bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comparative Study of Passive Vibration Isolator Modeling and Analysis
Authors: Kaul Sudhir
Published: March 2015

Passive vibration isolators are extensively used in wide ranging applications such as automotive, aerospace, railroad and earth moving equipment in the mechanical industry, and in structural applications in the civil industry. These isolators serve as spring-damper units that isolate specific parts of a system from external dynamic loading, or from other sub-systems that cause vibration excitation. Passive isolators exhibit very complex behavior that depends on excitation frequency, displacement amplitude, ambient temperature and pre-load in addition to geometry, design features as well as material composition of the isolator. Various models are prevalent in the existing literature for the design and analysis of such isolators, ranging from the basic Voigt model to more complex models such as the Maxwell-Voigt model with multiple Maxwell elements, the Maxwell ladder model, the three dimensional viscoelastic model, the fractional derivative model, and models specifically used for capturing the hysteresis behavior or the displacement limiting behavior. However, each of these models is successful in representing certain characteristics of the isolator while being unable to capture other key attributes. This paper provides a comparative study of some of the main models that are commonly used for the design and analysis of passive vibration isolators. Experimental data collected from a passive elastomeric isolator under varying excitation conditions is used to identify parameters associated with some of the commonly used models. The analysis results are compared and specific highlights and shortcomings of each model are identified and discussed.
Analysis of Kinematic and Dynamic Behaviour of Valve Train System
Authors: Rai Vishnu R. , Mahangade Vijay M. , Remesan C. B.
Published: March 2015

This paper discusses the work done on kinematic and dynamic analysis of Valve Train (VT) system of a diesel engine by Analytical method. Above said analysis was done as a part of verification of VT system design for an engine speed increase of 21 %. Kinematic analysis is carried out to study the change in valve motion characteristics such as cam contour radius, tappet contact eccentricity etc. Further to this, dynamic analysis is carried out to assess forces and stresses on valve train components. Effect of cam tappet contact stresses, buckling load on push rod, spring surge, ratio of spring force to inertia force, valve seating velocity at increased speed condition etc. are discussed in detail. The kinematic and dynamic analysis methodology adopted, was validated using GT-VTRAIN software for existing and increased speeds and the comparative results are also discussed.
Threshold Selector for Fault Detection on Closed-Loop Predictor-Based Recursive System Identification
Authors: Kim Young-Man
Published: March 2015

In this research, predictor-based system identification is recursively implemented to identify system in closed-loop, which has been connected with proper threshold setting for fault detection. The predictor-based system identification technique is based on the assumption that the process and measurement noise is white. This paper shows how recursive system identification is connected with fault detection, which can remove the influence of noise. The effectiveness is demonstrated for recursive system identification combined with proper threshold setting via Matlab simulation.
3D Dynamical Model for Liquid Motion Simulation in a Partially Filled Tank
Authors: Bouazara M. , Noui O. , Richard M. J.
Published: March 2015

Many 2D mechanical models have been developed to simulate liquid sloshing of a partially filled tank with different shapes. However, those models don’t represent properly the complex liquid motion, especially in the case of the portable tanks. Indeed, forces exerted on the fluid can be lateral, longitudinal and vertical. Then, liquid displacement and pressure forces applied to the tank walls are undervalued and can cause design flaws. In this case, 2D mechanical models are ineffective for the simulation of liquid motion properly. It this study a 3D equivalent mechanical model has been developed. This dynamical model is used to simulate different liquid motion in a partially filled tank that take into account any sort of excitement forces and get more accurate results in terms of displacements and pressure forces. Afterward, various tank forms and their compatibility with the 3D model are discussed, such as circular, modified oval and modified trapezoidal sections. Finally, equations of motion are developed for each tank shape.
Development of Autonomous Mobile Platform for Automated Process of Ship Hull Fabrication
Authors: Kim Jongjun , Kim Jeomgoo
Published: March 2015

Automated equipment is used for the ship fabrication process to obtain its higher productivity. However, in the final assembly stage of ship structures, automatic welding system has some constraints on application because of angled and curved surfaces. In order to overcome these constraints, wall climbing mechanism which has mobility and strong adhesion force is necessary. This paper presents an autonomous mobile platform designed for climbing on ferrous 3-D surfaces with welding head. The switchable permanent magnets are used for adhesion, which are capable of adjusting a maximum adhesion force if a variation in the magnetic field strength is required. The mechanism of mobile platform has identical twin bodies, link, flexible rail and sensing devices. Experimental results on the test block verified that the proposed mechanism was feasible and suitable for mobile platform of welding head.
Computer Simulation and Modelling of Passive Humidification Device Cavity for Intensive Care Patient Medical Applications
Authors: Shafik Mahmoud , Lechevretel Anne
Published: March 2015

This paper presents the research that has been undertaken into the passive humidification device cavity airflow structures and patterns. This was aiming to improve the device airflow, Heat and Moisture Exchange (HME) materials performance, for a greater patient care. However the objectives were to assist in understanding the optimal cavity structural geometries, generating improved airflow patterns over target HME material structures and consequently leading to improved heat and moisture exchange properties.

