bluuebunny/crossref_metadata_2025 huggingface dataset:
Coalescence of Dual Bubbles on Micro Heaters
Authors: Chen Tailian , Chung J. N.
Published: November 2021

This experiment is based on a heating surface consisting of micro heaters where the temperature of each heater can be individually controlled by an electronic feedback loop similar to those used in hotwire anemometry. The power consumed by the heaters throughout the cycle of individual bubble growth, coalescence and departure was measured at high frequencies, thus the heat flux and its variation were obtained. At the same time, visualization of bubbles’ behaviour by a fast CCD camera has been performed to gather more information. By combining the heat flux data closely with the visualization result, we have found that the single bubble’ heat flux variation correlates with the separate stages of its life cycle: nucleation, growth, detachment and departure. By careful timing and control of two individual heaters, we were able to grow two individual bubbles side-by-side. The coalescence of these two bubbles would take place when they grow to a certain size that allows them to touch each other. We have recorded two major heat flux spikes for a typical cycle. The first one corresponds to the nucleation of bubbles, the second one is for the coalescence of the two bubbles. We found that the heat flux variation is closely related to the bubble dynamics and bubble-bubble interaction.
Design of Liquid Cooled Coldplate for the Inverter of the Hybrid Electric Vehicle
Authors: Jih C. Edward , Chen K. , Abraham T. , Siddapureddy V. , Poulson R. , Sankaran V. A.
Published: November 2021

As the performance of the advanced electric systems increases, the packaging densities and power requirements will also increase. The reliability of these components will depend on the ability of the packaging system to transport heat away from the device. In this paper, a liquid-cooled coldplate for the inverter of hybrid electric vehicle was designed by using Computational Fluid Dynamics (CFD) technique. The main features of inverter packaging include power module, capacitors, busbar, gate driver, gate power supply, coldplate, sensors, & controllers. How to effectively dissipate the heat from power module to the coldplate is the focus of this study. The 3-phase full bridge power module consists of 12 IGBTs and 12 diodes. The silicon dies of IGBT or diode were soldered to the direct-bonded ceramic (DBC) A1N substrate, and to the copper base plate. Then the whole module was mounted mechanically onto an aluminum coldplate using thermal grease at the interface. The maximum allowable die junction temperature is 125°C. The commercial CFD code, FLUENT, was used here to study the flow field and heat transfer of the coldplate. In order to have confidence in the CFD prediction, the temperature distribution of an inverter assembly was obtained from FLUENT and then verified with the measurement from an infrared camera. Several design options on the coldplate, i.e., diameter & height of fins and shape & pattern of fin arrays, were examined. The effects of coolant flow rate and coolant type on the performance of coldplate were also studied. The overall thermal resistance and pressure drop of the coldplate were used to compare the efficiency of a series of coldplate design. Based on the CFD results, the effect of coldplate pin fins design on the thermal resistance is small. However, the pressure drop of the coldplate is quite sensitive to the design of pin fins. It is also noted that the fin height of coldplate can be reduced by 10% without degrading the performance of coldplate.
Aggregate Intensification of Natural Convection Between Air and a Vertical Parallel-Plate Channel by Inserting an Auxiliary Plate at the Mouth and Appending Colinear Insulated Plates at the Exit
Authors: Andreozzi Assunta , Manca Oronzio , Campo Antonio
Published: November 2021

This paper addresses the examination of heat transfer in parallel-plate channels using a combination of two passive schemes: (1) the insertion of an auxiliary plate at the mouth and (2) the appendage of colinear insulated plates at the exit. The investigation is made by numerically solving the full elliptic Navier-Stokes and energy equation in a I-type computational domain. The channel is symmetrically heated by uniform heat flux. The working fluid is air. The results are reported in terms of induced mass flow rate and maximum wall temperatures. Further, the local Nusselt number, the mean Nusselt number and pressure profiles are presented. The analyzed Grashof numbers based on the heated plate height are 103 and 106.
Ceramic Miniature Heat Pipes and Liquid Charging Methods
Authors: Gao Mingcong , Cao Yiding , Jones W. Kinzy , Zampino Marc A.
Published: November 2021

