bluuebunny/crossref_metadata_2025 huggingface dataset:
Equivalent Active Circuits of Distributed Control Systems
Authors: Tzou H. S. , Ding J. H.
Published: November 2021

Modeling distributed parameter systems (DPS) by electronic circuits and fabricating the complicated equivalent circuits to evaluate the system characteristics always poses many challenging research issues for years. Modeling and analysis of distributed sensing/control of smart structures and distributed structronic systems are even scarce. This paper is to present a technique to model distributed structronic systems with electronic circuits and to evaluate control behaviors with the fabricated equivalent circuits. Electrical analogies and analysis of distributed structronic systems is proposed and dynamics and control of beam/sensor/actuator systems are investigated. To determine the equivalent circuits and system parameters, higher order partial derivatives are simplified using the finite difference method; partial differential equations (PDE) are transformed to finite difference equations and further represented by electronic components and circuits. To provide better signal management and stability, active electronic circuit systems are designed and fabricated. Electric signals from the distributed system circuits (i.e., soft and hard) are compared with results obtained by classical theoretical and other (e.g., the finite element, and experimental) techniques.
The Architecture and Development Environment of Virtual Manufacturing Systems
Authors: Yuan Qing Ke , Chen Xin
Published: November 2021

For adapting the demands of the rapid changing and enhancing the competing capability of enterprise in the international market, various modern manufacturing systems have been put forward, which are aimed at various specifications, perfect performance and high quality, low production cost and short manufacturing cycle of products, virtual manufacturing system (VMS) has been emerged as the times require, which is effective technology to meet the challenge of 21 century’s manufacturing industries. Based on analyzing modern manufacturing systems, according to the characteristics and requirement of VMS, in this paper, the architecture, the key technologies and the implement way of VMS were explored, and development environment for VMS was put forward, which is a powerful tool for building VMS.
Modeling and Experiment on Physical and Chemical Liquid Deposition Processes for Rapid Tooling and Manufacturing
Authors: He Zongyan , Zhou Jack G.
Published: November 2021

A new solid free-form fabrication (SFF) technique, named Physical and Chemical Liquid Deposition (P/CLD), is introduced in this paper, and then several key technical problems are stated. In order to solve these problems, theoretical models to describe the nucleation and growth of deposits in PLD, the chemical dynamic process in CLD, and the heat transfer in P/LCD are studied. To determine the heat transfer parameters, some experiments are designed and experimental results are presented.
Mechanical Characterization of Gold Bonding Wires With Different Doping at Extreme Temperatures
Authors: Mahadevan Dave S. , Hause Vern , Lee Tien-Yu Tom
Published: November 2021

A new process was developed to characterize the mechanical strength of small bonding wires under extreme temperature environment. By the combination of innovative fixture designs and a commercially available mechanical tester, both Beryllium and Calcium doped wires were evaluated for their strengths in the temperature range of −55°C to 250°C. Results indicated that the tensile break strength of Beryllium doped wire decreased with an increase in temperature throughout the temperature range tested whereas for Calcium doped wire it remained generally constant throughout. In addition, percent elongation of Beryllium doped wire significantly increased above 200°C whereas Calcium doped wire exhibited a constant decrease with an increase in temperature. Up to a tensile load of 27.5 grams, both wires were loaded less than their elastic limit under normal operating conditions (−40°C to 150°C). Hence, the cyclic load would not weaken the wire. If that limit is exceeded, Beryllium doped wire would weaken. Calcium doped wire has the advantage of resisting extrusion after the formation of wire bond giving added strength in normal operating conditions.
Quench Process Modeling and Optimization
Authors: Bellur-Ramaswamy Ravi S. , Sobh Nahil A. , Haber Robert B. , Tortorelli Daniel A.
Published: November 2021

We optimize continuous quench process parameters to produce a desired precipitate distribution in aluminum alloy extrudates. To perform this task, an optimization problem is defined and solved using a standard nonlinear programming algorithm. Ingredients of this algorithm include a cost function, constraint functions and their sensitivities with respect to the process parameters. These functions are dependent on the temperature and precipitate size which are obtained by balancing energy to determine the temperature distribution and by using a reaction-rate theory to determine a discrete precipitate particle size distribution. Both the temperature and the precipitate models are solved via the finite element method. Since we use a discrete particle size model, there are as many as 105 degrees-of-freedom per finite element node. After we compute the temperature and precipitate size distributions, we must also compute their sensitivities. This seemingly intractable computational task is resolved by using an element-by-element discontinuous Galerkin finite element formulation and a direct differentiation sensitivity analysis which allows us to perform all of the computations on a PC.
Viscoplastic Constitutive Modeling of Anisotropic Damage Under Nonproportional Loading
Authors: Chow C. L. , Yang X. J. , Chu Edmund
Published: November 2021

