bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of a Hemispherical Magnetic Levitation Haptic Interface Device
Authors: Berkelman Peter J. , Butler Zack J. , Hollis Ralph L.
Published: July 2023

We are currently fabricating a haptic interface device to enable direct physical interaction with dynamic simulated three-dimensional environments by exerting and reacting to forces and motions between the user’s hand and a magnetically levitated object. Our device uses magnetic levitation rather than a motorized linkage so that the dynamics are simple and actuator nonlinearities such as hysteresis, backlash and static friction are eliminated. Magnetic levitation haptic interaction was previously demonstrated using a fine motion robot wrist. A new magnetic levitation device was then designed specifically to address the requirements of realistic tool-based haptic interaction. A hemispherical device shape was adopted to maximize the ranges of translation and rotation and the ratio of actuator surface area to the levitated mass while enabling the user to grip a tool handle at the hemisphere center, near the center of mass, where translation, rotation, force, and torque ranges are the same in all directions. The new device will have a motion range of at least ±12 mm and ±7°, position sensing resolution within 3 μm, and will be capable of generating peak forces up to 60 N. Preliminary results from testing of position sensors and actuator assemblies support the performance data obtained from model analysis.
Task and Motion Analyses in Endoscopic Surgery
Authors: Cao Caroline G. L. , MacKenzie Christine L. , Payandeh Shahram
Published: July 2023

We present here task and motion analyses, part of a larger study on users, tasks and tools in endoscopic surgery. Expert and novice surgeons’ performance of laparoscopic surgery in training workshops was captured on video and analyzed. Four basic surgical tasks were identified: dissecting tissue, suturing, tying knots, and cutting suture. Each task was decomposed into subtasks with operational beginnings and endings. Subtasks were further analyzed into component motions. Here we discuss: differences between novice and expert surgeons; task constraints that might account for the pattern of results across the different tasks, including precision and safety constraints; differences in manipulation of the same endoscopic tool as a function of the target object; the large number of “additional” motions; difficulties in positioning and orientation of tools to perform the surgical tasks; and the serial execution of reach and grasp movements in endoscopic surgery, compared to their parallel execution in natural prehension.
Engineering Icons for Multidisciplinary Systems
Authors: Rosenberg Ronald C. , Hales Michael K. , Minor Mark A.
Published: July 2023

Many modern engineering systems are multidisciplinary, in that they incorporate energy effects from a variety of domains. Iconic representations of components have been standardized for different disciplines in order to provide a consistent set of conceptual modeling tools and to facilitate communication. In this paper we propose a generic multiport icon (GMI) for unifying conceptual reasoning and communication about multidisciplinary engineering system models. We show how the GMI can be used to represent existing icons from electrical, mechanical, fluid power, bond graph, and block diagram domains in a compatible manner. We show that hierarchical modeling is supported. We discuss the concept of icon loading, which is an important issue in the design of icon-based model libraries. The development is structured throughout with reference to the four levels of modeling abstraction introduced by the Twente research group.
Development of a Six-Component Miniature Force Sensor for Robotic Applications
Authors: Jin W. L. , Mote C. D.
Published: July 2023

A six-component miniature force sensor (5 × 5 × 5 mm3) is developed using micro-fabrication and conventional precision machining technologies. High sensitivity and high stiffness are obtained simultaneously with a novel silicon sensing element design. Fair agreement between predicted and measured sensitivities is obtained.
Adaptive Control Using Multiple Models and Model Weighting
Authors: Rajagopal A. , Krishnamurthy K.
Published: July 2023

A general methodology for the identification and control of dynamical systems with several operating environments and possessing a high degree of uncertainty is presented. Neural networks are used to create multiple models to capture the dynamics of the various environments of the system. Control is effected by combining these models by using an evolutionary strategy. The methodology is applied to the problem of controlling a two-link robotic manipulator in the presence of disturbances and varying load conditions. Simulated results presented show that the proposed methodology yields better results compared to the ones obtained by using a single model or by using multiple models but switching to and tuning the model with the smallest tracking error.
An Approach Using Neural-Fuzzy With Modified Fuzzy Associative Memory for System Identification
Authors: Chang Hsin-chi , Lu Wen F.
Published: July 2023

In this paper, a Neural-Fuzzy with modified fuzzy associative memory (NFFAM) approach is developed for the system identification. This approach contains two mechanisms: modified fuzzy associative memory (FAM) and neural-fuzzy. It combines the learning capability of the neural networks and the linguistic characteristic of fuzzy rules. The modified FAM is used to define the initial structure and initial parameters of the rule base, while neural-fuzzy is used to adjust the rules defined by modified FAM. The simulation results show that for a Mackey-Glass time series prediction problem, the proposed NFFAM itself only implements 61 fuzzy rules to simulate the system, and the learning rate is faster than the Back Propagation Neural Network (BPNN). Besides the advantages of a faster learning rate and self-organization, the NFFAM is a rule-based reasoning approach. Being able to recognize the characteristics of the system from rules was the reason for developing this approach.
Bounded-Input Bounded-Output Stability of a Damped Nonlinear String
Authors: Shahruz S. M.
Published: July 2023

