Browsing by Author "Kam, T. Y."

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A procedure for power consumption estimation of multi-rotor unmanned aerial vehicle
(2020-01-01)
Chan, C. W.
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Kam, T. Y.
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機械工程學系
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Department of Mechanical Engineering
Unmanned aerial vehicles (UAVs) have the potential to find many commercial applications, which may require relatively long mission times. Therefore, it is important to make UAVs that can complete the mission in an efficient and power saving way. To achieve a prescribed flight mission, a UAV has to perform a number of maneuvers/movements, which will consume a certain amount of power. To maximize the cruising time, not only the power source is able to provide enough amount of power to the UAV but also the parts of the UAV can perform efficiently to save power. Before the minimum power capacity can be determined, it is required that the power consumptions of the UAV parts for the required mission be evaluated in a proper way. In this paper, a procedure is presented to estimate the power consumption of a composite UAV. The configuration as well as the fabrication of the UAV using truss-type parts made of carbon strand/epoxy composite material will be briefly introduced. The power consumptions of the propeller system and electric parts will be evaluated in a systematic way. Experiments were conducted to verify the theoretical predictions. Flight tests were also performed to study the power consumption of the UAV and the suitability of the proposed procedure for power consumption calculation.
A two-level optimization procedure for material characterization of composites using two symmetric angle-ply beams
(2007-10-01)
Chen, C. M.
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Kam, T. Y.
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機械工程學系
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Department of Mechanical Engineering
A two-level optimization procedure for determining elastic constants E-1, E-2, G(12), and v(12) of laminated composite materials using measured axial and lateral strains of two symmetric angle-ply beams with different fiber angles subjected to three-point-bending testing is presented. In the first-level optimization process, the theoretically and experimentally predicted axial and lateral strains of a [(45 degrees/-45 degrees)(6)](s) beam are used to construct the strain discrepancy function which is a measure of the sum of the squared differences between the experimental and theoretical predictions of the axial and lateral strains. The identification of the material constants is then formulated as a constrained minimization problem in which the best estimates of shear modulus and Poisson's ratio of the beam are determined to make the strain discrepancy function a global minimum. In the second-level optimization process, shear modulus and Poisson's ratio determined in the first level of optimization are kept constant and Young's moduli of the second angle-ply beam with fiber angles different from 45 degrees are identified by minimizing the strain discrepancy function established t this level of optimization. The suitability of the proposed procedure for material characterization of composite materials has been demonstrated by means of a number of examples. (c) 2007 Elsevier Ltd. All rights reserved.
A two-level optimization procedure for material characterization of composites using two symmetric angle-ply beams
(2007-10-01)
Chen, C. M.
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Kam, T. Y.
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機械工程學系
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Department of Mechanical Engineering
A two-level optimization procedure for determining elastic constants E-1, E-2, G(12), and v(12) of laminated composite materials using measured axial and lateral strains of two symmetric angle-ply beams with different fiber angles subjected to three-point-bending testing is presented. In the first-level optimization process, the theoretically and experimentally predicted axial and lateral strains of a [(45 degrees/-45 degrees)(6)](s) beam are used to construct the strain discrepancy function which is a measure of the sum of the squared differences between the experimental and theoretical predictions of the axial and lateral strains. The identification of the material constants is then formulated as a constrained minimization problem in which the best estimates of shear modulus and Poisson's ratio of the beam are determined to make the strain discrepancy function a global minimum. In the second-level optimization process, shear modulus and Poisson's ratio determined in the first level of optimization are kept constant and Young's moduli of the second angle-ply beam with fiber angles different from 45 degrees are identified by minimizing the strain discrepancy function established t this level of optimization. The suitability of the proposed procedure for material characterization of composite materials has been demonstrated by means of a number of examples. (c) 2007 Elsevier Ltd. All rights reserved.
Automatic crack detection from 2D images using a crack measure-based B-spline level set model
(2018-01-01)
Nguyen, H. N.
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Kam, T. Y.
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Cheng, P. Y.
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機械工程學系
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Department of Mechanical Engineering
A method is proposed for automatic detection of cracks extracted from 2D images of damaged structures. In the 2D images, the cracks are treated as tree-like topological dark objects of which each tree branch is assumed to be line-like and have local symmetry across the crack center axis. Utilizing the geometric features of the cracks, a novel level set model in which the level set function comprises a set of B-spline basis functions is established to automatically extract the level set function from the 2D crack image with intensity inhomogeneity for crack detection. A new energy functional together with a crack measure technique is introduced to derive an iterative procedure for obtaining the exact level set function of the crack image via an optimization approach. In the iteration process, the level set model can produce smooth and continuous boundaries of the cracks with fast convergence speed. In a comparative study, it has been shown that the proposed method can extract cracks from several real noisy crack images of damaged structures made of various materials more accurate than those determined using the existing crack detection methods which use either different level set models or other image processing techniques in extracting the cracks.
