bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanism Design for Global Isotropy With Applications to Haptic Interfaces
Authors: Stocco Leo J. , Salcudean Septimiu E. , Sassani Farrokh
Published: March 2022

A new global isotropy index (GII) is proposed to quantify the configuration independent isotropy of a robot’s Jacobian or mass matrix. The matrix is scaled to homogenize the physical units, to tailor it to the demands of the application and to choose optimum actuator parameters. A new discrete global optimization algorithm is also proposed to optimize the GII without placing any conditions on the objective function. The algorithm is used to establish design guidelines and a globally optimum architecture for a planar haptic interface from both a kinematic and dynamic perspective and to compare three robots for use as a 5-DOF haptic pen. The algorithm demonstrates consistent effort reductions of up to six orders of magnitude over global searching with low sensitivity to initial conditions.
Automatic Structure and Parameter Training Methods for Modeling of Mechanical System by Recurrent Neural Networks
Authors: Li C. James , Huang T. Y.
Published: March 2022

Automatic nonlinear-system identification is very useful for various disciplines including, e.g., automatic control, mechanical diagnostics, and financial market prediction. This paper describes a fully automatic structural and weight learning method for recurrent neural networks (RNN). The basic idea is training with residuals, i.e., a single hidden neuron RNN is trained to track the residuals of an existing network before it is augmented to the existing network to form a larger and better network. The network continues to grow until either a desired level of accuracy or a preset maximal number of neurons is reached. The method requires neither guess of initial weight values nor the number of neurons in the hidden layer from users. This new structural and weight learning algorithm is used to find RNN models for a two-degree-of-freedom planar robot, a Van der Pol oscillator and a Mackey-Glass equation using their simulated responses to excitations. In addition, a RNN model is obtained for a real robot using its input and output measurements. The algorithm is effective in all four cases and RNN models were shown to be superior to linear models and hybrid models wherever the comparison was made.
Fuzzy Logic Control of Material Forming Process
Authors: Lieh Junghsen , Li Wei Jie
Published: March 2022

Adaptive controllers with self-adjustment capabilities possess many advantages over conventional methods. An adaptive fuzzy controller may be implemented either in a direct form or in an indirect form, and it is generally referred to as a self-organizing controller. One advantage of fuzzy controllers is their simple computation requirements in comparison with more algorithmic-based controllers.

A metal forming process is a good candidate for the implementation of fuzzy logic rules because of its nonlinear and stochastic properties. In this paper, a prototype electromechanical forming machine was developed and tested. The system includes an optical sensor, an AC induction motor, a servo controller, a forming mechanism, and a microprocessor. The measured state variable is processed by the CPU with a fuzzy logic algorithm. The controller utilizes primary and secondary errors between the actual response and desired output to conduct rule reasoning. Results from testing are presented.
Learning by Highly Autonomous Sensors
Authors: Figueroa Fernando , Mahajan Ajay
Published: March 2022

A formal theory for the development of a generic model of an autonomous sensor is described. This model can be viewed as addressing a somewhat specific area of autonomous agent models. Perhaps the most intriguing aspect of this work is that it concentrates on the sensor itself whereas autonomous agents assume that the sensory input is complete and accurate to the degree that it needs to be. Building intelligent systems in engineering implies embedding the capabilities of the system operator in the model. These capabilities are not simply rules and facts, but also reasoning and decision making methodologies. So we present the notion of considering a sensor as an autonomous agent itself and call it highly autonomous, since no system can be completely autonomous. A highly autonomous sensor (HAS) not only interprets the acquired data in accordance with an embedded expert system knowledge base, but is also capable of learning and thereby improving its performance over time. This paper will concentrate on the learning aspects of the HAS model. The model is generic and can be used to instantiate any sensor as a HAS.
Image Processing for Pose Recognition Using a Neural Network
Authors: Murray William R. , Billingsley Daniel A.
Published: March 2022

The research reported herein is an empirical investigation of the capability of an artificial neural network to determine part pose by processing image data from the silhouette of a back-lit part. The chief potential benefit of this new approach is simplicity of training, which is important for flexible automated parts feeders. While this research is of general interest to the designers and users of vision-based, flexible parts feeders, these experiments focused on a flexible tray loader that has been developed at the University of Washington. Pertinent aspects of the hardware and software for that system are presented. A relatively simple neural network is proposed and evaluated experimentally. For five of the six challenging parts considered, the network performed flawlessly. The difficulties encountered with the sixth part have been identified, and further work exploring solutions to the problem are underway.
Thresholding on Bone Density for the Identification of Ligament Insertion Sites of the Human Knee
Authors: Morgan T. G. , Murphy M. C.
Published: March 2022