In this paper, we prove that the displacement of a damped nonlinear string under bounded distributed forces is bounded. The proof is achieved by showing that an energy-like (Lyapunov) function corresponding to the string is bounded.
Contact Transition Control of Nonlinear Mechanical Systems Subject to Unilateral Constraints
Authors: Pagilla Prabhakar R. , Tomizuka Masayoshi
Published: July 2023

In this paper, contact transition control of mechanical systems subject to unilateral constraints is presented. A systematic way is proposed for designing the control laws for unilaterally constrained mechanical systems. Three phases of motion (inactive, transition, active) are formulated depending on the activation/deactivation of the constraints. Our framework describes the complete behaviour of the mechanical system under the action of unilateral constraints. We propose stable control laws for all the phases of the system. Of special interest is the contact transition problem. During this phase the dynamics is discontinuous. Stability analysis of the transition phase is conducted using nons-mooth Lyapunov stability theory. The transition phase is shown to be exponentially stable. The proposed method is successfully implemented on robots interacting with an environment, and we present results of those experiments.
Stability Analysis of Healthy Greyhounds via Lyapunov Exponents
Authors: Marghitu Dan B. , Nalluri Prasad
Published: July 2023

This paper evaluated the applicability of a mathematical technique of computing Lyapunov exponents for nonlinear systems to describe and define normal greyhound gait. A commercially available video based, 2-dimensional motion analysis system was utilized to acquire kinematic data from healthy greyhounds being led at trot. The removal of noise from the time series data obtained from measurements was accomplished with B-spline wavelets. Lyapunov exponents of five normal subjects were computed from the kinematic data. For the steady state animal locomotion one of the Lyapunov exponents was always zero and all other exponents were negative. Lyapunov exponents provided a useful characterization of the given experimental data set.
A Proper Orthogonal Decomposition Approach to Coupled Structural-Mechanical Systems
Authors: Georgiou Ioannis T. , Schwartz Ira B.
Published: July 2023

This work applies the proper orthogonal decomposition method to identify the asymptotic dominant degrees-of-freedom of a parametrically driven pendulum coupled to a vertical linear viscoelastic rod. Most of the energy of the system is carried by one slow degree-of-freedom whenever the fundamental frequency of the rod is sufficiently larger than that of the pendulum. For certain ranges of physical parameters, the dynamics of the coupled system becomes very large, spreading the energy among many degrees-of-freedom.
Control of Two Coupled Pendula With Zero Energy Change
Authors: Quinn D. Dane
Published: July 2023

We study a system of two identical forced pendula, coupled with a linear torsional spring. Using the idea of energy transfer between the two oscillators, we derive a nonlinear control law to stabilize the in-phase motion. Trajectories of the controlled system are required to remain on the constant energy surface of the Hamiltonian.
Analysis of the Forced Response of Dry-Friction Damped Structural Systems Using an Efficient Hybrid Frequency-Time Method
Authors: Guillen J. , Pierre C.
Published: July 2023

The steady-state response to periodic excitation of dry friction damped structural systems is studied. The general model considered is a linear structure with one flexible dry friction damper connected to ground — representing, for example, a blade with an attached friction damper in a turbomachinery rotor stage. A full hysteretic model of the dry friction force is considered, which involves no further approximation of Coulomb’s law. Namely, the relative slip velocity at the frictional interface is taken to vanish when the damper is stuck, unlike the often-assumed piecewise linear relation between friction force and slip velocity. The solution procedure used is a hybrid frequency-time domain algorithm, which is largely based upon the incremental multi-harmonic balance method. The method is significantly improved by the use of several efficient numerical techniques, such as Fast Fourier Transforms and Toeplitz Jacobian Matrices. In addition, new features are developed to achieve the fast generation of frequency responses, namely, adaptive step size and line search algorithms for automatic sweeps in amplitude and frequency. The resulting solution procedure is highly performant and gives reliable and accurate results for a wide range of system parameters. It allows for the fast and automatic generation of steady-state frequency responses. Results are obtained for both a single-degree of freedom, dry friction damped system and for a beam with one friction damper attached. Interesting features of the non-linear response are revealed.
Bifurcation and Chaos in Parametrically Excited Contact Vibrations
Authors: Narayanan S. , Sekar P.
Published: July 2023

The rolling contact problem between two contacting cylinders is analysed. The contact force between the bodies is assumed to be given by the Hertzian contact law. The equation of motion is derived in nondimensional form which is nonlinear and contains harmonic parametric excitation terms induced by the surface corrugations and the relative rotation between the cylinders. The periodic solutions are obtained by a numeric-analytical algorithm based on FFT and Galerkin error minimization. An arc length based path following technique in conjunction with a stability analysis is used to obtain the response curves and the bifurcation points. Flip bifurcation boundaries are obtained for different values of surface waviness amplitude in a two dimensional parametric plane consisting of damping and rotational speed parameter. For low values of damping and high values of amplitude of surface waviness, the system exhibits chaotic behaviour attained through a period doubling route.
Self-Scheduled H∞ Controllers for Magnetic Bearings
Authors: Tsiotras Panagiotis , Mason Stephen
Published: July 2023

