bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance Modeling and Optimization of Composite Manufacturing Processes
Authors: Zhang Chuck , Jiang Shunliang , Wang Ben 
Published: November 2021

Abstract
Resin transfer molding (RTM) is a promising manufacturing process for high performance composite materials. However, the fact that RTM process design has traditionally been an expensive, time-consuming trial-and-error procedure has prohibited its wide application base. This paper proposes a solution to that problem — a simulation-based process performance assessment and optimum process design scheme for RTM. This scheme enables engineers to determine the optimum locations of injection gates and vents so that both process efficiency and high part quality can be ensured.
Essential to this optimum process design scheme is a process performance index, which is defined with respect to the major factors influencing RTM process efficiency and part quality. This index is then used as the objective function of the RTM process design optimization model. Gate and vent locations are the process design parameters to be optimized. All data is obtained by running an RTM simulation program, and the genetic algorithm (GA) is employed to carry out the optimization procedure for the design parameters. It is found that constant pressure optimization will yield a process with a short flow path, whereas constant flow optimization will yield a process with smooth and vent-oriented flow pattern. Although there is no void factor in the objective function, it is interesting to note that both constant pressure and constant flow optimization procedures result in process designs with a minimum probability of void formation. This study finds that, in general, constant flow optimization should be employed if injection pressure is not a major concern; otherwise, constant pressure optimization should be used. Two case studies are presented to illustrate the efficacy of this approach.
Tissue-Level Structural Constitutive Models
Authors: Sacks Michael S. 
Published: November 2021

Abstract
A fundamental goal in constitutive modeling is the ability to predict the mechanical behavior of a material under a generalized loading state. To achieve this goal, rigorous experimentation involving all relevant deformations is necessary to obtain both the form and material constants of a strain-energy density function. For both natural biological tissues and tissue-derived soft biomaterials, there exist many physiological, surgical, and medical device applications where rigorous constitutive models are required. Although able to fit the biaxial data well, phenomenological models cannot be used to determine the underlying mechanisms of tissue mechanical behavior. In particular, the respective roles of the fibers and the matrix and how these may change with growth or chemical treatments are unknown. Structurally based constitutive models avoid ambiguities in material characterization and offer insights into the function, structure, and mechanics of tissue components. In the present work a structural constitutive model for the aortic valve is presented as an example of a structural approach. Ongoing issues in practically applying structural models to other tissues are also addressed.
Measurements of Decomposed EPS Gases Pressure and Molten Metal-Polymeric Foam Interface Velocity During Lost Foam Casting Process: Part 2—Rectangular Bars Casting
Authors: Bakhtiyarov Sayavur I. , Overfelt Ruel A. 
Published: November 2021

Abstract
The behavior of liquid metal flow and gas pressure of the evaporated styrofoam pattern decomposition by-products inside the mold and surrounding sand for ductile iron was investigated experimentally. A computer aided thermometric and pressure measurement technique was built to study the heat and pressure related processes in the lost foam casting. A complete pattern of temperature/pressure fluctuations is obtained during the rectangular bar casting. A relationship between liquid metal front velocity, mold filling rate, decomposed EPS gases pressure, distance from the gating and mass of decomposed EPS is found.
Stokes Flow, Reynolds Flow, Molecular Flow: Restrictions on Modeling Thin Films
Authors: Szeri Andras Z. 
Published: November 2021

Abstract
Under ordinary conditions fluids are modeled as continua and the Navier -Stokes equation and the equation of continuity can be employed to study their motion. However, to find solutions to these equations is far from elementary, and in applications we look for ways to simplify them. Such simplification is made particularly easy for thin films. We make use of thin film geometry to derive the Reynolds theory of lubrication. The Reynolds equation is employed extensively in various technical fields; it breaks down, however, when there are sudden changes in film thickness or when the film is too thin for the continuum model to apply.
In case of a sudden change of film thickness, the essentially two-dimensional flow approximation inherent in the Reynolds theory is no longer valid and the Stokes equation must be employed. If the film is made progressively thinner, the continuum assumption becomes less accurate, eventually losing its validity. For gas flows the non-dimensional group that characterizes deviation from continuum flow is the Knudsen number, Kn, the ratio of the length of the mean free path to the thickness of the channel. For small values of Kn continuum model with no-slip boundary conditions applies, for intermediate values the Reynolds equation may still be employed when specifying slip at the solid boundaries. For larger values of the Knudsen number molecular modeling is required. For liquids the Knudsen number is not available. Nevertheless, it has been shown that down to 10 nm in film thickness the flow is well modeled by the Reynolds equation.
Generation of Porous Microcellular 85/15 poly (DL-Lactide-co-Glycolide) Foams Using Supercritical CO2 for Biomedical Applications
Authors: Singh Lakhwant , Kumar Vipin , Ratner Buddy D. 
Published: November 2021

