bluuebunny/crossref_metadata_2025 huggingface dataset:
Scale-Independent Model on Gravitational Dispersion of Particulate Suspension in Fractal Channels
Authors: Kurose Yudai , Ishizawa Kanami , Harada Shusaku
Published: July 2018

Gravitational dispersion of solid particles in a liquid-filled channel can be seen in various engineering processes. However, it is known that the dispersion behavior is greatly influenced by properties of suspension and channel geometry. In this study, the gravitational dispersion behaviors of solid particles into a liquid-filled complex channel are examined experimentally. Particularly we focus on the dispersion of particles during the collective settling which occurs when the particle size is small and the concentration is large. In such conditions, the suspended particles form a finger-like blob and they behave as a continuum which is immiscible to surrounding fluid. We experimentally observed the collective settling in a fractal-shaped transparent channel. We also developed a scale-independent model on temporal change of the occupancy ratio of suspended particles in channels having fractal characteristics.
Flow Characteristics on Fluidized Powder Conveying in a Horizontal Rectangular Channel
Authors: Ogata Koichiro , Yamashita Sumito , Hirose Tomoya
Published: July 2018

This study experimentally examined the dense phase pneumatic conveying in a horizontal rectangular channel using the fluidizing air. The powder used is PVC belong to Geldart A particle, where the mean diameter is 151μm, the particle density is 1382kg/m3 and the minimum fluidizing velocity is 9.0mm/s. As the experimental conditions, the fluidizing velocity at the bottom of a vessel and the horizontal channel has been changed. Also, the mass of transported powder, the supply air pressure and the height of powder bed inside a vessel were measured. In the case of PVC, we confirmed the flow characteristics of the powder conveying and air pressure. Further, we found that the fluidizing air to the bottom of a vessel was required to the powder conveying of this system, and that the fluidizing velocity at the horizontal channel needs to be larger than the minimum fluidizing velocity. These results were also obtained on the previous study when two kinds of glass bead was used. The mass flow rate and solid loading ratio were estimated by the measured data of the mass of transported powder. In addition, these results were compared with the conveying characteristic of two kinds of glass beads belongs to Geldart A and B particle. As a result, the mass flow rate and solid loading ratio of PVC were smaller than that of two kinds of glass beads.
Measurement and Analysis on Flow Structure of Inertial Particle Separator
Authors: Wang Tong , Sun Liangliang , Gu Chuangang
Published: July 2018

With relatively less flow losses, Inertial Particle Separator (IPS) is recommended to scavenge the sand or dust from the main flow into the engines. The rectangular cross section IPS model was measured by PIV technique with different inlet flow rate and scavenge ratio. It was found that the recirculation region was varied by the influence of the wall. The numerical method was verified by the similar velocity profiles with the testing results. The annular inlet IPS model was analyzed by the numerical method. The flow field in the annular inlet IPS was quite different from that in the rectangular cross section IPS model. The velocity profile and the total pressure drop were both different. It suggested that the annular inlet IPS model should be analyzed and be optimized to improve the real IPS performance.
Study on Drug Powder Acceleration in a Micro Shock Tube
Authors: Zhang Guang , Kim Heuy Dong , Jin Yingzi , Setoguchi Toshiaki
Published: July 2018

Recently, needle-free drug delivery systems have been widely used for delivering drug particles into human body without any external needles in medical fields. Drug powders should be accelerated to obtain enough momentum to be delivered into the suitable layer of the skin. This is achieved by accelerating drug particles in a Contoured Shock Tube (CST) which consists of a micro shock tube and an expanded supersonic nozzle. Shock wave happens in micro shock tube, and supersonic flow with particles is induced by the shock wave and accelerated in the expanded nozzle. Even though micro shock tubes have been studied for a long time, detailed experimental data for shock waves and particle-gas flows are sparse to date and it is very important to investigate the complicated particle-gas flow fields for practical applications. In the present study, Particle Tracking Velocimetry (PTV) was used to measure the average velocity of the gas-particle flow behind the propagating shock wave. Unsteady flow properties and shock wave propagation were analyzed by this instantaneous particle velocity fields. Numerical simulation was performed with unsteady compressible Naver-stokes equations which were solved by using a fully implicit finite volume scheme. Discrete Phase Model (DPM) has been used for simulating particle-gas two-phase flows. Different particle diameter and density were performed in present numerical studies. Unsteady particle-gas flow characteristics and shock wave propagation have been studied and analyzed in details in present micro shock tube model.
A Cost-Effective Search of Collision Pairs in Lagrangian Particle Tracking Method
Authors: Lin Jian-Hung , Chang Keh-Chin
Published: July 2018