In this paper we present a design procedure for disturbance attenuation with internal stability of a rotor supported by magnetic bearings, over the whole interval of the rotor operating speeds. The nonlinear gyroscopic equations can be simplified to a set of linear, time-varying differential equations, owing to the linear dependence of the rotor speed in the plant dynamics. For rotors operating in high speeds, even small unbalanced masses can create large synchronous disturbances. To alleviate the forces produced due to imbalance the controller automatically balances the rotor for each operating speed. The proposed methodology addresses both the gyroscopic compensation problem due to change of the rotor speed as well as the automatic balancing problem. The approach is based on the recently developed theory of self-scheduled H∞ controllers. Owing to the linear dependence of the equations on the rotor speed, the computation of the controller can be done very efficiently using convex optimization and Linear Matrix Inequalities (LMIs).
Nonlinear Filtering of Signals Exhibiting Large Fluctuations in Strength
Authors: Jayasuriya Suhada , Langari Reza
Published: July 2023

Considered in this paper is the following filtering problem: Given a signal which has a certain frequency spectrum (|ω| ≤ Ω) and a wide range of strength over that spectrum including such low levels which may not be distinguishable from noise and high levels that could distort the signal due to, say, inherent nonlinearities in the sensors over those ranges, (i) would it be possible to identify the signal correctly?, and (ii) how could it be done? Proposed is a scheme in which the original signal is first distorted by a mono-tonic function and is then passed through an ideal low-pass linear filter resulting in a filtered version of the distorted signal. It is shown that the original signal may be uniquely recovered from the ultimate filtered version of the distorted signal.
The Modal Diagnostics of Rotors With Cracks
Authors: Goldman Paul , Bently Donald E. , Muszynska Agnes
Published: July 2023

This report provides insight into the synchronous response of a cracked multimodal rotor during transient processes of startups or shutdowns. The transversal crack on the rotor is treated as a structure singularity which provides an additional local flexibility and mass reduction. The influence of it on the global rotor behavior is estimated. The rotor lateral response synchronous component is investigated from the mode shape stand point. The results are formulated as suggestions for the vibrational diagnostics strategy improvements.
A Finite Element Method for Separable HRR Solutions in Bi-Material Systems
Authors: Zhang Ningsheng , Joseph Paul F. , Kaya Ahmet C.
Published: July 2023

Separablesingular eigensolutions at points of geometric and/or material discontinuity are determined by the finite element method. The method is applicable to n-material anisotropic elastic behavior as shown by Pageau et al. (1995), and to n-material isotropic power-law hardening behavior, including the case of complex eigenvalues for plane stress, as shown by Zhang and Joseph (1996a,b,c). Separable HRR solutions for the nonlinear problem are limited to cases whereall materials have the same hardening exponent. This paper demonstrates these capabilities with several examples that have relevance to ceramic coatings on metal substrates. The examples include the elastic case of a crack touching an isotropic-orthotropic interface, and several power-law hardening cases for bi-material systems. Both plane strain and plane stress solutions are considered.
Micromechanical Study of Particulate Reinforced Composites
Authors: Choi D. K. , Nomura S.
Published: July 2023

Particulate reinforced composites include functionally graded materials that are to be exposed to extremely high temperatures at one side and extremely low temperature at another side. In this paper, the steady-state temperature field in particulate reinforced composites is derived using the Green’s function expressed by a linear combination of the eigenfunctions for the given geometry and the boundary conditions. The trial functions that are used to construct the Green’s functions are those that warrant continuous temperature and heat flux across the material boundary (heat-flux-conserving trial functions). The solution by the proposed method is compared to the finite element solution for accuracy.
Micromechanical Edge Effects in Glass Matrix Composites
Authors: Tandon G. P. , Kim R. Y. , Dutton R. E.
Published: July 2023

This paper reports on our efforts to demonstrate the significance of free edge effects on the effective response of a unidirectional composite under combined thermal and transverse loading and to validate the predictions of an analytical model through the careful design and testing of composite specimens. Included in this study are the demonstration of potential failure modes and the predictions for the micromechanical stress fields which define damage initiation and the constituent energy release rates governing crack propagation within the constituents and along the interfaces. The theoretical predictions for damage development and propagation are in good agreement with the experimental measurements and observations and demonstrate the importance of free edge stresses in controlling damage initiation and subsequent response.
A Model for the Effusion of Water in Carbon Phenolic Composites
Authors: Sullivan Roy M. , Stokes Eric H.
Published: July 2023

