bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling Flow Properties in Biofluids
Authors: Kee Daniel De , Sun Ning
Published: November 2021

Biofluids such as blood, as well as other structured materials, exhibit rather complex rheological behavior. In this paper, starting from a first order kinetic model introduced by Soong et al., we developed a constitutive equation and studied its applicability to model biofluids. In particular, we studied the cases of steady shear flow, hysteresis, yield stress and small amplitude oscillatory flow. Model predictions were successfully compared with experimental data on complex materials such as blood and a penicillin suspension.
Functional Macroporous poly(dicyclopentadiene)
Authors: Della Martina A. , Hilborn J. G.
Published: November 2021

The synthesis and processing of functional macroporous poly(dicyclopentadiene) is addressed in this paper. The basic principle of chemically induced phase separation, which can produce either closed or open pore materials, is described. The produced materials showed narrow pore size distributions and micrometric average access diameters. Linearity between the initial porogen contents and the final porosity was observed, allowing easy tailoring of the final materials. The wide possibilities of this technique are presented. Porous monoliths as well as porosity gradient rods and porous microspheres have been produced. Pore sizes distributions modification as well as surface functionalization have also been performed.
Flow-Forces Effect on the Behavior of an Open Center Hydraulic Distributor
Authors: Borghi M. , Milani M. , Sedoni E.
Published: November 2021

The effect of steady-state axial flow-forces on the motion of an open center hydraulic distributor notched spool is considered.

More in details, the spring driven spool centering is considered, in which undesired axial flow-forces could overcome the spring action.

A steady-state analysis of the forces influencing the spool motion is reported, calculating the axial flow-force for different positions of the spool.

Different notched shapes of the metering edge are considered, and an optimized solution for the notched edge of the spool is proposed at last.
Elastic-Plastic Behavior of Filamentary Networks
Authors: Baesu Eveline
Published: November 2021

The finite elastic-plastic deformation of thin sheets formed by several families of perfectly flexible extensible fibers is described using an idealized theory in which fibers are assumed to be continuously distributed and fastened together at nodes which deform as material points. The constitutive properties of the associated surface are deduced directly from those of the constituent fibers. An incremental formulation of the equilibrium equations for two families of fibers is presented and used to generate extremum principles based on primary bounds on the exact global force-deflection response.
Plane Steady Flows of Dilute Magnetic Fluids
Authors: Venkatasubramanian S. , Kaloni P. N.
Published: November 2021

In this article, steady plane flows of dilute magnetic fluids are studied. A solution procedure for a general flow is developed using transformation techniques. Macroscopic effects due to the rotation of the suspended particles are taken into account, while neglecting their diffusion. Effectiveness of this method is illustrated by solving two rectilinear flows in different coordinate systems. In an uniform applied magnetic field, the magnetic torque displays itself as an apparent viscosity affecting the flow of a dilute magnetic fluid. Importance of not neglecting the particle rotation effects are shown by comparing the results with that of the corresponding equilibrium model.
Spatial Discretization of Axially Moving Media Vibration Problems
Authors: Jha Rajesh K. , Parker Robert G.
Published: November 2021

Spatial discretization of axially moving media eigenvalue problems is examined from the perspectives of moving versus stationary system basis functions, configuration space versus state space form discretization, and subcritical versus supercritical speed convergence. The moving string eigenfunctions, which have previously been shown to give excellent discretization convergence under certain conditions, become linearly dependent and cause numerical problems as the number of terms increases. This problem does not occur in a discretization of the state space form of the eigenvalue problem, although convergence is slower, not monotonic, and not necessarily from above. Use of the moving string basis at supercritical speeds yields strikingly poor results with either the configuration or state space discretizations. The stationary system eigenfunctions provide reliable eigenvalue predictions across the range of problems examined. Because they have known, exact solutions, the moving string on elastic foundation and the traveling, tensioned beam are used as illustrative examples. Many of the findings, however, apply to more complex moving media problems, including non-trivial equilibria of nonlinear models.
Failure of Foam Core Sandwiches: Numerical Simulation by Microplane Model
Authors: Bažant Zdeněk P. , Brocca Michele
Published: November 2021

The paper presents a new constitutive model for closed-cell polymeric foams. The model is of the microplane type. In this model, the constitutive law is characterized in terms of vectors rather then tensors. The conceptual simplicity of this ‘first-principles’ approach makes it possible to base the model more directly on the physical phenomena occurring in the microstructure, in this case the elastic bending of the cells idealized as spheres in contact. The model is then employed in a finite element analysis of three point bending tests of sandwich beams failing by core indentation. Good agreement of the numerical results with the experimental observations is achieved. The softening and size effect engendered by the reduction of tangential bending stiffness due to the geometrically nonlinear effect of core indentation is discussed.
Comparative Study of Two Different Conceptual Design Principles for Non-Circular Pressurized Sandwich Fuselage Sections Using a High-Order Sandwich Theory Formulation
Authors: Thomsen Ole T. , Vinson Jack R.
Published: November 2021

