• Title, Summary, Keyword: Deflection

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A Study on Micro Tool Deflection in Micro Endmilling Process (마이크로 엔드밀링 시 공구 변형에 관한 연구)

  • Kim, G.H.;Yoon, G.S.;Heo, Y.M.;Jung, W.C.;Cho, M.W.
    • Transactions of Materials Processing
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    • v.15 no.9
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    • pp.654-659
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    • 2006
  • In this paper, the real shapes of micro tool deflection were observed. In micro endmilling process, micro tool deflection generates very serious problems in contrast to macro tool deflection. For analyzing the micro tool deflection, the trend of micro tool deflection was observed using real captured images in this paper. To get the real images of micro tool deflection, micro slot cutting processes were executed under cutting volume using micro endmill($Dia.\;200{\mu}m$) and real images of tool deflection were obtained during cutting processing by high-speed camera. Finally, the extent of tool deflection was calculated by the deflection angle according to cutting volume.

The Mechanical Behavior and the Anatomical Changes of Wood due to Variation of Deflection Rates

  • Kang, Chun Won
    • Journal of the Korean Wood Science and Technology
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    • v.33 no.5
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    • pp.7-12
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    • 2005
  • The objective of this study is to estimate the mechanical behavior in bending and the anatomical changes of wood under several deflection rates. Sample specimens of water-saturated Japanese cedar (Cryptomeria japonica) were stressed to rupture under several deflection rates. Mechanical properties of wood such as modulus of elasticity, modulus of rupture and stress at proportional limit, and anatomical changes affected by deflection rates were estimated. Microscopic observations on compression side of the test specimens when the specimen was loaded to rupture were carried out by the SEM (scanning electron microscopy). The results are summarized as follows: 1. The mechanical properties of wood were affected by variations of the deflection rates. The modulus of elasticity (MOE), modulus of rupture (MOR) and stress at proportional limit were in proportion to the logarithm of deflection rates. 2. The deflection of wood at rupture in bending increased as deflection rates decreased. 3. The variations of the microscopic deformations of sample specimens were closely related to the deflection of wood at rupture. In case of largely deflected wood by maximum bending load, severe and abundant microscopic deformations were observed.

The Influence and Treatment Method of Extraneous Deformation & Unstability on the Flexural Toughness of FRC (FRC의 휨인성 평가시 외부변형과 불안정성의 영향 및 처리방안)

  • Kim, Kyoung-Soo;Kim, Nam-Wook;Lim, Jeong-Hwan;Bae, Ju-Seong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.6 no.3
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    • pp.119-128
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    • 2002
  • This study discusses the issues related to the accuracy of deflection measurement and unstable energy in the testing of FRC. Some deflection methods may include large extraneous deformations. A faulty load-deflection curve will be obtained if an unstable deflection measuring system is used, and inaccurate toughness evaluation can result from this faulty curve. Some load-deflection curve of FRC may be attributed to unstable region of the load-deflection curve. If the unstable region is not correctly evaluated toughness indices from the curve would inappropriately represent true indices. In this paper, the discussion will focus on the effects of the deflection measuring system both on the measurement of the load-deflection response of FRC and the evaluation of FRC toughness and the effects of the unstable region and the management method of unstable region on toughness evaluation of FRC. It is observed that ASTM toughness indices which is based on measured deflection at first cracking is influenced significantly by extraneous deformation of deflection measurement. Extraneous deformation in deflection measurement, however result in negligible errors in toughness evaluation if JSCE and JCI definitions are used.

Study of the thermal deflection error and the deflection error induced by the cutting force (절삭공구의 열변형 오차 및 절삭력 변형 오차에 관한 연구)

  • Oh, Myung-Seok;Yoon, In-Jun;Baek, Dae-Kyun
    • Journal of the Korean Society of Industry Convergence
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    • v.5 no.4
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    • pp.373-378
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    • 2002
  • This paper presents a method to predict tool deflection induced by the thermal distribution and the cutting force using FEM in milling operation. The thermal distribution of cutting tool was predicted using FEM after measuring the temperature of the end of tool and of the tool holder. The thermal deflection of cutting tool was predicted using FEM as well. The tool deflection induced by the cutting force was analyzed with the solid model of cutting tool. An end mill tool caused most of tool deflection comparing to tool holder. Most of thermal deflection came from Z-direction and most of tool deflection induced by the cutting force came from X and Y direction. Precision cutting will be accomplished when tool locations are generated considering the thermal deflection of cutting tool and the tool deflection induced by the cutting force in CAD/CAM.

