bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-Uniqueness of Two Inverse Problems of Thermally and Force-Loaded Smart Structures: Sensor Shaping and Actuator Shaping Problem
Authors: Irschik Hans , Belyaev Alexander K. , Krommer Michael , Schlacher Kurt
Published: March 2022

Flexural vibrations of smart beams with integrated piezoelectric actuators and sensors are considered. For the case of a spatial variation of the sensor/actuator activity, actuator and sensor equations are derived taking into account the interaction of mechanical, electrical and thermal fields. Self-sensing actuators are included. With respect to the non-uniform spatial distribution of the sensors/actuators, shaping problems are formulated. Possible non-uniqueness of these inverse problems is pointed out. Shape functions responsible for non-uniqueness of the shaping problems are termed nilpotent solutions. Within the context of simplified sensor/actuator equations widely used in the literature, a class of nilpotent shape functions is derived for redundant beams by analogy to an auxiliary quasi-static problem of thermally induced flexure. Nilpotent shape functions of the sensor/actuator shaping problem thus turn out to correspond to bending moments in the auxiliary thermoelastic problem.
Computation of the Maximum Amplitude of a Mistuned Bladed Disk Assembly via Infinity Norm
Authors: Sinha Alok
Published: March 2022

The maximum amplitude of a mistuned bladed disk assembly has been computed on the basis of the infinity norm of a complex matrix relating amplitudes and phases of blades’ vibration and sinusoidal forcing functions. Numerical results are presented for a model containing a single degree of freedom per blade. In addition, minimum values of the maximum amplitude have also been computed along with their sensitivities to small changes in mistuning parameters.
Static Indentation and Low Velocity Impact Tests on Sandwich Plates
Authors: Ferri Rocco , Sankar Bhavani V.
Published: March 2022

Quasi-static indentation tests and drop-weight impact tests were performed on graphite/bismaleimide (GR/BMI) laminates as well as on foam-core sandwich panels. Impact tests on 8-ply laminates show that the response and damage are similar to quasi-static results. Quasi-static and impact test results on sandwich panels show that the overall response is dependent upon the response of the face sheets and the core. An increase in core density increases the overall load level, panel stiffness, core fracture toughness, and decreases the core compression. A decrease in core thickness decreases the panel stiffness and energy absorption. If the radius of the indenter is greater than the core thickness, penetration of the panel will be delayed and the failure load of the bottom face sheet will increase. The quasi-static and impact responses have the same overall trend, however, the load levels increase in impact tests due to dynamic effects.
Forced Response Prediction of Gas Turbine Rotor Blades
Authors: Hilbert Gary R. , Ni Ron-Ho , Takahashi Ronald K.
Published: March 2022

An analytical forced response prediction system is used to predict turbomachinery airfoil vibratory stress amplitudes. The forced airfoil vibration can be caused by time dependent (unsteady) aerodynamic loads due to interaction with the flow field from neighboring airfoils rows, such as shocks, wakes, or pressure waves, or due to self induced unsteady aerodynamics such as vortex shedding and unsteady tip vortices. The amplitude of the forced response is of particular interest when the frequency of the time dependent unsteadiness is close to the natural frequency of the forced airfoil. At this condition, the airfoil is at or near resonance and vibratory stress can exceed the material capability causing high cycle fatigue (HCF) failures.

The airfoil forced response prediction system presented here combines structural static and dynamic analysis with steady and unsteady computational fluid dynamic analysis in an iterative coupled solution to the aeroelastic problem. The system includes three dimensional viscous multistage steady and unsteady computational fluid dynamics and three dimensional geometric nonlinear structural static, linear free vibration and modal forced response analysis to predict the airfoil amplitude in the resonance modes during engine operation.

This analysis system is being used to help identify the cause of HCF failure and determine corrective action. The analysis system is demonstrated using a compressor rotor excited by upstream and downstream vanes. Results are then compared with engine test data.
On the Structure of Turbulent Bubbly Gas-Liquid Flows
Authors: Roy Ramendra P.
Published: March 2022

To gain understanding of the structure of turbulent bubbly gas (or vapor)-liquid flows, local measurements have been carried out in the bubbly regime of isothermal gas-liquid flow and boiling flow. The isothermal flow was created by injecting nitrogen gas into an upward flow of liquid Refrigerant-113 through a vertical pipe. The boiling flow, of Refrigerant-113, was created in a vertical annular channel whose inner wall was heated. In both flows, the radial distributions of gas (or vapor) residence time fraction, bubble mean axial velocity, and bubble diameter were measured by a dual-sensor fiberoptic probe. In the liquid phase of the flows, the radial distributions of mean axial and radial velocities, axial and radial turbulent intensities, and axial Reynolds shear stress were measured by a two-component laser Doppler velocimeter (LDV). The radial distributions of bubble mean axial velocity and axial velocity fluctuation intensity were also measured by the LDV. Vapor and liquid temperature radial distributions in boiling flow were obtained by a fast-response microthermocouple.