Airflow studies of the device have been undertaken using the Computational Fluid Dynamics (CFD) interface of the ANSYS. The CFD package enables analysis of fluid flow and heat transfer. This paper presents the results of the CFD simulations carried out on different passive humidification device cavity designs and materials arrangements. An optimised design leading to enhanced airflow structures and patterns, heat and moisture properties of the device is also presented in this paper.
Antenna Array Configuration in Holographic Microwave Imaging
Authors: Wang Lulu , Al-Jumaily Ahmed , Simpkin Ray
Published: March 2015

Biomedical imaging has played an important role in identifying and monitoring the effectiveness of the current state of the art treatments for many diseases. We recently proposed a novel holographic microwave imaging array (HMIA) technique for lesion detection. One of the most important considerations of this technique is the antenna array configuration. This paper demonstrates investigation of using various antenna array configurations to generate a high-resolution microwave image by using the HMIA technique. Both simulation and experimental results are obtained and compared using spiral, random and regularly spaced array configurations to fully demonstrate the effectiveness of antenna arrays to the HMIA technique. The results show that the proposed spiral and random array configurations have the ability to produce high-resolution images at significantly lower cost compared to regularly spaced array. The potential biomedical imaging applications of the research findings would be breast cancer detection and/or brain stroke detection.
Passive Suspension Optimization Using Teaching Learning Based Optimization and Genetic Algorithm Considering Variable Speed Over a Bump
Authors: Gadhvi Bhargav , Savsani Vimal
Published: March 2015

The main objectives of a vehicle suspension system are to isolate the road excitations to reach the sprung mass of the vehicle and proper road holding. This paper proposes a solution to optimize a quarter car linear passive suspension parameters while passing over a bump with variable speeds to improve the ride comfort and road holding. The Teaching-learning based optimization algorithm (TLBO) is used to solve the problem and results are compared to those obtained by Genetic algorithm (GA) technique. The quarter car model presented is simulated in time domain subjected to a Cosine speed bump considering the variable speeds of the vehicle over it. Results show sprung mass acceleration, and tire displacement are reduced by 26.03%, and 23.7% respectively by using TLBO and 22.3%, and 18.52% respectively by using GA, conforming the capabilities of the optimization techniques.
Parallel Processing Algorithm for a Direct Solution of Customized Fourier Transforms
Authors: Kim HyungTae , Jin KyungChan , Kim Jongseok
Published: March 2015

A parallel algorithm for a direct solution of customized Fourier transform was proposed using a general processing unit (GPU). The algorithm was derived from parallel addition and multiplication, and was applied to non-integer Fourier transform (NFT). The parallel NFT was targeted to improve the resolution in 3D RF profile measurement. The proposed algorithm was efficient in processing time through consideration of the amount of operation using recent parallel FFT (Radix-2).
Elastic Beam Vibration Control With Phase-Locked Loop
Authors: Lopes Guilherme Cano , Bueno Átila Madureira , Balthazar José Manoel
Published: March 2015

The Phase-Locked Loop (PLL) is a closed-loop control system that synchronizes a local oscillator to an oscillatory incoming signal. The PLL plays important roles in communication, computation and control systems, allowing the correct flow of information by efficiently generating and distributing clock reference signals. PLLs are also applied in motor speed control and in atomic force microscopy. Nevertheless, PLLs are inherently nonlinear devices, and behaviors such as bifurcations and chaos may arise. In this paper, the vibration control of an elastic beam is performed by a PLL control structure. Additionally, different designs for the PLL-beam control system are discussed.
Dynamics and Stability of Towed Flexible Cylinders: Theory and Experiments
Authors: Kheiri Mojtaba , Païdoussis Michael P. , Amabili Marco
Published: March 2015

In this paper, a newly developed nonlinear model is used to predict the dynamical behaviour and stability of a typical towed flexible cylinder. The numerical solutions are obtained via a time-integration method and also via the AUTO software. The effect of some system parameters on the local and overall stability and dynamics of the system is also investigated. Some experiments are then described which were designed to illustrate the dynamical behaviour of towed flexible cylinders and to test the theory. The experimental observations are generally in qualitative agreement with the nonlinear theory. Quantitative comparison of various quantities, e.g. the instability thresholds, between experiment and theory, based on the estimated values of some of the theoretical nondimensional parameters, is also fairly good.
Low Cost, Flow-Rate-Controllable Cryogenic Cooling System for Manufacturing Processes
Authors: Khawam Louai Al , Haidar Ali Abu , Mansour Mohammad , Dimassi Fadi El , Ammouri Ali , Hamade Ramsey F.
Published: March 2015

