• Title/Summary/Keyword: Wear prediction

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Real-time Tool Condition Monitoring for Machining Operations

  • Kim, Yon-Soo
    • IE interfaces
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    • v.7 no.3
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    • pp.155-168
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    • 1994
  • In computer integrated manufacturing environment, tool management plays an important role in controlling tool performance for machining operations. Knowledge of tool behavior during the cutting process and effective tool-behavior prediction contribute to controlling machine costs by avioding production delays and off-target parts due to tool failure. The purpose of this paper is to review and develop the tool condition monitoring scheme for drilling operation to assure a fast corrective response to minimize the damage if tool failures occur. If one desires to maximize system through-put and product quality as well as tooling resources, within an economic environment, real-time tool sensing system and information processing system can be coupled to provide the necessary information for the effective tool management. The example is demonstrated as to drilling operation when the aluminum composites are drilled with carbide-tipped HSS drill bits. The example above is limited to the situation that the tool failure mode of drill bits is wear.

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An Study on the Erosion Characteristics of Tube CN98 (CN98 포신의 마모특성 연구)

  • Kim, Jae-Kab
    • Journal of the Korea Institute of Military Science and Technology
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    • v.9 no.2 s.25
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    • pp.42-52
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    • 2006
  • Tube erosion can be defined as a phenomenon for an increment of bore diameter, a declination of accuracy and utility of tube by firing. This study introduces the characteristics of tube life for the 155 mm K9 SHP Using a tube history book with bore measurement data and firing data of standard charge, this study analyzed the EFC vs Tube life and EFC with heat transfer effect formula as a consideration of continuous firing vs tube life. The results were compared with Firing Table(FT 155-K9-1) after the analysis. Also, this study suggests that CN98 tube can be rifled as 1000 EFC through the severe condition with continuous firing.

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.

Integrated Model for Assessment of Risks in Rail Tracks under Various Operating Conditions

  • G. Chattopadhyay;V. Reddy;Larsson, P-O
    • International Journal of Reliability and Applications
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    • v.4 no.4
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    • pp.183-190
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    • 2003
  • Rail breaks and derailments can cause a huge loss to rail players due to loss of service, revenue, property or even life. Maintenance has huge impact on reliability and safety of railroads. It is important to identify factors behind rail degradation and their risks associated with rail breaks and derailments. Development of mathematical models is essential for prediction and prevention of risks due to rail and wheel set damages, rail breaks and derailments. This paper addresses identification of hazard modes, estimation of probability of those hazards under operating, curve and environmental condition, probability of detection of potential hazards before happening and severity of those hazards for informed strategic decisions. Emphasis is put on optimal maintenance and operational decisions. Real life data is used for illustration.

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Thermal Property Analysis of 40 mm Long Hollow Cylinders Though Measurements and Analysis of Transient Temperatures (온도 측정과 분석을 통한 40 mm 장축공동실린더의 열적특성 고찰)

  • Shin Nae-Ho;Chung Dong-Yoon;Oh Myoung-Ho;Yoo Sam-Hyeon;Nam Seok-Ryun
    • Tribology and Lubricants
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    • v.22 no.4
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    • pp.190-195
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    • 2006
  • A simple and effective analysis method is presented for gaining a complete transient temperatures on the internal and external surfaces of a 40 mm gun tube subjected to a series of rapid firings. Two series of temperature data for both Hs and As were measured by using two rapid response k-type surface thermocouples near the firing origin and the muzzle. With other available temperature data, patterns of temperature variations of the gun tube as a function of time variable were driven through complete evaluations of the data. It is found that overall temperature gradients which increase exponentially toward saturation temperature, actually consist of a series of linear temperature gradients corresponding to the firing sequences. Under the similar firing sequences, patterns of temperature variations fur both the surface temperatures near the chamber and those near the muzzle were found to have linear temperature gradients with different values and the same response frequencies, i.e. they had peaks and lows in temperatures at the same time. The resultant complete temperature data can be used as the fundamental bases for analysis of thermoelastic properties of the materials such as thermal strain and stress, and f3r the prediction of cannon tube life-time through calculation of wear rate.

Determination of Rock Abrasiveness using Cerchar Abrasiveness Test (세르샤 마모시험을 통한 암석의 마모도 측정에 관한 연구)

  • Lee, Su-Deuk;Jung, Ho-Young;Jeon, Seok-Won
    • Tunnel and Underground Space
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    • v.22 no.4
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    • pp.284-295
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    • 2012
  • Abrasiveness of rock plays an important role on the wear of rock cutting tools. In this study, Cerchar abrasiveness tests were carried out to assess the abrasiveness of 19 different Korean rocks. Cerchar abrasiveness test is widely used to assess the abrasiveness of rock because of its simplicity and inexpensive cost. This study examines the relationship between Cerchar Abrasiveness Index (CAI) and mechanical properties (uniaxial compressive strength, Brazilian tensile strength, Young's modulus, Poisson's ratio, porosity, shore hardness of rock), and the effect of quartz content, equivalent quartz content, which was obtained from XRD analysis. As a result of test, CAI was more influenced by petrographical properties than by the bonding strength of the matrix material of rock. CAI prediction model which consisted of UCS and EQC was proposed. CAI decreased linearly with the hardness of the steel pin. Numerical analysis was performed using Autodyn-3D for simulating the Cerchar abrasiveness test. In the simulations, most of pin wear occurred during the initial scratching distance, and CAI increased with the increase of normal loading.