A multidimensional two-fluid model of turbulent bubbly gas (or vapor)-liquid flow is being developed at Electricité de France with contribution from our experimental and turbulence modeling work.
Pore-Scale Modeling of Enhanced Vapor Diffusion in Porous Media
Authors: Webb Stephen W. , Ho Clifford K.
Published: March 2022

Vapor diffusion in porous media in the presence of its own liquid has often been analyzed similar to air diffusion. Air diffusion rate is much lower than in free space due to the presence of the porous medium and any liquid present. However, enhanced vapor diffusion has also been postulated such that the diffusion rate may approach free-space values. The mechanisms postulated to account for this enhancement include condensation/evaporation across isolated liquid islands in the porous media and an increased temperature gradient in the gas phase. In order to try to understand the mechanisms involved in such an enhancement, pore-scale models have been developed. Vapor diffusion in the presence of liquid islands has been evaluated for a one-dimensional linear system, a two-dimensional pore, and a small two-dimensional pore network under a concentration gradient. The simulations show that significant enhancement of vapor diffusion is indeed possible in the presence of liquid islands, while air diffusion decreases slightly. While the present pore-scale model indicates that enhanced vapor diffusion is possible, only experimental data can confirm the relevant processes.
Predicted Thermally Induced Stresses in a Glass Fiber Epoxy Bonded Into an Elliptical Enclosure
Authors: Uschitsky M. , Suhir E.
Published: March 2022

Thermally induced stresses in an optical glass fiber epoxy bonded into a thin-walled elliptical metal enclosure are analyzed. The emphasis is on the fiber microbending and possible buckling. The adverse effect of voids in the epoxy on the stresses in the fiber and in the epoxy itself is also addressed. The developed analytical models are easy-to-use, and clearly indicate the role of various geometrical and materials factors affecting the fiber propensity to buckling and its delamination from the epoxy. The obtained results can be used in the analysis and design of optical fiber structures epoxy bonded into elliptical enclosures.
Transient, Three-Dimensional Heat Transfer Model for the Laser Assisted Machining of Ceramic Materials
Authors: Rozzi Jay C. , Incropera Frank P. , Shin Yung C.
Published: March 2022

A three-dimensional, unsteady heat transfer model has been formulated for predicting the temperature field associated with the laser assisted machining (LAM) of ceramic materials. The model considers a rotating silicon nitride workpiece heated by a translating CO2 laser, with material removal occurring at a location corresponding to the cutting tool. Movement of the workpiece relative to the laser source and cutting tool at the conclusion of a preheat phase significantly influences the workpiece temperature distribution, particularly at the material removal plane, by facilitating the transport of thermal energy deposited by the laser to the chamfer (the boundary between removed and unremoved material). Relative to predictions without material removal, the chamfer represents a significant thermal resistance to heat transfer, thereby increasing temperatures in the material removal plane at the conclusion of the preheat phase and causing a slower decay in the average temperature in this region as machining continues. The temperature distribution within the machined material remains nearly uniform for the investigated operating condition.
Analysis of Mixed Convective Cross Flow Near Protruding Heat Sources on a Vertical Circuit Board
Authors: Raghavan Jagannath , Rahman Muhammad M.
Published: March 2022

The effects of cross flow mixed convection on discrete mounted heat sources on a circuit board of finite thickness has been analyzed in this study. In this type of flow, the orthogonal free and forced convection result in a three dimensional boundary layer flow. A numerical model is developed to simulate the actual device considering heat generation in the integrated circuit components, conduction of heat through the board and heater modules, and convection of heat from the board and module surfaces to the fluid stream. The significance of the factors that affect heat transfer rate and surface temperatures of these components were analyzed. The equations for the conservation of mass, momentum, and energy were solved in their non-dimensional form to study the velocity and temperature profiles. The numerical model identified important dimensionless parameters such as Richardson number, Prandtl number, source spacing, distance from leading edges, and the ratio of solid-to-fluid thermal conductivities. A parametric study revealed their influences.
Effect of Coal Particle Size on Coal-Water Slurry (CWS) Atomization
Authors: Son S. Y. , Kihm K. D.
Published: March 2022

The effect of coal particle size on coal-water slurry (CWS) atomization is examined by comparing classified CWS sprays containing coal particles in different size ranges. The sprays are generated by injecting a CWS mixture into a sonic air jet and the Malvern sizing system nonintrusively measures spray Sauter mean diameters (SMD). The results consistently show that the spray SMDs of the CWS containing smaller coal particles are larger than the spray SMDs of the CWS containing larger coal particles. The internal capillary holding force between the particles and water increases with decreasing particle sizes because of their smaller radii of curvature. This increased holding force strongly resists against the external airblast and makes the atomization difficult. On the other hand, the relatively small capillary holding force of the CWS containing larger coal particles carries weaker resistance to the external airblast, and smaller spray SMDs result.
Radiative Calibration of Heat Flux Sensors at NIST: An Overview
Authors: Murthy Annageri V. , Tsai Benjamin K. , Saunders Robert D.
Published: March 2022