Knee ligament attachment coordinates are essential in developing a model of the passive constraints of the joint as well as evaluating ligament behavior. Several methods for making measurements of the ligament attachment sites have been reported. One proposed method asserted that high bone density can be used to locate ligament insertion sites. In order to examine if thresholding of bone density can be used to identify ligament insertion sites, CT scans of the femur and tibia-fibula of a cadaver were taken with and without the ligament attachment sites marked. Scans were viewed with a computer program to see if a recognizable and geometrically consistent distribution of higher bone density existed near the ligament insertion sites. The results show that for regions of higher bone density to be used to identify ligament insertion sites, different threshold values for each ligament need to be used, different threshold values for different points along the femur need to be used, and it is sometimes necessary to know the approximate location of the ligament insertion site to locate a region of higher bone density near the insertion site.
Sliding Mode Control of Spatial Mechanical Systems Decoupling Translation and Rotation
Authors: Goeree Barry B. , Fasse Ernest D. , Tiernego Martin J. L. , Broenink Jan F.
Published: March 2022

This paper looks at the robust trajectory control of spatial mechanical systems using sliding mode techniques. Two distinctions of the proposed method from reported methods are: (1) The measure of altitudinal error used is intrinsically defined, Euclidean-geometric, and intuitive. From Euler’s theorem it follows that given a desired and actual attitude of a rigid body there exists an axis and angle of rotation relating the two attitudes. This defines a relative rotation vector, which is used as an intrinsically defined, intuitive measure of error. Reported methods use algebraic differences of entities such as generalized coordinates representing attitude. While functionally correlated to attitudinal error, these measures are not intrinsically defined. (2) A novel, dynamically nonlinear sliding function is used that results in a simple control law. The parameters of this function are dynamically and geometrically intuitive. Simulation results are given for a spacecraft tracking a complex desired trajectory.
Dynamic Scheduling of Internal Exhaust Gas Recirculation Systems
Authors: Stefanopoulou Anna G. , Kolmanovsky Ilya
Published: March 2022

In this paper we analyze the nonlinear dynamic behavior of an internal exhaust gas recirculation system based on the mean-value model of an experimental engine equipped with a camshaft phaser. We develop a dynamic camshaft timing schedule that regulates the internal exhaust gas recirculation system while maintaining transient engine torque response similar to an engine with zero exhaust gas recirculation. The dynamic schedule consists of a steady-state map of the camshaft timing for optimum exhaust gas recirculation based on throttle position and engine speed, and a first order lag that regulates the transition of the camshaft timing to the optimum point. A scheme for adjusting the time constant of the first order lag depending on engine speed and throttle position is described.
Theoretical and Experimental Considerations of Electrorheology With DC and AC Fields
Authors: Wu C. W. , Conrad H.
Published: March 2022

This paper reviews the recently developed theoretical models on electrorheology by the authors, which is followed by comparisons of experimental observations with the theoretical predictions for dc and ac fields. The theoretical predictions are in good accord with experiments regarding both current density and shear yield strength. Finally, some design guidelines are given for electrorheological (ER) fluids with coated particles. It is suggested that highly conducting particles coated with a surface film having reasonable conductivity and high dielectric constant are desired for high strength ER fluids.
Thermocapillary Convection of Viscoinelastic Fluids in Layered Fluid Systems
Authors: Siginer Dennis A. , Jacks Thomas E.
Published: March 2022

The flow dynamics of a finite two layered fluid system driven by thermocapillary effects when heated from the side is studied in the absence of gravity. The configuration is of low aspect ratio with a third dimension several orders of magnitude larger. The case of a low Prandtl number Newtonian fluid in the bottom layer encapsulated by a high Prandtl number viscoinelastic fluid with a shear rate and temperature dependent viscosity in the top layer is investigated numerically using the method of finite volumes together with the case of a high Prandtl number viscoinelastic fluid encapsulating another high Prandtl number viscoinelastic fluid in the lower layer both when the top surface is free and a no-slip solid cover. In either case, the top surface is considered to be insulated together with the bottom and viscous dissipation is taken into account. Free surface and interface deformations are neglected. The results are reported for both high and low Marangoni numbers. Appropriate values of the ratio of the interfacial Marangoni number to the free surface Marangoni number are determined to bring the convective motion in the lower layer to a virtual halt.
Interfacial Fracture Toughness in Plastic Packages
Authors: Nguyen L. T. , Lee G. , Jones C. , Hsu T. R. , Fang R. , Kuo A. Y. , Chen W. T.
Published: March 2022

Interracial adhesion in plastic packages is one of the key requirements to achieving popcorn-resistant packages. As part of an Air Force-funded study to develop an Expert Design System for plastic packages (EPACK®), an extensive evaluation of various interfaces in plastic packages is being conducted. Three-point bending testing was conducted on molded composite beams embedded with either Si (with and without polyimide coating), or copper alloy. Two pre-crack lengths were tried. Testing was conducted at different temperatures and humidities. The effect of residual stresses (resulting in curved test specimens) was modeled and accounted for in the evaluation of the critical interracial fracture toughness. Eventually such material properties, together with package configurations and leadframe designs, will be entered as part of the EPACK database to provide design rules for achieving Level-1 (no dry bag) performance.
Thermo-Stressed State of Anisotropic Non-Homogeneous Constructive Elements
Authors: Pankratova Nataliya D.
Published: March 2022

