bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimum Design of Compound Cylinders Used for Storing Pressurized Fluids
Authors: Patil Sunil A.
Published: April 2008

In the classical design of thick cylinders, if the internal fluid pressure approaches the safe working stress limit of the material, the thickness of the cylinder approaches infinite value. To overcome this difficulty, compound cylinders are used, where another cylinder is shrinkfitted on the inner cylinder. Designing a shrink fit assembly is tricky because the stress developed in the cylinders is a function of internal fluid pressure, shrinkage pressure and the dimensions of the cylinders. Also the shrinkage pressure is a function of the amount of interference and dimensions of the cylinders. That is, unless the shrinkage pressure is known, stresses developed cannot be computed and to compute shrinkage pressure, dimensions of both the cylinders must be known. Hence a cumbersome trial and error method is to be used. In the optimum design of compound cylinders, the thickness of both the cylinders should be just sufficient to withstand the hoop stresses developed. That means the maximum hoop stress produced in both cylinders should be equal. In this, shrinkage (contact) pressure plays an important role. The shrinkage pressure can be such that the limiting compressive stress is produced in inner cylinder. But when subjected to internal pressure, causes unequal stresses in both cylinders. That is, in one of the cylinders, the stress level can be maximum allowable and in other, less than maximum allowable. This paper describes the method of determining the optimum dimensions of both the cylinders made of specified material and to withstand a specified internal pressure so that the volume (and weight) is minimum. The results obtained are verified by using COSMOS and ANSYS finite element analysis packages.
Heat Exchanger Analysis Combining 1-D and 3-D Flow Modeling
Authors: De Henau Vincent , Ahmed Iftekhar
Published: April 2008

A recently developed method that couples a 1-D duct flow solver to a 3-D general purpose Computational Fluid Dynamics (CFD) solver is described. This methodology provides an integrated approach for the solution of coupled flow and heat transfer problem, utilizing 1D and 3D meshes for fluid flow. During the solution process, principles of conservation are preserved at the interface of the two flow domains. Results from the coupled 1D/3D simulation are then verified by comparison to the 3D solution, and are validated against an empirically obtained correlation for a shell and tube heat exchanger.
The Effect of Welding Self-Equilibrating Stresses on the Natural Frequencies of Thin Rectangular Plate With Edges Rotational Flexibility
Authors: Yousif Albert E. , Al-Samarrai Shakir , Al-Ammri A. Salam
Published: April 2008

An investigation has been made into the effect of residual stresses on the vibration characteristics of a thin rectangular plate elastically restrained against rotation along all edges using an energy method. General frequency equations with and without the effect of residual stresses have been obtained. Exact frequency equations with and without the effect of residual stresses for the cases: C-C-C-C, S-S-S-S, S-S-C-S, C-S-C-S, S-S-C-C, C-C-C-S have also been obtained. Exact equations were derived including the effect of the position of welding along the width of the plate for all cases considered. The validity of the equations obtained was checked with available special solutions with a good agreement.
High-Reynolds-Number Turbulent-Boundary-Layer Surface Pressure Fluctuations With Bubble or Polymer Additives
Authors: Winkel E. S. , Elbing B. R. , Dowling D. R. , Ceccio S. L. , Perlin M.
Published: April 2008

This paper reports multi-point dynamic pressure fluctuation measurements made beneath a high-Reynolds-number turbulent boundary layer (TBL) with wall-injection of air or polymer additives for the purpose of skin-friction drag reduction. Two independent experiments were conducted in the U.S. Navy’s Large Cavitation Channel (LCC) on a 12.9 m long, 3.05 m wide hydro-dynamically smooth (k+ < 1) flat plate at free-stream speeds from 6.5 to 20.0 m/s. The first, a bubble drag reduction experiment (BDR), involved injecting gas at flow rates ranging from 100 to 800 CFM (17.8 to 142.5 liter/s per meter of injector span) from one of two injectors located 1.32 and 9.78 m from the model leading edge. The second, a polymer drag reduction experiment (PDR), involved injecting polymer from a single slot injector, 1.32 m from the leading edge, at flow-rates ranging from 6 to 30 GPM (0.14 to 0.71 liter/s per meter of injector span). Dynamic pressure measurements were made with 16 flush-mounted transducers in “L”-shaped arrays located 10.7 and 9.8 m (70 × 106 < ReX < 210 × 106) from the leading edge for the BDR and PDR experiments, respectively. Measurements show modifications in the spectra, stream-wise coherence, and convection velocity of the pressure fluctuations due to the presence of gas or polymer in the near-wall region of the TBL. At the dynamic pressure measurement locations the maximum skin-friction drag reduction approached 100% for the BDR experiment and 63% for the PDR experiment.
Microbubble Contrast Agents in Vibro-Acoustography
Authors: Manilal P. I. , Al-Jumaily A. M. , Fatemi M.
Published: April 2008

