bluuebunny/crossref_metadata_2025_split huggingface dataset:
Toughness Enhancement in Blends of Dissimilar Polymers Due to the In-Situ Formation by Chaotic Mixing of Fine-Scale Extended Structures at Low Minor Phase Concentrations
Authors: Liu Y. H. , Zumbrunnen D. A. 
Published: March 2022

Abstract
Experimental results are presented to demonstrate that significant improvements to the impact properties of a polystyrene (PS) matrix can be achieved by the addition of only 9% by volume of low density polyethylene (LDPE). Polymer blends of LDPE and PS were combined in the molten state within a cylindrical cavity where a quiescent, three-dimensional chaotic mixing process was performed. Whereas a minor phase normally adopts the form of highly distributed droplets in conventional processing techniques, minor phase bodies were stretched and folded recursively to yield fine-scale extended and interconnected structures. The structures were largely preserved upon solidification. Impact tests were carried out on specimens which were machined from the solidified blend. Fracture surfaces of the impact test specimens were examined by scanning electron microscopy. Blends achieved a maximum impact toughness 69% higher than that of PS. Results demonstrate potential improvements in properties that may be obtained if favorable and unique microstructures are formed directly in the melt during processing, even when major and minor phases are dissimilar.
Raman Investigation and Mechanical Behavior of Zirconia
Authors: Gogotsi George G. 
Published: March 2022

Abstract
Raman microprobe analysis was performed of partially-stabilized ZrO2 ceramics and single crystals using the samples which were preliminary indented with a Vickers indenter at room temperature or subjected to bending at low temperatures. The addition of ferric oxide into Y-PSZ ceramics was found to intensify martensitic phase transformation in it and to enhance its fracture toughness. For single crystals the tetragonal-to-monoclinic phase transformation was found possible at fracture. It was established that inelastic Mg-PSZ ceramics at −50°...−60°C becomes in fact elastic but no relevant changes in Raman spectra were observed. A conclusion was made that further investigations are required to specify the known micromechanisms which govern the behavior of ZrO2 materials under loading.
Strength Distribution and Size Effects for the Fracture of Fibrous Composite Materials
Authors: Phoenix S. Leigh , Beyerlein Irene J. 
Published: March 2022

Abstract
Random network models have recently been developed in the physics literature to explain the strength and size effect in heterogeneous materials. Applications have included the breakdown of random fuse networks, dielectric breakdown and brittle fracture. Unfortunately, conventional scaling approaches of statistical mechanics have yielded incorrect predictions, and new approaches have been proposed which build on field enhancement occurring near the tips of critical, random clusters together with the statistical theory of extremes. New distributions and size scalings for strength have been proposed and supported through Monte Carlo simulation. Here we consider an idealized, one-dimensional model for the failure of such networks where elements of constant strength may be initially present or absent at random. Our idealized rule for local stress redistribution near breaks reflects features we find in a discrete mechanics model that has limiting forms consistent with continuum theories for cracks. We obtain rigorous asymptotic results for the strength distribution and size effect with constants and exponents that are known. The validity of various analytical approximations in the literature is then discussed.
Non-Uniqueness of Two Inverse Problems of Thermally and Force-Loaded Smart Structures: Sensor Shaping and Actuator Shaping Problem
Authors: Irschik Hans , Belyaev Alexander K. , Krommer Michael , Schlacher Kurt 
Published: March 2022

Abstract
Flexural vibrations of smart beams with integrated piezoelectric actuators and sensors are considered. For the case of a spatial variation of the sensor/actuator activity, actuator and sensor equations are derived taking into account the interaction of mechanical, electrical and thermal fields. Self-sensing actuators are included. With respect to the non-uniform spatial distribution of the sensors/actuators, shaping problems are formulated. Possible non-uniqueness of these inverse problems is pointed out. Shape functions responsible for non-uniqueness of the shaping problems are termed nilpotent solutions. Within the context of simplified sensor/actuator equations widely used in the literature, a class of nilpotent shape functions is derived for redundant beams by analogy to an auxiliary quasi-static problem of thermally induced flexure. Nilpotent shape functions of the sensor/actuator shaping problem thus turn out to correspond to bending moments in the auxiliary thermoelastic problem.
Computation of the Maximum Amplitude of a Mistuned Bladed Disk Assembly via Infinity Norm
Authors: Sinha Alok 
Published: March 2022