In the simulation of particle-laden flows, in which the inter-particle collisions have to be considered, using the Eulerian-Lagrangian approach, it is agreed that the search of collision pairs based on the deterministic particle tracking method together with the binary-collision, hard-sphere model is a time consuming job in the computational procedure particularly for the flow laden with a remarkably high number density of particles. A cost-effective algorithm for the particle tracking processes which include solving the equations of motion, searching the collision pairs, and updating the list of neighboring particles’ indices is developed. It is demonstrated in the turbulent, fully developed, particle-laden channel flows that the computational expenditure required for completing the particle tracking processes in a given Lagrangian time step can be optimally made with an approximately linear proportionally to the total number of particles (NPT) by setting the number of Lagrangian cells (Ncell) for computation in accordance with the criterion of NPT / Ncell = O(10°).
Numerical Investigation on Performance of Contra-Rotating Axial Flow Pump With Different Rear Rotor Design
Authors: Honda Hironori , Cao Linlin , Watanabe Satoshi , Tsuda Shin-ichi , Furukawa Akinori
Published: July 2018

In the industrial fields, the development of higher specific speed pumps is demanded with the importance of energy and resource savings. We believe that contra-rotating axial flow pumps with a rear rotor rotating opposite side to a front rotor offer a good solution against it. This type of the pump shows better performance and more compact machine size relatively than the conventional rotor-stator type under the same design specifications. In the present paper, the effect of rear-rotor speed on the hydraulic efficiency of contra-rotating axial flow pump is investigated by using numerical simulations. We re-designed several rear rotors with the different rotational speeds of Nr=600, 900 1123min−1 determined based on one-dimensional stream-tube theory with considering the momentum conservation laws. The evaluation of their performance is carried out by numerical simulations using ANSYS CFX. According to simulation results, it is found that the reduced rear-rotor speed concept brings about preferable performance with the increased efficiency. However, in the passage of re-designed rear rotors, secondary flow is clearly observed at the corner of hub and blade suction surfaces, indicating the possibility of further performance improvement with more appropriate blade design.
Cavitation Flow Structure and Unsteady Pressure Pulsation Around a Hydrofoil
Authors: Ni Dan , Yang Minguan , Li Zhong , Zhang Ning , Gao Bo
Published: July 2018

The present work is an original study of the flow induced vibration, cavitation structures and cavitation induced pressure pulsation characteristics around a typical hydrofoil named 791, which is widely applied in the axial flow pump.

From the vibration experiment of the hydrofoil at various operating conditions, it is clear that at low frequency band, with Reynolds number increasing, vibration energy first experiences a stable slightly increasing tendency, and then decreases rapidly, finally rises steeply again. Besides, according to the results of several positive incidence angles, it is observed that vibration energy usually achieves a local minimum level at a certain positive incidence angle falling into the range of 2° to 4°.

Based on results obtained from the detached eddy simulation (DES) turbulent model, full developing process of cavitation stages including, incipient cavitation, sheet cavitation and cloud cavitation could be captured and easily identified. It is found that pressure spectra in accordance with different cavitation stages show great discrepancy. In the stage of incipient cavitation and cloud cavitation, predominant components in pressure spectra are caused by the cyclical evolution of the main cavity and the periodic variation of the small vacuoles shedding at the span-wise outer edge of the hydrofoil. However, in sheet cavitation stage, the pronounced excitation frequencies are generated by cyclical evolution of the main cavity and cavity shedding from both sides of the U-shaped cavitation structure. Pressure pulsation amplitude is pretty small at the cavity stable adhesion region. But the amplitude of vacuoles shedding from the hydrofoil is much larger than main cavity adhesion region at these three stages.
Adaptive Blade Systems for Increased Operating Range of a Turbomachine
Authors: Hammer Steffen , Peter Julija , Thamsen Paul Uwe , Meyer Robert , Phan Dat Tien , Liebich Robert
Published: July 2018

At the Department of Fluid System Dynamics, within the Collaborative Research Centre 1029 funded by the German Research Foundation (DFG), the influence of the rotor-stator interaction by four adaptive blade systems is studied. Using the adjustable stator vane, moveable stator vane, Gurney flaps and piezo actuators the flow losses are decreased by reducing the incidence. Therefore experimental investigations are carried out in a cascade, integrated in a water channel by means of the High-Speed PIV and time-resolved pressure measurement. The presented investigations show an enlargement of the operating range by using Gurney flaps in a rotating system and the adjustable front flap.
PIV Measurements in Diffuser of the Radial Pump
Authors: Jung Sung Yong , Min Young Uk , Lee Kyung Lok
Published: July 2018

The performance characteristics of the radial pump commonly used as a multistage (8 or 10 stage) pump have been investigated experimentally. Due to the complex three-dimensional geometries, the hydraulic performance of multistage pumps is closely related to the internal flows in diffuser and return vanes. In order to investigate the flow characteristics in these regions by Particle Image Velocimetry (PIV) technique, a transparent pump is designed. A 532 nm continuous laser and a high-speed camera are used as a light source and an image acquisition device, respectively. The velocity field information in a diffuser of the radial pump is successfully obtained by two-dimensional PIV measurements at various operating conditions.
Numerical and Experimental Study of Flexural Wave Band Gaps of Periodical Locally-Resonant Beams With Suspended Separated Force and Moment Resonators
Authors: Lv Hangyuan , Wang Michael Yu
Published: July 2018

