bluuebunny/crossref_metadata_2025 huggingface dataset:
Regularization Techniques Applied to Nearfield Acoustical Holography
Authors: Williams Earl G.
Published: November 2021

Nearfield Acoustical Holography (NAH) is an inverse problem in wave propagation which has found applications to both interior and exterior noise control problems. We can view the fundamental equation of NAH in the spatial frequency domain as a linear equation, p=Gv, where p is the measured pressure, v is the unknown normal velocity (usually on the surface of a vibrator), and G is the known transfer function. NAH inverts this equation solving for the velocity. However, this equation is ill-posed since small changes in p usually lead to large changes in v. Thus the need for regularization of the inversion. We will discuss regularization techniques applied to NAH, and will compare the errors associated with several regularization schemes; Tikhonov, conjugate gradient, Landweber iteration and a simple exponential filter approach (which appears to provide the best results). Furthermore, in an effort to illuminate the physical propagation mechanisms of NAH, we will discuss these approaches in the light of k-space.
Correcting a Significant Bias Error in the Modal Damping Determined Using Transient Vibration Data
Authors: Ratcliffe Colin P.
Published: November 2021

This paper investigates the experimental vibration technique of impact excitation when used to determine modal damping. Current practices introduce a consistent bias error in the derived modal damping estimates. The error can be significant, with levels of damping being wrongly predicted by a factor of three or more. This paper identifies the source of the error, and derives a simple correction to be applied to the observed modal damping estimates. The procedure is demonstrated by experiment and the results of a round robin exercise.
Vibration Response of Multi-Functional Z-Pin Space Core Sandwich Composites
Authors: Vaidya Uday K. , Nelson Scott P. , Ulven Chad , Mathew Biju
Published: November 2021

Sandwich composite constructions that possess several multi-functional benefits in addition to providing structural strength and stiffness have been investigated in the current work. In comparison to traditional foam and honeycomb cores, the Z-pin reinforced space core provides multi-functionality to route wires and rods, embed electronic assemblies, store fuel and fire-retardant foam and provide tailored damping in structures among other conceivable benefits. The present study deals with vibration characterization of Z-pin sandwich plates with hollow and foam-filled core. A finite element study has been conducted on hollow Z-pin core sandwich panels to investigate the stiffness reduction associated with Z-pin buckling.
The Use of Multifunctional Composite Materials in Large Scale Naval Applications
Authors: Crane Roger M.
Published: November 2021

The U. S. Navy has a long-standing history of ship design using metals. With the improvements in weapon systems, it is becoming increasingly critical to design ship structures not only to satisfy the structural loading but also to exhibit additional multifunctional properties. This is becoming evident with structures such as the Advanced Enclosed Mast Sensor System, AEM/S, which was installed on the USS Radford. This structure was designed to house radar systems and allow the passage of certain radar frequencies through the structure while simultaneously not allowing the penetration of radar at other frequencies. In addition, the structure was designed to reduce the ship’s detectability.

This paper will present a summary of the large-scale composite manufacturing that is being considered for Naval Structures. These structures are being manufactured using low-cost manufacturing techniques and are incorporating multifunctional characteristics in addition to meeting the structural requirement of the application. This paper will provide a historical discussion on the use of composite applications in the surface fleet.
Sudden Drop Phenomena in Natural Frequencies of Composite Plates or Panels With a Non-Central (or Eccentric) Stiffening Plate Strip
Authors: Yuceoglu U. , Özerciyes V.
Published: November 2021

In this study the free bending vibrations of compsite base plates or panels reinforced by a non-central (or eccentric) stiffening plate strip are considered. The base plate and the stiffening plate strip are dissimilar orthotropic plates. They are connected by a very thin and flexible adhesive layer. The dynamic equations of the entire composite plate system are obtained from the “Mindlin Plate Theory” for orthotropic plates. The set of the governing partial differential equations of the composite plate or panel system are reduced to a set of first order ordinary differential equations by the elimination of the time variable and one of the space variables. This final system of the first order differential equations in one space variable is integrated by the “Modified Version of the Transfer Matrix Method”. It was shown that the natural frequencies, at any mode, of the plate or panel system gradually increase at first with the increasing “Bending Cross Stiffness Ratio”. After then, for certain values of this “Ratio”, the natural frequencies for each mode, suddenly drop to a lower value and subsequently start to go up, although slowly, regardless of the support conditions. This unusual “Sudden Drop Phenomena” is explained in detail and, also, the mode shapes corresponding to the sudden drop are presented. The effect of the “hard” and the “soft” adhesive layer on the “Phenomena” are also shown.
Effects of Cure State on the Ultrasonic Nonlinear Parameter in Adhesive Joints
Authors: Liu Guoli , Qu Jianmin , Jacobs Laurence J.
Published: November 2021