Abstract
Porous 85/15 poly (DL-lactide-co-glycolide) or PLGA foams were produced by the pressure quench method using supercritical CO2 as the blowing agent. The effects of saturation pressure and temperature on average cell size and relative density of the resulting foams were studied. Porous PLGA foams were generated with relative densities ranging from 0.107 to 0.232. Foams showed evidence of interconnected cells with porosities as high as 89%. The cell size ranged from 30 to 70 microns.
Production and Characterization of Nanoporous Polymer Membranes Produced by an Electrospraying Process
Authors: Gibson Phillip , Schreuder-Gibson Heidi 
Published: November 2021

Abstract
Electrospinning is a process by which high voltages are used to produce an interconnected membrane-like web of small fibers (10 to 500 nanometers in diameter). This novel fiber spinning technique provides the capacity to lace together a variety of types of polymers, fibers, and particles to produce ultrathin layers which are useful for chemical protective clothing. Of particular interest are electrospun membranes composed of elastomeric fibers, which are under development for several protective clothing applications. The various factors influencing electrospun nonwoven fibrous membrane structure and transport properties are discussed.
Performance measurements on experimental electrospun fiber mats compared favorably with transport properties of textiles and membranes currently used in protective clothing systems. It was found that electrospun layers presented minimal impedance to moisture vapor diffusion required for evaporative cooling.
There may be special considerations in the application of elastomeric membranes for protective clothing. Effects of membrane distortion upon transport behavior of the structure might be significant. Preliminary measurements have found that changes in elastomeric membrane structure under different states of biaxial strain were reflected in measurements of air flow through the membrane. Changes in membrane structure were also evident in environmental scanning electron microscope images of the pore/fiber rearrangement as the membrane was stretched.
Experimental measurements and theoretical calculations show electrospun fiber mats to be extremely efficient at trapping airborne particles. The high filtration efficiency is a direct result of the submicron-size fibers generated by the electrospinning process. Electrospun nanofiber coatings were applied directly to an open cell polyurethane foam. The air flow resistance and aerosol filtration properties correlated with the electrospun coating add-on weight. Particle penetration through the foam layer, which is normally very high, was eliminated by extremely thin layers of electrospun nanofibers sprayed on to the surface of the foam.
Electrospun fiber coatings produce an exceptionally lightweight multifunctional membrane for protective clothing applications which exhibits high breathability, elasticity, and filtration efficiency.
Pneumatic Pipe Modeling: Theory and Experimental Approach—Part I
Authors: Bideaux Eric , Scavarda Serge 
Published: November 2021

Abstract
In fluid power systems, lines or pipes can have a predominant effect on dynamics. Although many studies have been carried out on hydraulic pipe modeling, there are only a few existing approaches for such problems in pneumatics. This paper proposes a theoretical work in modeling pneumatic pipes. After presenting the state of the art situation and the nature of this problem, we propose different approaches of modeling pneumatic pipes. As the simulation of system with pipes may need an important computing time, it is crucial to use the adequate model. We use various discretization scheme based on finite differences and finite volumes. These methods allow the representation of the main phenomena which may occur in pipes as pressure drop, thermal exchange, compressibility, conduction and convection effects. A robust and simplified model is finally proposed. The models are simulated and the conclusion about the obtained result is presented with future prospects. In order to validate our propositions, we compare experimental trails to the results given by the simulation in a second paper: Pneumatic Pipe Modeling: Theory and Experimental Approach (PART II).
On the Motion of Granular Materials Due to Shear
Authors: Massoudi Mehrdad , Phuoc Tran X. 
Published: November 2021

Abstract
In this paper we study the flow of granular materials between two horisontal flat plates where the top plate is moving with a constant speed. The constitutive relation used for the stress is based on the continuum model proposed by Rajagopal and Massoudi (1990), where the material parameters are derived using the kinetic theory model proposed by Boyle and Massoudi (1990). The governing equations are non-dimensionalized and the resulting system of non-linear differential equations is solved numerically using finite difference technique.
Scission and Cross-Linking in an Elastomeric Cylinder Undergoing Circular Shear and Heat Conduction
Authors: Wineman Alan , Min Je-hong 
Published: November 2021

Abstract
When an elastomeric material is at a sufficiently high temperature, there can be time dependent scission of macromolecular network cross links. The affected molecules can relax and re- cross link to form a new network with a new reference configuration. This microstructural change can soften the mechanical response and there can be permanent set. A constitutive equation is proposed, based on experimental work of Tobolsky (1960), which can account for the influence of this temperature dependent microstructural change on the mechanical response. It is used to study an elastomeric cylinder undergoing circular shear and transient heat conduction.
Thermal Effects on the Natural Frequency of Rotating Disks Experiencing Large Deflection
Authors: Luo Albert C. J. , Saniei Nader 
Published: November 2021