Abstract
The maximum amplitude of a mistuned bladed disk assembly has been computed on the basis of the infinity norm of a complex matrix relating amplitudes and phases of blades’ vibration and sinusoidal forcing functions. Numerical results are presented for a model containing a single degree of freedom per blade. In addition, minimum values of the maximum amplitude have also been computed along with their sensitivities to small changes in mistuning parameters.
Static Indentation and Low Velocity Impact Tests on Sandwich Plates
Authors: Ferri Rocco , Sankar Bhavani V. 
Published: March 2022

Abstract
Quasi-static indentation tests and drop-weight impact tests were performed on graphite/bismaleimide (GR/BMI) laminates as well as on foam-core sandwich panels. Impact tests on 8-ply laminates show that the response and damage are similar to quasi-static results. Quasi-static and impact test results on sandwich panels show that the overall response is dependent upon the response of the face sheets and the core. An increase in core density increases the overall load level, panel stiffness, core fracture toughness, and decreases the core compression. A decrease in core thickness decreases the panel stiffness and energy absorption. If the radius of the indenter is greater than the core thickness, penetration of the panel will be delayed and the failure load of the bottom face sheet will increase. The quasi-static and impact responses have the same overall trend, however, the load levels increase in impact tests due to dynamic effects.
Forced Response Prediction of Gas Turbine Rotor Blades
Authors: Hilbert Gary R. , Ni Ron-Ho , Takahashi Ronald K. 
Published: March 2022

Abstract
An analytical forced response prediction system is used to predict turbomachinery airfoil vibratory stress amplitudes. The forced airfoil vibration can be caused by time dependent (unsteady) aerodynamic loads due to interaction with the flow field from neighboring airfoils rows, such as shocks, wakes, or pressure waves, or due to self induced unsteady aerodynamics such as vortex shedding and unsteady tip vortices. The amplitude of the forced response is of particular interest when the frequency of the time dependent unsteadiness is close to the natural frequency of the forced airfoil. At this condition, the airfoil is at or near resonance and vibratory stress can exceed the material capability causing high cycle fatigue (HCF) failures.
The airfoil forced response prediction system presented here combines structural static and dynamic analysis with steady and unsteady computational fluid dynamic analysis in an iterative coupled solution to the aeroelastic problem. The system includes three dimensional viscous multistage steady and unsteady computational fluid dynamics and three dimensional geometric nonlinear structural static, linear free vibration and modal forced response analysis to predict the airfoil amplitude in the resonance modes during engine operation.
This analysis system is being used to help identify the cause of HCF failure and determine corrective action. The analysis system is demonstrated using a compressor rotor excited by upstream and downstream vanes. Results are then compared with engine test data.
On the Structure of Turbulent Bubbly Gas-Liquid Flows
Authors: Roy Ramendra P. 
Published: March 2022

Abstract
To gain understanding of the structure of turbulent bubbly gas (or vapor)-liquid flows, local measurements have been carried out in the bubbly regime of isothermal gas-liquid flow and boiling flow. The isothermal flow was created by injecting nitrogen gas into an upward flow of liquid Refrigerant-113 through a vertical pipe. The boiling flow, of Refrigerant-113, was created in a vertical annular channel whose inner wall was heated. In both flows, the radial distributions of gas (or vapor) residence time fraction, bubble mean axial velocity, and bubble diameter were measured by a dual-sensor fiberoptic probe. In the liquid phase of the flows, the radial distributions of mean axial and radial velocities, axial and radial turbulent intensities, and axial Reynolds shear stress were measured by a two-component laser Doppler velocimeter (LDV). The radial distributions of bubble mean axial velocity and axial velocity fluctuation intensity were also measured by the LDV. Vapor and liquid temperature radial distributions in boiling flow were obtained by a fast-response microthermocouple.
A multidimensional two-fluid model of turbulent bubbly gas (or vapor)-liquid flow is being developed at Electricité de France with contribution from our experimental and turbulence modeling work.
Pore-Scale Modeling of Enhanced Vapor Diffusion in Porous Media
Authors: Webb Stephen W. , Ho Clifford K. 
Published: March 2022

