bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of Hail Damage on the Fatigue Strength of a Graphite/Epoxy Composite Laminate
Authors: Skordahl Richard A. , Mahinfalah Mohammad
Published: July 2023

An investigation was undertaken to determine the effects of hail damage on the fatigue strength of a graphite/epoxy composite laminate. Sixteen-ply coupons were subjected to simulated hail impact by iceballs of 25.4 mm or 38.1 mm in diameter. Upon impact, the 25.4 mm diameter iceball possessed 7.1 J of kinetic energy, while the 38.1 mm diameter iceball possessed a kinetic energy of 27.4 J. For further comparison, additional coupons were impacted with a 12.7 mm diameter aluminum sphere with either 7.1 J or 27.4 J of kinetic energy. Inspection revealed that neither iceball impact event caused any internal damage, while each aluminum sphere impact caused delaminations within each coupon. After being impacted and inspected, each coupon was subjected to constant amplitude tension-tension fatigue. It was determined that neither the 25.4 mm diameter iceball impact nor the 38.1 mm diameter iceball impact affected the fatigue performance of this particular laminate. The 7.1 J aluminum sphere impact also did not affect this laminate, while the 27.4 J aluminum impact did adversely affect the fatigue performance of this material.
Modeling Delamination Growth in Composites
Authors: Reedy E. David , Mello Frank J.
Published: July 2023

A method for modeling the initiation and growth of discrete delaminations in shell-like composite structures is presented. The laminate is divided into two or more sublaminates, with each sublaminate modeled with four-noded quadrilateral shell elements. A special, eight-noded hex constraint element connects opposing sublaminate shell elements. It supplies the nodal forces and moments needed to make the two opposing shell elements act as a single shell element until a prescribed failure criterion is satisfied. Once the failure criterion is attained, the connection is broken, creating or growing a discrete delamination. This approach has been implemented in a three-dimensional finite element code. This code uses explicit time integration, and can analyze shell-like structures subjected to large deformations and complex contact conditions. The shell elements can use existing composite material models that include in-plane laminate failure modes. This analysis capability was developed to perform crashworthiness studies of composite structures, and is useful whenever there is a need to estimate peak loads, energy absorption, or the final shape of a highly deformed composite structure.

This paper describes the eight-noded hex constraint element used to model the initiation and growth of a delamination, and discusses associated implementation issues. Particular attention is focused on the delamination growth criterion, and it is verified that calculated results do not depend on element size. In addition, results for double cantilever beam and end notched flexure specimens are presented and compared to measured data to assess the ability of the present approach to model a growing delamination.
Failure Development in Particulate Composites
Authors: Rubinstein Asher A. , Wang Peng
Published: July 2023

We present a model capable of evaluation of principal micromechanical processes taking place in brittle matrix composites reinforced by ductile particles. The reinforcing mechanism is based on formation of a system of restrictive forces imposed on the crack surfaces by the plastic particles behind the propagating crack front. The particles form the bridging zone and, thus, constrain the crack opening. This is the principal aspect of the toughening mechanism in these systems. The developed model addresses the effects associated with the discrete particle distribution and particle-matrix interface properties. The developed analytical approach allows us to trace the crack propagation through this system at any intermediate step. This detailed analysis explains certain aspects of the particulate reinforcement mechanism not discussed in the literature previously. The crack growth resistance curves are presented for several composite systems.
Creep Behaviour of Hot Isostatically Pressed Metal-Matrix Composite
Authors: Lim C. S. , Hung N. P. , Tan Y. C. , Loh N. L.
Published: July 2023

Castings usually contain defects such as shrinkage cavities and internal gas porosity. The application of hot isostatic pressing (HIPping) to cast metals can remove such defects through the synergistic effect of high isostatic pressure and high temperature. This paper investigates the effects of HIPping on creep of cast A359/SiC/20p composite. Although creep life was expected to improve due to removal of internal porosity in the castings, the creep results were contrary to expectations. Activation energy calculated for the cast composite, showed a decrease in activation energy for the material after HIPping. Creep life was noted to have improved with higher tensile strength as for the cast composite while creep strain at failure improved with an increase in elongation for the cast-HIPped composite. The effect of stress on creep properties are reported to show a decrease in creep life and creep strain at failure with an increase in stress, temperature remaining constant.
The Influence of Fiber Distribution and Voids on the Tensile Strength of Polymer Composite Materials
Authors: Generalis George , Sundaresan Mannur J.
Published: July 2023

Three types of material variations commonly introduced during the processing of polymeric matrix composite materials are considered. These are (i) deviations from the local fiber volume fraction from the design specifications, (ii) non-uniformity in the inter-fiber spacing, and (iii) the presence of substantial levels of local void distribution. The influence of these variabilities on the longitudinal tensile strength of unidirectional composite material is evaluated. For composite materials with uniform fiber distribution, the tensile strength slightly dropped as the fiber volume fraction was increased. The non-uniformity in the inter-fiber spacing and the presence of significant levels of voids was found to have a more adverse influence on the tensile strength.
Prediction of Axial Flow Fan Noise Spectrum
Authors: Su Shigong , Wu Sean F. , Shah Hemant
Published: July 2023