In-process cryogenic cooling in fabrication processes is known to — among other benefits — extend tool life and improve the surface properties of a work-piece. To provide flexible applications of cryogenic cooling, control of the cooling fluid is required. The commercial availability of such a control system is limited and, if available, is rather expensive. This paper reports on the design and build of a low-cost controlled cryogenic cooling system. The system supplies an adjustable flow of liquid nitrogen to the work-piece under process. Flow control is accomplished by controlling the temperature and/or pressure of an intermediate actuator while controlling the flow via an actuated electronic valve. Using a custom code using LabVIEW, the user would specify the cooling parameters and the system will automatically adjust the temperature/pressure signal input to the actuator as well as the valve opening while monitoring both temperature and pressure of the actuator. Flow development of liquid nitrogen inside the system was modeled using ANSYS. The closed loop system will guarantee minimum use of liquid nitrogen in an as-needed basis similar to minimum quantity lubrication.
Forces Applied During Manual Assessments of Low Back Pain Patients
Authors: Gudavalli M. R. , DeVocht J. W. , Xia T. , Vining R. D. , Wilder D. G. , Meeker W. C. , Goertz C.
Published: March 2015

Doctors of chiropractic (DCs) use manual palpation to subjectively assess the relative “stiffness” (resistance) of spinal articulations to help inform decisions regarding where to focus treatment. The objective of this study was to quantify the forces generated by DCs when assessing patients with low back pain (LBP). This is an observational study nested into a three-arm randomized clinical trial evaluating two forms of chiropractic treatment and one sham control. LBP patients of both genders between 21–65 years of age participated in the study. Measurements were collected with the participants lying prone on an examination table embedded with force plates. Three DCs applied manual force downward on the participants to obtain a sense of relative joint resistance over vertebral segments L1-L5, the superior sacrum, and bilateral sacroiliac (SI) joints. Peak forces generated during the manual assessments were extracted using custom-written, semi-automated, MathCad software. The results were descriptively analyzed using SPSS statistical software. Three clinicians manually assessed spinal resistance during 230 observations. Mean peak force ranged from 128–178N. Higher force levels were observed at lower vertebral levels and the pelvis by two of the clinicians. L3 and L4 spinal levels showed the greatest similarity of force applied by 3 DCs.
A Hybrid Model for Characterizing Pre-Yield Properties of MR Fluids
Authors: Eshaghi Mehdi , Sedaghati Ramin , Rakheja Subash
Published: March 2015

This study aims to present a field dependent phenomenological model to characterize the Magneto-Rheological (MR) fluid in the pre-yield region under varying frequency and applied magnetic field. Systematic analytical and experimental studies are proposed to formulate a hybrid model for representing complex shear modulus of a typical MR fluid (MR 122EG from Lord Corporation) as a function of both applied magnetic field and frequency. Two fully treated MR based sandwich beams with aluminum and copper face layers and MR fluid as the core layer are designed and fabricated. Uniform magnetic flux across the sandwich beam is provided using two permanent magnets. The fabricated MR based sandwich beams are then tested on an electrodynamic shaker under sweep sine excitation and different applied magnetic field to realize the effect of external excitation frequency and applied magnetic field on the stiffness and damping properties of the structure. The finite element model based on classical plate theory is also developed to analyze vibration response of the designed MR based sandwich beams incorporated with MR fluid. Then, by correlating the finite element results with those of the experiment, the frequency and field dependent complex shear modulus of the MR fluid is identified.
Numerical Simulations and Experimental Data to Evaluate Residual Limb-Socket Interaction
Authors: Morotti Roberto , Rizzi Caterina , Regazzoni Daniele , Colombo Giorgio
Published: March 2015

This paper presents an automatic simulation procedure to study the stump-socket interaction that has been embedded within a software platform specifically developed to design lower limb prosthesis. In particular, it investigates and compares the results obtained by means of FE tools with the experimental data acquired with pressure transducers. A transfemoral (amputation above knee) male amputee has been considered as case study. Numerical simulations have been carried out considering different techniques to acquire the residuum geometry and different socket models. In details, two residuum geometric models were reconstructed starting from MRI images and from 3D scanning to investigate how acquisition techniques influence the final results. Two socket geometric models were taken into account. The first was the patient’s real socket, acquired by 3D scanning; the second one has been modeled using a dedicated CAD system, named Socket Modeling Assistant. The patient’s real socket has been also used to perform the experimental pressure measurements. The experimental data have been acquired by means of the Tekscan F-socket system. Results reached so far allowed identifying main criticalities and future developments to improve the accuracy of the numerical results and make available a full-automated simulation procedure.
Design, Analysis, and Experimental Studies of a Novel PVDF-Based Piezoelectric Energy Harvester With Beating Mechanisms
Authors: Chen Kuo-Shen
Published: March 2015