This paper describes the current capabilities and future plans at the National Institute of Standards and Technology (NIST) for radiative calibration of heat flux sensors. Experimental methods using an existing blackbody and high power lasers have been developed to characterize a reference electrical substitution radiometer and heat flux sensors, respectively. Tests carried out on a typical Schmidt-Boelter heat flux sensor showed long term repeatability of calibration within ± 0.4 %. Factors, such as purge gas flow, affecting sensor calibration when using high temperature blackbodies are discussed. To enhance the present capabilities, two additional blackbody setups are planned. These are a high temperature blackbody operating up to 3200 K with the possibility of calibrating sensors at power levels up to 200 kW/m2, and a spherical blackbody with a water-cooled aperture to calibrate sensors in a low convection environment.
A Comparison Between Colocated Mesh and Staggered Mesh Solutions for the Steady State Simple Driven Cavity Problem
Authors: Batteh John J. , Chen Michael M.
Published: March 2022

This paper presents some sample computations that employ three different schemes for the discretization of the incompressible Navier-Stokes equations: colocated mesh (CM) with basic second order finite difference approximations for the interior nodes, with two different implementations of the pressure boundary condition, and the conventional staggered mesh (SM). The specific goal is to better appreciate the well known spatial oscillation, or “pressure wiggle”, phenomenon usually attributed to the use of colocated mesh. A modified artificial compressibility method (ACM) and the MAC method were used for the colocated and staggered mesh calculations, respectively, but the focus of our findings is on the converged steady state results which pertain more to the asymptotic steady state discretization scheme (i.e. SM or CM) than the pseudo-time iteration method for obtaining these asymptotic solutions. Two different implementations of the pressure boundary condition were employed in conjunction with the ACM: 1) the requirement that the boundary pressure acts so that the continuity equation is satisfied at the boundary or 2) the requirement that the normal pressure gradient on the boundary satisfies the Navier-Stokes equation. Sample 2D and 3D calculations are performed on the driven cavity problem using these three techniques for a Reynolds number of 100. The results of these sample calculations are analyzed based on solutions available in the literature, and a comparison is made between the various methods and boundary condition implementations. The colocated mesh results indicate that the spatial oscillations, when present, were never greater than the overall accuracy, which is judged to be consistent with expected truncation errors of the various methods. The major objections of the oscillations are thus cosmetic rather than substantive. Furthermore, when the normal pressure gradient condition from the Navier-Stokes equation is used in conjunction with a colocated mesh, the spatial oscillations in the computations are significantly reduced for the pressure and are essentially non-existent for the velocities. These results suggest that the colocated mesh, with artificial compressibility or with other methods of computation, is a viable discretization scheme without the use of complex interpolation schemes to simulate a staggered mesh.
Design, Fabrication and Static Test of a Resonant Microaccelerometer
Authors: Kim Si Young , Go Jeung Sang , Cho Young-Ho
Published: March 2022

This paper investigates a resonant microaccelerometer that measures acceleration using a built-in micromechanical resonator, whose resonant frequency is changing due to an acceleration-induced axial force. From a structural analysis, design equations for the resonant microaccelerometer have been developed and have included analytic formulae for the resonant frequency, sensitivity, nonlinearity and maximum stress in the mechanical structures. On this basis, the sizes of the accelerometer are designed for a sensitivity of 10−3g/Hz over the bandwidth of 100Hz, while satisfying the maximum nonlinearity of 5%, the minimum shock endurance of 100g, the detection range of 5g and the size constraints placed by microfabrication process. A set of the resonant accelerometers has been fabricated by an integrated use of bulk-micromachining and surface-micromachining techniques. From on-chip test structures, the Young’s modulus of polysilicon is measured in the range of 60∼100GPa. The residual stress of polysilicon structures was reduced to 362.1kPa by the annealing process performed for 2 hours at 1000 C in N2 atmosphere. From a static test of the resonant accelerometer, a frequency shift of 860Hz has been measured corresponding to the deflection of the proof-mass by 4.3±0.5μm; thereby obtaining the detection sensitivity of 0.92±0.11 × 10−3g/Hz. Uncertainty in the resonant frequency output has been evaluated to identify important issues involved in the design, fabrication and testing of the resonant accelerometer.
Optimization of the Silicon/PZT Longitudinal Mode Resonant Transducer
Authors: Lai Amit , White Richard M.
Published: March 2022

An analytical electromechanical model of a silicon/PZT laminate longitudinal mode resonant transducer is presented. The validity of this model is shown by the excellent agreement between the predicted and measured impedance of transducers with different device parameters. The experimental data also show a maximum value of 34 for the product of the quality factor and the effective electromechanical coupling. This figure of merit product, an indication of the power output capacity of a transducer, is two to three times higher than that of metal-based transducers. Additionally, silicon can sustain eight times higher ultrasonic velocities than high-strength titanium alloys, indicating that silicon-based ultrasonic transducers can produce much higher intensities efficiently.
Micromachined RF Signal Switching Devices on High Resistivity Silicon Substrates
Authors: Yao Zhimin J. , Goldsmith Chuck , Eshelman Susan , Denniston David
Published: March 2022