Results obtained as part of a design study regarding a non-circular pressurized sandwich fuselage section are presented. The originating problem is associated with preliminary studies for the “Global Range Transport” envisaged by the “New World Vistas” program of the United States Air Force. The modeling and analysis is conducted using a high-order sandwich theory formulation in which the elastic response of each face laminate is accounted for, including bending-stretching coupling and transverse shear deformations, and where the transverse flexibility of the core is included. The sandwich fuselage envisaged may contain flat, tapered and curved sandwich elements, and a high-order sandwich theory formulation is developed to analyze each of these configurations. The paper includes a brief presentation of the adopted high-order sandwich theory with special emphasis on the application for the analysis of sandwich panels with variable core thickness, and for the analysis of curved sandwich panels. Numerical results obtained for two different mid-plane asymmetric fuselage sections are presented and compared; one with constant core thickness, and one with varying core thickness.
High-Order Analysis of Unidirectional Sandwich Panels With Flat and Generally Piecewise Curved Faces and a “Soft” Core
Authors: Rabinovich Oded , Frostig Yeoshua
Published: November 2021

The bending behavior of a unidirectional sandwich panel with flat and generally piecewise curved faces and a flexible core in the vertical direction is investigated. The studied panels consist of an upper flat face sheet, a core of a variable thickness, and a lower face sheet that can take any geometrical layout described by a piecewise analytical function. The core is assumed to be a two-dimensional elastic medium with vertical and shear rigidities only, and the faces are considered to have membrane and bending rigidities and are made of metallic or composite materials. The field equations and the boundary conditions are rigorously derived using the variational principle of virtual work. The continuity conditions between the various regions of the generally piecewise curved face are presented. Higher order effects in the form of nonlinear deformation distributions through the thickness due to flexibility of the core are incorporated in the proposed analysis. Numerical results in terms of deformations, stresses, and stress resultants are presented for some typical cases of piecewise flat-curved panels. The results demonstrate the capabilities and generality of the proposed model, especially in the ability to predict the high-order localized effects and the high stress concentrations that characterize these panels.
Implication of Anisotropy of Face-Sheets and Core Layer Materials on the Load Carrying Capacity of Advanced Sandwich Panels: Linear and Nonlinear Responses
Authors: Librescu Liviu
Published: November 2021

This paper deals with a comprehensive geometrically nonlinear theory of shallow sandwich shells that includes also the effect of the initial geometric imperfections. It is assumed that the face-sheets of the sandwich structure are built-up from anisotropic materials layers, whereas the core layer from an orthotropic material. As a result of its features the structural model can provide important information related to the load carrying capacity of sandwich structures in the pre- and postbuckling ranges. Moreover, by using the directionality properties of face-sheets materials, possibilities of enhancing the load carrying capacity of sandwich shells/plates are reached. Selected numerical illustrations emphasizing these features are presented and pertinent conclusions on the beneficial implications of anisotropy of face-sheets and core layer materials upon the load-carrying capacity of sandwich panels are emphasized.

Under the present study, the sandwich structure consists of a thick core-layer bonded by the face-sheets that consist of composite anisotropic materials, symmetrically laminated with respect to the mid-surface of the core-layer. The initial geometric imperfection consisting of a stress free initial transversal deflection, will be also incorporated in the study. The loads under which the nonlinear response will be analyzed consist basically of uniaxial/biaxial compressive edge and lateral loads.
A Novel Micro Capacitance Sensor for Studying Hydrodynamics of Particle Laden Flow
Authors: Pokusevski Z. , Evans I. G. , York T. A. , Dyakowski T.
Published: November 2021

Particle laden flows occur in a wide range of industrial applications. Detection of dispersed particles and drops is of enormous importance since they may cause “erosion-corrosion effects” in industrial equipment. This paper presents a novel technique for particle detection. The results show 20 and 50 micron particles detected in the static tests. CFD simulations were carried out in order to design the sensor mounting and its optimal inclination to the flow. It was shown that sensor inclination of 5 or 10 degrees to the flow is highly beneficial. Dynamic tests were carried out and the full results show good agreement with the predicted particle tracks. 50 and 20 micron polyamide particles were detected at air velocities up to 12 metres per second.
Simulation of Evaporating Spray and Comparison With Droplet Temperature Measurement Obtained by Rainbow Refractometer
Authors: Gemci Tevfik , Hom James , Chigier Norman
Published: November 2021

Both experimental and computational work are important in the study of spray evaporation and combustion; therefore, it is essential that a link between the two areas be established. In this study, measurements of a full cone spray using phase-Doppler interferometry and Rainbow Refractometry are presented and compared with computational results. The computation results were acquired using a KIVA-3V code, which is specifically designed to analyze transient, two- and three-dimensional, chemically reactive fluid flows with sprays.