This article discusses the possibility of using microbubble contrast agents in the Vibro-Acoustography (VA) technique. An existing mathematical model is used to determine the interaction of encapsulated microbubbles with VA ultrasound fields. Such models may lead to a better understanding of the underlying mechanics and interactions in clinical settings.
Acoustically Induced Mass Flow in Partially Saturated Porous Media: Applications to Fuel Cells
Authors: Staroselsky Alexander , Fedchenia Igor I. , Li Wenlong
Published: April 2008

In this work we aim to develop a theoretical framework for evaluating the feasibility of attaining significant improvement of fuel cells performance and stability by enhancing the transport processes in porous partially-fluid-filled cathode compartments through applying acoustic and structural excitations. A generic unified model has been derived of the structural/acoustic wave propagation in the porous media with consideration of its coupling with mass transfer. It has been demonstrated that the phase saturation has a strong impact on the wave dynamics in porous media. Explicit expressions have been obtained for the generalized multiphase Biot-type coefficients. A generalized filtration equation has been derived that takes into account the effects on mass transfer of dynamic loading, varying saturation, and solid structure distortion in this complex system. For model calibration a series of tests has been conducted to measure water flows through porous media with and without acoustic excitations. It has been demonstrated that the excitations may result in a net change of the saturation inside the porous medium and the applied structural/acoustic loading can intensify the transportation process. Based on the numerical and experimental results, certain recommendations have been made in regards to the selection of materials and the optimization of performance regime.
A Regression-Based Energy Method for Estimating Vehicle Interior Noise in Road Tests
Authors: Sung Shung H. , Nefske Donald J.
Published: April 2008

A regression-based energy method is developed for rapid estimation of the overall passenger-compartment interior noise (dBA) and Articulation Index (AI) in a vehicle of prescribed architecture when the vehicle travels on a particular road at a particular speed. The method is developed for use in the early vehicle design stage when only limited vehicle architecture design information are known. Regression analyses from a database of vehicle on-road tests and vehicle wind-tunnel tests are used to identify the energy transfer functions that represent the prescribed vehicle architecture. Energy excitation from both tire-road interaction and aerodynamic loads is then used to predict the interior dBA and AI responses. Comparisons of the predicted versus measured dBA and AI responses show reasonable agreement for car and wagon-type vehicles, although limited architecture data somewhat underestimates the actual response in certain vehicles
FFT Analysis Using LabView as a Part of Vibration and Preventive Maintenance Class for Senior Level MET students
Authors: Mitra Aniruddha , Sen Sahana
Published: April 2008

An existing senior level elective course on vibration in Mechanical Engineering Technology program at Georgia Southern University has been modified significantly. Two major components have been added to this course. Those are theoretical topics on preventive maintenance and laboratory experiments. As a part of laboratory experiments, Fast Fourier Transform (FFT) was introduced as a possible tool for vibration analysis for the purposes of machine diagnosis. Utilizing the current laboratory set up for the data acquisition systems, LabView software has been used for FFT analysis of signals from various sources. Four different modules were developed and implemented. The modules are as follows: random variation in acceleration of a toy cart due to roughness of the track and pulley, regular uniform wave signal which is generated by the lateral vibration of a cantilever beam at its natural frequency, signal generated by the imported raw data from other sources (e.g. MATLAB) and vibration signal of a shaft mounted on ball bearings in order to detect the defects in the bearing. Each of these modules is illustrated in this paper with suitable examples and suggested student activities and involvements. The results from FFT analysis have been cross checked using other methods and observations. As a follow up, students have been taken to a local industry where significant amount of emphasis is given to preventive maintenance of machineries by vibration data analysis using FFT. Future possible projects include the analysis of vibration data gathered from actual machine shop. This project opens the scope for greater collaborative effort between local industries and classroom activities.
Hydrodynamics of Moulding of Ceramic Articles From Beryllium Oxide Using Ultrasonic Activation
Authors: Zhapbasbayev U. K. , Kaltayev A. , Bitsoev G. D. , Turnayev S. K.
Published: April 2008

Moulding of thermoplastic slurry using ultrasound activation is studied experimentally. Thermoplastic slurry represents a high-viscous suspense of beryllium oxide powder and molten paraffin (with surfactant species) as a binder. Experimental results of slurry products reveal its low castability at minimal binder content. Thus, the actual problem is to increase slurry castability by ultrasound at minimal binder content. The role of bubble cavitations in slurry degassing process is discussed and parameters of ultrasound radiator necessary for cavitation onset in water are found. Consolidation of slurry in wire die is simulated, slurry velocity and temperature profiles are found and analyzed.
A Study on Detection of Small Fault in Cast Thin Plate Using Hitting Sound
Authors: Ohue Yuji , Shinomiya Masayasu , Neki Yasutoshi
Published: April 2008

The cast wood has the thin face with shallow grooves. The strength of the face was deteriorated, since the faults in the face cause the stress concentration. In order to investigate the possibility of the fault detection for the cast thin plate, seven kinds of thin plates with holes having a diameter of 0.3 to 1.0 mm and a depth of 0.7 mm were prepared and the hitting inspection were carried out using a swing robot. The signals were analyzed using FFT analysis and wavelet transform. The wavelet transform was better than the FFT analysis for the detection of the fault. It was possible to detect the existence of the fault in the plate using the hitting sound using the wavelet transform. It was clear that the fault detection in the thin plate depends on the relation between the vibration mode of the thin plate and the position of the fault in the plate.
Two-Photon Polymerization Technique for Bio-Applications
Authors: Ovsianikov Aleksandr V. , Chichkov Boris N.
Published: April 2008

