bluuebunny/crossref_metadata_2025 huggingface dataset:
Air Ingress Analyses on a High Temperature Gas-Cooled Reactor
Authors: Oh Chang H. , Moore Richard L. , Merrill Brad J. , Petti David A.
Published: November 2021

A loss-of-coolant accident is one of the design-basis accidents for a high-temperature gas-cooled reactor (HTGR). Following the depressurization of helium in the core, if the accident is not mitigated, there exists the potential for air to enter the core through the break and oxidize the in-core graphite structure in the modular pebble bed reactor (MPBR). This paper presents the results of the graphite oxidation model developed as part of the Idaho National Engineering and Environmental Laboratory’s Directed Research and Development effort.

Although gas reactors have been developed in the past with limited success, the innovations of modularity and integrated state-of-art control systems coupled with improved fuel design and a pebble bed core make this design potentially very attractive from an economic and technical perspective. A schematic diagram of a reference design of the MPBR has been established at a major component level (INEEL & MIT, 1999). Steady-state and transient thermal hydraulics models will be produced with key parameters established for these conditions for all major components. Development of an integrated plant model to allow for transient analysis on a more sophisticated level is now being developed. In this paper, preliminary results of the hypothetical air ingress are presented. A graphite oxidation model was developed to determine temperature and the control mechanism in the spherical graphite geometry.
Frost Growth in Regenerative Heat Exchangers: Part II — Simulation and Discussion
Authors: Shang W. , Chen H. , Evitts R. W. , Besant R. W.
Published: November 2021

In this paper a numerical simulation of frost growth is compared with experimental data that was taken for similar operating conditions as those for regenerative wheels. One set of simulation results for the frost growth model (Part I) is presented to predict frost growth in a regenerative wheel with a cold supply air temperature of −40 °C, a warm exhaust temperature of 20 °C and 50% relative humidity. Cyclic and longer time duration frost properties are presented along with the spatial distribution of frost within the wheel. It is concluded that frost blockage effects will become very significant in only 20 minutes of operation.
Natural Convection Influenced Ice-Water Systems Contained Between Concentric Spheres
Authors: Sinton D. A. , Baliga B. R.
Published: November 2021

A computational study of natural convection influenced ice-water systems contained in the annular space between two concentric isothermal spheres is presented. An adaptive-grid control-volume finite element method (CVFEM) formulated for the solution of two-dimensional planar and axisymmetric problems was used in the computer simulations. The grid was designed to delineate the solid-liquid interface using a structured adaptation technique. In this study, attention is limited to three different two-dimensional axisymmetric, steady state, pure ice-water systems, with buoyancy-driven natural convection in the liquid phase: two of these systems involve ice adjacent to the inner sphere, and one system involves ice adjacent to the outer sphere. The dimensionless parameters are the following: a modified Rayleigh number, a density inversion parameter, the Prandtl number, radius ratio, and a temperature ratio. The results presented include solid-liquid interface shapes, streamlines and temperature contours in the liquid phase, and dimensionless local heat flux distributions along the surfaces of the inner and outer spheres, and the interface.
Parallelized DSMC Modeling of Transport Near Liquid-Vapor Interfaces in a Micro Bubble Heat Pipe
Authors: Jiang Ping , Carey Van P.
Published: November 2021

The investigation summarized in this report explores a new efficient computational method for predicting heat and mass transfer near liquid-vapor interface in a micro bubble heat pipe. In the micro bubble heat pipe considered here, net vaporization occurs over heated portions of the interface and net condensation occurs on cooled portions of the interface. A dynamic equilibrium is reached when the condensation just balances the vaporization. The dimensions of the micro heat pipe may be comparable to the mean free path of the inside gas molecules. Since the transport may then fall in the transition regime between continuum and free molecular transport, a stochastic modeling scheme, the direct simulation Monte Carlo (DSMC), is used to simulate the transport by modeling the molecular transport from the evaporation end to the condensation end. A new treatment of the boundary conditions at the bubble interface is used which properly accounts for the energy and mass balance at the interface as well as thermodynamic requirements that must be imposed there. Parallel computing is successfully applied in this simulation by parallelizing the originally sequential DSMC scheme to shorten the otherwise over 10 hours of computation running time. Different domain decomposition strategies are applied to the parallelization. Dynamic load balancing is realized to further improve performance. A nearly linear speedup is found in the tests with up to 64 parallel processors of T3E Cray super computer, despite the huge amount of message communication among processors in this 3-D problem. Simulation predictions of temperature, pressure, molecular density profiles, and molecular flow speed profile from the simulation are shown to agree with the theoretical analysis of the resulting compressible flow. The results provide insight into the mechanisms of transport in the micro bubble heat pipe and parametric effects on its heat transfer capacity.
Design and Fabrication of a Micro-CPL for Chip-Level Cooling
Authors: Liepmann Dorian
Published: November 2021