The objective of this paper is to characterize the cure state of polymer adhesive joints using nonlinear ultrasonic techniques. To this end, through transmission tests were carried out on joint samples that had been subjected to various curing conditions. In these tests, a 40-cycle harmonic signal was generated by a 2MHz narrow-band PZT transducer as the incident wave. The wave transmitted through the adhesive joint was received with a 4MHz narrow-band PZT transducer. The magnitude of the second order harmonics in the transmitted signal was measured and the corresponding nonlinear parameter β was calculated. A fairly good correlation was observed between the nonlinear parameter and the cure state. It was found that under-curing (lower curing temperature or short curing time) tends to increase the nonlinear parameter.
Parametric Studies of Gas Turbine Combustion NOx Emissions Using KIVA With a Reduced Mechanism
Authors: Su K. , Zhou C. Q.
Published: November 2021

A numerical study was conducted to determine the effects of combustion condition parameters, including inlet temperature and pressure, fuel spray characteristics on NOx emissions in gas turbine combustion using the KIVA-3V code. Log-normal spray distribution was assumed for the simulation of real fuel spray distributions at injection. A simplified mechanism with 17-species and 26-step was employed for chemical reactions of Jet A in a formula of C12H23. A sector model of a typical annular combustor was used in calculations. Flow fields and temperature distributions were analyzed. A wide range of operating condition was varied with the inlet pressure from 0.1 to 2.0 MPa, inlet temperature from 400 to 900 K, and overall fuel/air ratio from 0.012 to 0.08. The results reasonably agreed with those from experimental data and Chemkin modeling, which demonstrates the applicability of KIVA-3V and the chemical mechanism to the predictions of NOx emissions. With respect to the inlet temperature, NOx productions show a trend of monotone increasing. As the inlet pressure increases, NOx emissions increase at the beginning and then decrease. The droplet mean diameter as well as injection velocity and angle were independently varied to distinguish the separate effects of variables involved. It is found that the NOx emissions decrease with the Sauter mean diameter, but increase with the injection velocity and angle of fuel sprays. It appears that KIVA-3V code can be a valuable tool for the development of low emission combustors.
Numerical Prediction of the Transient Operation of a Gas-Fired Reheating Furnace
Authors: Correia Sara A. C. , Ward John , Sousa João L. V. A.
Published: November 2021

The well-known “zone method”, treats thermal radiation in an enclosure in a global manner so that reliable estimates of this mode of heat transfer can be obtained in systems such as gas-fired furnaces. Consequently the paper employs a two-dimensional thermal radiation model in which both the height and length of the furnace was divided into surface and volume zones. An isothermal computational fluid dynamics simulation was used to estimate the relative mass flow rates, and hence enthalpy flows, into or out of each volume zone. This simplified approach was considered to provide a reasonable estimate of the appropriate inter-zone mass flows since the use of small-scale experimental, near ambient temperature models has been shown in the past to give useful data on flow related behaviour of combustion systems. The computing times resulting from the coupling of a multi-zone model with a single isothermal computation of the flows are relatively short so that the transient performance of the reheating furnace can be analysed. The mathematical model was thus used to predict the fuel consumptions and load temperatures in a gas-fired furnace heating steel bars to a nominal discharge temperature of 1250°C over a typical transient operating period of 8 hours including the start-up from cold. The influences of burner geometry as well as the effects of changes to the value of the roof set point temperature which was used to control the thermal input to the burners were studied. The effects of varying the position of the roof temperature control sensor relative to the burners and of changes in the roof construction were also investigated.
On the Effectiveness of Aerodynamic Design and Analysis for Centrifugal Compressors
Authors: Aungier Ronald H.
Published: November 2021

Effectiveness is promoted as an essential feature of a centrifugal compressor aerodynamic design and analysis system. Effectiveness measures the system’s ability to apply sound technology to the wide range of functions the centrifugal compressor engineer needs to perform to develop, apply and maintain these complex machines. Effectiveness compliments efficiency (or productivity) in the overall evaluation of a design and analysis system. This paper discusses several features that an effective aerodynamic design and analysis system should have to support the design and application of industrial process centrifugal compressors. These features are known to be occasionally (if not often) neglected. Yet they all can be incorporated using technology available from the open literature.
Aerodynamic Analysis of Return Channels of Multi-Stage Centrifugal Compressors
Authors: Lenke L. J. , Simon H.
Published: November 2021

From the wide range of applications in which centrifugal compressors are used, two different return channels will be investigated, to demonstrate the influence of flow coefficients onto the flow structure. The investigated return channels are typical to join the exit from one stage of a centrifugal machine to the inlet of the next stage and cover the range of very small and large flow coefficients.

Starting with a comparison between measurements and numerical results to demonstrate the performance of the calculations, the comparison of both return channels show that three-dimensional phenomena and viscous effects such as secondary flow and wakes have appreciable effect on the fluid dynamics and performance of centrifugal compressors. Especially the deceleration of the flow introduces large separations and recirculations which will decrease the efficiency.

Furthermore, a variation of the 180°-bend demonstrates the influence of streamline curvature onto the separation behaviour within the whole return channel.

