• 한국유체기계학회 논문집
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• 제7권5호
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• pp.7-12
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• 2004

Multi-path ultrasonic flowrate measuring technology is being received much attentions from a variety of industrial fields to exactly measure the flowrate. Multi-path ultrasonic flowmeter has much advantage since it has no moving parts and little pressure loss. It offers good accuracy, repeatability, linearity and turn-down ratio can be over 1:50. The present study investigates flowrate integration errors using weighting factors. A theoretical flow model uses power law to describe a fully developed velocity profiles and wall roughness is changed. Gaussian, Chebyshev, and Tailor methods are used to integrate line-average velocities. The obtained results show that Chebyshev method in 2, 4-path arrangement and Gaussian method in 3, 5-path arrangement are not affected for wall roughness changes.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.378-386
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• 2002

Multi-path ultrasonic Sow measurement system uncertainty is determined by assigning an expected error of each component of flow measurement and then defining the total flow measurement uncertainty as square root of the sum of squared values of the individual error. Sources of uncertainty for flow measurement are geometry, transit time and velocity profile integration uncertainty. A theoretical uncertainty model for multi-path ultrasonic transit time flowmeter configured with parallel 5 chords, is derived from and calculated by dry calibration method.

• 한국산학기술학회논문지
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• 제18권5호
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• pp.29-34
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• 2017

본 논문에서는 압연 공정을 통해 리드용 와이어를 생산할 때 생산성을 향상시키기 위해 와이어의 직진 속도를 증가시키는 방법을 연구했다. 직진 속도를 증가시킬 때 가장 중요한 점은 와이어가 원래의 목적을 바르게 수행할 수 있는 것이다. 즉, 와이어의 직진 속도가 증가함과 동시에 균열이 발생하지 않으며, 치수 공차를 만족시켜야 한다. 하지만 와이어의 직진속도를 증가시키게 되면 기존의 압하량 보다 더 큰 수치를 주어야 하고 이는 와이어에 보다 큰 손상을 주어 표면에 무리를 주게 된다. 따라서 기존의 2단계 평압연 공정을 통해 생산되었던 와이어의 필요스펙을 충족시키면서 생산성 향상까지 도모할 수 있는 3단계 평압연 공정에 관해 연구하였다. 본 연구에서는 3단계 평압연 롤러의 압하량만을 변수로 가정하고 다른 조건은 현장 조건과 일치시킨다. 상용 PIDO(Process Integration and Design Optimization) 툴인 PIANO (Process Integration, Design and Optimization)를 통해 지정한 변수 3가지를 조작하면서 실험점을 분포하고 이를 바탕으로 최적설계를 진행하여 와이어의 생산성을 향상시킴과 동시에 필요 스펙인 최대 응력의 최소화가 가능하도록 설계되었다.

• 대한기계학회논문집B
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• 제28권10호
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• pp.1271-1278
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• 2004

In order to measure non-intrusively velocity profile in liquid metal flow, a modified electromagnetic flowmeter was designed, which was based on electromagnetic tomography technique. Under the assumption that flow is fully-developed, axisymmetric and rectilinear, the velocity profile was reconstructed after the flowmeter equation, the first kind of Fredholm integration equation, was linearized. In reconstruction process Tikhonov regularization method with regularization parameter was used. The reconstructed velocity profile had the nearly same as turbulent flow profile which was approximately represented as log law. In addition, flowmeter output fur a fixed magnet rotation angle was linearly proportional to flow rate. When magnet rotation angle was 54$^{\circ}$, axisymmetric weight function was nearly uniform so that the flowmeter gives a constant signal for any fully-developed, axisymmetric and rectilinear profile with a constant flow rate.