This paper summarizes the development of a micro-CPL designed for chip-level cooling. This research indicates that there are numerous fundamental issues regarding the thermofluid dynamics at small scales that are poorly understood. These issues, which can often be ignored at macro-scales, will be critical as devices such as micro-CPL’s and heat pipes are optimized in order to handle the increasingly large thermal loads of modem technology.
Free Surface Tracking and Steady/Unsteady Computational Simulations for Internal Condensing Flows
Authors: Narain A. , Liang Q. , Barve A. S.
Published: November 2021

The computational investigation in this paper explores a new technique for steady and unsteady internal condensing flows in the annular/stratified regime. Simulation capabilities for both steady and unsteady interface laminar/laminar situations are presented for film condensation on the bottom wall of a small-to-moderate gap channel. The unsteady simulations employ a suitable adaptive grid and the solution of an interface tracking hyperbolic equation (of the type used in level-set or VOF methods). At each time-step, the scheme locates the interface, solves the Navier-Stokes equation in each phase, satisfies the full non-linear conditions at the phase change interface, and satisfies the necessary inlet, outlet, and wall conditions.

The stability and instability of various exit condition dependent steady solutions are inferred from direct unsteady simulations and this leads to insights into the flow mechanisms that determine the eventual quasi-steady flows. For some cases it is found that waviness and heat transfer rates are enhanced significantly by the flow’s sensitivity to the frequency content of persistent noise in the inlet data.
A Photographic Insight Into the Motion of Liquid-Vapor Interface During Rapid Evaporation of a Liquid Droplet on a Heated Surface
Authors: Kandlikar Satish G.
Published: November 2021

Photographic observations of the boiling phenomena have played an important role in gaining insight into the boiling mechanism. This paper presents a brief historical review of the available literature on the photographic studies in pool and flow boiling. This is followed by the results of the photographic studies conducted in the author’s laboratory on liquid droplets impinging on a heated surface. Liquid-vapor interface and contact line movements are observed through a high speed camera at high resolution. The effect of surface roughness an surface temperature on dynamic advancing and receding contact angles has been studied. Also, the effect of rapid evaporation on advancing and receding contact angles, liquid-vapor interface motion, and dryout front propagation have been investigated.
Measurements of the Velocity Field With MTV During the Solidification of an Alloy Analog With Mushy Region
Authors: Lum C. L. , Koochesfahani M. M. , McGrath J. J.
Published: November 2021

A previous application of the advanced diagnostic method, Molecular Tagging Velocimetry (MTV), showed promise with respect to providing an improved understanding of velocity fields in the complex thermo-solutal flows associated with solidification in the presence of significant buoyancy. The present study extends the earlier results (Wirtz et al, 1998) in an ammonium-water alloy analog by demonstrating the capability of quantifying two components of the instantaneous velocity vectors of such flows. The model alloy was directionally-solidified by chilling from below. Velocity vectors were measured near the solidification front at early phases (∼3minutes) of the solidification when fine structures exist. Well-defined convective flow patterns were documented with velocities on the order of 1 mm/s measured for both velocity components. Velocity vectors within and around a plume were also measured further away from the solidification front later in the solidification process (∼100 minutes). The optical grid used for tagging must be refined to provide adequate spatial resolution within the plumes. The capabilities and limitations of the MTV method in its present realization are described. The results demonstrate that the MTV method is a powerful tool that can be expected to provide valuable data related to complex thermo-solutal flows associated with solidification in the presence of significant buoyancy.
Non Linear Laminar Flow Characterization for Different Fabric Pore Shapes
Authors: Le Coq Laurence A. M. , Pavageau Michel H. , Solliec Camille H.
Published: November 2021

The hydrodynamic behavior of a plane fabric filter was investigated. The emphasis was put on the influence of cloth weave onto flow structure downstream from the filtering media. Experiments were performed on a 50:1 scaled-up glass model of a 3-ply twill textile sample used in water treatment applications. Air was used as working fluid. The Reynolds similarity criterion was applied to design the experimental facility used throughout this work. This entailed a mean flow velocity of 0.07 m/s. Particle Image Velocimetry (PIV) was used to observe and analyze the flow structure past inter-yarn pore models of various shape. Comparisons of mean velocity profiles upstream and downstream from the model were made to determine the distance over which wake effects remain noticeable case depending.
Microstructure-Level Force Prediction Model for Micro-Milling of Multi-Phase Materials
Authors: Vogler Michael P. , DeVor Richard E. , Kapoor Shiv G.
Published: November 2021

A mechanistic model for the micro-endmilling process is developed that explicitly accounts for the different phases in heterogeneous materials. It is shown that frequencies in the cutting force signal higher than those that can be explained by the kinematics of the process can be explained by considering the multiple phases in the material. Experiments are performed on ductile iron workpieces and pure ferrite and pearlite workpieces that show that the nature of the variation in the ductile iron cutting force signals can be attributed to the mixture of the phases. Specifically, simulation studies show that the frequency component of the variation is related to the spacing of the secondary (ferrite) phase and the magnitude of this component is determined by the size of the secondary phase particles.
Delamination Models in Drilling of Composite Materials Using Saw Drill and Candle-Stick Drill
Authors: Ho-Cheng H. , Tsao C. C.
Published: November 2021