Three working-liquid charging methods for miniature heat pipes are introduced, and their advantages and disadvantages are described. Using these methods, two types of ceramic heat pipes were charged and tested. The ceramic heat pipes were made of alumina and have overall dimensions of 89 mm × 12 mm × 2.9 mm and a designed vapor space of 82.5 mm × 4.1 mm × 1.27 mm. Axial micro capillary grooves were provided on the top and bottom or sidewalk inside the heat pipes as wick structures. Water was used as working liquid. More than 20 Watts of heat input was achieved on a 5 mm × 5 mm heating surface. The corresponding heat flux was 80 W/cm2.
Active Thermal Control of an Ion-Drag Pump Assisted Micro Heat Pipe
Authors: Yu Zhiquan , Pohlman Nicholas A. , Hallinan Kevin P. , Kashani Reza
Published: November 2021

An ion-drag pump is utilized to enhance the heat transport capacity of micro heat pipes. An analytical model is developed to estimate the maximum heat transport capacity as a function of the applied electric field. The model predicts that the application of an electric field causes a four fold increase in heat transport capacity. A transient analytical model was developed to permit variation of the electric field with applied thermal load. A proportional-integral-derivative controller was used to simulate active temperature control. The feasibility of achieving active temperature control was demonstrated experimentally.
Investigation of a Stiff-Integrator Scheme for High-Speed Reacting Flows
Authors: Woolley Lance D. , Schwer Douglas A. , Daines Russell L.
Published: November 2021

Improvements in the modeling of high-speed reacting propulsion flowfields are sought through the coupling of a stiff integrator to determine chemical reaction rates with a multidimensional CFD code. Detailed chemical kinetics models usually have significantly shorter reaction time scales than the fluid time scales, resulting in stiff governing equations and robustness issues. The present work investigates the application of a stiff ordinary differential equation solver, coupled to a diagonalized alternating-direction implicit scheme to decouple the governing time scales. This coupled ODE-ADI split-operator technique is applied to two high-speed reacting flows using hydrogen/air chemistry. The results from the stiff integrator method are compared to the traditional coupled approach utilizing 8- and 18-step kinetics models. Time-step choice, robustness, and comparison of results between the different solution methods are discussed, along with CPU times.
Modeling a Catalytic Combustor for a Steam Reformer in a Methanol Fuel Cell Vehicle
Authors: Sundaresan Meena , Ramaswamy Sitaram , Moore Robert M.
Published: November 2021

Using a fuel other than pure hydrogen in a fuel cell vehicle (FCV) employing a Proton Exchange Membrane (PEM) fuel cell stack typically requires an on-board fuel processor to provide hydrogen-rich fuel to the stack. In the case of methanol as the source fuel, the reformation process typically occurs in a fuel processor that combines a steam reformer plus a catalytic burner (to provide the necessary energy for the endothermic steam reforming reactions to occur). This paper will discuss a model for the catalytic burner in a methanol fuel processor for an Indirect Methanol FCV. The model uses MATLAB/Simulink software and the simulation provides results for both energy efficiency and pollutant formation.
Improving the Performance of a Vibration Neutraliser by Controlling Its Stiffness and Damping
Authors: Brennan M. J. , Kidner M. R. F.
Published: November 2021

This paper is concerned with improving the performance of a vibration neutraliser (absorber) by making it adaptive. To achieve this, the stiffness and damping of the device has to be controlled so that the impedance of the neutraliser is optimised at its operational frequency. The results of an experimental study are presented where real-time control of such a device is demonstrated. The stiffness is adjusted by changing the geometry, and damping is controlled with a velocity feedback system. Both these actions are achieved using a fuzzy logic controller.
Ultra-Pure Viscoelastic Damping Polymers and Associated Low Outgassing Materials
Authors: McCutcheon Jeff W.
Published: November 2021

The key to successful multifunctional materials applications for vibration, shock and acoustic control is often the proper selection of materials, geometric design and optimum application. Much work has been done in the areas of geometric designs and optimum application of the multi-functional materials. The next step is improvements in the passive damping materials themselves.

