• Title/Summary/Keyword: Notch Problem

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Solution of periodic notch problems in an infinite plate using BIE in conjunction with remainder estimation technique

  • Chen, Y.Z.
    • Structural Engineering and Mechanics
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    • v.38 no.5
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    • pp.619-631
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    • 2011
  • This paper provides a complex variable BIE for solving the periodic notch problems in plane plasticity. There is no limitation for the configuration of notches. For the periodic notch problem, the remainder estimation technique is suggested. In the technique, the influences on the central notch from many neighboring notches are evaluated exactly. The influences on the central notch from many remote notches are approximated by one term with a multiplying factor. This technique provides an effective way to solve the problems of periodic structures. Several numerical examples are presented, and most of them have not been reported previously.

A Study on Notch Bit System for Controlling Blast Vibration and Over-break in Rock Mass (발파공해 해소 및 여굴 최소화를 위한 선균열 암굴착 노치장비 개발에 관한 연구)

  • Jeong, Dong-Ho;Moon, Sang-Jo;An, Dae-Jin;Jeong, Won-Joon;Kim, Eun-Kwan;Kim, Dong-Gyou
    • Tunnel and Underground Space
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    • v.17 no.3 s.68
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    • pp.216-224
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    • 2007
  • Blasting, using shock and dynamic energy of explosive, is very effective tunnel excavation method. But it had serious problem which is the blast vibration and over-break. In recent study, pre-cracked excavation method using notch hole reduced blast vibration and over-break in tunnel, so we performed study about developing notch bit system for making notch hole. In order to make notch hole effectively we had perform drilling experiments changing length and height of notch and in order to improve speed and precision of drilling we had developed notch bit system which consists of drilling bit, notch bit, adapter and notch guide.

An Adaptive Digital Notch Filter for Stabilization of Single-Phase Grid-Connected Inverters With LCL Filter (LCL 필터가 결합된 단상 계통연계형 인버터의 안정화를 위한 적응형 디지털 노치 필터)

  • Heo, Jin-Yong;Kim, Hak-Soo;Nho, Eui-Cheol
    • The Transactions of the Korean Institute of Power Electronics
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    • v.26 no.5
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    • pp.307-314
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    • 2021
  • Even though the LCL filters have superior harmonic attenuation ability to L filters, stability has always been an issue. The system could be unstable because of the resonance phenomenon, especially when digital controller is used. Adding a notch filter to the compensator is one approach to solve the problem. Resonance phenomenon can be inhibited by aligning notch frequency to system resonance frequency. However, resonance frequency variation can be obtained because the actual system has a nonstationary characteristic. Therefore, the system could be unstable, where the system parameters are changed when the conventional notch filter is used. An adaptive digital notch filter that stabilizes the system even system parameters are changed. Simulation and experiment results are provided to verify the validity of the proposed adaptive filter.

Application of 1mm fictitious notch radius approach to the fatigue strength assessment of welded joint (1mm 가상 노치 반경을 이용한 용접부 피로강도 평가에 관한 연구)

  • Kim Yu Il;Gang Jung Gyu;Heo Ju Ho
    • Proceedings of the KWS Conference
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    • v.43
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    • pp.275-277
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    • 2004
  • Fictitious notch radius approach is based on the Neuter's microstructural support hypothesis which assumes that fatigue crack is governed by highly stressed volume of the material right on the weld toe area rather than the surface stress at a pin point of weld toe area. Variety of successes have been achieved in applying this methodology to the fatigue of welded joint, hence, it became one of recommended design procedure in IIW's recommendation as well as many ship classification societies. 1mm fictitious notch radius approach was applied to the various fatigue problems of welded joints in this study covering the effect of weld size, notch stress calculation for 3D geometry and low cycle fatigue problem. It was found that fictitious notch radius approach fumed out to be very effective and accurate in dealing with fatigue strength of welded joint.

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Practical Ultraprecision Positioning of a Ball Screw Mechanism

  • Sato, Kaiji;Maeda, Guilherme Jorge
    • International Journal of Precision Engineering and Manufacturing
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    • v.9 no.2
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    • pp.44-49
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    • 2008
  • This paper describes the problem of ultraprecision positioning with a ball screw mechanism in the microdynamic range, along with its solution. We compared the characteristics of two ball screw mechanisms with different table masses. The experimental results showed that the vibration resulting from the low stiffness of the ball screw degraded the positioning performance in the microdynamic range for the heavyweight mechanism. The proposed nominal characteristic trajectory following (NCTF) controller was designed for ultra precision positioning of the ball screw mechanism. The basic NCTF control system achieved ultra precision positioning performance with the lightweight mechanism, but not with the heavyweight mechanism. A conditional notch filter was added to the NCTF controller to overcome this problem. Despite the differences in payload and friction, both mechanisms then showed similar positioning performance, demonstrating the high robustness and effectiveness of the improved NCTF controller with the conditional notch filter. The experimental results demonstrated that the improved NCTF control system with the conditional notch filter achieved ultra precision positioning with a positioning accuracy of better than 10 nm, independent of the reference step input height.

