• 한국기계가공학회지
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• 제11권4호
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• pp.7-12
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• 2012

The cutting force for peripheral end-milling considering run-out property was estimated and its result was compared with that of measured one. An experimental coefficient modelling was used for the formulation of theoretical end-milling force by considering the specific cutting force coefficient. Also, the specific cutting force, that is the multiplication of specific cutting force coefficient and uncut chip thickness, was used for the prediction of end-milling force. The end-milling force mechanics with run-out was presented for the estimation of theoretical force in peripheral end-milling by considering the geometric shape of the workpiece part. As a result, the estimated end-milling force shows a good consistency with the measured one. And it can be used for the prediction of force history in end-milling with run-out which incurs different start and exit immersion angle in entering and exiting condition.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.262-265
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• 2002

Fused deposition modelling(FDM) is a rapid prototyping(RP) process that fabricates part layer by layer by deposition of molten thermoplastic material extrude from a nozzle. RP system has many benefit. One of the benefit would be the ability to experiment wiか physical objects of my complexity in a relatively short period of time. But it has a matter of surface roughness and geometric accuracy. We study on Influence of angle of tangent line and area error on sphere surface roughness at fused deposition.

• Smart Structures and Systems
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• 제18권1호
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• pp.17-29
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• 2016

In this paper, the possibility of using human induced loading (HIL) to detect a decrease of tension in the cable-stays of an existing footbridge is investigated. First, a reliable finite elements model of an existing footbridge is developed by calibration with experimental data. Next, estimates of the tension in the cables are derived and their dependency on the modal features of the deck is investigated. The modelling of the HIL is briefly discussed and used to perform the nonlinear, large strain, dynamic finite elements analyses. The results of these analyses are assessed with focus on characterizing the time histories of the tension in the cables under pedestrian crossing and their effects on the deck response for different initial conditions. Finally, the control perspective is introduced in view of further research.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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• pp.393-400
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• 2001

A simple numerical modelling technique is proposed for estimating the shear stress distribution in beams of framed tube structures with multiple internal tubes. The structures are analysed using a continuum approach in which each tube is individually modelled by a tube beam that accounts for the flexural and shear deformations, as well as the shear lag effects. The method idealises the discrete tubes-in-tube structures as an assemblage of equivalent multiple beams, each composed of orthotropic plate panels. The numerical analysis of shear stress is based on the elastic theory in conjunction with the minimum potential energy principle. By simplifying assumptions regarding the form of strain distributions in external and internal tubes, the shear stress distributions are expressed in terms of a series of linear functions of the second moments of area of the structures and the corresponding geometric and material properties, as well as the applied loads. The simplicity and accuracy of the proposed method are demonstrated through the solutions of three numerical examples.

• Smart Structures and Systems
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• 제2권1호
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• pp.61-80
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• 2006

The concept of structural vibration control is to absorb vibration energy of the structure by introducing auxiliary devices. Various types of structural vibration control theories and devices have been recently developed and introduced into mechanical systems. One of such devices is damper employing controllable fluids such as ElectroRheological (ER) or MagnetoRheological (MR) fluids. MagnetoRheological (MR) materials are suspensions of fine magnetizable ferromagnetic particles in a non-magnetic medium exhibiting controllable rheological behaviour in the presence of an applied magnetic field. This paper presents the modelling of an MRfluid damper. The damper model is developed based on Newtonian shear flow and Bingham plastic shear flow models. The geometric parameters are varied to get the optimised damper characteristics. The numerical analysis is carried out to estimate the damping coefficient and damping force. The analytical results are compared with the experimental results. The results confirm that MR damper is one of the most promising new semi-active devices for structural vibration control.

• Advances in nano research
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• 제15권5호
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• pp.485-493
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• 2023

Critical multi-field loads and free vibration responses of the sandwich piezoelectric/piezomagnetic microplate subjected to combination of magnetoelectromechanical loads based on a thickness-stretched higher order shear deformable model using Hamilton's principle. The lateral displacement is assumed summation of bending, shearing and stretching functions. The elasti core is sandwiched by a couple of piezoelectric/piezomagnetic face-sheets subjected to electromagnetocmechanical loads. The work of external force is calculated with considering the in-plane mechanical, electrical and magnetic loads based on piezomagnetoelasticity relations. The critical multi field loading and natural frequency analysis are performed to investigate influence of geometric and loading parameters on the responses. A verification is performed for justification of the numerical results.