On the basis of the developed approach to solution of problems of the thermo-stressed state of hollow thick-walled bodies with taking into account arbitrary variability of material properties through their thickness, different modes of layers conjugations, types of boundary conditions on all limited surfaces and forms of loading according to elasticity theory the influence of non-homogeneity and anisotropy of elastic properties of materials at the stress level an deformabiity of laminated bodies in the form of a cylinder, cone, sphere or plate is studied.
Numerical Simulation of Inertia Welding of Inconel 718
Authors: Balasubramanian Vikran , Li Youlin , Stotler Tim , Crompton Jeff , Katsube Noriko , Soboyejo Winston O.
Published: March 2022

This paper presents the results of numerical simulations and experimental measurements of the temperature distributions in the heat affected zone. These were obtained for the inertia welding of IN718 to IN718 and the inertia welding of IN718 to 1045 Steel. Microstructures of the heat affected zone are presented along with microhardness profiles for the similar and dissimilar inertia welds. The measured temperature profiles are compared with numerical/finite element predictions of the temperature distributions in the heat affected zone. The effects of friction welding parameters on the temperature distributions in the heat affected zone are modeled using the finite element method. The experimental results are compared with predictions from numerical analysis. The implications of the results are then discussed in the final section of the paper.
Robust Fuzzy Control of a Magnetic Bearing System Subject to Harmonic Disturbances
Authors: Hong Sung-Kyung , Langari Reza
Published: March 2022

This paper proposes a robust fuzzy logic based control scheme for a rotating active magnetic bearing (AMB) system. We represent the nonlinear magnetic bearing by means of a Takagi-Sugeno-Kang (TSK) fuzzy model. Subsequently a systematic synthesis procedure is used to derive a nonlinear fuzzy logic control strategy that incorporates an integral control for improved tracking. Experimentation and simulation results demonstrate that the proposed fuzzy controller yields robustness against harmonic disturbances and parameter uncertainty.
A Comparative Case Study of Active Vibration Suppression by Active Power Absorption
Authors: Berkman Evan F. , Owen Arch A. , Preuss Robert D.
Published: March 2022

An optimal SISO active power absorption algorithm has recently been developed, by the authors, that maximizes the broadband power transferred from a structure to a control actuator. In this paper, numerical performance studies are presented for a controller employing this algorithm to suppress global vibrations of a simple example beam structure. The performance of optimal power absorption control strategy based only on measurement at the actuator location is compared to the performance of an optimal Linear Quadratic Regulator (LQR) controller with the same single actuator but with full state (or modal) feedback. The power absorption strategy achieved vibration reduction similar to the optimal LQR controller over most of the frequency range examined. As expected, both of these control strategies resulted in substantially better global vibration reduction than a controller that minimizes motion only at the single actuator location.
A Study on Predictive Control Using Short-Term Prediction Method Based on Chaos Theory
Authors: Masumoto Noriyasu , Yamakawa Hiroshi
Published: March 2022

The main objective of this study is an application of short-term prediction method by chaos theory to vibration control. In this paper, we proposed two predictive control methods for mechanical systems. The input time series or the output time series of a mechanical system in the near future was predicted by the short-term prediction method based on chaos theory and we used the obtained time series effectively to get the control force. The algorithm of the short-term prediction method, which is based on Takens’s theorem, used in this study and a condition to have sufficient precision of prediction were discussed from practical engineering points. The effectiveness of the proposed control methods was shown by numerical results and experimental results.
Relative Kinematics of Multibody Contacts
Authors: Pfeiffer Friedrich , Wolfsteiner Peter
Published: March 2022

Unilateral contact problems in multibody dynamics axe always accompanied by problems of relative kinematics of the contacting bodies. A general approach for plane and spatial contacts is presented based on a parametric representation of the body contours and on rules of differential geometry. Practical examples illustrate the methods.
Active Vibro-Acoustic Control of a Flexural Plate
Authors: Fariborzi Fariborz , Golnaraghi Farid , Heppler Glenn R.
Published: March 2022

Using a Rayleigh-Ritz approximation to model the transverse vibration of the Poisson-Kirchoff plate an energy based linear coupling control (LCC) strategy, for free and forced vibrations of the plate, is developed. The controller seeks to minimize a quadratic control objective and is implemented for a reduced order model by coupling a virtual second order system with each critical mode in the quadratic control objective. The energy transfer phenomena between each mode and the controller is maximized by coupling the appropriate states of the plant and the controller. Energy is transfered from the plant to the controller where it is dissipated via linear damping.
Aluminum-Boron Carbide Ceramic Composite Materials for Disk Drive Actuator Applications
Authors: Perettie D. J. , Fox R. T. , Macioce P. , Chamberlain J.
Published: March 2022