Wireless sensor networks become increasingly important in modern life for structural health monitoring and other related applications. In these applications, due to their overall sensor populations and possible covered measurement areas, the replacement of batteries becomes a difficult and unrealistic task. As a result, energy harvesters to convert environment wasted vibration energy into electricity for powering those sensor nodes become important and many miniaturized device have been realized by using MEMS technology. In order to achieve optimal performance, the energy harvester must be operated at the resonance frequency. However, the vibration frequencies of environmental vibrations are usually much less than that of those miniaturizing energy harvesters and this fact could be a major barrier for energy harvesting performance. In this paper, a new piezoelectric energy scavenging concept is proposed and demonstrated to convert environmental vibrations into electricity. Unlike previous MEMS-based piezoelectric energy harvesters, which suffer from matching between environmental low frequency vibration and the much higher system natural frequency, this work proposes a novel beating design using polymer piezoelectric materials in collaborating with a beating mechanism. That is, by creating impact force via the low frequency vibration motion from the mechanism, it is possible to excite system natural frequency by the low frequency environmental vibrations and it is possible to operate the entire system at the natural frequency. This work contains details in presenting this idea, designing piezoelectric harvester systems with flexible PVDF elements, exploring their vibration characteristics, and energy accumulating strategies by using a capacitor with a full-bridged rectifiers or a boost conversion. By experimental characterization, the overall harvesting efficiency of the proposed design is much greater than that from the design without the beating mechanism. It indicates that the efficiency is significantly improved and the proposed translational design could potentially improve the future design approach for piezoelectric energy harvesters significantly. In summary, this preliminary study shows that it is a feasible scheme for the application of piezoelectric materials in harvesting electricity from environmental vibrations. Although this work is still in its initial phase, the results and conclusions of this work are still invaluable for guiding the development of high efficient piezoelectric harvesters in the future.
Analysis of Performances of a Semi-Active Suspension Implemented on a Landing Gear
Authors: Ocaña Marta I. , Novillo Eva , Morante Esteban , Chamorro Eduardo
Published: March 2015

Semi-active suspensions are able to adapt their behavior to the specific necessities of each operation phase of the vehicle. Their application in the aerospace industry is very attractive, specifically in landing gear actuators. However, according to Ref. [1], no examples of commercial use of this technology in this industry are reported in recent reviews of the state of the art.

In this paper, the real capabilities of a magneto-rheological semi-active suspension implemented on an UAV nose landing gear designed and manufactured by CESA are introduced by the analysis of the performances obtained by test when it is submitted to quasi-static and dynamic working conditions.
CFD Analysis of a Fluidized Bed Reactor for Industrial Application
Authors: Vaccari Anna , Pinelli Michele , Pirani Luca , Gandolfi Nicola
Published: March 2015

The fluidized bed reactors are widely used in chemical, mining and pharmaceutical industries and energy applications because of the low pressure drop, the uniform distribution of temperature and of high-speed mass transfer of energy and speed. Fluidization behavior depends on the reactor geometry and internals as well as the particle size distribution and physical properties of the process material. This paper presents a 3D fluid dynamic simulation of a fluidized bed reactor for the pharmaceutical processing of powder, such as mixing, granulation and drying. Firstly, sensitivity analyses based on a literature test-case were performed, for the validation of the computational model and the development of the additional components required for the simulation of a real fluidized bed reactor. Then an unsteady URANS 3D simulation of a modular laboratory-scale fluid bed reactor, product of IMA S.p.A. Active Division, was performed to evaluate the velocity field and particle distribution of the powder involved in the mixing process.
Modeling and Trajectory Control of a Forklift-Like Wheeled Robot
Authors: Lee Ho-Hoon
Published: March 2015

In this paper, kinematic and dynamic models are derived for a forklift-like four-wheeled mobile robot, and then, based on the models, a new trajectory control scheme is designed and evaluated for the robot. The dynamic model, exhibiting non-minimum-phase characteristics, is derived by applying Lagrange’s equations and then the control law is design by using Lyapunov stability theorem and the loop shaping method. The proposed control scheme consists of a trajectory generator, a motion control law, and a steering control law. First, a real-time trajectory generator is designed based on the nonholonomic kinematic constraints of the robot, in which the reference driving speed and time rate of heading angle are computed in real time for a given desired trajectory of the robot. The proposed trajectory generator guarantees a local asymptotic stability. Next, motion and steering control laws are designed based on the dynamic model of the robot. The motion and steering control laws are used to control the robot speed and steering angle. The proposed control guarantees asymptotic stability of the trajectory control while keeping all internal signals bounded. Finally, the validity of the proposed control scheme is shown by realistic computer simulations with one sampling-time delay in the control loop.
Feature Extraction Algorithm Fusion for SONAR Sensor Data Based Environment Mapping
Authors: Ismail Hesham , Balachandran Balakumar
Published: March 2015