The improvement in the passive materials in the past has often focused on the areas of improved damping performance (loss factor, storage modulus), material performance (acrylics, silicones, etc.) and enhanced features (thermally conductive, electrically conductive, etc). One of the newest requirements for passive damping polymers is in the area of ultra-pure viscoelastic damping polymers. This new generation of materials is finding growing use because the sensitive environment where the passive material is used require a material that will not negatively impact the components in that environment. This new generation of passive materials needs to be ultra-pure with respect to organic material outgassing, anions, catalysts and siloxanes.

In addition to the viscoelastic damping polymer requirements for high purity, the associated polymeric materials (epoxies, laminating adhesives and tapes) used in the same environment must also be of a similar low outgassing, ultra-pure, ultra-clean, electronics grade or clean room performance designation. If this is not done, the environment could become contaminated and negate a portion of the benefit of using the clean damping material. This also requires an understanding of the test method used to determine each product’s cleanliness performance, as all test methods are not equal and can give significantly different test results. An example is comparing a polymer sample tested for organic outgassing and using a static headspace gas chromatography/mass spectroscopy (GC/MS) and a dynamic headspace GC/MS.
A Study on Diesel Fuel Drop Size Distribution
Authors: Jawad Badih A.
Published: November 2021

A pulsed Malvern drop-size analyzer, based on Fraunhofer diffraction, was utilized to determmine droplet size size ranges of diesel fuels under different conditions of injection. the effects of fuel properties, design and operating parameters on the formation of diesal spray are discussed. In these studies, the spray is formed by injecting a calibrated amount of fuel into air with the frequency of the intermittent behavior controlled by the speed of the fuel pump. In this study, an injection cycle was tailored so that it was divided into several increments which were injected sequentially. A two mm diammeter collimated beam illuminated a cylindrical volume perpendicular to the axis of the fuel spray, and its attenuation was recorded and stored on the oscilloscope. With the optical measurement being synchronized to the needle lift of the injector, the output of the needle lift transducer and the optical signal was recorded simultaneously. Thus, the arrival and the duration of the spray at various positions along its axis were measured.

The droplet size distributions were obtained directly as penetration measurements were made. However, by applying a delay time through the synchronization feature of the sizer, information about droplet size evolution within the same spray was possible. Distribution widths are plotted as a function of time for different chamber pressures, injection pressures, different positions, and different fuels. Coagulation seems to be a dominant phenomenon in these studies.
CFD Modeling of a Fiberglass Furnace
Authors: Jian Christopher Q.
Published: November 2021

In the fiberglass production process, glass is produced from various batch ingredients in a glass furnace. The molten glass is then delivered, through a delivery system that is often called the front-end system, to the various downstream forming operations. Multiple complex processes take place in the glass furnace, which include the turbulent reacting flow in the combustion space; laminar flow dominated by natural convection in the molten glass; fusion of raw batch materials to form molten glass; radiation and convective heat transfer between the combustion space and the molten glass; bubbling flows in the glass; and Joule heating within the molten glass, etc. The main task of the glass furnace is to convert raw batch materials into glass and thermally and chemically condition the glass before being delivered to the front-end system. One of the major tasks of a front-end system is to insure that the glass is conditioned to the specifications required by the forming operations while maintaining the highest glass quality. Improperly designed and/or operated furnace and front end delivery system can cause a number of problems to the forming operations, ranging from poor glass quality with defects to shortened furnace service life. CFD has become an increasingly important tool for glass manufacturers to guide and optimize such system designs and operations. The current work is part of an effort to leverage CFD resources in the decision-making processes in engineering, operations, and businesses. The furnace modeling was performed using the recently implemented batch melting model jointly developed by Owens Corning and Fluent, Inc., which features three-dimensional simulation of an entire glass furnace including combustion, bubbling, and electrical boosting. The thermal coupling procedure between the combustion space, batch, and the melting tank along with the associated convergence issues are discussed. The modeling results are presented along with comparison with field measurements.
Assessment and Performance Analysis of Centrifugal Compressors
Authors: Whitfield A. , Johnson M. A. , Dosanjh M.
Published: November 2021

