bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Finite Element Modeling of Belt-Drives Including One-Way Clutches
Authors: Leamy Michael J. , Wasfy Tamer M.
Published: November 2021

In this study, a dynamic finite element model is developed for pulley belt-drive systems, including systems incorporating oneway clutches. The belt is modeled using truss elements, while the pulleys are modeled using rotating circular constraints, for which the driver pulley’s angular velocity is prescribed. Frictional contact between the pulleys and the belt is modeled using a penalty formulation with frictional contact governed by a Coulomb-like tri-linear friction law. One-way clutch elements are modeled using a proportional torque law supporting torque transmission in a single direction. The dynamic response of the drive is then studied by incorporating the model into an explicit finite element code, which can maintain time-accuracy for large rotations and for long simulation times. The finite element solution is validated through comparison to an exact analytical solution of a steadily-rotating, two-pulley drive. Several response quantities are compared, including the normal and tangential (friction) force distributions between the pulleys and the belt, the driven pulley angular velocity, and the belt span tensions. Excellent agreement is found. Results for a second belt-drive example involving a one-way clutch demonstrates the utility and flexibility of the finite element solution approach.
Simulation of Driver Behaviour in Heterogeneous Untidy Traffic in Developing Countries
Authors: Ahuja Sonal
Published: November 2021

This paper describes the research attempt to understand driver behaviour in heterogeneous, untidy traffic in developing countries through simulation. Cities of Dhaka, Bangkok and Delhi were identified as three case study areas where traffic surveys were conducted and driver behaviour analysed.

The paper tries to quantify the level of ‘aggressiveness’ in a particular driver-vehicle environment and proposes a simulation package to understand it. A modified Tetris approach has been developed to simulate heterogeneous and untidy traffic.

The study looks into the relationship of varying driver typologies, based on age and their relative aggression levels associated with trips and vehicle typologies in the three case locations. It proposes a simulation package to generate varying driver responses in context of slow moving and untidy traffic. The study reveals that age, and driver experiences are a significant factor in determining level of driver aggression. The driver response in a particular environment is a system optimum response of his individual state, in relation to the performance of system’s ‘driver-vehicle environment’. The study concludes that while heterogeneous and mixed traffic increases vehicle delays, and stops at the signalised links, untidy traffic reduces it. The combined effect of heterogeneity and untidiness cancel each other. The simulation reveals that segregation of traffic based on vehicular typologies and speeds leads to optimisation of link performance and environment. The research proposes a simulation model that can accurately simulate mixed, slow moving, and untidy traffic condition with varying degree of driver aggression and recommends its applications.
Car Crash Zones Based on Driver’s Collision Avoidance Behavior
Authors: Shiraishi Masatake , Tsuchiya Yukiya
Published: November 2021

There will be three kinds of collision avoidance operations when a driver encounters an object just ahead: braking and stopping before collision, steering the vehicle for avoidance, and steering and braking simultaneously. In any case, a certain crash-unavoidable zone exists to each vehicle. A “cross point” determined by the vehicle behavior is a key factor in designing a crash-unavoidable zone and depends mainly on vehicle speed, friction between the wheels and the road, and the steering angle. In this paper, this zone is determined by taking these factors into account.
Control of the Vehicle’s Running Properties As a Pre-Condition for Designing Wheel Drive Systems
Authors: Vantsevich V. V. , Amani L.
Published: November 2021

The paper presents a new approach of designing optimal wheel drive systems which improve considerably vehicle properties; including traction and velocity properties, fuel consumption, turnability, and ride stability. This approach creates the basis for synthesizing optimal circumferential wheel forces needed for designing optimum wheel drive systems for a particular vehicle.

At the beginning the optimum circumferential wheel forces should first be computed. These forces correspond to the optimum values of vehicle properties’ criteria simultaneously taken in aggregate with the required vehicle kinematics.

A single criterion optimization with limitation of the rest of criteria and limitation of optimized parameters is being presented. The objective function is being built for vehicles transporting a useful load.

All these theoretical developments are followed by the results of the mathematical modeling and computer simulation of an 8WD vehicle. The modeling and simulation are based on a previously developed algorithm for the optimization of the circumferential forces among the drive wheels (see [8]).
Optimization Techniques for Hybrid Electric Vehicle Analysis Using Advisor
Authors: Markel Tony , Wipke Keith
Published: November 2021

System optimization is an extremely important step in the vehicle design process. Recently the National Renewable Energy Laboratory (NREL), both internally and through its subcontractors, has been actively developing and applying optimization tools to vehicle systems analysis problems associated with hybrid electric vehicles. We are applying both locally- and globally-focused optimization tools to these analysis problems. This paper describes the current status of the tools under development and the application of these tools to a specific problem. The optimization tools evaluated include FMINCON (gradient-based constrained optimization routine included in the MATLAB Optimization Toolbox), DIRECT (non-gradient based optimization routine), Response Surface Approximations and Direct Gradient-based Optimization (commercial routines available in VisualDOC 2.0 from Vanderplaats R&D).