Due to the strongly three-dimensional flow structure with high streamline curvature and secondary flows on hub and shroud of the return channel vanes, a modified explicit algebraic Reynolds stress model will be used for all calculations.
Fabrication of Porous NiTi Shape Memory Alloy by Elemental Powder Sintering
Authors: Thangaraj K. , Chen Y. C. , Salama K.
Published: November 2021

Porous equi-atomic NiTi Shape Memory Samples were fabricated using the Elemental Powder Sintering technique for varying starting powder sizes of Ni and Ti. The porosity was primarily dependent on the starting powder sizes, and less dependent on the sintering parameters and compaction loads. Sintering at higher temperatures of 1120°C and 48 hrs resulted in a completion of reaction to equilibrium NiTi. The average pore size was found to be in proportion to the starting powder size. The martensitic-austenitic transformations as determined from the electrical measurements had a broad transformation behavior. Compressive tests performed on the sample showed a recoverable strain of up to 2.5 %.
Transient Thermal Stress Analysis of an Interior Crack in Functionally Graded Materials
Authors: Jin Zhi-He , Paulino Glaucio H.
Published: November 2021

An internal crack in a strip of a functionally graded material (FGM) is studied under transient thermal loading conditions. The FGM is assumed having constant Young’s modulus and Poisson’s ratio, but the thermal properties of the material vary along the thickness direction of the strip. Thus the material is elastically homogeneous but thermally nonhomogeneous. This kind of FGMs include some ceramic/ceramic FGMs such as TiC/SiC and MoSi2/Al2O3, and also some ceramic/metal FGMs such as zirconia/nickel and zirconia/steel. Thermal stress intensity factors (TSIFs) are calculated for a TiC/SiC FGM with various volume fraction profiles of the constituent materials. It is found that the TSIF could be reduced if the thermally shocked cracked edge of the FGM strip is pure TiC.
Large Deformation Thermal-Plasticity in a Shape Active Aluminum Metal Matrix Composite
Authors: Armstrong William D. , Lorentzen Torben
Published: November 2021

The present work reports macroscopic thermal mechanical and in-situ neutron diffraction measurements from a 14.4 volume percent, 50.7 at% Ni-Ti fiber actuated 6082-T4 aluminum matrix composite and 6082-T4 homogeneous aluminum control material subjected to a room temperature 5% tensile elongation, and subsequent room temperature to 120 deg. C unconstrained heating process. During the unconstrained room temperature to 120 deg. C heating process, the composite exhibited a 2.2%, nonlinear thermal contraction, while the homogeneous control exhibited the expected linear thermal expansion. The composite thermal compression was clearly the result of a powerful shape memory response in the actuating NiTi fibers. During a subsequent temperature hold at 120 deg. C the composite exhibited an external stress free compressive creep response. The compressive creep behavior was the result of matrix creep under the large compressive stresses imposed by the shape memory active NiTi fibers. In summary, the experimental composite has demonstrated a new form of large deformation self thermal-plastic response which may be used in thermally controlled adaptive machine parts and structures.
Design and Testing of a Turbomachinery Dynamics Simulator
Authors: Duffield Colin J. , Agnes Gregory S.
Published: November 2021

A novel flywheel exitation system for examining the dynamics of bladed-disk assemblies is presented. The excitation is rotated allowing a stationary hub reducing the cost of the testing while maintaining the essential dynamics which lead to HCF failure in turbomachinery. The success of this measurement system offers a new experimental tool to further advance our understanding of bladed-disk dynamics.
The Effect of Mechanical Prestress on Dielectric and Piezoelectric Response of PZT-5H at High Electric Fields
Authors: Chaplya Pavel M. , Carman Gregory P.
Published: November 2021

The dielectric and piezoelectric response of PZT-5H ceramics at high electrical and mechanical loads is presented. The purpose of this study is to provide a detailed explanation of the effect of prestress on the induced polarization and strain. The material is electrically cycled (−2/+2 MV/m, 0/+2 MV/m, and −0.4/+2 MV/m) at constant mechanical prestress levels up to 175 MPa. A descriptive model is used to explain the results in terms of consecutive non-180° domain wall motion only. The response of the material depends on the non-180° domain wall motion produced by the balance between the applied electric field and prestress. The limitation of the model is that it neglects 0° and 180° domains contribution to the response of the actual material.
Dielectric Properties of 0.9PMNTa-0.1PT Relaxor
Authors: Tang Feng , Wang Jin T.
Published: November 2021