Abstract
Thermal effects on the natural frequency for the nonlinear free vibration of rotating disks are investigated for non-uniform temperature distributions relative to the laminar and turbulent airflow induced by disk rotation. The natural frequencies for symmetric and asymmetric responses of a 3.5 inch diameter computer memory disk are calculated. When the disk is heated, its stiffness becomes larger for the two lowest nodal diameter numbers and smaller for the other nodal diameter numbers. It implies that the vibration of heated, rotating disks for the higher nodal diameter numbers may be induced more easily than the cooled one.
A Multi-Scale Model for Cell Adhesion and Deformation
Authors: N’dri Narcisse , Shyy Wei , Tran-Son-Tay Roger , Udaykumar H. S. 
Published: November 2021

Abstract
A multi-scale computational approach for studying the adhesion kinetics and deformation of a cell on a substrate is presented. This method breaks the computational work into two separate but interrelated domains. At the cellular level, a continuum model satisfying the field equations for momentum transfer and mass continuity is adopted. At the receptor-ligand or molecular level, the bond force is mechanically represented by a spring, and the formation and dissociation of bonds are characterized by a reversible two-body kinetic model. The model demonstrates that as the reverse reaction rate increases, the receptor-ligand bonds break faster, and the opposite is observed when the forward reaction rate increases. As expected, the cell peeling time increases as the number of ligands increases until it equals the number of receptors. The peeling time becomes shorter when the spring constant or slippage constant is larger. Furthermore, as the cell velocity increases during the peeling process, the maximum bond length increases while the total peeling time decreases. Based on the information from the two modeling levels, dynamics of membrane movement can be computed, illustrating that the cell mechanical properties and surrounding fluid dynamics affect the receptor-ligand kinetics, and that these effects need to be included in any realistic cell-surface interaction models.
The Effect of an External Magnetic Field on the Impurity Distribution in an RF-FZ Silicon Crystal During the Growth Process
Authors: Munakata Tetsuo , Someya Satoshi , Tanasawa Ichiro 
Published: November 2021

Abstract
The impurity concentration distribution in a silicon crystal during the floating zone (FZ) growth process under radio-frequency (RF) heating and the effect of an externally applied magnetic field on the impurity distribution in the crystal have been investigated numerically. The main purpose of the study is to clarify the characteristics of the impurity distribution in the silicon crystal under the RF-FZ crystal growth process, and the effect of an externally applied magnetic field on such an impurity distribution. The numerically obtained characteristics on impurity distribution in the crystal are as follows. In the case of excluding the external magnetic field, impurity concentration in the crystal varies due to the fluctuation of the melt flow. If we apply an external magnetic field, such impurity variation in the crystal disappears due to the stabilizing effect of the external magnetic field. Further, the crystal growth rate is decreased, the impurity concentration in the crystal is also decreased. The impurity segregation coefficient does not affect the impurity distribution in the crystal.
New Steam Turbine Test Vehicle for the Verification of Improved Efficiency Power Generation Steam Turbines
Authors: Willey Lawrence D. , Maughan James R. , Hill J. Michael , Walsh Dennis J. 
Published: November 2021

Abstract
The worldwide demand for electricity is continually increasing. Deregulation in the power generation business is driving rapid changes in the global energy market. This results in higher premiums on steam turbine efficiency and opportunities to structure several new Steam Turbine products to meet these challenging requirements. The “Dense Pack” high pressure section replacement and offering is one of the newest advanced designs to address these needs by delivering more power for the least amount of fuel. The intense competition to serve the electric power utility industry combined with the drive for new product introductions to be of the highest development life-cycle quality demands that verification of performance benefits be established very early in the new product development process.
To answer this and establish pre-field installation credibility with customers, a new multi-stage Steam Turbine Test Vehicle (STTV) has been designed and constructed. The turbine faithfully models a typical, 4-admission, large utility steam turbine and preserves geometric and flow similarity while operating at reduced pressure. The basic train is comprised of a nominal 3.5 MW (4700 hp) test turbine, a 5:1 speed reducing load gear, and two tandem 3.0 MW (4000 hp) dynamometers. The thermodynamic cycle is straight through superheated steam entering the turbine through a turbine bowl pressure regulator control valve and exhausted to the atmosphere via a back pressure control valve and roof-mounted silencer. A rigorous Design for Six Sigma (DFSS) process was used to establish the test turbine facility and to ensure all of the new product program objectives were met.
A detailed description of the facility is given with discussion of the major sub-systems, prototypical model hardware, unique steampath instrumentation, and the test procedures used to ensure accurate, repeatable data. The timeline for accomplishing the design, construction, and early testing is chronicled. Key test results are summarized including baseline testing to validate the new test facility, testing of the “Dense Pack” aerodynamic design methodology for power generation steam turbines, and the performance evaluation of developments such as new shaft, advanced aerodynamics and bucket tip seals.
In addition to developing the new design technologies and verifying their predicted efficiency increases, the Steam Turbine Test Vehicle is key for conducting Form-Fit-Function studies. Model hardware built using the standard manufacturing methods and materials intended for production parts provides invaluable insight ahead of finalizing production specifications. New features such as advanced seals and Integral Cover Buckets (ICB) benefit from being more thoroughly understood in terms of assembly and procedures ahead of new product production.
Self-Excited Oscillation of a Collapsible Tube
Authors: Wang J. W. , Low H. T. , Chew Y. T. 
Published: November 2021