The four optimization algorithms were applied to a simple two-dimensional problem so that the solution methods could be visualized and the relative performance quantified. The tools were then each applied to the optimization of a fuel cell-powered hybrid electric vehicle modeled in ADVISOR 3.1. Both the component sizes and the energy management strategy where included as design variables. The fuel economy was maximized under the constraint that vehicle performance must not be less than its conventional vehicle counterpart. Vehicle and/or component costs were not included in this study but could easily be included if suitable models were identified.

Based on this work, the following conclusions can be drawn:

• The impact of multiple local minimums and a small amount of objective function ‘noise’ (due to necessary state of charge balancing for hybrid vehicles) caused gradient based optimizers to stop before they were able to find design points as good as those found by the non-gradient based DIRECT routine.

• For the fuel cell-powered hybrid electric SUV design problem, several local optimums and one likely global optimum design have been determined. The global optimum is based on 2461 function evaluations. Based on the assumptions in this study, the optimal fuel cell-powered hybrid electric SUV would consist of a 66 kW (net) fuel cell, 107 kW and 16.8 kWh battery pack (twenty-eight 49 Ah modules, 372 volts) and a 126 kW traction motor. The optimal control for this system turned out to be mainly a series thermostat design with some power following capability under peak loads. This vehicle is expected to achieve a City/Highway composite fuel economy of 56.5 mpgge (miles per gallon gasoline equivalent).
Forced Convection Heat Transfer in the Combined Entry Region of Non-Circular Ducts
Authors: Muzychka Y. S. , Yovanovich M. M.
Published: November 2021

A new model for predicting Nusselt numbers in the combined entrance region of non-circular ducts and channels is developed. This model predicts both local and average Nusselt numbers and is valid for both isothermal and isoflux boundary conditions. The model is developed using the asymptotic results for flow past flat plates, thermally developing flows in non-circular ducts, and fully developed flow in non-circular ducts. Through the use of a novel characteristic length, the square root of cross-sectional area, the effect of duct shape on Nusselt number is minimized. Comparisons are made with several existing models for the circular tube and parallel plate channel and with numerical data for several non-circular ducts. Agreement between the proposed model and numerical data is within ± 15 percent or better for most duct shapes.
Nusselt Number in Micro and Nano Channels Under Conditions of Constant Wall Temperature
Authors: Hadjiconstantinou Nicolas G. , Simek Olga
Published: November 2021

We investigate the constant-wall-temperature convective heat-transfer characteristics of a model gaseous flow in two-dimensional micro and nano channels under hydrodynamically and thermally fully developed conditions. Our investigation covers both the slip-flow regime 0 ≤ Kn ≤ 0.1, and most of the transition regime 0.1 < Kn < 10, where Kn, the Knudsen number, is defined as the ratio between the molecular mean free path and the channel height. We use slip-flow theory in the presence of axial heat conduction to calculate the Nusselt number in the range 0 ≤ Kn ≤ 0.2, and a stochastic molecular simulation technique known as the direct simulation Monte Carlo (DSMC) to calculate the Nusselt number in the range 0.02 < Kn < 2. Inclusion of the effects of axial heat conduction in the continuum model is necessary since small-scale internal flows are typically characterized by finite Peclet numbers. Our results show that the slip-flow prediction is in good agreement with the DSMC results for Kn ≤ 0.1, but also remains a good approximation beyond its expected range of applicability. We also show that the Nusselt number decreases monotonically with increasing Knudsen number in the fully accommodating case, and that axial heat conduction increases the Nusselt number. The effect of axial heat conduction is largest at Kn = 0 and is of the order of 10%.
Parametric Study of Conjugate Heat Transfer in a Plate-Fin and Tube Heat Exchanger
Authors: Romero-Méndez Ricardo , Adame Rafael , Sen Mihir
Published: November 2021

A finite element code is used to analyze the conjugate heat transfer over the external side of a single-row plate-fin and tube heat exchanger. The conditions for which the simulations are conducted are similar to those of real plate-fin and tube heat exchangers where both conduction through the fins and convection over them are present. The influence of several parameters on the temperature distribution and local heat transfer is analyzed. From the simulations it is seen that the region of high heat transfer that appears in the leading edge of the fins is the most affected by the finite conductivity of the fin material. There is a decrease of the local heat transfer there when either the fin conductivity or the fin thickness is decreased. This is due to the decrease of the temperature gradient between the fin leading edge and the entering fluid. The effect of increasing the Reynolds number is to reduce the efficiency of the fins. This causes the local Nusselt number not to grow as fast as it would have grown if the fins had infinitely large conductivity. Finally, the effect of the eccentricity of the tube with respect to the fin length is studied. The results illustrate that by moving the tube nearer to the trailing edge of the fin, the area of low heat transfer behind the tube is reduced in size and, at the same time, the temperature gradient between the fin leading edge and the fluid above is reduced causing a reduction of the heat transfer ahead of the tube. This suggests that there is an optimum position of the tube with respect to the fin length.
Numerical Prediction of Flow and Heat Transfer in a Rectangular Channel With a Built-in Circular Tube
Authors: Basu S. , Eswaran V. , Biswas G.
Published: November 2021