We will report on the recently developed two-photon polymerization (2PP) technique for biological applications. 2PP of photosensitive inorganic-organic hybrid polymers (ORMOCERs) is applied for the fabrication of 3D scaffolds, micro-and nanostructures. ORMOCERs have negative resist behaviour and can be used as storage-stable, liquid photopolymerizable resins. When Ti:sapphire femtosecond laser pulses are tightly focused into the volume of this resin (which is transparent in the infrared) they initiate 2PP process transferring liquid into the solid state. This allows the fabrication of any computer-generated 3D structure by direct laser “recording” into the volume of this material. ORMOCERs demonstrate excellent cell adherence and cell growth rate comparable to that of Extracellular matrix. With 2PP technique there are no limits in complexity of the 3D scaffold structures which can be fabricated with the resolution of 100 nm.
Service Life Aging and Heat Exposure Effects on Aluminum Sheet Alloy Properties and Structural Crashworthiness Under Dynamic Axial Loading
Authors: Baccouche Ridha , Wagner David , Sherman Andy , Miller Craig , Ward Susan , Mahmood Hikmat
Published: April 2008

An investigation of the service life aging and heat exposure effects on sheet aluminum alloy properties and structural crashworthiness has been conducted. This research, part of a broader program, consists of investigating five aluminum sheet alloys each of which is subjected to four heat treatments. The aluminum sheet alloys investigated are 6111T4PD, 5754-O, 5182-O, 6022T4E29, and 6022T4. The four heat treatments are 177°C for 30 minutes, 200°C for 15 minutes, 200°C for 2 hours, and 200°C for 24 hours. The 200°C/24 hours treatment simulates the most severe thermal exposure i.e. components adjacent to exhaust pipes and manifolds. All 200°C heat treatments are in addition to the 177°C for 30 minutes. All specimens were subjected to the reference 177°C for 30 minutes treatment. Aluminum rails of hexagonal cross-section were formed for the twenty combinations of aluminum sheet alloys and heat exposures. These twenty formed aluminum rails were then bonded and riveted using Betamate 4601 adhesive and Henrob K50742 self-piercing rivets. Once assembled, these twenty rails were subjected to dynamic axial crushing at a speed of 40 kph (25 mph). Force-Time data was collected and responses were plotted for all tests. Force-Displacement responses were then integrated for the crush energy management and mean axial crush load for each of the aluminum sheet rails. Bar charts were generated to describe the crash loads and energy management behaviors of the various aluminum alloys and associated heat treatments. Service life simulated heat exposure was found to affect the mean crash load and crash energy management of the aluminum structural crash members. The heat exposure effects on the crashworthiness of the sheet aluminum members ranged from a reduction of [−21.6%] to an increase of [+6.8%] in the mean crash load and crash energy management with higher variation observed in the “T4” tempered aluminum alloys.
An Interactive Web-Based Approach to Perform Full-Scale Tensile Testing Experiments
Authors: Kholamkar Sachin , Chandrashekar Naveen , Anderson Edward E. , Hashemi Javad
Published: April 2008

An interactive web-based software on ‘Tensile Testing of Materials’ is developed to help undergraduate students learn more effectively about the objectives, procedure, and methods used in the experiment. The main objective was to better prepare the students in performing their tasks during the physical experiment. The intention of this project is to reap the benefits of both web based training as well as performing the experiments in a practical and interactive sense. Access to the software is given to the students before performing the actual experiment. The software is evaluated to assess its effectiveness. Our initial results verify that the virtual lab could be an effective tool in preparation of the students for the actual experimental tasks in a laboratory environment. In the following paper, the design of the software, important elements of the virtual lab and the evaluation results will be presented.
Trimming of Advanced High Strength Steels
Authors: Golovashchenko Sergey F. , Ilinich Andrey M.
Published: April 2008

Modern product design and manufacturing often utilizes a wide variety of materials. Where once low carbon steel predominated, a variety of different materials such as aluminum alloys and advanced high-strength steels (AHSS) are now being utilized. Although such alternative materials may provide a variety of benefits in manufacturing and design, these same materials may present difficulties when subjected to manufacturing processes originally designed for low carbon steel. One such manufacturing area where difficulties may arise is in trimming operations. A defect that may arise directly in the trimming operation are burrs. Burrs decrease the quality and accuracy of stamped parts and cause splits in stretch flanging and hemming. Current standards limit the production of burrs through accurate alignment of the upper and lower edges of the trim knives. The clearance between the shearing edges should be less than 10% of the material thickness. For automotive exterior sheet, this requires a gap less than 0.06mm. Unfortunately, tolerances often exceed the capabilities of many trim dies resulting in the production of burrs. To satisfy the current standards of quality and to meet customer satisfaction, stamped parts frequently need an additional deburring operation, which is often accomplished as a metal-finish operation and conducted manually. The objective of the research described in this paper was to study the mechanisms of burr generation and the impact on AHSS formability in stretch flanging. Results on both the conventional trimming process and a recently developed robust trimming process, which has the potential to expand tolerances of trim die alignment, will be discussed.
Heat Transfer Characteristics of Mixed Electroosmotic and Pressure Driven Flows Under Constant Heat Flux
Authors: Horiuchi Keisuke , Dutta Prashanta
Published: April 2008

