bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Eccentricity on Glass Temperatures in the Neck-Down Stage of the Optical Fiber Drawing Process
Authors: Dogu Yahya , Kaminski Deborah A.
Published: March 2022

A three-dimensional model of the neck-down stage of an optical fiber draw furnace was formulated to examine the effects of eccentricity on preform temperature and flow in the furnace. Eccentricity is an unavoidable off-manufacturing condition, which is the deviation between the centers of the cylindrical furnace and the glass preform rod. The Navier-Stokes and energy equations describing the momentum and thermal transfers in the draw furnace were solved simultaneously both in the glass and gas domains using the finite element method. Temperature dependent physical properties were considered. Radiation heat transfer was added into the model as surface-to-surface radiation between the glass surface and furnace wall, using a full enclosure analysis. Radiation inside the glass was approximated by using the Rosseland diffusion approximation.

The circumferential temperature distribution and viscosity change on the preform surface were determined. They increase with the eccentricity ratio. The eccentricity is the distance between the furnace axis and the preform axis. The gas flow is unsymmetrical due to eccentricity. Most of the temperature gradients and viscosity changes were not large within the furnace due to eccentricity. A balanced temperature field in the furnace is due to the high radiation heat transfer. Since the preform necks down within the furnace and becomes thinner in the lower half, the glass becomes more isothermal due to its high radiation coupled glass conductivity. However, although the resulting temperature difference on the glass preform is small, the gradient is high. This temperature gradient becomes important when the exponential temperature dependence of the glass viscosity is considered. The resulting viscosity difference in the neck-down region will cause the glass to flow faster on one side than on the other side resulting in nonuniform consumption of the glass preform. Thus, the desired symmetric root shape of the glass preform may change.
Asymmetric Glass Temperature due to Cold-Spots on the Furnace Wall in the Optical Fiber Drawing Process
Authors: Dogu Yahya , Kaminski Deborah A.
Published: March 2022

This study represents a three-dimensional numerical analysis of the effects of wall cold-spots on the temperature fields in an optical fiber draw furnace. Radiation heat transfer was added to the energy equation by using the diffusion approximation inside the glass, and a full enclosure analysis in the gas for surface-to-surface radiation between the glass surface and furnace wall was used. The model includes temperature dependent physical properties. Convective heat transfer was treated by solving the flows in the gas and glass, conjugately. The three-dimensional Navier-Stokes equations and the energy equation were solved within the glass preform and gas simultaneously using the finite element method.

Wall cold-spots at different locations and temperatures were examined and their effects on the furnace temperature were determined. These cold spots cause temperature nonuniformities around the preform circumference and delay the heat up of the preform. Asymmetric glass temperatures on the preform caused by cold-spots located in the upper part of the furnace tended to equilibrate before reaching the end of the furnace. The preform diameter at the furnace exit becomes narrow, thus the circumferential temperature distribution on the fiber becomes more uniform and isothermal. However, although the asymmetric temperature differences were small, the temperature gradients and viscosity changes over the preform cross-sections were rather high. Thus, the glass will flow faster through the hot side of the preform. This may result in a nonuniform consumption of the glass preform and may also cause distortion on the desired form of the symmetric neck-down root shape of the preform. Wall cold-spots must be minimized in temperature and size to prevent their effects on the temperature field and final fiber diameter.
The Role of Heat Transfer Problems in Standard Crystallization Experiments
Authors: Eder Gerhard
Published: March 2022

In most publications dealing with crystallization kinetics also nowadays Avrami’s model from 1939 is used for analyzing experimental data. There have been made many attempts to generalize this isothermal model to arbitrary non-isothermal crystallization processes. The solution of this problem can be found in a work by A.N. Kolmogoroff from 1937. The basic crystallization kinetic quantities in this theory are some crystal growth rate and nucleation rate, which both may depend arbitrarily on time. For analyzing data with such models it is essential to have a good control of the temperature history, since both kinetic quantities are very sensitive with respect to temperature changes. A very popular reason to develop new kinetic models was often the fact, that experimental results could not be described by the classical models. In this paper heat transfer problems are shown to be a decisive source of such deviations.
Estimating the Morphology of Soot Agglomerates by Measuring Their Scattering Matrix Elements
Authors: Manickavasagam S. , Govindan R. , Mengüç M. P.
Published: March 2022

In this study, we introduce a novel approach to identify the structure of soot agglomerates in flames. The idea is based on the use of elliptically-polarized light scattering, which is quite sensitive to the morphology of the scattering particles. First, a numerical procedure is outlined to determine the scattering (Mueller) matrix elements of particles and agglomerates. Results for various fractal-like agglomerates are presented. Following this, an experimental procedure is described to measure the same elements. Then, normalized experimental and numerical results are compared to estimate the fractal morphology of soot agglomerates. The results show that this technique is quite versatile and can be employed effectively to identify the size and structure of soot agglomerates.
Monodisperse Spray Effects on Thermal Explosion in a Gas
Authors: Goldfarb Igor , Goldshtein Vladimir , Kuzmenko Grigory , Greenberg J. Barry
Published: March 2022