The development of a micromechanical capacitive microwave switching device is described in this paper. The switching element consists of a thin metallic membrane. Micromechanical membrane switches have several advantages compared to FET or p-i-n diode switches, such as: low loss, low cost, and low DC power requirements. Compared with the cantilever type of mechanical switches, metal membrane switches have faster switching speeds, lower switching voltages and less stiction problems. This paper presents the design, fabrication and test results of membrane switches. Some important process related issues are discussed.
Theoretical Determination of the Laser Induced Damage Threshold for Ultrashort Pulse Laser Heating of Metal Films
Authors: Smith Andrew N. , Norris Pamela M. , Lee Anthony S.
Published: March 2022

Non-equilibrium heating between electrons and the crystalline lattice has been observed in numerous ultrashort pulsed laser applications yielding unexpected temperature profiles. Typically, laser induced damage threshold (LIDT) values for thin metal films are predicted using the melting temperature and the standard heat diffusion equation. A method is presented which accounts for non-equilibrium heating by solving the Parabolic Two Step (PTS) heat conduction model and deriving an analytical expression for the laser power that causes the film temperature to exceed a critical value. This critical temperature is a design parameter dependent on the material properties of the film and often the repetition rate of the source. In non-equilibrium heating, the predicted peak lattice temperature is significantly lower and occurs at some time after the deposition of energy, which can be orders of magnitude greater than the pulse duration. This minimizes the effect of the temporal shape of the pulse and allows for an analytical solution. This solution and an equation which can be used to calculate the thermal damage threshold value for non-equilibrium laser heating are presented.
Genetic Algorithm Simulation for Deposited Structure of Atoms
Authors: Miyazaki Koji , Hijikata Kunio , Inoue Takayoshi
Published: March 2022

Molecular simulations using a genetic algorithm are conducted in the present study to investigate stable structures of clusters and deposited atoms on a substrate. First, the total potential energy of a n-atoms cluster is calculated for various atom configurations, where an icosahedron is found to be the stablest structure of a 13-atoms cluster. Secondly, stable structures of deposited atoms on a solid surface are investigated. The simulation shows that deposited atoms have either an island or a layer structure, depending on the combination of intermolecular potentials between the deposited and substrate atoms. In addition, a new idea of introducing a temperature concept into the simulation is proposed and evaluated, for examining temperature effects on the stable atom structures. The present solutions agree qualitatively with results from molecular dynamics simulations as well. In spite of demanding a little computing power, calculations can be expected to simulate most well-known stable molecular structures. From the study, it is confirmed that the genetic algorithm is an effective technique for examining stable structures of clusters and thin film.
Direct Contact Melting Process on a Spherical Heating Wall With an Arbitrary Temperature Distribution
Authors: Oka Mineo
Published: March 2022

Direct contact melting process takes place in a lot of technological processes. One of the important applications is in the thermal storage system. In this system, phase change material is stored in small spherical capsules. Diameter of the capsule is about 4 inches. Millions of capsules are packed in a thermal storage tank. Capsules are heated and cooled through brine. Direct contact takes place in the melting process of the thermal storage system. In this system, latent heat energy is used effectively. This paper presents a theoretical study of the direct contact melting process on a spherical heating wall that has arbitrary temperature distribution. Governing system of equations with heat convection terms is solved analytically. It is shown that it can be transformed into ordinary differential equations system by a similarity transformation. Temperature is solved using perturbation method. This solution is valid for almost all practical Stefan number. Analytical solution is obtained for a typical temperature distribution. It is shown that melting rate is enhanced by more than 10% by the effect of temperature distribution.
Thermophotovoltaic Energy Conversion Technology Development at NASA Lewis Research Center
Authors: Wilt David M. , Chubb Donald L.
Published: March 2022

NASA Lewis Research Center (LeRC) has had an ongoing research program in TPV since the late 1980’s. This effort has included both in-house research programs on critical components such as photovoltaic cells (PV) and emitter materials, as well as an active contracting effort directed toward system and component development. Of particular note is the in-house development of thin film selective emitters fabricated from rare-earth yttrium aluminum garnets (YAG). These emitters have demonstrated in-band emittances of > 0.7 with low out of band emittances (∼0.2). Rare earth elements have a unique valency which allows them to behave as isolated atoms even when at solid state densities (i.e. produce line emission rather than grey body emission). Each element has a characteristic emission frequency (wavelength) and YAG selective emitters with emissions peaks ranging from 0.98μm to > 2μm have been demonstrated. In addition, it has been demonstrated that two rare earth elements can be added to the same emitter for increased the power density.

