bluuebunny/crossref_metadata_2025 huggingface dataset:
A Load-Based Depth-Sensing Indentation Technique for Elastic-Plastic Material Mechanical Property Evaluation
Authors: Lee K. , Tannenbaum J. M. , Kang B. S.-J. , Alvin M. A.
Published: May 2012

A load-based depth-sensing micro-indentation technique has been developed for material mechanical properties evaluation including elastic modulus, yield stress, strain hardening exponent and stress-strain curve. Based on a Hertzian contact mechanics approach, this load-based depth-sensing micro-indentation technique does not require system compliance calibration or the use of high precision depth sensors. Furthermore a unique, material independent, indentation based load-depth algorithm has been developed accounting for both elastic and elastic-plastic deformation of the material beneath the indenter. This algorithm, found to be a function of material yield stress, strain hardening exponent and elastic modulus, is shown to be the basis for obtaining a stress-strain curve. Finite element analyses of multiple materials with various mechanical properties were employed to examine and develop the fundamental indention based relationships between these variables and the load/depth curve needed to extract the stress-strain diagram. In addition, experimental results obtained with this load-based micro-indentation technique were found to yield accurate material mechanical properties (elastic modulus, strain hardening, yield strength) at room and elevated temperatures (up to 1200°C).
Swept Arc Length Measure of Abrasive Wear
Authors: Johnson Nessa , Hennessey Michael , Abraham John
Published: May 2012

A geometric theory is presented to enhance understanding of part wear and lay patterns generated during surface grinding, such as when a part is fed through a machine with a rotating circular abrasive disk. This theory uses the integrated relative speed between the part and the abrasive wheel, the swept arc length, as a wear measure. A dynamic simulation model was created in SIMULINK™ to evaluate the swept arc length computation at a single point, and a MATLAB™ script was used to provide initial conditions, spatially loop through the entire part surface, and evaluate the resultant part wear. Three common machine configurations have been dynamically modeled and evaluated using the swept arc length theory. Additionally, simulation results have been validated through comparison with industry professionals using the swept arc length as a wear measure.
Reflection and Transmission of Waves in Pyroelectric Body
Authors: Yuan Xiaoguang , Kuang ZhenBang
Published: May 2012

The reflection and transmission theory of waves in pyroelectric medium is studied in this paper. In general in an infinite homogeneous pyroelectric medium there are four bulk wave modes: quasi-longitudinal, two quasi-transversal and temperature waves. However there are five boundary conditions in the reflection and transmission problem of the pyroelectric medium. In this paper we find that the surface wave will be revealed to satisfy the boundary conditions with other four bulk waves. The surface wave has the same wave vector component with the incident bulk waves on the interface plane. The two dimensional reflection problems of waves at the interface between the semi-infinite pyroelectric medium and vacuum is researched and an numerical example is given.
A Fast Constrained Nonlinear Elastography Technique: Polyvinyl Alcohol (PVA) Phantom Study Using the Veronda-Westman Model
Authors: Amooshahi M. , Samani A.
Published: May 2012

Breast elastography has been proposed as a novel imaging modality for breast cancer detection and assessment. As pathologies are known to change tissue stiffness significantly, the idea behind elastography is using tissue stiffness as imaging contrast agent. Evidence in the literature suggests that various pathological tissues exhibit different mechanical stiffness characteristics. Therefore, in addition to the ability of detecting the presence of abnormalities, elastography is capable of pathological tissue classification. In this work, we propose a novel nonlinear (hyperelastic) breast elastography system which takes into account tissue large deformations resulting from mechanical stimulation. To idealize breast tissue, we use the well-known Veronda-Westman model as the forward problem solution in the hyperelastic parameter reconstruction process. This process involves tissue mechanical stimulation, displacement data acquisition followed by solving an inverse problem to find the hyperelastic parameters iteratively. These parameters are useful for in vivo tumor classification, image guided surgery and Virtual Reality systems development. Due to the exponential form of the Veronda-Westman function, however, this model cannot be solved using inverse-matrix techniques. Therefore, we have developed a novel technique to solve the corresponding nonlinear inverse problem. To validate the technique, we used an experimental breast tissue mimicking phantom that was made up of PVA-C (Polyvinyl Alcohol), which exhibits nonlinear mechanical behavior. Displacement data was acquired using a combination of Time Domain Cross-Correlation Estimation (TDE) and Horn-Schunck Optical Flow techniques.
Analysis, Control, and Maneuvering of Supercavitating Vehicles
Authors: Hassouneh Munther A. , Nguyen Vincent , Balachandran Balakumar , Abed Eyad H.
Published: May 2012