The effect of a flammable spray on the thermal explosion in a combustible gas mixture is investigated based on an original physical model. For qualitative analysis of the system an advanced geometric asymptotic technique (integral manifold method) has been used. Possible types of dynamical behavior of the system are classified and parametric regions of their existence are determined analytically. It turns out that there are five main dynamical regimes of the system: slow regimes, conventional fast explosive regimes, thermal explosion with freeze delay and two different types of thermal explosion with delay (the concentration of the combustible gas decreases or increases). Peculiarities of these dynamical regimes are investigated and their dependence on physical system parameters are analyzed. Upper and lower bound estimates for the delay time are derived analitically and compared with results of numerical simulations. The comparison demonstrates satisfactory agreement.
Microscales of Natural Convection
Authors: Arpacı Vedat S.
Published: March 2022

A universal dimensionless number, ΠN∼NN1+Pr-1 ,Pr being the usual Prandtl number and NN the limit of ΠN for Pr → ∞, is introduced for all natural convection processes. For NN=Ra ,Ra being the usual Rayleigh number, ΠN describes buoyancy-driven natural convection. For NN=Ma ,Ma being the usual Marangoni number, ΠN describes thermocapillary-driven natural convection. For NN=TaPr ,Ta being the usual Taylor number, ΠN describes centrifugally-driven natural convection.

In terms of ΠN, a thermal Kolmogorov scale relative to an integral scale, ηθℓ∼ΠN-1/3 is introduced for natural convection including buoyancy, thermocapillary and centrifugally-driven flows. Heat transfer associated with these flows is modeled byNu∼ΠN1/3 ,Nu being the usual Nusselt number. A variety of turbulent natural convection phenomena are shown correlating the model.
Effects of Orifice Geometry on the Heat Transfer Distribution for Impinging Jet Array
Authors: Arjocu Simona C. , Liburdy James A. , Ferland Michele M.
Published: March 2022

The recent technological advances in the areas of gas turbine blades, tempered metals and in particular electronic components, require a rapid rate of removal of heat. With an array of impinging jets a large surface involved in the cooling or heating process can be covered using relatively small flow work, or driving pressure. A properly spaced and configured impinging jet array produces a high heat transfer rate. The present study details the role of impinging jets in the heat transport phenomena. The average and local heat transfer coefficient distribution is mapped using thermochromic liquid crystals for three equal flow area jet orifice geometries in a 3-by-3 submerged impinging water jet square array. The hydrodynamic conditions are established for low Reynolds number values, from 800 to 1500, and impingement distances of 1, 2 and 4 jet hydraulic diameters. The constant temperature jets impinged normally on a constant heat flux surface and liquid crystal images were recorded under thermal and hydrodynamic steady state conditions. The results indicate that there is a Reynolds number dependence of the degree of heat transfer enhancement for different shaped jet orifices. The heat transfer within the central unit cell varies with impingement distance and jet geometry. Two types of heat transfer coefficient spatial variation have been identified: one deals with large scale jet flow characteristics and the other with smaller scale effects caused by flow turbulence. Details are presented illustrating the nonuniformity of the heat transfer for the various geometries.
A Study of the Flow Field and Convective Heat Transfer in a Model Rotor-Stator Cavity
Authors: Roy Ramendra P. , Agarwal Vivek , Devasenathipathy Shankar , He Junru , Meier Lars , Kim Yong W. , Howe Jeff , Ho Ko-Sun
Published: March 2022

Experiments and computations are being carried out with the objective of understanding the turbulent flow field and convective heat transfer in gas turbine disk cavities. An experimental rig which features a configuration of rotor and stator disks simpler than in actual gas turbines but retains the important features of stator vanes, rotor blades, and realistic rim seals on the disks has been constructed for the experiments. The commercial CFD code FLUENT/UNS is used for the computations.

We report measurements, in experiments with mainstream and secondary air flows, of the convective heat transfer coefficient and cooling effectiveness distributions on the rotor disk surface. Also reported are the radial distribution of the time-mean static pressure at the stator disk and the circumferential distribution of the same in the mainstream gas passage. Implications of the cooling effectiveness and static pressure distributions vis-á-vis the ingestion of mainstream gas into the disk cavity are discussed briefly. Computational results are presented and compared with measurements in some cases.
Non-Boussinesq Convection in a Tall Cavity Near the Codimension-2 Point
Authors: Suslov S. A. , Paolucci S.
Published: March 2022