Specifically, in this study, the droplet size, velocity and temperature distributions were measured at various locations within the full cone spray. Using the same initial and boundary conditions, computation results were obtained at corresponding locations and compared with the experimental results. The experimental and computational results agree very well and indicate similar droplet size, velocity and temperature distributions at the corresponding locations. Additionally, the cooling rates and movement of the droplets show the same trends.
Atomization of Liquid by Two-Phase Gas-Liquid Flow Through a Nozzle
Authors: Lörcher M. , Mewes D.
Published: November 2021

A liquid or a suspension is divided into small droplets by atomization. The mean goal is either the equal distribution of the droplets, or the generation of large surface areas of the liquid phase in order to increase heat- and mass-transfer. In two-phase atomization the spatial and time distribution of the mean droplet diameter of the spray depend on the total pressure upstream of the nozzle, the volumetric flow rate of the liquid and the gas, as well as on the flow regime in the nozzle. Thus the radial and axial profile of the void fraction inside the nozzle are measured with an electrical measurement technique. In addition, the flow in the nozzle is visualized by a high-speed camera. Three flow regimes are identified. These are bubbly flow, plug flow, and annular flow.

At the smallest cross section of the nozzle critical mass flow is observed. A literature review on models to calculate the critical mass flow is given. The calculated and the measured mass flow rates are compared.
Pressure Drop Fluctuation and Flow Regime Identification for Air-Water Two-Phase Flow
Authors: Bai Bofeng , Wu Tiejun , Guo Liejin , Chen Xuejun
Published: November 2021

The fluctuating pressure drop for air-water two-phase flow was measured in the vertical upward section of U-type tube with 0.05m I.D. The feature of the fluctuations was extracted by means of statistical and chaotic theories. The influence of liquid superficial velocity on the features was also investigated. The results showed that the mean, root mean square, fractal dimension of pressure drop fluctuations is function of flow regimes. The fractal dimension can be larger than 1.5 in annular flow with great liquid superficial velocity which is reported for the first time. Furthermore, the present paper provided a feasible solution, which the gas-liquid two-phase flow regimes can be recognized automatically and objectively on basis of the combination of the Counter Propagation Network (CPN) and the FFT coefficients of the differential pressure fluctuations. The recognition possibility is determined by the clustering results of the Kohonen layer in the CPN. With the presented test cases, the possibility can be greater than 90 percent for different liquid phase velocity.
Segregation During Magnetically-Stabilized Liquid-Encapsulated Growth of Compound Semiconductor Crystals
Authors: Ma Nancy , Bliss David F. , Bryant George G.
Published: November 2021

During the magnetically-stabilized liquid-encapsulated Czochralski (MLEC) process, a single compound semiconductor crystal is grown by the solidification of an initially molten semiconductor (melt) contained in a crucible. The melt is doped with an element in order to vary the electrical and/or optical properties of the crystal. During growth, the so-called melt-depletion flow caused by the opposing relative motions of the encapsulant-melt interface and the crystal-melt interface can be controlled with an externally applied magnetic field. The convective dopant transport during growth driven by this melt motion produces non-uniformities of the dopant concentration in both the melt and the crystal. This paper presents a model for the unsteady transport of a dopant during the MLEC process with an axial magnetic field. Dopant distributions in the crystal and in the melt at several different stages during growth are presented.
Investigation of Heat Transfer in a Building Integrated Photovoltaic System
Authors: Zhu Zuojin , Yang Hongxing , Wu Qingsong
Published: November 2021

Heat transfer in a building integrated photovoltaic (BIPV) system has been investigated experimentally and numerically. A mathematical model is proposed for the numerical prediction, where an alternative of temperature, the cumulative variable, is defined as a temperature integration along the wall height of the BIPV system. The system which was consisted of eighteen west facing BP PV panels and a heavy concrete wall was experimentally studied to measure the electricity generation rate and thermal regulation effects. The eighteen PV panels were arranged in three modes and installed on the building wall with an thermal regulation gap, which enables natural convection for the ventilation of the PV panels. The experiments were controlled by a computer, so that data from sensors can be collected and recorded by a data logger automatically. However, the instantaneous outdoor wind speed was estimated by the Discrete Hillbert Transformer with sample input selected from the data observed by the Observatory in Hong Kong in June of 1989. The measured results of four days from the twelfth to sixteenth of June in 1999 had been compared with the numerical results. It is found that the maximum of the average temperature of PV panels has exceeded 50°C, but the maximum conversion efficiency of solar energy is less than 10%, close to 6.76%. A good agreement has been obtained between the measurements and predictions for the four days of investigation. It is concluded that the model for heat transfer analysis could be applied for the long term run of this BIPV system.
A New Approach for Large Non-Linear Integer Optimization Suitable for Implementation on a Distributed Collection of Computers
Authors: Nickel Ronald H. , Mikolic-Torreira Igor , Tolle Jon W.
Published: November 2021

We present a new methodology called Multi-Indenture, Multi-Echelon Readiness-Based Sparing (MIMERBS) for solving large, non-linear integer optimization problems that arise in determining the retail and wholesale sparing policies that support the aircraft operating from a deployed aircraft carrier. MIMERBS determines the minimum cost mix of spare parts that meets required levels of expected aircraft availability. The size (thousands of variables), the nonlinear relationship between spare parts and aircraft availability, and the requirement that the variables be integers make this problem hard.

