 잔류응력 평가를 위한 접촉깊이의 보정 (Calibration of Contact Depth for Evaluating Residual Stress using Instrumented Indentation Testing)

  • 김영천;강승균;안희준;김광호;권동일
    • 한국압력기기공학회 논문집
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    • 제7권1호
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    • pp.41-47
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    • 2011
  • Residual stress is the key parameter for reliability and lifetime assessment because it can reduce the fatigue strength and fracture properties of industrial structures. Recently, instrumented indentation testing (IIT) has been widely used for evaluating it, since it does not need specific specimen and time-consuming procedure. However, conventional Oliver-Pharr method, which is used for calibrating contact depth to analyze indentation load-depth curve, cannot estimate plastic pile-up between indenter and surface of specimen. Here, we introduce f parameter which is the ratio of contact depth and maximum depth, to consider pile-up height. And, its application for evaluating residual stress of weldment is introduced.

점용접 시 압흔 깊이 감소를 위한 최적 용접조건 선정에 관한 연구 (A Study on the Optimum Welding Conditions for Reducing the Depth of Indentation of Surface in Spot Welding)

  • 서승일;이재근;장상길;차병우
    • Journal of Welding and Joining
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    • 제14권2호
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    • pp.57-64
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    • 1996
  • In this paper, authors are trying to find optimum spot weldig conditions to minimize indentation of the plate surface which is crucial to quality of stainless rolling stocks. At first, to derive a simple equation to estimate the depth of indentation, a simplified one-dimensional bar model is proposed and validity of the model is confirmed by experiments. And also, to find proper welding conditions giving satisfied tensile strength of the welded joint, a simple formula is derived referring to the standard spot welding conditions by AWS. Optimization problem is formulated to find welding conditions such as welding current, time and applied force which give minimum indentation and proper tensile strength of joint, and solutions are found out. According to the results, the depth of indentation can be expressed by applied electrode froces and it can be shown that an optimum applied force exists.

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인장 및 압축 등방 잔류응력 측정을 위한 누프 압입시험의 응력환산계수 결정 (Determination of Knoop Indentation Stress Conversion Factors for Measuring Equibiaxial Residual Stress)

  • 정민재;김영천
    • Corrosion Science and Technology
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    • 제20권6호
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    • pp.484-490
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    • 2021
  • Instrumented indentation testing has been widely used for residual stress measurement. The Knoop indentation is mainly selected for determining anisotropic mechanical properties and non-equibiaxial residual stress. However, the measurement of equibiaxial stress state and compressive residual stress on a specimen surface using Knoop indentation is neither fully comprehended nor unavailable. In this study, we investigated stress conversion factors for measuring Knoop indentation on equibiaxial stress state through indentation depth using finite element analysis. Knoop indentation was conducted for specimens to determine tensile and compressive equibiaxial residual stress. Both were found to be increased proportionally according to indentation depth. The stress field beneath the indenter during each indentation test was also analyzed. Compressive residual stress suppressed the in-plane expansion of stress field during indentation. In contrast, stress fields beneath the indenter developed diagonally downward for tensile residual stress. Furthermore, differences between trends of stress fields at long and short axes of Knoop indenter were observed due to difference in indenting angles and the projected area of plastic zone that was exposed to residual stress.

소구경 전열관 내의 열전달촉진 형상변화에 따른 열전달 및 압력강하 특성에 관한 실험적 연구 (Experimental Study on the Characteristics of the Heat Transfer and the Pressure Drop inside the Small Diameter Tube with the Heat Transfer Enhancing Geometry)

  • 박찬우;진성민;정종수
    • 설비공학논문집
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    • 제18권4호
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    • pp.297-303
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    • 2006
  • Friction and heat transfer coefficients were measured inside the corrugated tube using water as the working fluid. The test is performed for 16 tubes which outer diameter of tubes are 12.7 mm. These specifications are 4 indentation depths and 4 indentation pitches, respectively. The range of the water velocity inside the tube is from 0.5 to 3.0 m/s (8,500