By means of weakly nonlinear analysis, we investigate the interaction between two physically distinct instability modes arising in the non-Boussinesq convection flow in a differentially heated tall vertical air-filled cavity. It is shown that in the neighborhood of the codimention-2 point the primary parallel flow becomes unstable due to both shear and buoyant disturbances. The flow dynamics is modeled by a system of the two coupled Landau equations. Different possible instability wave patterns are found, and the parameter regions of their existence are discussed. Energy analysis of the interacting instability modes is also presented.
A Stream Function Finite Differences Formulation for Two Dimensional Incompressible Flows
Authors: Bubnovich Valeri I. , Moraga Nelson O.
Published: March 2022

A new implicit algorithm to solve the full Navier Stokes equations for two dimensional unsteady incompressible flows that only makes use of the stream function, without the explicit calculation of the vorticity, is presented. The mathematical model discretized in finite differences, according to the ADI method, results in a system of two algebraic equations involving 11 nodes in each equation. By making an original hyphotesis, a reduction to equations with five nodes allows to obtain the numerical solution via the use of a pentadiagonal matrix algorithm PDMA. An iterative cycle has been implemented to verify the quality of the proposed hyphotesis ant to asses its accuracy and speed of convergence. Numerical results are presented for two classical fluid mechanics problems: induced laminar flow in a square cavity with Re = 100, 400, 1000 and natural convection inside a square cavity for cases where Ra = 1000, 10000 and Pr = 0.1; 1, 10.
The Design and Analysis of Compliant MEMS Using the Pseudo-Rigid-Body Model
Authors: Jensen Brian D. , Howell Larry L. , Gunyan Daniel B. , Salmon Linton G.
Published: March 2022

Because of the difficulty of fabricating rigid-body joints and assembling parts in micro-electro-mechanical systems (MEMS), compliant mechanisms offer several advantages to MEMS designers. However, motion of compliant segments generally involves large, non-linear deflections which are difficult to predict using linear beam theory. This paper discusses MEMS design using the pseudo-rigid-body model. This model has been developed to permit simplified prediction of nonlinear deflections in compliant mechanisms, allowing traditional mechanism theory to be used in design. The design process is validated by testing MEMS structures designed using this model. The model successfully predicted the motion of the compliant MEMS, even for very large deflection paths. The mechanisms designed and tested achieved larger deflections and more complex motion than was previously possible.
Impact of Phonon Dispersion Upon the Size Effect on Thermal Conduction Along Thin Semiconductor Films
Authors: Ju Y. Sungtaek , Goodson Kenneth E.
Published: March 2022

The thermal conductivities of thin crystalline semiconductor films in novel electrical and optical devices can differ from bulk values due to the size effect on lattice thermal conductivity, which is caused by phonon-boundary scattering. For many semiconductors at or above room temperature, the size effect is strongly influenced by the highly dispersive nature of their phonon spectra and the varying contribution of each phonon branch to heat conduction. The present study reviews existing thermal conductivity models for bulk semiconductor samples and examines the impact of the phonon dispersion on the size effect. Based on the observed strong dependence of the size effect on the phonon branch contributions, we demonstrate that the investigation of thin-film thermal conductivity at high temperatures can help the theoretical understanding of lattice thermal conduction. For silicon thin films studied here better agreement between the predicted in-plane thermal conductivity and the existing experimental data is achieved by assuming that longitudinal phonons are the dominant heat carriers. The practically-relevant problem of phonon scattering at the interface between crystalline silicon and amorphous silicon dioxide layers is discussed.
Increasing the Exergy Storage Capacity of Thermal Storages Using Stratification
Authors: Rosen M. A. , Tang R.
Published: March 2022

The increase in exergy storage capacity that is attained in thermal storages through stratification is assessed. A design-oriented temperature distribution model for vertically stratified thermal storages that facilitates the evaluation of storage energy and exergy contents is utilized. The paper is directed towards demonstrating the thermodynamic benefits achieved through stratification, and increasing the utilization of exergy-based performance measures for stratified thermal storages. A wide range of realistic storage-fluid temperature profiles is considered, and for each the relative increase in exergy content of the stratified storage compared to the same storage when it is fully mixed is evaluated. The results indicate that, for all temperature profiles considered, the exergy storage capacity of a thermal storage increases when it is stratified, and increases as the degree of stratification, as represented through greater and sharper spatial temperature variations, increases. Furthermore, the percentage increase in exergy capacity is greatest for storages at temperatures near to the environment temperature, and decreases as the mean storage temperature diverges from the environment temperature (to either higher or lower temperatures). It is concluded that (i) the use of stratification in thermal storage designs should be considered as it increases the exergy storage capacity of a thermal storage, and (ii) exergy analysis should be applied in the analysis and comparison of stratified thermal storage systems.
New Humidification Concept for Evaporative Gas Turbine Cycles Applied to a Modern Aeroderivative Gas Turbine
Authors: Aagren Niklas D. , Cavani Adrin , Westermark Mats O.
Published: March 2022

A new humidification concept in evaporative gas turbine cycles is presented. This involves a humidfication column with multiple sections of counter-current humidification with different water flows in each section. The advantages of multiple sections are analyzed in combination with part-flow humidification, where less than 50% of the compressed air from the air compressor is led through the humidification column and the rest is passed on directly to the recuperator. The part flow humidification is a concept that noticeably reduces mass and heat transfer equipment costs in the EvGT cycle. It is shown that, for a part flow configuration, a more efficient cycle can be attained than in a system with customary single-section humidification.