This paper presents a semi-empirical formula for predicting the noise spectra of axial flow fans in a free field. The basic assumption made in deriving this formula is that sound radiation from an axial flow fan in a free field is primarily due to the fluctuating pressure exerted on the fan blade surface. This fluctuating pressure is correlated to the lift force per unit length acting on the fan blade, and is subsequently approximated by pressure pulses that decay both in space and time. Accordingly, the radiated acoustic pressure is expressed in terms of superposition of contributions from these pressure pulses, and the line spectrum is obtained by taking a Fourier series expansion. To simulate the narrow and broad band sound spectra, a normal distribution-like shape function is designed which divides the frequency into consecutive bands centered at the blade passage frequency and its harmonics. The amplitude of this shape function at the center frequency of each band is unity but decays exponentially. The decay rate decreases with an increase in the number of bands. Thus, at high frequencies the narrow bands merge to form broad bandlike spectra. The noise spectra thus obtained are compared with the measured ones from four different types of axial flow fans running under various conditions, and a favorable agreement in each case is obtained.
The Application of Finite Element Method in Analyzing the Noise Reduction Effect of Helmholtz Resonator Attachments
Authors: Koai Kwang-Lu , Yang Tachung , Chen Jean
Published: July 2023

This paper is devoted to the study of muffling effect of Heimholtz resonators installed in different environments. A finite element approximation is employed to simulate a general acoustic environment of three (3) dimensional nature, while the Helmholtz resonators are represented by boundary conditions with a suitable amount of impedance at the frequency of interest. Using a variational formulation of the acoustic wave equation, the impedance boundary condition turns out to be damping terms in the second order matrix equations. Examples are given to quantitatively show the noise reduction effects of various Helmholtz resonator arrangement. Discussions on the damping coefficients based on lumped parameter and distributed model formulation are made.
The Characteristics of Ceramic Spool Valve Piloted Water Hydraulic Proportional Valve
Authors: Koskinen K. T. , Uusi-Heikkilä J. K. , Vilenius M. J.
Published: July 2023

Water hydraulics is one of the most rapidly growing areas in the field of fluid power. Environmental and safety aspects have strong effect to the use of water hydraulics. Also high level material technology and intelligent control systems enable better characteristics for water hydraulic components. Computer simulation is very efficient way to get information of the operation of a component and a system before the prototype or the system really exists. Especially in the research of water hydraulic systems simulation is effective, because water hydraulic components are still very expensive.

Proportional valves used in water hydraulics are normally ball seat valves, seat valves or spool valves. The latest development is ceramic spool valve, which has a spool made of industrial ceramics. Today the valves are still mainly 2/2-way or 3/2-way valves and the more complex controls must be build by using these basic elements. The control accuracy of the valves can be improved by using electrical position feedback from the control element. In some cases this is also essential for the proper operation of the valve. In this paper the simplified mathematical model for 3/2-way ceramic spool valve is presented and verified. Different control methods for the two-stage throttle valve are examined.
Formation of Pressure Gain in Hydraulic Servovalves and its Significance in System Behavior
Authors: Ellman Asko , Virvalo Tapio
Published: July 2023

The pressure gain of hydraulic servovalves is caused by an internal leakage. The leakage flow occurs because of the spool construction and finite radial clearance of the spool. The internal leakage results in unwanted properties such as crawling of a loaded actuator in open loop systems and position error of a P-controlled loaded actuator. On the other hand system damping increases. This paper presents a robust model for internal leakage that can be identified according to known pressure gain. The importance of the valve’s pressure gain on steady state and dynamic behaviour is studied by a well verified simulation model.
Elastic-Plastic Strain Acceptance Criterion for Structures Subject to Rapidly Applied Transient Dynamic Loading
Authors: Solonick William R.
Published: July 2023

Rapidly applied transient dynamic loads produce stresses and deflections in structures that typically exceed those from static loading conditions. Previous acceptance criteria for structures designed for rapidly applied transient dynamic loading limited stresses to those determined from elastic analysis. Different stress limits were established for different grades of structure depending upon the amount of permanent set considered acceptable. Structure allowed to sustain very limited permanent set is designed to stress limits not significantly greater than yield stress. Greater permanent set in structure under rapidly applied transient dynamic loading conditions is permitted by establishing stress limits that are significantly greater than yield stress but still provide adequate safety margin (with respect to failure).