Analytical solution for the heat transfer characteristics of steady electroosmotic flows with an arbitrary pressure gradient are obtained for two-dimensional straight micro-channels. Both thermally developing and fully developed regions are considered for hydraulically fully developed mixed flows under isoflux channel wall conditions. In mixed flow cases, the governing equation for energy is not separable in general. Therefore, we introduced a new method that considers the extended Graetz problem. Heat transfer characteristics are presented for low Reynolds number micro-flows where the viscous and electric field terms are very dominant. Our analytical techniques are verifled by obtaining an excellent agreement with existing literature for slug, pressure driven, and pure electroosmotic flow cases. In the fully developed region, the Nusselt number of mixed flow is independent of the thermal Peclet number for a particular Joule heat and imposed surface heat flux. The entry length of mixed flow significantly depends on the applied pressure gradient to the electroosmotic flow.
Investigation and Implications of a Compactor Fatality
Authors: Harris James R. , Struttmann Timothy , Merinar Timothy R.
Published: April 2008

A construction worker died August 18, 2003, when the compactor she was operating rolled over. A seatbelt and rollover protective structure (ROPS) were used by the operator. NIOSH investigators visited the scene of the incident and interviewed the employer, witnesses, and compactor manufacturer as part of NIOSH’s Fatality Assessment and Control Evaluation program to gather additional incident detail and to collect relevant equipment dimensions. Analysis of the equipment dimensions and victim anthropometry indicate that it is unlikely that the victim’s head struck the ground during rollover if the victim remained seated. Information on ROPS penetration into the ground during overturn was not available and was not considered in this analysis. This incident highlights the need to have a formal established safety and training program where operators must be familiar with the owner’s manual for equipment they operate and demonstrate competence in operating the equipment. Additionally, protective equipment, such as a seatbelt, must be securely fastened to be effective.
Modeling of Ferromagnetic Shape Memory Alloy Based Transducers for Electro-Hydraulic Actuators
Authors: Tan Honghao , Elahinia Mohammad H.
Published: April 2008

Ferromagnetic Shape Memory Alloys (FSMAs) like Ni-Mn-Ga have attracted significant attention over the past few years. What makes these materials attractive as actuators is their high energy density, large stroke, and high bandwidth. Among other applications, these properties make FSMAs potentially candidates for developing lightweight Electro-Hydraulic Actuators (EHA). The role of the FSMA transducer is to provide the mechanical energy by the linear displacement in the EHA. In order to develop effective FSMA-based transducers, it is important to study their dynamic behavior. In this paper a dynamic model is presented for a Ni-Mn-Ga transducer. The transducer consists of the Ni-Mn-Ga material, a linear spring, Helmholtz coils, and a soft iron housing. An enhanced phenomenological model is also presented in this work to describe the strain output of the actuator in the response to the magnetic field strength. Using this model the effect of design parameters on the performance of the actuator is studied.
Development of a Wearable Gesture Recognition System
Authors: Zhang Hong , Koo Jeong-Hoi
Published: April 2008

This paper presents an effort of developing a wearable gesture recognition system. The objective of this work is to design and build a mechatronic device that can recognize human gestures. This device can be used to help the communication between humans or humans and machines (such as unmanned vehicles). The device is composed of two main components, a data acquisition system and a gesture recognition system. The data acquisition system obtains sensory information from human motions and encodes the information for transmission to the gesture recognition system. Upon receiving the signals, the gesture recognition system decodes them such that machines can respond to the corresponding human motions. The project was conducted by a group of Mechanical Engineering students in the format of junior/senior engineering clinic. Through this project, they obtained working knowledge of a mechatronic device within a cohesive and dynamic team.
Wirebond Reliability Assessments and Layout Guidelines for a TO247 Package Using FEA
Authors: Nayak Rohit T. , Cheng Chean Fay Judy , Krishna Arvind
Published: April 2008

Automotive electronics design and manufacture present unique challenges for product reliability. Recent trends toward mounting electronic systems directly onto engines introduce a new level of severity in terms of thermal and vibration environments. Automotive microelectronic packages experience thermal stresses that can possibly cause components and electrical interconnection damage. The loss of electrical interconnection due to coarse Aluminium wires in electronic modules is one of the most critical reliability problems in automotive electronics packaging. The paper intends to help understand and investigate the reliability of Aluminium wire bonds that make the electrical connection between integrated chips and the leads inside a typical leaded electronic package like TO247. Finite element modeling (FEM) is used to simulate the stresses the package goes through during reliability tests. Results are compared to empirical testing. The FE model consists of the entire TO247 package including the leadframe, overmold, chip, substrate, Al wire loops and corresponding bond pads. Results from simulations provide information to map out high stress locations on the heels of the wirebonds due to package warp. In addition, the results also provide manufacturing engineers the insight to develop general bonding guidelines for Aluminium wires. As a result of this exercise, the development team is able to counter the issue and provide a design guideline to design the leadframe, place components away from high stress locations and pursue a more symmetrical layout to reduce the effect of thermal stresses.
Application of an HP-Adaptive Technique for Heat, Mass and Momentum Transport
Authors: Wang Xiuling , Pepper Darrell W.
Published: April 2008