Abstract
Vapor diffusion in porous media in the presence of its own liquid has often been analyzed similar to air diffusion. Air diffusion rate is much lower than in free space due to the presence of the porous medium and any liquid present. However, enhanced vapor diffusion has also been postulated such that the diffusion rate may approach free-space values. The mechanisms postulated to account for this enhancement include condensation/evaporation across isolated liquid islands in the porous media and an increased temperature gradient in the gas phase. In order to try to understand the mechanisms involved in such an enhancement, pore-scale models have been developed. Vapor diffusion in the presence of liquid islands has been evaluated for a one-dimensional linear system, a two-dimensional pore, and a small two-dimensional pore network under a concentration gradient. The simulations show that significant enhancement of vapor diffusion is indeed possible in the presence of liquid islands, while air diffusion decreases slightly. While the present pore-scale model indicates that enhanced vapor diffusion is possible, only experimental data can confirm the relevant processes.
Predicted Thermally Induced Stresses in a Glass Fiber Epoxy Bonded Into an Elliptical Enclosure
Authors: Uschitsky M. , Suhir E. 
Published: March 2022

Abstract
Thermally induced stresses in an optical glass fiber epoxy bonded into a thin-walled elliptical metal enclosure are analyzed. The emphasis is on the fiber microbending and possible buckling. The adverse effect of voids in the epoxy on the stresses in the fiber and in the epoxy itself is also addressed. The developed analytical models are easy-to-use, and clearly indicate the role of various geometrical and materials factors affecting the fiber propensity to buckling and its delamination from the epoxy. The obtained results can be used in the analysis and design of optical fiber structures epoxy bonded into elliptical enclosures.
Transient, Three-Dimensional Heat Transfer Model for the Laser Assisted Machining of Ceramic Materials
Authors: Rozzi Jay C. , Incropera Frank P. , Shin Yung C. 
Published: March 2022

Abstract
A three-dimensional, unsteady heat transfer model has been formulated for predicting the temperature field associated with the laser assisted machining (LAM) of ceramic materials. The model considers a rotating silicon nitride workpiece heated by a translating CO2 laser, with material removal occurring at a location corresponding to the cutting tool. Movement of the workpiece relative to the laser source and cutting tool at the conclusion of a preheat phase significantly influences the workpiece temperature distribution, particularly at the material removal plane, by facilitating the transport of thermal energy deposited by the laser to the chamfer (the boundary between removed and unremoved material). Relative to predictions without material removal, the chamfer represents a significant thermal resistance to heat transfer, thereby increasing temperatures in the material removal plane at the conclusion of the preheat phase and causing a slower decay in the average temperature in this region as machining continues. The temperature distribution within the machined material remains nearly uniform for the investigated operating condition.
Analysis of Mixed Convective Cross Flow Near Protruding Heat Sources on a Vertical Circuit Board
Authors: Raghavan Jagannath , Rahman Muhammad M. 
Published: March 2022

Abstract
The effects of cross flow mixed convection on discrete mounted heat sources on a circuit board of finite thickness has been analyzed in this study. In this type of flow, the orthogonal free and forced convection result in a three dimensional boundary layer flow. A numerical model is developed to simulate the actual device considering heat generation in the integrated circuit components, conduction of heat through the board and heater modules, and convection of heat from the board and module surfaces to the fluid stream. The significance of the factors that affect heat transfer rate and surface temperatures of these components were analyzed. The equations for the conservation of mass, momentum, and energy were solved in their non-dimensional form to study the velocity and temperature profiles. The numerical model identified important dimensionless parameters such as Richardson number, Prandtl number, source spacing, distance from leading edges, and the ratio of solid-to-fluid thermal conductivities. A parametric study revealed their influences.
Effect of Coal Particle Size on Coal-Water Slurry (CWS) Atomization
Authors: Son S. Y. , Kihm K. D. 
Published: March 2022