This paper presents a strain-based elastic-plastic (i.e., inelastic) analysis criterion developed as an alternative to the more conservative stress-based elastic analysis stress criterion for structures subjected to rapidly applied transient dynamic loading. The strain limits established are based on material ductility considerations only and are set as a fraction of the strain at ultimate stress obtained from an engineering stress/strain curve of the material. Strains limits are categorized by type as membrane or surface and by region as general, local, or concentrated.

The application of the elastic-plastic criterion provides a more accurate, less conservative design/analysis basis for structures than that used in elastic stress-based analysis criteria, while still providing adequate safety margins.
Simple Structures Test for Elastic-Plastic Dynamic Analysis Validation
Authors: Trimble Thomas F. , Krech Gregory R.
Published: July 2023

A Simple Structures Test Program was performed where several cantilevered beam and fixed-end beam test specimens were subjected to a series of analytically predetermined rapidly applied transient dynamic input loads. The primary objective of the test program was to obtain dynamic nonlinear response for simple structures subjected to these load inputs. Data derived from these tests was subsequently used to correlate to analysis predictions to assess the capability to analytically predict elastic-plastic nonlinear material behavior in structures using typical time-dependent (transient) design methods and the ABAQUS finite element analysis code.

The installation of a significant amount of instrumentation on these specimens and post-test measurements enabled the monitoring and recording of strain levels, displacements, accelerations, and permanent set. An assessment of modeling parameters such as the element type and mesh refinement was made using these test results. In addition, currently available material models and the incremental time step procedure used in the transient analyses were evaluated.
Elastic-Plastic Finite Element Analysis-to-Test Correlation for Structures Subjected to Dynamic Loading
Authors: Hodge Scott C. , Minicucci Jay M.
Published: July 2023

A test program was undertaken to demonstrate the ability of elastic-plastic finite element methods to predict dynamic inelastic response for simple structural members. Cantilever and fixed-beam specimens were tested to levels that produced plastic straining in the range of 2.0% to 3.0% and permanent sets. Acceleration, strain, and displacement data were recorded for use in analytical correlation.

Correlation analyses were performed using the ABAQUS finite element code. Results of the correlation show that current elastic-plastic analysis techniques accurately capture dynamic inelastic response (displacement, acceleration) due to rapidly applied dynamic loading. Peak elastic and inelastic surface strains are accurately predicted. To accurately capture inelastic straining near connections, a solid model, including fillet welds, is necessary.

The hardening models currently available in the ABAQUS code (isotropic, kinematic) do not accurately capture inelastic strain reversals caused by specimen rebound. Analyses performed consistently underpredicted the peak strain level of the first inelastic reversal and the rebound deflection and overpredicted the permanent set of structures experiencing inelastic rebound. Based on these findings, an improved hardening model is being implemented in the ABAQUS code by the developers. The intent of this model upgrade is to improve the ability of the program to capture inelastic strain reversals and to predict permanent sets.
A Nodal-Based Stable Time Step Predictor for Transient Dynamics With Explicit Time Integration
Authors: Heinstein Martin W. , Mello Frank J. , Dohrmann Clark R.
Published: July 2023

A procedure for estimating the maximum stable time step for explicit finite element codes using central time difference is presented. The method is based on an estimate of maximum nodal stiffness and lumped nodal mass. The estimate of maximum nodal stiffness makes use of the finite element assembly operator and the maximum eigenvalue estimates of the finite elements being considered (in this case Flanagan’s mean quadrature hexahedron). The nodal-based stable time step calculated by this method is shown to be greater than or equal to an element based estimate alone.
Overview of the Trainline Communication Network and Associated Systems
Authors: Nast Thomas E.
Published: July 2023

The Staff of the Association of American Railroads in cooperation with the railroad supply industry are specifying a network of intelligent control devices to aid freight train handling and railway operations. This trainline control network has the potential to host electronically controlled pneumatic (ECP) brake systems, distributed locomotive power control (DP) systems, and a wide assortment of vehicle health monitoring systems.

This paper highlights some of the system level considerations of this project and provides and overview of component “black box” definitions.
NUCARS Modeling of Locomotive Bogies
Authors: Ahmadian Mehdi , DeLorenzo Michael W.
Published: July 2023

NUCARS is an industry standard dynamic simulation package that has been used extensively for railcar modeling. Locomotives can also be modeled in NUCARS, reducing the cycle time for problem solving and product development. This paper discusses NUCARS modeling, and how it is applied to a typical freight locomotive.
Modern Locomotive Fueling Facilities
Authors: Purdy David C.
Published: July 2023

This paper presents information on modern locomotive fueling facilities. Its objective is to give the reader an appreciation of the capabilities and features of such facilities. The scope is limited to the fueling platforms and their equipment. Systems off the platform are excluded.
Effects of Yarn Undulation on the Stress and Deformation of Textile Structural Composites
Authors: Chou Tsu-Wei , Ito Makoto , Kostar Timothy D.
Published: July 2023