Based on the theory of damage mechanics, a viscoplastic constitutive modeling of anisotropic damage for the prediction of forming limit curve (FLC) is developed. The model takes into account the effect of rotation of principal damage coordinates on the deformation and damage behaviors. With the aid of the damage viscoplastic potential, the damage evolution equations are established. Based on a proposed damage criterion for localized necking, the model is employed to predict the FLC of aluminum 6111-T4 sheet alloy. The predicted results agree well with those determined experimentally.
Calculation of Punch Force and Maximum Pressure for Tube Extrusion
Authors: Zhang S.-H. , Shang Y.-L.
Published: November 2021

Punch force and maximum pressure for tube extrusion can be predicted with an upper bound theory-based program POLSK. Experiments of steel tube extrusion and wax physical modeling were performed. The punch force and the maximum pressure values were obtained. Comparisons were made among the experimental results, physical modeling results and upper bound predictions. It was found that a medium extrusion coefficient causes the lowest pressure on the tooling system, very low and very high extrusion coefficients can both cause very high pressure. It is proved that the upper bound predictions are in good agreement with the experimental results and the upper bound program is suitable for use of steel tube extrusion design.
A Stabilized Mixed FEM for Viscoplastic Flow Analysis
Authors: Liu Yong , Maniatty Antoinette M. , Klaas Ottmar , Shephard Mark S.
Published: November 2021

A stabilized, mixed finite element method for viscoplastic flow analysis is presented. Preliminary results show promise for modeling steady-state bulk forming processes. In this work, the Ladyzenskaya-Babuska-Brezzi (LBB) condition is circumvented by adding mesh dependent terms (stabilization terms), which are functions of the residual of the Euler-Lagrange equations, to the usual Galerkin method. The stabilized formulation and applications to plastic flow problems are presented. Numerical experiments using the stabilization method show that the stabilized, mixed FEM is effective and efficient for non-linear steady forming problems.
Real-Time Process Characterization of Open Die Forging for Adaptive Control
Authors: Nye T. J. , Elbadan A. M. , Bone G. M.
Published: November 2021

Open die forging is a process in which products are made through repeated, incremental plastic deformations of a workpiece. Typically, the workpiece is held by a manipulator, which can position the workpiece through program control between the dies of a press. The part programs are generated with an empirically derived parameter, called the spread coefficient, whose value is subject to some contention. In this work, we demonstrate how process information can be used in real time to derive the actual spread coefficient for a given workpiece as it is being formed. These measurements and calculations occur in real time, and can be used to regenerate part programs to optimize the forming process, or can be used to adaptively control each incremental deformation of the workpiece.
Solid Freeform Fabrication by Ultrasonic Joining: Implementation and Mechanical Analysis
Authors: Gao Yuan , Greif Robert , Doumanidis Charalabos
Published: November 2021

This article presents the mechanical analysis of an emerging nonthermal Rapid Manufacturing technology for layered fabrication of metallic or multiple-material products, i.e. the Multi-material Ultrasonic Adhesion process, based on Ultrasonic Welding. Its laboratory implementation, automation and integration, and parameter optimization are described first. The mechanics of Ultrasonic Welding, the stress and strain field changes during one weld, and static and dynamic behavior of the weld material are then analyzed. The technical advantages of Ultrasonic Welding for the manufacturing industry include fabrication of dense, full-strength functional solid metal parts, multiple-material composites, and active parts with embedded intelligent components and electronic, mechatronic, optic and fluidic structures.
Development of a MicroPCM Machine Coolant
Authors: Colvin David P. , Colvin Virginia S. , Bryant Yvonne G. , Whitney Ray A. , Sheikh-Ahmad Jamal Y. , Bailey John A.
Published: November 2021

Under multiple SBIR (Small Business Innovation Research) programs from the Department of Defense, NASA and the National Science Foundation, investigators at Triangle Research and Development Corporation (TRDC) and associated universities have conducted research toward the development of a new machine coolant that has demonstrated some significant advantages. Results in SBIR programs for NASA, USAF and NAVY, that were reported in earlier publications, have indicated that both aqueous and non-aqueous two-component coolants containing microencapsulated phase change materials (microPCMs) can provide from 10× to 40× (1,000% – 4,000%) enhancement in the coolant’s effective thermal capacitance along with isothermal heat transport and significant improvement in the system’s Nusselt Number. During another SBIR program for the National Science Foundation, a non-aqueous, two-component microPCM machine coolant was used for machine turning operations and demonstrated (a) an increase in the effective thermal capacitance of a machine coolant oil by more than 10× or 1,000%, (b) a significant reduction in the temperature of a work/tool thermocouple as much as 15%, (c) a reduced temperature excursion of the machining coolant by more than 90% for the same cutting speeds and feed rates, (d) a significant reduction in the tool force by 25 to 75%, and (e) a highly significant reduction in the environmental pollution in the shop due to much lower evaporation of the machine coolant. The further development of such a microPCM machine coolant could potentially (a) significantly increase tool life (related to the thrust force), (b) improve product quality, dimensional accuracy and tolerance, and (c) reduce both coolant loss and operator exposure to hazardous evaporating coolants during high-speed machining operations. Follow-on experiments at General Motors have also demonstrated that microPCM coolants can be used effectively during grinding operations.
Integration of Mechanical and Biological Criteria When Defining Injury Tolerance
Authors: Lotz Jeffrey C. , Bass Elisa C. , Wagner Diane R.
Published: November 2021