We provide a concise description of the MIMERBS model and present data to show how it improves on earlier sparing models. This improvement comes at the price of significant computationally complexity, which in turn makes the optimization problem hard to solve.

We describe how we integrated an interior point method with a direct search algorithm to solve this optimization problem. This hybrid algorithm is well suited for implementation on a home-made virtual super-computer made up of several dozen Windows NT computers connected by an office LAN. A description of the virtual super-computer is given in a separate paper. We report on three specific cases we solved using the MIMERBS model, having from 1,000 to 8,000 optimization variables.
A “Boundary Layer” Method for Obtaining an Approximate Equation for the Unsteady Velocity-Time History of Flow Startup in a Pipe
Authors: Janna William S. , Hochstein John I.
Published: November 2021

An incompressible fluid volume is initially at rest in a pipe. A valve is suddenly opened and the fluid accelerates from rest to the steady state velocity. The equation describing the accelerating motion is a first order nonlinear equation containing friction, pressure drop and kinetic energy terms. The solution to this equation yields a relationship between average velocity and time. The traditional solution method involves assuming friction factor is a constant, and equal to the steady state value. The equation can be solved numerically using a difference scheme, which does not involve assuming a constant friction factor. In this study, a method of generating a velocity-time equation in polynomial form is developed to obtain an alternative solution. The method is used to solve two specific examples and the results obtained are compared with the numerical solution method. The comparison yields a small error, and so the polynomial approximation method can be used as an alternative technique to describe the motion of an accelerating fluid volume.
Railroad Vehicle Glazing Standard Development
Authors: Lamond James H. , Liao Sam S. C.
Published: November 2021

The American Public Transportation Association’s (APTA) Passenger Railroad Equipment Safety Standard (PRESS) Task Force initiated a testing program to develop a new railroad vehicle glazing standard. The program was coordinated and funded through the Federal Railroad Administration (FRA). This paper presents the procedures and results of this testing program. The test program used an air cannon to project various sizes of steel balls at speeds between 30 and 125 miles per hour and a 24-pound cinder block at 30 miles per hour to impact different glazing samples (glass laminates and polycarbonates) in the vertical position with the impactors striking at 90 degrees to the samples. With the cinder block, the impacts had to occur between the corner of the block and the samples. A pendulum system was used to impact the samples at slower speeds. The ballistic tests consisted of a 0.22-caliber long rifle, 40-grain bullet at speeds between 960 and 1163 feet per second. The pass/fail criteria were dislodgment of the glazing from the frame, or spall penetrating one mil aluminum foil witness plate placed 6 inches behind the samples. Based on this test program and input from the rail industries, a new glazing standard was developed.
Nonlinear Behavior of Sandwich Panels With Delamination Inside Face Sheets Based on Refined Higher Order Core Theory
Authors: Li R. , La Saponara V. , Kardomateas G. A.
Published: November 2021

Sandwich construction, consisting of two stiff face sheets and a soft core of a foam or low strength honeycomb type while designed principally as efficient integral structures, can lose this quality when delaminations occur inside the face sheets, especially under compressive loading condition. A refined higher order core theory is developed for the core that accounts for the nonlinear distortion of the plane of section of the core and the compressibility in the vertical direction, and for the skins in which part of the transverse deflections is related to the core nonlinear distortion. Based on this core theory, nonlinear behavior of sandwich beams/panels with delaminated faces is studied. The nonlinear governing equations, boundary conditions, and continuity conditions are formulated for the compressed sandwich structure which includes initial imperfection and delamination in the face sheets. Solution arc length parameterization within Newton continuation method is employed in solving the bifurcation and nonlinear eigenvalue problems for critical loads and postbuckling behavior of the sandwich structure. The results suggest that delaminations inside face sheets have considerable influence on the global and local behavior of the whole sandwich con structure.
A New Approach for the Numerical Integration of Nonlinear Dynamic Systems
Authors: Zheng Zhao Chang , Su Zhi Xiao , Han Ray P. S. , Xu Zefang
Published: November 2021