Design and Fabrication of Composite Wind Blades for a 5kW Wind Power System
(2013-01-01)
Kam, T. Y.
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機械工程學系
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Department of Mechanical Engineering
The development of composite wind blades for a 5kW wind turbine blade is presented. During the design process, the distributions of the twisting angle and wind load along the long axis of the blade are determined in the aerodynamic analysis of the blade. A finite element model is constructed for the design and stress analysis of the wind blade made of glass-fabric composites. The failure modes such as the first-ply failure and buckling of the skin of the composite wind blade are identified in the finite element analysis of the blade. The wind blade parts were fabricated using the hand-layup and vacuum-bag molding technique. The blade was composed of two, namely, upper and lower, composite skins which were joined together via a composite shear web. The wind blade was tested to validate the suitability of the design.
Development of Glass-fabric Composite Wind Turbine Blade
(2011)
Kam, T. Y.
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Su, H. M.
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Wang, B. W.
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機械工程學系
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Department of Mechanical Engineering
The development process of a glass-fabric composite wind turbine blade is presented. A finite element model is constructed for the design and stress analysis of the wind blade. The wind blade parts were fabricated using the vacuum-bag molding technique. The assembling process of the wind blade is described in detail. The wind blade was tested to validate the suitability of the design. The finite element method is used to predict the failure wind loads of the wind blade.
Elastic constants identification of composite materials using single angle-ply laminate
(2006-11-01)
Chen, C. M.
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Kam, T. Y.
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機械工程學系
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Department of Mechanical Engineering
A method is presented for identification of elastic constants for composite materials using three measured strains of a single angle-ply laminate subjected to tensile testing. In the proposed method, the trial material constants of the angle-ply laminate are used to predict the corresponding strains in the laminate. An error function is established to measure the difference between the experimental and theoretical predictions of the strains. The identification of material constants is then formulated as a constrained minimization problem in which the material constants are determined to make the error function a global minimum. The accuracy and capability of the proposed method are demonstrated by means of a number of examples of the identification of material constants of angle-ply laminates with different lay-ups. Experimental data obtained from static tensile tests of several angle-ply laminates are used to identify the material constants of the laminates. The excellent results obtained in the experimental investigation have validated the applicability of the proposed method.
Elastic constants identification of symmetric angle-ply laminates via a two-level optimization approach
(2007-03-01)
Chen, C. M.
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Kam, T. Y.
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機械工程學系
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Department of Mechanical Engineering
A two-level optimization method for elastic constants identification of symmetric angle-ply laminates is presented. Measured axial and lateral strains of two symmetric angle-ply laminates with different fiber angles are used in the proposed method to identify four elastic constants of the composite laminates. In the first-level optimization process, the theoretically and experimentally predicted axial and lateral strains of a [(45 degrees/-45 degrees)(2)](s) laminate are used to construct the error function which is a measure of the differences between the experimental and theoretical predictions of the axial and lateral strains. The identification of the material constants is then formulated as a constrained minimization problem in which the best estimates of the shear modulus and Poisson's ratio of the laminate are determined by making the error function a global minimum. The problem of this level of optimization is then solved using a multi-start global minimization algorithm. In the second-level optimization process, the shear modulus and Poisson's ratio determined in the previous level of optimization are kept constant while the Young's moduli of the second angle-ply laminate with fiber angles other than 45 degrees are identified using the same minimization technique that has been used in the previous level. The accuracy of the proposed method are studied by means of a number of numerical examples on the material constants identification of symmetric angle-ply laminates made of different composite materials. Finally, static tensile tests of [(45 degrees/-45 degrees)(2)](s) and [(30 degrees/-30 degrees)(2)](s) laminates made of Gr/ep composite material are performed to measure the strains of the laminates. The experimental data are then used to identify the elastic constants of the laminates. The excellent results obtained in the experimental investigation have demonstrated the feasibility and applications of the proposed method. (c) 2006 Elsevier Ltd. All rights reserved.
Fabrication and Strength Assessment of Composite Corrugated Expansion Tube
(2020-01-01)
Liu, J. W.