Also developed at LeRC is a Monolithically Interconnected Module (MIM) consisting of many small InGaAs cells series interconnected on a single InP substrate. An infrared reflector placed on the rear surface of the substrate returns unabsorbed photons to the emitter for recycling. The MIM design has many advantages such as: high output voltages and low currents, improved reliability, minimized losses associated with emitter non-uniformity (i.e. variation in view factor, temperature, etc.), high output power density, simplified system design and simplified thermal management. MIM devices with excellent photoresponses and IR reflectivity’s > 82% have been demonstrated.

The contracted efforts include a TPV system development by Tecogen, Inc., based on ytterbia fibrous selective emitters and silicon PV devices. Two (2) prototype TPV systems were constructed, each including recuperators, non-premixed combustor designs, dielectric interference filters and PERL silicon TPV PV cells. Emitters temperatures of 2000K were routinely achieved and both systems have logged many hours of testing. Also under contract development are solar powered TPV systems, InGaAsSb PV devices and plasma-sprayed selective emitters.
Numerical Simulation of Molten Carbonate Fuel-Cell Power-Generation Systems
Authors: He W. , Chen Q.
Published: March 2022

This paper provides a dynamic simulation model for investigation of the characteristics of molten carbonate fuel cell (MCFC) systems. To achieve the accuracy of the system model, the essential component model (i.g. fuel cell stack) is first established in three-dimensional, dynamic form, and it is then simplified prior to incorporation into the system model. The development of simulation techniques, such as estimation of variable limits, connection between component models, definition of input variable variation, and selection of simulation time step, has resulted in successful simulations.

The stationary simulation results for the entire load range show that the fuel cell system has the highest efficiency at partial load (45% full load). The dynamic simulation results indicate the existence of dynamic interactions between the stack and reformer under load-up operation. Moreover, the investigation has evaluated the alternative operation strategy of providing fuel gas directly to the reformer combustor during load-up mode. This alternative strategy has significantly reduced the dynamic interactions. The model has also been used to select the location of the fuel flow control valve. These results can be used to improve MCFC system operation and control design.
Modeling and Experimental Verification of a Perforated Plate-Fin Absorber for Aqua-Ammonia Absorption Systems
Authors: Garrabrant Michael A. , Christensen Richard N.
Published: March 2022

Modeling with experimental verification is presented for a novel Perforated Plate-Fin Absorber (Perforated Fin Absorber), developed for utilization in aqua-ammonia absorption chillers and heat pumps. The Perforated Fin Absorber’s (PFA) unique construction provides high heat and mass transfer efficiencies and simple fabrication, necessary for the residential and small commercial absorption cooling markets.

The PFA is comprised of a perforated fin sandwiched between cooling channels augmented with offset strip fin. Counter flow, falling film absorption (solution down, vapor up) occurs in the perforated fin cavity. The perforations are sized and spaced to prevent flooding and provide solution distribution. Coolant flow in the offset-strip fin cavities is counter to the solution flow.

The PFA was modelled using a combined heat and mass transfer analysis. Two laboratory prototypes were constructed and tested over a range of solution flow rates and concentrations. The experimental data was utilized to verify and calibrate the design model. Experimental results verify that the PFA geometry provides very high absorption rates over a wide range of operating conditions.
Heat Transfer Coefficients of Zeotropic Refrigerant Mixtures and Their Pure Components in Horizontal Flow Boiling: An Experimental Study
Authors: Rohlin Peter
Published: March 2022

The paper deals with an experimental study of flow boiling heat transfer coefficients in horizontal tubes. The experiments are performed in an electrically heated thermosiphon loop with two different evaporator tube diameters. Measurements are performed with constant heat flux along the tube and at relatively low heat and mass fluxes. The gravitational forces will influence the flow pattern and incomplete wetting of the tube walls will occur in a great part of the measurements. The tests are performed with the pure substances R22, R142b, R32 and R134a as well as several mixtures of R22/R142b and R32/R134a. The two tube dimensions tested have quite different behavior in spite of having the same length and refrigerant distribution system.

A Chen-type correlation is chosen to predict the local heat transfer coefficients. The influences on the heat transfer coefficient of incomplete wetting are correlated by correcting the enhancement factor by a function of the Froude number. The correlations obtained for the two tube diameters and with pure refrigerants are then used as basis for the evaluation of the refrigerant mixture tests.

The degradation of the heat transfer coefficient for mixtures is discussed. The measured mixture heat transfer coefficients are well estimated by using Jung’s correlation for mixtures, if Jung’s enhancement factor is replaced by the enhancement factors evaluated from the tests and the real mixture transport properties are used or by the theoretically approached correlation by Granryd.
Refrigeration Lubricants for R-407C
Authors: Macaudière Sylvie , Rolotti Gustavo D. , Sanvi Pierre
Published: March 2022

Miscibility between refrigerants and lubricants has long been considered essential to the refrigeration cycle. Many compounds that have been proposed for use as lubricants for hydrofluorocarbons (HFC) have polar molecular structures in order to be fully miscible with the refrigerants. However, it seems difficult for these lubricants to maintain long term durability in rotary compressors when R-407C is used.

In order to overcome the durability problem, a new type of lubricant has been developed that sacrifices some of its miscibility in return for better anti-wear properties.