This paper reports the effects of yarn undulation on the stress and deformation of plain weave composites. The findings from a number of sources2 are reviewed and compiled here. Existing micromechanical analyses of woven fabric composites have been conducted using mostly either simplifying mathematical models or elaborate three-dimensional finite element analysis. For example, Ishikawa and Chou proposed the mosaic model, crimp model, and bridging model for analyzing the thermoelastic and failure behavior of woven fabric composites. On the other hand, finite element analysis by Whitcomb and Foye, for example, can provide detailed stress analysis under specific boundary conditions. The recent work of Ito and Chou expands the analytical capability to modeling of the strength and failure behavior of woven fabric composites. In their studies, the geometrical characteristics of yarn shape, laminate stacking configuration, fiber volume fraction, and yarn packing fraction are investigated using three-dimensional micromechanical models. Based on the geometrical characteristics, an iso-strain approach is then developed to predict the elastic properties, local stress distributions, and failure strengths under tensile loading for four laminate stacking configurations: a single lamina, an iso-phase laminate, an out-of-phase laminate, and a random-phase laminate.
On Predicting Dynamic Compressive Properties of Some Composite Materials
Authors: Vinson Jack R.
Published: July 2023

A need exists to employ high strain rate mechanical properties of composite material systems when designing or structurally analyzing products and vehicles that are subjected to dynamic loadings. This is due to the fact that for many materials some properties vary by factors of two or three from the static mechanical properties which are so often used in design. The result is that some structures may be significantly overweight from what they could be if dynamic material properties were used in their design, while in other instances unexpected failures can occur which are difficult to diagnose if the high strain rate properties of the materials involved were unknown.

An ultimate goal might be to develop the capability to predict high strain rate properties from static material properties, but that capability does not exist today. However, it is helpful to develop the capability to predict the needed high strain rate material properties over the entire strain rate range of interest from a minimum number of dynamic tests performed, because high strain rate property testing is time consuming, expensive, and requires sophisticated equipment.

From the testing of numerous polymer matrix composite materials in compression utilizing a Split Hopkinson Pressure Bar, repeated patterns have emerged involving yield strength, yield strain, ultimate strength, strain to failure, modulus of elasticity, elastic strain energy density and strain energy density to failure. These are the properties needed for proper design, structural analysis and materials selection. By studying these patterns, a procedure is suggested by which these properties can be obtained through performing a minimum number of tests.
Delamination Induced Buckling in Orthotropic Plate Structures
Authors: Jiang W. , Bao G.
Published: July 2023

Delamination in composite laminates can cause buckling of the debonded layer; the subsequent delamination cracking can in turn be buckle-driven. To aid the failure analysis of composite structures, this article presents a critical review of analytic solutions for buckling of rectangular, orthotropic thin plates. Considered are plates with all edges simply supported, two edges simply supported/two edges clamped, and all edges clamped. The material orthotropy is characterized by two non-dimensional parameters, λ = D22/D11 and η=(D12+2D66)/D11D22. Systematic comparisons with finite element results are made for the critical buckling load of a plate under in-plane uniaxial compression. It is found that for plates with all edges clamped, the analytic solution for critical buckling load is neither accurate nor conservative. Buckling of orthotropic plates with other boundary conditions is briefly discussed.
Influence of Ply Orientation on Delamination in Composite Laminates
Authors: Tao Jianxin , Sun C. T.
Published: July 2023

An experimental investigation in interlaminar fracture behavior and toughness of multi-directional composite laminates was conducted. Based on the result of this investigation, an experimental method to determine mode II dominated interlaminar toughness of was proposed and used to obtain interlaminar toughnesses of 0/θ interfaces in AS4/3501-6 composite material with various θ’s. It was found that the critical strain energy release rate decreases as the off-axis angle θ increases.
Modeling the Effects of Translaminar Reinforcements on Mode II Fracture Toughness
Authors: Sonik V. , Sankar B. V.
Published: July 2023

Translaminar reinforcements in the form of stitching is an effective solution to suppress delaminations in laminated composites. An analytical study is conducted on the unidirectional graphite/epoxy laminates to examine the effects of stitching and the various geometric parameters associated with stitching on the apparent interlaminar fracture toughness. End-notched flexure tests were conducted to study the Mode II fracture toughness of the laminates. Shear deformable beam theory was applied to model the sublaminates where the stitches were smeared as equivalent foundation springs. Only elastic behavior of this equivalent spring system was assumed. Load-deflection patterns were obtained and the fracture toughness, GIIc, as a function of the apparent crack propagation was computed. The fracture toughness, GIIc was determined by evaluating the area under the load-deflection curve at every instant of crack propagation. The effects of mechanical properties of the smeared stitches on the crack extension was studied. The analytical model was verified by comparing with the experimental results. The effects of stitch stiffness, density, initial starter crack length and various geometric parameters were examined.
Application of Composites in Aircraft Gas Turbine Engines: Critical Issues
Authors: Miller Robert J.
Published: July 2023

