bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expanded Asymmetric Stability Bounds With First-Order Lyapunov Robustness Method
Authors: Lee Jae-Cheon , Misawa Eduardo A. , Reid Karl N. 
Published: July 2023

Abstract
The problem of stability robustness in linear time-invariant system with structured parameteric uncertainties is considered. A new technique that estimates stability boundaries is proposed. It assumes asymmetric stability bounds and is derived using the Gao’s method and the first-order Lyapunov method. It is shown that new proposed method can inherit the optimal Lyapunov function property proposed by Olas. Two examples illustrate the new method. It is shown that it is simple to apply and significantly improves the estimates of stability boundaries for interval linear dynamic systems.
Robust Stabilizing Control of Stable Interval Plants: A Time Domain Approach
Authors: Zhang Yu M. , Kovacevic Radovan 
Published: July 2023

Abstract
A time-domain algorithm is proposed to control stable interval plants. The closed-loop control actions are determined based on the interval ranges of the model parameters and feedback. Robust stability and robust steady-state performance can be guaranteed if the negative feedback condition is satisfied despite possible open-loop overshooting, delay, and nonminimum phase of the stable interval plants. Simulation and closed-loop control examples are given to illustrate the performance.
Using Chaos Control and Tracking to Suppress Alternans in a Cardiac Model
Authors: Christini David J. , Collins James J. 
Published: July 2023

Abstract
Atrioventricular (AV) nodal alternans is a pathological cardiac condition characterized by a beat-to-beat alternation (period-2 rhythm) in AV nodal conduction time. AV nodal conduction time is a vital cardiac-cycle delay which allows ventricular filling and therefore facilitates the efficient pumping of blood. Thus, AV nodal alternans, while electrical in nature, has bio-mechanical repercussions. Here we use chaos control and tracking, respectively, to suppress AV nodal alternans in a cardiac model by stabilizing the model about its unstable period-1 fixed point. We demonstrate that these techniques are robust to imprecise measurements and experimental noise. Importantly, these methods require no knowledge of the underlying system equations. These findings suggest that chaos control and tracking may be useful for biomechanical applications in a clinical environment.
Tracking Controllers for Flexibly Jointed Robotic Manipulators With Extreme Joint Compliance
Authors: Zenieh Salah , Corless Martin 
Published: July 2023

Abstract
We consider the problem of designing robust tracking controllers for uncertain robotic manipulators where the actuators are coupled to the links via flexible joints. We impose no restrictions on the stiffness of the joints; hence robots with very flexible joints can be successfully treated with the proposed controllers. Each proposed controller guarantees exponential convergence of the tracking error for a compact set of initial states: for every compact set C of initial states, there is a controller from a family of nonlinear tracking controllers which guarantees that, provided the initial state is in C, the trajectory of the closed loop system converges exponentially to a small neighborhood of the desired trajectory. Controller design is based on singular perturbation theory and Lyapunov functions.
Nonlinear Modeling and Control of I.C. Engine Idle Speed
Authors: Shah Minesh A. , Franchek Matthew A. 
Published: July 2023

Abstract
Presented in this paper is the nonlinear modeling and control of the idle speed of a Ford 4.6L-2 valve V-8 fuel injected engine. The nonlinear model is of the Hammerstein type model and is identified through input-output data without a priori knowledge of the system dynamics. The nonlinear model is utilized in the development of an H∞ controller with a nonlinear gain that maintains the idle speed within a prespecified output tolerance despite system nonlinearities, an external disturbance, and an actuator saturation constraint. The allowable output tolerance is asymmetric.
Adaptive Robust Motion and Force Tracking Control of Robot Manipulators in Contact With Stiff Surfaces
Authors: Yao Bin , Tomizuka Masayoshi 
Published: July 2023

Abstract
High performance robust motion and force tracking control of robot manipulators in contact with stiff surfaces is considered in this paper. The robot parameters and the stiffness of the contact surface may not be known. The system may also be subjected to uncertain nonlinearities coming from the joint friction of the robot, external disturbances, the contact surface friction model, and the unknown time-varying equilibrium position of the contact surface. An adaptive robust motion and force controller is proposed, which needs measurements of position, velocity and interaction force only. The controller achieves a guaranteed transient performance and final tracking accuracy, a desirable feature for applications and for maintaining contact. In addition, the controller achieves asymptotic motion and force tracking without resorting to high-gain feedback when the system is subjected to parametric uncertainties only.
Deformation and Fracture Response of Steel at High Temperature
Authors: Brust Frederick W. , Zhang Jinmiao 
Published: July 2023