This paper presents new methods for selecting the best lubricant for future air conditioning applications.
The Development of Analytical Models for Predicting Viscoelastic Damping in Woven Fabric-Reinforced Polymer Matrix Composites
Authors: Guan Huimin , Gibson Ronald F.
Published: March 2022

This paper describes the development of a closed-form model and a finite element model for studying viscoelastic damping in woven fabric-reinforced polymer matrix composites. The closed-form model was obtained by first deriving an elastic solution based on the mechanics of materials theory, then applying the Elastic-Viscoelastic Correspondence Principle to the elastic solution. The damping loss factors were determined from the complex moduli. Three-dimensional finite element models with various mesh densities were constructed based on the actual geometry of a plain weave fabric-reinforced composite unit cell. Three different loading cases were designed to simulate extensional, shear and bending deformations of the unit cell. The strain energies stored in the fiber and matrix elements for each loading case were conveniently determined from the finite element analysis. A strain energy formulation was used to calculate the damping loss factors for each loading case. Experiments were conducted using an impulse-frequency response technique to measure damping in beam samples made of plain weave E-glass fabric-reinforced vinyl ester resin matrix composite. The predictions from both analytical models show reasonably good agreement with experimental data.
Ultrasonic and Acoustic Emission NDE of a Graphite/Epoxy T-Joint
Authors: Dayal Vinay
Published: March 2022

This paper deals with the Ultrasonic Non Destructive Testing of a T-Joint Graphite/Epoxy composite. The T-beam is then subjected to compression loading and Acoustic Emission recording is used to follow the buckling and delamination growth in such structures.
The Effect of Toughened Composites on Dynamic Behaviors of Composite Laminates Under the In-Plane Dynamic Load
Authors: Jia Hongyu , Rogers Craig A.
Published: March 2022

In order to investigate the effect of toughened composites on the dynamic behavior of the laminated composite plates under in-plane loading, a simply supported laminated composite plate under the axial in-plane dynamic load is studied. A model for symmetric cross-ply laminated composite plate is presented here. The gorvening equations of motion are obtained by using Lagrange equations. The laminated composite plates are made from various composite materials, such as, Graphite/Epoxy, Graphite/PEKK, Graphite/PEEK, and Kevlar/PEKK. This model considers the large strain, transverse inertia, and neglects the in-plane inertia. The static critical buckling load is determined. The static part and the amplitude of dynamic part of the load are less than the static critical buckling load. Dynamic buckling of the laminated composite plates is studied for dynamic instability regions and primary responses. Linear solution for dynamic instability region is obtained. Also, the linear natural frequencies are determined for different compressive loads and materials. Nonlinear solution for primary responses is also obtained. The effects of the toughened composites on the dynamic buckling responses of the plates are evaluated.
Boundary Element Method for High Frequency Acoustic Analysis
Authors: Raveendra Satha T. , Thompson James K. , Mollo Chris M.
Published: March 2022

A boundary element formulation based on energy flow is developed for the analysis of high frequency acoustic problems. Unlike traditionally modelled acoustic pressure and velocity variables, the variation of space-averaged energy density at high frequencies is rather smooth and therefore energy parameters are well suited for the description of acoustic behavior. The governing differential and integral equations based on energy variables are similar to the Helmholtz equations for acoustic problems based on pressure and velocity variables and thus the extension of existing solution techniques for the solution of integral equations based on energy flow parameters is rather straightforward.
Intelligent Tool Wear Estimation for Precision Cutting Tools
Authors: Suchorucov U. N. , Derevianchenco A. G.
Published: March 2022

This paper presents a new algorithm for the direct inspection of the cutting tool wear. The place of the direct inspection is discussed. It is shown hat direct inspection does not require to establish experimentally a number of correlations amongst the cutting process parameters for each particular cutting regime, the tool and the workpiece involved. The main difficulty associated with the direct methods is the graphical representation of the wear topology using the results of the measurements. The basic principles associated with such representation are discussed. The cutting tool is represented by a set of initial geometrical parameters which constitutes its initial shape. Then, this set is used for the comparison with that of the partially worn tool to distinguish the wear topology. A number of computer program for the built-in computers of CNC machine tools are developed on the base of the proposed approach.
Engaged Cutting Edge Effects on Tool-Wear and Tool-Life in Turning Operations Using Grooved Cutting Tools
Authors: Li P. X. , Stein D. , Ghosh R. , Jawahir I. S.
Published: March 2022

This paper presents a systematic approach to the assessment of tool-wear/tool-life and provides a new relationship between the effective engaged cutting edge and tool-wear in machining with grooved tools. It is found that the tool-wear patterns change with varying cutting edge angles and nose radii; both of which affect the engaged length of the cutting tool. Four different cutting edge angles and nose radii are tested. Tool-life is then validated by a new tool-life equation which includes the operational effects of the cutting edge angle and the tool nose radius.
Tool Path Generation Using C-Space for 5-Axis Machining
Authors: Morishige Koichi , Takeuchi Yoshimi , Kase Kiwamu
Published: March 2022