In this paper, flexural vibration in a locally-resonant (LR) beam with periodically attached separated force and moment beam-like resonators is investigated theoretically and experimentally. The relationship between the distance parameter and the band structure of an Euler-Bernoulli beam with proposed locally resonators is provided using the transfer matrix theory. The frequency response functions of finite periodic systems are calculated with the finite element method over a range of different parameters of the resonators. Finally, we use LR beam specimens with separated force and moment resonators mounted on a free-free host beam for experimental measurements of the vibration transmittance. The experimental results show a good agreement with those of the theoretical and numerical except some small discrepancies at high frequencies. Our study confirms that the bandwidth of band-gaps will become wider with the increasing of the distance parameter until it reaches its peak, which provides an effective way for LR periodic structures with resonators to obtain broad band-gaps in low-frequency range, and makes the structure had potential applications in the control of vibration and wave propagation in flexural beams.
A New Method for Simultaneous Optimization of a Structure With Active and Passive Control Variables
Authors: Jung Ui-Jin , Park Gyung-Jin
Published: July 2018

An optimization method is proposed for the simultaneous design of structural and control systems using the equivalent static loads. The two structural and control systems are not completely independent and need to be considered in a unified fashion. Furthermore, an integrated system design is unavoidable to exhibit a good performance in the time domain. The analysis for the integrated system is conducted for the transient-state in a dynamic manner. The constraints for the structural and control systems are defined in the time domain as well. Therefore, a physically small scale problem in structural analysis easily becomes quite a large scale in an optimization problem. A new equivalent static loads (ESLs) method, which deals with the structural design variables as well as the control design variables, is proposed to solve physically large scale problems. A finite element dynamic equation is defined with control forces and a dynamic response optimization problem is formulated. Linear static response optimization is carried out with the ESLs. The control forces for the linear static response optimization are considered as design variables. Shape variables are utilized to handle the design variables for the control forces. Several examples are solved to validate the proposed method.
Time Delay Consideration on a New Active Control Algorithm
Authors: Yanik Arcan , Aldemir Unal , Bakioglu Mehmet
Published: July 2018

In the area of active control of structures, time delay consideration is an important parameter which must be taken into consideration for realistic numerical models. In this research, the performance of a new active control algorithm for several time delays under two different earthquake excitations was investigated numerically. The proposed performance index does not require a priori knowledge of seismic input and the solution of the nonlinear matrix Riccati equation to apply the control forces [1,2]. The proposed control introduces the seismic energy term into the performance index so that the mechanical energy of the structure, the control and the seismic energies are considered simultaneously in the minimization procedure, which yields cross terms in the performance index. A two story shear frame was modelled in Matlab-Simulink considering time-delay. A fully active tendon controller system is implemented to the system. 0–50 ms time delay was considered in the dynamic analysis. The change in the time delay steps was 5 ms. The effect of time-delay was investigated under synthetic and Erzincan NS (1995;95 Erzincan station) earthquakes. Kanai-Tajimi power spectral density function was used to generate synthetic earthquake motion. The behavior of the proposed control with time delay considerations is compared with the uncontrolled conventional structure.
Design Optimization of Beams With Multi-Layers of Corrugations
Authors: Cheng W. N. , Cheng C. C.
Published: July 2018

Optimal designs of beams with multi-layers of corrugations are introduced in this paper. The dynamic characteristic of corrugated structures is investigated firstly using the impedance modeling technique. The dynamic response of a beam with layers of corrugations is formulated by dividing a corrugated beam into two kinds of structural segments: one, the corrugation modeled as a curved beam using finite element method and the other, the liner treated as a straight beam formulated analytically. Then the frequency equation is derived by assembling the impedance of each structure segment based on conditions of force equilibrium and velocity compatibility. The accuracy of the impedance modeling technique are compared to different existing methods, e.g. FEM, Guyan reduction, improved reduction system (IRS), improved reduction system (DIRS), and iterative improved reduction system (IIRS). Finally, examples of optimal design of corrugated beams are presented. Results further show that with an optimal number of corrugated layers and optimal thickness of liner and medium of each layer, the corrugated beam has a desirable dynamic characteristic, e.g. the first bending natural frequency may increase 40% as compared to that of the original design.
Bifurcation Analysis of a Spacecraft Structure Using the Harmonic Balance Method
Authors: Detroux T. , Renson L. , Masset L. , Noël J. P. , Kerschen G.
Published: July 2018

The harmonic balance (HB) method has been widely used in the past few years, as a numerical tool for the study of nonlinear models. However, in its classical formulation the HB method is limited to the approximation of periodic solutions. The present paper proposes to extend the method to the detection and tracking of bifurcations in the codimension-2 system parameters space. To validate the methodology, the forced response of a real spacecraft is examined. The paper first provides some numerical evidence of the presence of quasiperiodic oscillations and isolated solutions. It then demonstrates how the tracking of Neimark-Sacker and fold bifurcations can help get a deeper understanding of these attractors.
Comparative Study of Magnetorheological Damper Models for Force Tracking
Authors: Strydom Anria , Scholtz Werner , Els Schalk
Published: July 2018