A model is developed for the effusion of water in phenolic composites as the material is heated to moderate temperatures. The model is developed from the theory of the flow of gases through a porous media coupled with the thermodynamics of the evaporation of water from a condensed, binary mixture. The resulting model accounts for the evaporation of water from solid sites in the material to an internal pore network and then the subsequent flow of water vapor through the pore network. The mathematical theory is applied by simulating the effusion behavior of water in a thernogravimetric test. The results obtained from the model compared favorably with the thermogravimetric measurements. The results also showed a close correlation between the permeability of the material and the rate of evaporation of water from the solid sites.
An Approach to Characterize Nonlinear Viscoelastic Material Behavior Using Dynamic Mechanical Tests and Analyses
Authors: Golden H. J. , Strganac T. W. , Schapery R. A.
Published: July 2023

Traditional methods of viscoelastic material characterization have not been able to rapidly characterize nonlinear viscoelastic materials. Dynamic mechanical analysis has been a method in which only linear viscoelastic material properties are rapidly identifying. Herein, dynamic mechanical analysis is extended to provide a method of nonlinear characterization. The proposed method is based on an extension of Schapery’s nonlinear viscoelastic model to dynamic mechanical theory. The oscillatory loading during a dynamic test is accounted for by expanding the nonlinear viscoelastic model on stress. An experimental protocol is established and utilized in the characterization of thin film polyethylene for validation of the nonlinear dynamic mechanical theory.
Fatigue Damage Modeling and Life Prediction of Titanium Matrix Composites
Authors: Wang P. C. , Yang J.-M. , Mal A. K.
Published: July 2023

The evolution of microstructural damage during fatigue loading, which includes matrix cracking, interfacial debonding, and fiber fracture results in the progressive degradation of mechanical properties of the fiber-reinforced titanium matrix composites. A mechanism-based fatigue life prediction methodology was developed to simulate the evolution of fatigue damage, degradation of mechanical properties, and distribution of fatigue lives under various applied stress levels. The simulated matrix crack propagation rates, residual stiffness, residual tensile strength, and fatigue life are also correlated with experimental results.
An Autonomous System for the Active Control of Noise on a High Speed Patrol Craft
Authors: Dignan M. , Schudel G. , Sutterlin M. , Kewley D.
Published: July 2023

An autonomous active noise control system has been developed to reduce low frequency noise in the aft berthing space of a high speed patrol craft. The system controls both high amplitude propeller blade-rate harmonic noise, as well as broadband noise caused by propeller cavitation and machinery. A local control strategy using an adaptive feedback algorithm provides a quiet zone at the head of each bunk. One system, containing a loudspeaker, microphones, and control electronics, is mounted at the head end of each bunk. The only external connection to the system is a power cable. Noise reductions of up to 20 dB at tones and 8, 15, and 5 dB in the 31, 63, and 125 Hz octave bands respectively have been measured at the head position of the bunks. Overall A-weighted level reductions of up to 6 dB have also been measured.
Estimation of the Fuzzy Substructure Model Parameters Using the Mean Power Flow Equation of the Fuzzy Structure
Authors: Soize Christian
Published: July 2023

This paper presents a theoretical approach for identifying the dimensionless mean coefficient of participating fuzzy mass which is the main unknown parameter of the type I or II fuzzy law previously introduced by the author. This method is based on the use of the associated power flow equation, each power term being identified by using a global statistical energy analysis of the fuzzy structure (master structure with its fuzzy substructures). Identification is then carried out by solving a nonlinear constrained optimization problem. An example is given to illustrate the theoretical results.
Using Composite Materials for Noise Attenuation in Automobiles
Authors: Raichel Daniel R.
Published: July 2023

An overview is rendered of the criteria that must be met in the use of composite materials for reducing NVH (noise-vibration-harshness) in automotive vehicles. Previous work in structural mechanics provide the foundation for defining composite complex moduli, and. hence, loss tangents of fiber and particulate composite materials as functions of the constituent (i.e., fiber and matrix) properties. Specific materials can be cited as being primary candidates for NVH control in vehicles, primarily through structural stiffening, and these can also serve other functions such as promoting vehicular lightness and providing for passenger protection. The field remains wide open for the introduction of new types of composites and structural rheological matrices.
Space-Time Analysis of the Flow-Induced Vibration of a Solid Containing an Embedded Cylindrical Shell
Authors: Hull Andrew J. , Abraham Bruce M.
Published: July 2023

This paper develops a model of a viscoelastic solid that contains an embedded cylindrical shell through which fluid flows at low Mach number. The model output corresponds to the displacement that a beamformed, steered array of sensors would measure in wavenumber and frequency. The solid and the shell are modeled using elasticity equations of isotropic mediums. The fluid is modeled with two pressure terms: one that represents the acoustic pressure field and one that represents the normal forces of the turbulent boundary layer on the inner wall of the cylindrical shell. The fluid equations are coupled to the solid equations by conservation of momentum. The spatial (or wavenumber) response of the array and the array elements are also included in the model. All the model terms are assembled into a single integral equation which is numerically evaluated at various frequencies. The work is verified with an experiment in which gravity-fed water is passed through a piece of surgical tubing that is contained in the block. Displacement measurements of the free surface of the block are made with an eight-element array, and the results are compared to the theoretical model. It is shown that the model and the experiment are in good agreement.
Growth and Propagation of Acoustic Waves of Nonuniform Sound Speed Within a Plane-Walled Enclosure
Authors: Kuprowicz Nicholas J. , Petrykowski John C. , Eloe Paul W.
Published: July 2023