The paper deals with the method of tool path generation for 5-axis machining using a ball end mill. 5-axis machining has been used for aircraft parts as well as for complicated shapes such as molds and dies. However, most of the present CAM systems for 5-axis machining have limited functions in terms of tool collision, workpiece shapes and machining methods. For that reason, in many cases the optimal cutter location (CL) data cannot be obtained or considerable time is consumed. To solve this problem, we have applied a 3-dimensional configuration space (C-Space) and showed the relationship between all tool positions and postures and the existence of tool collision. The method of tool path generation devised in the study enables users to generate CL data reflecting their own machining strategy such as smooth change in tool posture and the state of machining without considering the gouging. The validity of this method was experimentally confirmed by successfully milling an impeller without tool collision occurring.
Investigation of a Special 6-6 Parallel Platform for Contour Milling
Authors: Abbasi Waheed A. , Ridgeway Shannon C. , Adsit Phillip D. , Crane Carl D. , Duffy Joseph
Published: March 2022

Recently, companies have been experimenting with parallel-mechanism based approaches for milling machines. This research presents an investigation into the development of a special 6-6 parallel mechanism for application to contour milling. The idea behind this approach is that existing non-CNC milling equipment can be augmented to increase its capability at a lower cost than purchasing traditional 5-axis machining centers. This paper presents the phase of research associated with developing a parametric kinestatic design methodology for a special 6-6 parallel mechanism (Kinestatic Platform, KP). This methodology was applied to the design specifications associated with 5-axis contour milling. The resulting kinestatic design’s dynamics were evaluated to determine the actuation requirements of each connector. A prototype connector was built to allow the evaluation of actuator response under simulated loading conditions. Joint stiffness and control strategy were of primary concern in evaluating the performance of the prototype connector. The parametric kinestatic design and control strategy results are presented. Several observations are evidenced from the research. Joint deflection is an obvious critical issue and the most difficult to quantify. A scheme is proposed detailing the concept of using a separate metrology frame to overcome difficulties associated with accurate connector length determination.
Explicit Dynamic Finite Element Analysis of Laminated Composite Automotive Structures Using a New Composite Plate Element
Authors: Cho Y. B. , Plaskacz E. J. , Averill R. C. , Kulak R. F.
Published: March 2022

Composite materials are being considered for use in the front end structures of vehicles to help reduce overall vehicle mass and, thus, improve fuel efficiency. Acceptance of composite material in structural members will depend on their ability to do crash energy management. Numerical simulations can greatly aid in the design of these critical structures and reduce the number of crash tests. A new finite element, which is based on laminated plate theory with cubic zig-zag approximations, was developed to model the relevant mechanics that occur in composite materials during crash events. The element was cast in the internal force format for use with explicit integration solvers. In the plate theory, the in-plane displacement fields in a laminate are assumed to be piecewise cubic functions and vary in a zig-zag fashion through the thickness of the laminate. The zig-zag functions are obtained by satisfying the continuity of transverse shear stresses at layer interfaces. This in-plane displacement field assumption accounts for discrete layer effects without increasing the number of degrees of freedom as the number of layers is increased. The transverse normal strain predictions are improved by assuming a constant variation of transverse normal stress through the thickness in a laminate. The finite element is developed with the topology of an eight-noded brick. Each node has five engineering degrees of freedom, three translations and two rotations. Thus, this element can be conveniently implemented into general purpose finite element codes. Consistent and lumped mass matrices are derived. The developed element is implemented into Argonne National Laboratory’s in-house code, NEPTUNE, which utilizes explicit direct integration method. In NEPTUNE the internal force vector is calculated from the developed element at each time step. Numerical performance of the current element is investigated in this research.
Steel Post Simulation for the Buffalo Guardrail System
Authors: Reid John D.
Published: March 2022

In previous research, a new guardrail system, called the “Buffalo Rail”, was designed and successfully tested that incorporated wood posts. With the aid of nonlinear finite element analysis, a steel post Buffalo Rail system was designed and successfully redirected a heavy duty 3/4-ton pickup truck.

Although work remains on the Buffalo Rail, it clearly has shown potential to increase the safety performance of guardrail system throughout the world.
Woven Fabric Composite Material Model With Material Nonlinearity for Nonlinear Finite Element Simulation
Authors: Tabiei A. , Jiang Y.
Published: March 2022

