bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrohydrodynamic (EHD) Flow and Convective Boiling Augmentation in Single-Component Horizontal Annular Channels
Authors: Cotton James S. , Chang JenShih , Shoukri Mamdouh , Smith-Pollard Tracey
Published: November 2021

In order to explore the mechanics of EHD induced flow and heat transfer augmentation, an experimental study of the tube-side boiling heat transfer of refrigerant HFC-134a has been conducted in a single-pass, counter-flow heat exchanger. The electrode position was arranged concentric to the tube. Experiments are conducted for inlet qualities of 0% to 60%, mass fluxes from 100 kg/m2s to 500 kg/m2s, heat fluxes of 10 kW/m2 and 20 kW/m2, and applied voltage from 0 kV to 8 kV DC. The threshold of EHD effects were analysed by a proposed dimensional analysis which predicts that the EHD forces become significant when the Dielectric Electric Rayleigh number is of the same order of magnitude as the square of the liquid Reynolds number, Eℓε ≈ Re ℓ 2 . This criterion is supported by experimental evidence. Flow visualization experiments have shown that, when the proposed dimensionless criterion is satisfied, EHD body forces may have a strong influence on the liquid-phase and consequently the flow pattern within the channel. The various flow configurations clearly affect heat transfer and pressure loss and need to be considered in any attempt to identify the effects of an applied electric field.
Numerical Modeling of Heat Transfer and Water Shedding in Automotive Evaporator Louvered Fins
Authors: Wang DeMing , Zhang Chao
Published: November 2021

A mathematical model has been developed to simulate mass and heat transfer of humid air flows at the airside of automobile air conditioning evaporators. The phenomenon of water condensation and water shedding in louvered fins are modeled based on extension of the existing Eulerian two-fluid method which treats water and air as two continuous media. A species transport equation for the mass fraction of water vapor in humid air is solved. The condensation of water from the air mixture translates into a sink term for the vapor transport equation and an equal source in the continuity equation for the volume fraction of liquid water in the two-fluid system of equations. A critical element in modeling the condensate transport in louvered fins calls for a surface tension force sub-model, since the surface tension force is the primary resistance against water shedding and draining. A formulation is proposed to evaluate the surface tension force based on searching for the most probable liquid-air interface where sharp gradient of water volume fraction exists. Numerical aspect of the implementation is discussed. In order to validate the model and demonstrate the applicability of the present methodology, a six-louver two-dimensional test case is established. The relative influence of the stopping force on liquid distribution pattern and flow was illustrated. The simulation is then carried out on a full-scale 2-D louvered fin design for different operating conditions. This study has demonstrated the feasibility of modeling “wet” heat transfer and water shedding in evaporator fins with an Eulerian two-fluid based method.
Modeling Non-Equilibrium CO Oxidation in Combustion Systems
Authors: Adams Bradley R. , Cremer Marc A. , Wang Dave H.
Published: November 2021

Performance of industrial and utility combustion systems is becoming increasingly affected by limits on pollutant emissions such as NOx and CO. CO emissions impact design and operation of combustion systems, particularly when coupled with NOx reduction technologies that involve lower temperature operation or staged firing. Lower combustion temperatures or delayed mixing of fuel and air helps minimize NOx formation, but can increase CO concentrations and minimize CO oxidation rates. Reacting computational fluid dynamics (CFD) models have been shown to be useful in evaluating and optimizing performance of these new technologies and operating conditions. These CFD models have traditionally used equilibrium chemistry models to predict specie concentrations throughout the combustor, however equilibrium assumptions for CO oxidation at lower temperatures is inaccurate. A non-equilibrium CO model is required to accurately predict the oxidation of CO at temperatures lower than ∼1150 K. This paper reviews the development of a non-equilibrium CO model and integration with a reacting CFD model. The use of the resulting model is illustrated on two combustion systems — a waste gas incinerator and a cyclone-fired utility boiler. Results show that low temperature CO oxidation can be accurately predicted with the use of the non-equilibrium CO model.
Experimental and Numerical Investigation of Air-Particle Two-Phase Flow in Centrifugal Separator
Authors: Kang H. J. , Zheng B. , Lin C. X. , Ebadian M. A.
Published: November 2021

The velocity distributions inside a centrifugal separator with outside and inside diameters of 152.4 mm (6″) and 76.2 mm (3″), respectively, have been investigated experimentally and numerically to obtain optimum separation efficiency. Two 12.7 mm (1/2-inch) holes were drilled on the external surface of the separator to measure the velocity distribution in the separator. Two direction velocities (tangential direction along the cylinder surface and axial along the vertical direction) were measured to compare with the numerical simulation results. A 6060P Pitot probe was employed to obtain the velocity distribution. The dust samples (a mixture of steel particle and dust) from the dust collection box were analyzed using a Phillips XL30 Scanning Electron Microscope.