Ta-Modified lead magnesium niobate-lead titanate crystalline solutions 0.9PbMg1/3(Nb(1−x)Tax)2/3O3-0.1PbTiO3 (PMN-PT) were first synthesized. The dielectric constant and the dielectric loss of the ceramic for different compositions as a function of frequency and temperature were measured using a Hewlett Packard 4284A LCR precision meter, which can cover a frequency range from 20 to 106Hz in a Delta 9039 test chamber operated between −75°C to +330°C. Dramatic changes of the dielectric properties were observed in Ta-modified 0.9PMN-0.1PT. It was noticed that the samples with appropriate amount of Ta-doping (x = 0.1, 0.2, and 0.3) have smaller grain size, larger dielectric constant, and lower dielectric loss than those of the specimens without doping (x = 0.0) or over doping (x = 1.0) in the frequency band of 100 – 105Hz. Proper Ta-doping in PMN-PT also resulted in a weaker frequency dispersion. It was also found that with increasing of Ta addition x, the transition temperature shifts downward to the lower temperature and the peaks of the dielectric constant versus temperature are getting sharper. Ta-doped PMNTa-PT shows a typical relaxor behavior.
Continuous Sensors for Structural Health Monitoring
Authors: Ghoshal Anindya , Sundaresan Mannur J. , Schulz Mark J. , Pai P. Frank
Published: November 2021

An active fiber composite tape with segmented electrodes was modeled for use as a continuous sensor for structural health monitoring. The material has unidirectional piezoceramic fibers with interdigital electrodes on the top and bottom surfaces and is poled in the fiber direction. The elastic response of a plate with the modeled sensor was computed in closed form at small time steps, and the coupled piezoceramic constitutive equations and the electrical circuit equations were solved. Sensor voltages and wave propagation responses were computed in the simulations. The simulations indicate that such a sensor will be capable of detecting damage to the plate from the changes in the wave propagation response. Further, the sensor has adequate sensitivity to detect fiber breaks in the composite plate making it useful for both passive and active interrogation. A continuous sensor comprised of PZT patches was tested to measure simulated acoustic emissions on panel structures. The sensor was shown to reduce the number of channels of data acquisition required to detect simulated acoustic emissions in a fiberglass panel, but the source of the emission is not precisely determined.
Active Control of Periodic Structures
Authors: Baz A.
Published: November 2021

Conventional passive periodic structures exhibit unique dynamic characteristics that make them act as mechanical filters for wave propagation. As a result, waves can propagate along the periodic structures only within specific frequency bands called the “Pass Bands” and wave propagation is completely blocked within other frequency bands called the “Stop Bands”.

In this paper, the emphasis is placed on providing the passive structures with active control capabilities in order to tune the spectral width and location of the pass and stop bands in response to the structural vibration.

Apart from their unique filtering characteristics, the ability of periodic structures to transmit waves, from one location to another, within the pass bands can be greatly reduced when the ideal periodicity is disrupted resulting in the well-known phenomenon of “Localization”. In the case of passive structures, the aperiodicity (or the disorder) can result from unintentional material, geometric and manufacturing variability. However, in the case of active periodic structures the aperiodicity is intentionally introduced by proper tuning of the controllers of the individual substructure or cell.

The theory governing the operation of this class of Active Periodic structures is introduced and numerical examples are presented to illustrate their tunable filtering and localization characteristics. The examples considered include periodic/aperiodic spring-mass systems controlled by piezoelectric actuators.

The presented results emphasize the unique potential of the active periodic structures in controlling the wave propagation both in the spectral and spatial domains in an attempt to stop/confine the propagation of undesirable disturbances.
Simultaneous Structure-Control Optimization of a Steering Wheel for Vibration Suppression
Authors: Zhu Ye , Qiu Jinhao , Tani Junji
Published: November 2021

This paper presents both simulation and experimental investigation into the simultaneous design of a steering wheel and its control system for vibration suppression. The research can be divided into two stages. In the first stage, the simultaneous design is formulated as a nonlinear programming problem in which the H∞ norm of the closed-loop system is minimized with respect to the structural parameters and the control parameters. For the convenience and efficiency of using existing control design tools, the original formulation is replaced by a nested one in which only the structural parameters are used as explicit design variables in the main optimization and for a given structure, a sub-optimization is carried out to find the corresponding optimal control parameters. The design obtained by simultaneous optimization is compared with the original structure combined with the corresponding optimal controller and the effectiveness of the simultaneous optimization is verified by simulation. In the second stage, experiments are performed to evaluate the design of simultaneous optimization. For simplicity, standard H∞ control is used in the first stage and the effects of modeling error and system uncertainty are not considered. However, dealing with these factors is important issue in a real structure-control system. Since μ synthesis is a systematic robust control method to analyze and quantify the effects of uncertainty, it is adopted in the experimental evaluation. The experimental result shows that the optimized structure is still superior to the original one after the controllers are redesigned in the framework of μ synthesis.
Bifurcations in a Mathieu Equation With Cubic Nonlinearities
Authors: Ng Leslie , Rand Richard
Published: November 2021

We investigate the nonlinear dynamics of the classical Mathieu equation to which is added a nonlinearity which is a general cubic in x, ẋ. We use a perturbation method (averaging) which is valid in the neighborhood of 2:1 resonance, and in the limit of small forcing and small nonlinearity. By comparing the predictions of first order averaging with the results of numerical integration, we show that it is necessary to go to second order averaging in order to obtain the correct qualitative behavior. Analysis of the resulting slow flow equations is accomplished both analytically as well as by use of the software AUTO.
Rubbing Phenomena in Rotor-Stator Contact
Authors: Feng Z. C. , Zhang Xiao-Zhang
Published: November 2021