The objective of the current investigation is to develop a simple, yet generalized, model which considers the two-dimensional extent of woven fabric, and to have an interface with nonlinear finite element codes. A micromechanical composite material model for woven fabric with nonlinear stress-strain relations is developed and implemented in ABAQUS for nonlinear finite element structural analysis. Within the model a representative volume cell is assumed. Using the iso-stress and iso-strain assumptions the constitutive equations are averaged along the thickness direction. The cell is then divided into many subcells and an averaging is performed again by assuming uniform stress distribution in each subcell to obtain the effective stress-strain relations of the subcell. The stresses and strains within the subcells are combined to yield the effective stresses and strains in the representative cell. Then this information is passed to the finite element code at each material point of the shell element. In this manner structural analysis of woven composites can be performed. Also, at each load increment global stresses and strains are communicated to the representative cell and subsequently distributed to each subcell. Once stresses and strains are associated to a subcell they can be distributed to each constituent of the subcell i.e. fill, warp, and resin. Consequently micro-failure criteria (MFC) can be defined for each constituents of a subcell and the proper stiffness degradation can be modeled if desired. This material model is suitable for implicit as well explicit finite element codes to deal with problems such as crashworthiness, impact, and failure analysis under static loads.
Finite Element Modeling of Experimental Diffuse Axonal Injury: A Parametric Analysis
Authors: Zhou Chun , King Albert I. , Khalil Tawfik B. , Yang King-Hay , Meaney David F.
Published: March 2022

A parametric study on the material properties of the brain tissues was conducted using the 2-D porcine brain model developed by Zhou et al (1994). The animal test condition by Meaney et al (1993) was simulated. Four points in the DAI regions were chosen for evaluation. Changes due to variation of material properties were investigated in terms of shear stress distribution, shear stress magnitude, shear strain magnitude, shear stress time history, shear strain time history, and strain rate. Base on the simulation results, a stress criterion of 20 kPa and a strain criterion of 0.20 were proposed for DAI to occur in the mini pigs. Shear stress/strain contours can be used for DAI predictions. Diffuse axonal injury was found to occur in areas where higher shear stresses or strains persisted for relatively longer periods during impact. It was estimated that the instantaneous shear modulus is in the range of 40 kPa to 120 kPa and the long term shear modulus is in the range of 5 kPa to 8 kPa. The decay factor should be within the range of 350 s−1 and 700 s−1.
Numerical Simulation of Side Impact Sled Tests With Chambered Side Airbag
Authors: Palaniappan Pal , Maripudi Vivek , Wipasuramonton Paul , Tanavde Anand S. , Gudipaty Krish
Published: March 2022

This work describes side impact numerical simulation methodology. It also demonstrates an application of PAM-SAFE finite element program to simulate complex interaction among the vehicle-door system, chambered side airbag, and EUROSID-1 dummy in a side impact sled test which was conducted to meet (EEVC) European side impact standards. The simulation methodology developed herein can be utilized in performing parametric studies to optimize the effectiveness of padding and side airbag system. A typical sled simulation without airbag takes approximately one and a half hours of CPU time on high-end engineering workstations. Problems encountered in modeling dummy and chamber side airbag are also discussed. This study also illustrates effectiveness of head-thorax side impact airbag used with door padding, in improving occupant protection.
Driving PWA Thermomechanical Analysis From Step AP210 Product Models
Authors: Tamburini Diego R. , Peak Russell S. , Fulton Robert E.
Published: March 2022

This paper describes experiences using the STEP AP210 Printed Wiring Assembly (PWA) product model to drive engineering analysis. It describes how this product design data is mapped into an intermediate analyzable representation (the Analyzable Product Model, or APM) which supports the information requirements of several thermomechanical analyses, including product idealizations. Examples from the DARPA-sponsored TIGER project are included, in which AP210 models were generated from the Mentor Graphics board layout tool. The paper describes other issues encountered such as how to integrate product data that spans more than one tool, how to add missing analysis data that is not generated during design, and how to use data stored in the APM from different programming environments.

Experiences show the value of semantically rich product models like STEP AP210 for analysis integration (vs. straight geometry-oriented models like AP203). However, the multi-fidelity idealization nature of analysis leads to an insatiable information appetite that no product model, no matter how rich, can continually satisfy. Thus, the APM technique is necessary as a general link to design tools in order to harmonize diverse data and add idealizations and missing data. Overall, experiences in TIGER confirmed the basic thrusts of the APM approach and its usage of STEP.
Advances in Stress Test Chips
Authors: Jaeger Richard C. , Suhling Jeffrey C.
Published: March 2022

Structural reliability of integrated circuit chips in electronic packages continues to be a major concern due to ever increasing die size, circuit densities, power dissipation, and operating temperatures. A powerful method for experimental evaluation of die stress distributions is the use of test chips incorporating integral piezoresistive sensors, and this paper presents a review of the state-of-the-art in silicon piezoresistive stress sensor test chips.

Resistive rosettes on (100) silicon can be used to measure as many as four components of the six-component stress state whereas advanced test chips based upon (111) silicon can measure the complete stress state. However, not all of the measurements can be performed in a temperature compensated manner which is required for high accuracy results.

Classic resistor rosettes suffer from reduced sensitivity due to high doping levels, and they measure values of the die surface stress averaged over a relatively large area. Advanced stress sensors based upon the piezoresistive response of field-effect transistors are expected to provide improved sensitivity and highly localized measurement of stress sensitivity. Localized high sensitivity measurement can also be provided by new van der Pauw stress sensors.