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Kam, T. Y.
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機械工程學系
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Department of Mechanical Engineering
A technique is proposed to develop a composite corrugated expansion tube which can achieve a prescribed axial extension when subjected to an internal pressure. The composite corrugated expansion tube was fabricated using annular carbon fabric/PU sheets via the vacuum-assisted resin transfer process. In forming the tube shape, the edges of each annular fabric/PU sheet are adhesively bound to the other two similar sheets at the outer and inner edges, respectively. A finite element model of the corrugated expansion tube is established using the shell elements of the finite element code ANSYS. To illustrate the applications of the proposed technique, the corrugated expansion tube that can sustain internal pressure of 82.73 MPa is developed and tested to verify the accuracy of the finite element model. It has been shown that compressive stresses are induced at the adhesive layers that are located at the outer edges of the corrugated expansion tube. The occurrence of such compressive stresses at the outer edge adhesive layers can increase the failure pressure of the corrugated expansion tube. The failure strength of the composite sheet dominates the incipient failure pressure of the tube. This type of failure mode makes the expansion tube design feasible for practical applications.
Failure Analysis of Small Composite Sandwich Turbine Blade Subjected to Extreme Wind Load
(2011)
Chen, C. P.
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Kam, T. Y.
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機械工程學系
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Department of Mechanical Engineering
In this paper, the progressive failure process of composite sandwich wind turbine blades subjected to wind load is studied via both theoretical and experimental approaches. In the theoretical study, the wind pressure acted on the wind blade surface is estimated in an aerodynamic analysis. The stresses in the wind blade are determined using the finite element code ANSYS in which the skin and the core of the blade are modeled using shell and solid elements, respectively. A phenomenological failure criterion is adopted to predict the first-ply failure strength of the blade. After the occurrence of the initial failure, the material properties at the failure locations are modified following a material degradation rule. The updated stiffness matrix of the blade is then obtained with the consideration of the changes of the material properties and configuration of the blade. An incremental load approach together with a sequential stiffness adjustment technique is used to trace the load-displacement curve and thus determine the ultimate strength of the blade. In the experimental investigation, a composite sandwich wind blade was fabricated for strength testing. In the test, the Whiffle-tree approach was used to simulate the wind load on the blade. The measured ultimate load of the wind blade was then used to validate the accuracy of the proposed method for failure analysis of composite sandwich wind blades. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of [name organizer]
Fault diagnosis method for worm gearbox using convolutional network and ensemble learning
(2020-01-01)
Hsiao, J. C.
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Shivam, Kumar
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Kam, T. Y.
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機械工程學系
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Department of Mechanical Engineering
Worm gearboxes are popular across various industrial applications since they offer significant gear ratios in small installation spaces. Despite having multiple advantages, worm gearboxes are subjected to higher friction due to sliding design and are prone to damage and increased transmission error over the period of operation. Delayed diagnosis of worm gearbox degradation can lead to low-quality products and/or unnecessary production line downtime. Using vibration characteristics of worm gearbox, it is possible to determine the fault and transmission error at a given period in time. In this paper, an ensemble machine learning model is trained and deployed to monitor the transmission error of worm gearbox and classify between new, operational and old conditions. 1D CNN (one dimensional convolutional neural network) model is used to automatically extract features in vibration signal of X, Y, and Z axes and predict the relevant state of worm gear. The proposed technique uses ensemble machine learning technique fusion of features extracted by multi-layer 1D CNN for three axes vibration data. The proposed method could achieve 96% accuracy and performs significantly better than traditional sequential and ensemble machine learning models on a dataset of with 7,870 samples with 800 samples labeled as new condition, 4,740 samples as operational and 2,330 as old.
Free-vibration analysis and material constants identification of laminated composite sandwich plates
(2007-08-01)
Lee, C. R.
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Kam, T. Y.
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Sun, S. J.
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機械工程學系
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Department of Mechanical Engineering
Free vibration of symmetrically laminated composite sandwich plates with elastic edge restraints is studied via the Rayleigh-Ritz approach. The proposed Rayleigh-Ritz method is constructed on the basis of the layer-wise linear displacement theory. The accuracy of the method in predicting natural frequencies of composite sandwich plates with different boundary conditions is verified by the results reported in the literature or the experimental data obtained in this study. The proposed method is then applied to the material constant identification of free composite sandwich plates using the first six theoretical natural frequencies of the plates. In the identification process, trial material constants are used in the present method to predict the theoretical natural frequencies, a frequency discrepancy function is established to measure the sum of the squared differences between the experimental and theoretical natural frequencies, and a stochastic global minimization algorithm is used to search for the best estimates of the material constants by making the frequency discrepancy function a global minimum. Applications of the material constant identification technique are demonstrated by means of several examples.