A dive-plane model of a supercavitating vehicle is considered and the physical basis for a time delay effect in this system is described. The time delay is on the order of the vehicle length divided by its speed. Control design is carried out to achieve stabilization of the supercavitating vehicle for trim conditions inside or outside the cavity in the presence of the time delay effect. The effectiveness of different control designs are demonstrated by carrying out numerical simulations with the nonlinear dive-plane model of the supercavitating vehicle. A preliminary investigation conducted into the utilization of an outer-loop controller for vehicle maneuvering is also presented. A numerical optimal control approach is used to study dive, move-to-point, and obstacle avoidance maneuvers of the delay-free system.
A Unified Unintrusive Discrete Approach to Sensitivity Analysis and Uncertainty Propagation in Fluid Flow Simulations
Authors: Mathur Sanjay R. , Chigullapalli Aarti , Murthy Jayathi Y.
Published: May 2012

In recent years, there has been growing interest in making computational fluid dynamics (CFD) predictions with quantifiable uncertainty. Tangent-mode sensitivity analysis and uncertainty propagation are integral components of the uncertainty quantification process. Generalized polynomial chaos (gPC) is a viable candidate for uncertainty propagation, and involves representing the dependant variables in the governing partial differential equations (pdes) as expansions in an orthogonal polynomial basis in the random variables. Deterministic coupled non-linear pdes are derived for the coefficients of the expansion, which are then solved using standard techniques. A significant drawback of this approach is its intrusiveness. In this paper, we develop a unified approach to automatic code differentiation and Galerkin-based gPC in a new finite volume solver, MEMOSA-FVM, written in C++. We exploit templating and operator overloading to perform standard mathematical operations, which are overloaded either to perform code differentiation or to address operations on polynomial expansions. The resulting solver is capable of either performing sensitivity or uncertainty propagation, with the choice being made at compile time. It is easy to read, looks like a deterministic CFD code, and can address new classes of physics automatically, without extensive re-implementation of either sensitivity or gPC equations. We perform tangent (forward) mode sensitivity analysis and Galerkin gPC-based uncertainty propagation in a variety of problems, and demonstrate the effectiveness of this approach.
On Viscoelasticity in CNT-Reinforced Polymer Composites
Authors: Yazdchi K. , Salehi M.
Published: May 2012

The nanocomposites exhibit high electrical conductivity, significant non-linear optical behavior and electroluminescence, while having substantially improved mechanical properties relative to the neat polymer. However, very limited attention has been paid to the viscoelastic behavior of nanotube reinforced polymer composites (NTRPCs). In this paper, the constitutive relation and linear viscoelastic behavior of NTRPC are studied using methods of micromechanics and nanomechanics. First, the effects of volume fraction, aspect ratio and orientation of carbon nanotubes (CNTs), on the overall elastic properties of NTRPC are obtained through a micromechanical technique based on Eshelby’s Equivalent Inclusion (EEI) and Mori-Tanaka (MT) method. Secondly, by incorporating the Dynamic Correspondence Principle (DCP), the elastic solution is extended to solve the related linear viscoelastic problem. The results of this study are in good agreement when compared with previous analytical and experimental data.
Design of Rotary-Type Flow Control Valve for Control of Water-Driven Spindle
Authors: Nakao Yohichi , Niimiya Hajime , Obayashi Takuya
Published: May 2012

Water-driven spindle was developed for producing small and precise parts by the diamond turning processes. Rotational speed of the spindle can be controlled by the flowrate supplied to the spindle. The paper describes a newly developed rotary-type flow control valve that is designed for controlling rotational speed of the water-driven spindle. In particular, the paper focuses on the establishment of the mathematical model capable of representing the characteristics of the open loop control system composed of the pump, flow control valve and spindle. Mathematical models are then derived so that a feedback control system can be designed using the models. Performances of the flow control valve and the spindle are examined through simulation as well as experiments. It is then verified that the derived mathematical models are capable of representing the performance of the system. In addition, the required positioning accuracy of valve rotation for achieving desired control of the rotational speed of the spindle is considered based on the derived linearized mathematical model.
Development of Magnetic Memory Testing System Used on Defect Detection of Drill Pipe
Authors: Zheng Wenpei , Fan Jianchun , Zhang Laibin , Wen Dong
Published: May 2012

Drill pipe is used in well drilling in oil field. Under the force of tubular columns and pressure of drilling fluids, the drill pipe usually fails in long-term service, which consequently leads to accidents, such as drill pipe twisting off, and causes stagnation of production. So it’s especially necessary to detect defects in drill pipe in time. Traditional nondestructive testing methods, for example, magnetic flux leakage, eddy current and ultrasound, can only detect already formed defects. They do not help detect and evaluate stress concentration zones, which tends to develop into defects. Magnetic memory testing technology is a newly developed nondestructive testing technology. Under the exciting of the magnetic field of the earth, the magnetic status will change in stress concentration zones of ferromagnetic material. Location and study of the stress concentration zones will forecast the defects of ferromagnetic material. Magnetic memory testing system used on defect detection for drill pipe is developed based on this technology. Composition and function of the system is introduced, and application effect is shown. This system will play important part in detection and evaluation for drill pipe in oil field.
Forensic Analysis of Belt Use Evidence in Rollover Crashes: A Methodology
Authors: Meyer Steven E. , Hock Davis A. , Oliver Arin A. , Herbst Brian R.
Published: May 2012