Numerical investigation of flow and heat transfer in a rectangular duct with a built-in circular tube has been carried out for a Reynolds number of 1000 and blockage ratio of 0.44. Since the heat transfer in the duct is dictated by the flow structure, the present study is directed toward characterization of the flow structure. To this end, the topological theory shows the promise of becoming a powerful tool for the study of the flow structure. Computations show helical vortex tubes in the wake and existence of horseshoe vortices. The w component of velocity is surprisingly large in front and in the near wake of the tube. The limiting streamlines on the tube and the bottom-plate reveal a complex flow field. The separation lines as well as singularity (saddle and nodal) points have been investigated. The iso-Nusselt number contours and the span-averaged Nusselt number in the flow passage shed light on the heat transfer performance in the duct.
Assessment of Surface Wettability and its Relation to Boiling Phenomena
Authors: Nagai Niro , Carey Van P.
Published: November 2021

The methods for evaluating surface wettability during boiling phenomena are reviewed. Surface wettability strongly affects boiling phenomena such as boiling nucleation, bubble growth and departure, evaporation near the three phase contact line and so on. Consequently, in most regions of boiling curves other than the fully-developed film boiling regime, surface wettability has strong effects on boiling curves. In order to evaluate surface wettability, the equilibrium contact angle measured at room temperature has been commonly used. In this paper, the authors describe evidence that indicates that the equilibrium contact angle is not sufficient to estimate surface wettability as a parameter in boiling phenomena. Some other indexes of surface wettability, such as advancing and receding contact angle, dynamic contact angle, surface energy, and potential energy scale between liquid & solid molecules are reviewed and discussed.
Molecular Dynamics Simulation and Measurement of Contact Angle of Water Droplet on a Platinum Surface
Authors: Kandlikar Satish G. , Maruyama Shigeo , Steinke Mark E. , Kimura Tatsuto
Published: November 2021

A water liquid droplet in contact with a platinum surface was simulated by the molecular dynamics method. Water molecules were modeled by SPC/E and one layer of harmonic molecules represented the platinum surface with the constant temperature heat bath model using the phantom molecules. Here, the water-platinum pair potential developed by Spohr (1989) based on extended Hückel calculations was employed. In the spreading process of the liquid droplet on the platinum surface, the area of contact region between water and platinum expanded just in proportional to the one-third power of time. This spreading rate was clearly in contrast to the case of Lennard-Jones droplet.

The contact angles of water on a platinum surface under saturated conditions are measured. The measurements are made in a vacuum container using de-ionized and degassed water on a clean platinum surface. The equilibrium static, advancing and receding contact angles are measured by changing the orientation of the platinum surface. The droplets of different masses are placed on the horizontal platinum surface. The surface is the inclined to 20, 30 and 40 degrees. The advancing and receding contact angles under these conditions are measured.
Heat Transfer in a MEMS for Determination of Fluid and Flow Characteristics
Authors: Damean Nicolae , Regtien Paul P. L.
Published: November 2021

The paper presents an one-dimensional model for the heat transfer in a limited but significant zone of an actuator-sensor structure for the determination of fluid and flow characteristics. As an essential step for the designing process of this structure, the usefulness of the model in the framework of the structure’s functionality is underlined. The main heat transfer mechanisms are detailed by qualitative and quantitative evaluations. Finally we compare the data obtained by simulating this model with the experimental data. The modeling errors are discussed. The achieved results might be used directly or adapted for various thermal based sensors for flow measurement both in micro and macro world.
A Mixture Theory Model for the Flow Through an Unsaturated Wellbore
Authors: Martins-Costa Maria Laura , Gama Rogério M. Saldanha da
Published: November 2021

This work studies the dynamics of the filling up of a rigid cylindrical porous matrix by a Newtonian fluid, in order to build a preliminary local model for flows through a wellbore, using a mixture theory approach in their modeling. The mixture consists of three overlapping continuous constituents: a solid (porous medium), a liquid and an inert gas, included to account for the compressibility of the mixture as a whole. A set of two nonlinear partial differential equations describes the problem which is approximated by means of a Glimm’s scheme, combined with an operator splitting technique.
Statistics of Mathematical Two-Scale Closure of Momentum, Heat and Charge Transport Problems With Stochastic Orientation of Porous Medium Capillaries
Authors: Travkin V. S. , Hu K. , Catton I.
Published: November 2021