Identification of mechanical properties of elastically restrained laminated composite plates using vibration data
(2006-08-22)
Lee, C. R.
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Kam, T. Y.
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機械工程學系
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Department of Mechanical Engineering
A nondestructive evaluation method using vibration data to determine mechanical properties (material and spring constants) of elastically restrained laminated composite plates is presented. The Rayleigh-Ritz method in which a set of Legendre's polynomials is adopted to approximate the plate deflection is used to determine the theoretical natural frequencies of the elastically restrained laminated composite plates. A number of natural frequencies extracted from the impulse vibration test data of the laminated composite plates supported by elastic restraints at both the edges and centers of the plates are used in the present method to determine the mechanical properties of the plates. The sum of the squared differences function which measures the differences between the experimentally and theoretically predicted natural frequencies of the elastically restrained laminated composite plates is established. The identification of the plate mechanical properties is then formulated as a constrained minimization problem in which the mechanical properties are determined by making the sum of the squared differences function a global minimum. The feasibility and accuracy of the proposed method are studied by means of several numerical examples on the mechanical properties identification of elastically restrained laminated composite plates with different layups made of various composite materials. Experimental investigation of the mechanical properties identification of several elastically restrained laminated composite plates has been performed to illustrate the applications of the present method. It has been shown that the present method can produce good estimates of the mechanical properties of the elastically restrained laminated composite plates in an efficient and effective way. (c) 2006 Elsevier Ltd. All rights reserved.
Material characterization of laminated composite materials using a three-point-bending technique
(2009-05-01)
Kam, T. Y.
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Chen, C. M.
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Yang, S. H.
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機械工程學系
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Department of Mechanical Engineering
A three-point-bending technique is presented for identifying the elastic constants of laminated composite materials. In the proposed technique, three strains in the axial, lateral, and 45 directions on the bottom surface at the mid-span of a symmetric angle-ply beam subjected to three-point-bending testing are measured for elastic constants identification. The narrow beam theory together with the trial elastic constants is used to predict the theoretical strains of the beam. The theoretical and experimental strains of the beams are then used in a stochastic optimization method to identify the elastic constants of the beam. The accuracy and applications of the proposed technique are demonstrated by means of a number of examples on the elastic constants identification of graphite/epoxy (Gr/ep) or glass/epoxy (Gl/ep) laminated composite materials. The effects of specimen aspect ratio and thickness on the accuracy of the proposed method are investigated. (C) 2008 Elsevier Ltd. All rights reserved.
Mechanical Reliability Analysis of Pneumatic Solenoid Valve Considering Airflow Disorder
(2016-01-01)
Huang, C. Y.
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Su, H. M.
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Jian, B. S.
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Yao, C. L.
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Kam, T. Y.
The mechanical reliability of a pneumatic solenoid valve is studied with the consideration of the failure mode of airflow disorder. The key mechanical components that have important effects on the improper airflow phenomenon are identified as the conical compression spring and rubber O-ring seal. The limit states of key components are constructed via the failure analyses of the components. The probability distributions of the random variables together with the limit states are used to determine the failure probabilities of the key components. A method established on the basis of the series system model is used to estimate the failure probability of the solenoid air valve for the failure mode of airflow disorder.
Modal characteristics of symmetrically laminated composite plates flexibly restrained at different locations
(2009-06-01)
Hao, W. F.
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Kam, T. Y.
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機械工程學系
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Department of Mechanical Engineering
A method for determining modal characteristics (natural frequencies and mode shapes) of symmetrically laminated composite plates restrained by elastic supports at different locations in the interior and on the edges of the plates is presented. The classical lamination theory together with an appropriate set of characteristic functions are used in the Rayleigh-Ritz method to formulate the eigenvalue problem for determining the modal characteristics of the flexibly supported laminated composite plates. Sweep-sine vibration testing of several laminated composite plates flexibly restrained at different locations on the plates is performed to measure their natural frequencies. The close agreement between the experimental and theoretical natural frequencies of the plates has verified the accuracy of the proposed method. The effects of elastic restraint locations on the modal characteristics of flexibly supported laminated composite plates with different lamination arrangements and aspect ratios are studied using the present method. The usefulness of the results obtained for predicting sound radiation behavior of flexibly supported laminated composite plates is discussed. (C) 2009 Elsevier Ltd. All rights reserved.