Degeneration of the intervertebral disc is an important clinical and socio-economic problem. Because of associations between injury rates and physical activity, mechanical factors are thought to play an important role in the incidence and progression of this disease. Bioengineers have historically utilized a strength-of-materials approach to develop tolerance criteria and design interventions meant to reduce injury risk. However, it has become apparent that the disc’s biologic response to loading is an important determinant of degeneration rate. In order to quantify degeneration risk, a hierarchical approach is required which links whole body mechanical exposures to tissue responses that are consistent with the clinical presentation. One challenging aspect of this approach is the definition of accurate constitutive relationships for disc tissues, which are inherently nonlinear, anisotropic and heterogeneous. A second challenge is the development and interpretation of models that allow assessment of the in vivo biologic response to loads. Recent progress in these areas indicates that mechanical and biological factors should be quantitatively linked to provide a comprehensive injury tolerance criteria.
Bubble Nucleation Under External Pressure in Nitrogen-Polystyrene Microcellular System
Authors: Kumar Vipin
Published: November 2021

Polystyrene disks were saturated with nitrogen at 2000 psi pressure (13.8 Mpa) and foamed at 115 C in a pressurized cavity. It was found that the cavity pressure had no influence on the cell nucleation density. This was a surprising result, since based on classical nucleation models, we expected fewer and fewer cells to nucleate as we increased the cavity pressure.
Modeling and Bumpless Learning Control of Position and Pressure for an Electropneumatic Actuator
Authors: Ng Han Wee , Alleyne Andrew
Published: November 2021

This paper presents the modeling, simulation and control of a pneumatic cylinder actuator driven by a high-performance pneumatic servovalve. The modeling is done via a combination of first principles and empirically identified system characteristics. A stick-slip friction model is incorporated as a necessary component of the overall system description. The model is verified against experimental data and shown to be quite accurate over a range of operating conditions. Two separate Iterative Learning Controllers (ILC’s) are applied to the system to improve the overall sequential tracking of position and pressure reference inputs. In addition, a bumpless transfer technique is used to transition between the position and pressure control loops in a smooth manner. The profiles chosen are similar to those found in certain manufacturing processes such as blow molding. It is show via simulation and experiment that the ILC can provide an improvement in the system tracking capabilities and the bumpless transfer can be used very effectively to minimize transients in the changeover from position to pressure.
Trade-Off Analysis for the Design of a High Performance Hydrostatic Actuation System
Authors: Habibi S. R.
Published: November 2021

This paper considers the design of a high performance hydrostatic actuation system referred to as the ElectroHydraulic Actuator (EHA). The expected performance of EHA and its dominant design parameters are identified by using mathematical modeling. The design parameters are classified into Direct and Indirect categories based on the measure of their accessibility to the designer. The Direct parameters are directly quantifiable and, can be linked to the performance of EHA through a set of mathematical functions.

A prototype of EHA has been produced and described. The mathematical functions linking performance to design parameters are used to investigate design trade-offs. Design improvements to the prototype are suggested by using constrained quadratic programming.
Free Vibration of Stepped and Restrained Cantilever Beams Connected With a Rigid Body: Exact and Numerical Solutions
Authors: Kwon Hyuck-Dong , Park Young-Pil , Yang Hyun Seok
Published: November 2021

The object of this work is to analyze the dynamic characteristics of the portal closed frame which consists of two stepped beams including a torsional spring at the discontinuous point and a rigid body connecting each beam tips. This system is available in a lot of cases that need higher stiffness and linear motion of the tip mass. For example, it might be used for an optical pick-up actuator, using piezoelectric materials, of the high areal density CD, DVD or the next generation of optical memory devices, which requires super rigidity and linear motion in focusing. The mathematical modeling and the derivation of the equation of motion are given for the beam that is identically paralleled and stepped cantilevers. The equation of motion and the associated boundary and the continuous conditions are analytically obtained by using variational Hamilton’s principle. The exact solutions are presented and compared with the results obtained by the use of the FEM Tool (IDEAS).
Study of In-Plane Motions in a Thin Rotating Disk
Authors: Deshpande Moreshwar , Mote C. D.
Published: November 2021

A model for the in-plane oscillations of a thin rotating disk has been derived using a nonlinear strain measure to calculate the disk energy. This accounts for the stiffening of the disk due the radial expansion resulting from its rotation. The corresponding non-dimensionalized natural frequencies are seen to depend only on rotation speed and have been calculated. The radially expanded disk configuration is linearly stable over the range of rotation speeds studied here. The sine and cosine modes for all nodal diameters couple to each other at all nonzero rotation speeds and the strength of this coupling increases with rotation speed. This coupling causes the reported frequencies of the stationary disk to split. The zero, one and two nodal diameter in-plane modes do not have a critical speed corresponding to the vanishing of the backward travelling wave frequency. The use of a linear strain measure in earlier work incorrectly predicts instability of the rotating equilibrium and the existence of critical speeds in these modes.
Nonlinear Resonant Motion of Traveling Waves in Rotating Disks
Authors: Luo Albert C. J. , Tan Chin An
Published: November 2021