Mobile platforms that make use of concurrent localization and mapping algorithms have industrial applications for autonomous inspection and maintenance, such as the inspection of flaws and defects in oil pipelines and storage tanks. An important component of these algorithms is feature extraction, which involves detection of significant features that represent the environment. For example, points and lines can be used to represent features such as corners, edges, and walls. Feature extraction algorithms make use of relative position and angle data from sensor measurements gathered as the mobile vehicle traverses the environment. In this paper, sound navigation and ranging (SONAR) sensor data obtained from a mobile vehicle platform are considered for feature extraction and related algorithms are developed and studied. In particular, different combinations of commonly used feature extraction algorithms are examined to enhance the representation of the environment. The authors fuse the Triangulation Based Fusion (TBF), Hough Transfrom (HT), and SONAR salient feature extraction algorithms with the clustering algorithm. It is shown that the novel algorithm fusion can be used to capture walls, corners as well as features such as gaps in walls. This capability can be used to obtain additional information about the environment. Details of the algorithm fusion are discussed and presented along with results obtained through experiments.
Actuator Array Manipulation Using Low Resolution Local Sensing
Authors: Parajuli Deepak , Bedillion Mark D. , Hoover Randy C.
Published: March 2015

An actuator array is a planar distributed manipulation system that uses multiple two degree-of-freedom actuators to manipulate objects with three degrees of freedom (x, y and θ). This paper presents an accurate method of estimating position and orientation of an object using local sensing and communication. In this method, each of the distributed modules contains a number of binary sensors, weight sensors, and two planar actuators. The binary sensors combined together give a binary image and analog sensors in each module combined together form a grayscale image representation of the weight distribution of the object under manipulation. Additive normalization has been used to combine binary and grayscale distributed sensing images together to come up with increased precision estimates of the position and orientation of an object. A distributed sensing simulation has been developed in Simulink and the effectiveness of this method has been verified for rectangular and circular objects using the Simulink model.
Modelling and Numerical Analysis for High Frequency Characteristics of Laminated Galfenol Based on Eddy-Current
Authors: Tan Yimin , Zhang Zuguang , Zu Jean
Published: March 2015

Galfenol, a novel magnetostrictive and ferromagnetic material, has been employed in various applications because of the material’s outstanding mechanical properties. For high frequency applications, the energy loss of eddy-current is a critical criterion because this loss not only reduces the power efficiency for Galfenol material, but also rapidly generates large amounts of heat that can destabilize the system. While laminating ferromagnetic material has been proved to be an effective way that minimises eddy-current, the objective of this research is to investigate the laminated Galfenol material’s plausibility in high frequency applications. For the prescribed geometry, an accurate model for the generated eddy-current is derived based on the Maxwell equations. Combining a built magnetic coupled dynamic model, the relationship between the strain response and the applied magnetic field is derived under high frequency conditions. The simulative results of the laminated Galfenol rods are compared to those rods without laminations. The comparison shows that the laminated Galfenol rod exhibits a milder hysteresis than the non-laminated Galfenol rod. Furthermore, the laminated Galfenol rod is able to maintain a high strain output with a broader frequency range compared to the non-laminated Galfenol rod. This work proves that laminating Galfenol rods are capable of restricting the generation of eddy-current and improving high frequency characteristics significantly.
Recent Trends in Stabilization and Control of Distributed Parameter Dynamic Systems
Authors: Radisavljevic-Gajic Verica , Karagiannis Dimitrios A. , Cheng Meng-Bi , Su Wu-Chung
Published: March 2015

The field of control and stabilization of distributed parameter systems described by partial differential equations has recently seen an increasing number of results published by very respected researchers in excellent control engineering and applied mathematics journals. This paper presents a survey of control and stabilization results with emphasis on controls. Various distributed parameter dynamic control and stabilization problems have been studied corresponding to heat conduction, wave propagation, Schrodinger equation, crowd (swarm) dynamics, magneto-hydro-dynamic channel flow, string and beam equations, viscous Burger equation, and general diffusion equations. Various techniques have been used for control and stabilization of such systems: Lyapunov stabilization, backstepping, gain scheduling, singular perturbations, sliding mode control, observer driven controller, tracking control, sampled-data control, neural networks. The field still remains widely open for future research. Applications of surveyed results to various areas including robots, aircraft, networks, transmission lines, electrochemical processes in energy systems are indicated.
Nonlinear Dynamics of High-Dimensional Models of a Rotating Euler-Bernoulli Beam Under the Gravity Load
Authors: Huang J. L. , Zhu W. D.
Published: March 2015

