bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parallelized DSMC Modeling of Transport Near Liquid-Vapor Interfaces in a Micro Bubble Heat Pipe
Authors: Jiang Ping , Carey Van P. 
Published: November 2021

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.