A three-step hp-adaptive finite element model (FEM) is employed to solve the governing equations for incompressible flow including mass and thermal transport. The adaptive FEM uses both mesh enrichment (h-adaptation) and spectral order incensement (p-adaptation) to maximize the rate of decrease of the interpolation error. The three-step adaptive methodology can be used to solve a wide variety of problems related to incompressible viscous flow including mass dispersion along with thermal transport. Highly accurate solutions are obtained using an optimally refined final mesh. The L2 energy norm is calculated to guide the adaptation procedure. Simulation results for incompressible flow over a backward facing step, natural convection in a partitioned enclosure and mass transport within a partitioned enclosure under thermal effects are presented. Results are compared with experimental data and numerical simulations reported in the literature. The efficiency of the proposed numerical technology is discussed.
Numerical Investigation of Liquid-Liquid Coaxial Flows
Authors: Vempati Bhadraiah , Panchagnula Mahesh V. , O¨ztekin Alparslan , Neti Sudhakar
Published: April 2008

This paper presents numerical results of the interfacial dynamics of axisymmetric liquid-liquid flows when the more dense liquid is injected in with parabolic inlet velocity profile. The flow dynamics are studied as a function of the individual phase Reynolds numbers, viscosity ratio, velocity ratio, Bond number, and Capillary number. The flows have been categorized as “necking” and “swelling” based on whether the injected fluid radius is smaller or larger than the injection port radius. The jet has been observed to neck when the average inlet velocity ratio is less than unity. The outer fluid velocity has a significant effect on the shape and evolution of the jet as it progresses downstream. As the outer liquid flow rate is increased, the intact jet length is stretched to longer lengths while the jet radius is reduced due to interfacial stresses. The jet radius appears to increase with increase in Bond number and viscosity ratio while it is nearly invariant with changes in Capillary number. The results of numerical simulations using FLUENT® agree well with the results of experimental measurements and the results of self-similar solution.
Board Strain Analysis to Investigate Chassis Design Effects
Authors: Liang Frank Z. , Palanuk Larry M. , Williams Richard L. , Daharwal Paresh
Published: April 2008

A circuit board response was used to characterize five chassis that were manufactured by five different suppliers to two form factors: slim and mid-tower designs. The board responses were compared to that in a reference test chassis. All the chassis were shocked to the same input. The board response was characterized by strain gauges mounted on the PCB around critical BGA components. The board strains measurements were able to detect the manufacturing variability of the chassis fabricated and was used to identify the second level interconnection (SLI) risk for BGA placement at the measured location. This paper presents an empirically driven methodology comparing supply line chassis variation and their direct affect on BGA SLI reliability and the need to revise the procurement specification to ensure repeatable and predictable BGA or any critical SLI performance.
A Hybrid Numerical Model for Simulating Atmospheric Dispersion
Authors: Wang Xiuling , Pepper Darrell W.
Published: April 2008

A hybrid numerical model for simulating atmospheric contaminant dispersion is developed. The hybrid numerical scheme employs an hp-adaptive finite element method coupled with a Lagrangian particle transport technique to solve the governing equations for atmospheric flow and species transport. A random walk/stochastic approach is used to generate Lagrangian particles that define the contaminant dispersion traces. A coarse mesh using low order shape functions is initially generated. Both the mesh and shape function order are subsequently refined and enriched in those regions where high computational error exist. Compared with fine mesh and high order numerical solutions, the hybrid scheme produces highly accurate solutions with reduced computational cost. A general probability distribution is used in the particle transport module for the random component of motion due to turbulent diffusion. Results depicting contaminant transport and dispersion in the atmosphere are presented. The computational efficiency of the hybrid numerical model is also discussed.
Adaptive Servoregulation of a Projectile Fin Using Piezoelectric Actuator
Authors: Mani Smitha , Singh Sahjendra N. , Parimi Surya Kiran , Yim Woosoon
Published: April 2008