The history of stochastic capillary porous media transport problem treatments almost corresponds to the history of porous media transport developments. Volume Averaging Theory (VAT), shown to be an effective and rigorous approach for study of transport (laminar and turbulent) phenomena, is used to model flow and heat transfer in capillary porous media. VAT based modeling of pore level transport in stochastic capillaries results in two sets of scale governing equations. This work shows how the two scale equations could be solved and how the results could be presented using statistical analysis. We demonstrate that stochastic orientation and diameter of the pores are incorporated in the upper scale simulation procedures. We are treating this problem with conditions of Bi for each pore is in a range when Bi ≳ 0.1 which allows even greater distinction in assessing an each additional differential, integral, or integral-differential term in the VAT equations.
Three-Dimensional CFD Analysis of Gas Mixing in Large Volumes
Authors: Smith Brian L.
Published: November 2021

The paper describes three-dimensional Computational Fluid Dynamics (CFD) calculations undertaken in support of analyses of steam/air mixing which takes place in the drywell volumes of the 1/40th-scale ESBWR1 mock-up facility PANDA under conditions of symmetric steam/air injection and asymmetric outflow. Steady-state simulations for pure steam conditions illustrate how the flow streams mix to ensure balanced outflow conditions to the condensers. A transient calculation has also been performed to examine how air released from solution in the PANDA boiler would ultimately accumulate in the separate condenser units. Results provide a possible explanation for the rundown in performance of one of the condensers which was repeatedly observed in some of the PANDA tests.
Experimental and Numerical Modeling of Gaseous Carbon Dioxide Injecting Into Aqueous Water in Bottle Filler System
Authors: Zheng Y. H. , Amano R. S.
Published: November 2021

An efficient enhancement of the carbonation rate in the bottle filling stage can substantially increase the production in beverage industries. The bottle filling system currently used in most of the manufacturers can still be improved for a better performance of carbonation by designing the injection tube system. This paper reports on an experimental and numerical mass transfer modeling that can simulate the dissolution process of gaseous carbon dioxide into aqueous water in the bottle filler system. In order to establish the operating characteristics of the bottle filler system, an ordinary tap water and pure carbon dioxide were used as the liquid-gas system. The two-phase numerical modeling was developed that can serve as a framework for the continuous improvement of the design of the carbonation process in the bottle filler system. For an optimal design of CO2 injection tube and flow conditions, a computational fluid dynamics (CFD) approach is one of the most power tools. However, since only limited experimental data are available in the open literature to verify the computational results, an experiment study was performed to obtain measurements of CO2 level, temperature, and pressure during the carbonation process in the bottle filled with liquid. Both experimental and numerical studies of various flow condition and different sizes of injection tube are presented in this paper.
An Experimental Study of Liquid Entrainment by Rapid Surface Swelling of Two-Phase Mixture in a Vessel
Authors: Chun Moon-Hyun , Seo Kyong-Won , Kim Hyeng-Kuk
Published: November 2021

An experimental study of liquid entrainment by rapid surface swelling of a two-phase mixture in a vessel has been performed. To investigate the effects of air flow rate and initial water level on the liquid entrainment, a series of experiments have been performed using air and water as working fluid.

A total of 64 experimental liquid entrainment rate data have been obtained for various combinations of the test parameters (i.e., for six different initial water levels and various air flow rates) using two test vessels that have the same height but different inner diameters (0.15 and 0.3m, respectively) for vertical bubbly and churn-turbulent flow conditions.

An empirical correlation for the liquid entrainment rate, E has been developed in terms of the superficial velocity of air, the initial water level, the density of gas, the surface tension, and the gravity. This correlation shows a good agreement with the present experimental data within ±30% over a wide range of flow parameters.
Numerical Simulation of Bubble Dynamics in the Presence of Boron in the Liquid
Authors: Bai Qiang , Dhir V. K.
Published: November 2021

Deposition of boron on the fuel rod cladding during boiling of water containing boron can depress the neutron flux and lead to a decrease in nuclear reactor power output. There is practically little precise information on the temperature field, the gradients of chemical concentration and deposition of boron on the cladding surface. The objective of the present work is to simulate the nucleate boiling process along with velocity, temperature and concentration fields of aqueous boron in the vicinity of the cladding of a fuel rod.

As a first step in solving the complete problem, two-dimensional numerical simulation of a bubble growth on a horizontal surface is considered. A finite difference scheme is used to solve the equations governing conservation of mass, momentum, energy and species concentration. The calculation domain is divided into macro and micro regions. In macro-region, the governing equations are used to calculate the distributions of velocity, temperature, and concentration. The Level Set method is used to capture the evolving liquid-vapor interface. For micro-region, lubrication theory is used, which includes the disjoining pressure in the thin liquid film. The solutions for micro-region and macro-region are matched at the outer edge of the micro-layer. A dilute aqueous Boron solution is considered in the simulation. From numerical simulations, the dynamic change in concentration distribution of boron during the bubble growth shows that the precipitation of boron can occur near the advancing and receding liquid-vapor interface when the ambient boron concentration level is 0.003.
Multiphase Flows With Two Liquid Phases
Authors: Hewitt G. F.
Published: November 2021