A centrifugal compressor performance analysis and assessment procedure is described which is based on the measurement of the basic performance characteristics of the compressor only. It is shown that a useful assessment of the compressor performance can be carried out within the uncertainty bounds of a one-dimensional analysis common to a more detailed experimental study. The analysis procedure provides details of the impeller performance in terms of relative velocity diffusion ratio, and details of the impeller/diffuser interface in terms of the absolute flow angle, incidence angle and Mach number. If the compressor design incorporates a vaneless diffuser the flow angle at the volute inlet can be found, leading to a good assessment of the volute performance. The procedure was applied to a small turbocharger compressor with a vaneless diffuser and a number of gas pipeline compressors with vaned diffusers. The ability to derive the required aerodynamic parameters and the limitations involved are described with reference to one of the gas pipeline compressors and the turbocharger compressor.
The Influence of Inlet Flow Distortion on the Performance of a Centrifugal Compressor and the Development of Improved Inlet Using Numerical Simulations—Part II: Development of Improved Inlet for a Centrifugal Compressor Using Numerical Simulations
Authors: Kim Yunbae , Engeda Abraham , Aungier Ron , Direnzi Greg
Published: November 2021

Part I of this paper reported the experimental investigation on the effect of the curved inlet pipe flow distortion on a centrifugal compressor performance, which motivated the need of a new inlet design as well as a clear picture of the detailed flow field in the existing inlet design using numerical simulations. In Part II, new designs of different inlet systems as well as the design methods are discussed based on the comparison of flow properties at pipe exit of each design. The goal of the compressor inlet system design is to reduce the secondary flow and provide uniform flow for a compressor. Two design approaches are reported in this paper, one of which is the location of vanes and the other is the length of curvature radius, resulting in four new designs. The vanes are spaced in such a way that each passage shares the same pressure difference in radial direction. Numerical simulation results are presented in terms of mass averaged parameters and flow structures on the exit cross-sectional area. The design of original bend pipe with two vanes inside shows advantages over others.
Modeling of Disc Shaped FGM Piezoelectric Actuator
Authors: Almajid Abdulhakim , Taya Minoru
Published: November 2021

The mechanical behavior of a disk shaped piezoelectric actuator was studied using modified classical lamination theory (CLT) for circular plate. The modified CLT accounts for piezoelectric coupling terms. CLT is capable of predicting the stress field and out of plane displacement of disk shaped laminated piezoelectric layers under applied electric field. The analysis was applied to different types of piezoelectric actuators.
Magneto-Mechanical Characterization of Magnetostrictive Composites
Authors: Nersessian Nersesse , Carman Gregory P.
Published: November 2021

This paper describes magneto-mechanical test results for magnetostrictive composites. The purpose of the study is to evaluate the behavior of magnetosrictive materials under combined magnetic and mechanical loading, and to determine fundamental properties used for design of actuator and sensor systems that incorporate these materials. Currently the composites are being used in sonar transducers. The magnetosrictive composite contains Terfenol-D (Tb0.3Dy0.7Fe2) particulate embedded into an epoxy binder. Composite form is used due to the relative brittleness and limited operational frequencies of monolithic Terfenol-D. Three different tests were performed: 1) constant magnetic field with linearly varying load, 2) constant magnetic field with cyclically varying load around a bias load and 3) constant pre-load with varying magnetic field. Testing was performed on five different volume fraction composites, namely, 10%, 20%, 30%, 40% and 50%. Parameters that were evaluated include strain output, magnetic field and elastic modulus. Results for the constant magnetic field tests indicate that modulus generally increases with increasing volume fraction and increasing H/Hmax. However, for low fields, an initial dip is noticed in modulus (i.e. ΔE effect) attributed to domains becoming more mobile at lower magnetic field levels. Results for the constant load test indicate a strong dependence of strain output on applied pre-stress. Results indicate that max strain peaks at a certain value of the pre-stress and then decreases for increasing pre-stress.
Shear Load Transfer in Shape Memory Alloy Fiber Reinforced Composites During Elastic Axisymmetric Deformations
Authors: Tsai Hungyu , Fan Xinjian
Published: November 2021

The axisymmetric elastic deformations in shape memory alloy (SMA) fiber reinforced composites are studied. We analyze the stress concentration near the interface between the fiber and the matrix as a result of a pre-described phase transformation in the active fiber. A typical model involving a single infinite fiber embedded in an infinite elastic matrix is studied. A portion of the fiber is allowed to undergo phase transformation along the axial direction so that its length is changed by the corresponding transformation strain (typically a few percentages), while the matrix is assumed to be linearly elastic and isotropic. Under certain bonding conditions, the deformation of fiber forces the matrix to deform in the elastic regime in order to accommodate the transformation strains.