In this paper, the exact solution of a linearlized equation is employed as initial conditions for the next timestep in the numerical integration of the end displacement and velocity. This exact solution is calculated by means of the Duhamel integration. The system equations are satisfied continuously and not discretely as done traditionally. The essential difference of the present method from other works is that the performance of dynamics systems can be traced continuously. Comparisons between the proposed method with traditional techniques are presented. Examples investigated include the large amplitude nonlinear vibration of a simple pendulum of a conservation system, the period of vibration and chaos in the forced vibration of the Duffing oscillator and forced vibration of the van der Pol oscillator of a non-conservation system. The results obtained indicate that the accuracy of the proposed method supersede that of the traditional techniques.
Modal Analysis in Coupled Vibration of Serpentine Belt Drive System
Authors: Zu Jean W. , Zhang Lixin
Published: November 2021

The modal analysis of linear prototypical serpentine belt drive systems is performed in this study. The entire system is divided into two subsystems: one with a single belt and its motion is not coupled to the rest of the system in the linear analysis; the other with the remaining components. The explicit exact characteristic equation for eigenvalues is derived, which does not use the iteration approach. The response of serpentine belt drive systems to arbitrary excitations is obtained as a superposition of orthogonal eigenfunctions. The exact solution without using eigenfunction expansion is derived when the excitations are non-resonance harmonic.
Finite Element Simulation of Damage in Dynamically Loaded Weldments
Authors: Moraes Ricardo , Nicholson David
Published: November 2021

The main goal of the current investigation is to accommodate combined damage softening and thermal softening in structures that experience ductile fracture [1] due to an impulsive loading. A constitutive model first introduced by Johnson-Cook [2], which is sensitive to strain rate effects and temperature softening, is extended to explain the proposed idea. Equations are derived through continuum mechanics theory. Continuum Damage Mechanics (CDM) was first introduced by Kachanov [3] during the fifties. Since then, the topic has been under development by many authors.

Numerical simulations are performed in the explicit finite element impact code LS-DYNA [4]. Constitutive equations for a viscoplastic model with damage and thermal softening are implemented in the code using a User Defined Subroutine UMAT. The Continuum Damage Mechanics (CDM) model is based on the Bonora formulation [5]. The combined material model, named UMAT 41, is added to the program static library using Digital Visual Fortran (FORTRAN 90). Using the User Defined Material, the solution of an explosive charge and of projectile impact applied to a ring-stiffened welded structure is analyzed to predict fracture.

Ring-stiffened structures are widely used in ships, submarines and aircraft, which are subject to explosive or projectile attack. Results obtained using models with and without damage softening agree very well with previously published data with respect to crack paths. However, the time histories and thresholds are sensitive to the model used [6]. Projectile impact is also presented in this work.
Nonuniform Temperature Distribution in Electronic Devices Cooled by Flow in Parallel Microchannels
Authors: Hetsroni G. , Mosyak A. , Segal Z.
Published: November 2021

We fabricated a novel thermal microsystems (simulating a computer chip) consisting of a heater, microchannels, inlet and outlet plena and we studied the effect of the geometry on the flow and heat transfer. The vapor - water two-phase flow patterns were observed in the parallel microchannels through a microscope and high-speed video camera. It was observed that hydraulic instabilities occur. Existence of a periodic annular flow was also observed, which consist of a symmetrically distributed liquid ring surrounding the vapor core. Along the microchannel axis, the periodic dry zone appears and develops. The thermal visualization and temperature measurements of the heated device were carried out using infrared thermography. As long as the flow was single phase liquid, the forced convection heat transfer resulted in a moderate irregularity on the heated chip. These temperature differences do not cause damage to the device. The steady-state heat transfer for different types of microchannels has been studied also at the range of heat flux where phase change of the working fluid from liquid to vapor took place. Under conditions of flow boiling in microchannels, a significant enhancement of heat transfer was established. In the case of uniform heat flux the hydraulic instabilities lead to irregularity of temperature distribution on the heated chip. In the case of nonuniform heat flux the irregularity increased drastically.
Thermal-Mechanical Analysis of an NCA Type of Chip-on-Glass Assemblies
Authors: Cheng Hsien-Chie , Lee Ming-Hsiao , Chiang Kuo-Ning , Chang Chung-Wen
Published: November 2021

Since the electrical conduction in the COG assembly using a non-conductive adhesive takes place through the connection of the bump and the electrodes, the contact resistance can be applied to the evaluation of the design quality as well as the overall reliability of the particular assembly. It should be further noted that as reported in the literature (e.g., see Liu, 1996; Kristiansen et al, 1998; Nicewarner, 1999; Timsit, 1999), the contact resistance between the bump and the electrode on the substrate strongly depends on the contact stress and the contact area. A higher reliability of the packaging somewhat relies on better contact stability as well as larger bonding stresses.