The resonant conditions for traveling waves in rotating disks are derived. The nonlinear resonant spectrum of a rotating disk is computed from the resonant conditions. Such a resonant spectrum is useful for the disk drive industry to determine the range of operational rotation speed. The resonant wave motions for linear and nonlinear, rotating disks are simulated numerically for a 3.5-inch diameter computer memory disk.
Influence of Core on Face/Core Debond Toughness
Authors: Viana Camps Gilmer M. , Carlsson Leif A. , Li Xiaoming
Published: November 2021

The influence of mechanical properties and fracture toughness of the core on debond fracture toughness of foam core sandwich has been examined. It was found that the fracture toughness for debonding was larger than the core toughness. The observed difference between core fracture toughness and face/core debonding toughness was analyzed using plastic zone size and mode mixity arguments. The difference in toughness can not be explained by plastic zone size and mode mixity effects. It is possible that the core displays a gradient in properties and fracture resistance, and anisotropic behavior which might explain the difference in toughness.
Effects of Interfacial Delaminations in Curved Sandwich Beams
Authors: Layne Andrew M. , Carlsson Leif A.
Published: November 2021

The influence of face/core debonding on the structural integrity of curved sandwich beams subjected to opening bending moments has been examined experimentally. The sandwich beams consisted of glass/polyester faces over a PVC H30 foam core. Debonds of various sizes were implanted by inserting thin teflon sheets at the outer face/core interface in the curved region of the beam prior to processing. A test fixture for flexure testing of curved sandwich beams was designed and manufactured, and evaluated using homogeneous isotropic beams. The surface strains at the middle of the curve were recorded to examine the response. Buckling of the debonded face sheet occurred followed by face/core propagation of the debond. Strength reduction of the beams under opening moments due to face/core debonding was substantial.
An Asymptotic Solution for the Response of Face-Sheet Delaminations/Debonds Under Compression
Authors: Kardomateas George A. , Huang Haiying
Published: November 2021

The buckling and initial postbuckling behavior of face-sheet delaminations or face-sheet/core debonds is studied by a perturbation procedure. The procedure is based on the nonlinear beam equation with transverse shear included, and an asymptotic expansion of the load and deformation quantities. First the characteristic equation for the critical load is formulated and this is a nonlinear algebraic equation. Subsequently, the first order load is found from a system of linear equations and the initial postbuckling behavior can thus be studied. The procedure can be easily expanded to the higher order terms. The effect of transverse shear is illustrated with results on the critical strain and the initial postbuckling displacement.
Sandwich Shell Finite Element for Dynamic Explicit Analysis
Authors: Tabiei Ala , Tanov Romil , Birman Victor
Published: November 2021

This work presents the finite element (FE) formulation and implementation of a higher order shear deformable shell element for dynamic explicit analysis of composite and sandwich shells. The formulation is developed using a displacement based third order shear deformation shell theory. Using the differential equilibrium equations and the interlayer requirements, a treatment is developed for the transverse shear, resulting in a continuous, piecewise quartic distribution of the transverse shear stresses through the shell thickness. The FE implementation is cast into a 4-noded quadrilateral shell element with 9 degrees of freedom (DOF) per node. Only C0 continuity of the displacement functions is required in the shell plane, which makes the present formulation applicable to the most common 4-noded bilinear isoparametric shell elements. Expressions are developed for the critical time step of the explicit time integration for orthotropic homogeneous and layered shells based on the developed third order formulation. To assess the performance of the present shell element it is implemented in the general nonlinear explicit dynamic FE code DYNA3D. Several problems are solved and results are compared to other theoretical and numerical results. The developed sandwich shell element is much more computationally efficient for modeling sandwich shells than solid elements.
A Novel Non-Intrusive Probe of Particle Motion and Gas Generation in the Feed Injection Zone of the Feed Riser of a Fluidized Bed Catalytic Cracking Unit
Authors: Cody G. D. , Bellows R. J. , Goldfarb D. J. , Wolf H. A. , Storch G. V.
Published: November 2021

We define a non-intrusive Acoustic Shot, Noise, ASN, probe of particle velocity at the wall of fluidized beds and transfer lines, and demonstrate how it can be used to obtain quantitative data on changes in particle velocity at the wall through changes in the mean squared wall acceleration of the wall vibrational energy produced by random particle impact or ASN. We note that the probe can be simply calibrated if any two of the following quantities are known for the transfer line: (1) average Axial Velocity of particles; (2) average Axial Mass Density of particles; (3) average Mass Flux of particles. We present the first field data on simultaneous measurements of ASN excited wall vibrational energy along the feed riser of Fluidized Catalytic Cracking Units where catalyst particle flow is produced by the gas generated in the catalytic and thermal cracking of injected oil. We define the Feed Riser Profile as the curve of RMS acceleration along the feed riser and show that changes in its magnitude and shape can be correlated with changes in the product yield of the catalytic and thermal cracking process.
Mean Flow and Turbulent Stress Estimation Using DPIV in Pulsatile Flow Through Mechanical Heart Valve
Authors: Subramanian Amirthaganesh , Mu Haining , Kadambi Jaikrishnan R. , Harasaki Hiroaki , Wernet Mark P.
Published: November 2021