Liquid-liquid two-phase flows and liquid-liquid-gas flows occur widely in industrial applications. A particularly important case is in hydrocarbon recovery where such flows occur in subsea pipelines carrying produced fluids (oil, water and natural gas) from subsea wells to on-shore or platform-based processing facilities. The presence of a second liquid phase makes gas-liquid flows even more complex. At higher gas velocities, the liquid phases tend to become inter-dispersed. The dispersions formed can either be of oil drops dispersed in water or water drops dispersed in oil. The transition between one form of dispersion and the other is called phase inversion and is accompanied by anomalous behaviour signalled by a large increase in pressure gradient. A similar inversion phenomenon occurs in liquid-liquid flows at high superficial velocity. In this presentation, recent Imperial College work on this class of flows will be presented. This includes studies of overall parameters such as pressure gradient and phase holdups (the latter being measured using dual energy gamma densitometry) and investigations of local phenomena and parameters (e.g. drop size and interfacial structure) using advanced optical and other techniques. Both steady state and transient flow have been studied. Progress on meeting the formidable challenges of modelling such flows is also reviewed.
Small Diameter Effects on Internal Flow Boiling
Authors: Kendall Gail E. , Griffith Peter , Bergles Arthur E. , Lienhard John H.
Published: November 2021

Since the 1950’s, the research and industrial communities have developed a body of experimental data and set of analytical tools and correlations for two-phase flow and heat transfer in passages having hydraulic diameter greater than 6 mm or so. These tools include flow regime maps, pressure drop and heat transfer correlations, and critical heat flux limits, as well as strategies for robust thermal management of HVAC systems, electronics, and nuclear power plants. Designers of small systems with thermal management by phase change will need analogous tools to predict and optimize thermal behavior in the mesoscale and smaller sizes. Such systems include a wide range of devices for computation, measurement, and actuation in environments that range from office space to outer space and living systems. This paper examines important proceses that must be considered when channel diameters decrease, including flow distribution issues in single, parallel, and split flows; flow instability in parallel passages; manufacturing tolerances effects; nucleation processes; and wall conductance effects. The discussion focuses on engineering issues for the design of practical systems.
Dynamics of the Flows in Micro-Channels of a Capillary Pumped Loop (CPL) Evaporator
Authors: Lee Hyoung-In , Cho Hye-Jung , Song In-Seob , Lee Ju-Hyeong
Published: November 2021

Cooling of electronic components is often limited by space availability and power consumption. Capillary-pumped loops (CPL) are utilized to achieve a coolant circulation via self-activated capillarity (Faghri, 1995). However, CPL is extremely unstable due to a nonlinear feedback among capillarity, viscous force, and heat transfer. Conventional refrigeration theories, which usually allow a larger pressure jump due to an external pumping, failed to explain the CPL cycle.

The dynamics of a flow through a CPL cooling cycle is investigated with a particular attention to the flow in the micro-channels. Full numerical approaches, by which multi-component multi-phase flows are solved, tend to obscure the engineers from identifying outstanding design parameters. Instead, one here adopts several simplified semi-analyitic approaches, namely, models based on single-phase flows with discrete zones of heating and cooling. The analytical and numerical results could explain some general tendencies in the dynamical features like dry-out and flooding. However, the problem still requires closer and more realistic modeling.
Measurement of Condensation Heat Transfer Coefficients in Microchannel Tubes
Authors: Garimella Srinivas , Bandhauer Todd M.
Published: November 2021

A technique for the measurement of condensation heat transfer coefficients in microchannels is reported. The high heat transfer coefficients and low mass flow rates in microchannels make it difficult to accurately measure these coefficients. The requirements for accurate heat duty measurement are in direct conflict with the requirements for deducing the heat transfer coefficients from measured temperatures and flow rates. In addition, measurement of local condensation heat transfer coefficients in small increments of quality is difficult to accomplish due to the low heat transfer rates for such quality changes. The present work reports a technique that addresses these requirements. The inlet and outlet qualities to a microchannel test section are measured through energy balances on a pre- and post-condenser. The test section is cooled using water at a high flow rate to ensure that the condensation side presents the governing thermal resistance. Heat exchange with a secondary cooling water stream at a much lower flow rate is used to obtain a large temperature difference, which is in turn used to measure the condensation duty. Local heat transfer coefficients are therefore measured in small increments for the entire saturated vapor-liquid region. This technique is demonstrated using a square microchannel geometry with a hydraulic diameter of 0.76 mm. Heat transfer coefficients for the condensation of refrigerant R134a in this geometry range from 2,110–10,640 W/m2–K over the mass flux range 150 < G < 750 kg/m2–s.
Measurement of the Temperature Field at the Tool-Chip Interface in Machining
Authors: Narayanan V. , Krishnamurthy K. , Chandrasekar S. , Farris T. N. , Madhavan V.
Published: November 2021