This paper treats the question of adaptive control of a projectile fin using a piezoelectric actuator. The hollow projectile fin is rigid, within which a flexible cantilever beam with a piezoelectric active layer is mounted. The model of the fin-beam system includes the aerodynamic moment which is a function of angle of attack of the projectile. The rotation angle of the fin is controlled by deforming the flexible beam which is hinged at the tip of the rigid fin. It is assumed that the system parameters are completely unknown and that only the fin angle and its derivative are measured for synthesis. A linear combination of the fin angle and fin’s angular rate is chosen as the controlled output variable and an adaptive servoregulator is designed for the control of the fin angle and the rejection of the disturbance input (aerodynamic moment). In the closed-loop system, the fin angle asymptotically converges to the desired value and the elastic modes converges to their equilibrium values. Computer simulation is performed which shows that in the closed-loop system, the fin angle is precisely controlled in spite of uncertainties in the fin-beam parameters and the aerodynamic moment coefficients. Furthermore, a laboratory model of the projectile fin is developed and the adaptive controller is implemented for real-time control. Experimental results are presented which show that adaptive servoregulator accomplishes fin angle control.
Minimum Rank Generalized Subspace Updating Approach for Nonlinear Systems
Authors: D’Souza Kiran , Epureanu Bogdan I.
Published: April 2008

An algorithm for analyzing a nonlinear system as an augmented linear system is presented. The method uses a nonlinear discrete model of the system and the form of the nonlinearities to create an augmented linear model of the system. A linear modal analysis technique that uses forcing that is known but not prescribed is then used to solve for the modal properties of the augmented linear system after the onset of damage. Due to the specialized form of the augmentation, nonlinear damage causes asymmetric damage in the updated matrices. A generalized minimum rank perturbation theory, which requires knowledge of both right and left eigenvectors, is developed to handle the asymmetric damage scenarios. The damage extent algorithm becomes an iterative process when an incomplete set of right eigenvectors are known. The method is demonstrated using numerical data from nonlinear 3-bay truss structures. Various damage scenarios of the nonlinear systems are used to demonstrate the effectiveness of the augmentation and the generalized minimum rank perturbation theory, and the effect of random noise on the technique. The nonlinearities included in the 3-bay truss are cubic springs.
Molecular Simulation of the Contact Angle of Water Droplet on a Platinum Surface
Authors: Shi Bo , Sinha Shashank , Dhir Vijay K.
Published: April 2008

This paper presents a molecular simulation study of the contact angles of water droplets on a platinum surface for a range of temperatures. SPC/E and Z-P model are used for the water-water and water-platinum potentials, respectively. The results show that the contact angle decreases with the increase of system temperatures and increases when the potential decreases. When the temperature is high enough, the contact angles drop to zero degrees. The results were compared with the argon-virtual solid wall and water-Aluminum results, a similar trend was found.
Measurement of the Size Effect in the Micron-Sized Structures Using the AFM
Authors: Ko Seong-Hyun , Lee Hun-Kee , Han Jun-Soo , Park Hyun Chul
Published: April 2008

Purpose of this study is to investigate the size-dependent mechanical properties in micron scale medium. Theories such as the couple stress theory and strain gradient theory explain that the deformation in the micron scale is dependent upon the size of the medium. Specimens of the cantilever type, bridge type and paddle type beam that have thickness of 900, 1000 and 1200 nm and width of 20, 30 and 50 μm were fabricated by the MEMS technique. We carried out the bending and torsion test to measure the mechanical properties such as the young’s modulus, yield strength and torsional rigidity using the AFM (Atomic Force Microscopy). In addition, the mechanical test for the AAO (Anodic Aluminum Oxide) structure was carried out.
An Exploratory Study on the Analysis of Electron Triboemission Data
Authors: Molina G. J. , Furey M. J. , Kajdas C. K.
Published: April 2008

The authors have carried out extensive measurements of electron triboemission from the scratching of selected ceramics and of semiconductors in high vacuum. Although the origin of triboemission is not clear, the authors suggest that some triboemission features relate to worn surface evolution. A bibliographic review is presented on analysis of electron triboemission data. Time-domain and frequency-domain discussion of the burst-type triboemission outputs are presented. This paper briefly summarizes key findings on triboemission and presents measurements of electron triboemission from an alumina ball and a diamond cone scratching alumina and sapphire disks. An exploratory study is focused on frequency analysis of data. The feasibility of investigating randomness vs. deterministic origin is explored for the triboemission outputs. Because key triboemission features are yet to be explained, the proposed data analysis can be a tool for such understanding.
Electrokinetic Focusing and Dispensing of Particles and Cells on Microfluidic Chips
Authors: Xuan Xiangchun , Young Edmond W. K. , Li Dongqing
Published: April 2008

This work investigated the electrokinetic focusing and dispensing of polystyrene particles and red blood cells on microfluidic chips. Particles or cells were first electrokinetically focused using the merging of focusing streams on the sample stream, and subsequently separated as a result of the focusing. These particles or cells were then selectively dispensed from the focused sample stream using precise application of electrical pulses. The whole process of focusing, separation and dispensing of particles was visualized by a custom-made microscopy system. In particular, the width of the focused fluorescein stream and the accelerated electrophoretic motion of particles and cells were measured in a cross-channel and compared with a proposed analytical model. The electrokinetic manipulation of particles and cells demonstrated in this work can be used for developing integrated lab-on-a-chip devices for studies of cells.
Channel Size Based Measurement Techniques for Condensation Heat Transfer Coefficients in Mini- and Micro-Channels
Authors: Garimella Srinivas , Agarwal Akhil , Bandhauer Todd M.
Published: April 2008