Nonlinear dynamic responses of an Euler-Bernoulli beam attached to a rotating rigid hub with a constant angular velocity under the gravity load are investigated. The slope angle of the centroid line of the beam is used to describe its motion, and the nonlinear integro-partial differential equation that governs the motion of the rotating hub-beam system is derived using Hamilton’s principle. Spatially discretized governing equations are derived using Lagrange’s equations based on discretized expressions of kinetic and potential energies of the system, yielding a set of second-order nonlinear ordinary differential equations with combined parametric and forced harmonic excitations due to the gravity load. The incremental harmonic balance (IHB) method is used to solve for periodic responses of high-dimensional models of the system and period-doubling bifurcation. The multivariable Floquet theory along with the precise Hsu’s method is used to investigate the stability of the periodic responses. Phase portraits and bifurcation points obtained from the IHB method agree very well with those from numerical integration.
Research on Constitutive Model of Hybrid Photovoltaic/Piezoelectric Actuation Mechanism
Authors: Jiang Jing , Deng Zong-Quan , Yue Hong-Hao , Wang Lei , Tzou Horn-Sen
Published: March 2015

Opto-mechanical actuators do not require hard-wired connections to control light source. Accordingly, the control commands will not be influenced by undesirable electric noises. Without accessorial devices and connecting wires, photonic control which conforms to the lightweight trend of space structure has great research value. PLZT photostrictive actuator can only induce actuation strain along its polarized direction, so it has the deficiency of one-way actuation. In this paper, the novel hybrid photovoltaic/piezoelectric actuation mechanism is proposed to remedy this deficiency. The ultraviolet light-driven PLZT induced voltages are used to drive piezoelectric actuator. Based on the equivalent electrical model, constitutive model is established to define the time history of actuation strain of piezoelectric actuator driven by photovoltage. Experimental platform is established to verify this established constitutive model. A logical switch is designed to realize positive and negative connection switch between PLZT photovoltaic generator and piezoelectric actuator. It is experimentally validated that the piezoelectric actuator can induce both positive and negative control forces.
Output Feedback Model Predictive Control of Linear Parameter Varying Systems
Authors: Gao Jianwei , Yang Weilin , Zhang TieJun
Published: March 2015

In practical control systems, the plant states are not always measurable, so state estimation becomes essential before the state feedback control is applied. In this paper, we consider output feedback model predictive control (MPC) for linear parameter varying (LPV) systems with input constraints. We proposed two approaches to obtain the observer gain, that is to compute the gain in the dynamic optimization at each time instant (on-line), and to compute the gain in advance (off-line), respectively. By applying both approaches, the state estimation error goes to zero asymptotically, meanwhile, the state feedback gain is optimized. In fact, the on-line approach can help enlarge the feasibility region and improve the control performance. It has been shown that feasibility of both approaches can be maintained for the closed-loop control systems even in the presence of state estimation error. Finally, the proposed output-feedback MPC strategies are applied to an angular positioning control system and the control of a transcritical CO2 vapor compression refrigeration system.
Mathematical Analysis of the Motion of Fluid in Between Ceramic-on-Ceramic Total Joint Arthroplasty Bearing Surfaces
Authors: Paliwal Manish , Wickramasinghe Thulsi
Published: March 2015

Friction-induced squeaking has been reported in 1–20% of patients who have a ceramic on ceramic total hip replacement, which is a subject of annoyance. Friction induced stick-slip phenomenon is the driving force behind squeaking. Stick-slip occurs when the film lubrication is broken. Fluid film lubrication is a function of sliding speed, lubricating fluid viscosity, bearing roughness, clearance, and contact pressure. A breakdown of fluid film lubrication may result from edge loading, presence of third bodies (wear particles) during articulation, damage to the articular surface (increased roughness), mismatched bearing diameters, etc. In the present study, influence of variation in relative densities of the biofluid and femoral head is mathematically investigated when the spheres are initially subjected to an impulse (start-up condition: initial contact to pre-swing phase of the gait cycle). The parametric analysis also looks at the influence of initial impulse speed, and time of approach of the femoral head to the outer shell.
Research on Active Control for Thermal Deformation of Precise Membrane Reflector With Boundary SMA Actuators
Authors: Lu Yi-Fan , Yue Hong-Hao , Deng Zong-Quan , Tzou Horn-Sen
Published: March 2015

Along with the rapid development of space exploration, communication and earth observation technology, the large space membrane structure gains its widely application. With poor stiffness and large flexibility, the surface accuracy of membrane structures can be easily interfered by the space environment variety, so precise shape control of in-orbit space membrane reflector becomes the focus in space technology area. As an object for this paper, the active control of the membrane reflector deformation under typical thermal disturbance in space is investigated. Considering of Von-Karman geometrical nonlinearity, the equilibrium equations of a circular membrane are firstly presented based on Hamilton’s Principle and Love’s thin shell theory. As a simplification for equilibrium equations, the nonlinear mathematical model for the circular membrane in a symmetrical temperature field is obtained. In the next place, an FE model for a circular membrane under thermal load is developed in Abaqus as an example. By contrasting the FEM deformation analysis with mathematical modeling solutions of circular membrane reflectors under typical thermal load, it is demonstrated that the theoretical model is capable of predicting the amplitude of membrane surface deformation. At last, a boundary actuation strategy for membrane shape control is proposed, which could effectively decrease the membrane wrinkle induced by thermal disturbance via precisely control to the tension of the SMA wire actuators. The simulation result indicates the effectiveness of boundary active control strategy on improving membrane surface accuracy with different temperature distributions. The conclusions of modeling and analysis in this paper will be an essential theoretical foundation for future research on active flatness control for in-orbit large space membrane structure.
The Steady-State Thermal Effect on Rotordynamics of a Rod-Fastened Rotor-Bearing System
Authors: Zhuo M. , Yang L. H. , Yu L.
Published: March 2015