Abstract
The effect of coal particle size on coal-water slurry (CWS) atomization is examined by comparing classified CWS sprays containing coal particles in different size ranges. The sprays are generated by injecting a CWS mixture into a sonic air jet and the Malvern sizing system nonintrusively measures spray Sauter mean diameters (SMD). The results consistently show that the spray SMDs of the CWS containing smaller coal particles are larger than the spray SMDs of the CWS containing larger coal particles. The internal capillary holding force between the particles and water increases with decreasing particle sizes because of their smaller radii of curvature. This increased holding force strongly resists against the external airblast and makes the atomization difficult. On the other hand, the relatively small capillary holding force of the CWS containing larger coal particles carries weaker resistance to the external airblast, and smaller spray SMDs result.
Radiative Calibration of Heat Flux Sensors at NIST: An Overview
Authors: Murthy Annageri V. , Tsai Benjamin K. , Saunders Robert D. 
Published: March 2022

Abstract
This paper describes the current capabilities and future plans at the National Institute of Standards and Technology (NIST) for radiative calibration of heat flux sensors. Experimental methods using an existing blackbody and high power lasers have been developed to characterize a reference electrical substitution radiometer and heat flux sensors, respectively. Tests carried out on a typical Schmidt-Boelter heat flux sensor showed long term repeatability of calibration within ± 0.4 %. Factors, such as purge gas flow, affecting sensor calibration when using high temperature blackbodies are discussed. To enhance the present capabilities, two additional blackbody setups are planned. These are a high temperature blackbody operating up to 3200 K with the possibility of calibrating sensors at power levels up to 200 kW/m2, and a spherical blackbody with a water-cooled aperture to calibrate sensors in a low convection environment.
A Comparison Between Colocated Mesh and Staggered Mesh Solutions for the Steady State Simple Driven Cavity Problem
Authors: Batteh John J. , Chen Michael M. 
Published: March 2022

Abstract
This paper presents some sample computations that employ three different schemes for the discretization of the incompressible Navier-Stokes equations: colocated mesh (CM) with basic second order finite difference approximations for the interior nodes, with two different implementations of the pressure boundary condition, and the conventional staggered mesh (SM). The specific goal is to better appreciate the well known spatial oscillation, or “pressure wiggle”, phenomenon usually attributed to the use of colocated mesh. A modified artificial compressibility method (ACM) and the MAC method were used for the colocated and staggered mesh calculations, respectively, but the focus of our findings is on the converged steady state results which pertain more to the asymptotic steady state discretization scheme (i.e. SM or CM) than the pseudo-time iteration method for obtaining these asymptotic solutions. Two different implementations of the pressure boundary condition were employed in conjunction with the ACM: 1) the requirement that the boundary pressure acts so that the continuity equation is satisfied at the boundary or 2) the requirement that the normal pressure gradient on the boundary satisfies the Navier-Stokes equation. Sample 2D and 3D calculations are performed on the driven cavity problem using these three techniques for a Reynolds number of 100. The results of these sample calculations are analyzed based on solutions available in the literature, and a comparison is made between the various methods and boundary condition implementations. The colocated mesh results indicate that the spatial oscillations, when present, were never greater than the overall accuracy, which is judged to be consistent with expected truncation errors of the various methods. The major objections of the oscillations are thus cosmetic rather than substantive. Furthermore, when the normal pressure gradient condition from the Navier-Stokes equation is used in conjunction with a colocated mesh, the spatial oscillations in the computations are significantly reduced for the pressure and are essentially non-existent for the velocities. These results suggest that the colocated mesh, with artificial compressibility or with other methods of computation, is a viable discretization scheme without the use of complex interpolation schemes to simulate a staggered mesh.
Design, Fabrication and Static Test of a Resonant Microaccelerometer
Authors: Kim Si Young , Go Jeung Sang , Cho Young-Ho 
Published: March 2022