Drilling is the most frequently employed operation of secondary machining for fiber-reinforced materials owing to the need for structure joining. Delamination is one of the serious concerns during drilling. Practical experience proves the advantage of using such special drills as saw drill and candle stick drill. Comprehensive delamination models for twist drill, saw drill and candle stick drill in drilling of composite materials are constructed in the present study. Of the three, the saw drill offers the highest critical thrust force followed by the candle stick drill, while the traditional twist drill allows for the lowest thrust force. A guide for drill design can be developed based on the proposed models.
An Experimental and Computational Study of Temperature and Strain Fields in Metal Cutting
Authors: Zehnder Alan T. , Potdar Yogesh K. , Deng Xiaomin , Shet Chandrakant
Published: November 2021

Metal cutting is a thermo-mechanically coupled process in which plasticity induced heating and friction play a critical role. In this paper, we outline a methodology that combines high resolution experiments with numerical simulations. The simulations were performed with a general purpose finite element code. With this code we evaluate the effects of chip-tool interface friction and rake angle on temperature and cutting force and show that results for residual stresses in the workpiece are consistent with experimental data. We hypothesize that by closely coupling simulations to fine scale spatial and temporal experimental measurements of temperature and strain fields, questions related to choice of parameters in FE simulations can be resolved. We have designed and conducted orthogonal cutting experiments to measure temperatures, using IR detectors, with a spatial resolution of 27 × 27 μm and time scale of 200 ns. Experimentally obtained temperature fields are compared with FE results. We also obtain deformation fields with a spatial resolution of 50 × 50 μm.
Development of a Model for the Prediction of the Energy Partition in a Peripheral Milling Operation
Authors: Shen G. , Arici O. , Sutherland J. W.
Published: November 2021

Over the last several decades, much research has been performed to establish models that contribute to a fundamental understanding of the peripheral milling process. In this paper, a model for the prediction of the energy partition in the peripheral milling process is presented. When integrated with other milling model elements from the technical literature, the workpiece temperature change produced by the energy/heat that flows into the workpiece can be predicted. The energy partition model consists of two sub-models, with the first sub-model directed at estimating the portion of the shear zone heat that does not escape with the chip. The second sub-model is focused on quantifying the fraction of the heat that passes into the final machined workpiece. Both sub-models are initially formulated as two-dimensional, quasi steady-state, homogeneous boundary value problems of heat conduction and heat transfer via mass transport with constant coefficients in a semi-infinite domain. The energy partition model is validated through a set of milling experiments performed according to a 25-1 fractional factorial design. For the conditions examined, the model predicted and experimentally observed energy/heat fraction entering the workpiece varies between 23% and 43%. The model predicted energy partition and temperature behavior is seen to be in good agreement with the experimental results.
Machining Simulation of Ductile Iron and its Constituents: Part I — Estimation of Material Model Parameters and Their Validation
Authors: Chuzhoy L. , DeVor R. E. , Kapoor S. G. , Beaudoin A. J. , Bammann D. J.
Published: November 2021

A microstructure-level simulation model was recently developed to characterize machining behavior of heterogeneous materials. During machining of heterogeneous materials such as cast iron, the material around the machining-affected zone undergoes reverse loading, which manifests itself in permanent material softening. In addition, cracks are formed below and ahead of the tool. To accurately simulate machining of heterogeneous materials the microstructure-level model has to reproduce the effect of material softening on reverse loading (MSRL effect) and material damage. This paper describes procedures used to calculate the material behavior parameters for the aforementioned phenomena. To calculate the parameters associated with the MSRL effect, uniaxial reverse loading experiments and simulations were conducted using individual constituents of ductile iron. The material model was validated with reverse loading experiments of ductile iron specimens. To determine the parameters associated with fracture of each constituent, experiments and simulation of notched specimens are performed. During the validation stage, response of simulated ductile iron was in good agreement with the experimental data.
A High-Magnification Experimental Study of Orthogonal Cutting With Edge-Honed Tools
Authors: Kountanya Raja K. , Endres William J.
Published: November 2021

Past work on the subject of cutting with a blunt tool has focused mostly on the effect of deformation of the work material and on the process forces. A number of investigators have shown that in orthogonal machining, when the uncut chip thickness approaches the size of the edge radius, size-effect like phenomena greatly influence the forces and sub-layer deformation of the workpiece. However, in terms of visual evidence of how the material deforms in the vicinity of the cutting edge, their work is only loosely supported. In this paper, we describe the apparatus used in a high-magnification experimental study of blunt-edged cutting, wherein real-time observation of deformation near the cutting edge is possible with simultaneous force measurement. Preliminary results for the machining of zinc are reported for a range of uncut chip thicknesses chosen such that its ratio to edge radius varies between 0.5 and 35. The upper-bound plasticity model of Manjunathiah and Endres (2000a) is used to analyze the data in terms of steady-state stress, strain and strain-rate for the process. For the case of cartridge brass, a stable dead metal cap is noted to form on the edge radius. Proposed modeling directions are briefly discussed.
An Intrinsic Size-Effect in Machining Due to the Strain Gradient
Authors: Dinesh D. , Swaminathan S. , Chandrasekar S. , Farris T. N.
Published: November 2021