FLUENT code is used as the numerical solver for this fully three-dimensional problem. The fluid flow in the separator is assumed to be steady and incompressible turbulent flow. The standard k–ε model was employed in this study. Non-uniform, unstructured grids are chosen to discretize the entire computation domain. Almost 100,000 cells are used to discretize the whole separator. The constant velocity profile is imposed on the inlet plane. The pressure boundary condition is adopted at outlet plane. Comparing the velocity distribution and separation efficiency from the experiment and the numerical modeling shows that the experimental results and the estimated data agree fairly well and with a deviation within ±10%.
Composite Isogrid Structures With Integral Passive Damping
Authors: Chen Yu , Gibson Ronald F.
Published: November 2021

This paper presents preliminary results from an analysis of the damping properties of a composite isogrid panel with an embedded viscoelastic layer by means of a finite element method (FEM) implementation of the modal strain energy method (MSE). Modal analysis shows that significant shear deformation occurs in the region between the ribs and the face skin because of the stiffness mismatch between the two. Since the performance of a viscoelastic polymer damping material is optimized by subjecting the material to shear deformation, such damping materials can be placed at the interface between the ribs and the skin in order to significantly improve the damping properties of composite isogrid structures. It is shown that the shear strain energy density (energy per volume) near the edges of the panel in the damping layer is much higher than that at the center area for the first free-free vibration mode. As a first attempt at improvement of damping, the effect of using different amounts of damping materials on the loss factor of the isogrid panel is also studied.
Decisive Factors in Advanced Centrifugal Compressor Design and Development
Authors: Japikse David
Published: November 2021

The design of advanced turbomachinery has been practiced in the last half of the previous century with increasing degrees of sophistication while continuously advancing levels of efficiency and regimes of stable operation. This trend of development is not complete; products have not reached a level of full maturity. There is considerable room for further development of most turbomachinery products today when looked at with the perspective of the broadest possible design world. Modern design no longer concerns itself only with efficiency and stability, but adds significant issues of weight, life, cost of manufacturing, marketability, and so forth. Decisive factors in each area are considered in this paper and consideration is given to developing trends.
Stress-Induced Martensitic Phase Transformations in NiTi Shape Memory Alloys During Dynamic Loading
Authors: Miller David A. , Thissell W. Richards , Gray George T. , Macdougall Duncan A. S.
Published: November 2021

This research explores the near-adiabatic, high strain rate stress-induced martensitic phase transformation in NiTi shape memory alloys using both a compressive and tensile Split Hopkinson Pressure Bar (SHPB). The results of the dynamic loading tests are presented with emphasis on the loading rate, stress-strain response, specimen temperature and post-test microstructural evaluation. In addition to the large strain rates, tensile specimens of various geometries are tested to large strain levels such that void growth and failure mechanisms are identified. The dynamically loaded specimens failed in a mixed mode, ductile void growth followed by transgranular failure. The void growth in incipient failure specimens showed ductile void growth throughout the specimen cross-section.
A Basis Function Method for Controlling Payload Vibration Using Command Shaping Control of a Multiple Axis Robot Maneuver
Authors: Agostini Michael J. , Parker Gordon G.
Published: November 2021

Several manufacturing assembly operations exist which require the robotic repositioning of flexible payloads. One example is aligning body panels during automobile assembly. These operations can limit throughput due to the need for relatively slow trajectories that don’t excite payload vibration. Several methods exist for generating residual vibration-free trajectories for single axis maneuver of flexible payloads, but there currently is not a general method for multiple axis maneuvers with nonlinear combinations of the inputs driving system vibration. In this paper a trajectory generation method is developed minimizing the energy transferred to the payload at resonant frequencies. Simulation and experimental results are presented demonstrating the approach.
Deployment Behavior of Modularized Structures
Authors: Ishimura Kosei , Natori M. C.
Published: November 2021

Deployment behavior of modularized structures is numerically analyzed from the viewpoint of synchronism. Elastic panels with single and double accordion folding patterns are examined as examples of modularized structures. Through computer simulations, it is shown that asynchronous deployments are caused by inertia forces. To improve the synchronism of the deployment, autonomous distributed control method is proposed. Control rules are driven based on equations of heat conduction and wave propagation. It is confirmed that simple autonomous distributed control can improve the synchronism of the deployment.
Vibration and Stability Control of Spinning Flexible Shaft via Integration of Smart Materials Technology
Authors: Song Ohseop , Librescu Liviu , Jeong Nam-Heui
Published: November 2021

Within this paper problems related with the vibration and stability control of circular flexible shafts spinning about their rotational axis are addressed. Due to the occurrence, as a result of the spinning speed, of gyroscopic forces in the system, the rotating shaft can experience, in some conditions, instabilities of the same nature as any nonconservative system, namely divergence and flutter instabilities. Whereas the former instability is of a static character, the latter one is of dynamic character and the results of its occurrence are catastrophic.

