This page has only limited features, please log in for full access.
In order to improve precision of machines in operation, the actual parameters on a machine, such as stiffness of its footings, can be sought using sensitivity-based model updating methodology. The under-determined model updating problem is avoided by moving a perturbation mass around the machine and creating new sensitivity equations. The positions of the perturbation mass are determined using the singular value decomposition (SVD) analysis of sensitivity matrix. Plate-footings assembly is utilized in both simulation and experiment to demonstrate the feasibility of the model updating of footing stiffness. Results show that this methodology can identify the weak footings, if several constraints are imposed on the relationship among stiffness parameters. Studies carried out on machine tool prototype are described.
Shih-Yin Chien; Zhen Wah Chew; Yum Ji Chan. Identify Loose Footings of Machines Using Model Updating-Based Method. Fracture, Fatigue, Failure and Damage Evolution , Volume 3 2020, 255 -258.
AMA StyleShih-Yin Chien, Zhen Wah Chew, Yum Ji Chan. Identify Loose Footings of Machines Using Model Updating-Based Method. Fracture, Fatigue, Failure and Damage Evolution , Volume 3. 2020; ():255-258.
Chicago/Turabian StyleShih-Yin Chien; Zhen Wah Chew; Yum Ji Chan. 2020. "Identify Loose Footings of Machines Using Model Updating-Based Method." Fracture, Fatigue, Failure and Damage Evolution , Volume 3 , no. : 255-258.
To build reliable digital twins of machine tools (also known as “virtual machine tools”), the dynamic properties of nonlinear components in the model should be close to the actual counterpart. The nonlinear dynamics mean that the frequency response functions (FRFs) derived from tap tests are inaccurate because of difference in excitation levels. In this study, dynamic behavior of a linear guideway is sought experimentally using harmonic excitation. It is found that the dynamic properties are affected by (1) excitation level, (2) lubrication, (3) specified preload and (4) static lateral load, and the dynamic properties cannot be fully described using the Hertzian contact model.
Ting-Yen Wu; Yi-Chun Lo; Yum Ji Chan. Control Parameters in Non-linear Properties of Linear Guideway in Lateral Direction. Fracture, Fatigue, Failure and Damage Evolution , Volume 3 2020, 189 -197.
AMA StyleTing-Yen Wu, Yi-Chun Lo, Yum Ji Chan. Control Parameters in Non-linear Properties of Linear Guideway in Lateral Direction. Fracture, Fatigue, Failure and Damage Evolution , Volume 3. 2020; ():189-197.
Chicago/Turabian StyleTing-Yen Wu; Yi-Chun Lo; Yum Ji Chan. 2020. "Control Parameters in Non-linear Properties of Linear Guideway in Lateral Direction." Fracture, Fatigue, Failure and Damage Evolution , Volume 3 , no. : 189-197.
Dynamic properties of rectangular stepped Mindlin plates plates with non-Lévy boundary conditions are investigated in this study. Plates are modelled based on the Rayleigh-Ritz method, whereas admissible functions are obtained using hierarchic high-order Timoshenko beam finite elements. The proposed method leads to reduced and step-independent error level compared with using uniform-beam admissible functions, and the boundary conditions are better approximated. Computation involved is significantly less than using the finite element method, thus suitable to be used in environments with limited computational power. The method is demonstrated numerically on cantilevered (CFFF), mixed (CFEF) and free (FFFF) plates and experimentally on FFFF plates. Compared with experimental results, natural frequency error of an FFFF plate is less than 1% and most of the mode assurance criterion (MAC) values are above 0.9.
Y.J. Chan; C.-Y. Tai. Free vibration of stepped rectangular Mindlin plates with non-Lévy boundary conditions. International Journal of Mechanical Sciences 2018, 144, 668 -678.
AMA StyleY.J. Chan, C.-Y. Tai. Free vibration of stepped rectangular Mindlin plates with non-Lévy boundary conditions. International Journal of Mechanical Sciences. 2018; 144 ():668-678.
Chicago/Turabian StyleY.J. Chan; C.-Y. Tai. 2018. "Free vibration of stepped rectangular Mindlin plates with non-Lévy boundary conditions." International Journal of Mechanical Sciences 144, no. : 668-678.