Recent advances in occupant protection systems have brought many new restraint technologies into our motor vehicles. These technologies include belt integrated restraints, various types of load limiters, webclamping devices and pretentioners. Additionally, recent developments in predictive roll sensor technologies have led to an increased use of rollover activated side curtain type airbags and rollover activated pretensioners. Moreover, recent upgrades and research by the National Highway Traffic Safety Administration (NHTSA) on the roof crush resistance standard, Federal Motor Vehicle Safety Standard (FMVSS) 216, as well as developing an ejection mitigation standard (FMVSS 226) will likely lead to an increased focus on restraint system performance in rollovers. Post crash analysis of various restraint system components is oftentimes necessary for evaluation of a particular restraint system’s use and performance in a given crash circumstance. With the addition of these new technologies, together with an increased frequency of rollover crashes seen in the last many years, specific techniques, protocols and methodologies for evaluating belt use evidence in these multiple impact, often times chaotic, rollover events is necessary. The subject paper reviews previous work regarding analysis of belt use evidence and expands upon those studies to include specific consideration of the current restraint system technologies and how they affect the forensic evidence left behind after a rollover crash. Real-world case examples and a systematic methodology for analysis of belt evidence in rollover crashes is presented along with photographic examples and laboratory supported quantification of associated belt loads.
Displacement Flow of Shear Thinning Fluids in Tube: The Effect of Density and Viscosity Ratio
Authors: Alba K. , Taghavi S. M. , Gharib S. , Seon T. , Martinez D. M. , Frigaard I. A.
Published: May 2012

The miscible displacement flow of non-Newtonian fluids is investigated experimentally in a 20 mm diameter pipe. Attention is paid to the effect of the density and viscosity ratios on the non-Newtonian fluid displacement. The effect of the density difference of the two fluids is discussed via a dimensionless parameter called the Atwood number, At. When the current is stabilized by the imposed flow, the ratio of the front velocity, Vf, to the mean flow velocity, V0, does not significantly change with Atwood number, similar to the Newtonian displacement [5]. The viscosity ratio of the two fluids then seems to be a critical factor on the flow field stability. It has previously been established that the increase in the mean flow velocity dampens the Kelvin-Helmholtz-like instabilities in the system [5]. However it may not be the case for the flows with very high viscosity ratios. The mean flow velocity in turn can contribute to the onset of interfacial instabilities as its value increases.
Separation System Design and Equipments Performance Optimization for High-Viscosity and High-Density Drilling Fluid
Authors: Xu Renbo , Deng Jingjiang , Liu Xiaoguang
Published: May 2012

For degassing of high-density and high-viscosity drilling fluid used in Ultra-high pressure oil & gas zones, carry out vertical separation systems, gravity separator for first and active centrifugal separator for secondary. Orthogonal experiment method for CFD simulates the flow field, Analysis operating variables, structural variables impact of efficiency; carry out the performance optimization scheme in accordance with the characteristics of flow fields.
Geometric Nonlinear Elasto-Dynamics Problems Solved by Variational Method
Authors: Liu Zongmin , Wu Guohui , Liang Lifu , Song Haiyan
Published: May 2012

With the development of hydromechanics and aeromechanics, the interest in non-conservative and non-selfadjoint problems has increased. However some traditional variational methods are not applicable to these problems, which have no energy functional in full variable form. And weighted residuals method is the general name of a series of approximate numerical methods for non-energy variational equations. Generalized Galerkin method is just one of weighted residual method, which is engineer’s experience summary in long practical applied process for the numerical analysis methods. Generalized Galerkin method is often used for dynamic response problems. In this paper, the general process for solving geometric nonlinear elasto-dynamics problem in non-conservative system is presented. The vibration problem of elastic thin plate with large deflection in non-conservative system is solved by generalized Galerkin method. Finally, some correlative problems are discussed.
Computational Fluid Dynamics Analysis of the Performance of Three Hemodialysis Catheters
Authors: Elkhoury M. , Youssef N. , Issa C.
Published: May 2012

In this study, FLUENT (computational fluid dynamics software) is utilized to compare the performance of three widely used hemodialysis catheters, Niagara double lumen, Flexxicon II double lumen and Hemosplit long-term catheters of BARD Access Systems, in terms of blood flow rate and shorter exposure time. Running the three models at a fixed blood flow rate of 300 ml/min, it is found that Niagara catheter displays the lowest shear rates, yet high enough to induce thrombosis, which occurs as a result of platelet aggregation. High vorticity magnitudes exceeding 50,000s−1 are detected near the venous luminal walls of the Hemosplit catheter rendering the formation of Hemolysis which causes free toxic hemoglobin to circulate in the blood stream. Furthermore, the highest shear rates are found to occur at the arterial inlet, downstream the openings where inflow of blood occurs. It was found that the Niagara catheter, with open side holes, is the most recommended among the three considered catheters.
Modeling of Cell Deformation Under External Force Using Neural Network
Authors: Ahmadian M. T. , Vossoughi G. R. , Abbasi A. A. , Raeissi P.
Published: May 2012