The propagation of acoustic waves through nonuniform temperature fields may suffer distortion due to local sound speed variations. This paper considers the case of the generation and propagation of acoustic waves through a nonuniform temperature field where the spatial variations are caused by eddy current heating of a fluid layer. Numerical solutions to the variable coefficient inhomogeneous wave equation are presented for the case where the fluid is excited in the transverse direction and the adjoining walls are acoustically hard. Progressive and dispersive waves can be clearly distinguished in the numerical results with a dispersive wave speed value within 1.5% of theory. In addition, the progressive waves are shown to propagate along curved characteristics with the curvature being related to the severity of the sound speed gradient. Several eddy current heating applications are described in which propagation of acoustic waves is significantly altered by the nonuniform sound speed profile.
Effect of an Annular Inlet Guide on the Performance of Low-Speed Centrifugal Fans
Authors: Vadari Viswanathan R. , Ruff Gary A. , Reethof Gerhard
Published: July 2023

Understanding the complex flow in the inlet and scroll of low-speed centrifugal fans is required to improve fan aerodynamic and acoustic performance. Previous investigators have documented the presence of a strong separation region at the inlet of a centrifugal fan. In this study, a simple annular inlet guide (AIG) was designed to reduce the size and strength of the separation region, thereby improving the flow quality entering the impeller and reducing noise. Preliminary inlet guide designs resulted in a reduction of 6 dB at the blade passing frequency and a 10 dB reduction at its second harmonic. A reduction of 3 dB in the broadband frequency range of 0 to 2000 Hz was also obtained without loss of aerodynamic efficiency. Based on static pressure measurements made in the exhaust duct, the AIG was found to redistribute the flow uniformly over the width of the impeller.
A Modified Secondary Source Method for Characterizing Pump Acoustic Source Impedance in Hydraulic Systems
Authors: Chen Chuan-Chiang , Hastings Mardi C.
Published: July 2023

Hydraulic pumps generate flow ripples which interact with the hydraulic circuit and cause pressure pulsations (fluid-borne noise). This kind of noise is a major source of structural vibration and airborne noise. In order to study the noise and vibration in hydraulic systems, the pump source impedance must be characterized.

In general, the pump source impedance is independent of the interaction between the pump and circuits connected to it. Former researchers [1,2,3,4] measured acoustic pressures along the transmission line at different locations and used plane-wave propagation theory to find the source impedance. However, the acoustic pressures used in previous research are dependent on the dynamic response of the circuits as well as the pump. Edge and Johnston [5,6] developed the ‘secondary source’ method to evaluate the source characteristics of hydraulic pumps. They used a secondary source to excite the pump at two different frequencies. The pump source impedance (termination impedance for the second source) could then be estimated. Since the impedance obtained from their method is for different frequencies than the harmonic frequencies of the pump, they used a suitable model along with the experimental results to find the impedance of the pump at the desired harmonic frequencies.

In this paper, a new method is proposed using a ‘modified secondary source’ method which is achieved by use of two experimental configurations. By using the principle of superposition for a linear system, the pump impedance can be found from addition of the impedances obtained from the two setups. The proposed method will be able to cover the whole frequency range without using a mathematical model for the pump.
Sound and Vibration in Composite Tubes of Variable Cross Section
Authors: McAleenan Michael G. , Nagem Raymond J.
Published: July 2023

To investigate the coupling between sound production and wall vibration in composite tubes of variable cross section, a set of composite cones with varying wall material and thickness was manufactured and tested experimentally. The approach undertaken was to optimize the relationship between cross sectional radial vibrations and structural stiffness. Employing Webster’s variation of the wave equation as a basis for a theoretical analysis, a second generalized equation was derived to include the effects of surface vibrations onto the standing wave pattern in the composite tube. Methods for solving this differential equation analytically are discussed, as are assumptions to arrive at a general solution for the natural frequency mode and shapes.

The focus of the experimental research was to produce such composite cones, excite standing waves in the cones at particular frequencies, and record the acoustic radiation and the corresponding wall oscillations for each. Carbon, Kevlar and wood veneer were chosen as materials for the composite. To reduce the influence of other factors that effect acoustical properties, each cone was laid up over a single mold. In addition, pre-impregnated fabrics were used to insure a consistent volume fraction, and the sinusoidal source and mechanical procedures were held constant.