Actual and potential composite applications in commercial and military aircraft gas turbine engines range from low temperature graphite/polymer matrix composite (PMC) components at the front of the engine, such as, fan blades, vanes, struts and cases, to high temperature ceramic matrix composite (CMC) nozzle components. Currently the “building block” approach is primarily used in the development of composite components for gas turbine engines. Critical issues associated with the design of these composite structures for both commercial and military aircraft gas turbine engines are defined. Critical structural components for both commercial and military gas turbine engines are designed to meet strict safety-of-flight requirements established by the FAA and the Air Force/Navy, respectively. Key design requirements established for damage tolerance and durability are defined. Areas in which research and development efforts should be accelerated are identified. There are currently a number of ongoing major funded research and development programs involving industry, academia, and government agencies which are contributing significantly to some of the issues addressed. These programs are: (1) High Speed Research (HSR), (2) Affordable Composites for Propulsion (ACP), and (3) Advanced Composites Technology (ACT).
An Interaction Integral Formulation for Computing Stress Intensity Factors Along Curved Bimaterial Interface Cracks
Authors: Gosz Michael R. , Moran Brian , Dolbow John E.
Published: July 2023

Domain integrals for extracting mixed-mode stress intensity factors along curved, three-dimensional bimaterial interface cracks are derived. In the derivation, the asymptotic auxiliary fields for the plane problem of a bimaterial interface crack are imposed along a curved crack front. The general crack-tip interaction integral is then expressed in domain form which is more suitable for numerical computation. A consequence of imposing the auxiliary fields along a curved crack front is that the auxiliary stress fields do not satisfy equilibrium, and the auxiliary strain fields do not satisfy compatibility. It turns out that the terms which arise due to the lack of equilibrium and compatibility are not sufficiently singular to contribute to the crack tip interaction integral or to affect its path independence. It is crucial, however, to include them in the domain integral representations because the domain integrals involve fields which are not asymptotically close to the crack-tip. In the paper, we present two numerical examples. As a benchmark, we consider the problem of a penny-shaped interface crack embedded in a cylinder. The results for the complex stress intensity factor and phase angle are found to be in excellent agreement with the analytical solution. The problem of an elliptical crack embedded between two dissimilar isotropic materials, for which an analytical solution is not available, is also considered, and the results are discussed.
Elastic-Plastic Analyses of Multiple Site Damages in Aluminum Sheets Using Finite Element Alternating Method
Authors: Wang L. , Atluri S. N.
Published: July 2023

This paper presents elastic-plastic analyses of Multiple Site Damages (MSD) in aluminum sheets, which contain one large crack at the center with several small cracks in front of its tips, subjected to far field tension loads. The analyses is performed based on the T*-integral fracture parameter, using the recently developed elastic-plastic finite element alternating method. A T*-resistance curve is obtained from the numerical simulations of experiments of center-cracked panels containing single cracks, in the generation phase analyses. A number of numerical predictions are made in the application phase, using the T*-resistance curve obtained in the generation phase. The predicted curves of load versus crack-extension are compared with the experimental measurements obtained at National Institute of Standards and Technology (NIST). Good agreements are observed. Through this comparison, the present paper presents, for the first time, a truly validated energy based fracture criterion for the analysis of stable growth and link-up of multiple cracks in an MSD situation.
Aeroelastic Analysis of Helicopter Rotor Blades Incorporating Anisotropic Piezoelectric Twist Actuation
Authors: Wilkie W. Keats , Belvin W. Keith , Park K. C.
Published: July 2023

A simple aeroelastic analysis of a helicopter rotor blade incorporating embedded piezoelectric fiber composite, interdigitated electrode blade twist actuators is described. The analysis consists of a linear torsion and flapwise bending model coupled with a nonlinear ONERA based unsteady aerodynamics model. A modified Galerkin procedure is performed upon the rotor blade partial differential equations of motion to develop a system of ordinary differential equations suitable for dynamics simulation using numerical integration. The twist actuation responses for three conceptual full-scale blade designs with realistic constraints on blade mass are numerically evaluated using the analysis. Numerical results indicate that useful amplitudes of nonresonant elastic twist, on the order of one to two degrees, are achievable under one-g hovering flight conditions for interdigitated electrode poling configurations. Twist actuation for the interdigitated electrode blades is also compared with the twist actuation of a conventionally poled piezoelectric fiber composite blade. Elastic twist produced using the interdigitated electrode actuators was found to be four to five times larger than that obtained with the conventionally poled actuators.
Control of Bending and Twisting Vibration in Non-Isothermal Beams
Authors: Wetherhold Robert C. , Aldraihem Osama J.
Published: July 2023