It has been suggested recently [1–4] that an increase in the hardness value often observed when the indentation size is reduced (indentation size effect) in metals is a consequence of the dependence of the flow stress of the metal on the strain gradient. Here, we show based on an analysis of the strain gradient in machining, that a similar size effect should be observable when machining at small values of the undeformed chip thickness. Such a size effect will manifest itself as a continuous increase in the specific cutting force as the chip thickness is reduced. Furthermore, the size effect in machining is likely to be much more pronounced than in indentation, because of the more intensive strain gradient prevailing in the deformation field in machining. The dependence of the flow stress on strain gradient is not an artificial construct but has a well-established basis in the dislocation theory of hardening [5].

Our analysis suggests that an effective test of plasticity constitutive laws that incorporate the strain gradient as a parameter can be achieved using a simple 2-D cutting experiment with a sharp tool carried out at very low speeds. Such a test may be carried out with ductile pure metals as workpieces wherein this size effect is expected to be most significant.
Dynamic Modeling for Machine Tool Thermal Error Compensation
Authors: Yang Hong , Yuan Jingxia , Ni Jun
Published: November 2021

This paper presents a new thermal error modeling methodology called the Dynamic Thermal Error Modeling which improves the accuracy and robustness of the machine tool thermal error model. The characteristics of the thermoelastic system are investigated from the dynamic system viewpoint. The pseudo-hysteresis effect is revealed to be the major factor causing poor robustness of the conventional static thermal error model. System identification theory is applied to build the dynamic model for machine tool thermal error on-line estimation. The modeling procedure for the linear Output Error (OE) model is illustrated using simulation work for both one-dimensional spindle and two-dimensional machine structure thermal deformations. Model performance evaluation through spindle experiments shows that the thermal error dynamic model has advantages over the static model in terms of model accuracy and robustness.
Modal Inverse Frequency Response Heat Transfer Analysis for Estimation of Machine Tool Transient Thermal Loads
Authors: Ma Youji , Yuan Jingxia , Ni Jun
Published: November 2021

Thermal loads of internal and external sources cause thermal deformations of a machine tool structure and affect its accuracy. Software-based real-time error compensation method is an effective way to reduce the thermal errors. However, lack of knowledge of thermal loads impedes greater success. In this paper, a method of inverse heat transfer analysis is developed that, using temperature measurement data from multiple sensors mounted on a machine tool structure, the transient thermal loads of multiple heat sources can be estimated simultaneously. The method uses modal method and is carried out in frequency domain. The temperature measurement data are first transformed into frequency spectra through DFT. The modal method of inverse frequency response analysis is then used to obtain the thermal load spectra. Finally the thermal loads are recovered from their spectra through IDFT. The estimated thermal loads play crucial roles in estimating transient temperature fields and transient thermal errors of a machine tool structure. The issues of mode truncations and frequency truncations, and their effects on the efficiency and stability of the method are also discussed with simulation results. Finally, experimental results on a machining center column are presented.
Institutionalized University and Industry Partnership in Multidisciplinary Design and Build: Product and Process Realization
Authors: Stanfill R. Keith , Wiens Gloria J. , Lear William E. , Whitney E. Dow
Published: November 2021

The intent of this paper is to describe a unique, multidisciplinary undergraduate experiential education program developed at the University of Florida and to share program experiences from 1995 to 2000. The uniqueness of the Integrated Product and Process Design (IPPD) Program comes from the diversity of the 10 student and faculty disciplines involved, the variety of project types undertaken — including hardware, process and software orientations, the support from a variety of industries and the delivery of the course content to support such a wide range of disciplines and project definitions. The specifics presented in this paper will focus more on the hardware development than the software development. IPPD is institutionalized at the University of Florida and approximately 25% of the students within each participating engineering discipline participate.
Influence of Geometrical Factor on Heat Conduction Rate During GTAW for Welding-Based Deposition
Authors: Kmecko Ivan S. , Jandric Zoran , Kovacevic Radovan
Published: November 2021

To successfully control the welding process and make it appropriate for the welding-based deposition (WBD) process, it is necessary to fully understand the influence of the welding process parameters and the geometry of the welding scenery on the resulting weld-bead dimensions. A new parameter, referred to as the geometrical factor, was defined in order to reflect on the geometrical configuration in the molten pool vicinity. An accurate dynamic model and an expression for the heat conduction rate that included the net heat input, the filler metal flow rate, the workpiece velocity and geometrical factor, were developed by balancing mass and energy flow through the control volume set around the molten pool. An open-loop controller for the gas tungsten arc welding (GTAW) process, based on the developed model, was designed and experimentally tested by controlling the metal layer deposition process on top of a workpiece with complex geometrical features, such as conformal channels, edges, and corners. The controller performed well and demonstrated the capability to adjust the welding process parameters according to demanding welding conditions.
Femtosecond Excimer (248 NM) Laser Micro-Machining of Teflon (PTFE)
Authors: Adhi K. P. , Owings R. L. , Railkar T. A. , Brown W. D. , Malshe A. P.
Published: November 2021