Gas turbine rotor works at high temperature, especially the turbine used to expand hot gas and generate power. For the F class heavy duty gas turbine, the inlet temperature of hot expanding gas of the first turbine stage can be as high as 1400°C. Temperature is not only the source of thermal stress of gas turbine rotors but also leads to the variation of elastic modulus. Both of these two factors can cause a local stiffness variation of the rotor and thus have an influence on the dynamic characteristics of the rotor. The rotor investigated in this paper is a circumferential distributed rod-fastened rotor which is made of several discs bolted together. A 3-D model of the combined rotor system considering contact effect is established. The steady-state temperature field of the combined rotor is obtained through a thermal analysis. The stress distribution due to restraint on free expansions of components of the rotor as well as the deformation under steady-state thermal load is derived from a static structural analysis. Then a pre-stress modal analysis is performed to calculate the lateral natural frequencies of the rotor-bearing system. Finally, based on modal results, unbalance response of the rotor-bearing system is calculated through a harmonic analysis. For all steady-state thermal related analysis, two kinds of elastic modulus are calculated, i.e., constant and temperature-dependent elastic modulus, corresponding to the effect of thermal stress and material degradation, respectively. Both two steady-state cases are compared with the room temperature results to evaluate the role of these two thermal factors.
Transient Two-Phase Effects in an Aeroengine Bearing Chamber Scavenge Test Rig
Authors: Chandra Budi , Simmons Kathy
Published: March 2015

Aeroengine bearing chambers typically contain bearings, seals, shafts and static parts. Oil is introduced for lubrication and cooling and this creates a two phase flow environment that may contain droplets, mist, film, ligaments, froth or foam and liquid pools. Efficient and effective liquid removal from a bearing chamber is a functional requirement and in recent years the University of Nottingham Technology Centre in Gas Turbine Transmission Systems has been conducting an experimental and computational research program one strand of which is investigating bearing chamber off-take flows. Initial investigations focussed on a chamber where there was a relatively deep pocket for oil collection below the chamber [1, 2]. In more recent studies Chandra et al have investigated a shallower geometry [3]. In both sets of studies, chamber residence volume and wall film thickness data have been obtained for a range of shaft speeds, scavenge ratios and liquid supply rates. Two methods of introducing liquid to the chamber have been used: a film generator that puts liquid directly onto the chamber wall and a droplet inlet system that distributes droplets from the rotating shaft.

During some of the previous investigations, visual data relating to the two phase flow in the outlet pipe immediately below the chamber was gathered together with data from pressure transducers one located in this pipe and one on the chamber itself. It has been observed that for some parameter combinations the chamber flow is gravity dominated whereas for others (typically at higher shaft speeds) the flow is shear dominated. During transition between regimes a pressure spike on the pipe pressure transducer is observed and this may be linked to a change in two phase flow regime within the outlet pipe. A study by Baker et al [4] on transient effects in gas-liquid separation has shown pressure spikes during transitions to new equilibrium conditions for two-phase pipe flow where the gas flow rate is suddenly increased.

In this paper outlet visualisation, chamber visualisation and pressure data are combined and conclusions are drawn relating to the parameters controlling whether shear or gravity dominate. The effect of the chamber flow regime on the outlet flow regime is assessed and presented. An implication of the analysis is that during transitional conditions a bearing chamber may contain a different quantity of liquid than in steady state conditions.
Low-Velocity Global-Local Impact Response of Smart Composite and Sandwich Composite Plates With Piezoelectric Transducers
Authors: Plagianakos Theofanis S. , Papadopoulos Evangelos G.
Published: March 2015

Higher-order layerwise piezoelectric laminate mechanics are presented for predicting the low-velocity impact response of pristine composite and sandwich composite plates with piezoelectric transducers. The present formulation enables prediction of the global (temporal variation of impact force, deflection, strain and sensory potential) and local through-thickness (distribution of displacement, stress and strain) impact response of plates with piezoelectric layers or patches. Its enhanced capabilities include efficiency in terms of computational cost, since the system matrices are reduced by means of a Guyan scheme or by using the eigenvectors, thus leading to a plate-impactor system containing a single or two deflection amplitudes per vibration mode, depending on consideration of transverse compressibility. The transfer of the plate-impactor system to state-space enables investigation of the feasibility of real-time active control towards impact force reduction by using output feedback control laws.
A Study on Calculation Method of Natural Frequency for Rubber Damped Torsional Vibration Absorbers
Authors: Shangguan Wen-Bin , Wei Yumin , Rakheja Subhash , Zhao Xu , Rong Jun-wei , Wang Ya-jie
Published: March 2015