A set of techniques for the measurement of condensation heat transfer coefficients for circular and noncircular channels with 5 mm > Dh > 100 μm is presented. For the larger range of Dh (5 > Dh > 0.4 mm), single tubes or multiple parallel extruded channels are used as test sections. The test section is cooled using water at a high flow rate to ensure that the condensation side presents the governing thermal resistance. Heat exchange with a secondary cooling water stream at a much lower flow rate is used to obtain a large temperature difference, which is used to measure the condensation duty. Condensation heat transfer coefficients are measured in small quality increments for 0 < x < 1 over the mass flux range 150 < G < 750 kg/m2-s with uncertainties typically less than 20%. For 200 > Dh > 100 μm, channels are fabricated on a copper substrate by electroforming copper onto a mask patterned by X-ray lithography, and sealed by diffusion bonding. Subcooled liquid is electrically heated to the desired quality, followed by condensation in the test section. Downstream of the test section, another electric heater is used to heat the refrigerant to a superheated state. Energy balances on the pre-and post-heaters establish the refrigerant inlet and outlet states at the test section. Water at a high flow rate serves as the test section coolant to ensure that the condensation side presents the governing thermal resistance. Heat transfer coefficients are measured for 200 < G < 800 kg/m2-s for 0 < x < 1. It is demonstrated that uncertainties as low as 6% can be achieved in the measurement of condensation heat transfer coefficients.
On the Creep Behaviour at Periodic Holes in Thermal Equipment
Authors: Prabhu M. Mohan , Rao G. Venkata
Published: April 2008

A large body of literature exists on investigations carried out earlier on the effects of holes in a continuum in the elastic regime of material behavior like for instance the case of the elastic analysis of tube sheets. Mathematical and finite element methods have been presented in detail for the solution of these design problems by a large number of authors in the sixties and seventies. However, it is observed that there is a paucity of reported research investigations on the creep behavior of equipment containing periodic holes such as boiler headers, heat exchangers etc. Material creep effects near holes in a continuum appear to have been investigated only during the past fifteen years and that too restricted to a limited number of configurations. Moreover, a large number of investigations seem to have been focused on the uni-axial behavior while the state of stress in most of the equipment utilized by industry is predominantly biaxial in nature. Creep behavior of substantial number of equipment subject to biaxial loading which is commonplace in industry remains to be relatively not understood fully. In view of the important applications of these mechanical equipment in thermal power stations and in chemical plants, it is essential to address the problem of creep behavior at single, multiple and periodic holes in the material continuum subjected to biaxial loading [1,2]. In order to obtain tractable solutions to the complex problems, it is felt appropriate to carry out detailed finite element analyses aimed at obtaining the strain and stress distribution near holes in the creep regime in certain generalized configurations so that the same can be applied in equipment where an array of holes is present.
New Class of Contact Problems
Authors: Sosnovskiy Leonid A. , Shcharbakou Siarhei S.
Published: April 2008

A non-traditional approach to setting and solving contact problems and the analysis of complex stressed state of roller/shaft active system is presented in this paper.
Numerical Simulation of an ADSS With Surface Heat Flux and Heat Generation Using FEM
Authors: Prakash K. Arul , Biswas G. , Kumar B. V. Rathish
Published: April 2008

ADSS (Accelerator Driven Sub-critical System) nuclear reactors have evoked renewed interest in research because it operates in sub-critical conditions and transmutes nuclear wastes. Numerical investigation of fluid flow and heat transfer characteristics of an ADSS has been accomplished using a finite element method based on Streamline Upwind Petrov-Galerkin (SUPG) technique. The time-dependent governing equations for conservation of mass, momentum and energy are solved. The simulations have been carried out to predict the heat transfer in the spallation regime. The cases of beam window with heat flux prescription is analyzed in the absence and presence of heat generation in the liquid metal. At the first place, laminar regime of the flow is considered for the ADSS geometry. The Reynolds number of interest were varied over a specified range.
Design and Analysis of Piezoelectric Transducer Based Resonant Actuation Systems
Authors: Kim Jun-Sik , Wang K. W. , Smith Edward C.
Published: April 2008

The objective of this research is to address some of the important design issues of the recently developed piezoelectric resonant actuation system (RAS) concept. The RAS is achieved through both mechanical and electrical tailoring. With mechanical tuning, the resonant frequencies of the actuation system (includes the piezoelectric actuator and the related mechanical and electrical elements for actuation) can be adjusted to the required actuation frequencies. This obviously will increase the authority of the actuation system. To further enhance controllability and robustness, the actuation resonant peak can be significantly broadened and flattened with electrical tailoring through the aid of an electric network of inductance, resistance, and negative capacitance. Therefore, one can achieve a high authority actuator without the negative effects of resonant systems. In this investigation, the RAS is analyzed and compared to an equivalent mechanical system to provide better physical understandings. Design guidelines of the RAS are derived in a dimensionless form, and the optimal values of the electrical components are explicitly determined. A method of implementing the actuator circuitry is proposed and realized via a digital signal processor (DSP) system. Performance of the resonant actuation system is analyzed and verified experimentally on a full-scale piezoelectric tube actuator for light class helicopter rotor control. The electric power consumption of the RAS is analyzed and discussed in terms of the power factor and apparent power. It is demonstrated that a piezoelectric resonant actuation system with proper tunings not only yields high authority with a broad frequency bandwidth but also is electrically efficient in terms of power consumption.
Accurate Study of Normal Pressure Distribution in Entrance Region of Channel
Authors: Shimomukai Kensyuu , Kanda Hidesada
Published: April 2008