Efforts to enhance hard disk drive areal densities via increases in tracks per inch (TPI) will ultimately be influenced by the ability of the positioning system to locate the head with increasing precision in order to accurately seek and follow targeted data tracks. Actuator servo control system design goals revolve around reduction of track misregistration (TMR) in the presence of non-repeatable mechanical disturbances which can cause head placement errors impairing data reliability; error sources can include externally induced vibrations, shock, unpredictable variations in rotation due spindle and actuator bearing wear, thermal effects, and aerodynamic forces associated with rotating disks. Figure 1 illustrates a typical disk stack and actuator assembly configuration with influences on head placement.
Analysis of Contact Problems Between a Sheet and Separate-Gate-Rollers
Authors: Kobayashi Yuko , Hattori Shunsuke , Suzuki Yuji , Shima Yasuo , Ukai Makoto
Published: March 2022

Sheet separating mechanisms are used in ATMs (automated teller machines) to separate bank notes. These mechanisms are composed of separate-gate-rollers. Sheets are separated when the overlap distance of the separate-gate-rollers is appropriate. We have found out by experiment that although the appropriate overlap distance range differs according to the configuration of the separate-gate-roller, the range of friction force between a bank note and the separate-gate-roller is equally 3 to 10N. Thus, we have examined a method to estimate the friction force by numerical analysis, using the ABAQUS nonlinear structural analysis program. Consequently, calculated friction forces were found to correspond to experimental friction forces quantitatively and qualitatively.
Progress in Railroad Freight Car Engineering
Authors: Punwani Swamidas K.
Published: March 2022

This paper is the result of an annual survey, conducted by the author on behalf of the Rail Transportation Division (RTD), American Society of Mechanical Engineers (ASME) to document progress in the design, construction and use of freight cars and components. Typically, the design must be at a prototype stage or beyond in order for it to be included here.
Application of Instrumented Wheel Set Technology to Transit System Research and Development
Authors: Wilson Nicholas G. , Gurule Stanley T. , Rajkumar Britto R.
Published: March 2022

The application of strain-gaged transit car wheel sets for use on a major Latin American transit system is described in this paper. The application allowed for evaluation of turnout design and maintenance standards, provided test data for validation of the Association of American Railroads (AAR) NUCARS general vehicle dynamics computer model, allowed for further verification of previous AAR work on suspension design optimization, and also provided a tool for future work on developing performance based track maintenance standards. Performance accuracy was demonstrated through a series of validation tests on curved and perturbed track. All test results were used to compare and validate the NUCARS model predictions.
Data Transfer From BETHSY 9.1B Experiment to Real NPP
Authors: Petelin Stojan , Mavko Borut , Ravnikar Igor , Hassan Yassin A.
Published: March 2022

This paper provides the scaling-up methodology that was applied from the BETHSY integral test facility to the real Framatome NPP (Nuclear Power Plant). The ISP-27 (International Standard Problem) transient scenario was used, based on test 9.1b. The objectives were to evaluate the ideal scaling-up of BETHSY facility for real NPP and to compare and analyse the physical phenomena known from experimental background with the phenomena predicted by RELAP5/MOD3.2 simulation of real NPP transient. Further, in order to test phenomenological scaling-up basis two models for RELAP5/MOD3.2 code were constructed differing in scaling criteria for the primary cooling system. Special attention was concentrated on heat structures scaling. Data were analysed through plotting plots and NPA’s (Nuclear Plant Analyzer) graphical presentation.
Nonuniform Heat Transfer in Horizontal Helical Coils Tube Steam Generators
Authors: Bai Bofeng , Guo Liejin , Chen Xuejun
Published: March 2022

The present experiment is conducted to study the nonuniform heat transfer of single-phase water turbulent flow and two-phase steam-water flow in horizontal helical coils tubes. The inner and the outer diameter of the tube are 11mm and 15mm respectively, and the ratio of the diameter of the coil to that of the tube is 23.27. The experimental pressure ranges from 0.5 to 3.0MPa, mass flowrate from 200 to 2500 kg/m2 s, heat flux from 230 to 500kW/m2, and the maximum exit steam quality 0.86.

Along both the tube axial direction and the periphery on the cross-section, the local heat transfer coefficients are not evenly distributed. The secondary flow has less contribution to the enhancement heat transfer of the coil with increasing Reynolds number to a high level. Taking the average coefficient at outlet section as that of the coil is not reasonable.
Numerical and Experimental Studies on the Demolding of Injection Molding Parts
Authors: Wang Hao , Kabanemi Kalonji K. , Salloum Georges
Published: March 2022

Numerical and experimental studies are conducted on the demolding stage of injection molding process. Based on an integrated computer-aided-engineering software package, a numerical approach has been proposed to predict the ejection force and to analyze the layout of ejector pins. The predictions are validated in this work by injection molding of polycarbonate boxes. The boxes are molded at given processing condition while ejected with different layouts of ejector pins. The ejection force is measured by load transducers installed behind the ejector pins. The shrinkage of the boxes is also measured by displacement transducers. It is found that the measured total ejection force and its distribution over the pin layouts compare reasonably well with numerical predictions. The validation is also supported by the agreement between the predicted and measured warpage of the boxes. Additional results are provided for a complex molding geometry for which the mold opening and ejection operations need to be considered in studying the demolding.
Smart Processing of Plastics Through Vibration Controlled Shear-Thinning and Orientation
Authors: Ibar J. P.
Published: March 2022