• Structural Engineering and Mechanics
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• 제65권5호
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• pp.573-585
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• 2018

This article presents strain gradient elasticity-based procedures for static bending, free vibration and buckling analyses of functionally graded rectangular micro-plates. The developed method allows consideration of smooth spatial variations of length scale parameters of strain gradient elasticity. Governing partial differential equations and boundary conditions are derived by following the variational approach and applying Hamilton's principle. Displacement field is expressed in a unified way to produce numerical results in accordance with Kirchhoff, Mindlin, and third order shear deformation theories. All material properties, including the length scale parameters, are assumed to be functions of the plate thickness coordinate in the derivations. Developed equations are solved numerically by means of differential quadrature method. Proposed procedures are verified through comparisons made to the results available in the literature for certain limiting cases. Further numerical results are provided to illustrate the effects of material and geometric parameters on bending, free vibrations, and buckling. The results generated by Kirchhoff and third order shear deformation theories are in very good agreement, whereas Mindlin plate theory slightly overestimates static deflection and underestimates natural frequency. A rise in the length scale parameter ratio, which identifies the degree of spatial variations, leads to a drop in dimensionless maximum deflection, and increases in dimensionless vibration frequency and buckling load. Size effect is shown to play a more significant role as the plate thickness becomes smaller compared to the length scale parameter. Numerical results indicate that consideration of length scale parameter variation is required for accurate modelling of graded rectangular micro-plates.

• Steel and Composite Structures
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• 제33권4호
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• pp.595-614
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• 2019

In cold-formed steel (CFS) structures, such as trusses, transmission towers and portal frames, the use of back-to-back built-up CFS unequal angle sections are becoming increasingly popular. In such an arrangement, intermediate welds or screw fasteners are required at discrete points along the length, preventing the angle sections from buckling independently. Limited research is available in the literature on axial strength of back-to-back built-up CFS unequal angle sections. The issue is addressed herein. This paper presents an experimental investigation on both the welded and screw fastened back-to-back built-up CFS unequal angle sections under axial compression. The load-axial shortening and the load verses lateral displacement behaviour along with the deformed shapes at failure are reported. A nonlinear finite element (FE) model was then developed, which includes material non-linearity, geometric imperfections and modelling of intermediate fasteners. The FE model was validated against the experimental test results, which showed good agreement, both in terms of failure loads and deformed shapes at failure. The validated FE model was then used for the purpose of a parametric study to investigate the effect of different thicknesses, lengths and, yield stresses of steel on axial strength of back-to-back built-up CFS unequal angle sections. Five different thicknesses and seven different lengths (stub to slender columns) with two different yield stresses were investigated in the parametric study. Axial strengths obtained from the experimental tests and FE analyses were used to assess the performance of the current design guidelines as per the Direct Strength Method (DSM); obtained comparisons show that the current DSM is conservative by only 7% on average, while predicting the axial strengths of back-to-back built-up CFS unequal angle sections.

• 한국자원공학회지
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• 제55권6호
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• pp.614-623
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• 2018

최근 한반도 남동부에서 발생한 연이은 강진들로 인해 국내에서도 지진 방재에 대한 관심도가 높아지고 있다. 본 연구에서는 최근 들어 급격히 진보하고 있는 시각지능과 가상현실 분야 기술들을 기반으로 하는, 맞춤형 지진재해 대응을 위한 기술적 방법론에 대해 살펴보고자 한다. 해당 기술은 카메라를 이용한 생활공간 영상 정보의 취득, 개별 객체의 영상 기반 인식, 3차원 공간 정보의 추출, 이산요소법 등을 활용한 가상 지진의 동역학적 모의, 가상현실환경에서의 모의 지진 실감화 등의 단계를 통해 구성된다. 본 연구에서는 이러한 전체 기술 프로세스를 구성하기 위한 각 단계의 프로세스, 해당 이슈와 관련한 현재 기술 동향, 실시를 위한 기술적 해결 과제 등을 분석하였다.

• Steel and Composite Structures
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• 제42권1호
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• pp.1-22
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• 2022

In cold-formed steel (CFS) structures, such as trusses, transmission towers and portal frames, the use of back-to-back built-up CFS unequal angle sections are becoming increasingly popular. In such an arrangement, intermediate welds or screw fasteners are required at discrete points along the length, preventing the angle sections from buckling independently. Limited research is available in the literature on axial strength of back-to-back built-up CFS unequal angle sections. The issue is addressed herein. This paper presents an experimental investigation reported by the authors on back-to-back built-up CFS unequal angle sections with intermediate stiffeners under axial compression. The load-axial shortening behaviour along with the deformed shapes at failure are reported. A nonlinear finite element (FE) model was then developed, which includes material non-linearity, geometric imperfections and modelling of intermediate fasteners. The FE model was validated against the experimental test results, which showed good agreement, both in terms of failure loads and deformed shapes at failure. The validated finite element model was then used for the purpose of a parametric study comprising 96 models to investigate the effect of longer to shorter leg ratios, stiffener provided in the longer leg, thicknesses and lengths on axial strength of back-to-back built-up CFS unequal angle sections. Four different thicknesses and seven different lengths (stub to slender columns) with three overall widths to the overall depth (B/D) ratios were investigated in the parametric study. Axial strengths obtained from the experimental tests and FE analyses were used to assess the performance of the current design guidelines as per the Direct Strength Method (DSM); obtained comparisons show that the current DSM is conservative by only 7% and 5% on average, while predicting the axial strengths of back-to-back built-up CFS unequal angle sections with and without the stiffener, respectively.