Embryogenesis, regeneration and cell differentiation in microbiological entities are influenced by mechanical forces. Therefore, development of mechanical properties of these materials is important. Neural network technique is a useful method which can be used to obtain cell deformation by the means of force-geometric deformation data or vice versa. Prior to insertion in the needle injection process, deformation and geometry of cell under external point-load is a key element to understand the interaction between cell and needle. In this paper the goal is the prediction of cell membrane deformation under a certain force, and to visually estimate the force of indentation on the membrane from membrane geometries. The neural network input and output parameters are associated to a three dimensional model without the assumption of the adherent affects. The neural network is modeled by applying error back propagation algorithm. In order to validate the strength of the developed neural network model, the results are compared with the experimental data on mouse oocyte and mouse embryos that are captured from literature. The results of the modeling match nicely the experimental findings.
Creep Behavior of a TWARON®/Natural Rubber Composite
Authors: David N. V. , Gao X.-L. , Zheng J. Q.
Published: May 2012

The creep behavior of a Twaron CT709® fabric/natural rubber composite under a uniaxial constant stress is studied using three viscoelasticity models with different levels of complexity and a newly developed para-rheological model. The three models employed are a one-term generalized Maxwell (GMn = 1) model (consisting of one Maxwell element and an additional spring in parallel), a two-term generalized Maxwell (GMn = 2) model (including two parallel Maxwell elements and an additional spring in parallel), and a four-parameter Burgers model. The values of the parameters involved in each model are extracted from the experimental data obtained in this study. The creep tests reveal that the axial strain starts to increase exponentially during the primary stage and then continues to equilibrate linearly with time. The results show that the initial creep response of the composite is predicted fairly well by the GMn = 2 model, while the secondary creep is more accurately described by the GMn = 1 model. An implicit solution, together with a characteristic retardation time spectrum, obtained using the para-rheological model is found to provide more accurate predictions of the composite creep response than the three viscoelasticity models at both the primary and secondary stages.
Numerical Simulation of Hydraulic Transients in Long Corridor Surge Tank
Authors: Yu Xiaodong , Zhang Jian , Hazrati Arash , Chen Sheng
Published: May 2012

A numerical model of fluid transients in long corridor surge tank, based on the equations of Saint-Venant, is developed. The implicit method of Preissman, with appropriate boundary conditions, is used to solve these two nonlinear partial differential equations. The hydraulic transients with new model and normal surge tank model are simulated and compared with model experiments. It is clarified that the new numerical model can simulate the changes of water level in long corridor surge tank and pressure along penstock realistically. The new model provides scientific basis for studying hydraulic transients of hydropower station with long corridor surge tank.
A Study of Convective Heat Transfer and Pressure Drop Phenomena in Curved Microchannels
Authors: Tang Heng-Chih , Jen Tien-Chien , Yen Yi-Hsin , Teng Jyh-Tong
Published: May 2012

The research conducted in this paper was based on numerical simulation analysis that investigated the relationships between convective heat transfer and pressure drops and the flow patterns between conventional straight channels and curved microchannels. The main goal is to thoroughly investigate thermo-fluidic phenomena in curved microchannels and to determine the optimal design for the curved microchannel cooling system. Commercial numerical software (ESI-CFD) was used to simulate all cases studied in this paper. The computer simulated results were compared with actual experimental results to evaluate its accuracy. Six cases of different dimensions were studied. Results obtained from this study showed that when the dimensions of curved microchannels are smaller than 40 μm in height, conventional macro fluidic theory can still be used, since the numerically simulated results are in good agreement (<6% difference) with those obtained experimentally. Hydraulic diameter is the factor affects the pressure drop. Larger hydraulic diameter causes smaller pressure drop while smaller hydraulic diameter results in higher pressure drop. Secondary flow patterns and Nusselt numbers are also illustrated in this paper. When the Dean number is lower than 400, the pressure drop of fluid in 40 μm height models is similar to that found in straight microchannels. For the velocity profiles in the curved microchannels, the main stream is at the center of the curved microchannel first. But it is gradually offsets to the outer wall when the mass flow rates increases. The centrifugal force due to the curve geometry is the main reason that results in the shifting of the main flow toward the outer wall of the microchannel.
A Numerical Study of the Effect of Blind Opening on Laminar-to-Turbulent Transition in the Flow Over a Simple Recessed Window-Plane Blind System
Authors: Oosthuizen Patrick H. , Naylor David
Published: May 2012