This paper discusses the vibration phenomena of a rotor rubbing with a stator caused by an initial perturbation. The analytical model consists of a simple disc-shaft rotor and a fixed stator. The perturbation is an instantaneous change of the radial velocity when the rotor is rotating in its normal steady state. It is found that under certain conditions, the rotor will remain rubbing with the stator, even if the initial perturbation no longer exists. In the case of no friction on the contact surface between the rotor and the stator, the full rubbing behaves as forward whirling. When friction is present, the full rubbing behaves as backward whirling.
Hamilton’s Principle for External Viscous Fluid-Structure Interaction
Authors: Benaroya Haym , Wei Timothy
Published: November 2021

In this paper, Hamilton’s principle is extended so as to be able to model external flow-structure interaction. This is accomplished by using Reynold’s Transport theorem. In this form, Hamilton’s principle is hybrid in the sense that it has an analytical part as well as a part that depends on experimentally derived functions. Examples are presented. A discussion on implications and extensions is extensive. In this work, the general theory is developed for the case where the configuration is not prescribed at the end times of the variational principle. This leads to a single governing equation of motion. This limitation can be removed by prescribing the end times, as is usual. This is outlined in the present paper, and will be the subject of a future paper.
Robust Tracking Control of a Shape Memory Alloy Wire Actuator
Authors: Song Gangbing , Quinn Dane
Published: November 2021

Tracking control of shape memory alloy (SMA) actuators is essential in many applications such as vibration isolation. Due to the hysteresis, an inherent nonlinear phenomenon associated with SMAs, control design based on linear methods has proven inadequate for tracking control of these actuators. In this paper, a novel tracking controller employing a nonlinear robust compensator is proposed for SMA actuators. The control design uses the sliding-mode approach and requires no detailed information of the SMA model. To test the effectiveness of the proposed controller, a single SMA wire test stand is built. A titanium-nickel SMA wire stretched by a bias spring is used as an actuator for tracking control. Experimental results show that the SMA wire actuator under the robust control can precisely follow a sinusoidal path and the effectiveness of the proposed control strategy is demonstrated.
Adaptive Vibration Control of Machining via PZT Actuator
Authors: Zamora Solórzano Efraín , Galíndez José A. Sánchez , Boya Eduardo Sasía , Irigoien Joseba Albizuri , Rodrigues María H. Fernandes
Published: November 2021

At present, the techniques developed to control machine tool vibration have been dominated by passive features, focusing on manipulating the cutting parameters such as feed rate, cutting speed, and depth of cut. Since productivity is affected when modifying cutting parameters, other control methods must be investigated. To that end, electroactive actuators and robust control algorithms have attributes that make them potentially effective in reducing the vibration level. In this paper, the successful use of an adaptive control with a piezoelectric actuator to decrease the vibrations in a machine tool is reported.
Disordered Dynamic Systems Resulting From Approximate Modeling and Analysis
Authors: Bhat R. B. , Stiharu I.
Published: November 2021

Some dynamic systems exhibit curve veering behavior or avoided crossings when their natural frequencies are plotted against a system parameter, while some other show a curve crossing behavior or frequency coalescence. The curve veering behavior is also observed in disordered systems where the symmetry of the system is slightly perturbed and a mode localization takes place. In some systems while the exact analysis shows a curve crossing trend, approximate analyses show a curve veering behavior. Earlier studies have shown that there is a common pattern in curve veering systems and disordered systems. In the present study the exact analysis is recognized as representing the actual system while the approximate analysis of the same system renders it a disordered system by perturbing the eigenvalues and eigenfunctions from their true values. Since the responses of disordered systems can sometimes show violent changes for small perturbations in the system parameters, the response of a simply supported plate has been obtained both exactly and approximately using the Rayleigh Ritz method, and compared. The conclusions have far reaching implications from the point of the accuracy of the response quantities obtained by approximate methods such as finite element method, the Rayleigh Ritz and Galerkin methods.
Preliminary Optical Performance Analysis of the Space Interferometer Mission Using an Integrated Modeling Methodology
Authors: Basdogan Ipek , Grogan Robert , Kissil Andy , Sigrist Norbert , Sievers Lisa
Published: November 2021

The Space Interferometer Mission (SIM) scheduled for launch in 2008, is one of the premiere missions in the Origins Program, NASA’s endeavor to understand the origins of the galaxies, of planetary systems around distant stars, and perhaps the origins of life itself. The precise tolerance required by the SIM instrument facilitates the investigation of many design options, trades, and methods for minimizing interaction between the actively controlled optics and the structure. One of the activities that addresses these technological challenges is the integrated modeling methodology development and validation at Jet Propulsion Laboratory (JPL). The methodology integrates structural, optical, and control system modeling into a common computational environment and enables end-to-end performance evaluation of complex optomechanical systems.