Accurate estimation of turbulent stresses in pulsatile flows is very important in the design of mechanical heart valves to reduce thromboembolism and hemolysis. The flow within the lumen of a fully transparent bileaflet mechanical heart valve model, in the “mitral” position of an in-vitro pulsatile flow loop, is characterized using digital particle image velocimetry (DPIV). A phase-averaging technique is used to obtain the mean velocities and turbulent stresses. The results are compared with those obtained using laser Doppler anemometry which shows good agreement between the two measurement techniques, thereby validating the integrity of the DPIV measurements in the conditionally sampled time dependent flow. Convergence and accuracy issues involving turbulent stress measurements with DPIV in pulsatile flows are addressed in this paper.
Scale Effects on the Non-Newtonian Behaviour of Blood: A Numerical Study
Authors: Sørensen Lotte T. , Rosendahl Lasse A. , Condra Thomas J. , Madsen Jens I.
Published: November 2021

The commonly used assumption that blood behaves as a Newtonian fluid in the large vessels and the heart and as a non-Newtonian fluid in the smaller vessels is questioned in this paper. A numerical simulation of three characteristic vessels (aorta, arterie, and arteriole) in the human cardiovascular system has been carried out using three constitutive equations for human blood. The constitutive equations are proposed by other researchers, one depending on the composition of blood, a general non-Newtonian model, and a Newtonian model. The calculations carried out shows that the prediction of the shear stresses varies with the constitutive equation used, and the deviation is more pronounced for the aorta than for the smaller vessels.
An Eulerian Model for Free-Shear Multiphase Turbulent Diffusion
Authors: Loth Eric
Published: November 2021

A closed-form Eulerian model was constructed for longtime diffusion of heavy or buoyant particles. This model is based on incorporation of experimentally observed turbulent diffusion features: Stokes number, crossing-trajectory, inertial limit, and continuity effects. The anisotropic model was formulated using a Csanady-based approximation for the particle diffusion ratio as equal to the ratio of the particle interaction time to local eddy integral time scale. The model favorably compares with experimental free-shear measurements and numerical Lagrangian turbulent diffusion results for a range of particle density ratios (including solid particles in gas and gas bubbles in liquid). The model for turbulent diffusion effects is suited for inclusion within multi-phase Reynolds-Averaged Navier-Stokes methods which treat the particle distribution as a continuous Eulerian concentration field.
Drag-Reduction and Slip: An Investigation of Size Scale and Hydrophobicity Effects
Authors: Gordon Timothy D. , McCarthy Thomas J.
Published: November 2021

Experiments indicate that hydrodynamic drag may be reduced by using ultrahydrophobic substrates to induce slip at the solid-liquid interface. The connection between drag-reduction and slip is explored, and these previously isolated fields are joined into a single, more comprehensive area of research.

We present data from two experimental techniques indicating the role of hydrophobicity and size scale in drag-reduction. In one series of studies, water was directed through a channel containing two rectangular plates of smooth silicon. Flow rates for smooth non-hydrophobic plates and smooth hydrophobic plates were identical.

In another series of studies, a rheometer was used to measure the relative drag experienced by a polypropylene-coated disk as it was rotated in water. The polypropylene (PP) was ultrahydrophobized (water contact angles were θa/θr = 167°/166°) by argon plasma etching in the presence of poly(tetrafluoroethylene). Drag was reduced by over 20% by using the roughened PP instead of the virgin PP.

Contact angle hysteresis is isolated as a critical factor in the drag-reduction mechanism proposed.
A Laboratory Study of the Velocity Structure in an Intrusive Gravity Current
Authors: Lowe Ryan J.
Published: November 2021

Laboratory experiments were performed in which an intrusive gravity current was observed using shadowgraph and particle tracking methods. The intrusion was generated in a two-layer fluid with a sharp interface by mixing the fluid behind a vertical lock-gate and then suddenly withdrawing the gate from the tank. The purpose of the experiments is to determine the structure of the velocity field inside the intrusion as well as the stability characteristics of the interface. Soon after the removal of the lock-gate the speed of the front of the intrusive gravity current reached a constant speed. The observed structure of the flow inside the intrusion shows a “head region” where the flow is nearly uniform, followed by a region of intense mixing and high velocities and finally followed by another region of fairly uniform velocity with a speed slightly faster than the front speed. The results show that the maximum centerline velocity is about 50% greater than the front speed and corresponds to the position in the intrusion where the strongest Kelvin- Helmholtz billows form. Closer to the front, the relative flow within the head is weak, which explains why Benjamin’s (1968) energy-conserving gravity current theory accurately predicts the behavior of dissipative gravity currents.
A Computational Study on Airfoils at a Low Reynolds Number
Authors: Singh Ajit Pal , Winoto S. H. , Shah D. A. , Lim K. G. , Goh Robert E. K.
Published: November 2021