The results suggest that composite tubes of variable cross section can be designed to obtain a coupling between the standing wave and wall vibrations to produce a specific sound quality.
An Automatic Shut-Off Valve for Hydraulic Accumulators
Authors: Song Jinchun , Zhou Shichang , Liu Lipeng
Published: July 2023

This paper introduces an automatic shut-off valve device used in conjunction with a hydraulic accumulator that compensates for leakage in hydraulic accumulator circuits. This device shuts off automatically to prevent the pressurized oil inside the accumulator from draining out whenever the pressure of the circuit drops to zero. Therefore, it saves the time and energy of recharging the accumulators.
Differential PWM Operated Solenoid Valves in the Pilot Stage of Mini Excavators: Modeling and Identification
Authors: Tafazoli S. , Peussa P. , Lawrence P. D. , Salcudean S. E. , de Silva C. W.
Published: July 2023

For computer control of the link movements in a mini excavator, the original pilot stage has to be modified. In our previous work (Peussa et al., 1995), switching on/off valves were used in the pilot stage, as an interface between the main valve and electronics. It was investigated that Differential Pulse Width Modulation (DPWM) can be used to generate the required pilot pressure. Modeling and identification of the proposed DPWM operated pilot stage is studied in this paper. Both parametric and non-parametric approaches are employed for identification. An estimated linear model is obtained for the new pilot system and its validity is checked via various tests. According to the results, the modified pilot stage has linear dynamics and is quite reliable.
Improved Simulation of Ratcheting in Straight Pipes
Authors: Hassan Tasnim , Zhu Yimin , Matzen Vernon C.
Published: July 2023

It is well known that ratcheting can cause failure in piping components or systems subjected to seismic or other cyclic loads. Commercial finite element codes cannot accurately simulate the ratcheting responses recorded in tests on piping components and systems. The reason for this can be traced to inadequate constitutive models in the existing analysis codes. To overcome this deficiency, we have incorporated an improved cyclic plasticity model, based on the Armstrong-Frederick kinematic hardening rule in conjunction with the Drucker-Palgen plastic modulus equation, into an ANSYS user subroutine. The analysis results for straight pipes subjected to constant internal pressure and quasi-static cyclic bending obtained from the modified ANSYS code are compared to experimental data, as well as to results from ABAQUS and the original ANSYS code. The simulations from the modified ANSYS are satisfactory and show a significant improvement over the original ANSYS and the ABAQUS codes.
Cyclic Material Properties Tests Supporting Elastic-Plastic Analysis Development
Authors: Hodge Scott C. , Minicucci Jay M.
Published: July 2023

Correlation studies have shown that hardening models currently available in the ABAQUS finite element code (isotropic, kinematic) do not accurately capture the inelastic strain reversals that occur due to structural rebounding from a rapidly applied transient dynamic load. The purpose of the Cyclic Material Properties Test program was to obtain response data for the first several cycles of inelastic strain reversal from a cyclic properties test. This data is needed to develop elastic-plastic analysis methods that can accurately predict strains and permanent sets in structures due to rapidly applied transient dynamic loading. Test specimens were cycled at inelastic strain levels typical of rapidly applied transient dynamic analyses (0.5% to 4.0%). In addition to the inelastic response data, cyclic material properties for high yield strength (80 ksi) steel were determined including a cyclic stress-strain curve for a stabilized specimen.

Two test methods, the Incremental Step Method and the Companion Specimen Method, were used to determine cyclic properties. The incrementally decreasing strain amplitudes in the first loading block of the Incremental Step Method test is representative of the response of structures subjected to rapidly applied transient dynamic loads. The inelastic strain history data generated by this test program will be used to support development of a material model that can accurately predict inelastic material behavior including inelastic strain reversals. Additionally, this data can be used to verify material model enhancements to elastic-plastic finite element analysis codes.
Parallel Contact Detection Algorithm for Transient Solid Dynamics Simulations Using Pronto3D
Authors: Attaway Stephen W. , Hendrickson Bruce A. , Plimpton Steven J. , Gardner David R. , Vaughan Courtenay T. , Heinstein Martin W. , Peery James S.
Published: July 2023

An efficient, scalable, parallel algorithm for treating material surface contacts in solid mechanics finite element programs has been implemented in a modular way for MIMD parallel computers. The serial contact detection algorithm that was developed previously for the transient dynamics finite element code PRONTO3D has been extended for use in parallel computation by devising a dynamic (adaptive) processor load balancing scheme. 1
Advanced Materials and Structures for Transport Aircraft
Authors: Janicki Gerry
Published: July 2023

The growth predicted in the commercial transport aircraft market by the three leading airframe manufacturers indicates that there is a one trillion dollar market encompassing over 13,000 aircraft over the next twenty years. The ability to capture a significant portion of this business will be dependent on the ability of a company to offer technologically advanced products at an affordable price. The McDonnell Douglas Corporation has established the Advanced Transport Aircraft Systems Division to develop and implement advanced technology in future transport aircraft products. McDonnell Douglas through Douglas Aircraft Company has produced over 17,000 aircraft since the early 1930’s. A key element of capturing the future market is the incorporation of technology advancements into future products in a manner that reduces the acquisition and operating costs for the airline customers. Structures and materials technology has an impact on both the manufactured cost and the direct operating cost.
Hurdles in Technology Transfer Between Industries
Authors: Barron James H.
Published: July 2023