Time-domain data-driven stochastic subspace identification operational modal analysis (SSI-OMA) is widely used in civil engineering. In this study, such an algorithm is applied to analyse a machine tool test stand, with excitation provided through pseudo-random excitation of the feed table. SSI-OMA is computationally more efficient than previous implementations, with a lower order of analysis (32 instead of 100) and higher bandwidth. The key parameters that determine the quality of SSI-OMA have been determined. It is shown that the function of reference nodes in measurement can be replaced by a time-alignment algorithm, if the noise level in signals are low. In addition, application of micro-electrical-mechanical (MEMS) accelerometers to carry out SSI-OMA in machine tools is investigated.
Yum Ji Chan; Jing-Wei Huang. Time-Domain Operational Modal Analysis in Machine Tools: Optimal Parameters and Practical Issues. International Journal of Precision Engineering and Manufacturing 2018, 19, 889 -897.
AMA StyleYum Ji Chan, Jing-Wei Huang. Time-Domain Operational Modal Analysis in Machine Tools: Optimal Parameters and Practical Issues. International Journal of Precision Engineering and Manufacturing. 2018; 19 (6):889-897.
Chicago/Turabian StyleYum Ji Chan; Jing-Wei Huang. 2018. "Time-Domain Operational Modal Analysis in Machine Tools: Optimal Parameters and Practical Issues." International Journal of Precision Engineering and Manufacturing 19, no. 6: 889-897.
Frequency response functions (FRFs) of thin workpieces, which are typically clamped step-thickness cantilever plates, are needed at every stage in order to avoid chatter (cutting-related instability). Due to variability of machining procedure, FRF estimation is proposed to be carried out at the embedded computer at machine tool, which has limited computing power. A combination of Reissner-Mindlin plate theory and Rayleigh-Ritz method are used to form small system matrices to estimate FRFs. Mode shapes of uniform-thickness Timoshenko beams are taken as the admissible functions. Example shows that a system with approximately 500 DOFs, which is much smaller than a full finite-element model with 10,000’s of DOFs, can estimate the first four natural frequencies with a similar error level during every step of cut. Additionally, experimental natural frequencies are used to estimate the contact stiffness at the vice. As a result, the change in those natural frequencies during machining are determined accurately.
Yum Ji Chan; Chung-Yu Tai; Yuan-You Li. Efficient Estimation of Clamped Step-Thickness Plates FRFs in Industrial Systems. Conference Proceedings of the Society for Experimental Mechanics Series 2018, 61 -65.
AMA StyleYum Ji Chan, Chung-Yu Tai, Yuan-You Li. Efficient Estimation of Clamped Step-Thickness Plates FRFs in Industrial Systems. Conference Proceedings of the Society for Experimental Mechanics Series. 2018; ():61-65.
Chicago/Turabian StyleYum Ji Chan; Chung-Yu Tai; Yuan-You Li. 2018. "Efficient Estimation of Clamped Step-Thickness Plates FRFs in Industrial Systems." Conference Proceedings of the Society for Experimental Mechanics Series , no. : 61-65.
Yum Ji Chan; Jing-Wei Huang. Multiple-point vibration testing with micro-electromechanical accelerometers and micro-controller unit. Mechatronics 2017, 44, 84 -93.
AMA StyleYum Ji Chan, Jing-Wei Huang. Multiple-point vibration testing with micro-electromechanical accelerometers and micro-controller unit. Mechatronics. 2017; 44 ():84-93.
Chicago/Turabian StyleYum Ji Chan; Jing-Wei Huang. 2017. "Multiple-point vibration testing with micro-electromechanical accelerometers and micro-controller unit." Mechatronics 44, no. : 84-93.
Timoshenko beam theory (TBT) is suitable for vibration studies as it describes beams with small models. The super-convergent Timoshenko beam element is improved by adding hierarchic high-order shape functions using Legendre polynomials, and correction terms were added where necessary. The proposed element is validated in static, dynamic and rotordynamic analyses. With the same model size, the fractional error of the 2nd cantilever beam natural frequency with the p-version beam element is 1/100th of the h-version counterpart, and error in estimating natural frequency split in rotors is reduced. The proposed element is also applied to estimate natural frequencies in experiments.