Vibration control of a beam which experiences a slowly changing through-thickness temperature variation is considered. This temperature variation produces thermal moments and curvatures which are assumed to change slowly with respect to the vibration frequencies. By proposing a Lyapunov controller which relies on a definition of strain energy without thermal expansion terms, stability of vibration control and removal of thermal curvatures are assured. By proposing a Lyapunov controller based on strain energy including thermal expansion terms, stability is assured but the thermal curvatures remain. The effect of temperature on the sensor output is included. A laminated beam with full sensor (all mode) coverage is used to illustrate the method. The continuous system is simulated using a discretized (finite element) approximation, and the successful operation of both controllers is demonstrated. The effects of the host beam stiffness and the ratio of actuator thickness to host beam thickness are determined.
Sensor Instrumentation for Smart Materials and Structures
Authors: Claus Richard O.
Published: July 2023

This paper reviews recent progress in the development and testing of sensor instrumentation for smart materials and structures, with specific consideration of sensors based on optical fiber techniques. General classes of fiber-based sensor platforms for mechanical measurements are discussed, specifically including Fabry-Perot and grating-based devices. Extrinsic Fabry-Perot interferometric (EFPI) sensors are shown to be advantageous for applications involving embedding in materials and for use in particularly harsh environments, while gratings are shown to be useful in situations requiring distributed sensor multiplexing. The very recent development of long-period grating (LPG) sensors that overcome troublesome observable cross-sensitivity while allowing increased sensitivity and low-cost manufacturing is presented. Applications of fiber sensor instrumentation in recent smart structure demonstration articles is referenced.
Active Control of Transmission of Bandlimited Disturbances Into a Three-Dimensional Enclosure
Authors: Sampath Arun , Balachandran Bala
Published: July 2023

Experimental investigations into active control of bandlimited noise transmitted into the interior of a three-dimensional enclosure with a flexible wall are presented. In the different experiments, the frequency range of the bandlimited disturbance is chosen to encompass structural and/or enclosure resonances. The rigid boundaries of the enclosure are constructed from acrylic material, and the flexible boundary clamped along all the edges is constructed from aluminum material. Lead Zirconate Titanate (PZT) patches mounted symmetrically on the flexible wall are used as actuators. Polyvinylidene fluoride (PVDF) film patches mounted on the flexible wall are used as vibration sensors, and condenser microphones placed inside and outside the enclosure are used as acoustic sensors. Digital feedforward control schemes based on filtered-x gradient descent algorithms are implemented in the experiments to minimize a chosen performance function. Different performance functions are examined, and the results obtained in the corresponding cases are compared. It is observed from the experiments conducted thus far that better noise reduction results are obtained when only acoustic sensors are used than when either vibration sensors or a combination of acoustic and vibration sensors is used.
Active Aperture Antennas
Authors: Washington Gregory
Published: July 2023

Recent studies have shown that reflector surface adaptation can achieve performance characteristics on the order of phase array antennas without the complexity and cost. The work proposed in this study develops a class of antennas capable of variable directivity (beam steering) and power density (beam shaping). The actuation for these antennas is employed by attaching polyvinylidene fluoride (PVDF) film to a metalized mylar substrate. A voltage drop across the material will cause the material to expand or contract. This movement causes a moment which causes a moment to be developed in the structure which causes the structure to change shape. Several studies of flexible structures with PVDF films have shown that cylindrical antennas can achieve significant deflections and thereby offer beneficial changes to radiation patterns emanating from aperture antennas. In this study, relatively large curved actuators are modeled and a deflection vs. force relationship is developed. This relationship is then employed in simulations where the far field radiation patterns of an aperture antenna are manipulated.
On the Shape Control of Environmentally Responsive Composite With Embedded TiNi Alloy as Effector
Authors: Yoshida Hitoshi , Funaki Atsuo , Yano Shoichiro
Published: July 2023

Bi-directional Environmentally Responsive Composites (ERC) composed of TiNi alloy effectors and CFRTP (Carbon Fiber Reinforced Thermoplastic) were fabricated to investigate the temperature responses and a method of responsive shape control of ERC.

Response upon environmental alternations was defined as the response rate and the recovery rate corresponding to the change in environmental temperature. Responsive shape control was done by controlling for the curvature of ERC when the mechanical properties and the initial curvature of the effectors were given. When the curvatures of ERC at low and high temperatures were set, the corresponding equations were derived in order to calculate the initial curvature and flexural rigidity of the matrices. As a result, it was found that a bi-directional responsive ERC with superior performance could be made by appropriately choosing the properties, the geomatries and volume fractions of effectors and matrices. The ratios of experimental and calculating values are very close to 1.0, and the numerical results were fairly satisfactory.
Active Fracture Control of a Composite Material System With SMA Actuator and AE Sensor
Authors: Furuya Y. , Shimamoto A. , Tani J. , Qiu J.
Published: July 2023