Performance characteristics of some low Reynolds number airfoils for the use in micro air vehicles (MAVs) are computationally studied using XFOIL at a Reynolds number of 80,000. XFOIL, which is based on linear-vorticity stream function panel method coupled with a viscous integral formulation, is used for the analysis. In the first part of the study, results obtained from the XFOIL have been compared with available experimental data at low Reynolds numbers. XFOIL is then used to study relative aerodynamic performance of nine different airfoils. The computational analysis has shown that the S1223 airfoil has a relatively better performance than other airfoils considered for the analysis.
A Nested-Grid Computational Study of Jets in Crossflow
Authors: Zheng Z. Charlie , Zhang N. , Lim S. H.
Published: November 2021

In this paper, a nested grid technique is used to accommodate the smaller scale structures near the jet hole and the larger structures downstream. Flow physics resolved by the nested-grid computation is discussed in the context of vorticity transport and vortex dynamics. Pitch and skew angle effects of the jet are studied. Quantitative comparisons with available experimental data have been made.
Fluid Flows Through Two-Dimensional Irregular Composite Channels
Authors: Al-Hadhrami A. K. , Elliott L. , Ingham D. B. , Wen X.
Published: November 2021

The present analysis is concerned with the study of two-dimensional fluid flow problems through channels of irregular composite materials. The fluid is assumed to be steady, incompressible, with a negligible gravitational force, and is constrained to flow in an infinite long channel in which the height assumes a series of piecewise constant values. An analytical study in the fully developed section of the composite channel is presented when the channel is of constant height and composed of several layers of porous media, each of uniform porosity. Numerical solutions are utilised using CFD based on the control volume method to solve the Brinkman equation, which governs fluid flow through porous media. In the fully developed flow regime the analytical and numerical solutions are graphically indistinguishable. A geometrical configuration involving several discontinuities of channel height, and where the entry and exit sections are layered, is considered and the effect of different permeabilities is demonstrated. Several numerical investigations which form a first attempt to mathematically model some geological structures, e.g. a fault or a fracture, are performed. Further, flow through fractures composed of randomly generated permeability values are also discussed and the effect on the overall pressure gradient is considered.
Numerical Study of Density-Currents Using the Non-Staggered Grid Fractional-Step-Method
Authors: Pacheco J. Rafael , Pacheco-Vega Arturo , Pacheco-Vega Sigfrido
Published: November 2021

A new approach for the solution of time-dependent calculations of buoyancy driven currents is presented. This method employs the idea that density variation can be pursued by using markers distributed in the flow field. The analysis based on the finite difference technique with the non-staggered grid fractional step method is used to solve the flow equations written in terms of primitive variables. The physical domain is transformed to a rectangle by means of a numerical mapping technique. The problems analyzed include two-fluid flow in a tank with sloping bottom and colliding density currents. The numerical experiments performed show that this approach is efficient and robust.
Railroad Wheel Rotundity
Authors: Van Overveen Joseph P. , Grosser Joseph
Published: November 2021

This paper is based on wheel data collected by the authors at the Bay Area Rapid Transit (BART). The wheel data is examined to determine the rotundity in a new condition and after three levels of accumulated service mileage. Analysis of this data points to the need for investigating Wheel/Rail reaction under various conditions of wheel rail rotundity and rail irregularities.

The authors suggest a method of investigation that should show that the interaction of wheel and rail can result in rail corrugation.
Consolequip Steering Bogie for the Société Nationale Industrielle et Minière ‘SNIM’ de la Mauritanie
Authors: Khatchadourian Varoujan
Published: November 2021

This paper describes in detail the design, engineering and testing conducted for 260 self-steering bogies in response to a bid from SNIM (Société Nationale Industrielle et Minière), in Mauritania, Africa.

Severe environmental conditions in Mauritania, caused by the presence of sand, contribute to accelerated wheel tread wear. This in combination with asymmetric wheel wear typically experienced with the standard three-piece bogie, results in poor wheel life. A steering bogie improves wheel life by allowing the axles to self-align, thus reducing asymmetric wheel wear occurrence.

Bogie behavior is explained by comparing the stiffness characteristics of self-steering bogies and standard three-piece bogies. High bogie stiffness keeps a truck square as it travels on the track, thus improving its dynamic response on tangent track. Split type friction wedges are used together with heavy-duty suspension system to obtain high bogie shear stiffness and vertical damping characteristics. An elastic shear pad between the roller bearings and the side frame pedestal roof allows the axles to self-align in curves, giving the truck its self-steering characteristic.

The truck design is unique as the standard AAR unit guide bracket construction point and angle were changed to provide the alignment for the unique combination of axle spacing and wheel diameter. It utilizes 1000 mm diameter wheels and a wheel base of 1800 mm.