C.-Y. Tai; Y.J. Chan. A hierarchic high-order Timoshenko beam finite element. Computers & Structures 2016, 165, 48 -58.
AMA StyleC.-Y. Tai, Y.J. Chan. A hierarchic high-order Timoshenko beam finite element. Computers & Structures. 2016; 165 ():48-58.
Chicago/Turabian StyleC.-Y. Tai; Y.J. Chan. 2016. "A hierarchic high-order Timoshenko beam finite element." Computers & Structures 165, no. : 48-58.
Broadband noise with profound low-frequency profile is prevalent and difficult to be controlled mechanically. This study demonstrates effective broadband sound absorption by reducing the mechanical reactance of a loudspeaker using a shunt circuit through electro-mechanical coupling, which induces reactance with different signs from that of loudspeaker. An RLC shunt circuit is connected to the moving coil to provide an electrically induced mechanical impedance which counters the cavity stiffness at low frequencies and reduces the system inertia above the resonance frequency. A sound absorption coefficient well above 0.5 is demonstrated across frequencies between 150 and 1200 Hz. The performance of the proposed device is superior to existing passive absorbers of the same depth (60 mm), which has lower frequency limits of around 300 Hz. A passive noise absorber is further proposed by paralleling a micro-perforated panel with shunted loudspeaker which shows potentials in absorbing band-limit impulse noise.
Yumin Zhang; Yum Ji Chan; Lixi Huang. Thin broadband noise absorption through acoustic reactance control by electro-mechanical coupling without sensor. The Journal of the Acoustical Society of America 2014, 135, 2738 -2745.
AMA StyleYumin Zhang, Yum Ji Chan, Lixi Huang. Thin broadband noise absorption through acoustic reactance control by electro-mechanical coupling without sensor. The Journal of the Acoustical Society of America. 2014; 135 (5):2738-2745.
Chicago/Turabian StyleYumin Zhang; Yum Ji Chan; Lixi Huang. 2014. "Thin broadband noise absorption through acoustic reactance control by electro-mechanical coupling without sensor." The Journal of the Acoustical Society of America 135, no. 5: 2738-2745.
Dependence of the performance of feedforward active duct noise control on secondary loudspeaker parameters is investigated. Noise reduction performance can be improved if the force factor of the secondary loudspeaker is higher. For example, broadband noise reduction improvement up to 1.6 dB is predicted by increasing the force factor by 50%. In addition, a secondary loudspeaker with a larger force factor was found to have quicker convergence in the adaptive algorithm in experiment. In simulations, noise reduction is improved in using an adaptive algorithm by using a secondary loudspeaker with a heavier moving mass. It is predicted that an extra broadband noise reduction of more than 7 dB can be gained using an adaptive filter if the force factor, moving mass and coil inductance of a commercially available loudspeaker are doubled. Methods to increase the force factor beyond those of commercially available loudspeakers are proposed.
Yum-Ji Chan; Lixi Huang; James Lam. Effects of secondary loudspeaker properties on broadband feedforward active duct noise control. The Journal of the Acoustical Society of America 2013, 134, 257 -263.
AMA StyleYum-Ji Chan, Lixi Huang, James Lam. Effects of secondary loudspeaker properties on broadband feedforward active duct noise control. The Journal of the Acoustical Society of America. 2013; 134 (1):257-263.
Chicago/Turabian StyleYum-Ji Chan; Lixi Huang; James Lam. 2013. "Effects of secondary loudspeaker properties on broadband feedforward active duct noise control." The Journal of the Acoustical Society of America 134, no. 1: 257-263.
Yum Ji Chan; Yumin Zhang. Determination of the physical parameters of systems with a time-domain approach. The Journal of the Acoustical Society of America 2012, 131, 3483 -3483.
AMA StyleYum Ji Chan, Yumin Zhang. Determination of the physical parameters of systems with a time-domain approach. The Journal of the Acoustical Society of America. 2012; 131 (4):3483-3483.