This paper provides an overview of the integrated modeling methodology and introduces the most recent SIM Reference Design model. The SIM integrated model is used in system requirement trade studies and performance analyses to support the overall system design and ongoing error budget efforts.

Optical performance in interferometry is typically measured in terms of optical pathlength difference (OPD) and differential wavefront tilt (DWT). This paper focuses on the OPD performance metric and investigates the OPD jitter resulting from reaction wheel assembly (RWA) disturbances. The RWA is the largest anticipated disturbance source on the spacecraft. Therefore, assessing the impact of the wheel disturbance frequency content and magnitude levels on the optical performance is essential for the success of the mission. Broadband and discrete frequency models of a reaction wheel are used to perform the disturbance analysis. The overall system design can benefit from such analysis results by identifying the critical regions in the frequency domain and decoupling the dynamics of the optical and structural components from the disturbance spectrum and the control bandwidth. The preliminary performance results show that the current SIM Reference Design meets the mission requirements with respect to RWA induced disturbances. However, some of the modeling assumptions and component models must be validated by experimental studies before the subsystem requirements are finalized.
Nonlinear Axial and Transverse Oscillation and Control of a PZT Laminated Distributed Structronic System
Authors: Tzou H. S. , Ding J. H. , Chai W. K.
Published: November 2021

Piezoelectric laminated distributed systems have broad applications in many new smart structures and structronic systems. As the shape control becomes an essential issue in practical applications, the nonlinear large deformation has to be considered, and thus, the geometrical nonlinearity has to be incorporated. Two electromechanical partial differential equations, one in the axial direction and the other in the transverse direction, are derived for the nonlinear PZT laminated beam model. The conventional approach is to neglect the axial oscillation and distributed sensing and control of the distributed laminated beam is evaluated, excluding the effect of axial oscillation. In this paper, influence of the axial displacement to the dynamics and distributed control effect is evaluated. Analysis results reveal that the axial displacement, indeed, has significant influence to the dynamic and distributed control responses of the nonlinear distributed PZT laminated beam structronics systems.
Modeling the Progressive Nature of Milling Tool Wear
Authors: Fish Randall K. , Ostendorf Mari , Bernard Gary D. , Castanon David , Shivakumar Hariharan
Published: November 2021

A particularly important step during industrial machining operations is the detection and classification of tool wear. Past research in this area has demonstrated the effectiveness of various feature sets and binary classifiers. The goal of the research discussed here is to develop a classifier which makes use of the dynamic characteristics of tool wear in a metal milling application and replaces the standard binary classification with a gradient measure that is the posterior probability (or confidence) that the tool is worn given the observed feature sequence. This classifier tracks the dynamics of sensor data within a single cutting pass as well as the evolution of wear from sharp to dull. We discuss topology design and training model parameters in an application with sparsely-labeled training data. We were able to achieve better than 90% accuracy across changing cutting conditions even with a limited feature set drawn from a single sensor.
End Milling Process Vibration Signal Enhancement by Stochastic Resonance
Authors: Klamecki Barney E.
Published: November 2021

The possible enhancement of vibration signals by the addition of a random signal component (stochastic resonance) was investigated. Vibration measurements during end milling were made using an accelerometer mounted on the workpiece. A large number of tests were run with varying spindle speed, table speed, axial depth of cut, radial depth of cut and tool condition. Signal frequency spectra were dominated by the cutting edge passing frequency and so individual cutting edge generated events could not be identified easily in the signal spectra. Enhancement of spectra peaks associated with individual cutting edge events by adding a random signal component to accelerometer signals was demonstrated in numerical experiments using actual accelerometer signals. The effects of initial spectrum peak magnitude, measurement system threshold level and added noise level on signal enhancement were determined.
Reactive Processing of CVD Diamond Substrates in Liquid Ambient by Second Harmonic of Nd:YAG Laser
Authors: Park Beom S. , Malshe Ajay P. , Brown William D. , Adhi Kiran P.
Published: November 2021

The objective of this investigation is to study the effects of laser radiation at 532 nm, the second harmonic of Q-switched Nd:YAG laser on polycrystalline diamond in air and liquid (water and H2O2) ambient. Phase changes and laser-induced stress due to structural deformations are analyzed using Raman spectroscopy. Surface morphology of the processed region of diamond and formation of microcracks is studied by scanning electron microscopy. Drilling of diamond substrates, in water ambient, is observed to be faster, 1.364 times, than that in the air. Enhancement in the drilling speed and uniformity of the drilled hole are discussed from the view of presence of reactive hydrogen and / or oxygen radicals liberated during the interaction of laser radiation with the diamond surface in water ambient.
Thermal and Dimensional Process Characteristics in Laser-Aided Rapid Manufacturing
Authors: Kahlen Franz-Josef , Kar Aravinda
Published: November 2021