The measurement of the temperature field at the tool-chip interface in machining has been demonstrated. The key elements in the measurement technique are the use of an optically transparent sapphire tool, which has enabled direct images of the tool-chip contact area in the infra-red to be obtained at high spatial and temporal resolution; and radiation intensity measurements in two wavelength windows which have enabled the temperature field to be accurately derived from these intensity values. The principal characteristics of the temperature field such as the variation of temperature with position along the interface and the location of the region of highest temperature are identified. The implications of this measurement to our understanding of the tribology of the tool-chip interface and machining process models are briefly discussed.
Microstructure-Level Modeling of Ductile Iron Machining
Authors: Chuzhoy L. , DeVor R. E. , Kapoor S. G. , Bammann D. J.
Published: November 2021

A microstructure-level model for simulation of machining of cast irons using the finite element method is presented. The model explicitly combines ferritic and pearlitic grains with graphite nodules to produce the ductile iron structure. The behaviors of pearlite, ferrite, and graphite are captured individually using an internal state variable model for the material model. The behavior of each phase is dependent on strain, strain rate, temperature, and amount of damage. Extensive experimentation was conducted to characterize material strain rate and temperature dependency of both ferrite and pearlite. The model is applied to orthogonal machining of ductile iron. The simulation results demonstrate the feasibility of successfully capturing influence of microstructure on machinability and part performance. The stress, strain, temperature, and damage results obtained from the model are found to correlate well with experimental results found in the literature. Furthermore, the model is capable of handling various microstructures in other heterogeneous materials such as steels.
A Model-Based Prediction Approach to Understanding Tool Wear
Authors: Kim W. , Wong T. , Kwon P.
Published: November 2021

Since the development of Taylor’s wear equation in the early 1900s, empirical approaches to tool wear have been extensively used by industries. However, as many types of work materials and cutting tools have emerged, developing the empirical equation for each combination of work material and cutting tool is too costly and time-consuming. In this paper, we present a promising new model-based approach, where the developed model can be directly extended to other work materials and cutting tools. However, when machining pearlitic steels at high cutting speed, phase transformation restricts the model’s applicability. With phase transformation, the associated flank wear does not follow the model’s predictions. Evidently, the abrasive action of cementite is suppressed as the cementite phase in pearlitic microstructure transforms into austenite. This paper summarizes and reevaluates our previous experimental results in order to develop a model-based approach to understanding and predicting tool wear.
Deformation During High Pressure and Pressure Sequence Hydroforming of Tubes
Authors: Orban H. , Hu S. J. , Duncan J. L. , Morphy Gary
Published: November 2021

Hydroforming is a process used to manufacture tubular sections from circular tubes. Two systems for hydroforming are mainly used, high pressure hydroforming (HPH), and pressure sequence hydroforming (PSH). In this paper, an energy approach is used to calculate the compressive forces developed in the tube wall during deformation in PSH. The pressure required to prevent buckling of the tube wall is estimated based on a two dimensional buckling model. The differences in the mechanics of deformations between HPH and PSH are explained. The advantages and limitations of both systems are also summarized.
Enhancement of Coil Stiffness Using a Cardboard Core
Authors: Li Shunping , Cao Jian
Published: November 2021

Problems of excessive coil deformation after winding will present difficulties in later material handling. Sheet material with a lower stiffness is more likely to deform than solid sheet coil. In this paper, numerical and analytical methods are used to study the factors causing this problem. The results can be used to estimate the requirement of the supporting core material to prevent this excessive coil deformation.
Performance Characterization of Micromachined Tunneling Infrared Detectors
Authors: Ajakaiye Olaleye , Shin Choongsoo , Grade John , Kenny Thomas W.
Published: November 2021

The individual assembly of early generation tunneling infrared detectors required time and skill that were incompatible with high volume production and resulted in large variations in key device operating parameters. The parts of the sensor were glued together and the yield was poor. This paper describes the first successful wafer scale production of micromachined tunneling infrared detectors. The detectors produced with this process feature performance consistent with the best tunneling sensors developed so far and are suitable for use as state-of-the-art uncooled infrared detectors. The noise in these detectors is measured to be below 30 μV/rtHz with a corresponding noise equivalent power (NEP) of less than 10−8 W/rtHz.
Magnetically Actuated, Circular Diaphragm Pumps Fabricated With Low-Temperature, Co-Fired Ceramic Tapes and Kapton Polyimide Films: Experiments and Theory
Authors: Kim Moon , Ananthasuresh G. K. , Bau Haim H.
Published: November 2021

Magnetically actuated diaphragm pumps were fabricated with low temperature co-fired ceramic (LTCC) tapes and Kapton polyimide film. The pumps consisted of a chamber machined in a LTCC substrate. The chamber was covered either on one or both sides with Kapton diaphragms on which copper coils were patterned. The diaphragms were actuated by passing electric current through the coils in the presence of permanent magnets. Passive Kapton flap valves were used to direct fluid flow into and out of the chamber. The first design consisted of a single, circular diaphragm pump. In the second design, two circular diaphragms were used. The two diaphragms are deflected into and out of the pressure chamber simultaneously. Flow rates of up to 7 mL/min were measured. The static response of a circular diaphragm subjected to magnetic forces was computed using the finite element method (FEM). The effect of the copper coils on diaphragm stiffness was accounted for. The design parameters (the number of windings and the size and location of the magnet) needed to maximize the volumetric displacement were determined. At relatively high currents, the coils heated up significantly and caused the pump’s performance to deteriorate.
A CMOS-MEMS Micromirror With Large Out-of-Plane Actuation
Authors: Xie Huikai , Pan Yingtian , Fedder Gary K.
Published: November 2021