• Korean Journal of Hydrosciences
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• 제3권
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• pp.45-59
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• 1992

The flow characteristics varying with rate of the radius of curvature to width (Rc/B) in open channel bends are investigated with a simplified numerical model. Secondary flow velocity and transverise bed slope are formulated from the equations of momentum and force balance analysis, respectively. The conservation equations of mass and streamwise momentum are simplified by depth integration and its solution could be obtained from the explicit finite difference method. Three sets of computer simulation are executed. The rates of Rc/B adopted in simulations are 2.7, 5.4 and 8.1. The terms analyzed in this paper secondary flow velocity, streamwise velocity, the path of maximum steamwise velocity, deviation angle, and mass-shift velocity.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1749-1754
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• 2004

In order to measure non-intrusively velocity profile in liquid metal flow, a modified electromagnetic flowmeter was designed, which was based on electromagnetic tomography technique. Under the assumption that flow is fully-developed, axisymmetric and rectilinear, the velocity profile was reconstructed after the flowmeter equation, the first kind of Fredholm integration equation, was linearized. In reconstruction process Tikhonov regularization method with regularization parameter was used. The reconstructed velocity profile had the nearly same as turbulent flow profile which was approximately represented as log law. In addition, flowmeter output for a fixed magnet rotation angle was linearly proportional to flow rate. When magnet rotation angle was $54^{\circ}$, axisymmetric weight function was nearly uniform so that the flowmeter gives a constant signal for any fully-developed, axisymmetric and rectilinear profile with a constant flow rate.

• 한국가시화정보학회지
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• 제14권2호
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• pp.46-51
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• 2016

In this study, a Masked Omni-Directional Integration(MODI) method for pressure calculation is proposed using the Particle Image Velocimetry (PIV) data. To obtain the velocity field, the Affine PIV method was adopted. Synthetic images were generated for a solid body rotation. Calculation on the pressure was based on the Navier-Stokes equation. The results obtained by the MODI were compared with those obtained by theoretical pressure and by the Omni-Directional Integration(ODI) method. It was shown that the minimum error by the proposed MODI method was attained when the mask size was 1.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.111-118
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• 2004

For the precise analysis of high velocity impact problem though FEM with element erosive method, the adequate mesh size and critical equivalent plastic strain(EQPS) is chosen prior to the simulation. In this research, it is strongly required from a standpoint that critical EQPS is used to decide whether perforation occurs or not. The optimization of dual armor plate consisting of 4340 steel and 2024 aluminium against a die steel sphere with high-velocity has been suggested using Lagrangian explicit time-integration code, NET2D. The response surface method based on the design of experiment is utilized for the size optimization. The optimized thickness of each layer, in which perforation does not occur, the strength of multi-layer is maximized and total weight is minimized, is obtained at a constant velocity of a pellet with a designated total thickness.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1631-1637
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• 2002

This paper presents a method for calculating contact force between bodies on plane. At each integration time step, the proposed method finds expected contact point on their outlines and then calculates penetration, velocity of penetration and contact force. This paper adopts continuous analysis method and multi-point contact method to calculate contact force. To obtain the accurate expected contact point on their outlines, a new algorithm is developed. The accuracy of the proposed algorithm is demonstrated by comparing the numerical results of the proposed method and DADS.

• 대한기계학회논문집
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• 제17권12호
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• pp.2982-2994
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• 1993

Low-velocity impact responses of composite laminates are investigated using the finite element method based on various theories. In two-dimensional nonlinear analysis, a displacement field considering higher order shear deformation and large deflection of the laminate is assumed and a finite element formulation is developed using a C$^{o}$-continuous 9-node plate element. Also, three-dimensional linear analysis based on the infinitesimal strain-displacement assumptions is performed using 8-node brick elements with incompatible modes. A modified Hertzian contact law is incorporated into the finite element program to evaluate the impact force. In the time integration, the Newmark constant acceleration algorithm is used in conjuction with successive iterations within each time step. Numerical results from static analysis as well as the impact response analysis are presented including impact force histories, deflections, strains in the laminate. Impact responses according to two typical low-velocity impact conditions are compared each other.