Abstract
To increase energy efficiency, new plants must operate at higher and higher temperatures. Moreover, power generation equipment continues to age and is being used far beyond its intended original design life. Some recent failures which unfortunately occurred with serious consequences have clearly illustrated that current methods for insuring safety and reliability of high temperature equipment is inadequate. Because of these concerns, an understanding of the high-temperature crack growth process is very important and has led to the following studies of the high temperature failure process.
This effort summarizes the results of some recent studies which investigate the phenomenon of high temperature creep fatigue crack growth. Experimental results which detail the process of creep fatigue, analytical studies which investigate why current methods are ineffective, and finally, a new approach which is based on the T*integral and its ability to characterize the creep-fatigue crack growth process are discussed. The potential validity of this new predictive methodology is illustrated.
Dislocation Punching in Functionally-Graded Materials
Authors: Taya M. , Lee J. K. , Mori T. 
Published: July 2023

Abstract
A new dislocation punching model for a functionally graded material (FGM) subjected to a temperature change has been proposed, using Eshelby’s model. FGM, consisting of several layers, is deposited on a ceramic substrate. Two types of microstructures are examined for a layer: one consists of a metal matrix and ceramic particles and the other of a ceramic matrix and metal particles. An elastic energy is evaluated when plastic strain, in addition to thermal mismatch strain, is introduced in the metal phase. The work dissipated by the plastic deformation is also calculated. From the condition that the reduction in the elastic energy is larger than the work dissipated, a critical thermal mismatch strain to induce stress relaxation is determined. The magnitude of the plastic strain is also determined, when the relaxation occurs. The results of the present theory for a special case of FGM, i.e., the case of single interface coincide with those of our earlier work on a thin metal coating on ceramic substrate. The theory is applied to a model FGM consisting of mixtures of Pd and Al2O3 on an Al2O3 substrate.
Fatigue of Ceramic Matrix Composites: Damage Mechanisms and Fatigue Life Diagrams
Authors: Talreja Ramesh 
Published: July 2023

Abstract
Ceramic matrix composites (CMCs) provide higher strength and toughness properties than are possible from monolithic ceramics, in addition to the high temperature resistance. The mechanisms of toughness of these materials have been treated extensively, although some confusion exists in characterizing this property, which has been recently addressed in a systematic manner (Sorensen and Talreja 1995). It is, however, of greater importance in most engineering applications that the long term behavior of CMCs remains in a safe regime. In particular, degradation of stiffness and strength under cyclic loading is a major concern.
Mechanism-Based Design of Composite Structures
Authors: Adjerid Slimane , Beall Mark W. , Dvorak George J. , Fish Jacob , Flaherty Joseph E. , Hudson John , Shek Kam L. , Shephard Mark S. , Wentorf Rolf 
Published: July 2023

Abstract
The paper introduces high temperature composite software developed for mechanism-based design of composite structures. Mechanism-based design is characterized by an understanding of the critical composite behaviors at several physical scales: the fibrous (micro) scale, the ply/weave (meso) scale and the laminated part (macro) scale, and by the specification of the available design parameters to achieve functionality by those behaviors. A software framework is described which integrates material modeling and analysis codes, provides automated assistance, and links to material databases. Elastic and inelastic material modeling codes suitable for high temperature composites with complex reinforcement and weave/lay-up configurations are presented and references to their underlying theories are given. Advanced analysis techniques are outlined for numerically efficient computational plasticity based on mathematical homogenization, idealization error indicators for material scale, three dimensional crack propagation in a fibrous composite, and modeling of reactive vapor infiltration and chemical vapor deposition processes.
Fatigue Damage in Metal Matrix Composites
Authors: Voyiadjis George Z. , Echle Rainer 
Published: July 2023

Abstract
In recent years the design and performance of aerospace vehicles changed due to enhancement and improvement in the design and the materials employed. Special consideration has to be given to the performance of the materials chosen for such vehicles. Titanium matrix composites (TMC) have been identified among the metal matrix composites as candidate materials capable of sustaining the arising loads while maintaining their structural integrity. Material behavior during fatigue loading has to be given special consideration since this loading condition is dominant during the flight regime. Material degradation due to fatigue loading is modeled using a micro-mechanical fatigue damage model for uni-directional metal matrix composites. The evolution of damage is considered at the constituent level by employing a damage criteria for each individual constituent. The overall material damage is obtained by using the Mori-Tanaka averaging scheme. A numerical implementation of the model is used to demonstrate its capabilities by presenting the analytical results for damage evolution in the fibers as well as in the matrix material for isothermal high cycle fatigue loading. Results for varying material and model parameters are also presented.
Effects of Defects in a New Form of Affordable Composite Materials-Rod Reinforcement
Authors: Chan W. S. , Wang J. S. 
Published: July 2023