In order to explore the physical contact behaviors of a non-conductive adhesive type of COG assemblies, the contact pressure during manufacturing process sequences and during the temperature variation are extensively investigated using a three-dimensional nonlinear finite element model. The so-called death-birth simulation technique is applied to model the manufacturing process sequences. The typical COG assemblies associated with two types of micro-bumps that are made of different materials: metal and composite are considered as the test vehicle. The contact stress between the electrode and the bump is extensively compared at each manufacturing sequence as well as at elevated temperature in order to investigate the corresponding mechanical interaction. Furthermore, the adhesion stresses of the adhesive are also evaluated to further investigate the possibilities of cracking or delamination within the adhesive and in its interfaces with the die and with the substrate. At last, a parametric finite element model is performed over number of geometry/material design parameters to investigate their impact on the contact/adhesion stresses so as to attain a better reliability design.
Interfacial Versus Cohesive Failure on Underfill-Aluminum Interface: Effects of Interface Roughness
Authors: Yao Qizhou , Qu Jianmin
Published: November 2021

This paper is concerned with the interfacial adhesion and failure of underfill materials in flip-chip packages. Debonding of polymer-metal interfaces often involves both interfacial and cohesive failure. Since the cohesive strength of polymers is usually much greater than the polymer-metal interfacial strength, cohesive failure near the interface is usually desired to enhance the interfacial adhesion. Roughened surfaces generally produce more cohesive failure, therefore, are used commonly in practice to obtain better adhesion. In this paper a fracture mechanics model is developed that can be used to quantitatively predict the amount of cohesive failure once the surface roughness data are given. An epoxy/Al interface was investigated using this fracture mechanics model. The predicted amount of cohesive failure as a function of surface roughness compares very well with the experimentally measured values. It is believed that this model can be extended to other polymer – metal interfaces.
Mathematical Model for Thermostatic Expansion Valve
Authors: Ding Yiwu , Agonafer Dereje , Schmidt Roger
Published: November 2021

A methodology to generate the mathematical model to simulate the steady-state operation of the thermostatic expansion valves is described. Such a model is necessary in understanding the operation of a refrigeration system used in cooling electronics. The model treats the mutual dependence between the valve’s throttling and control functions, and requires a few experimentally determined parameters. Specifically, the characteristic of the valve changes with the evaporating temperature, and a simple model to represent this influence on the valve is suggested.
Musculoskeletal Modeling Using a Bond Graph Approach
Authors: Wojcik Laura A.
Published: November 2021

The dynamic effects of muscle strength, timing of muscle activations, and body geometry have been modeled for a wide variety of human activities. These types of models require the development of complex system equations that account for the effects of rigid-body dynamics, musculotendon actuators, passive and active resistance to motion, and other physiological structures. One way in which model refinement can be expedited is through the use of bond graph modeling techniques. While bond graph techniques have been used extensively in a broad variety of applications, they have been used only sparingly in the field of biomechanics, despite the potential suitability of a modular, multidomain approach to the modeling of musculoskeletal function. This modular approach to dynamic systems modeling is particularly useful in an educational setting, where it allows students to fully understand interactions among the components of complex multidomain systems. In the current paper, bond graph modules representing muscle function and rigid-body motions of underlying bone structures are introduced. These modules can be used in conjunction with control models of neuromuscular function for the simulation of overall dynamic motor performance.
A Sensor Fusion Method for a Network of Highly Autonomous Sensors
Authors: Figueroa Fernando , Yuan Xiaojing
Published: November 2021

To date, data fusion and sensor management systems have largely been implemented with centralized and hierarchical architectures. Numerical and statistical methods are the most common data fusion methods found in these systems. Some recent research has taken on distributed and decentralized systems, while there are other efforts that try to apply qualitative reasoning. However, little has been done to apply qualitative reasoning as an inference mechanism in distributed and decentralized systems. Based on other work by the authors, a sensor may be treated as a highly autonomous (decentralized) unit. In this context, this paper describes a distributed sensor-data-fusion theory based on a qualitative theory to interpret measurements, and on qualitative procedures to reason and make decisions based on the measurement interpretations. In this manner, fusion is done at a high-qualitative level, thus making it possible the implementation of intuitive (effective) methods to monitor, diagnose, and compensate processes/systems and their sensors.
Recognition and Tracking of Large Seam Based on Robotic Vision
Authors: Yue Hong , Sun Lixin , Li Kai , Shi Jianru
Published: November 2021

For the seams of large Structure, the low accordance of joint openings usually results in displacement of the real welding track from the robot teaching track, which will affect the welding quality of the structure. It has very important meanings to apply robotic vision for recognizing the feature parameters of the weld joints. A set of seam tracking system is presented. In order to remove arc noise, the methods of LOG filter and image segment filter are used in image processing.
Output Feedback Adaptive Robust Control of Linear Motors With Negligible Electrical Dynamics
Authors: Xu Li , Yao Bin
Published: November 2021