An iteration approach for multiple notch problem based on complex variable boundary integral equation

  • Chen, Y.Z.
    • Structural Engineering and Mechanics
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    • v.41 no.5
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    • pp.591-604
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    • 2012
  • This paper provides an iteration approach for the solution of multiple notch problem, which is based on the complex variable boundary integral equation (CVBIE). The contours of notches are applied by some loadings. The source points are assumed on the boundary of individual notch and the displacements along the boundaries become unknowns to be investigated. After discretization of the BIE, many influence matrices are obtained. One does not need to assemble many influence matrices into a larger matrix. This will considerably reduce the work in the program. The displacements along the many boundaries can be obtained from an iteration. There is no limitation for the configuration of notches. Several numerical examples are provided to prove the efficiency of the suggested approach.

An efficient algorithm for scaling problem of notched beam specimens with various notch to depth ratios

  • Karamloo, Mohammad;Mazloom, Moosa
    • Computers and Concrete
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    • v.22 no.1
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    • pp.39-51
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    • 2018
  • This study introduces a new algorithm to determine size independent values of fracture energy, fracture toughness, and fracture process zone length in three-point bending specimens with shallow to deep notches. By using the exact beam theory, a concept of equivalent notch length is introduced for specimens with no notches in order to predict the peak loads with acceptable precisions. Moreover, the method considers the variations of fracture process zone length and effects of higher order terms of stress field in each specimen size. In this paper, it was demonstrated that the use of some recently developed size effect laws raises some concerns due to the use of nonlinear regression analysis. By using a comprehensive fracture test data, provided by Hoover and Bazant, the algorithm has been assessed. It could be concluded that the proposed algorithm can facilitate a powerful tool for size effect study of three-point bending specimens with different notch lengths.

A Novel Cogging Torque Reduction Method for Single-Phase Brushless DC Motor

  • Park, Young-Un;Cho, Ju-Hee;Rhyu, Se-Hyun;Kim, Dae-Kyong
    • Journal of Magnetics
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    • v.18 no.2
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    • pp.117-124
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    • 2013
  • Single-phase, brushless DC (BLDC) motors have unequal air-gaps to eliminate the dead-point where the developed torque is zero. Unfortunately, these unequal air-gaps can deteriorate the motor characteristics in the cogging torque. This paper proposes a novel design for a single-phase BLDC motor with an asymmetric notch to solve this problem. In the design method, the asymmetric notches were placed on the stator pole face, which affects the change in permanent magnet shape or the residual flux density of the permanent magnet. Parametric analysis was performed to determine the optimal size and position of the asymmetric notch to reduce the cogging torque. Finite element analysis (FEA) was used to calculate the cogging torque. A more than 28% lower cogging torque compared to the initial model with no notch was achieved.

Small Fatigue Crack Measurement and Crack Growth Characteristics for Smooth and Notch Specimens (평활 및 노치재의 미소피로균열측정과 성장특성)

  • 이종형
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.9
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    • pp.2145-2152
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    • 1993
  • The objective of this paper is to examine the detection limit, growth characteristics and notch curvature radius in short crack problem. Measurement techniques such as ultrasonic method and back-face strain compliance method were adopted. The fatigue crack growth rate of the short crack is slower than that of a long crack for a notched specimen. The characteristic of crack growth and crack closure is same as the case of a delay of crack growth caused by constant amplitude load for an ideal crack or single peak overload for a fatigue crack. The short crack is detected effectively by ultrasonic method. A short surface crack occurs in the middle of specimen thickness and is transient to a through crack depth is larger than the notch curvature radius.

An elliptical fracture criterion for mixed mode fracture I+II emanating from notches

  • El Minor, H.;Pluvinage, G.;Azari, Z.
    • Structural Engineering and Mechanics
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    • v.26 no.1
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    • pp.87-97
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    • 2007
  • Some mixed mode fracture criterion may be converted in to elliptical or ellipsoidal formula with the aid of mathematical translation. Hence, the crack initiation in mixed mode fracture I+II emanating from notches, has been studied using notched circular ring specimens. On the basis of Irwin (1957) theory, a new criteria in mixed mode fracture I+II, based fracture elliptic criterion and notch stress intensity factors has been developed.