The problem is formulated as axisymmetric deformations coupled with a finite transformation region in the fiber. In order to avoid infinite stresses found under perfect bonding conditions, we adopt a “spring” model which accounts for the elasticity of a transition layer at the interface. This model allows for relative displacements between the fiber and the matrix. A linear relation between this relative displacement and the shear stress is used. The exact elasticity solution (in integral form) to this problem is found using Love’s stress function and Fourier transform. Numerical integration is performed to produce the stress distributions. In particular, the shear load transfer profiles along the interface are calculated for various spring stiffness. It is found that the singularity is eliminated and the stress concentration factor depends on the stiffness of the transition layer.
A 700 Hz Valve for Dispensing High Viscosity Molten Polymers Using a Piezo-Electrically Driven Star Frame Mechanical Amplifier
Authors: Hassler Bill
Published: November 2021

A valve was designed, built, and tested using a Star Frame mechanical amplifier driven by multilayered piezo-electric actuators. This valve was designed to dispense many different types of molten polymers, adhesives, and highly rilled coating materials. The valve was a simple ball and seat design with a stroke of 0.38 mm, a ball diameter of 2.4 mm, and a seating diameter of 1.5 mm. The valve was successfully tested with molten block copolymers with viscosities as high as 45,000 centipoise, at temperatures of up to 190 deg. C and at frequencies of up to 700 Hz continuous duty. The valve was also successfully tested at 1 kHz for short durations.
Forced Response and Random Vibration Analysis of Printed Circuit Boards
Authors: Tarter James F.
Published: November 2021

Finite element analysis has been used in conjunction with developed algorithms to analyze forced response and random vibration response of printed circuit boards. Analytical predictions have been compared to random vibration test data for model correlation and validation of the analysis methods. The described methods provide design data for predicting deflections and G levels as a function of frequency or predicting RMS levels for random excitation. These data are utilized for initiating design changes and guiding component placement. Deflection versus frequency contributions for random excitation are analyzed to identify critical design frequencies. Forced response contour plots include effects of modal coupling, modal participation factors, and system damping. These data provide a better description of the expected operating deflection shapes man a simple mode shape. All of these methods are used to improve design integrity and ensure specification compliance prior to hardware fabrication. The analyses utilize aggregate board properties, and do not currently provide data for individual components which are installed on the board.
Iterative Fixture Layout and Clamping Force Optimization Using the Genetic Algorithm
Authors: Kulankara Krishnakumar , Satyanarayana Srinath , Melkote Shreyes N.
Published: November 2021

Fixture design is a critical step in machining. An important aspect of fixture design is the optimization of the fixture, the primary objective being the minimization of workpiece deflection by suitably varying the layout of fixture elements and the clamping forces. Previous methods for fixture design optimization have treated fixture layout and clamping force optimization independently and/or used nonlinear programming methods that yield sub-optimal solutions. This paper deals with application of the genetic algorithm (GA) for fixture layout and clamping force optimization for a compliant workpiece. An iterative algorithm that minimizes the workpiece elastic deformation for the entire cutting process by alternatively varying the fixture layout and clamping force is proposed. It is shown via an example of milling fixture design that this algorithm yields a design that is superior to the result obtained from either fixture layout or clamping force optimization alone.
Fastener-Induced Growth and Distortion in Large Compliant Assemblies
Authors: Mahanian Saba , Mattikalli Raju , Jones Alan
Published: November 2021

A systematic approach has been developed to predict fastener-induced growth and distortion in large compliant assemblies. Analytical growth and distortion formulas are developed for beam-type structures of arbitrary cross-section and an equivalent fastener force model is developed that can be applied to more complex finite element models.
A 3D Measurement of Cutting Tool Edge Based on Focus Error
Authors: Moon K. S. , Ling Z. K.
Published: November 2021