By including collocated sending and actuating capabilities via integration in the system of piezoelectric devices and of a feedback control law, it is shown that a dramatic enhancement of both the free dynamic response and of the stability behavior from both the divergence and flutter points of view can be achieved.

This implies that via the implementation of this technology an increase of the spinning speed can be achieved without the occurrence of these instabilities. Numerical simulations documenting these findings are provided and pertinent conclusions are outlined. It is also worthy to mention that the shaft is modeled as a thin-walled cylinder made of an anisotropic material and incorporating a number of non-classical features.
Effect of Regenerative Process on the Sample Stability of a Multiple Delay Differential Equation
Authors: Fofana M. S.
Published: November 2021

In this paper, explicit analytical expressions for the stability behaviour of a single degree of freedom turning model have been derived. The regenerative chatter due to chip thickness and feed rate variations, a delay in the spring stiffness coefficient and the probabilistic property of the displacement process of the chatter induced by the earlier tool cuts in the undeformed chip thickness have been taken into account. A characteristic equation for the linearized stability at equilibrium machining is presented, and regions of stable and unstable machining for multiple fixed time delays are captured in the parameter plane of two model parameters. By a combined use of the classical Hopf bifurcation theorem and the centre manifold, equations governing stochastic chattering, which are infinite in character, are reduced to two-dimensional ordinary differential equations. The integral averaging method and the Lyapunov exponent have been employed to explicitly derive the required analytical expressions.
Nonlinear Modeling and Experimental Verification of a MDOF Hydraulic Engine Mount
Authors: Geisberger Aaron A. , Khajepour Amir , Golnaraghi M. Farid
Published: November 2021

This paper has made several contributions to hydraulic mount modeling. A continuous nonlinear decoupler model is developed to capture the amplitude dependent behavior of a typical hydraulic mount over low and high frequency ranges. The decoupler model also demonstrates decoupler resonance, which degrades high frequency characteristics of a generic hydraulic mount. In addition, this paper is the first to introduce a lumped parameter MDOF (Multi Degree Of Freedom) fluid column system that is shown to improve high frequency characteristics. Model parameters are identified by isolating components in an experimental test apparatus and applying system identification techniques. Model simulation results are validated with measured data over the full range of standard excitation conditions.
On Adaptive-Passive Vibration Suppression Using Distributed-Parameter Absorbers
Authors: Jalili Nader
Published: November 2021

A semi-active vibration absorber with adaptive capability is presented to improve wide band vibration suppression characteristics of harmonically excited structures. The absorber subsection consists of a double-ended cantilever beam carrying an intermediate lumped mass. The adaptive capability is achieved through concurrent adjustment of the position of the moving mass, along the beam, to comply with the desired optimal performance. If such an absorber is attached to a vibrating body, it effectively absorbs vibrations at all frequencies that belong to the absorber frequency bandwidth. Numerical simulations are provided to verify the effectiveness of the proposed absorption scheme. It is shown that the tuning strategy tries to follow and match the absorber natural frequency with the excitation frequency. The optimally tuned absorber provides considerable vibration suppression improvement over the passive and de-tuned absorbers, for wide band excitation disturbances.
Search-Based Selection of Sample Points for Form Error Estimation
Authors: Badar M. Affan , Raman Shivakumar , Pulat P. Simin
Published: November 2021

Efficient part feature verification through coordinate metrology requires prudent sample point selection as well as accurate zone fitting. Selection of a large sample size typically results in higher accuracy of sampling. This paper suggests search-based methods for reducing the sample size in form verification while maintaining required accuracy. Specifically, we illustrate the use of region elimination search methods for straightness verification and the tabu search technique for flatness. The corresponding form error is then obtained using the least squares and/or the minimum zone methods. Preliminary example analysis is presented to demonstrate the methodology.
Thermal Evaluation of GaAs-Based RF Power Amplifier Packages for Handheld Portable Applications
Authors: Adams V. H. , Lee T. Y. Tom , Hause J. V.
Published: November 2021

This study characterizes the thermal performance of the Thermally Enhanced Plastic Very Thin Fine Pitch Quad Flat No Lead Package (HP-VFQFP-N) family for GaAs-based RF power amplifier applications. This package uses perimeter lands on the bottom of the package to provide electrical contact to the printed wiring board (PWB). The package also provides thermal enhancement by having the die attach paddle exposed on the bottom of the package surface to provide an efficient conduction path when soldered directly to the printed wiring board. Thermal model assumptions and development for the 0.5 mm pitch HP-VFQFP-N package are provided. Due to the relatively low thermal conductivity of GaAs, power dissipation in the individual stage areas on the die were modeled instead of uniform surface heat flux or uniform heat generation rate approximations. A conjugate heat transfer problem, in which radiative losses from the exposed surfaces of the package and PWB to the external environment were accounted for, was solved for horizontal natural convection cooling. The model is benchmarked with infrared thermal imaging measurements obtained for a 20 I/O, 0.5 mm pitch, 4 mm HP-VFQFP-N package with a 2-Stage GaAs Power Amplifier (PA) integrated circuit (IC). Predictions for junction-to-ambient thermal resistance were within 10% of measured values.