This paper reports a high-aspect-ratio, silicon-based vertical comb drive used to actuate a micromirror. The large displacement is achieved by the curled-up comb drives. This high-aspect-ratio vertical comb drive uses the vertical capacitance gradient of the sidewall capacitor existing between comb fingers. The electrical isolation is realized by using the undercut of the deep Si etch. The 1 mm by 1 mm micromirror is made of an approximately 40 μm-thick single-crystal silicon membrane with aluminum coated on the surface. The mirror has a peak-to-peak curling of 0.5 μm. The mechanical rotation angle of the mirror is ±5°. The fabrication process is compatible with standard CMOS processes, and there is no need for wafer bonding and accurate front-to-backside alignment. Such capability has potential applications in optical switches, optical scanners, interferometric systems, and vibratory gyroscopes.
Development and Testing of a Planar, Silicon Mini-Capillary Pumped Loop
Authors: Pettigrew Kenneth , Smith Brian , Yerkes Kirk , Gamlen Carol , Liepmann Dorian
Published: November 2021

A planar, silicon mini capillary pumped loop (CPL) was designed, built, and tested using recent MEMS technology to provide integral cooling and temperature control for electronics. This design featured three silicon fusion bonded wafers incorporating an evaporator, condenser, liquid line and vapor line, all of which were dry plasma etched. Grooves were etched in the condenser and evaporator to provide passive capillary pumping. An insulated gate bipolar transistor (IGBT) was bonded to the evaporator region of the CPL and an external reservoir attached to a port hole in the finished device. The CPL was then filled with a working fluid of water. A calorimeter was attached via epoxy above the condenser to control condenser temperature and monitor heat removal. The mini-CPL was operated with an input heat load ranging from 3 to 10 W resulting in the junction temperature of the IGBT being reduced approximately 15 C from that of a solid SI substrate. This mini-CPL also performed as a thermal diode, turning on or off depending on the reservoir temperature. Work is in progress to understand the dynamics observed in the CPL as well as increase the CPL’s performance to its full potential.
Actuation of MEMS by Light: An Optical Actuator
Authors: Sulfridge Marc , Saif Taher , Miller Norman , O’Hara Keith
Published: November 2021

This paper presents experimental evidence that MEMS devices may be manipulated using beams of light. Light possesses momentum, and hence it imparts a force equal to 2W/c when perfectly reflected by a surface. Here W is the total power of the reflected light, and c is the speed of light. The radiation pressure of light can be quite significant to MEMS devices. This actuation method is demonstrated, both in air and in vacuum, by switching the state of a bi-stable MEMS device. The associated heat transfer model is also presented.
Stress Relaxation of Gold/Polysilicon Layered MEMS Microstructures Subjected to Thermal Loading
Authors: Zhang Yanhang , Dunn Martin L.
Published: November 2021

We study both experimentally and theoretically the stress relaxation behavior of a series of gold/polysilicon MEMS microstructures fabricated by the MUMPs surface micromachining process and subjected to thermal loading. We measured, using an interferometric microscope with a custom-built temperature chamber, full field deformed shapes (and from these determined the average curvatures in x and y directions) of gold (0.5 μm thick)/polysilicon (1.5 or 3.5 μm thick) beam and plate microstructures. The microstructures are initially thermal cycled between room temperature and 190°C to stabilize the gold microstructure. After the initial thermal cycle, the microstructures are cooled from 190 °C to 120 °C and held at 120°C for about six weeks. During the isothermal hold, stress relaxation is observed in all of the microstructures. Both material and structural issues contributed to the observed deformation response. The coupling of the two was apparent in plate microstructures where the initial cooling caused them to buckle, but the stress relaxation then caused them to substantially unbuckle. We attempted to model the stress relaxation process by assuming simple power-law creep in the gold ε ˙ = A σ n , and assuming that the polysilicon did not relax at the modest temperature of 120 °C. We found that with such a simple model we could not obtain self-consistent results among all measurements. However, with a stress component of n = 5, good agreement was obtained among beam and plate microstructures using a value of A that depended on the microstructure thickness. The reasons for this are unclear presently, but these results resonate with similar studies of thin films on thick substrates in microelectronics contexts.
Resistance of Liquid Metal Droplets Against Actuation on Microstructured Surfaces
Authors: Shen Wenjiang , Kim Joonwon , Kim Chang-Jin “CJ”
Published: November 2021