We have investigated, using X-ray photoelectron spectroscopy (XPS), the surface of polyterafluoroethylene (PTFE) films which were subjected to micromachining by femtosecond UV radiation from an excimer laser (KrF: λ = 248 nm, tp ∼ 380 fs) in air ambient. Bulk characterization of processed PTFE films by Fourier transform infrared spectroscopy (FTIR) allowed us to study laser-induced modifications of the material at energy densities below the ablation threshold. No features in the XPS or FTIR spectra indicated incorporation of hydrogen and/or oxygen or the formation of cross-linked networks of carbon, indicating chemically clean processing in contrast to nanosecond excimer laser processing which chemically degrades the surface being machined. Scanning electron microscopy (SEM) of micrometer size microvias indicates mechanically and thermally damage-free processing of PTFE with good edge quality, again in contrast to nanosecond excimer laser processing.
Microstructure Integrated Modeling of Multiscan Laser Forming
Authors: Cheng Jin , Yao Y. Lawrence
Published: November 2021

Laser forming of steel is a hot forming process with high heating and cooling rate, during which strain hardening, dynamic recrystallization, and phase transformation take place. Numerical models considering strain rate and temperature effects only usually give unsatisfactory results when applied to multiscan laser forming operations. This is mainly due to the inadequate constitutive models employed to describe the hot flow behavior. In this work, this limitation is overcome by considering the effects of microstructure change on the flow stress in laser forming processes of low carbon steel. The incorporation of such flow stress models with thermal mechanical FEM simulation increases numerical model accuracy in predicting geometry change and mechanical properties.
The Diffraction Limitation on Drilling Nano-Meter Holes by Laser Irradiation
Authors: Luo Y. F. , Lineton W.
Published: November 2021

The high resolution of some laser irradiation has important applications in micro machining. In drilling micro holes with a diameter close to or less than 1 micrometer, beam diffraction essentially restricts the final drilling depth due to the finite wavelength of all laser irradiation. Besides diffraction, interference can also affects the drilling results. It is of practical interest for process characterization and evaluation to know these substantial restrictions before application. This investigation tries to determine the correlation between the beam properties and the aspect ratio in drilling micro holes. First, the desirable qualities of laser irradiation will be defined in the situation of drilling micro holes. Given the attributes of electromagnetic wave, the diffraction in drilling is then analyzed. The attention is focused on the situation in which the laser wavelength approaches or exceeds the hole diameter. Fraunhofer diffraction is therefore the dominant pattern that determines the wave intensity inside the free space of micro hole. In accordance with a steady-state thermal equilibrium that terminates any further erosion by laser irradiation, the solution of heat conduction equation determines the final erosion front and the maximum depth. Finally, the minimum required power density of a femtosecond laser is estimated by solving a transient heat conduction equation. The effects of ultra-short pulses on diffraction and hole quality are also analyzed.
Balancing of Competitiveness Metrics and Measures for Excellence in Manufacturing
Authors: Dwivedi Suren N. , Prasad Biren
Published: November 2021

Many manufacturing companies are finding that true increase in productivity and efficiency begins with strategies such as clean and efficient process, good communication infrastructure, teamwork, and a constancy of shared vision and purpose. The challenge is simply not to crank up the speed of the machines so that their outputs (per unit of time) are increased or doubled, but to change the basic machinery, process or strategy that produces those outputs. To accomplish the latter goals, today many organizations are balancing competitiveness metrics and applying competitiveness measures through benchmarking, Continuous Process Improvement (CPI), organizational restructuring, time compression and process re-engineering. Lean Manufacturing is an important and crucial manufacturing competitiveness strategy. Lean Manufacturing strategy improves efficiency through things such as systematic elimination of waste, error-proofing, just-in-time inventory, work place organization, etc. In this paper, author describes two sets of competitiveness metrics and measures that need to be balanced for achieving excellence in manufacturing. These metrics and measures were utilized by major manufacturing companies for solving complex process-improvement and these have been found quite useful for handling actual production economic problems.
Modeling and Simulating MEMS Devices Using Finite Element Analysis
Authors: Gonzalez Ulises
Published: November 2021

In this paper we discuss how Finite Element Analysis (FEA) can be used to simulate Micro Electro Mechanical Systems (MEMS). The mechanical behavior of many MEMS devices is a direct result of non-mechanical physical phenomena, such as electrostatics, electromagnetics or heat transfer. This coupling of mechanical behavior with another physical effect, combined with considerations associated with their small dimensions, poses significant challenges to the analysis of MEMS. These challenges can be met by FEA software capable of performing multiphysics analysis with no limitations on the dimensions of the objects in a model. With such software at their disposal, engineers can use the results of their simulations to design MEMS devices.
A Novel MEMS-Based Technique for In-Situ Characterization of Freestanding Nanometer Scale Thin Films Inside SEM and TEM
Authors: Haque M. A. , Saif M. T. A.
Published: November 2021