Abstract
This paper considers the effect of flow-system parameters on collapsible tube flow during low-frequency oscillation; of particular interest are the reservoir head and flow resistance at the upstream and downstream, and the fluid inertia at the downstream. Experimental measurements were obtained, under zero upstream transmural pressure, for the pressure and flowrate in terms of their mean values and waveforms; also presented were the instantaneous tube shapes during an oscillation cycle. It was found that the upstream reservoir head and flow resistance determine the mean flowrate but do not affect the pressure and flow waveforms. Different waveforms were obtained even when the downstream reservoir head and flow resistance were arranged to achieve identical mean condition of pressure and flowrate. An increase in the downstream flow resistance or fluid inertia has the effect of reducing the amplitude and frequency of oscillation.
Flow Characteristics of Pulsating Flow Obstructed by an Array of Square Rods
Authors: Murata Hiroyuki , Sawada Ken-ichi , Kobayashi Michiyuki 
Published: November 2021

Abstract
A series of flow visualization experiments of pulsating flow obstructed by an array of square rods was carried out to investigate its characteristics. When the pulsation is absent, Karman vortices shed periodically from each rod. When the pulsation period is relatively long compared with the shedding period and its amplitude is large, the flow is stabilized during the accelerating phase and, during the decelarating phase, the flow is destabilized and Karman vortices break down. When the pulsation period is shorter than shedding period and its amplitude is large, the flow pulsation controls the generation and breakdown of the Karman vortices. A numerical simulation code was developed and compared with the experimental results. When the pressure gradient parameter of the code is changed sinusoidally with time, computed results become the pulsating flow. Time variations of the streamwise pressure gradient and cross-sectional averaged velocity show similarity between the experimental and computed results.
Evaluating and Improving Locomotive Crashworthiness Using LS-DYNA
Authors: Kokkins Stephen J. , Kasturi S. Kash , Kong Wayne , Punwani S. K. John 
Published: November 2021

Abstract
Representative structural models of locomotives, other rail vehicles, and other potential colliding objects were combined into moving consists which were then subjected to various collision scenarios. The LS-DYNA dynamic finite-element modeling code was utilized to realistically simulate collisions and guide understanding and improvements of the locomotive structures. This incorporated the effects of the collision interactions, plus critical non-linear material and structural behavior, buckling, fracture, kinematics, and wayside interactions of the vehicles.
The types of collisions included: locomotive-headed consists striking standing consists obliquely fouling the Right Of Way, headed both by freight cars and other locomotives; locomotives striking loose, loaded intermodal containers dislodged from opposing cars on adjacent track. Work on multiple coupled locomotive overrides in direct consist collisions is now being conducted.
The effects of varying parameters such as collision speeds, location and orientation of the colliding vehicles, and structural improvements were explored and quantified. Also, the effects of some structural design modifications such as stronger collision posts and cab structure were evaluated using this process.
Verification studies to date have shown good correlation between the analytical simulations and observed outcome of actual historical accidents.
Progress in Railway Mechanical Engineering: 1999–2000 Report of Survey Committee—Passenger and Commuter Rail Vehicles and Components
Authors: Hesser Kenneth R. 
Published: November 2021

Abstract
This annual ASME committee report covers selected worldwide developments in rail passenger and commuter vehicle equipment, components and systems. The information contained herein was obtained from responses to survey letters sent to the manufacturers of passenger rail vehicles and components, and from a review of trade and technical publications.
Prediction of Progressive Failure of Woven Composites
Authors: Whitcomb John , Tang Xiaodong 
Published: November 2021

Abstract
This paper investigates the effects of geometric non-linearity and material property degradation models on the prediction of progressive failure analyses of woven composites under tensile and compressive loads. Preliminary results presented herein suggest that the degree of difficulty of conducting progressive failure analysis is largely a function of the degree of waviness. The large waviness material exhibits complex behavior and the predictions are very sensitive to the assumed degradation model. The low waviness composite, which is more representative of most structural weaves, does not exhibit such complex behavior, at least on the global scale.