The Consolequip steering bogie has been engineered to improve dynamic response on tangent track. This is done by increasing bogie interaxle shear stiffness which increases the threshold of truck hunting. Stability tests with service worn wheels confirmed stability speed to exceed operating speeds used by SNIM network. Preliminary projections have estimated an improvement of up to 50% in wheel life by reducing asymmetric wheel wear and the number of times they are re-profiled.
Comparing U.S. and European Freight Car Design Specifications: What Can We Learn?
Authors: Richmond Shaun
Published: November 2021

Railroads in the U.S. and Europe have evolved to perform the same functions but have developed different specification and regulatory environments. In the U.S., AAR rules apply while in Europe the UIC code is followed. This paper compares selected parts of both specifications with a view to understanding the differences in philosophy between them and pointing out areas where we in the U.S. might gain from adopting the methods used in Europe.

Clearly, the volume of regulation prohibits a comprehensive review and so discussion is limited to three key areas: Trackability—which includes ride quality and safety from derailment, Structural Integrity and Gauging—the calculation of the maximum permitted profile of the car. It is the author’s belief that improved performance could be obtained from the existing railroad environment by adopting certain UIC methodologies.
The Influence of Acceleration Performance on Throughput and Trip Time of Passenger Trains in High Density Corridors
Authors: Strong Philip M.
Published: November 2021

Studies continue to indicate that acceleration performance has a significant influence on limiting throughput (maximum number of trains per hour per track) and trip time, in service with high density and/or close station spacing.

This paper investigates the influence of horsepower per ton, tractive effort per lb., and maximum speed on throughput and trip time.

The paper presents a methodology which can be used to determine performance (throughput and trip time) as functions of horsepower per ton, tractive effort per lb. and maximum speed. Results are presented, using this methodology, which represent a range of typical operations. Limits on available adhesion, and on practical limits on horsepower per ton achievable with today’s technology and infrastructure, are recognized in the examples.
Effects of Production Variables on Stress-Strain Behavior of Glass/Epoxy Textile Composites in Compression Molding
Authors: Adanur Sabit , Onal Levent
Published: November 2021

The production parameters of glass-reinforced composites have a significant effect on the tensile properties of the material. The effects of manufacturing characteristics such as molding time, molding temperature, molding pressure and mixing ratio of epoxy resin and curing agent on stress and strain values of the composites were examined at the same volume fraction ratio.
Structural Design Applications of the Two-Branch Tournament Genetic Algorithm
Authors: Crossley William A. , Fanjoy David W. , Beaver Angela K.
Published: November 2021

The two-branch tournament Genetic Algorithm (GA) is a population-based search technique that generates a large number of designs to approximate the Pareto-optimal set of designs for problems with two objectives. The two-branch GA can accommodate problems with a mix of discrete and continuous design variables and problems with discontinuous and/or multimodal objectives. The two-branch GA was applied to several multiobjective structural design problems: a ten-bar truss, Golinski’s speed reducer, a multi-material ten-bar truss, and a stiffened composite panel. Where possible, GA results were compared to traditional multiobjective optimization results. The two-branch GA appears to have advantages over traditional approaches for problems with non-smooth Pareto fronts and / or combined variable types. The studies led to conclusions about the two-branch GA for multiobjective structural design.
Optimum Design of Turbomachinery Components: A System Based Design
Authors: Nagendra Somanath
Published: November 2021

The advent of incredibly fast, increased memory computational systems enable a very systematic design integration of complex engineering modules using an integrated system based approach. Rapid turn-around time for investigating new design concepts is a primary force driving design productivity initiatives across industry. A system based integration focusing on tools for rapid design automation and preliminary design, (e.g. Closed Form Solutions, Response Surfaces, Approximate Numerical Models etc), finite element analysis coupled with optimization methods are needed.

Numerical design algorithms (e.g. Sensitivity analysis methods, Feasible Direction methods, Genetic Algorithms, Simulated Annealing, Gradient based Algorithms etc.) at the preliminary and detailed design stages, would ensure higher quality designs from the beginning of the product design cycle. Resulting reliable, robust optimum designs from the preliminary design phase would enable to reduce the overall design cycle time.

Large-scale engineering systems (like the gas turbine See Figure. 1) often involve many disciplines which are either loosely or tightly coupled to each other due to the multidisciplinary nature of the interactions. Designers have long recognized the need to decompose such systems into a set of smaller more tractable disciplines. This decomposition is usually based either on engineering disciplines or mathematical models governing the system. Narayan et al. [1] developed a multi-disciplinary design optimization procedure for the design of the aerodynamic shape of turbine blades for enhanced performance using shape optimization techniques.