Abstract
A pultruded rod reinforced composite which can eliminate presence of fiber waviness and reduce cost of laminate manufacturing has become a focus interest to aircraft manufacturers. Due to its characteristics of rod layer, conventional analysis which use the smeared properties across the entire rod layer fails to predict the structural response of this rod reinforced laminates. A closed-form expression was derived and a finite element analysis was conducted for predicting the critical buckling load for this type of laminates with a damage. Damage considered include broken rods, rods split vertically and horizontally, and delamination between the rod layer and angle plies. It is concluded that damages with rods split horizontally and a delamination can reduce the buckling load. For the rods broken, the buckling load will be reduced if a broken space is included. However, the buckling load remains unchanged if rods split vertically.
The Effect of pH on the Mechanism of Corrosion and Stress Corrosion, and Degradation of Mechanical Properties of AA6061 and Nextel 440 Fiber Reinforced AA6061 Composite
Authors: Berkeley D. W. , Sallam H. E. M. , Nayeb-Hashemi H. 
Published: July 2023

Abstract
The breaking load method was used to determine the degradation rate of mechanical properties of wrought T6 aluminum 6061, and Nextel 440 fiber reinforced AA6061 composite, as a function of pH, by measuring their post-exposure residual strength. The materials were exposed to acidic NaCl at two initial pH of 1.5 and 2. Two different exposure techniques were employed; one in which the pH of the solution was kept constant by refreshing the corrosive medium, and a second method in which the solution was not refreshed. The change in pH with exposure time was also investigated to provide a more comprehensive understanding of the role of H+ ions in the corrosion process. At an initial pH of 1.5 the matrix showed a significant strengthening response, after an initial decrease in residual strength with time, if the solution was unrefreshed. However, if the solution was refreshed, the residual strength for both the corrosion and stress corrosion specimens continued to decline at an approximately constant rate. The specimens at an initial pH of 2 show a much more gradual strengthening because of the slower initial reaction rates between the solution and the alloy. The Nextel 440 fiber reinforced AA6061 composite was found to be considerably more susceptible to corrosion than the AA6061 matrix. From the results attained, it was concluded that the pH of the solution played a crucial role in the degradation rate of mechanical properties in the AA6061 matrix, and the Nextel 440 fiber reinforced AA6061 composite.
Thermal Softening of Glassy Particle Modified Tungsten
Authors: LeDuc P. R. , Bao G. 
Published: July 2023

Abstract
A micromechanics study is made of the rate-dependent thermal softening behavior of a tungsten matrix composite containing glassy particles. Under adiabatic compression of the composite, the elastic glassy particles thermally soften at relatively high strains, enhancing the thermal softening of the tungsten-based composite, thus reducing the strain rate sensitivity and fostering shear localization. To guide the microstructural design of the particle-modified tungsten-based composite in penetration applications, systematic predictions are made for the stress-strain behavior of the composite under overall adiabatic compression with different temperature-dependent behaviors, sizes, volume fractions of the particle and applied strain rates. It is found that both the onset and the rate of thermal softening of the composite depend critically on the applied strain rate. Owing to thermal softening of the glassy particles, the strain-rate sensitivity of the composite is reduced.
Evaluation of the Multidimensional QR Algorithm for Actuator Placement in Active Control Applications
Authors: Naghshineh Koorosh , Heck Larry P. , Olkin Julia A. 
Published: July 2023

Abstract
In our previous work, we developed a new actuator placement algorithm that is capable of selecting the best actuator placement for active noise control problems over a broadband of frequencies. The actuator selection algorithm is based on a novel extension of the Householder QR subset selection algorithm. In this paper, we improve our algorithm by incorporating seven new measures of actuator performance. The new measures, based on different matrix norms and functions of the actuator frequency responses, yield actuator placements that result in active noise control systems with improved performance and robustness.
Sensitivity of Structural Acoustic Response to Attachment Feature Scales
Authors: Shepard W. Steve , Cunefare Kenneth A. 
Published: July 2023

Abstract
When implementing a discrete computational method to predict the vibro-acoustic behavior of a larger structure one must decide how much effort and refinement to expend on modeling smaller attached structural components. In representing these attachments, or features, it is important to know what scales are important with regard to a valid prediction of the system response. To aid in the study of the impact of feature scales, sensitivity relationships for important system variables are developed in this paper. The sensitivity analysis will, for one, consider the change in the radiated power with respect to changes in the scale of an attached mass. These relations are developed analytically and do not require finite difference methods or eigenvalue derivatives. It is shown that computing the sensitivity of the radiated acoustic power only requires evaluating one additional term as all of the other terms are found during the normal course of modeling the system. Furthermore, the terms that include fluid loading on the structure need only be reevaluated when the excitation frequency is changed. It is also noted that the sensitivity relations developed here can easily be used to investigated the effects of modifying a number of structural parameters.
Feynman Rules for an Elastic Plate With Random Internal Scatterers
Authors: Photiadis Douglas M. 
Published: July 2023