Magnetorheological (MR) dampers are controllable semi-active dampers capable of providing a range of continuous damping settings. MR dampers are often incorporated in suspension systems of vehicles where conflicting damping characteristics are required for favorable ride comfort and handling behavior. For control applications the damper controller determines the required damper current in order to track the desired damping force, often by using a suitable MR damper model. In order to utilise the fast switching time capability of MR dampers, a model that can be used to directly calculate damper current is desired. Unfortunately few such models exist and other methods, which often negatively affect the computational efficiency of the model, need to be used when implementing these models. In this paper a selection of MR damper models are developed and evaluated for both accuracy and computational efficiency while tracking a desired damping force. The Kwok model is identified as a suitable candidate for the intended suspension control application.
Geometric Modeling and Robust Control of a Gyroscopic System
Authors: Colón Diego , Angelico Bruno A. , Toriumi Fabio Y. , Liduário Paulo U. M. , Balthazar José M.
Published: July 2018

Gyroscopic systems are multi-body systems which present coupled three dimensional motion. The configuration space and the state space are differentiable manifolds, and differential geometric concepts are frequently useful in the process of modeling. This paper deals with a Control Moment Gyroscope (CMG), which is not asymptotically stable, so it needs a stabilizing control law. We apply a new methodology of modeling kinematics and dynamics of rigid multi-body systems, based in the concept of Cartan’s connection and covariant derivative. The systems has two inputs (torques) and two outputs (angles) that will be controlled by a robust linear closed-loop control technique (LQG/LTR). Experimental results are presented in order to validate the proposal.
Noise Control in a Small Household Appliance by Means of Experimental Analysis of Vibration Paths
Authors: Doria Alberto , Florian Paolo , Franzon Floriano
Published: July 2018

Automatic machines for the preparation of coffee from the bean to the cup have now a wide diffusion among coffee amateurs. Since these machines are usually installed at home and in offices, low noise emission is an important design requirement. These small appliances are complex dynamic systems from the point of view of noise and vibration control, because they include some electric motors, a transmission, a grinder, some mechanisms, a suspension system, cavities and radiating panels. In the last decades various methods for the experimental study of vibrations have been developed in the aerospace and automotive fields, like transfer path analysis and modal testing. The first section of this paper describes the potentialities and the limits of these methods, when a small appliance (maximum size 300 mm) has to be tested in an industrial environment. Then a specific method for the study of the flux of energy from the motor-grinder group to the acoustic field is presented. It is based on the physical variation in the stiffness of the resilient connections, which is carried out with the design of experiments approach. The noise spectra measured outside the machine and the vibration spectra measured in critical points inside the machine are analyzed with correlation techniques. Results show that the resilient mounts are effective, but one transmission path influences noise transmission more than the others, mainly owing to the asymmetrical construction of the motor-grinder group and of the appliance structure. Suggestions for improved noise control are given.
Parametric Resonance of MEMS Circular Plate Resonators
Authors: Caruntu Dumitru I. , Oyervides Reynaldo
Published: July 2018

This paper investigates parametric resonance of electrostatically actuated MEMS circular plates for resonator sensing applications. The system consists of a clamped circular elastic plate over a ground plate. Soft AC voltage of frequency near natural frequency of the plate gives the electrostatic force that leads the elastic plate into vibration, more specifically into parametric resonance which can be used afterwards for biosensing purposes. Frequency response and corresponding bifurcations are reported. The effects of damping and voltage are predicted.
Complex Modal Analysis of Non-Modally Damped Wind Turbine Blade
Authors: Xing Xing , Feeny Brian F.
Published: July 2018

The vibration model of a wind turbine blade can be approximated as a rotating pretwisted nonsymmetric beam, with damping and gravitational and aeroelastic loading. In this work, the out-of-plane (flapwise) and in-plane (edgewise) motion are examined with simple aeroelastic damping effects. The aeroelastic model used is based on a simple quasisteady blade-element airfoil theory. The linear velocity dependent terms are isolated and incorporated into the damping, which then turns out to be generally non modal (non Caughey). The complex modes are analyzed while neglecting the effects of rotation to single out the effect that aerodynamic damping may have on the modes. The analysis is done by first discretizing the system with assumed modes, and then solving an eigenvalue problem for the state-variable description of the discretized system. The eigen modes are recombined with the assumed mode functions to approximate the modes in the original system. The analysis is performed on the National Renewable Energy Laboratory (NREL) 23-meter blade, the NREL 63-meter blade, and the Sandia 100-meter blade. The effects of nonproportional damping are seen to become more significant as the blade size increases. The results provide some experience for the validity of making modal damping assumptions in blade analyses.
A Multimode Wave-Form Command Shaping Control Applied on Double Pendulum
Authors: Alhazza Khaled A. , Masoud Ziyad N. , Alhazza Abdulsalam
Published: July 2018