Optimal design of rectangular composite flat-panel sound radiators considering excitation location
(2014-02-01)
Jiang, C. H.
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Chang, Y. H.
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Kam, T. Y.
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機械工程學系
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Department of Mechanical Engineering
The optimal excitation locations of rectangular composite sound radiation plates to produce relatively smooth sound level pressure (SPL) curves are determined using an optimal design method. In the optimal design process, the vibration of the plate is analyzed using the Rayleigh-Ritz method, the sound pressure produced by the plate is calculated using the first Rayleigh integral, and the optimal excitation location is determined using a global optimization technique. The experimental SPL curves of several sound radiators were measured to verify the accuracy of the theoretical predictions. In the determination of the optimal excitation location, the trial radius of the circular excitation force is used in the vibro-acoustic analysis to predict the theoretical SPL curve of the plate, a SPL discrepancy function is established to measure the sum of the squared differences between the SPLs at the chosen excitation frequencies and the average value of such SPLs, and a global minimization technique is used to search for the best estimate of the radius of the circular excitation force by making the SPL discrepancy function a global minimum. The optimal excitation locations of several composite sound radiators with different aspect ratios and layups are determined using the proposed method. (C) 2013 Elsevier Ltd. All rights reserved.
Progressive failure of composite wind blades with a shear-web spar subjected to static testing
(2017-01-01)
Kam, T. Y.
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Chiu, Y. H.
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機械工程學系
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Department of Mechanical Engineering
Composite wind blades of 1m long comprising glass-fabric/epoxy skins and a sandwich plate-type spar were designed and fabricated for static testing. In the composite wind blades, the spar supports the top and bottom skins to form the airfoil shape of NACA4418. The blades were tested to failure and the failure modes were identified at different loading stages. A structural failure analysis method which consists of a geometrically nonlinear finite element (FE) model and appropriate phenomenological failure criteria is used to study the progressive failure behaviours of the blades subjected to different types of quasi-static loads. The experimental load-displacement curves as well as failure loads and locations for different failure modes are used to validate the suitability of the proposed failure analysis method.
Quasi-static buckling and first-ply failure loads of shear web reinforced glass-fabric composite wind blades
(2017-01-15)
Kam, T. Y.
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Su, H. M.
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Huang, C. Y.
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機械工程學系
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Department of Mechanical Engineering
A procedure is proposed to analyze the structural failure of a composite wind blade subjected to quasi-static loads. The structural failure of a wind blade under extreme wind loads which can be treated as quasi-static loads is an important issue to be tackled when assessing the reliability of a wind turbine. In the proposed structural failure analysis procedure, the geometrically nonlinear finite element (FE) method together with several phenomenological failure criteria is used to investigate the possible failure modes such as incipient buckling, interfacial debonding, and first-ply failure of the blade via an incremental loading approach. The failure loads and locations associated with the possible failure modes for a number of small wind blades with different structural configurations are determined to study the appropriateness of the failure criteria. Static tests of several small glass-fabric composite wind blades were conducted to validate the suitability of the proposed procedure. It has been shown that the experimentally and theoretically predicted failure processes of the wind blades are in good agreement. The applications of the proposed procedure are demonstrated by means of a numerical example in which the failure process of a wind blade under quasi-static wind loads is simulated. (C) 2016 Elsevier Ltd. All rights reserved.
Reliability analysis of composite wind turbine blades considering material degradation of blades
(2020-02-15)
Su, H. M.
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Kam, T. Y.
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交大名義發表
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National Chiao Tung University
In this study, a set of analytical methods was proposed to evaluate the reliability of composite wind turbine blades after material aging, and to improve the blade structure strength to enhance its reliability. Because, the material aging will occur when the blade is affected by the external environment for a long time, consequently, time is an extremely important factor in reliability. Therefore, it is necessary to simulate the effect of environment on materials by aging experiments, so as to obtain the relationship between time, material strength and material constant. The reliability evaluation method used in this study is the direct integration method, which can quickly evaluate the reliability of blades degraded by materials. Because the reliability of the unmodified blade impossible be more than 98% after 20 years, it is necessary to improve the blade and then evaluate the reliability. The weight of the improved blade increased by only 8.57%, but the wind speed of buckling could be delayed by 32.47%, and the reliability could be more than 99% after 20 years, so the improved method meets the demand.