We present a MEMS-based technique for in-situ uniaxial tensile testing of freestanding thin films inside SEM and TEM. It integrates a freestanding thin film specimen with MEMS force sensors and structures to produce an on-chip tensile testing facility. Cofabrication of the specimen with force and displacement measuring mechanisms produces the following unique features: 1) Quantitative experimentation can be carried out in both SEM and TEM, 2) No extra gripping mechanism is required, 3) Specimen misalignment can be eliminated, 4) Pre-stress in specimen can be determined, and 5) Specimens with micrometer to nanometer thickness can be tested. We demonstrate the technique by testing a 200-nanometer thick Aluminum specimen in-situ in SEM. Significant strengthening and anelasticity were observed at this size scale.
Tunable Phase Grating Using CMOS Processes
Authors: Yang Yu-Sheng , Liu Cheng-Hsien , Chou Bruce C. S.
Published: November 2021

We present the development of a tunable phase grating using CMOS process in this paper. With CMOS processes, structure feature of sub-micrometer can be easily approached. In the design of our grating devices, we have ribbons of 0.7um and minimum separate spacing of 0.65um between ribbons. We used aluminum as ribbon material in our design, The ribbons were released via RIE to remove the SiO2 sacrificial layer. In our devices, we have successfully released the ribbons with the width from 0.7um up to 2um. The dry etching processes, which we developed to release ribbons in our devices, can avoid sticking problems and structure destruction. For electrostatic actuator, we use partial electrode design to obtain wider flat-reflection sections, and larger steady tuning distance. In this paper, we describe design, modeling, simulation, and measurement results of our tunable grating devices.
Surface Micromachined Electrothermal V-Beam Micromotors
Authors: Schreiber David S. , Cheng Wei-Jen , Maloney John M. , DeVoe Don L.
Published: November 2021

Surface micromachined electrothermal V-beam microactuators have been investigated and integrated into a microstepper motor design. 2 μm thick, 2 μm wide, 400 μm long polysilicon microactuators were fabricated and tested for displacement and operational lifetime. Displacement results compare well to a theoretical model. Reliability of the microactuators was also evaluated. Arrays of electrothermal V-beam microactuators were developed to provide actuation for novel microstepper motor designs. Motor displacement and speed have been measured, with repeatable 3.2 μm and 2.5 μm step sizes for forward and reverse directions for a driving voltage of 8 V and frequencies up to 1000 Hz. Maximum speeds of 4200 μm/sec and 3100 μm/sec were observed at 8 V and 1800 Hz for forward and reverse operation.
Design and Simulation of Shaped Comb Fingers for Compensation of Mechanical Restoring Force in Tunable Resonators
Authors: Jensen Brian D. , Mutlu Senol , Miller Sam , Kurabayashi Katsuo , Allen James J.
Published: November 2021

The comb-drive actuator is one of the main building blocks of microelectromechanical systems (MEMS). Its working principle is based on an electrostatic force that is generated between biased conductor plates as one moves relative to the other. Because of its capability of force generation, it finds wide application in micro-mechanical systems. Sample applications include polysilicon microgrippers [1], scanning probe devices [2], force-balanced accelerometers [3], actuation mechanisms for rotating devices [4], laterally oscillating gyroscopes [5], and RF filters [6]. Consequently, any improvement to this basic actuator could have far-reaching effects.
Novel Bulk Acoustic Wave Hammer to Determinate the Dynamic Response of Microstructures Using Pulsed Broad Bandwidth Ultrasonic Transducers
Authors: Lai Wen-Pin , Ho Yi-Ping , Fang Weileun
Published: November 2021

A novel testing technique to determinate the dynamic response of the microstructure is presented. In this study, a bulk acoustic wave hammer generated by a pulsed ultrasonic transducer is used to excite the microstructures. Thus the dynamic response of the microstructure in a wide frequency range is excited. Based on this novel method and test apparatus, the dynamic response of the microstructure including the resonant frequency, mode shape and the modal damping of the microstructure can be measured in a single excitation. Experimental results of the microbeams with different length agree well with theoretical predictions. In summary, the proposed BAW hammer technique has the following advantages. The sample preparation for this approach is very easy since it is not necessary to deposit an additional film for thermal or electrical purpose. In this regard, the experimental results of this technique are more accurate since there is no additional film to influence the dynamic behavior of the test sample. Moreover, there is no uncertain side effect such as thermal and acoustic coupling, caused by this approach. Since the test apparatus is also very simple, this approach has the potential to do the on-line test for batch production.
A Novel Testing Apparatus for Tribological Studies at the Small Scale
Authors: Gearing Brian P. , Anand Lallit
Published: November 2021