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Deflection Characteristics of the Rice Stalk in Harvesting Operation by Combine for Multi-crops (보통형 콤바인의 수확작업에 관계하는 벼줄기의 굽힘특성)

  • 김영근;홍종태;최중섭
    • Journal of Biosystems Engineering
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    • v.28 no.6
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    • pp.485-490
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    • 2003
  • Flexural rigidity(EI) and deflection characteristics of rice stalks were studied to investigate the mechanical interaction between a rice stalk and a combine reel in harvesting. Deflection of a rice stalk caused by reel operation is so large that conventional equation of small deflection fer elastic beam cannot be applied to the study of deflection characteristics. Therefore, an equation of large deflection for elastic beam was introduced in this study. Feasibility of this equation was examined by comparing theoretical calculation with the measured results for piano wire, and by the relationship between deflection and load acting on a rice stalk which was presumed by this equation. Results showed that the large deflection equation could predict the measurement data quite well. From this research, the following results were obtained. 1. Flexural rigidity(EI) calculated from the equation of large deflection was 4.0${\times}$l0$^4$N$.$$\textrm{mm}^2$(diameter 1.4mm, deflection 300mm) while the actual EI value of a piano wire(diameter 1.4mm) was 3.9${\times}$10$^4$N$.$$\textrm{mm}^2$. 2. The relationship between deflection and load acting on a rice stalk could be presumed by the large deflection equation. Flexural rigidity values of tested rice stalks calculated from the equation of large deflection were 1.6∼2.4${\times}$ l0$^4$N$.$$\textrm{mm}^2$(Hwa sung), 2.7∼3.5${\times}$ l0$^4$N$.$$\textrm{mm}^2$(Il pum) and 1.7∼2.4${\times}$ l0$^4$N$.$$\textrm{mm}^2$(Damakum)

Influence of Extraneous Deformation on the Toughness of Fiber Reinforced Concrete (외부변형이 섬유보강콘크리트의 인성에 미치는 영향)

  • Kim, Kyoung-Soo;Ko, Young-Zoo;Lim, Jeong-Whan;Bae, Ju-Seong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.4 no.1
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    • pp.111-120
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    • 2000
  • This study discusses the issues related to the accuracy of deflection measurement in the testing of FRC. Some deflection methods may include large extraneous deformations. such as local crushing at the loading points, elastic and inelastic deformations of the loading fixture, etc. A faulty load-deflection curve will be obtained if an unstable deflection measuring system is used, and incorrect toughness evaluation can be reached on the basis of this faulty curve. In this paper, the discussion will focus on the effects of the deflection measuring system on both the measurement of the load-deflection response of FRC and the evaluation of FRC toughness. It is observed that ASTM toughness indices which is based on measuring deflection at first cracking is influenced significantly by extraneous deformation in deflection measurement. But extraneous deformation in deflection measurement result in negligible errors in toughness evaluation using JSCE and JCI definition. However, in order to evaluate toughness accuracy, it is desirable to use net load-deflection curve eliminated extraneous deformation.

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The Flexibility Estimation of Alignment for Propulsion Shaft System using the Approximated Hull Deflection Curve (선체 변형 근사곡선을 이용한 추진축계 정렬의 유연성 평가)

  • Sun, Jin-Suk;Lee, Yong-Jin;Kim, Ue-Kan
    • Journal of the Korean Society of Marine Engineering
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    • v.33 no.1
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    • pp.28-36
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    • 2009
  • In this paper, based on the measured data of hull deflection, an approximated hull deflection curve is drawn using reverse analyzed hull deflection data and the estimation method for flexibility analysis of shaft alignment is proposed by use of the approximate hull deflection curve. Generally an offset value of after stern tube bearing is a datum point with an fore stern tube bearing however the shaft alignment has a tendency which is able to get higher flexibility if the shafting system has the deflection value from after stern tube bearing as reference to bottom direction according to results of on this study. By applying this result of study, the shaft alignment for next similar ships will be able to estimate how to follow the hull deflection and how to be influenced by hull deflection at shaft alignment analysis state using the approximated hull deflection curve.