It has long been the goal of structural composites producers to achieve aerospace quality composites using automotive production methods. It was hoped that by drawing on the best of the two industries, the goal could be achieved. However, too often, when put together, the two seem to be speaking different languages. This paper will discuss experiences of the author with interactions in automotive, aerospace, and industrial industries and attempts to exchange technologies between them.
An Aircraft Company’s Venture Into Non-Traditional Composite Structure: Bridge Decks, Windmills, Pedestrian Bridge, Transit Bus
Authors: Banuk Ron
Published: July 2023

In 1993 Northrop Corporation began to look at the potential for acquiring new business outside of the aerospace industry in the areas of composite infrastructure and surface transportation. In the field of windmills a typical design problem called for the construction of a 2000-lb blade to withstand one billion fatigue cycles over a 30-year life and be manufactured for $5/lb. The design would include an intricate all-composite root rib fitting. Design criteria for a pedestrian footbridge is shown to include a 90-ft span, bullet proof sides, fastenerless assembly, and a cost about $1000/ft. In the field of surface transportation a tank treadway needs a fastenerless damage tolerant design while the tank sponsons require the impact resistance afforded by thermoplastic materials. In another manufacturing activity bridge decking is being designed for damage tolerance to a hole in the presence of local tire contact stresses.
Offshore Structures: The Environmental, Economic and Structural Design Drivers
Authors: Mickelson Craig S. , Anderson Jeffrey J.
Published: July 2023

Composite structures are becoming more attractive to the offshore oil industry as weight becomes a critical design criteria in deep waters. Composites’ high strength to weight ratio offers potentially large weight reductions with comparable or enhanced performance for many applications. A team lead by Northrop Grumman Marine Systems (formerly Westinghouse Marine Division) consisting of DeepStar, ABB Vetco Gray, Offshore Technology Research Center, Reading and Bates and Hexcel (formerly Hercules) supported by NIST is currently developing one such offshore application, a composite drilling riser. This paper describes the design drivers for a composite drilling riser capable of operating at a 6000 foot water depth. The design drivers are categorized into three areas: environmental, structural and economic and directly determine the material selection, material property allowables, composite lay-up and composite to metal termination design.
The Development of Composites for Automotive Structures
Authors: Jeryan Richard
Published: July 2023

The automotive use of polymer composite materials offers the potential for significant benefits to both the consumer and the manufacturer. The materials and their manufacturing methods continue to be developed and composites are being applied in a widening array of structural and nonstructural parts of cars and trucks. The technical and business issues that face these applications are under development by the automotive manufacturers, materials suppliers, universities and government-supported consortia.

Composites are a mixture of several materials on a macroscopic level; they have characteristics that cannot be attained from the individual constituents. Automotive composite materials have high strength and stiffness fibers imbedded in a lower strength, lower stiffness, but easily manufactured, matrix. In polymer composites, the fibers are typically glass and the matrix is a thermoplastic or thermoset polymer. Composites exhibit a low density and a high specific strength, and can yield significant weight reduction when used in primary and secondary automotive components.
Characterization of Dynamic Ductile Fracture Using High Speed Infrared and Visible Optics
Authors: Singh Raman P. , Rosakis Ares J. , Ravichandran Guruswaminaidu
Published: July 2023

An experimental investigation has been conducted to study dynamic crack initiation in precracked ductile 304 stainless steel specimens. The specimens are subjected to dynamic three point bend loading by impacting them in a drop weight tower. This impact results in deformation followed by fracture initiation.

During the dynamic deformation and failure process the time history of the temperature and deformation fields around the crack tip are recorded experimentally. The transient temperatures are recorded using high speed infrared detectors, while the deformation fields are obtained using Coherent Gradient Sensing (CGS) in conjunction with high speed photography. The experimentally obtained temperature variation is then used to extract the time history of the dynamic J-integral, Jd(t). This is the first time that a non-contact temperature measurement is used to evaluate Jd(t). The applicability of this technique is currently being validated through comparison with the simultaneously performed optical measurements of the deformation field using CGS.
Constraint Fracture in Simulated Weldments
Authors: Anderson D. D. , Jackson J. H. , Epstein J. S. , Ganti S. , Parks D. M.
Published: July 2023