The natural frequency is the key performance parameters of a rubber materials damper, and it is determined by the static and dynamic shear properties of the rubber materials (rubber ring) and the moment of inertia of the inertia ring. The rubber ring is usually in compression state, and its static and dynamic shear properties are dependent on its sizes, compression ratio and chemical ingredients. A special fixture is designed and used for measuring static and dynamic shear performance of a rubber ring under different compression ratios in the study. To characterize the shear static and dynamic performances of rubbers, three constructive models (Kelvin-Voigt, the Maxwell and the fractional derivative constitutive model) are presented and the method for obtaining the model parameters in the fractional derivative constructive models are developed using the measured dynamic performance of a rubber shear specimen. The natural frequency of a rubber materials damper is calculated using the fractional derivative to characterize the rubber ring of the damper, and the calculated frequencies are compared with the measurements.
Aging in Soft Tissues: Influence of Chemical Reactions on Mechanical Response
Authors: Pullela Mythravaruni , Ravindran Parag
Published: March 2015

Aging of soft tissues occurs through various mechanisms, which involve biochemical reactions, like glycation, oxidation and calcification of proteins in the extracellular matrix of the soft tissue. Aging leads to changes in the microstructure of the soft tissues which results in changes in its mechanical behavior. In this paper, a mixture theory based model that is thermodynamically consistent and applicable for chemically reacting systems is developed. The tissue (elastin) is modeled as a viscoelastic material. The model is simulated for uni-axial loading to study the effect of chemical reactions occurring in the tissue (elastin) on its mechanical response.
Experiment on Active Vibration Isolation of a Conical Shell Isolator
Authors: Li H. Y. , Li H. , Hu S. D. , Chen Z. B.
Published: March 2015

Conical shells have advantages such as light weight, higher stiffness and strength, its stiffness ratio between axial and transverse directions can be easily adjusted by changing its apex angle. Thus conical shell can be utilized as an isolator to protect precision payloads and equipment from severe dynamic loads. In this study, vibration isolation performance of a conical shell isolator laminated with piezoelectric actuators is investigated. The conical shell isolator is manufactured from epoxy resin. The payload is at the minor of the isolator. The major end of the isolator is fixed at a flange installed on a shaker. Macro fiber composite (MFC) is used as actuator, which is laminated on the outer surface of the conical isolator. The sensing signals from sensors on the isolator is transferred to a dSPACE system and the control voltage is transferred to a power amplifier and then to the MFC actuator. The control voltage is calculated in the Matlab/Simulink environment. Both negative velocity feedback and optimal controllers are employed in the active vibration control. The payloads are simplified to be a rigid cylinder, and two payloads with different weight are investigated in the study. Experimental results show that the proposed conical shell isolator is effective for vibration isolation of payloads, and vibration amplitude of the payload can be significantly reduced.
Research on Self-Loosening Mechanism of Bolted Joints Under Transversal Vibration
Authors: Wang Wei , Wang Qingli , Zheng Shuai , Liu Xiaowei , Liu Haiping
Published: March 2015

Bolted joints are widely used in the auto industry, energy field and Construction, and so on. Due to the wide use of the bolted joints, the degradation of bolts has significant effect on the performance of a whole machine. Under transversal vibration, the self-loosening of bolted joints, which is the biggest form of failure ranked only second to fatigue failure [1], will happen, due to the cyclic shear load. This paper is to study the mechanism of bolted joints’ self-loosening.

Aiming at analyzing the self-loosening mechanism of bolted joints under vibration, a three dimensional FEA model of bolted joints, which had taken thread into consideration, was built with the application of APDL, and the preload was applied on the bolted joints by dropping temperature, then FEA transient analysis of the bolted joints under transverse cyclic excitation was conducted. Effect of transverse cyclic excitation’s amplitude, initial preload, thread and bearing friction coefficients, the joints’ surface friction coefficient, the thread pitch and the hole clearance on self-loosening was investigated. The results show that the complete thread slip occurs prior to the complete bearing surface slip under transverse vibration; the smaller amplitude, the smaller thread pitch and the smaller hole clearance is, and the greater initial preload, thread and bearing friction coefficients are, the more difficult self-loosening is to happen; the joints’ surface friction coefficient has little relationship with self-loosening, however, the larger joints’ surface friction coefficient makes the needed shearing force, which induces the transversal vibration, larger. These are of great significance for understanding of fasteners’ self-loosening and designing of bolted joints’ anti-loosening.