Chicago/Turabian StyleYum Ji Chan; Yumin Zhang. 2012. "Determination of the physical parameters of systems with a time-domain approach." The Journal of the Acoustical Society of America 131, no. 4: 3483-3483.
The static magnetic field of a magnetic resonance imaging scanner can be distorted by the presence of materials, perturbing the spatial encoding process in magnetic resonance imaging and often resulting in image artifacts. The relationship between the image artifact size and magnetic susceptibility of the material specimen is of interest to engineers for the design of devices that are to be compatible with the imaging volume of the scanner. In this study, a finite-element method was used to simulate the distorted magnetic field of samples with different susceptibilities. With the knowledge of the external- and self- magnetic field interactions, a Lorentz correction was applied to compute the magnetic field deviation. The simulated results were then validated by the corresponding experimental magnetic resonance images.
César A F Montesinos; Zion T H Tse; Yum Ji Chan; Haytham Elhawary; Marc Rea; Abbi Hamed; Ian Young; Michael Lamperth. Finite-element analysis for magnetic resonance image artifact evaluation. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 2011, 226, 49 -54.
AMA StyleCésar A F Montesinos, Zion T H Tse, Yum Ji Chan, Haytham Elhawary, Marc Rea, Abbi Hamed, Ian Young, Michael Lamperth. Finite-element analysis for magnetic resonance image artifact evaluation. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine. 2011; 226 (1):49-54.
Chicago/Turabian StyleCésar A F Montesinos; Zion T H Tse; Yum Ji Chan; Haytham Elhawary; Marc Rea; Abbi Hamed; Ian Young; Michael Lamperth. 2011. "Finite-element analysis for magnetic resonance image artifact evaluation." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 226, no. 1: 49-54.
BACKGROUND: MR elastography (MRE) is an emerging technique for tumor diagnosis. MRE actuation devices require precise mechanical design and radiofrequency engineering to achieve the required mechanical vibration performance and MR compatibility. METHOD: A method of designing a general-purpose, compact and inexpensive MRE actuator is presented. It comprises piezoelectric bimorphs arranged in a resonant structure designed to operate at its resonant frequency for maximum vibration amplitude. An analytical model was established to understand the device vibration characteristics. RESULTS: The model-predicted performance was validated in experiments, showing its accuracy in predicting the actuator resonant frequency with an error < 4%. The device MRI compatibility was shown to cause minimal interference to a 1.5 tesla MRI scanner, with maximum signal-to-noise ratio reduction of 7.8% and generated artefact of 7.9 mm in MR images. CONCLUSIONS: A piezoelectric MRE actuator is proposed, and its implementation, vibration issues and future work are discussed. Copyright © 2011 John Wiley & Sons, Ltd
Zion Tse; Yum Ji Chan; Henning Janssen; Abbi Hamed; Ian Young; Michael Lamperth. Piezoelectric actuator design for MR elastography: implementation and vibration issues. The International Journal of Medical Robotics and Computer Assisted Surgery 2011, 7, 353 -360.
AMA StyleZion Tse, Yum Ji Chan, Henning Janssen, Abbi Hamed, Ian Young, Michael Lamperth. Piezoelectric actuator design for MR elastography: implementation and vibration issues. The International Journal of Medical Robotics and Computer Assisted Surgery. 2011; 7 (3):353-360.
Chicago/Turabian StyleZion Tse; Yum Ji Chan; Henning Janssen; Abbi Hamed; Ian Young; Michael Lamperth. 2011. "Piezoelectric actuator design for MR elastography: implementation and vibration issues." The International Journal of Medical Robotics and Computer Assisted Surgery 7, no. 3: 353-360.
Integral bladed disks (also known as blisks) are more widely used in modern aeroengine compressor designs because of the potential weight savings, but there are challenges in controlling the extreme vibration response levels in mistuned blisks, which are blisks with blades slightly different from each other. As blisks lack the uncertainty and variability of friction properties related to joints, the maximum vibration response level of a blisk test piece in operation can be predicted prior to installation. A previously proposed response-level prediction procedure for mistuned blisks is outlined, and its robustness is studied. A method of improving the results, given noisy experimental data, is proposed. Some of the issues discussed are validated by using experimental data.