Most numerical studies of convective heat transfer between a window-blind system and a room are based on the assumption that the flow remains laminar. However, in the case of larger windows it is to be expected that transition to turbulent flow will occur in the system. The aim of the present study was to numerically determine when transition to turbulent flow occurs in a recessed window system and the effect of a simple partially open plane blind on when transition occurs. An approximate model of a recessed window that is covered by a partially open plane blind has been considered. The inner surface of the window is modeled as a plane vertical isothermal surface and the blind as a thin plane surface that offers no resistance to heat transfer. The fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces, this being dealt with using the Boussinesq approach. Radiant heat transfer effects have been neglected. The k-epsilon turbulence model with the full effects of the buoyancy forces being accounted for has been used in obtaining the solution. The governing equations have been solved using the commercial finite-volume based cfd code FLUENT. The solution has as parameters: (1) the Rayleigh number, (2) the Prandtl number, (3) the dimensionless ‘window’ recess depth, (4) the dimensionless blind opening, and (5) whether the ‘window’ surface is at a higher or lower temperature than the room air. Because of the application being considered results have only been obtained for Pr = 0.7 and for the case where the ‘window’ surface is at a higher temperature than the room air. The effect of transition on the mean Nusselt number variation with Rayleigh number with various blind openings for various dimensionless window recess depths has in particular been studied.
Mechanical and Thermal Properties of Highly Organized Nanowire-Alumina Nanocomposites
Authors: Rivera Johan , Englander Ongi
Published: May 2012

The use of porous anodic alumina allows for the fabrication of highly ordered unidirectional nanowire composites. Sol gel deposition was used in the successful fabrication of zirconia-alumina and zinc oxide-alumina nanocomposites. Silicon-alumina and germanium-alumina nanocomposites were fabricated via catalyst-assisted chemical vapor deposition. The mechanical and thermal properties of these alumina nanocomposites were investigated. The Vickers hardness of the different nanocomposites was established by means of microindentation. Vickers testing was performed at room temperature and after specified heat treatments. The high temperature treatments were performed in order to assess the effect of an annealing step on the properties of the nanocomposites. Thermal cycling experiments were performed to test the nanocomposites’ compatibility with recurring high temperature environments.
Design of a Steady-State, Parallel-Plate Thermal Conductivity Apparatus for Nanofluids and Comparative Measurements With Transient HWTC Apparatus
Authors: Kostic Milivoje M. , Walleck Casey J.
Published: May 2012

A steady-state, parallel-plate thermal conductivity (PPTC) apparatus has been developed and used for comparative measurements of complex POLY-nanofluids, in order to compare results with the corresponding measurements using the transient, hotwire thermal conductivity (HWTC) apparatus. The related measurements in the literature, mostly with HWTC method, have been inconsistent and with measured thermal conductivities far beyond prediction using the well-known mixture theory. The objective was to check out if existing and well-established HWTC method might have some unknown issues while measuring TC of complex nano-mixture suspensions, like electro-magnetic phenomena, undetectable hot-wire vibrations, and others. These initial and limited measurements have shown considerable difference between the two methods, where the TC enhancements measured with PPTC apparatus were about three times smaller than with HWTC apparatus, the former data being much closer to the mixture theory prediction. However, the influence of measurement method is not conclusive since it has been observed that the complex nano-mixture suspensions were very unstable during the lengthy steady-state measurements as compared to rather quick transient HWTC method. The nanofluid suspension instability might be the main reason for very inconsistent results in the literature. It is necessary to expend investigation with more stable nano-mixture suspensions.
Optical Density Measurements and Analysis for Single-Mode Initial-Condition Buoyancy-Driven Mixing
Authors: Doron Yuval , Duggleby Andrew
Published: May 2012

The Texas A&M water channel experiment is modified to examine the effect of single-mode initial conditions on the development of buoyancy-driven mixing (Rayleigh-Taylor) with small density differences (low-Atwood number). Two separated stratified streams of ∼ 5°C difference are convected and unified at the end of a splitter plate outfitted with a servo-controlled flapper. The top (cold) stream is dyed with Nigrosine and density is measured optically through the Beer-Lambert law. Quantification of the subtle differences between different initial conditions required the optical measurement uncertainties to be significantly reduced. Modifications include a near-uniform backlighting provided through quality, repeatable, professional studio flashes impinging on a white-diffusive surface. Also, a black, absorptive shroud isolates the experiment and the optical path from reflections. Furthermore, only the red channel is used in the Nikon D90 CCD camera where Nigrosine optical scatterring is lower. This new optical setup results in less than 1% uncertainty in density measurements, and 2.5% uncertainty in convective velocity. With the Atwood uncertainty reduced to 4% using a densitometer, the overall mixing height and time uncertainty was reduced to 5% and 3.5%, respectively. Initial single-mode wavelengths of 2, 3, 4, 6, and 8 cm were examined as well as the baseline case where no perturbations were imposed. All non-baseline cases commence with a constant velocity which then slows, eventually approaching the baseline case. Larger wavelengths grow faster, as well as homogenize the flow at a faster rate. The mixing width growth rates were shown to be dependent on initial conditions, slightly outside of experimental uncertainty.
Development of π–Shape Parametric Resonators Including Torsional Self Pumping Springs
Authors: Kim Jin-Ha , Lee Seung Hoon , Lee Joung A. , Shim Seung-Bo , Lee Kwang-Cheol , Lee Seung S.
Published: May 2012