This study describes a technique for measuring the three-dimensional (3D) shape of cutting tool edge, based on a CCD image sensor along the optical axis and on subsequently analyzing the image data. The image of a cutting edge formed by an optical system, such as a lens, contains geometric information about the shape of cutting edge. The focus errors can be deduced from the observed image. This deduction requires digital image processing. The focus error computation and a sequence of images obtained by continuously varying the distance between the lens and the image detector provides the possibility of obtaining high-resolution 3D coordinate measurement of cutting tool edge. The proposed technique is supported by experiments and further applications of the technique are indicated.
Optimum Error Separation Technique for In-Situ Straightness Measurement in Diamond Turning
Authors: Yu Jianming , Li C. James
Published: November 2021

In diamond turning, measurement of a workpiece without removing it from the machine tool needs an in-situ metrology system and an error separation technique. The traditional methods for error separation have their limitation in straightness measurement. In this paper, a thorough analysis is given for the non-periodic effect on error separation, and a new method is described to overcome the limitation in straightness measurement for short workpiece. The new method enables the use of a sampling interval smaller than the one permitted by the traditional techniques and gives more detailed information about the measured workpiece profile. Consequently, it is suitable for the in-situ measurements of short workpieces in diamond turning.
The Numerical Prediction of Grain Size During Hot Forming
Authors: Jin Quanlin
Published: November 2021

The grain size and its distribution have very important effects on mechanical behaviors of the formed parts, and the grain size evolution is controlled by multiple dynamic microstructure changes. Therefore, the numerical simulation of these microstructure changes will be significant for improving part quality. In this paper we discuss two important problems for the prediction grain size evolution. One is the constitutive relation considering the microstructure change processes, the another is the identification of the material constitutive parameters. Finally we present some numerical examples to show the influences of the process parameters on the grain size inhomogeneity and the influences of grain growth on the superplastic forming process.
Thermal Assessment and Enhancement of Molded Array (MAP) PBGA Packages for Handheld Telecommunication Applications
Authors: Adams V. H. , Chiriac V. A. , Lee T.-Y. Tom
Published: November 2021

Computational Fluid Dynamics (CFD) simulations were conducted to characterize the thermal performance of Molded Array Plastic Ball Grid Array (MAP PBGA) packages for hand-held applications. Due to size constraints, these PBGA packages tend to have fine pitch solder ball arrays and small overall size. Thermal analysis is required to assess the design risks associated with this trend toward smaller size and increasing power dissipation requirements. A conjugate heat transfer problem, in which radiative losses from the exposed surfaces of the package and the printed wiring board to the walls of the wind tunnel, was solved for horizontal natural convection cooling conditions. Thermal model assumptions and development for the MAP PBGA package are provided. The model is benchmarked with measurements obtained for a 64 I/O 0.8 mm pitch, 8 mm MAP PBGA. Predictions for junction-to-ambient thermal resistance were within 10% of measured values.

Baseline simulations were conducted for 0.8 mm pitch MAP PBGA packages with substrate/die size combinations in the range of 6 to 12 mm substrate size and 3.81 to 7.62 mm die size. Junction-to-ambient thermal resistances varied over the range of 28.8 °C/W to 62.4 °C/W. Methods to improve thermal performance of these packages were investigated. Previous work indicated that effective conduction to the substrate by heat spreaders, metallic lids, mold compound, heat sinks, and their combinations promoted thermal performance. A necessary further step is to understand how effective area for heat spreading inside the package affects its thermal behavior, while varying the die size for package configurations with and without heat spreader. Studies were conducted to evaluate thermal performance improvement through the use of a copper heat spreader on the package top surface as it is affected by die size, package size, and substrate effective thermal conductivity. Substrate effective thermal conductivity is varied through the use of two and four layer substrates with thermal vias under the die. Results show a modest 1% to 15% reduction in junction-to-ambient thermal resistance for the MAP PBGA package sizes of interest.
Selection of Industrial Coatings Based on Environmental and Societal Impact Characteristics
Authors: Gershenson J. K. , Dupont R. R. , Ratliff R. L.
Published: November 2021

Product and process engineers need tools that allow them to weigh the environmental and societal impacts versus the cost of their component and process selection decisions early in the design process when information and time are scarce. This paper is intended as a framework for future development that combines the elements of industrial ecology, product design methodology, and auditing to shed light on the selection of industrial coatings to minimize environmental and societal impact. The coating selection method described herein is based on the concept of making design decisions early in the product development process but in a state of considerable information. By using the principles of industrial ecology, it is possible to understand the elements of environmental and societal impact for industrial coatings. By incorporating the principles of auditing, or more specifically environmental auditing, it is possible to understand which of these elements may be, or must be, reliably measured and how they can be measured. Industrial ecology and environmental auditing create the state of considerable information. This information can then be meshed with design decision making, or more specifically component and process selection, to understand how to trade off these elements to select an industrial coating with the least environmental and societal impact.