In this work, a command shaping technique is used to reduce residual vibrations of rest-to-rest maneuvers of double pendulums. The proposed command shaper can produce a command shaper without the exact mathematical model; it is only dependent on the system natural frequencies. Furthermore, the proposed shaper has independent maneuvering time. Unlike most command shaper for multimode systems, the proposed technique has known formulas for its parameters. Both simulations and experiments are used to validate the shaper concept. Experiment and simulation results, through different examples, showed great shaper performances.
Reversible Passive Bandgap Reconfiguration Using an Excitation Dependent On-Site Restoring Force
Authors: Bernard Brian P. , Arvidsson Kim
Published: July 2018

By applying an excitation dependent, on-site restoring force to oscillators in a uniform one-dimensional chain with nearest neighbor coupling, this paper demonstrates the feasibility of reversible passive bandgap reconfiguration. Waveguide devices are most commonly tuned using active controls, component replacement, or by manually varying design parameters. Recent studies on wave propagation have pursued passive controls, where high amplitude environmental excitation triggers a potential well escape in an asymmetric, bi-stable system, automatically changing its linear spectra without user interaction. Current designs, however, do not return to their initial state upon later excitation amplitude reduction, instead requiring manual reset for continued operation. In order to allow fully autonomous function, a passively reconfigurable system must also be designed to return to its low amplitude state after environmental excitation amplitude decreases. This paper proposes a system in which reversible bifurcations are observed by introducing an excitation dependent on-site stiffness. Instead of a fixed, bi-stable potential energy curve, the oscillators have a single mono-stable curve at low energy levels and a different mono-stable curve with its own distinct linear spectrum at high energy levels. Numerical simulations are provided to demonstrate system transitions from propagation zone to attenuation zone behavior, and back, when subjected to increasing and decreasing excitation amplitudes.
Helicopter Ground Resonance Investigation With Dissimilar Nonlinear Lead-Lag Dampers
Authors: Tamer Aykut , Masarati Pierangelo
Published: July 2018

This work describes the analysis of helicopter ground resonance when nonlinearity and non-isotropy of the problem are taken into account. Ground resonance is a dynamic instability caused by the interaction between the rotor and the airframe of a helicopter. Sources of nonlinearity can be geometrical (finite blade lead-lag motion) and constitutive (hydraulic lead-lag dampers and shock absorbers). Standard methods use special coordinate transformations that make it possible to cast the problem in linear, time invariant form when considering small oscillations of an isotropic rotor about a reference solution. However, potential non-isotropy of the rotor (e.g. resulting from degraded performance of lead-lag dampers) may turn the problem into linear, time periodic. In such cases, the Floquet-Lyapunov method is normally used to study the stability of the coupled system. In this work the problem is investigated using Lyapunov Characteristic Exponents (LCE). The analysis shows that in some cases, characterized by a marked contribution of the nonlinearity of the blade lead-lag dampers, the problem assumes a nearly chaotic behavior. The stability of the system is investigated, and the sensitivity of the LCEs with respect to system parameters is determined, in an attempt to provide a consistent analysis framework and useful design guidelines.
Signal Processing Methods for Determining the Properties of Bolted Joints
Authors: Goyder Hugh
Published: July 2018

If a structure containing bolted joints is set into vibration and the subsequent motion measured it may be possible to determine some properties of the structure and the joints. However, it is not generally straightforward to interpret the decaying vibration signals and considerable signal processing may be necessary. Typically the vibration is nonlinear and this must be taken into account. Three methods for data analysis are investigated here: filtering time histories, working with short Fourier transforms and the use of empirical mode decompositions. Some progress is made with the first two but the third is disappointing but full of promise. The general scope of the objectives is to obtain properties such as frequency and damping that are changing in time. One of the key difficulties is that several nonlinear resonances are superimposed in a general decaying time history. Extracting the one required from the others is the main signal processing task.
Optimal Sensor Placement Using Chaotic Monkey Search Algorithm
Authors: Zhang Fuli , Brezhneva Olga , Shukla Amit
Published: July 2018

The optimal sensor placement (OSP) problem is integral to modern large scale structures for their health monitoring. Evolutionary algorithms for the OSP problem are attractive as they can result in global optima without gradient information. In this paper, a modification of the Monkey Algorithm with a chaotic search strategy and adaptive parameters is proposed. It includes chaotic initialization, variable search step length, and adaptive watching time.