A novel flexure-based biaxial compression/shear apparatus has been designed, built, and utilized to conduct tribological studies of interfaces relevant to MEMS. Aspects of our new apparatus are detailed and its capabilities are demonstrated by an investigation of two interfaces relevant to MEMS applications. Tribological tests may be performed with normal and tangential forces in the μN to N range and relative sliding displacements in the nm to mm range. In this testing range, the new experimental apparatus represents an improvement over existing techniques for tribological studies at the small scale.
A Piezoresistive Microphone for Aeroacoustic Measurements
Authors: Arnold David P. , Gururaj Sridhar , Bhardwaj Sunil , Nishida Toshikazu , Sheplak Mark
Published: November 2021

This paper presents the characterization of a piezoresistive silicon microphone. The microphone was designed for aeroacoustic measurements where small size, high dynamic range, large frequency bandwidth, and low power requirements are desired. It consists of four dielectrically-isolated, single-crystal silicon piezoresistors mounted on the top surface of a circular, tensile silicon nitride diaphragm. Multiple devices were characterized in terms of linearity, frequency response, drift, noise, and power. The sensors exhibit an average sensitivity of 0.6 μ/Pa·V, a flat frequency response, minimal drift, and consume 15 mW of power when operated at 3 V. They show a linear response up to 160 dB SPL and a 52 dB SPL noise floor (1 Hz bin centered at 1 kHz).
Analysis of a Natural Frequency Tracking System for MEMS Fatigue Testing
Authors: Sun Xiaotian , Horowitz Roberto , Komvopoulos Kyriakos
Published: November 2021

A nonlinear control system that can track the natural frequency of a MEMS resonator was developed in this study. Due to the evolution of fatigue damage, the natural frequency of the resonator decreases. To maintain the device at resonance, a phase-locked loop system is used to track the frequency decay and adjust the driving force accordingly. A model for the control system is introduced and the system behavior is analyzed using an averaging method. A quantitative criterion for selecting the control gain to achieve stability is derived from the analysis. Simulation results are shown to be in good agreement with the prediction of the theoretical analysis.
Design Optimization of a Fully-Compliant Bistable Micro-Mechanism
Authors: Jensen Brian D. , Parkinson Matthew B. , Kurabayashi Katsuo , Howell Larry L. , Baker Michael S.
Published: November 2021

Bistable behavior is desirable for a variety of applications because power is applied only during switching, and the mechanism state remains the same regardless of any power interruptions. The low variability in the stable positions also makes accurate open-loop control of many systems possible, and the precise switching characteristics make them valuable in sensing arrays. In this paper, fully-compliant bistable micromechanisms were modeled using finite elements. This model was then coupled with an optimization program, allowing extensive exploration of the design space. Three designs within this space were generated by minimizing the layout size of the devices subject to force constraints. These designs were subsequently manufactured and tested to verify bistability, with each mechanism snapping as expected between the two stable positions. The design space was then further explored to determine the behavior of the device as the maximum force output increased. This study revealed that the minimum layout size increases with the maximum force output.
Enhanced Copper Microplating Using High Frequency Acoustic Streaming
Authors: Busnaina Ahmed A. , Reynolds V. , Suni Ian , Way T. , Tiwari C. S. , Nakoski M. , Lin Hong
Published: November 2021

There is a need for a fast and effective electroplating process for 100 nm or smaller structures. It is necessary to develop effective and high throughput process that meets the needs for the required side wall step coverage and gapfill. This work investigates the effect of a non-contact physical mechanism (acoustic streaming) to enhance the convection of chemicals near the substrate and improve the gap fill characteristics for copper microplating process.
Temperature-Dependent Property Effects on Laminar Flow Characteristics in a Rectangular Microchannel
Authors: Park Ho Joon , Son Sang Young , Choi Mun Cheol , Lim Geunbae , Song In-Seob , Pak James Jungho
Published: November 2021

This paper investigated experimentally effects of the temperature-dependent property on the laminar flow characteristics in the micro-channel, where water was used as a working fluid. A rectangular straight micro-channel was fabricated with the dimension of 57 μm (H) × 200 μm (W) × 48050 μm (L), in which the resistance temperature detectors (RTDs) were integrated to measure precise temperatures of the fluid directly on the inside-surface of the channel wall. A micro-heater was also installed at the outlet of the channel to generate the heat flux. We measured pressure drop by increasing mass flow rate and the applied heating power. At the same time, micro-Particle Image Velocimetry (micro-PIV) [1] measured the detailed velocity fields along the microchannel, where the wall temperature varied.

Based on the pressure drop and Micro-PIV measurement, it was determined that the variation of the fluid property along the microchannel has an effect significantly on flow resistance but not considerably on the velocity profile. Also, it was observed that flow resistance and velocity field shows a good agreement with those estimated in the macro laminar theory under our experimental conditions.
Design and Fabrication of a Cellular Motor Driven Micro Fluidic System
Authors: Young Jedediah J. , Lee Chuen-Cheak , Malshe Ajay P. , Tung Steve , Manson Michael D.
Published: November 2021