Abstract
The ‘fuzzy structure’ approach proposed by Soize for the analysis of the effects of complex internal structure has been formulated in terms of Feynman diagrams for the case of a large fluid loaded plate. We have derived the Feynman rules both in real space and wavenumber space for the case in which the internals are simple oscillators distributed uniformly and independently in both space and frequency. With the method of calculation established, the mean Green’s function is evaluated to 3rd order in the perturbation expansion to illustrate the ease with which results can be obtained via this technique. The calculation demonstrates that the scattering effects due to the internal structure introduce damping (of a sort) and in addition exposes the parameter which must be quite small in order for low order calculations (e.g. zeroth order) to be meaningful: The ratio of the mass of a single oscillator to the mass which ‘rigidly’ supports the oscillator.
Acoustic Scattering From a Submerged Shell With Many Internal Oscillators
Authors: Bucaro Joseph A. , Photiadis Douglas M. , Houston Brian H. 
Published: July 2023

Abstract
The spectral character (temporal & angular) of the acoustic scatttering from a submerged, framed cylindrical shell in which have been inserted hundreds of dumbbell mechanical oscillators has been measured. The 880 oscillators, which are attached to the frames, are distributed over ten different frequency bands. A comparison of the measured scattering data from the shell — both with and without the attached oscillators — shows marked differences in the features displayed in frequency-angle space. Various mechanisms which might explain the character of these new features are discussed.
Boundary Element Prediction of Sound Propagation in Ducts Containing Bulk Absorbing Materials
Authors: Seybert A. F. , Seman Richard A. , Lattuca Michael D. 
Published: July 2023

Abstract
In this paper the sound propagation in a rectangular duct containing a bulk absorbing foam liner is investigated. The foam is characterized by the complex characteristic impedance which is measured using an improved two-cavity method. The complex characteristic impedance is used to predict the normal incidence impedance and absorption coefficient of the foam which is compared to measured data obtained using the ASTM E-1050 test method. The complex characteristic impedance is also used to predict the attenuation through a layer of foam in a plane wave tube for which measured results are also available. Finally, the boundary element method is used to predict the attenuation of sound in a rectangular duct where one surface is covered with foam. Comparison with experiment is shown for several frequencies.
The Design of a Robust Controller for Hydrostatic Transmissions
Authors: Hampson S. P. , Chawdhry P. K. , Burrows C. R. 
Published: July 2023

Abstract
Hydrostatic transmissions are often used for speed control in applications where large load-torque fluctuations may cause unacceptable changes in the output speed. The traditional approach is to use a closed-loop configuration and a classical control algorithm, but this often leads to unsatisfactory performance requiring on-line tuning. Modern robust controllers offer an alternative approach since they are able to explicitly take process uncertainties into account. One possibility is to use an H∞ controller for which the weights need to be selected to achieve the required disturbance rejection properties. This paper describes a case study which shows that an H∞ controller is capable of rejecting periodic torque disturbances generated by a mechanical mechanism while providing good tracking of the reference speed.
Acceleration Characteristics of Servo-Controlled Pneumatic Cylinder
Authors: Pu J. , Wong C. B. , Moore P. R. 
Published: July 2023

Abstract
Knowledge concerning the acceleration characteristics of pneumatic drives is useful in the design, control, and tuning of servo-pneumatic systems. In this paper the force/speed characteristics of an asymmetric actuator are outlined and verified. The paper then considers the rate at which a pressure differential can be established. This then leads to the concept of meter-in and meter-out control zones. The results reported in this paper should promote interests in pneumatic servos for certain profile following applications.
Analysis and Testing of Inelastic Buckling of a Ring Stiffened Cylinder
Authors: Ryan John D. 
Published: July 2023

Abstract
Naval vessels fabricated from high strength steels (HY-100) traditionally require higher yield strength weld metal to protect the weld from high strains. However, these high strength welds are costly due to strict fabrication requirements. Alternatively, reduced fabrication costs can be achieved by using slightly lower strength welds designed for use with lower strength HY-80 steel. To verify the validity of this approach, the U.S. Navy is supporting the optimized weldment properties project to evaluate the effect of lower strength welds on the performance of welded structures and institute applicable design changes.
One phase of this program included numerical and experimental evaluation of ring-stiffened cylinder structures under hydrostatic pressure loading. The objective was to modify the existing design criteria to account for the use of undermatched welds. Finite element analyses were developed using the ABAQUS and STAGS analysis codes. These analyses modeled the nonlinear, inelastic response of the structure and were used to predict buckling pressures for the structures. Experimental models were fabricated and tested to validate the numerical analyses. The experiments and analyses have resulted in design criteria modifications associated with the use of undermatched welds in hydrostatically loaded, ring-stiffened cylinder structures.