The performance of the proposed chaotic Monkey Algorithm (cMA) is compared with the original Monkey Algorithm. Convergence property of cMA is established. The proposed method is applied to an optimal sensor placement problem for structural health monitoring. The OSP problem is solved for a mass-spring-damper system and then for a model of the I-40 bridge developed by the Los Alamos National Laboratory. Numerical results demonstrate that the proposed Chaotic Monkey Algorithm has capability of solving mixed-variable optimization problems and that it performs better than the originally proposed Monkey algorithm. Finally, nonparametric uncertainty modeling is used to evaluate variability in a model and its effect on the optimal sensor placement.
Multi-Objective Optimal Design and Validation of Sliding Mode Control
Authors: Qin Zhi-Chang , Xiong Fu-Rui , Ding Qian , Hernández Carlos , Fernandez Jesús , Schütze Oliver , Sun Jian-Qiao
Published: July 2018

This paper presents a study of multi-objective optimal design of a slide mode control for an under-actuated nonlinear system with the parallel simple cell mapping method. The multi-objective optimal design of the slide mode control involves 6 design parameters and 5 objective functions. The parallel simple cell mapping method finds the Pareto set and Pareto front efficiently. The parallel computing is done on a graphic processing unit (GPU). Numerical simulations and experiments are done on a rotary flexible arm system. The results show that the proposed multi-objective designs are quite effective.
An Improved Variational Vibration Model of Damaged Beams to Obtain an Unconditionally Numerical Stable Model
Authors: Alzahrani Mahmoud A. , Choi Seung-Kyum
Published: July 2018

Fault detection methods are significant in health monitoring of critical system components, including aerospace applications. Failure in such systems is unacceptable, even though engineers try to achieve very low failure probability in these systems. The ability to accurately model and analyze the characteristics of such systems would reduce the rates of false positives and missed detections in structural health monitoring. Previously, a detection model was developed to investigate the effects of combined impact of geometrical variations of machining errors and crack presence in beams. The model utilized the Leap Frog finite difference method, which had a restrictive condition on stability of the numerical method. This restriction would show to be critical with materials with high modulus and low density values. The proposed work will overcome the drawback of the current detection model by utilizing other finite difference methods to remove or relax the stability condition of the method; namely, the Weighted Average method and Du Fort-Frankel method. The presented result clearly shows that the Theta method could be used to obtain an unconditionally stable finite difference model with high accuracy. It is also observed that the result from the Du Fort-Frankel method is still conditionally stable, but the stability condition is more relaxed compared to the Leap Frog method. The results obtained from the improved model show good agreement with the example in the literature. The improved model is also applied to investigate a cantilevered beam with the presence of cracks and geometrical variations.
Predicting the Frequency of the Rotor Whirl Excited by Semi-Floating Ring Bearing
Authors: Liang Feng , Xu Quanyong , Zhou Ming
Published: July 2018

The semi-floating ring bearings (SFRBs) are developed to attenuate rotor vibrations by providing damping, but the subsynchronous oscillations cannot be avoided. The subsynchronous oscillations of the rotor are the self-excited whirl motions for the instability of the oil films. Their frequencies are usually less than the half of the rotor speed, but difficult to be predicted because the effects of SFRB’s parameters on the subsynchronous oscillation frequency are not clear. In this paper, an analytical expression is proposed to estimate the subsynchronous whirl frequency of SFRB. To verify the accuracy of the predicting expression, the two-dimensional nonlinear responses of the SFRB are calculated by the Finite Element (FE) method. After confirming the accuracy, the predicting expression is generalized to the rotor-SFRBs (flexible rotor supported by SFRBs). The nonlinear responses of rotor-SFRBs are simulated. Two typical subsynchronous oscillations excited by the two SFRBs respectively are observed, and their frequencies coincide the prediction of the expression as expected.
Integrated Approach for Vibration-Based Condition Monitoring of Rotating Machines
Authors: Sinha Jyoti K.
Published: July 2018

Conventional Vibration-based Condition Monitoring (VCM) is well known and well accepted in industries to identify the fault(s), if any, in rotating machine since decades. However over the last 3 decades, significant advancement in both computational and instrumentation technologies has been noticed which resulted in number of research studies to find the alternate and efficient methods for fault(s) diagnosis. But most of the research studies may not be leading to an Integrated Modern VCM (IMVCM). It may be because of mainly 2 reasons; (a) the recent proposed methods in the literature are based on numerically simulated studies and a very limited experimental studies and (b) none of the recent studies applied on all kind of faults. In this paper, a summary of a couple of methods proposed and published earlier by author to meet the requirement of the IMVCM is presented.
Nonlinear Energy Sink With a Non-Traditional Kind of Nonlinear Restoring Force
Authors: Al-Shudeifat Mohammad A.
Published: July 2018

Enhanced nonlinear energy sink (NES) is addressed here by employing a non-traditional kind of a nonlinear restoring force. The usual nonlinear coupling element between the NES and the linear oscillator (LO) in the literature generates essentially nonlinear restoring force between the NES and the LO. Unlike Type I NES, here the nonlinear coupling force has varying components during the oscillation which appear in closed loops under the effect of damping terms. This NES attachment with the LO rapidly absorbs and immediately dissipates significant portion of the initial energy induced into the LO through a strong resonance capture between the NES and LO responses. The proposed design could also be promising for energy harvesting purposes. The obtained results by numerical simulation show that employing this type of nonlinear restoring force for passive targeted energy transfer (TET) is more promising than some other types of NESs in which purely cubic stiffness restoring forces have been incorporated.
High-Resolution Deformation Measurement System for Fast Rotating Tires
Authors: Takami Kuya , Furukawa Tomonari
Published: July 2018