Simulated under-matched butt weldments have been fabricated using commercially pure titanium (CP Ti) as an interleaf material diffusion bonded to a higher strength 6Al-4V titanium (6Al-4V Ti). Four-point bend bars were constructed where-by the only changing geometric feature is the thickness of the CP Ti interleaf which varied from 12 to 1.7 mm. The CP Ti and 6Al-4V Ti elastic moduli are 112.3 and 115.1 MPa while the yield stresses are 366 MPa and 896 MPa respectively. A through-crack was inserted in the center of the CP Ti interleaf. Due to the close moduli, the elastic T constraint terms do not change as the CP Ti interleaf thickness is varied. However, under plastic loading, the thickness of the interleaf has a large effect on the local plastic fields surrounding the crack tip as well as the initiation J values. Using a hybrid approach with moire interferometry and finite element methods, it has been found that the higher strength 6Al-4V Ti acts to constrain the crack tip plastic zone. The net result of this constraint is a reorientation of plastic flow in the CP Ti interleaf from 90 to 45 and 135 degrees and a mean stress 2.8 times larger that the flow stress. To understand the effect of the hydrostatic constraint on the initiation process in the CP Ti interleaf, a series of double interleaf tensile bars have been developed to obtain stress-strain curves of the CP Ti interleaf under varied constraint states. These tensile specimens indicate that for the highly constrained CP Ti interleafs, that the mode of fracture initiation is due to a form of cleavage initiating at the titanium carbide stringers.
Basic Research Issues in Aerodynamics, Structural Dynamics, and Control of Turbine Engine High Cycle Fatigue
Authors: Greitzer Edward M. , Paduano James D. , Epstein Alan H. , Weisshaar Terrence A.
Published: July 2023

This paper summarizes basic research issues which can enable improved methodologies for High Cycle Fatigue mitigation in gas turbine engines. The paper is drawn from the results of a recent AFOSR Workshop on High Cycle Fatigue, which brought together a national community of industry, government, and academic researchers specifically to define these issues.
Evaluation of Long Term Durability of Polyphenylene Sulfide Using In Situ FDEMS Sensing and Mechanical Analysis
Authors: Kranbuehl D. , Newby W. , Garrett J. , Gittelson R. , Yang J. , Case S. , Reifsnider K.
Published: July 2023

Current designs for nonbonded flexible pipe used to transport oil and gas from the sea floor on offshore platforms utilize carbon steel wire to maintain axial strength. Polyphenylene sulfide (PPS) graphite tape is one possible replacement in the design of a lightweight, high strength composite flex pipe for offshore oil and gas use. This report discusses work on the use frequency dependent electrical sensing (FDEMS) techniques to monitor the extent of degradation in PPS and use of FDEMS sensing to quantitatively monitor insitu changes in the strength of the PPS during use in the field. This report also addresses the use of “mechanical test” tests to evaluate the long term ability of PPS tape to maintain hoop strength in a high temperature salt water environment.
Assessment of Residual Composite Properties as Influenced by Thermal Mechanical Aging
Authors: Plunkett R. B. , Tsang P. H. , Lesko J. J. , Wood J. D. , Rufin A. C.
Published: July 2023

In this study, two quasi-isotropic carbon fiber-reinforced polyimide material systems, IM7/K3B and IM7/PETI-5, were thermally aged at 163°C (325°F) for up to 3000 hours under a static compressive load. The future goal of this study is to determine the effect of 10000 hours (currently underway) and possibly seven years of aging on these materials. The compressive load was applied using steel fixtures supplied by The Boeing Company. Back-to-back gages on the aging panels monitored compressive strain as well as bending strain. Following aging at 1500 and 3000 hours, ambient residual compression properties were assessed using the IITRI compression test method. Unexposed specimens were also tested to obtain baseline properties for comparison. These results showed that 3000 hours of stressed isothermal aging did not significantly affect the compressive properties of the two composite systems. A slight increase in scatter of the residual strength numbers was observed. Statistical evaluation of the results was used to compute design allowables and quantify changes in scatter. Dynamic thermogravimetric analysis (TGA) tests were used to compare weight loss rate versus temperature results for the different age materials. Preliminary results show different rates of degradation occurring in the different polymer aging histories. In addition to establishing the effect of isothermal aging under load on the compressive moduli and strength of two polymer-matrix composites, this experiment links increasing scatter in residual strength measurements to changing thermogravimetric results.
Buffet Load Alleviation Using Distributed Piezoelectric Actuators
Authors: Moore Jeffrey W. , Spangler Ronald L. , Lazarus Kenneth B. , Henderson Douglas A.
Published: July 2023

Unsteady buffet loads, resulting from high angle of attack maneuvers, cause excessive vibrations in the vertical tail of fighter aircraft. These vibrations increase structural fatigue, reduce service life and reduce availability of the aircraft. Therefore, a need exists to suppress the buffet induced vibrations.

This paper describes an active buffet suppression system designed to reduce the structural response of a full scale fighter tail under buffet loads. The system level design is discussed in detail with particular attention paid to actuator design and distribution. The analysis concludes with an estimate of the system performance based on modeled disturbance rejection. The design successfully reduces the response of the tail within specific design and weight constraints. The Buffet Load Alleviation system consists of induced strain piezoceramic actuators distributed on the surface of the tail. The actuators are driven by a digital programmable controller and a linear amplifier system. Closed loop control is achieved using accelerometers and strain gages located on the tail for the feedback.