Yum Ji Chan; D. J. Ewins. Prediction of Vibration Response Levels of Mistuned Integral Bladed Disks (Blisks): Robustness Studies. Journal of Turbomachinery 2011, 134, 044501 .
AMA StyleYum Ji Chan, D. J. Ewins. Prediction of Vibration Response Levels of Mistuned Integral Bladed Disks (Blisks): Robustness Studies. Journal of Turbomachinery. 2011; 134 (4):044501.
Chicago/Turabian StyleYum Ji Chan; D. J. Ewins. 2011. "Prediction of Vibration Response Levels of Mistuned Integral Bladed Disks (Blisks): Robustness Studies." Journal of Turbomachinery 134, no. 4: 044501.
It is known that small differences between nominally identical turbomachine blades, known as mistuning, can lead to significant variation in their vibration response levels. A commonly used term in mistuning studies called the “amplification factor” is clearly defined in this paper, and the high sensitivity of high-cycle-fatigue-related fatigue life to the level of vibration response levels is presented. Computer simulations are run to study the distribution of the amplification factor in three situations, namely, (i) bladed disks with damping mistuning, (ii) EO excitation of bladed disk modes in the veering region, and (iii) apparently tuned bladed disks. In addition to running simulations, the upper bound of the adjusted amplification factor in damping-mistuned bladed disks is derived theoretically.
Y.-J. Chan; D. J. Ewins. The Amplification of Vibration Response Levels of Mistuned Bladed Disks: Its Consequences and Its Distribution in Specific Situations. Journal of Engineering for Gas Turbines and Power 2011, 133, 102502 .
AMA StyleY.-J. Chan, D. J. Ewins. The Amplification of Vibration Response Levels of Mistuned Bladed Disks: Its Consequences and Its Distribution in Specific Situations. Journal of Engineering for Gas Turbines and Power. 2011; 133 (10):102502.
Chicago/Turabian StyleY.-J. Chan; D. J. Ewins. 2011. "The Amplification of Vibration Response Levels of Mistuned Bladed Disks: Its Consequences and Its Distribution in Specific Situations." Journal of Engineering for Gas Turbines and Power 133, no. 10: 102502.
The blade mistuning vibration problem refers to the often-dramatic scatter - and thus increase - in vibration response levels when the nominally-identical blades on a bladed disc are slightly different to each other. For example, when a set of blades have eigenfrequencies varying randomly with a 0.5% scatter about the design value, the vibration response of the individual blades can vary dramatically, with individual blades displaying increases of as much as 100-500% as compared with the level which would be observed on every blade in a perfect (i.e. “tuned”) bladed disc. As both the vibration response levels and variations of blades are physical in nature, the variation is called aleatory uncertainty or simply variability. Although the problem became a research topic over 40 years ago with more than 400 papers already published, industry still faces shortened fatigue lives due to these extreme vibration responses, with high levels of scatter and uncertainty as to the likely incidence of extreme response levels. In the paper, the blade mistuning problem is viewed as a robust design problem, where the maximum blade response on the bladed disc is the robustness. The dependence of robustness on selected design parameters is discussed, and a procedure for managing the consequences of blade mistuning on manufactured bladed discs, rather than trying to eliminate the problem, is presented.
Y.-J. Chan; D. J. Ewins. The application of robust design strategies on managing the uncertainty and variability issues of the blade mistuning vibration problem. IUTAM Symposium on Multiscale Modelling of Fatigue, Damage and Fracture in Smart Materials 2011, 443 -456.
AMA StyleY.-J. Chan, D. J. Ewins. The application of robust design strategies on managing the uncertainty and variability issues of the blade mistuning vibration problem. IUTAM Symposium on Multiscale Modelling of Fatigue, Damage and Fracture in Smart Materials. 2011; ():443-456.
Chicago/Turabian StyleY.-J. Chan; D. J. Ewins. 2011. "The application of robust design strategies on managing the uncertainty and variability issues of the blade mistuning vibration problem." IUTAM Symposium on Multiscale Modelling of Fatigue, Damage and Fracture in Smart Materials , no. : 443-456.