This paper covers the technology of melt vibration during the molding of plastic material (more specifically at low frequency) to reduce the viscosity and ease processability and to produce orientation benefits. The effect of vibration frequency and amplitude on melt viscosity is explained in terms of shear-thinning criteria. The effect of pressure, temperature and cooling rate on shear-thinning is also reviewed to predict how these variables interfere with melt vibration. Applications to injection molding, extrusion and blow molding of uneasily processable plastic melts (such as metallocenes polyolefins) are suggested.
Orientation Formation in Planar Mold Filling: Experimental Results
Authors: Olivero Kristian A. , He Jufang , Altan M. Cengiz
Published: March 2022

The formation of orientation field of short fibers suspended in a highly viscous flow through a planar mold cavity is experimentally analyzed. Such flows are common in injection molding of short-fiber-reinforced composite materials. A suspension of corn syrup and nylon fibers is injected at a constant flow rate through a narrow planar inlet gate into an experimental mold cavity. The flow undergoes a sudden expansion near the inlet gate, followed by a three to one contraction downstream. Photographs of thirteen zones of interest in the vicinity of the sudden contraction are taken through transparent mold walls after the flow achieved steady conditions. Computerized image analysis is performed to obtain orientation data for all the fibers within the zones of interest. This data is used to calculate a through the thickness average of the second-order orientation tensor, which is commonly used to quantify orientation field. The experimental results are qualitatively consistent with numerical predictions based on Jeffery’s theory, but quantitative agreement is not satisfactory. Orientation distribution histograms are generated to provide a more detailed representation of the orientation field. The histograms reveal a bimodal distribution, with an alignment peak along the direction of the theoretically calculated preferred orientation, and a second peak perpendicular to the flow direction. The failure of the second-order orientation tensors to quantitatively describe the experimental data seems to be due to these bimodal distributions. Radial orientation histograms at five zones of interest are presented along with the theoretical predictions at these locations.
Prediction of Race Tracking in Resin Transfer Molding
Authors: Owusu-Ofori Samuel P. , Pai Devdas M. , Sadler Robert L.
Published: March 2022

The resin transfer molding process experiences an unavoidable phenomenon known as race-tracking in which the resin flows along the edges of the mold ahead of the central flow. This phenomena may be severe whereby the resin reaches the top of the mold and exits the mold before it is completely filled. It is of interest to predict this behavior prior to the resin injection. A pre-injection method has been developed to predict whether the flow will be even or skewed and the severity of race tracking. This paper discusses how the method was developed. This method has been successfully used to predict the degree of severity of race tracking in vacuum-assisted resin transfer molding to a high degree of accuracy.
Simulation of Self-Propagating High-Temperature Synthesis Using Finite Element Method
Authors: Swaminathan Vinodh , Koczak Micheal J. , Kalidindi Surya R.
Published: March 2022

Self-Propagating High-Temperature Synthesis (SHS) is an energy efficient process for the synthesis of refractory ceramics and intermetallic compounds, and composites of these materials including functionally gradient materials (FGMs). The process utilizes the large exothermic heat of reaction between two or more elements (or compounds) in order to convert the reactants into one or more useful products. The products of SHS, in general, have been observed to possess significant amounts of residual porosity. It has been reported that a certain amount of liquid phase during the reaction aids in the consolidation process. In order to control the amount of liquid formed during SHS, it is necessary to develop a good understanding of the parametric influence of the various process parameters such as pre-heat, dilution, heat losses, etc. on the SHS reaction. In this study, a commercial finite element program, ABAQUS (1996), has been used to simulate SHS and to study the effects of process parameters that influence and help control the reaction. Processing maps have been developed for Ni-Al system based on the FEA results that can aid in syntheses of nickel aluminides and FGMs using these compounds with low residual porosities.
Effects of Stress Concentrations at the Slipping Fiber/Matrix Interface on Tensile Strength of Ceramic Matrix Composites
Authors: Ahn B. K. , Curtin W. A.
Published: March 2022