This paper studies high performance robust motion control of linear motors that have a negligible electrical dynamics. A discontinuous projection based adaptive robust controller (ARC) is constructed. Since only output signal is available for measurement, an observer is designed to provide exponentially convergent estimates of the unmeasurable states. This observer has an extended filter structure so that online parameter adaptation can be utilized to reduce the effect of the possible large nominal disturbance. Estimation errors that come from initial state estimates and uncompensated disturbances are effectively dealt with via certain robust feedback at each step of the ARC backstepping design. Theoretically the resulting controller achieves a guaranteed transient performance and a prescribed final tracking accuracy. In the presence of parametric uncertainties only, asymptotic output tracking is also achieved. This scheme is implemented on an epoxy core linear motor. Extensive experimental results are presented to illustrate the effectiveness and the achievable control performance of the proposed scheme.
Automated Speed Controller Design of Internal Combustion Engines via Adaptive Control
Authors: Cunningham Patrick J. , Franchek Matthew A. , Glass John W.
Published: November 2021

Presented in this paper is an adaptive control procedure applied to the idle speed control of an internal combustion (IC) engine. Adaptive control in this investigation is used to automate the design of the engine idle speed controller. The adaptive control process begins by tuning a feedback controller such that the closed loop system is stable. Next, reference step inputs are given to the tuned closed loop system. These transients are used to obtain a model of the IC engine between the by-pass air valve and engine speed. The online modeling procedure is constructed of a filtered derivative method so that the coefficients of the continuous-time model are recovered from the closed loop response. The execution of the proposed online modeling technology is realized using a recursive least squares approach. This online model of the engine process is then used to calculate a new (adapted) feedback controller. The adaptive controller is based on matching the open loop transfer function of the idle speed feedback system to an open loop transfer function that represents the desired transient and steady state performance. To implement the adapted controller, a bumpless transfer approach is used to switch the feedback controller from the tuned controller to the adapted controller. Experimental results performed on a Ford 4.6L fuel injected engine demonstrate the automated controller design process.
An Adaptive Pressure Servo-Control Design for Variable Displacement Pumps
Authors: Du Hongliu , Manring Noah D.
Published: November 2021

In this paper, a new pressure control scheme for a variable displacement pump is proposed under the consideration of various system uncertainties. The control design reported in this paper provides an effective approach for controlling the discharge pressure of variable displacement pumps to asymptotically track the desired pressure time history. With the provided nonlinear control design, the output pressure error dynamics are presented in a first order system with which the system performance is restricted by the limitations on control actuation, unmodeled dynamics, and parametric uncertainties. The discharge pressure overshoot is eliminated for the compensated closed-loop control system. On-line adaptive learning is introduced to compensate for the uncertainty in the pressure carry-over angle, which induces the most significant torque on the swashplate in a variable displacement pump. Experimental results are provided to validate the effectiveness of the proposed control approach.
Machine Diagnostics Using Nonlinear Output Observer and Neural Network Models
Authors: Fretheim Tor , Shoureshi Rahmat , Vincent Tyrone , Torgerson Duane , Work John
Published: November 2021

Predictive maintenance is rapidly becoming a familiar concept in industrial fault detection. The ability to detect early warning signals in systems in the form of small changes in dynamic behavior is essential to anticipate failures. In general, accurate system models are an essential part of residual based fault detection. However, in complex nonlinear systems, the development of accurate models can be very difficult, thus usually other approaches are often selected. As an alternative to the nonlinear analytical models, neural networks have shown significant potential in accurately representing nonlinear systems. In this paper we show how a system identified by a neural network, and a nonlinear observer can be used to detect changes in system dynamics. The neural network structure and identification have a significant impact on the observer performance. Different methods for observer design, and appropriate neural network structures for fault detection are discussed. The experimental section shows the observer implemented on a thermo fluid system. Several faults are introduced, and the observer prediction is compared to actual data.
Fault Diagnosis With a Model-Based Recurrent Neural Network
Authors: Gan Chengyu , Danai Kourosh
Published: November 2021

The utility of a model-based recurrent neural network (MBRNN) is demonstrated in fault diagnosis. The MBRNN can be formatted according to a state-space model. Therefore, it can use model-based fault detection and isolation (FDI) solutions as a starting point, and improve them via training by adapting them to plant nonlinearities. In this paper, the application of MBRNN to the IFAC Benchmark Problem is explored and its performance is compared with ‘black box’ neural network solutions. For this problem, the MBRNN is formulated according to the Eigen-Structure Assignment (ESA) residual generator developed by Jorgensen et al. [1]. The results indicate that the MBRNN provides better results than ‘black box’ neural networks, and that with training it can perform better than the ESA residual generator.
Powertrain Modeling With Modelica
Authors: Tiller Michael , Davis Cleon , Tummescheit Hubertus , Trigui Nizar
Published: November 2021

In this paper we will describe the development of models for prediction of powertrain performance. Our goal is to develop a library of components to model combustion, gas dynamics and mechanical response. We will also demonstrate the ease with which we can replace traditional component models (e.g., mechanically actuated valves) with non-traditional component models (e.g., electro-mechanically actuated valves) without having to change or reformulate any of the other components in our system.