Materializing NEMS devices incorporating nonlinear dynamics is of fundamental importance in the field of small-scale mechanics and general science. Among these, parametric amplification draws considerable attention due to its unique characteristic. In this paper, we introduce novel designs for mechanically pumped parametric resonators in which torsional pumping springs are linked. The proposed parametric resonators can increase signal amplitude by matching resonances in a cantilever and beam. Amplitudes of resonators increase when resonances of cantilevers are amplified by torsional pumping from linked beams. In an attempt to transmit pure torsion (not displacement), zero-displacement points method is suggested, and the analytical prediction results are further verified by the corresponding simulation results obtained from COMSOL Multiphysics®. The π-shape resonators are fabricated by surface nano-machining process, and the horizontal dimensions of fabricated beams and cantilever are 31.6 um and 8 um, respectively. By using magnetomotive method, resonance frequencies are measured. Finally frequency matching is performed by DC tuning. When 54 V is applied, fdrive and fpump increase 0.78% and 0.16%, and the frequencies are exactly matched as 4.463 MHz.
Nonlinear Random Vibration of Functionally Graded Plates
Authors: Dogan Vedat
Published: May 2012

The nonlinear random vibration of functionally graded plates under random excitation is presented. Material properties are assumed to be independent of temperature. The plates are assumed to have isotropic, two-constituent material distribution through the thickness. The modulus of elasticity, thermal expansion coefficient and density vary according to a power-law distribution in terms of the volume fractions of the constituents. The Classical Plate Theory (CPT) is employed for analytical formulations. Geometric nonlinearity due to in-plane stretching and von Karman type is considered. A Monte Carlo simulation of stationary random processes, multi-mode Galerkin-like approach, and numerical integration procedures are used to develop linear and nonlinear response solutions of clamped functionally graded plates. Uniform temperature distributions through the plate are assumed. Numerical results include time domain response histories, root mean square (RMS) values and response spectral densities. Effects of material composition and temperature rise are also investigated.
Forced Vibrations of Slacked Carbon Nanotube Resonators
Authors: Ouakad Hassen M. , Younis Mohammad I.
Published: May 2012

In this paper, we present an investigation of the dynamics of electrically actuated carbon nanotubes (CNTs) resonators including the effect of their initial curvature due to fabrication (slack). A nonlinear arch model is used to simulate the motion of the slacked CNT. A reduced-order model using a multimode Galerkin procedure based on the mode shapes of the straight un-actuated CNTs is derived. The reduced-order model equations are integrated numerically with time to reveal the steady-state response of the CNT when actuated by a DC load superimposed to an AC harmonic load. A perturbation method, the method of multiple scales, is used to obtain analytically the forced vibration response due to DC and small AC loads for various slacked CNT. Results of the perturbation method are verified with those obtained by numerically integrating the reduced-order model equations. The effective nonlinearity of the CNT is calculated as function of the slack and the DC load while using a beam model for the CNTs showing a softening dominant behavior.
A Fatigue Test Method for Tire Specimens
Authors: Cha Dong-Wook , Jeong Hyun-Yong
Published: May 2012

Crack growth in tires plays an important role in the durability of tires, and it is necessary to evaluate the characteristics of crack growth accurately. Since a tire is subjected to interlaminar shear stresses, a Mode III fatigue test method was developed. The fatigue life of three different tire specimens was measured by using the fatigue test method. Based on the fatigue test results, the effects of heat aging, temperature and belt stiffness on crack growth were analyzed.
Robotic Interfaces Through Virtual Reality Technology
Authors: Streusand David B. , Steuben John , Turner Cameron J.
Published: May 2012

Virtual reality, the ability to view and interact with virtual environments, has changed the way the world solves problems and accomplishes goals. The ability to control a person’s perceptions and interactions with a virtual environment allows programmers to create situations that can be used in numerous fields. Virtual interaction can go from a computer program to an immersive experience with realistic sounds, smells, visuals, and even touch. Research in virtual reality has covered human interaction with virtual reality, different potential applications, and different techniques in creating the virtual environments. This paper reviews several key areas of virtual reality technology and related applications. An application that has large implications for our research is the control of robotic systems. Robotic systems are only as smart as their programming. This limitation often limits the utility of robotic applications in otherwise desirable circumstances. Virtual reality technologies offer the ability to couple the intelligence of a human operator with a physical robotic implementation through a user-friendly virtualized interface. This early-stage research aims to develop a technological foundation that will ultimately lead to a virtual teleoperation interface for robotics in hazardous applications. The resulting system may have applications in nuclear material handling, chemical and pharmaceutical manufacturing, and biomedical research fields.
Diagnosis via NURBs Metamodel
Authors: Turner Cameron J.
Published: May 2012