Ceramic matrix composites can exhibit a transition from strong, tough behavior to brittle behavior as the interfacial sliding resistance τ between the fibers and the matrix increases. The detailed micromechanical reasons for this dangerous transition are not well understood, but are clearly important for optimizing performance in such composite systems. One mechanism of weakening involves a transition, with increasing τ, from “global” to “local” load transfer from broken to unbroken fibers near the slipping interface. These stress concentrations have been nicely investigated previously by Steif and coworkers (1991) for 2d geometries and by Weitsman and coworkers (1993) using shear-lag for an axisymmetric problem, but the precise implications of these stress concentrations on actual tensile composite failure have not been fully investigated. Here, the problem of stress concentrations in the fiber is revised using the very accurate yet efficient Axisymmetric Damage Model of Pagano (1993) to calculate the axial fiber stresses. The geometry is axisymmetric with a transverse matrix crack and a debond crack along the fiber/matrix interface having a constant sliding resistance τ. The stress concentrations obtained are compared to previous results, and generally increase with increasing τ. More importantly, the fiber surface stresses are then used to determine the probability of fiber fails by surface flaws having a Weibull probability distribution, and the overall composite strength is calculated in a manner similar to that originally suggested by Thouless and Evans for a single matrix crack. The results show a decrease in strength with increasing τ, relative to the common approximation of assuming uniform stresses across the fiber cross-section. The nature of the tough to brittle transition will be discussed in light of these results.
Effect of Creep Feed Grinding Parameters on Strength and Finish of Alumina
Authors: Sathyanarayanan G. , Plebani Louis J. , Wang Hsueh-Ming S.
Published: March 2022

The reliability of ground ceramics is affected by the subsurface cracks. Alumina was creep feed ground by utilizing a 25-1 fractional factorial design to vary the bond type, mesh size and concentration, feed rate, and depth of cut. The unit load, i.e., the normal force transmitted by each grit, was obtained from the normal grinding force and utilized to analyze the material removal mechanism and the observed roughness. The flexural strength is obtained from four point bending tests and correlated with unit load and surface finish. The study shows that creep feed grinding is best suited for alumina. Also the present study shows that fine mesh size and fast feed rate are recommended to grind alumina in order to obtain higher flexural strength.
High Strain Rate Normal Indentation of Ceramics: Implications for Material Removal Mechanisms
Authors: Subhash Ghatu , Koeppel Brian J. , Anton Richard J. , Huang Yonggang Y. , Chandra Abhijit
Published: March 2022

The static indentation fracture mechanics approach does not fully capture the rate sensitive nature of failure behavior in ceramics. Accordingly, a dynamic indentation technique was developed to investigate material removal mechanisms at strain rates similar to those encountered in realistic grinding situations. The technique is designed to deliver a single indentation load of duration 100 microseconds. Compared to static loading, it is observed that lateral cracking is promoted under dynamic loading rates. The implications of dynamic loading on the material removal mechanisms are discussed.
Orthotropic Column Buckling: The Euler and Engesser/Haringx/Timoshenko Formulas Versus an Elasticity Solution
Authors: Kardomateas George A.
Published: March 2022

The well known column buckling formulas of Euler and these of Engesser / Haringx / Timoshenko (which correct for transverse shear) were derived for isotropic materials, and are routinely used in composite structural applications. The accuracy of these formulas, when orthotropic composite material and moderate thickness are involved, is investigated in the present study by comparing the critical loads from these formulas with the predictions of a three-dimensional orthotropic elasticity solution. The column is assumed to be in the form of a hollow circular cylinder and the Euler or Timoshenko loads are based on the axial modulus. As an example, the cases of an orthotropic material with stiffness constants typical of glass/epoxy or graphite/epoxy and the reinforcing direction along the periphery or along the cylinder axis are considered. First, it is found that the elasticity approach predicts in all cases a lower than the Euler value critical load. Moreover, the degree of non-conservatism of the Euler formula is strongly dependent on the reinforcing direction; the axially reinforced columns show the highest deviation from the elasticity value. Second, the Engesser or first Timoshenko shear correction formula is conservative in all cases examined, i.e. it predicts a lower critical load than the elasticity solution. The Haringx or second Timoshenko shear correction formula is in most cases (but not always) conservative. However, in all cases considered, the second estimate is always closer to the elasticity solution than the first one. For the isotropic case both Timoshenko formulas are conservative estimates.
Stacking Sequence Effects on the Process-Induced Free-Edge Stresses in Thermoplastic Composite Laminates
Authors: Domb Moshe M. , Hansen Jorn S.
Published: March 2022

A numerical model is developed for prediction of the process-induced thermal residual stresses in thermoplastic composite laminates. The model addresses the development of the residual stress state in fracture-critical free-edge regions as well as through-thickness stress variations. The current approach provides a unique capability for the investigation of the influence of thermal processing and structural parameters on the resulting buildup of residual stresses during manufacturing. Therefore, it can assist in the design and analysis of thermoplastic composites to tailor mechanical and strength characteristics. Thermal processing considered here includes solidification from the molten state at a specific surface cooling rate, and application of a posterior annealing cycle. A significant reduction in the free-edge stresses is obtained via a quench/anneal cycle in comparison to the recommended nominal cooling from the melt. Alteration of the stacking sequence of the plies in the laminate can further reduce the magnitude of the interlaminar stresses. Results are shown for the case of a quasi-isotropic APC-2 (graphite/PEEK) laminate configuration.
Free Vibration Analysis of Composite Plates With Tailored Thermal Residual-Stresses
Authors: de Almeida Sérgio Frascino Müller , Hansen Jorn S.
Published: March 2022