The models were developed using the Modelica modeling language (Modelica Design Group, 1999) which allows component-based descriptions of behavior for complex engineering systems. Modelica is particularly well suited for creating behavioral models that are typical for powertrain plant models In addition to writing component models, the freely available Modelica Standard Library contains basic models from various engineering disciplines (e.g., resistors, shafts, springs).

With this approach, models can be symbolically preprocessed to improve computational performance. In addition, code can be generated from the Modelica model which can be used as either a stand alone analysis tool, imported into Simulink as an S-function or downloaded for use in real-time hardware in the loop experiments.
A Control Scheme to Produce a Catalyst Feedgas With Arbitrary Periodic Air-to-Fuel Ratio
Authors: Davison Daniel E. , Cornelius Stephen J. , Glover Keith
Published: November 2021

Motivated by investigations into catalytic converter modelling, this paper considers the problem of using an engine to generate a catalyst feedgas which has a predefined periodic air-to-fuel ratio. A simple feedback control scheme is proposed. The scheme is intended for fixed air flow and fixed engine speed operating conditions. Its main advantage is that it does not require a fuel puddling model, yet it can achieve high tracking performance that is usually associated only with feedforward schemes. Both theoretical and experimental results are presented.
PDAE Formulation for Multi-Domain Dynamic Systems With Application to Fluid-Structure Interactions in Arterial Hemodynamics
Authors: Tarraf Danielle C. , Asada H. Harry
Published: November 2021

A systematic approach to modeling coupled distributed dynamical systems by formulating them as partial differential equations and algebraic constraints (PDAEs) is presented. Several advantages of the PDAE formulation are listed and discussed. The challenges of ensuring well-posedness are also touched upon. The PDAE system is converted by semi-discretization into a corresponding DAE system. It is subsequently realized for the purpose of simulations using a recently emerging control based approach. Thus, the typical requirement of consistent initialization is avoided for a large class of systems. The PDAE formulation and the numerical solution approach are illustrated through a particular application: modeling of fluid-structure interactions in arterial hemodynamics.
Distributed Control of Rotating Stall in an Axial Flow Compressor With Actuator Constraints
Authors: Buhr Craig A. , Franchek Matthew A. , Fleeter Sanford
Published: November 2021

Presented in this paper is an analytical study evaluating the closed loop stability of rotating stall control in an axial flow compressor subject to a nonlinear spatial actuation constraint that limits the amplitude of a spatial mode input. Absolute stability of the rotating stall control system is investigated by applying the circle criterion to a linearized model of an axial compressor in series with the saturation element. This stability analysis is then used to design the gain and phase of the ‘classical’ complex gain feedback control law. Resulting is a systematic method for designing the parameters of the complex gain control law which increases the region of absolute stability guaranteed by the circle criterion for the closed-loop system.
Lumped-Parameter Modeling of Visco-Elastically Coupled Rigid Bodies Using Clifford’s Biquaternions
Authors: Fasse Ernest D.
Published: November 2021

This work considers the problem of modeling visco-elastically coupled rigid bodies, with application to modeling and computer simulation of spatial, flexural mechanisms. A method of modeling visco-elastic coupling based on Clifford’s biquaternions (dual quaternions) is presented. The potential utility of the method is demonstrated by simulating the behavior of a complex spatial, flexural mechanism.
Devices for a Micromanipulation System
Authors: Haddab Yassine , Chaillet Nicolas , Cabodevila Gonzalo , Bourjault Alain
Published: November 2021

The manufacture of MEMS requires the use of tools and machines able to execute dexterous manipulation of small mechanical components. Since several years various prototypes of micromanipulators using various types of actuators have been designed. The tools designed are often able to handle only specific microobjects and in particular conditions, the prototypes designed are rarely equipped with powerful sensors. Generally, designers of micromanipulators focus on the actuation principles. This is why the microgrippers designed are rarely equipped with powerful sensors. In this paper we present devices used as parts of our micromanipulation system. The micromanipulation system is able to perform 3D micromanipulation tasks in a volume of several mm3. The microgripper designed is characterized by a positioning accuracy of 10 nm and it allow us to measure the forces applied on the manipulated objects. Precise manipulation tasks can be performed.
A Visually Servoed Active Camera for Miniature Mobile Robots
Authors: Yesin Kemal B. , Nelson Bradley J.
Published: November 2021

In this paper, an active vision system for a miniature mobile reconnaissance robot is presented. The system consists of a single-chip CMOS video sensor, a wireless video transmitter and miniature brushless D.C. motors. Visual tracking and servoing techniques were used to test the dynamic capabilities of the system. Additionally, a simple yet effective motion detection and tracking algorithm suitable for systems with limited computational power was developed and implemented. Available technologies for image sensing and actuation are surveyed for compatibility with the severe size, weight and power restrictions that the robot presents. The video system is designed to be concealed inside the robot and performs a deploy-retract motion in addition to pan and tilt. Different mechanism designs to reduce the number of actuators are presented.