Liquid metal droplet can be used as contact and moving part in a microswitch system for such application areas as space electronics. In order to build clear knowledge about the behavior of liquid metal droplet under electrostatic actuation, the contact properties of the droplet on structured surface are investigated in this paper. Forces needed to slide or detach a liquid metal droplet on microstructured surface are theoretically analyzed. Micropositionor and a high-resolution goniometer are used to build up testing setup to experimentally evaluate sliding and detaching of the liquid metal droplet. Experimental results show that the physical modification (i.e., microstracturing) of surface can greatly reduce the adhesion between liquid metal droplet and solid surface and ease its actuation.
Mechanical Characterization and Controlled Manipulation of Micro Objects Using Vision-Based Techniques and Compliant Devices
Authors: Wang Xiaoye , Ostrowski James P. , Ananthasuresh G. K.
Published: November 2021

Stiffness characterization and mechanical manipulation of rigid or flexible micro objects using compliant devices are investigated in this paper. Compliant devices are themselves elastically deformable objects. By using the material properties, geometry, and measured deformations of the compliant devices, the force and deflection of the manipulated object are computed using geometrically nonlinear mechanics formulations. Thus, the stiffness of any given object is characterized. Since the input and output points might be occluded, we have developed an alternate approach where displacement measurement at other points can be used to estimate the forces at input and output points. This new technique also helps reduce the effect of errors in optical capturing of deformations in the computation of forces. By virtue of this vision-based force measurement, we can apply controlled force on the objects, which is a very useful feature in micro assembly and manipulation where excessive force might damage the object. Additionally, we demonstrate manipulation with compliant devices utilizing vision-guided position and force control. Illustrative examples at micro and macro size scales are included.
Selective Chemical Liquid Deposition for Fabrication of Mini-Structures and Microsystems
Authors: Zhou Jack G. , Wang Feng
Published: November 2021

Most technologies used in fabrication of MEMS involve very sophisticated and expensive processes, which limit the application of MEMS greatly. This paper presents our research on a new manufacturing technology named Selective Chemical Liquid Deposition for Mini-structures and Microsystems SCLD-MSMS. In SCLD-MEMS, small droplets of solution or liquid reactant are ejected from a nozzle at room temperature, the droplets decompose or react with each other after impinging upon a hot substrate, the reacted solid products will then deposit on the substrate. By controlling the droplet size, the flow rate, the motion of the nozzle, and the temperature of the substrate, as well as other process parameters, a desired 3-D microstructure of deposited material can be formed through layer-by-layer scanning technique. The working principle and some experiment results are discussed in this paper.
A Review of Laminar Single-Phase Flow in Microchannels
Authors: Papautsky Ian , Ameel Tim , Frazier A. Bruno
Published: November 2021

Microfluidics plays a major role in the development of many innovative research activities aimed at the development of miniaturized devices and systems, and new applications related to microscale handling of fluids. As the field of microfluidics continues to grow, it is becoming increasingly important to understand the mechanisms and fundamental differences involved in microscale fluid flow. This paper presents a summary of the experimental research efforts in the area of microscale single-phase internal fluid flow and discusses issues associated with investigating microscale flows. While the currently available experimental data indicate the presence of microscale phenomena, they do not unequivocally identify the effects. There is a clear need for additional experimental investigations.
Operational Limits of Suspension Flows Through Sudden Contractions
Authors: Stoeber Boris , Español Eddie , Liepmann Dorian
Published: November 2021

In many microfluidic MEMS (Micro Electromechanical Systems) especially in μTAS (micro Total Analysis Systems) suspensions of small particles are transported from relatively large chambers into small channels. The sudden contractions at the entrance to these channels are critical flow regions where high shear occurs in the fluid. Even very small particles at low concentrations have been observed to accumulate in these regions where they clog the channel inlet occasionally after a short period of time. The operational limitations for three-dimensional suspension flows are examined using dimensional analysis. Thus empirical relations based upon experimental results can be established between the parameters involved in this fluid mechanical problem such as shear rate, particle size and concentration, size and number of sudden contractions, and the time scale of clogging.
Liquid Transport Properties in Sub-Micron Channel Flows
Authors: Westin K. Johan A. , Breuer Kenneth S. , Choi Chang-Hwan , Huang Peter , Cao Zhiqiang , Caswell Bruce , Richardson Peter D. , Sibulkin Merwin
Published: November 2021

An experimental set-up for pressure driven liquid flow through microchannels have been designed and tested. The flow rate is determined by tracking the free liquid surface in a precision bore hole using a laser distance meter. Measurements of the flow rate through silicon microchannels with a height of less than 0.9 μm show good results for Newtonian fluids (silicon oil, ethanol) at flow rates as low as 0.2 nl/s. The experimental results are also in very good agreement with predictions based on laminar channel flow using no-slip boundary conditions, indicating that standard macroscopic assumptions are still valid for these fluids under these conditions. However, experiments with aqueous solutions show anomalies in the form of unexpectedly low flow rates and time dependent variations. Possible explanations to these observations are discussed.