In this paper an EvGT system is modeled in the GATE/CYCLE gas turbine simulation program. The simulations are based on the modem aeroderivative gas turbine Rolls Royce Trent in non-intercooled mode. The results include performance data as well as dimensions and design considerations of the humidification column and the heat exchangers.
The Effect of Thermoelectric Cooler Mounting Orientation on Cooling Efficiency
Authors: Welling Thomas E. , Bell Cheryl A. , Al-Ubaidi Muthar
Published: March 2022

This paper documents an experiment designed to evaluate the effect of heat sink location on cooling system efficiency. Increasing cost and regulation of CFCs, as well as environmental concerns, have resulted in the widespread use of alternative cooling systems, including Thermoelectric Coolers (TECs). These small, solid state heat pumps require heat sinks to increase their effective surface area. Their physical geometry precludes the use of more efficient flow-through heat exchangers. This fact encourages designs in which the cooling process occurs in a duct, raising the question, “How does the position of the heat sinks in a cooling duct affect system efficiency?”

This experiment documents a difference in cooling efficiency between identical sets of four thermoelectrically cooled heat sinks mounted serially in a duct and four similarly cooled heat sinks mounted peripherally in the duct.

This experiment proves that heat sink location in duct cooling applications should be optimized to increase system efficiency and reduce operating costs.
Absorption Heat Pump Performance Improvement Through Ground Coupling
Authors: Garimella Srinivas
Published: March 2022

The present study investigates the improvement in the performance of an absorption heat pump for residential space-conditioning due to the use of the ground as the heat source in the heating mode and the heat sink in the cooling mode. A baseline air-coupled single-effect ammonia-water heat pump is first designed to deliver 10.55 kW (36,000 Btu/hr) of cooling load at the ARI rating conditions. Particular attention is paid to incorporating many realistic details of an operating system such as fuel combustion efficiencies of the burner, non-equilibrium conditions, and moist air processes in the air-coupled heat exchangers. A range of parametric studies is also conducted to investigate the variation in performance of this system with ambient conditions in the heating and cooling modes. The same system is then analyzed in a ground-coupled configuration. The instantaneous COP for the ground-coupled system is compared with the COP of the air-coupled system as a function of the time of the year and the corresponding variations in ambient and ground temperatures using thirty-year average climate data for various locations from the National Weather Service. Improvements in COP of up to twenty percent over the air-coupled system values (cooling mode COP of 0.495 at 35°C (95°F) and heating mode COP of 1.20 at 8.33°C (47°F)) are demonstrated in diverse geographic locations with widely varying heating and cooling loads. These improvements indicate that an efficient ground-coupled heat pump could be developed for residential space-conditioning applications using simple thermodynamic cycles and existing technology for the heat and mass exchange components.
Nondestructive Evaluation of Graphite/Aluminum Composites Using Acousto-Ultrasonics
Authors: Quattlebaum Gene J. , Raju P. K.
Published: March 2022

Acousto-ultrasonic (AU) is a nondestructive testing technique for evaluating composites and composite like materials. The name is based on the fact that advantages of the acoustic emission and ultrasonic testing techniques are combined in this NDE technique. In previous research, AU has been used to evaluate carbon/carbon and GFRP composite materials. The work reported in this paper uses Au to examine the adhesive bond strength of lap-jointed graphite/aluminum composite structures. The Stress Wave Factor (SWF), an AU parameter, was used to quantify the strengths of the two types of adhesives used in this research. Also, AU was used to identify delaminations present in the bond area. AU was used to see if the transverse tensile strength of these composites could be determined and to see if this NDE technique was sensitive to progressive damage. The results indicate that AU can be used to effectively identify the bond strength, the transverse tensile strength, and progression of damage in transverse specimens.
Boundary Element Analysis of Mufflers With an Improved Four-Pole Method
Authors: Wu T. W. , Zhang P. , Cheng C. Y. R.
Published: March 2022

When a muffler is modeled by the boundary element method (BEM), the transmission loss (TL) can be evaluated by either the conventional four-pole method or the recently developed three-point method. The three-point method produces only the TL, and nothing else. On the other hand, the four-pole method has the advantage of retaining the transfer matrix of the muffler, which contains important parameters when the muffler is connected to another muffler or other components in the exhaust system. However, the major drawback of the conventional four-pole method is that it requires two separate boundary element runs due to the two different boundary conditions imposed on the outlet boundary. Therefore, it can take twice as much of the CPU time as the more efficient three-point method. In this paper, an improved four-pole method is introduced. This improved four-pole method does not require solving the boundary element matrix twice. Therefore, it is as efficient as the three-point method and it also retains the important four-pole transfer matrix. The boundary element analysis is done by the direct mixed-body BEM. Two different transfer impedance formulas for perforated tubes are used. Numerical results are compared to experimental data.
Flexible Monitoring Strategies for Milling Operations
Authors: Klocke Fritz , Reuber Martin , Rehse Michael
Published: March 2022