Abstract
This paper investigates a resonant microaccelerometer that measures acceleration using a built-in micromechanical resonator, whose resonant frequency is changing due to an acceleration-induced axial force. From a structural analysis, design equations for the resonant microaccelerometer have been developed and have included analytic formulae for the resonant frequency, sensitivity, nonlinearity and maximum stress in the mechanical structures. On this basis, the sizes of the accelerometer are designed for a sensitivity of 10−3g/Hz over the bandwidth of 100Hz, while satisfying the maximum nonlinearity of 5%, the minimum shock endurance of 100g, the detection range of 5g and the size constraints placed by microfabrication process. A set of the resonant accelerometers has been fabricated by an integrated use of bulk-micromachining and surface-micromachining techniques. From on-chip test structures, the Young’s modulus of polysilicon is measured in the range of 60∼100GPa. The residual stress of polysilicon structures was reduced to 362.1kPa by the annealing process performed for 2 hours at 1000 C in N2 atmosphere. From a static test of the resonant accelerometer, a frequency shift of 860Hz has been measured corresponding to the deflection of the proof-mass by 4.3±0.5μm; thereby obtaining the detection sensitivity of 0.92±0.11 × 10−3g/Hz. Uncertainty in the resonant frequency output has been evaluated to identify important issues involved in the design, fabrication and testing of the resonant accelerometer.
Optimization of the Silicon/PZT Longitudinal Mode Resonant Transducer
Authors: Lai Amit , White Richard M. 
Published: March 2022

Abstract
An analytical electromechanical model of a silicon/PZT laminate longitudinal mode resonant transducer is presented. The validity of this model is shown by the excellent agreement between the predicted and measured impedance of transducers with different device parameters. The experimental data also show a maximum value of 34 for the product of the quality factor and the effective electromechanical coupling. This figure of merit product, an indication of the power output capacity of a transducer, is two to three times higher than that of metal-based transducers. Additionally, silicon can sustain eight times higher ultrasonic velocities than high-strength titanium alloys, indicating that silicon-based ultrasonic transducers can produce much higher intensities efficiently.
Micromachined RF Signal Switching Devices on High Resistivity Silicon Substrates
Authors: Yao Zhimin J. , Goldsmith Chuck , Eshelman Susan , Denniston David 
Published: March 2022

Abstract
The development of a micromechanical capacitive microwave switching device is described in this paper. The switching element consists of a thin metallic membrane. Micromechanical membrane switches have several advantages compared to FET or p-i-n diode switches, such as: low loss, low cost, and low DC power requirements. Compared with the cantilever type of mechanical switches, metal membrane switches have faster switching speeds, lower switching voltages and less stiction problems. This paper presents the design, fabrication and test results of membrane switches. Some important process related issues are discussed.
Theoretical Determination of the Laser Induced Damage Threshold for Ultrashort Pulse Laser Heating of Metal Films
Authors: Smith Andrew N. , Norris Pamela M. , Lee Anthony S. 
Published: March 2022

Abstract
Non-equilibrium heating between electrons and the crystalline lattice has been observed in numerous ultrashort pulsed laser applications yielding unexpected temperature profiles. Typically, laser induced damage threshold (LIDT) values for thin metal films are predicted using the melting temperature and the standard heat diffusion equation. A method is presented which accounts for non-equilibrium heating by solving the Parabolic Two Step (PTS) heat conduction model and deriving an analytical expression for the laser power that causes the film temperature to exceed a critical value. This critical temperature is a design parameter dependent on the material properties of the film and often the repetition rate of the source. In non-equilibrium heating, the predicted peak lattice temperature is significantly lower and occurs at some time after the deposition of energy, which can be orders of magnitude greater than the pulse duration. This minimizes the effect of the temporal shape of the pulse and allows for an analytical solution. This solution and an equation which can be used to calculate the thermal damage threshold value for non-equilibrium laser heating are presented.