A multidisciplinary design optimization procedure for thin-walled high temperature components has been developed and demonstrated on different components Aerodynamic, heat transfer, structural and modal design objectives are integrated along with various constraint on the blade geometry for multidisciplinary shape optimization. The average blade temperature, maximum blade temperature and the blade weight are minimized with aerodynamic, structural, modal and geometric constraints. A methodology for performing mechanical design of turbine blade components is developed and tested.
Chaotic Motions in Resonant Separatrix Bands of a Parametrically Excited Pendulum
Authors: Luo Albert C. J.
Published: November 2021

The analytical conditions for the presence of primary (2M:1)-librational and (M:1)-rotational, resonant bands in a parametrically excited pendulum are obtained. The energy increment spectrum method is also developed for the numerical prediction of a specific primary resonant band. Illustrations of the analytical and numerical results for the appearance and destruction of the resonant bands are given for a comparison.
A Study on Boundary Integral Equation for Acoustic Radiation From Axisymmetric Bodies
Authors: Liu G. R. , Cai C. , Zheng H. , Lam K. Y.
Published: November 2021

A technique named the RDT (Reproduction of Diagonal Terms) is presented to improve the accuracy and the reliability of Conventional Boundary Integral Equation (CBIE) applied to acoustic radiation from axisymmetric bodies. In CBIE, the higher order singular integral is eliminated by placing a fabricated point source inside the boundary. Numerical results for a spherical structure show that the accuracy is obviously raised up to 10 times at higher frequency upon use of the RDT method, and the CHIEF and improved Burton & Miller methods can work with the technique presented in a wide frequency range with better accuracy.
FEM/BEM Simulation of Vibroacoustics of a Fluid-Loaded, Stiffened Plate Under Combined Force-Moment Excitation
Authors: Zheng H. , Cai C. , Liu G. R. , Lam K. Y.
Published: November 2021

A numerical simulation of structural vibration and acoustic radiation is presented for a finite, fluid-loaded plate reinforced with two sets of orthotropic stiffeners. The attempt is to achieve a physical understanding of the dynamic behaviour and especially the acoustic radiation of the stiffened plate under combined force and moment excitations. Finite element method (FEM) is employed for calculation of the in-vacuo normal modes of the stiffened plate. The coupled modes with a heavy fluid (water), vibration response and acoustic radiation of the plate under given force and/or moment excitation are calculated using boundary element method (BEM). Numerical simulation results are detailed to address the significance of moment in combined force-moment excitations and, more importantly, the cancelling of the combined excitation in both structural vibration response and the associated acoustic radiation into the surrounding fluid.
Adaptive Learning Algorithm for Cerebellar Model Articulation Controller: Neural Network Based Hybrid-Type Controller—Part I
Authors: Abdelhameed Magdy Mohamed , Cetinkunt Sabri
Published: November 2021

Cerebellar model articulation controller (CMAC) is a useful neural network learning technique. It was developed two decades ago but yet lacks an adequate learning algorithm, especially when it is used in a hybrid- type controller. This work is intended to introduce a simulation study for examining the performance of a hybrid-type control system based on the conventional learning algorithm of CMAC neural network. This study showed that the control system is unstable. Then a new adaptive learning algorithm of a CMAC based hybrid- type controller is proposed. The main features of the proposed learning algorithm, as well as the effects of the newly introduced parameters of this algorithm have been studied extensively via simulation case studies. The simulation results showed that the proposed learning algorithm is a robust in stabilizing the control system. Also, this proposed learning algorithm preserved all the known advantages of the CMAC neural network. Part II of this work is dedicated to validate the effectiveness of the proposed CMAC learning algorithm experimentally.
Multi-Sensor Fusion for Robot Positioning Based on Dempster-Shafer Methods
Authors: Qu Weidong , Jing Zhongliang , Xi Yugeng
Published: November 2021

This paper presents a high-performance positioning module for the mobile robot. The mobile robot is equipped with the internal and external sensors. Internal sensors are the acceleration gyroscopes. The positioning system makes use of the features of the external sensors to improve its performance: laser rangefinder ultrasonic sensors and video sensors, which were originally designed for mapping and obstacle avoidance modules, the positioning modules has demonstrated the system to work successfully in complex and uncertainty environments.
Effect of Curved Boundaries of an Intravenous Membrane Oxygenator on the Fluid Dynamics and Mass Transfer Characteristics
Authors: Guzmán Amador M. , Escobar Rodrigo A. , Amon Cristina H.
Published: November 2021

The Intravenous Membrane Oxygentor (IMO) device is an artificial respirator being developed at the University of Pittsburgh Medical Center (UPMC) with the objective of providing up to 50% of the O2 and CO2 exchange requirements to patients with the Acute Respiratory Distress Syndrome (ARDS) [1-4]. In-vitro and in-vivo experiments and computational simulations at the UPMC and Carnegie Mellon University (CMU), respectively, have been carried out to get a better understanding of the flow and mass transfer characteristics of the IMO [3,4, 7-11]. Numerically obtained pressure drop, for stationary and pulsating balloon conditions, presents a good agreement with the in-vitro experiments [4, 11]. The effect of the balloon pulsation on the flow pattern and mass transfer has also been investigated. Numerical results with a stationary balloon demonstrate a laminar flow regime with no secondary flows [10-11]. These results have indicated that the pulsating balloon generates a 3D oscillatory flow with a strong secondary flow that could increase the flow mixing and the mass transfer rate near the fibers [9-10]. These simulations however, have not considered the curvature of both the fibers and balloon and their effect on the flow mixing and mass transfer characteristics. This article reports numerical investigations of the effect of the curved shape of the balloon on the flow and oxygen transfer pattern of the IMO device shown in Fig. 1(a), for stationary and pulsating balloon regimes.