The ability to control the rotational direction of tethered motile bacteria such as Escherichia coli offers an alternative to power micro-electro-mechanical system (MEMS) devices. This paper describes our effort in the development of a micro-fluidic system for small but precise liquid delivery that uses the motility of tethered cellular motors as the driving force for fluidic transport. Based on CFD simulation, micro channels of various cross-sectional areas are fabricated on a 5″ × 5″ × 0.9″ quartz wafer. Integration of the cellular motors is done by bonding the micro channel wafer to a glass slide, which consists of a single layer of cellular motors previously tethered on the slide. With this system, rotation of the cellular motors will be initiated and the resulting volumetric fluid flow in the micro channel will be measured.
Development of an Ejector-Driven Micro-Vacuum Pump
Authors: Wong C. Channy , Aeschliman Daniel P. , Henfling John F. , Sniegowski Jeffry J. , Rodgers M. Steve
Published: November 2021

Recent attempts to miniaturize analytical instruments have led to the demand for mesoscale or microscale vacuum pumps. Existing pump hardware, in both capture and throughput configurations, has difficulty meeting the size, mass, and power consumption requirements of these mini-instruments. At Sandia National Laboratories, we have initiated the development of a micro-vacuum pump. This paper will present our assessment of various mechanisms to pump gas effectively at the micron scale and describe our efforts to build a micro-vacuum pump based upon the ejector principle.
Electrostatically Actuated Surface Micromachined Offset Planetary Gear Pump Design
Authors: Kilani Mohammad I. , Galambos Paul C. , Haik Yousef S. , Chen Ching-Jen
Published: November 2021

An offset planetary pump fabricated in five-level polysilicon surface micromachining is introduced. The pump consists of a ring gear enclosing two planetary gears and an offset sun gear, which generates pumping due to its eccentric rotation. The pump is driven by an electrostatically actuated comb-drive microengine and mechanical power is transmitted to the ring gear through a micro gear train. The paper presents a derivation of pump capacity and the detailed design of its mechanical elements, demonstrating the implementation of relatively advanced mechanical functions in multi-level surface micromachining, including axial roller bearing support, fluidic seal and planetary gear transmission.
Assessment of Viscous Flows in High-Speed Micro Rotating Machinery for Energy Conversion Applications
Authors: Fréchette Luc G.
Published: November 2021

This paper investigates the characteristics of viscous flow in the micron-scale clearances surrounding high-speed micro-rotors currently being developed for miniature energy conversion applications. Analysis and experimental results from 4 mm diameter microfabricated rotors operated above 1 million rpm are used to describe the viscous flow characteristics, and provide guidelines for system-level design. To first order, the flow is characterized as fully developed shear flow (Couette flow) across the small gaps, induced by the rotor motion. However, secondary flows are induced perpendicular to the direction of rotor motion when externally applied pressure gradients exist along the small gaps. The developing flow in the entrance region of the small gaps in this secondary flow direction impacts the shear flow profile, hence affecting the drag on the disk. The effect of other inertial forces, such as Coriolis and centrifugal forces, are investigated analytically and numerically and found to affect the shear flow profile on the fluid in the motor gap at high rotational speeds. Since viscous losses are prevelant in microsystems, appropriate modeling is necessary for system-level design.
Impact of Pumping Surface Separation Distance on Micromachined Silicon Electroosmotic Pump Performance
Authors: Laser Daniel J. , Goodson Kenneth E. , Santiago Juan G. , Kenny Thomas W.
Published: November 2021

We have developed a micromachined silicon parallel-plate electroosmotic pump. A silicon nitride dielectric thin film insulates the etched silicon substrate of the micropump, allowing it to operate at electrical potentials up to 500 volts. Standard silicon micromachining processes are used to fabricated the pump. Like all electroosmotic pumps, this micropump has the advantages of simple architecture, no moving parts, low power consumption, and robust operation. A recently-fabricated prototype micropump of this design generates flow rates in excess of 5 μL/min using deionized water as the working fluid. The finite thickness of the electric double layer must be taken into account when modeling the performance of this electroosmotic pump.
A Case for Magneto Hydro Dynamics (MHD)
Authors: Bau Haim H.
Published: November 2021

In this paper, I review some of our work on the use of magneto hydrodynamics (MHD) for pumping, controlling, and stirring fluids in microdevices. In many applications, one operates with liquids that are at least slightly conductive such as biological fluids. By patterning electrodes inside flow conduits and subjecting these electrodes to potential differences, one can induce electric currents in the liquid. In the presence of a magnetic field, a Lorentz force is generated in a direction that is perpendicular to both the magnetic and electric fields. Since one has a great amount of freedom in patterning the electrodes, one can induce forces in various directions so as to generate complex flows including “guided” flows in virtual, wall-less channels. The magnetic flux generators can be either embedded in the device or be external. Despite their unfavorable scaling (the magnitude of the forces is proportional to the fluid volume), MHD offers many advantages such as the flexibility of applying forces in any desired direction and the ability to adjust the magnitude of the forces by adjusting either the electric and/or magnetic fields. We provide examples of (i) MHD pumps; (ii) controlled networks of conduits in which each conduit is equipped with a MHD actuator and by controlling the voltage applied to each actuator, one can direct the liquid to flow in any desired way without a need for valves; and (iii) MHD stirrers including stirrers that exhibit chaotic advection.