In vivo tissue condition diagnosis is a challenging engineering problem. The goal is to develop a technology that can eliminate tissue removal and external examination and enable less invasive surgical techniques to be used with a precision provided by a knowledge of the tissue within the body. Particularly challenging is the task of automating the diagnosis of the tissue condition. In this work, a metamodeling technique based on Non-Uniform Rational B-splines is used to analyze and automate the diagnosis of human tissue conditions. The resulting diagnoses are compared to results from medical doctors and the challenges in such data analysis are discussed. The technique has implications for both biomedical and electromechical system fault diagnosis and diagnostics.
Teaching Design Methodologies Across Engineering Disciplines
Authors: Turner Cameron J.
Published: May 2012

The Colorado School of Mines (CSM) offers a combined capstone design experience for mechanical, civil, electrical and environmental engineering students. In a recent re-invention of our design curriculum, a new emphasis on design methodologies has been implemented. Many of these design methods have origins in the design of electro-mechanical products, and it is certainly in these areas where the most vibrant design communities seem to reside. Yet in a combined setting, analogous design processes appear to exist in a broader engineering design community. This paper describes the capstone design program at CSM, with a focus on the methods that we are teaching and how they translate between disciplines. The lessons learned in such a translation not only illuminate how engineering design may differ in other disciplines, but also may reveal new perspectives on mechanical design processes.
Study on a Francis Turbine With Super-Low Specific Speed Applied in Cooling Towers
Authors: Zhang Limin , Zheng Yuan , Zhou Daqing , Mao Yuanting
Published: May 2012

The surplus water head of the industrial cooling tower is generally 4 to 15 meters. Using the surplus water head, a Francis turbine with super-low specific speed is designed to replace the fan motor in the cooling tower, which may achieve the purpose of power saving. This turbine is different from the conventional turbine used in hydropower station. To drive the fan to a rated speed, the turbine is required to have high efficiency and small size to meet the installation requirements under a certain flow or water head. Little research work on this type of turbine has been done home and abroad. In this paper, the runner blade airfoil was chiefly designed by three-dimensional numerical simulation through the whole flow passage of the turbine. According to the features of the turbine’s work environment, metal elliptical volute and single row ring guide vanes were applied in the structural design. By comparison and analysis an optimal model of which the efficiency can reach 86% was selected to make the physical model. The model test shows that the designed super-low specific speed Francis turbine can meet the dimension requirement and has high efficiency of 85.3% and stable performance that can be popularized and applied in the capable local places. The new type Francis turbine with super-low specific speed studied and developed in this paper can achieve the goal of reducing the energy consumption of the cooling tower. It can provide reference of using the surplus energy to the other industry.
Enhancing Student Engagement in Engineering Statics With Online Tools
Authors: Howard A. K. T.
Published: May 2012

Engineering Statics at North Carolina State University is taught to both distance-education and on-campus sections simultaneously. Statics has been remodeled to include online and in-class tools to encourage all students to stay actively engaged with the material. Seven online tools which have been incorporated into the redesigned course are presented and discussed: review modules, reading introductions and quizzes, class notes with video example problems, recorded lectures, skills quizzes, synchronous office hours and asynchronous message boards, and clickers. Results indicate students come to class consistently, are more likely to complete readings, and appreciate the just-in-time online resources. One faculty member can now supervise larger numbers of students and homework grading has been cut in half.
Parallel-Path Compliant Structures as Electrical Interconnects
Authors: Okereke Raphael , Kacker Karan , Sitaraman Suresh K.
Published: May 2012

The coefficient of thermal expansion (CTE) mismatch between a die and an organic substrate generates high stresses in the die when underfilled solder bumps are used. These high stresses could crack or delaminate low-K dielectric materials in the next-generation flip-chip devices. In addition to such on-chip failures, the solder interconnects could fail due to thermo-mechanical fatigue, especially when the interconnect dimensions are scaled down to meet fine-pitch requirements. To address these reliability issues, compliant interconnects have been proposed to alleviate the thermo-mechanical stresses in the chip assembly. Some of the challenges to be addressed with compliant interconnects are: higher electrical parasitic compared to solder bumps, cost-effective fabrication, and high-yield, fine-pitch assembly process. This paper presents a study on a parallel-path compliant interconnect design which attempts to balance between mechanical compliance and electrical parasitics by using multiple electrical paths in place of a single electrical path. The high compliance of the parallel-path compliant interconnect structure will ensure the reliability of low-K dies. Also, these interconnects can be cost effective by using a wafer-level process and by eliminating the underfill process. Although an underfill is not required for thermo-mechanical reliability purposes, an underfill may be used for reducing contamination and oxidation of the interconnects and also to provide additional rigidity against mechanical loads. Therefore, this paper also examines the role of an underfill on the thermo-mechanical reliability of a parallel-path compliant interconnect.
Mechanical Properties of Hemp-Reinforced Biomimicked Composites
Authors: Summe Martin , Allameh Seyed
Published: May 2012