Frequently changing machining operations are a characteristic feature in one-off and small batch size production and require a high degree of flexibility in the production processes and facilities. Process monitoring systems applied in such a production environment have to be able to supply reliable process information under varying machining conditions. Therefore, generic and flexible monitoring solutions are needed, adaptable to the requirements of specific machining applications with minimum efforts. In this paper the requirements for such generic and flexible monitoring approaches are critically discussed. In the second part, monitoring strategies for a process state analysis in face milling, end milling and drilling operations is described, adaptable to varying machining conditions by combining several sensing and evaluation methods.
Prediction of Thermal Deformation of Machine Tool With Strain Sensor
Authors: Moriwaki Toshimichi , Shamoto Eiji , Kawano Masahiro
Published: March 2022

A new approach is presented to estimate the thermal deformation of machine tool, which is generally defined by the relative displacement between the tool and the workpiece. Unlike the conventional approaches based on measurement of the temperature distribution with thermocouples, the new approach is based on measurement of strain distribution, which is considered to give more accurate information about the deformation. A new sensor is developed to measure the true strain including the thermal influence, since it can not be measured by the conventional strain gauge sensors. The developed sensor is applied to estimation of the thermal deformation of a machining center. Fundamental properties of the sensor and the estimated results of thermal deformation are reported.
Modeling Texture of Peripheral-Milled Surfaces Using a Neural Network and Fractal Method With Evidence of Chaos
Authors: Stark G. A. , Moon K. S.
Published: March 2022

Modeling texture of milled surfaces using analytic methods requires explicit knowledge of a large number of variables some of which change during machining. These include dynamically changing tool runout, deflection, work-piece material properties, displacement of the workpiece within its fixture and others. Due to the complexity of all factors combined, an alternative approach is presented utilizing the ability of neural networks and fractals to implicitly account for these combined conditions. In the initial model, predicted surface points are first connected using splines to reconstruct 3D surface maps. Results are presented over varying several cutting parameters. Then, replacing splines, an improved fractal method is presented that determines fractal characteristics of milled surfaces to reconstruct more representative surface maps on a small scale. The fractal character of self-similarity within surfaces as manifested by the fractal dimension provides evidence of chaos in milling.
Feasible Machining Strip Evaluation for 5-Axis CNC Die and Mold Machining
Authors: Lee Yuan-Shin , Ji Hong
Published: March 2022

This research is focused on the investigation of robust surface interrogation tools which can support the planning and programming of 5-axis die/mold surface machining. Surface curvature information is evaluated to determine optimal tool orientation for 5-axis machining. A method for calculating machining strip width is proposed for 5-axis cutter path generation. This paper is focused on the development of computational geometry techniques and their application to design, analysis, and manufacturing automation. The proposed planning and programming methodology consists of two steps: 1) machining strip width evaluation, and 2) optimum tool orientation for 5-axis machining. This proposed research can be used to improve the quality of 5-axis die/mold machining.
Residual Stresses and Workpiece Deformation due to Polishing and Plating of Computer Hard Disk Substrates
Authors: Klamecki Barney E.
Published: March 2022

Residual stress distributions due to plating and polishing were determined for nickel-phosphorus plated aluminum alloy disks. Knowledge of these stresses provides insight into the material deformation and removal processes, information as to the effects of processing conditions on residual stress magnitude and can also serve as a basis for development of models of material deformation and removal in polishing. Measured disk shape data was fitted to an analytical solution for plate displacement due to bending moments, and residual stresses were calculated. Plating and polishing residual stresses were separated. Polishing residual stress is compressive indicating differential plastic deformation between the surface and interior regions of the workpiece. Residual stresses produced in polishing operations in which process motions were constrained so that polishing was unidirectional were measured. The results show large differences between amounts of deformation in the polishing direction and the direction perpendicular to it.
Development of Force-Control Model for Edge-Deburring With Filamentary Brush
Authors: Chen Lienjing , Stango Robert J. , Cariapa Vikram
Published: March 2022

In recent years, edge finishing with filamentary brushes has received much attention within the applied research and manufacturing engineering communities. This interest may be attributed, in part, to the ease with which brushing tools can be introduced into an automated machining environment. That is, such tools exert relatively small machining forces, remove material incrementally, and minimize the risk of generating abrupt, unstable forces that can lead to tool/workpart damage during the finishing operation. Although brushes have been successfully used in automated finishing applications, much uncertainty remains regarding the proper use of brushes for removal of edge burrs. Consequently, the implementation of automated brush deburring operations is often accompanied by costly trial-and-error experimentation, and in many cases, is met with only marginal success.