An Active control of the material degradation (i.e. damage accumulation, crack, delamination etc.) in service time and furthermore, an active prevention system of final sudden failure of machinery components and structures are studied by using shape memory TiNi fiber reinforced epoxy matrix composite model. First, the basic experimental study on active suppression of stress intensity (K value) at the crack-tip is performed by using photoelastic material. This is because the compressive stress effect is induced by means of direct current joule heating of the prestrained TiNi fibers embedded in epoxy matrix. Next, as an expansion of this study, another composite material system with SMA actuator as well as acoustic emission (AE) sensor is fabricated in which a typical AE outbreaks is utilized as a trigger to control the strengthening the bulk composite. The shape memory shrinkage of TiNi fibers is controlled under the commands from a microcomputer linked with AE sensor. This type of SMA intelligent (smart) material systems will be applicable for the elongation of the lives of material components, prevention of the sudden failure and maintaining the safety of the machinery devices, vehicles and building structures.
Shape and Location Optimization of Piezoelectric Actuators in Active Control Systems
Authors: Yousefi-Koma Aghil , Vukovich George
Published: July 2023

An optimization procedure for finding the optimal shape and location of a piezoactuator for active control of smart structures is introduced. PZT piezoceramic is used as the actuator and PVDF piezofilm is employed as a strain rate sensor bonded onto a flexible structure. The modal method is used to model the dynamic system, and state space feedback control is employed. Three different optimization criteria are studied and discussed. In the criterion we look for a configuration of the piezoactuator which maximizes the overall damping ratio of the closed loop system. Minimization of the overall real part of eigenvalues of the controlled system is the second criterion. For the third criterion, we seek the minimum LQR cost function over possible shapes and locations. Simulation provides some interesting results: for instance it is shown that in the case of constant piezoactuator area, wider and shorter actuators are better than longer and narrower ones. The methodology introduced here can be easily used in the actual experimental design of piezoactuators.
An Investigation of Microstructure and Microdynamics of Fluid Flow in MEMS
Authors: Lanzillotto Ann-Marie , Leu Tzong-Shyng , Amabile Michael , Wildes Richard , Dunsmuir John
Published: July 2023

This paper reviews x-ray imaging, visualization and analysis technologies which were utilized in an investigation of microstructure and micromotion in fluidic microsystems. These systems include fluidic microvalves, silicon v-groove microchannels and capillary tubes. Specifically, we have visualized the 3-D internal microstructure of Redwood Microsystems Fluistor microvalves and EG&G IC Sensors bimetal microvalve using x-ray microtomography and a massively parallel supercomputer. In other experiments, microradiography was used to image fluid transport through the valves as well as actuation. To better understand the microdynamics of flow, we have also studied the displacement of fluids in Si v-grooves and found that capillarity effects may be dominant. Finally, we discuss methods to visualize and measure steady-state flow in microchannels through the use of emulsions. The detailed flow patterns are directly viewable by the motion of the droplets. Computer vision motion analysis is used to recover the corresponding flow fields and velocity profiles.
Using HTML for an Online Survey of Risk Perception: An Experience Study
Authors: Halstead-Nussloch Richard
Published: July 2023

It is desirable to discover more about how much risk people perceive in everyday life and actions. Because the Internet is growing so fast, a survey on the World Wide Web might be a possible way to meet this desire. This study investigated using such an Internet survey, administered through an Internet web server, HTML, and a web browser. The online risk-perception survey had fifteen paired-comparison questions. It can be reviewed and taken at URL:

http://www.sct.edu/sct/departments/cs/classes/webwork/rpsurvey.html

Each pair had one common member, namely “Driving for an hour on suburban roads and highways.” The common member of the pair was always presented first. Two classes at Southern Polytechnic were invited to take the survey. Six responses were received from the 25 potential respondents. The low response-rate (24%) and overall results indicate that using HTML surveys on the web is more suitable for conveniently automating only the data collection rather than automating the total administration of a risk-perception survey. It is recommended that, within limits, surveys on the web can be an effective tool for assessing risk perception.
A Process to Quantify and Optimize the Effectiveness of Maintenance on Unavailability and Risk
Authors: Vesely W. E.
Published: July 2023

A process is described for utilizing available maintenance and failure data collected at nuclear power plants to quantify the effectiveness of maintenance on equipment reliability and availability. The methodology which is applied was developed under the sponsorship of the U.S. Nuclear Regulatory Commission (NRC) to help support the NRC’s Maintenance Rule. The process was applied and demonstrated using plant maintenance data for various equipment, such as diesels, motor operated valves and check valves. The applications show how maintenance can be optimized to maximize equipment reliability and availability while at the same time reducing required resources.
Building a Marketplace for Cross-Departmental Change
Authors: Sturdivant Maggie H. , Arsenault Frank J.
Published: July 2023