Yum Ji Chan; D.J. Ewins. Management of the variability of vibration response levels in mistuned bladed discs using robust design concepts. Part 2: Tolerance design. Mechanical Systems and Signal Processing 2010, 24, 2792 -2806.
AMA StyleYum Ji Chan, D.J. Ewins. Management of the variability of vibration response levels in mistuned bladed discs using robust design concepts. Part 2: Tolerance design. Mechanical Systems and Signal Processing. 2010; 24 (8):2792-2806.
Chicago/Turabian StyleYum Ji Chan; D.J. Ewins. 2010. "Management of the variability of vibration response levels in mistuned bladed discs using robust design concepts. Part 2: Tolerance design." Mechanical Systems and Signal Processing 24, no. 8: 2792-2806.
Y.-J. Chan; D.J. Ewins. Management of the variability of vibration response levels in mistuned bladed discs using robust design concepts. Part 1: Parameter design. Mechanical Systems and Signal Processing 2010, 24, 2777 -2791.
AMA StyleY.-J. Chan, D.J. Ewins. Management of the variability of vibration response levels in mistuned bladed discs using robust design concepts. Part 1: Parameter design. Mechanical Systems and Signal Processing. 2010; 24 (8):2777-2791.
Chicago/Turabian StyleY.-J. Chan; D.J. Ewins. 2010. "Management of the variability of vibration response levels in mistuned bladed discs using robust design concepts. Part 1: Parameter design." Mechanical Systems and Signal Processing 24, no. 8: 2777-2791.
A new procedure is developed to find the probabilities of extremely high amplification factors in mistuned bladed disk vibration levels, typical of events which occur rarely. While a rough estimate can be made by curve-fitting the distribution function generated in a Monte Carlo simulation, the procedure presented here can determine a much more accurate upper bound and the probabilities of amplification factors near to that bound. The procedure comprises an optimization analysis based on the conjugate gradient method and a stochastic simulation using the importance sampling method. Two examples are provided to illustrate the efficiency of the procedure, which can be 2 or 3 orders of magnitude more efficient than Monte Carlo simulations.
Yum Ji Chan; D. J. Ewins. A Comprehensive Procedure to Estimate the Probability of Extreme Vibration Levels Due to Mistuning. Journal of Engineering for Gas Turbines and Power 2010, 132, 112505 .
AMA StyleYum Ji Chan, D. J. Ewins. A Comprehensive Procedure to Estimate the Probability of Extreme Vibration Levels Due to Mistuning. Journal of Engineering for Gas Turbines and Power. 2010; 132 (11):112505.
Chicago/Turabian StyleYum Ji Chan; D. J. Ewins. 2010. "A Comprehensive Procedure to Estimate the Probability of Extreme Vibration Levels Due to Mistuning." Journal of Engineering for Gas Turbines and Power 132, no. 11: 112505.
A set of new procedures is developed to find the probabilities of extremely high amplification factors in mistuned bladed disk vibration levels, which rarely occur. While a rough estimate can be made by curve-fitting the distribution function, the method presented here can determine an accurate upper bound and the probabilities of amplification factors near to that bound. Two examples are provided to illustrate the efficiency of the method, which can be 2 or 3 orders of magnitudes more efficient than Monte Carlo simulations.
Yum Ji Chan; D. J. Ewins. A Comprehensive Set of Procedures to Estimate the Probability of Extreme Vibration Levels Due to Mistuning. Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Controls, Diagnostics and Instrumentation; Education; Electric Power; Awards and Honors 2009, 211 -219.
AMA StyleYum Ji Chan, D. J. Ewins. A Comprehensive Set of Procedures to Estimate the Probability of Extreme Vibration Levels Due to Mistuning. Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Controls, Diagnostics and Instrumentation; Education; Electric Power; Awards and Honors. 2009; ():211-219.
Chicago/Turabian StyleYum Ji Chan; D. J. Ewins. 2009. "A Comprehensive Set of Procedures to Estimate the Probability of Extreme Vibration Levels Due to Mistuning." Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Controls, Diagnostics and Instrumentation; Education; Electric Power; Awards and Honors , no. : 211-219.