This paper is concerned with the development of a force-control model for edge deburring with filamentary brushes. The model is based upon experimentally obtained “master curves”; that is, material removal data that corresponds to the actual machining performance of the brush/workpart system during the incremental burr removal process. Such master curves are generated by machining specially prepared edge projections having a geometry similar to flash that is produced along the edges of cast components. This information is used in conjunction with the on-line brush machining force to compute the brush feed rate that ensures complete removal of the edge burr. Example problems are reported for two cases, namely, the removal of edge flash having (i) unknown, constant height, and (ii) unknown variable height. The results indicate that the present force-control model provides straight forward approach for computing brush feed rates that lead to complete removal of edge burrs, and suggests that implementation can be carried out without the use of sophisticated sensing apparatus or complex control strategies.
Automated Scarfing and Surface Finishing Apparatus for Curved Composite Structures
Authors: Erlbacher Edwin A. , Godwin Lester E.
Published: March 2022

This paper describes the justification and design of a Scarfing Tool for Automated Repair of Composites (STARC) system. The repair of aircraft composites is currently a manual process that subjects workers to adverse working conditions often leading to costly mistakes and poor repair quality. Commercial robots are finishing many types of materials in many industries, but none are performing scarfing repairs. A lightweight, portable manipulator is needed to automate the scarfing process.

A pneumatic, parallel link Stewart Platform manipulator will provide necessary grinding trajectories. The primary benefits of Stewart Platform manipulators is their high stiffness to weight ratio and their simple modular design. For the STARC, a commercially available Adjustable Force Device (AFD) would be mounted on the underside of the movable platform. In this configuration, the platform would meet all the major design goals of providing a substantial work envelope, the required six degrees-of-freedom, and relatively light weight portability without sacrificing rigidity.
CBGA Solder Fillet Shape Prediction and Design Optimization
Authors: Li Y. , Mahajan R. L.
Published: March 2022

This paper presents a mathematical analysis to predict the solder fillet shape for ceramic ball grid array joints. Unlike the past analyses, the solder fillet is not assumed to be linear. The solder fillets on both the module and the card side are represented as arcs, and the solder shape is calculated from an analysis that incorporates the major factors affecting the solder fillet, including the solder volume, the pad size, the solder ball size, the wetting angle between the solder and the solder ball, and the gap between the solder ball and the pad. Three of these parameters (the card pad size, the solder ball size and the card-side eutectic solder volume) were selected for investigation of their effect on the reliability of solder joints. To this end, a central composite design of experiment was set up, and the mathematical analysis and finite element methods were used to predict the fatigue life corresponding to each of the design settings in the design array. The results of analyzing the data reveal that the solder volume, the solder ball size and their interaction are statistically significant; the interaction between the pad size and the solder volume is also significant but to a less degree; the pad size and the interaction between the pad size and the solder ball size are not significant. In addition, a response surface model was built to find the optimum settings for maximum reliability. Finally, inaccuracy due to the linear solder fillet assumption is assessed in light of the present analysis.
Direct Observations of the Chip-Tool Interface in Machining
Authors: Madhavan V. , Chandrasekar S. , Farris T. N.
Published: March 2022

An experimental study has been made of the chip-tool interface and its evolution in the low speed cutting of metals. Specially prepared transparent glass and sapphire tools have been used to cut commercially pure metals such as lead, aluminium and copper. The chip-tool interface has been observed in situ using optical microscopy and recorded on film and video tape. By observing the motion of inhomogeneities in the chip, and pro-filometry of the chip and tool surfaces, it has been established that there is intimate sliding contact between the chip and the tool at and near the cutting edge. Farther away from the cutting edge and close to the end of the chip-tool contact, metal transfer and sticking are observed between the chip and tool surfaces. It has been shown that metal deposition on the tool rake surface initially occurs near the end of contact and progressively extends outward and away from the cutting edge as the length of contact increases. The sticking and sliding zones are unchanged when these pure metals are machined with tungsten carbide tools.
Ultrasonic Machining: 1907 to Present
Authors: Wang Hsueh-Ming S. , Plebani Louis , Sathyanarayanan G.
Published: March 2022

The term Ultrasonic machining (USM) can be applied to any machining process which uses ultrasonic energy to erode brittle materials. The process has been successfully used to assist deburring, polishing, lapping, grinding, and drilling operations. Hardened steel, glass, ruby, and ceramics have been finish machined with a control of geometry and surface roughness under one micron. Applications have included optical products, dies and molds, structural ceramics and IC chips. The main topics of this article include machine tool renovation, work material application, accuracy of workpiece tolerance, the changing market and past research. Original developments in the Soviet Union, Germany, England, Japan, and the USA are surveyed. Possible areas of future research are identified.
Machinability of Graphitic Silicon Carbide Aluminum Metal Matrix Composite GrA-Ni™
Authors: Songmene V. , Stephenson T. F. , Warner A. E. M.
Published: March 2022

Metal-Matrix Composites (MMC) are being developed for high wear resistance applications. A new MMC, a graphitic aluminum metal matrix composite consisting of an aluminum matrix reinforced with SiC particles and nickel-coated graphite particles, GrA-Ni™, has been developed by INCO Limited. The addition of nickel-coated graphite to SiC particulate reinforced aluminum plays a similar role to flake graphite in grey cast iron. However, like other MMCs, this composite is demanding in terms of requirements for cutting conditions and cutting tool materials.