Thermal residual-stresses introduced during manufacture and their effect on the free vibration of stringer stiffened composite plates is investigated. The principal idea in the work is to include stiffeners on the perimeter of a composite plate in which the laminate for the stiffeners and the plate are different. Such an arrangement yields manufacturing induced thermal residual-stresses which result from the difference in manufacturing and operating temperatures as well as the difference in thermal expansion coefficients and elastic properties of the plate and the stiffeners. The analysis is based on an enhanced Reissner-Mindlin plate theory and involves two separate calculations. In the first, the thermal residual-stress state is determined for an unconstrained plate. In the second, the free vibration problem is solved; thermal effects from the first calculation are included by way of nonlinear membrane-bending coupling which in turn defines the free vibration reference state. The problem is solved using a finite element formulation to determine the natural frequencies and vibration modes of the plates. Two different plate-stiffener geometries are used to illustrate the effects of stringer size, stringer placement and temperature difference. Two principal results are obtained: first, it is shown that thermal residual-stresses can have a significant effect on the natural frequencies; secondly, thermal residual-stresses can be tailored to increase natural frequencies.
On the Optimization of Composite Cylindrical Sandwich Shells Subjected to Beam Type Bending
Authors: Vinson Jack R.
Published: March 2022

Sandwich construction offers several advantages over monocoque and various discretely stiffened structures. These include greater load carrying ability, reduced weight, higher buckling loads and higher fundamental natural frequencies. The equations for the analysis and design of sandwich cylindrical shells subjected to beam type bending are presented herein. These equations are then manipulated to provide the face thickness, core depth, and core shear modulus to produce a minimum weight structure for a given load index and face material system. A factor of merit to select the best face material is also presented. As examples, Carbon/epoxy and E-glass/epoxy cross-ply composite faced sandwich shells are compared, as well as comparison with a monocoque cross-ply laminated shell.
Experimental Study of Wavy-Stratified and Countercurrent Annular Flow Using Photochromic Dye Activation Technique
Authors: Kawaji Masahiro , Karimi Gholamreza , Nasr-Esfahany Mohsen
Published: March 2022

A non-intrusive flow visualization method called photochromic dye activation (PDA) technique has been used to investigate flow structures and mechanisms in wavy-stratified and annular flows in a horizontal channel and wavy falling films in countercurrent annular flow in a vertical tube. This non-intrusive flow visualization technique utilizes light activation of a photochromic dye material dissolved in a clear liquid and is a molecular tagging technique, requiring no seed particles. It has been used to yield both quantitative and qualitative flow data in the liquid phase in wavy-stratified, annular and countercurrent annular flows.
On Incompressible Turbulent Flow
Authors: Gao Ge , Yong Yan
Published: March 2022

A new unilateral average scheme is proposed in this paper for the purpose of retaining the first-order statistical information of turbulence fluctuations. In this approach, the fluctuations are divided into two groups according to their projections onto the mean flow. A forward (backward) fluctuation has a positive (negative) projection, and the corresponding ensemble average is called forward (backward) drift velocity. The momentum equations of these drift flows are derived within the framework of the Navier-Stokes equations. With the aid of the concept of modified eddy viscosity, these momentum equations join the conventional Reynolds-averaged Navier-Stokes equation constituting rational equations of incompressible turbulent flow. The rational equations contain no empirical coefficients, and their very same form is valid for all flow regions. The merit of the present approach is demonstrated by a numerical example of transition simulation of a flat-plate boundary layer without using the wall functions. Details of the transition, including change in velocity profiles from laminar to turbulent and change in thickness and length of the boundary layer in the transition zone, are in good agreement with existing experimental results.
Performance of the Triple-Concentric Air-Assist Atomizer
Authors: Mansour Adel , Humphrey William , Chigier Norman
Published: March 2022

The spray characteristics of the triple-concentric air assist atomizer have been explored using a Greenfield Digital Spray Analyzer and a Malvern Particle Sizer. The improved performance of the atomizer, as measured by the total amount of air required to generate a particular average droplet size, was demonstrated. A nearly ten-fold reduction in the total air quantity required for atomization is achieved.
Does a Strange Attractor Exist in Two-Phase Vertical Upflow?
Authors: Langford Heather M. , Beasley Donald E.
Published: March 2022

Instantaneous pressure measurements in air-water vertical upward flow in a circular pipe were analyzed to determine if the signals are consistent with deterministic chaotic behavior. Analysis of conventional Fourier power spectra characteristics yielded evidence consistent with a chaotic signal. Chaos measures were employed to provide both qualitative and quantitative evidence of the nature of the dynamics in bubbly flow (hemispherical cap), slug flow, and churn flow. A qualitative study of the system trajectory in phase space revealed dynamics consistent with a nonlinear system. The positive definite values of Kolmogorov entropy for all pressure signals quantitatively indicated that the system may be governed by chaotic dynamics. Therefore, the flow regimes studied in this investigation indicate the presence of a strange attractor.
Some Investigations on Flow Through Chevrons of Moisture Separator and Reheater Used in Nuclear Power Plants
Authors: Iyer V. Keshava , Dasgupta A. , Rao B. Venkat , Srivastava R.
Published: March 2022