This paper presents a high-resolution measurement system for fast-rotating tires. The developed system is compatible with and can be integrated with the tire testing machines used in industry research facilities. A field programmable gate array controller with a high clock rate triggers a short duration strobe flash capturing a clear instant image of a rotating tire based on an encoder reference signal. Since the rotation of a tire on a testing machine is periodic, the system can effectively capture the deformation of a rotating tire at a high equivalent sampling frequency. The Complementary Metal-Oxide-Semiconductor (CMOS)-based high-resolution low-cost system can be employed to measure tire deformation associated with sound generation. This was implemented by synchronously measuring sound with a microphone array. The validity of the developed system was investigated by experimental evaluation. Then, the system was implemented at the tire testing facility, and tested by rotating a tire at a drum speed up to 100 km/h and capturing images at every 0.025 degree rotation.
Efficient and Sensitive Energy Harvesting Using Piezoelectric MEMS Compliant Mechanisms
Authors: Ma Xiaokun , Yeo Hong Goo , Rahn Christopher D. , Trolier-McKinstry Susan
Published: July 2018

Piezoelectric energy harvesters typically perform poorly in the low frequency, low amplitude, and intermittent excitation environment of human movement. In this paper, a piezoelectric compliant mechanism (PCM) energy harvester is designed, modeled, and analyzed that consists of a PZT unimorph clamped at the base and attached to a compliant mechanism at the tip. The compliant mechanism has two flexures that amplify the tip displacement to produce large motion of a proof mass and a low frequency first mode with an efficient (nearly quadratic) shape. The compliant mechanism is fabricated as a separate, relatively rigid frame with flexure hinges, simplifying the fabrication process and surrounding and protecting the PZT unimorph. The bridge structure of the PCM also introduces an axial tensioning nonlinearity that self-limits the response to large amplitude impacts, improving the robustness of the device. Comparing the time domain performance based on realistic wrist acceleration data, the PCM produces 6 times more average power than a proof mass cantilever with the same unimorph area and natural frequency.
Modeling Heart Rate Dynamics in Response to Changes in Exercise Intensity
Authors: Mazzoleni Michael J. , Battaglini Claudio L. , Mann Brian P.
Published: July 2018

This paper develops a nonlinear mathematical model to describe the heart rate response of an individual during cycling. The model is able to account for the fluctuations of an individual’s heart rate while they participate in exercise that varies in intensity. A method for estimating the model parameters using a genetic algorithm is presented and implemented, and the results show good agreement between the actual parameter values and the estimated values when tested using synthetic data.
Analysis of Magnetic Forces in Two-Dimensional Space With Applications for the Tuning of Vibration Energy Harvesting Devices
Authors: Dong Lin , Fisher Frank T.
Published: July 2018

Vibration-based energy harvesting is a process by which ambient vibrations are converted to electrical energy, and is of interest for supplementing or replacing the batteries of individual nodes comprising wireless sensor networks among other applications. Generally, it is desired to match the resonant frequencies of the device with the primary ambient vibration frequencies for optimal energy harvesting performance. While previous work has demonstrated the use of magnetic forces to tune the resonant frequencies of vibrating energy harvesting structures, such efforts have been limited to one-dimensional analyzes. Here frequency tuning is realized by applying magnetic forces to the device in two-dimensional space, such that the resulting magnetic force has both horizontal and vertical components. In the case of a cantilever beam, the transverse force contributes to the transverse stiffness of the system while the axial force contributes to a change in the geometric stiffness of the beam. The effective resonant frequency of the device is then a function of the contributions of the original stiffness of the beam and the two additional stiffness components introduced by the presence of the magnet in 2D space. The simulation results from a COMSOL magnetostatics 3D model agree well with an analytical model describing the magnetic forces between the magnets as a function of location. Such 2D magnetic stiffness tuning approaches may be useful in applications where space constraints impact the available design space of the energy harvester.
Generation and Optimization of Traveling Vibrating Waves in Self-Assembling Swimming Smart Boxes
Authors: Bani-Hani Muath , Borazjani Iman , Esfahani Ehsan T. , Krovi Venkat , Karami M. Amin
Published: July 2018

This paper presents vibration analysis and structural optimization of a self-assembled structure for swimming. The third mode shape of the structure in the longitudinal direction resembles the body waveform of a swimming eel fish. At the final destination, the box self-assembles using shape memory alloys. MFCs (Piezoelectric Micro Fiber Composites) are actuated at the fundamental natural frequency of the structure. This excites the primary mode of resonance. We optimize the thickness of the panels and the stiffness of the joints to most efficiently generate the swimming waveforms that resembles the body waveform of eel. Traveling wave is generated using two piezoelectric batches actuators bonded on the first and fourth segments of the beams in the longitudinal direction. Excitation of the piezoelectrics results in coupled system dynamics equations that can be translated into generation of waves. Theoretical analysis based on the distributed parameter model was conducted in this paper.