Closed Form Expression of Cutting Forces and Tool Deflection in End Milling Using Fourier Series (푸리에 급수를 이용한 엔드밀링 절삭력 및 공구변형 표현)

  • Ryu, Shi-Hyoung
    • Journal of the Korean Society for Precision Engineering
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    • v.23 no.9
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    • pp.76-83
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    • 2006
  • Machining accuracy is closely related with tool deflection induced by cutting forces. In this research, cutting forces and tool deflection in end milling are expressed as a closed form of tool rotational angle and cutting conditions. The discrete cutting fores caused by periodic tool entry and exit are represented as a continuous function using the Fourier series expansion. Tool deflection is predicted by direct integration of the distributed loads on cutting edges. Cutting conditions, tool geometry, run-outs and the stiffness of tool clamping part are considered together far cutting forces and tool deflection estimation. Compared with numerical methods, the presented method has advantages in prediction time reduction and the effects of feeding and run-outs on cutting forces and tool deflection can be analyzed quantitatively. This research can be effectively used in real time machining error estimation and cutting condition selection for error minimization since the form accuracy is easily predicted from tool deflection curve.

The Practice of Bending Deflection using Non-destructive MOE of Glulam (비파괴 탄성계수를 이용한 집성재의 휨변형 예측)

  • Park, Jun-Chul;Hong, Soon-Il
    • Journal of the Korean Wood Science and Technology
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    • v.37 no.1
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    • pp.48-55
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    • 2009
  • In the glulam beam deflection it is necessary to check the reliability of theory formula, because of wood anisotropy and wood qualities (knot, slop of grain). In this experiment, when bending stress occurred on glulam, practice deflection of glulam measuring with AICON DPA-Pro 3D system were compared with prediction deflection calculated as substituting MOE through non-destructive testing and static MOE through bending test in differential equation of deflection curve. MOE using ultrasonic wave tester of laminae, MOE using natural frequencies of longitudinal vibrations ($E_{cu}$, $E_{cf}$), MOE using ultrasonic wave tester of glulam ($E_{gu}$) and MOE using natural frequencies of longitudinal vibrations ($E_{gf}$) were substituted in this experiment. When practice deflection measured by 3D system was compared with prediction deflection calculated with differential equation of deflection curve, within proportional limit the ratio of practice deflection and prediction deflection was similar as 1.12 and 1.14, respectively. Deflection using ultrasonic wave tester was 0.89 and 0.95, Deflection using natural frequencies of longitudinal vibrations was 1.07 and 1.10. The results showed that prediction deflection calculated by substituting using non-destructive MOE of glulam having anisotropy in differential equation of deflection curve was agreed well with practice deflection.

A Study for Improvement the Subsurface Cavity Management Grade Using Deflection Ratio (처짐비를 활용한 도로함몰 관리등급 개선 연구)

  • Kim, Kyung soo;Choi, Junseong;Yoon, Jin-sung
    • International Journal of Highway Engineering
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    • v.20 no.6
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    • pp.117-126
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    • 2018
  • PURPOSES : The purpose of this study is to evaluate and improve the potential risk of road cave-ins due to subsurface cavities based on the deflection ratio measured with light falling weight deflectometer (LFWD) tests. METHODS : A cavity database for Seoul was developed and sorted. LFWD tests based on the database were conducted on pavement sections with and without road cavities detected by ground-penetrating radar (GPR) tests; after excavating the area, the cavity sizes were measured. The deflection ratio was applied and analyzed by cavity management grade methods of Japan and Seoul. RESULTS : The results of comparative analysis show that the deflection method can detect road cavities in areas of the narrow road (or in narrow areas of the road). The average deflection ratio of the cavity sections to the robust sections were 2.48 for high-risk cavities, 1.85 for medium-risk level cavities, and 1.49 for low-risk cavities. Risk levels in Japan and Seoul were reclassified according to the deflection ratios. CONCLUSIONS : LFWD test results can be applied to verify and improve the subsurface cavity risk level by comparing maximum deflection and deflection ratio between cavity area and non-cavity area at the loading center. LFWD devices also have more advantages compared with larger NDT(Nondestructive test) because FWD and GPR encounter difficulties in traffic control and they could not get in a narrow roads.