Three-dimensional cylindrical and wall-like structures of copper, Ti-6Al-4V, aluminum, and stainless steel 304 were fabricated by melting the powders of these materials with a CO2 laser beam. A vapor-plasma plume is generated at the top of the melt layer. The emission spectra of the plume were recorded using an optical multichannel analyzer, and the plume temperatures are determined to be in the range of 4920 K to 6720 K. A one-dimensional model is developed to calculate the plume temperature, deposition geometry and melt pool characteristics. The model accounts for the transmission of the laser beam through the plume, energy transfer in the molten phase and the phase changes at the solid-liquid and liquid-vapor interfaces. The surface temperature at the molten surface is found to exceed the normal boiling temperature causing the pressure to be higher than one atmospheric pressure. The calculated plume temperatures are in good agreement with the values obtained from the spectral data. Also, the model predictions for remelt layer depth, deposition height and plasma height compare well with experimental data.
Vibration Analysis Based Modeling and Defect Recognition for Flip Chip Solder Joint Inspection
Authors: Liu Sheng , Erdahl Dathan , Ume I. Charles
Published: November 2021

A novel approach for flip chip solder joint quality inspection based on vibration analysis is presented. Traditional solder joint inspection methods have their limitations when applied to flip chip solder joint quality inspection. The vibration detection method is a new approach which has advantages such as being non-contact, non-destructive, fast and can be used on-line or during process development. In this technique, a flip chip was modeled as a thick plate supported by solder bumps. Changes in solder joint quality produce different vibration responses of flip chip, and change its natural vibration frequencies. In this paper, the vibration frequencies of a flip chip on a ceramic substrate were calculated using the finite element method. Based on vibration analysis, a laser ultrasound and interferometric system was developed for flip chip solder joint quality inspection. In this system, chips with good solder joints can be distinguished from chips with bad joints using their vibration responses and frequencies. Defects recognition methods were developed and tested. Results indicate this approach offers great promise for solder bump inspection in flip chip, BGA and chip scale packages.
Parametric Studies of the Thermal Performance of a Tape Ball Grid Array (TBGA) Package
Authors: Tonapi Sandeep S. , Sathe Sanjeev B. , Srihari K. , Sammakia Bahgat B.
Published: November 2021

This paper deals with parametric studies to evaluate the thermal performance of a Tape Ball Grid Array (TBGA) package. A cover plate is attached to the back side of the chip to enhance heat transfer from the module. The package is attached to an organic carrier and placed in a vertical channel. A conjugate heat transfer model is used accounting for conduction in the package and the card and convection in the surrounding air. The effect of location of the TBGA on a card with 0, 1 and 2 power planes is evaluated for thermal performance. Five different locations of the TBGA on the card are investigated. Heat dissipation is studied for forced convection (2, 1, and 0.5m/s). No significant difference in chip junction temperatures for the different locations is observed. Temperature distribution along the card centerline and the module centerline are used to discuss the physical phenomenon that is occurring.
Optimization of Forging Dies by Means of Simulation
Authors: Biba Nikolai , Vlasov Alexey , Lishny Andrey , Stebounov Sergei
Published: November 2021

Due to relatively high cost of the tooling in closed die forging the increasing of tool life is vitally important. The dies can failure due to cracks caused by overloading, low cycle fatigue or abrasive wear. On the other hand, the die deflection can cause deterioration of the forged part shape. The paper presents the ways for increasing of tool life and product accuracy by means of implementation of simulation. It can be done by modification of die design that reduces stress concentration in fillets or by using assembly dies that have splits in critical areas in combination with shrink rings and inserts. Finite element simulation allows to analyze the effectiveness of different variants of die design and to select the most effective ones in terms of tooling cost. Simulation also generates profiled shape of the die that compensates elastic deformation of tooling set and provides precise geometrical accuracy of a forged part.
Recent Developments in Thixoforging
Authors: Baur Jens , Messmer Guenther
Published: November 2021

During the process of thixoforging, the forming process of the metallic material takes place between the solidus and liquidus temperatures. Between these temperatures, both solid and liquid phases coexist. In comparison with the thixoforming methods, the process of thixocasting corresponds with die casting, while thixoforging has similarities with die forging.
Superimposing Ultrasonic Waves on Tube and Wire Drawing
Authors: Siegert Klaus , Ulmer Jochen
Published: November 2021

The drawing forces during wire and tube drawing can be reduced by ultrasonically oscillating dies. A major problem of conventional wire and tube drawing is to introduce high forces into the forming area. Compared to conventional wire and tube drawing, the forming process limits can be extended by superimposing ultrasonic waves due to decreasing drawing forces. Different techniques can be used to exite the die. One possibility is the variation of the vibration mode. In tube and wire drawing, the dies are usually exited longitudinally. If the vibration direction is parallel to the drawing direction, the main influence will be on the friction between workpiece and die. The Institute for Metal Forming Technology of the University of Stuttgart, Germany started a project to investigate the effect of ultrasonic waves on the tribology and on the the formability of the workpiece. The objective of this investigation is to separate the ultrasonic effect on the surface from the volume effects. This paper shows, that the reduction of the sliding friction between a longitudinal oscillating die and the workpiece can be explained by the so called Sliding Friction Vector Effect (SFVE). A statistical evaluation of roughness-measurements makes it possible to show the effect of the ultrasonic vibration on the friction and gives an insight into the operation of the SFVE. The results are compared with wire and tube drawing experiments of copper and Ti-alloys. New tube- and wire-drawing experiments with longitudinally vibrating dies support the theoretical approach. The surface-quality of the manufactured workpieces can be improved and the productivity increases.
Comments on a New Anisotropic Yield Criterion
Authors: Banabic D. , Balan T. , Comsa S. D. , Mueller W. , Poehlandt K.
Published: November 2021