A scalar measure of the traveling to standing wave ratio was created using 2-dimensional Fourier Transform of the wave form. The results then were compared to common method in the literature for assessment of standing to traveling wave ratio.
Optimal Design of Intentional Mistuning for a Bladed Disk With Interval Uncertainty
Authors: Yoo David , Tang Jiong
Published: July 2018

This paper presents a methodology for the optimal design of intentional mistuning for a mistuned bladed disk with interval uncertainty. For a bladed disk where blades are weakly coupled, presence of random mistuning can easily induce vibration localization. This phenomenon will lead to great amplification in response amplitude of certain blades. To achieve desired reliability of a bladed disk, amplified response must be reduced to certain level, which requires probabilistic or reliability analysis. In this study, it is considered that blades have random distribution and coupling between blades has interval uncertainty. To treat the interval uncertainty appropriately, the worst-case combination of interval couplings is searched first, then probability of failure is evaluated under the worst-case condition. To increase reliability of a bladed disk, intentional mistuning is used in this study. While applying the intentional mistuning, it is also wanted to minimize the degree of intentional mistuning to minimize the cost of implementation. To find optimal combination of intentional mistuning parameters to achieve dual goals, gradient-based design optimization approach is utilized, which is expected to guarantee efficient convergence. To carry out gradient-based design optimization, sensitivities of objective function and probabilistic constraints with respect to intentional mistuning parameters are derived. During the sensitivity analysis, distribution of forced response amplitude is identified through Gaussian fit and eigenvalue perturbation theory is referred to. Monte Carlo simulation is utilized to accurately calculate probability of failure and its sensitivity. The proposed method is demonstrated with numerical examples of two distinct bladed disks.
Vibration Isolation of a Cantilever Beam Using Fluidic Flexible Matrix Composite Tubes
Authors: Miura Kentaro , Zhu Bin , Rahn Christopher D. , Smith Edward C. , Bakis Charles E.
Published: July 2018

Fluidic Flexible Matrix Composite (F2MC) tubes are a new class of high-authority and low-weight fluidic devices that can passively provide vibration damping, absorption, and isolation. In this paper, transverse cantilever beam vibration causes strain-induced fluid pumping in F2MC tubes bonded to the beam surface, generating flow through a fluidic circuit. The F2MC tubes and fluidic circuit are designed to significantly reduce moment and shear transmission at the root of the cantilever beam. An analytical model of a cantilever beam with F2MC tubes is used to perform a parametric study via Monte Carlo methods. An isolator is designed that simultaneously attenuates root shear and moment transmission by over 99% at the first bending mode. By modifying the fluidic circuit dimensions and F2MC tube attachment locations, over 99% root shear and moment transmission attenuation is achieved for the second beam bending mode. The tunability and pumping efficiency of the F2MC tube makes it a promising candidate for passive vibration control applications, including aerospace structures such as wings and rotorcraft landing gear.
Discrete Time Finite Element Transfer Matrix Method Development for Modeling and Decentralized Control
Authors: Cramer Nick , Swei Sean , Cheung Kenny , Teodorescu M.
Published: July 2018

The current emphasis on increasing aeronautical efficiency is leading the way to a new class of lighter more flexible airplane materials and structures, which unfortunately can result in aeroelastic instabilities.

To effectively control the wings deformation and shape, appropriate modeling is necessary. Wings are often modeled as cantilever beams using finite element analysis. The drawback of this approach is that large aeroelastic models cannot be used for embedded controllers. Therefore, to effectively control wings shape, a simple, stable and fast equivalent predictive model that can capture the physical problem and could be used for in-flight control is required.

The current paper proposes a Discrete Time Finite Element Transfer Matrix (DT-FETMM) model beam deformation and use it to design a regulator. The advantage of the proposed approach over existing methods is that the proposed controller could be designed to suppress a larger number of vibration modes within the fidelity of the selected time step. We will extend the discrete time transfer matrix method to finite element models and present the decentralized models and controllers for structural control.
3D Printing Complex Structures Using Modeling and Simulation
Authors: Mazhar Hammad
Published: July 2018

This paper describes an open source parallel simulation framework capable of simulating large-scale granular and multi-body dynamics problems. This framework, called Chrono::Parallel, builds upon the modeling capabilities of Chrono::Engine, another open source simulation package, and leverages parallel data structures to enable scalable simulation of large problems. Chrono::Parallel is somewhat unique in that it was designed from the ground up to leverage parallel data structures and algorithms so that it scales across a wide range of computer architectures and yet has a rich modeling capability for simulating many different types of problems. The modeling capabilities of Chrono::Parallel will be demonstrated in the context of additive manufacturing and 3D printing by modeling the Selective Layer Sintering layering process and simulating large complex interlocking structures which require compression and folding to fit into a 3D printer’s build volume.