As the current decade opened, the Department faced the need to establish a standards basis for all of its work and the lack of a commonly accepted, standards-based management approach. The one-size-fits-all standards applied to production facilities had proven to be inappropriate for application to the diverse, complex, and sometimes undefined work of the Department’s revised mission. The Department Standards Committee was established as a high level, open marketplace for ideas — a Department-wide forum for discussion and decision. For its technical work, the Committee draws upon teams of voluntary participants from across the complex to provide a broad spectrum of experience and perspective in addressing issues such as cooperative engagement in the identification of Work Smart Standards, stakeholder involvement, and the attributes of effective documentation and implementation. The current expanding application of Work Smart Standards represents the practical results of this innovative effort.
National Training Program Efforts for Work Smart Standards
Authors: Carnes William E. , Peppers Kathleen S.
Published: July 2023

The Department of Energy recognized the need to establish a standards based, instead of expert based, way of performing its work. The Department Standards Committee was established as the high level, umbrella for developing the criteria and assisting in establishing this fundamental change throughout the Department. This paper describes the process and outcomes that Standards Process Action Team 8 (Training) applied to develop a needs analysis and method for effectively explaining the change of practices and processes within the Department. That process is based on the five step Instructional Systems Design model.
Singular Solutions of Interfacial Stresses in Multilayered Structures
Authors: Yin Wan-Lee
Published: July 2023

A general analysis methodology is developed to obtain accurate elasticity solutions of the singular stress fields associated with free edges and interfaces in multilayered structures under thermo-mechanical loads. Approximate solutions based on finite element or variational methods are used to provide traction boundary conditions on a circular path encircling the singularity. The singular elasticity solution of the region interior to the path is then determined in terms of eigenfunction expansion and by using boundary collocation. Results for a bilayer beam under a temperature load demonstrate that the interfacial stresses may be significantly contributed by non-singular eigenfunctions. Hence full elasticity solutions of the present type, rather than asymptotic solutions, may be required to assess the criticality and mode ratio of the interfacial actions across critical regions of the interface.
Tension-Tension Fatigue of Copper Thin Films
Authors: Read David T.
Published: July 2023

Tension-tension, load-controlled fatigue results extending to over 100,000 cycles for electron-beam-evaporated copper are reported. The specimen is fabricated as a single tensile coupon with hundreds of grains across the width but one or few through the thickness, supported on a silicon frame. These specimens had measured values of Young’s modulus lower than bulk polycrystalline values, but had high values of the yield and ultimate strengths. Closed-loop feedback control of the piezoelectric actuators allowed load-controlled fatigue tests with a cycle duration of 15 s. Stress-endurance results for this set of copper films are reported and compared to previous results.
Contribution of Thermal Stresses to Delamination of Coatings From Optical Fibers
Authors: Aloisio Charles J. , King Wilton W.
Published: July 2023

Sometimes the polymer coating on an optical fiber is observed to have separated from the fiber over (usually) a small portion of the interface. Irregularities on the capstans and sheaves of draw, rewind, coloring and cabling machines can initiate such delaminations. Subsequent growth would not be anticipated under the condition of radial compressive stress that might be expected for a coating shrinking over a relatively rigid fiber as the composite cools during manufacture. And compressive stress is indeed found at the interface when a single-layer coating is used. However, for a two-layer system, having a high-modulus secondary over a low-modulus primary (for improved protection against microbending), the different rates of thermal expansion can lead to radial tension at the silica/primary interface, and this tension can “drive” the growth of delaminations.

A principal result of this study is that the analysis predicts the primary coating although rubbery, to be approximately in a state of uniform hydrostatic tension. This tensile stress is of substantial magnitude because of constraints imposed by the relatively stiff secondary coating and by the fiber. The existence of significant radial tension at the fiber surface is consistent with experimental observations of induced delaminations, which are seen to grow long after cessation of external disturbances.
Recent Cryopreservation Techniques Applied to Transplantable Tissues
Authors: McNally Robert T. , Capps Scott B. , Clarke Kathryn A. , Hall M. Travis , Fronk David M.
Published: July 2023

Despite the efforts of the biomedical engineering community to devise synthetic and biosynthetic devices for surgical applications, there remain specific areas where cryopreserved tissue is clearly superior and has achieved clinical acceptance. In 13 years over 30,000 allograft tissues have been processed using state-of-the-art cryopreservation techniques. Based on a subset of 1,220 patients receiving cryopreserved allograft heart valves, the data show a 96% freedom from structural deterioration at 72 months for aortic valves used in left-sided reconstructions in the adult population, and 90% freedom from structural deterioration at 60 months for pulmonary valves used in the right ventricular outflow tract reconstructions in children. In a series of 264 cryopreserved saphenous vein allografts used for below-the-knee vascular bypass procedures, one year primary patency was 56% with a limb survival rate of 90%. Data for 303 cryopreserved memscal allografts with an average of 41 months follow-up resulted in 89% overall graft survival. These data demonstrate the benefits of proper cryopreservation technology.