An innovative working model of a Moisture separator reheater (MSR) used in nuclear power plants was fabricated using transparent acrylic sheets. All the internal flow passages including drain water siphoning arrangement was modelled. The sinusoidal vanes (chevrons) of the MSR were made out of galvanised iron sheets. The model was tested in an air flow test rig fitted with water spray nozzles, mounted in counter flow direction. Effect of inlet flow velocity on the performance of the MSR was studid over range of air flow velocities between 4.50 to 6.75 m/s. The pressure drop occurring in the fine separator of MSR was determined from the probe traverse data at the fine separators. The critical velocity of the flow through the chevron packs was determined from the probe traverse data. Using the overall separation efficiency, the average droplet size used in the air-water droplets was calculated. The pressure drop data can be used to detect fouling of the chevrons. The operating flow velocities at inlet to chevrons are known for the present experimental results.
Propagation of Thermal and Evaporation Waves Through Water-Wet Porous Media During Through-Flow Air Drying
Authors: Stacey Devin A. , Udell Kent S.
Published: March 2022

The simultaneous propagation of thermal and evaporation waves through a one-dimensional, water-wet porous media subjected to through-flow air drying is investigated through a set of theoretical, numerical, and experimental studies. The injection of dry air at a constant temperature, equal to the uniform initial temperature of the medium, is considered. Theory is developed for the limiting cases of i) a fast evaporation wave velocity relative to the characteristic thermal wave velocity, and ii) a fast thermal wave velocity relative to evaporation wave velocity. Mass and energy conservation equations are transformed to coordinates moving with the waves and the general energy transfer and drying behavior is described. Numerical simulations and experiments were performed for the two limiting cases plus one in which the evaporation wave velocity was approximately equal to the speed of the thermal wave. The numerical simulations and experimental data verified the basic features of the theoretical description. Theoretical, numerical and experimental results show that dryout times and temperature distributions in the one-dimensional porous medium were strongly dependent on the relative speeds of the thermal and evaporation waves. Contrary to conventional thought, the temperatures found in the porous matrix are not directly related to wet-bulb values. Under the condition where the evaporation wave velocity is equal to the speed of the thermal wave, a theoretical singularity suggests a very large temperature drop at the front; simulations and data for velocities approximately equal show the temperature at the front continuing to decrease with time to an extrapolated limit of freezing water.
Modeling of Growing Billet Shape in Spray Forming Process Using Scanning Gas Atomizer
Authors: Kang Shinill , Chang Dong-Hoon , Lee Eon-Sik
Published: March 2022

A numerical method is presented to predict and analyze the shape of a growing billet produced from the “spray forming” which is a fairly new near-net shape manufacturing process. It is important to understand the mechanism of billet growing because one can obtain a billet with the desired final shape without secondary operations by accurate control of the process, and it can also serve as a base for heat transfer and deformation analyses. The shape of a growing billet is determined by the flow rate of the alloy melt, the mode of nozzle scanning which is due to cam profile, the initial position of the spray nozzle, scanning angle, and the withdrawal speed of the substrate. In the present study, a theoretical model is first established to predict the shape of the billet and next the effects of the most dominant processing conditions, such as withdrawal speed of the substrate and the cam profile, on the shape of the growing billet are studied. Process conditions are obtained to produce a billet with uniform diameter and flat top surface, and an ASP30 high speed steel billet is manufactured using the same process conditions established from the simulation.
Study on Forced-Convective Film-Boiling Heat Transfer: Effects of Liquid Flow on a State of Vapor Film Flow
Authors: Sasaki Hidemasa , Ohtake Hiroyasu , Koizumi Yasuo
Published: March 2022

Focusing on the effects of a liquid velocity and subcooling, in this study the foced-convective film-boiling heat transfer was examined experimentally and analytically. Quenching tests of a vertical-long-thick cylindrical pipe were conducted for subcooled R-113 liquid in a range of bulk-liquid velocities from 0.018 to 0.081 m/s at a pressure of 0.1 MPa. The test section made of pure copper was 50, 15 and 110 mm in outer diameter, thickness and height, respectively. The test section was inserted into a transparent Pyrex glass pipe concentrically, and an annular flow passage was formed between the glass pipe and the test section.

Measured heat transfer coefficients were higher than those predicted with the two-phase boundary layer theory even in a low liquid velocity region. The characteristics of the measured heat transfer coefficients were quite similar to those of the pool film boiling. The vapor-film-unit model developed for the natural-convective film boiling was extended and applied to the present conditions. In the model, the Kelvin-Helmholtz instability wave length was used to give the length scale of the unit. The model provided good agreement with the experimental results.