This paper assesses the machining data for this new composite, in regards to tool life, surface finish and cutting forces. The tests included milling, turning, and drilling conducted with carbide and diamond tools. The test results showed that GrA-Ni™ with 10 vol% SiC – 5 vol% Gr, is easier to machine than existing aluminum composites reinforced with SiC particles, such as 20 vol% SiC reinforced aluminum composite.
A Study on the Dynamics of Toolholders
Authors: Jouraij Joseph , Du Ruxu , Yang Juhchin A.
Published: March 2022

There are two types of common toolholder defects: toolholder run-out (eccentric error) and toolholder fretting. Toolholder run-out is caused by either manufacturing error or assembly error and can be easily measured and corrected. On the other hand, toolholder fretting may be caused by the relative vibration between the machine spindle and the toolholder. It is much less understood and an effective correction method remains an engineering challenge. In this paper, the dynamics of the toolholders are investigated by means of mathematical modeling, finite element simulation, as well as modal analysis. The investigations consistently indicate that toolholder fretting is caused by high frequency vibration of the toolholder and it may be corrected by changing the toolholder design (e.g., extending the tool overhang and/or increasing the diameter of the toolholder).
Formation and Breaking of Side-Curl Dominated Short-Spiral Chips
Authors: Li Zhenjia , Qu Guimin , Xu Yihong , Rong Yiming (Kevin)
Published: March 2022

In this paper, the formation of side-curl dominated chips is first discussed, as well as the side-curl radius. The chip width and thickness in 3-D side-surl is studied for the side-curl radius prediction. The formation and and breaking of side-curled short-spiral chips in metal cutting is particularly studied. It is found that the collision of the swinging chip and the unmachined workpiece surface or tool holder flank surface plays an important role in chip breaking. Based on a force analysis, a chip breaking criterion is established and the chip length is estimated. The relationship of chip breaking length and cutting parameters is derived and verified by experiment results, which can be used in chip length prediction.
Theoretical Examination of a New Calibration Method for Multi-Axis Machines
Authors: Wang Y. , Moon K. S. , Sutherland J. W.
Published: March 2022

A new method of calibration of coordinate measuring machines (CMMs) and multi-axis machine tools using a 2-D ball array is proposed in this paper. Combined with the use of a 3-D capacitive probe or a magnetic socket, this method can improve the efficiency of calibration greatly. A new kind of artifact called a 2-D ball array is proposed. The 2-D ball array combines the advantages of ball plate and 1-D ball array. Using the 2-D ball array, it is convenient to perform calibration and it is cost effective. Two methods are put forward for using a 2-D ball array in the calibration of the machines. The general method needs the 2-D ball array to be measured at only 4 different positions in the machine working zone, and the 21 parametric errors of the machine can be obtained. The second method is based on the error separation theory. By this method, information of the artifact can be fully utilized without the need to accurately a priori calibrate the artifact. These proposed methods can be used in the calibration and error compensation of CMMs and machine tools.
Design of Extruded Aluminum Space Frame Front End Structures for Crash Energy Management: Part I
Authors: Mahmood Hikmat F. , Baccouche Mohamed R. , Barthelemy Bruno
Published: March 2022

The present crash energy management design work is comprised of two parts. Part I, this current paper, discusses the CAE analysis and testing results of extruded aluminum components for a front end structure of a space frame vehicle. The components consist of front and back-up rails with various rail reinforcement and triggering mechanisms. Rail and reinforcement members are manufactured using aluminum alloys extruded through a closed hat and aluminum sheet shaped in an open hat cross-section respectively. Aluminum alloys series 5xxx and 6xxx were used with the reinforcement while only 6xxx series extruded aluminum alloy was used with the front and back-up main rails. Triggering was applied to reinforcements in various configurations. Further details on the reinforcement and triggering are discussed throughout the paper. CAE models for the front end components were built and analysis was performed to determine the mean crush load, energy absorbing capability, mode of collapse, and folding pattern of each component. Component testing was conducted to verify the CAE prediction and to provide additional comparative design data as to the stability, mode of collapse, number of folds, folding pattern, stack-up, etc.