Effects of Increasing Ambient Temperatures on the Static Load Performance and Surface Coating of a Gas Foil Thrust Bearing (외기 온도 증가가 가스 포일 스러스트 베어링의 하중지지 성능과 표면 코팅에 미치는 영향)

  • Hyunwoo Cho;Youngwoo Kim;Yongbum Kwon;Tae Ho Kim
    • Tribology and Lubricants
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    • v.40 no.3
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    • pp.103-110
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    • 2024
  • Gas foil thrust bearings (GFTBs) are oil-free self-acting hydrodynamic bearings that support axial loads with a low friction during airborne operation. They need solid lubricants to reduce dry-friction between the runner and top foil and minimize local wears on their surfaces during start-up and shutdown processes. In this study, we evaluate the lift-off speeds and load capacity performance of a GFTB with Polytetrafluoroethylene (PTFE) surface coating by measuring drag torques during a series of experimental tests at increasing ambient temperatures of 25, 75 and 110℃. An electric heat gun provides hot air to the test GFTB operating in the closed booth to increase the ambient temperature. Test results show that the increasing ambient temperature delays the lift-off speed and decreases the load capacity of the test GFTB. An early developed prediction tool well predicts the measured drag torques at 60 krpm. After all tests, post inspections of the surface coating of the top foil are conducted. Scanning electron microscope (SEM) images imply that abrasive wear and oxidation wear are dominant during the tests at 25℃ and 110℃, respectively. A quantitative energy dispersive spectroscopy (EDS) microanalysis reveals that the weight percentages of carbon, oxygen, and nitrogen decrease, while that of fluorine increases significantly during the highest-temperature tests. The study demonstrates that the increasing ambient temperature noticeably deteriorates the static performances and degrades the surface coating of the test GFTB.

Determination and Verification of Flow Stress of Low-alloy Steel Using Cutting Test (절삭실험을 이용한 저합금강의 유동응력 결정 및 검증)

  • Ahn, Kwang-Woo;Kim, Dong-Hoo;Kim, Tae-Ho;Jeon, Eon-Chan
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.13 no.5
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    • pp.50-56
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    • 2014
  • A technique based on the finite element method (FEM) is used in the simulation of metal cutting process. This offers the advantages of the prediction of the cutting force, the stresses, the temperature, the tool wear, and optimization of the cutting condition, the tool shape and the residual stress of the surface. However, the accuracy and reliability of prediction depend on the flow stress of the workpiece. There are various models which describe the relationship between the flow stress and the strain. The Johnson-Cook model is a well-known material model capable of doing this. Low-alloy steel is developed for a dry storage container for used nuclear fuel. Related to this, a process analysis of the plastic machining capability is necessary. For a plastic processing analysis of machining or forging, there are five parameters that must be input into the Johnson-Cook model in this paper. These are (1) the determination of the strain-hardening modulus and the strain hardening exponent through a room-temperature tensile test, (2) the determination of the thermal softening exponent through a high-temperature tensile test, (3) the determination of the cutting forces through an orthogonal cutting test at various cutting speeds, (4) the determination of the strain-rate hardening modulus comparing the orthogonal cutting test results with FEM results. (5) Finally, to validate the Johnson-Cook material parameters, a comparison of the room-temperature tensile test result with a quasi-static simulation using LS-Dyna is necessary.

Prediction of Surface Crack Growth Considering the Wheel Load Increment Due to Rail Defect (레일손상에 의한 윤중증가를 고려한 표면균열 성장예측)

  • Jun, Hyun-Kyu;Choi, Jin-Yu;Na, Sung-Hoon;You, Won-Hee
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.9
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    • pp.1078-1085
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    • 2011
  • Prediction of a minimum crack size for growth, which is defined as a crack size that grows fast enough to keep ahead of its removal by contact wear and periodic grinding, is the most demanding work to prevent rail from fatigue failure and develop cost effective railway maintenance strategy In this study, we investigated the wheel load increment due to a rail defect during a train ran over it, and its effect on the minimum crack size for growth. For this purpose, we developed simulation software based on the Fletcher and Kapoor's "2.5D" model and measured wheel load increment during a train passed over a defect. A maximum contact pressure and contact patch size were calculated by 3D FEM and crack growth analyses were performed by varying two of dominant contact contributors; surface friction coefficient(0.1, 0.2, 0.3 and 0.4) and crack aspect ratio. The minimum crack sizes for growth were calculated from 0.29 to 1.44mm depending on the contact conditions. They were decreasing with increasing surface friction coefficient and decreasing with crack aspect ratio(a/b).

Improvement Plan of Excavation Performance Based on Shield TBM Performance Prediction Models and Field Data (쉴드 TBM 성능예측모델과 굴진자료 분석을 통한 굴진성능 개선방안)

  • Jung, Hyuksang;Kang, Hyoungnam;Choi, Jungmyung;Chun, Byungsik
    • Journal of the Korean GEO-environmental Society
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    • v.11 no.2
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    • pp.43-52
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    • 2010
  • Shield method is the tunnel boring method that propels a steel cylinder in the ground and excavates tunnels at once. After Marc Isambard Brunel started using the method for the Thames Riverbed Tunnel excavation in London, many kinds of TBM (Tunnel Boring Machine) developed and applied for the construction of road, railway, electricity channel, pipeline, etc. In comparison with NATM concept that allows to observe ground condition and copes with difficulty. The machine selected before starting construction is not able to be changed during construction in shield TBM. Therefore the machine should be designed based on the ground survey result and experiment, so that the tunnel might be excavated effectively by controlling penetration speed, excavation depth and cutter head speed according to the ground condition change. This research was conducted to estimate penetration depth, excavate speed, wear of disc cutter on Boondang Railway of the Han Riverbed Tunnel ground condition by TBM performance prediction models such as NTNU, $Q_{TBM}$, Total Hardness, KICT-SNU and compare the estimated value with the field data. The estimation method is also used to analyze the reason of poor excavation efficiency at south bound tunnel.