A new yield criterion, derived from the Hosford criterion, is investigated. The new yield criterion is compared to experimental data for steel and aluminum sheets, respectively. The yielding predictions of this criterion are also compared to those provided by the Hill’s family criteria. It appears that the new yield criterion can predict the yielding behavior better than the Hill’s family. In the range of definition of the Hill’93 criterion, it has a similar user-friendly (but homogeneous) mathematical form and identification procedure.
Cutting Fluid Mist Formation in Turning via Atomization: Part 1—Model Development
Authors: Yue Y. , Gunter K. L. , Michalek D. J. , Sutherland J. W.
Published: November 2021

Cutting fluid mist is becoming an increasing concern for manufacturers as additional information is obtained on the health risks that it poses. This two-part paper is focused on investigating cutting fluid mist formation via an atomization mechanism in a turning process. Models will be established to predict the fluid mist mean drop size as well as the drop size distribution. Predictive relationships will also be presented for the settling behavior of the fluid mist and the mass concentration. Part 1 of the paper is devoted to the development of the requisite models to describe the mist creation and settling phenomena. In Part 2 of the paper, the mist formation models will be validated through a series of experiments.
Laser-Assisted Surface Engineering of Silicon Nitride to Minimize the Surface Defects Generated During Grinding Operation: Part I
Authors: Chinnakaruppan Palaniappan , Malshe Ajay P. , Yedave Sharad N. , Park Beom Soo , Schimdt William F. , Gordon Matthew H. , Batzer Stephen A. , Brown William D.
Published: November 2021

Silicon Nitride (Si3N4), a structural ceramic, is being increasingly used for various applications such as bearings, rotors, valves, etc., due to its highly useful mechanical and physical properties. To achieve the desired close tolerance and better surface integrity for such applications, abrasive machining using diamond wheel grinding, is primarily used. Due to the extreme mechanical properties of the silicon nitride, sub-surface and surface defects like micro-cavities, micro-cracks, smeared areas and debris are formed on the ground surface of the component due to grinding. The final flexural strength of the components are jeopardized to a greater extent due these surface defects. In this research work, a novel process is developed and established to eliminate/minimize these surface defects. The process involves annealing of defects using continuous wave carbon-dioxide (CW CO2, λ = 10.6μm) laser radiation. The laser is applied as a radiation source to selectively soften and reflow the secondary non-Si3N4 phase material to fill/anneal the defects present in the surface and sub-surface. Experiments were performed at three different power densities and at a constant scanning speed in air ambient. Power densities and scanning speed were selected based on the output of the model. It is found during the investigation that the laser treatment reduces the surface roughness and increases the micro-hardness without any change in the surface stoichiometry. Also, the sub-surface and surface defects are minimized and the flexural strength, which is an important property for the related applications, is found to be increased after treatment. The detrimental influence of machining defects on the mechanical failure of the sample during the four-point bend testing was found to be significantly reduced.
Femtosecond Pulsed Laser-Induced Micromachining of Difficult-to-Machine Materials: Diamond a Case Study
Authors: Malshe A. P. , Ozkan A. M. , Railkar T. A. , Adhi K. P. , Brown W. D. , Molian P. A.
Published: November 2021

Meso and micro scale machining is an important and emerging area of research. Various non-traditional and novel tools are being explored for meso and micro machining of non-silicon materials. In this paper, we report etching, micro machining and related phenomena of commercially available single and polycrystalline diamond using a femtosecond pulsed excimer laser (λ = 248 nm, tp ∼ 380 fs). Surface modifications due to single pulse and multiple pulse irradiation of diamond samples, at different energy densities, have been analyzed using Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Etching rate of single crystal type IIA diamond by femtosecond pulsed excimer laser is also studied. Raman spectroscopy study of the single shot irradiation of diamond with a femto second laser shows the formation of a non-diamond disordered (sp2 bonded) phase on the surface. However, subsequent micro machining of this non-diamond disordered surface, by delivering several shots from the femtosecond laser, results in the removal of the non-diamond disordered layer and the restoration of the diamond surface. It is experimentally shown that the periodicity of the 2-dimensional corrugations written on diamond surface is shorter than the laser wavelength used. 3-dimensional writing on diamond globules during laser etching is also discussed. Further, micro machining of diamond tips is shown to be precise, and without mechanical and chemical damages. Femto second laser is demonstrated as a next-generation tool for mechanical and chemical damage free precision micro machining of the hardest material, diamond.