Part II, a second paper to be published at a later date, reviews briefly the components testing results and presents a detailed discussion of the CAE modeling and models results for the full front end of the extruded aluminum space frame structure.
Recurrent Artificial Neural Networks for Crashworthiness Analysis
Authors: Omar Tarek A. , Bedewi Nabih E. , Eskandarian Azim
Published: March 2022

The initial velocity and structural characteristics of any vehicle are the main factors affecting the vehicle response in case of frontal Impact. Finite Element (FE) simulations are essential tools for crashworthiness analysis, however, the FE models are getting bigger which increases the simulation time and cost. An advanced recurrent Artificial Neural Network (ANN) is used to store the nonlinear dynamic characteristics of the vehicle structure. Therefore, hundreds of impact scenarios can be performed quickly with much less cost by using the trained networks. The equation of motion of the dynamic system was used to define the inputs and outputs of the ANN. The back-propagation learning rule was used to adjust the connecting weights and biases of the developed Network. To include the dynamics of the system, the delayed acceleration was fed back as an input to the ANN together with the velocity and displacement.

A Finite Element (FE) model for a simple box beam with rigid mass attached to it was developed to represent a general crushable object. The simulation results were performed by impacting this model into a rigid wall with different initial velocities. The displacement, velocity and acceleration curves obtained from the simulation — for the C.G. of the moving mass — were used to train the ANN. After a successful training phase, the ANN was tested by predicting a new acceleration curve. The points of the acceleration curve were predicted sequentially since only one point of the curve is predicted through one cycle of the NN operation. The predicted acceleration curve showed a good correlation with the actual curve obtained from the simulation. During the recall phase, the predicted acceleration of a new state was integrated twice to obtain the velocity and displacement by using a second order integration scheme. Then, the displacement, velocity and acceleration of this new state were fed to the ANN to predict the next state acceleration, and so forth.

The results indicated that the recurrent ANN can accurately capture the frontal crash characteristics of any impacting structure, and predict the crash performance of the same structure for any other crash scenario within the training limits. The current paper considered only the front impact, however, an offset and oblique impact scenarios will be included in further research.
Finite Element Vehicle Impact Simulation for Highway Safety Applications
Authors: Tabiei Ala , Wu Jin
Published: March 2022

The subject of this investigation is the development of an accurate simulation of a truck impacting a G4 (1S) strong-post w-beam guardrail. The objective of the study is to provide a check and an additional measures of reliance of the results from the crash tests and identify critical roadside components for a crashworthy design. Identification of critical parameters will be used for design improvement of the G4 (1S) system for truck roll-over.
A Dynamic Finite Element Simulation of the Impact of Motorcycle Helmets
Authors: Scott De-Shin Liu , Fan Chih-Ming , Lee Maw-Chang , Yen Chung-Yet
Published: March 2022

The fact that helmets can prevent head injury is well-established. This paper describes the use of a dynamic, inelastic and large deformation finite element code LS-DYNA3D to simulate the impact response of motorcycle helmets. In order to verify the accuracy of the model, the simulation results of helmet drop on steel anvils were compared with experiments. The numerical predicted results matched experimental data very well. We then study the effects of ventilation holes. EPS shell with ventilation holes absorbed shock better than intact one when impacting the flat anvil, but not when impacting the hemi-sherical anvil. Next, a full FEM model which contain Hybrid III head, neck, and chest has been developed and couple with helmet FEM model for analyzing the kinematics of the neck motion and the associated dynamic transient response of the head subjected to various impact angles. The critical characteristics such as head C.G. acceleration, section forces and moments at the head-neck section and neck-chest section are investigated for each cases. Thus we have established a reliable 3D finite element model which can help us to better design the helmet.
Transient Thermal Analysis of Outdoor Electronic Equipment
Authors: Yeh L. T.
Published: March 2022

An outdoor electronic equipment is under consideration. In order to attain the desired system performance and reliability, the junction temperature of all electronic components and the base plate temperature of the power supply under the worst environmental conditions must be kept below 105°C and 85°C, respectively.

A system level transient analysis is performed to determine the temperatures of the internal air and the power supplies which are mounted to the internal structures of the system. The transient is caused by the daily cycle of ambient temperature and solar flux. The internal air temperature and the base plate temperature of the power supply are computed for a 24-hour period. The above thermal design limits are met with the computed internal air temperatures and flow rates.
On the Creation of Stagnation Points in a Rotating Flow
Authors: Mullin T. , Tavener S. J. , Cliffe K. A.
Published: March 2022

We report the results of a numerical study of the creation of stagnation points in a rotating cylinder of fluid where both end-walls are rotated. Good agreement is found with previous results where the stagnation points are formed on the core of the primary columnar vortex. Novel phenomena have been uncovered at small aspect ratios where stagnation occurs off-axis directly and the secondary vortex which is created forms a toroid. The case is then considered of a small cylinder placed along the centre of the flow and despite the qualitatively different boundary condition, the phenomena are found to be robust.