There are few implicit solutions available for the pressure distribution in the y-direction. Thus, for the flow between parallel plates, the pressure distribution in the entrance region was studied, focusing on the pressure gradient in the y-direction at Reynolds numbers (Re) between 100 and 5000. In the numerical method, the vorticity transport equation is first solved and then Poisson’s equation for pressure distribution is solved without any assumptions taken for pressure distribution. Consequently, the difference in pressure between the wall and the centerline existed near the inlet and decreased as Re increased. The pressure at the wall is lower than that in the central core for Re ≤ 5000. This result shows that (i) the boundary-layer assumptions do not hold for Re ≤ 5000 and (ii) the pressure distribution is contrary to Bernoulli’s law across parallel plates, although the law does not apply to viscous flow.
Application of Adaptive Neuro-Fuzzy Inference System in Field Balancing
Authors: Liu Shi , Qu Liangsheng
Published: April 2008

The field balancing of flexible rotors is one of the key techniques to reduce vibration of large rotating machinery. Although in recent decades the balancing theory has been thoroughly studied and various balancing techniques have been well developed, the present balancing methods are still remain for further improvements in accuracy and efficiency. Firstly, most balancing methods need large numbers of trial runs to obtain the vibration responses of trial weights in different correcting planes. Secondly, the vibration response in each measured section is always taken from a single sensor, and thus are lack of comprehensive vibration information of rotor. In fact, the movement of rotor is a complex spatial motion, which can’t be objectively and reliably described just with a single sensor in each bearing section. In order to overcome above shortcomings of traditional balancing methods, this paper presents a new field balancing method for flexible rotors, which is based on adaptive neuro-fuzzy inference system (ANFIS). The new method successfully applies the information fusion, ANFIS and computer simulation together. It integrates and fully utilizes the information supplied from all proximity sensors by holospectrum for enhancing the balancing efficiency and accuracy. A fuzzy model is established to simulate the mapping relationship between vibration responses and balancing weights by using the ANFIS. The inputs into ANFIS are the amplitudes and phases of integrated vibration responses, while the outputs are the mass and azimuth of balancing weights. A fuzzy set with three membership functions (MFs) is used to describe the magnitude of vibration amplitudes or of balancing weights. Another fuzzy set with five MFs is used to describe the quadrant of vibration phases or of balancing weights. Based on the historical balancing data, a combination of least-square and back-propagation gradient descent methods is then used for training ANFIS membership function and node-parameters to model input (vibration response)/output (balancing weight) data. The simulation study shows that the ANFIS can obtain satisfactory balancing result after a single trial run. At the same time, with the help of computer simulation, different correction schemes can be compared and rapidly simulated to direct balancing operation. Finally, the effectiveness of the new method was validated by the experiments on balancing rig and in the field balancing practice of several 300MW turbo-generator units.
Multiscale Characterization of Nanocomposites Fabricated by Copulverization of Epoxy Resin and Nanoclay
Authors: Aktas Levent , Dharmavaram Sudha , Altan M. Cengiz
Published: April 2008

Effect of nanoclay on the thermo-mechanical properties of BT250E-1 epoxy resin is investigated. Nanocomposite parts containing 0, 2 and 10wt. % of Cloisite® 30B nanoclay are fabricated by copulverization of nanoclay with epoxy resin at −25°C. Desired amounts of solid epoxy resin and nanoclay are placed into a grinder and copulverized for 20 seconds. The resulting fine powder is then cured using an APA2000 rheometer by using the time-temperature profile provided by the resin supplier. Five disk-shaped parts for each nanoclay content are fabricated. Two rectangular samples are cut out from each disk and used for characterization of mechanical properties and microstructure. Glass transition temperature is observed to deteriorate by 5% and 10% with the addition of 2 and 10wt. % nanoclay, respectively. Three-point bending test results indicate up to 28% improvement in flexural stiffness whereas flexural strength is observed to degrade by 57% over the range of nanoclay loading. Scanning electron microscopy indicates extensive nanoclay agglomeration. In order to characterize the nanoclay cluster morphology, several scanning electron micrographs are captured at 500x magnification. Nanoclay clusters and their size distribution are then identified by digital image processing. It is found that the average cluster size is 2-fold higher at nanocomposites containing 10wt.% nanoclay compared to 2wt.%. Transmission electron microscopy indicates several nanovoids trapped in the intra-cluster regions. The existence of these voids is also verified by density measurements of the cured samples of the epoxy with and without nanoclay. The reduction observed in the flexural strength is believed to be due to these nanovoids and nanoclay agglomeration.