Hemp-reinforced biomimicked composites (HRBC) were fabricated and tested under various mechanical testing configurations. The results were compared with the results of similar composites made with and without fiberglass reinforcement. In general, hemp reinforcement increases the tensile and bending strength of the composites. The tensile strength of the HRBC is greater than non-reinforced biomimicked composite (BC). However, this value is smaller than the tensile strength of fiberglass reinforced biomimicked composite (FRBC). The fracture toughness of HRBC was found to be close to that of FRBC, nearly seven times that of monolithic structural material.
Modeling of Shear Heating in Elastohydrodynamic Lubrication of Piston Skirts by Considering Different Viscosity Oils in Initial Engine Start Up
Authors: Malik M. Afzaal , Qasim Syed Adnan , Khan Mumtaz Ali , Mufti Riaz A.
Published: May 2012

The presence of fully established elastohydrodynamic lubricating (EHL) film between piston skirt and cylinder liner during normal engine operation prevents adhesive wear, piston noise and slap. The absence of EHL in the initial engine start up fails to prevent the same. During normal engine operation, thermal loading due to combustion dominates piston skirts lubrication. However, in a few initial cold engine start up cycles, shear heating may be assumed to considerably affect the lubricant viscosity and other characteristics. This study undertakes a 2-D EHL modeling of piston lubrication by incorporating shear heating effects due to lubricant flow between skirts and liner surfaces. The EHL film profile is predicted by solving the 2-D Reynolds equation using inverse solution technique and the finite difference method in fully flooded lubrication conditions. The temperature distribution within oil film is given by using the 2-D transient thermal energy equation with heat generated by viscous heating. The numerical analysis is based on energy equation having adiabatic conduction and convective heat transfer with no source term effects. The study is extended to a number of engine lubricants having different viscosities to investigate the extent of adverse effects due to temperature rise on load carrying capacity of lubricants. Numerical simulations show that piston eccentricities, film thickness profiles, hydrodynamic and EHL pressures visibly change when using different viscosity grade engine lubricants. This study suggests that a lubricant of appropriate viscosity can be optimized keeping in view the vulnerability of piston skirts and cylinder liner to adhesive wear at the time of initial engine start up.
Arbitrary Angular Displacement of Single Flexible Arm Using Mirrored Trajectory Planning
Authors: Huang Tung-Yung , Tsao Jen-Chieh , Huang Chi-Wei
Published: May 2012

This paper aims at planning the trajectory of an arbitrary angular displacement of single flexible arm to eliminate the residual flexural vibration. Though the concept of neutral points of flexural vibration was proposed, the strategy hasn’t been really extended to arbitrary angular displacement yet. Recently, the rest-to-rest motion for arbitrary angular displacement has been successfully dealt with different schemes; however, the flexible beam’s dynamic model wasn’t used to deduce their rules. This paper proposed to use mirror phenomenon to physically interpret the coincidence of half travel and a neutral point, and thereby deduce the trajectory planning scheme based on the flexural vibration model. The symmetric T-curve velocity profile is chosen to make the approach general. Having the angular acceleration fixed in the T curve, the trajectory planning problem reduces to the duration adjustment problem of the T-curve for the desired displacement with the imposed constraint of half travel at a neutral point. The simulation results demonstrate that a properly mirrored trajectory may successfully counteract the flexural vibration even tracking is made by a simple PD controller.
Analysis of Steam Turbine Instabilities of a 100 MW Combined Cycle Power Plant
Authors: Becerra Villanueva Jose´ A. , Jime´nez-Espadafor Aguilar Francisco J. , Carvajal Trujillo Elisa , Chacartegui Rami´rez Ricardo , Torres Garci´a Miguel
Published: May 2012

An analysis of the vibration field of the steam turbine in a combined cycle power plant has been used to identify the causes of the plant rejection at commissioning. The steam turbine group consists of a high pressure turbine connected through a gear box to a medium and low pressure turbine. The high vibration level in the main steam turbine journal bearings caused the plant can’t reach nominal power 100 MW, and at approximately 43 MW the plant was rejected. Vibration is measured through proximity non-contact sensors (two per bearing at 90°), which give relative displacements between shafts and the bearing housing. Accelerometers are also located in the bearing housing. The analysis carried out included: • Field measurements; • Critical speeds dynamic model (API 684 guidelines); • Comparison with the API 684 stability test. As a result of this study, the authors found that excessive vibration was caused by a rotor instability phenomenon, “steam whirl”, and that it led to plant rejection. The main conclusions from this work are: • The vibration rejection of the combined cycle plant was due to an excess in the maximum permissible vibration value at synchronism speed, which always occurred at 43 MW. • The excessive vibration level was caused by rotor instabilities at the rotor shaft in the high-pressure steam turbine. The main vibratory energy was concentrated in a frequency range 0.38–0.41 × rpm. • The main instability phenomenon was identified as “steam whirl”. • The protocol used as a tool in the stability analysis of the turbine, defined in API 684, shows that the logarithmic decrement at the first modal frequency in the most dangerous situation (minimum gap in bearings) has a value of 0.149, which is higher than the stability threshold defined in the API 684 specification (0.1). In this way, and according to the stability analysis, the steam turbine design would be safe despite the fact that the instability problem appeared.