The goal is a toolset to permit the incorporation of environmental and societal impact measures into design and manufacturing decisions by relating environmental and societal characteristics to key performance variables. The foundation of this work is a method for quickly comparing different industrial coating choices based on their environmental and societal impacts and their performance in a given application.
Modeling the HSK (Hollow Shank Taper 1/10 Tapered Joint) Toolholder-Spindle Interface
Authors: Hanna Ihab M. , Agapiou John S. , Stephenson David A.
Published: November 2021

The HSK toolholder-spindle connection was developed to overcome shortcomings of the 7/24 steep-taper interface, especially at higher speeds. However, the HSK system was standardized quickly, without detailed evaluation based on operational experience. Several issues concerning the reliability, maintainability, and safety of the interface have been raised within the international engineering community.

This study was undertaken to analytically investigate factors which influence the performance and limitations of the HSK toolholder system. Finite Element Models were created to analyze the effects of varying toolholder and spindle taper geometry, axial spindle taper length, drawbar/clamping load, spindle speed, applied bending load, and applied torsional load on HSK toolholders. Outputs considered include taper-to-taper contact pressures, taper-to-taper clearances, minimum drawbar forces, interface stiffnesses, and stresses in the toolholder. Static deflections at the end of the holder predicted by the models agreed well with measured values.

The results showed that the interface stiffness and load-carrying capability are significantly affected by taper mismatch and dimensional variations, and that stresses in the toolholder near the drive slots can be quite high, leading to potential fatigue issues for smaller toolholders subjected to frequent clamping-unclamping cycles (e.g., in high volume applications). The results can be used to specify minimum toolholder material properties for critical applications, as well as drawbar design and spindle/toolholder gaging guidelines to increase system reliability and maintainability.
Ultra-Violet Excimer Laser Micro-Patterning of Polymers
Authors: Kancharla Vijay V. , Chen Shaochen
Published: November 2021

Two polymer materials, PDLA and PVA, have been patterned by ultra-violet (UV) Excimer laser micromachining for biomedical applications. In this work, Parametric investigations were conducted for both PVA and PDLA polymers using a XeCl (Xenon-chloride) Excimer laser of 308 nm wavelength. Laser machined micro-patterns were examined by a high-resolution optical microscope. A surface profilometer was used to measure the actual depths of the micromachined patterns. Results show that it is much easier to pattern PVA than PDLA at 308 nm wavelength. The micro-channels show distinguished edges, indicating that thermal damage to the surrounding polymer is minimized.
A Mechanistic Force Model of the 5-Axis Milling Process
Authors: Clayton Paul A. , Elbestawi Mohamed A. , El-Wardany Tahany , Viens Dan
Published: November 2021

This paper presents a five-axis milling force model that can incorporate a variety of cutters and workpiece materials. The mechanistic model uses a discretized cutting edge to calculate an area of intersection which is multiplied by the specific cutting pressure to produce a force output along the primary cartesian coordinate system. By using an analytic description of the cutting edge with a non-specific cutter and workpiece intersection routine, a model was created that can describe a variety of cutting situations. Furthermore, a back propagation neural network is used to calibrate the model, providing robustness and scalability to the calibration process. Testing was performed on 1020 steel using various cutting parameters with a high speed steel two flute cutter and a tungsten carbide insert cutter. Furthermore, both linear cuts and a test die surface yielded good agreement between predicted and measured results.
Performance Modeling and Optimization of Composite Manufacturing Processes
Authors: Zhang Chuck , Jiang Shunliang , Wang Ben
Published: November 2021

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

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

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

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

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

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

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

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

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

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.