Parametric studies were performed for HP-VFQFP-N sizes of 4, 5, and 6 mm with GaAs die sizes from 1.465 × 1.369 mm to 2.7 × 2.354. IC layout considerations and associated power distribution on the die were also examined. 2-Stage PA, 3-Stage PA, and 3-Stage Dual-Band PA IC configurations were examined. Some improvement in thermal performance was noted with increasing package size (for the same IC configuration/die size). GaAs die size had minimal impact on thermal performance of the QFN package but the IC layout/power distribution significantly impacted product/package thermal performance. Additional studies were performed to evaluate mold compound and die attach thermal conductivity effects on package thermal performance.
An Analytical Design Method for Milling Cutters With Non-Constant Pitch to Increase Stability
Authors: Budak Erhan
Published: November 2021

Chatter vibrations result in reduced productivity, poor surface finish and decreased cutting tool life. Milling cutters with non-constant pitch angles can be very effective in improving the stability of the process against chatter. In this paper, an analytical stability model and a design method are presented for non-constant pitch cutters. An explicit relation is obtained between the stability limit and the pitch variation which leads to a simple equation for optimal pitch angles. A certain pitch variation is effective for limited frequency and speed ranges which are also predicted by the model. The improved stability, productivity and surface finish are demonstrated by several examples.
On Modeling the Rolling Contact Fatigue Performance Based on Residual Stresses Generated by Superfinish Hard Turning
Authors: Agha Salah R. , Liu C. Richard
Published: November 2021

It was shown earlier [Agha and Liu, 1998, 1999, 2000] that different cutting conditions, within superfinish hard turning, would lead to significantly different rolling contact fatigue lives. In this study, residual stresses were measured. The rolling contact fatigue life was then modeled using a maximum modified equivalent stress that takes residual stresses into account. It is seen that the maximum modified equivalent stress is a better predictor than the maximum Hertzian stress, but, still not accurate, given the consistent repeatability of the tested workpieces [Agha and Liu, 2000]. The difference in the nature of residual stresses produced by grinding and hard turning is used to show why the inclusion of the maximum modified equivalent stress, its location and the volume at risk, improves the power of the model to predict the rolling contact fatigue lives of the hard turned surfaces. This model is the best up to date for predicting the fatigue life of a surface, especially when residual stress is a factor.
Changes in the Mechano-Electrochemical Environment in the Extracellular Matrix Surrounding Chondrocytes
Authors: Mow V. C. , Guo X. E. , Sun D. D. , Lai W. M.
Published: November 2021

The objective of this paper is to provide an overall discussion of the biomechanical factors that are required to analyze and interpret data from the explant experiments and to present a description of some of the mechano-electrochemical events in the extracellular matrix (ECM) surrounding chondrocytes occurring within cartilage explants during loading. Five common loading cases of cartilage explants are discussed: hydrostatic pressure, osmotic pressure, permeation, confined compression and unconfined compression. Details of such surface loadings on the internal ECM pressure, fluid and ion flows, deformation and electrical fields are given. Similarities and differences in these quantities due to these five types of loadings are specifically noted. For example, it is noted that there is no practical mechanical loading condition that can be achieved in the laboratory to produce effects that are equal to the effects of osmotic pressure loading within the ECM. Some counter-intuitive effects from these loadings are also described. Further, the significance of flow induced compression of the ECM is emphasized, since this frictional drag effect is likely to be one of the major effects of fluid flow through the porous-permeable ECM. Associated streaming potential and diffusion potential and their dependence on the fixed charge density, are discussed in relation to the fluid flow through the charged ECM and the flow-induced compaction effect. Understanding of the differences among these explant loading cases is important; this can provide clearer understanding of the metabolic responses from chondrocytes in explant loading experiments.
Loading Rate Effect on Translaminar Fracture Toughness of Hybrid Composite Laminate
Authors: Moy Paul , Tzeng Jerome
Published: November 2021

Fracture toughness properties of composite laminates were evaluated at a loading rate commonly observed in ordinance applications. The laminates are composed of IM7 graphite and a small volume fraction of S2 glass plies to form a cross-ply laminate. Fracture toughness appears to be very rate sensitive if the crack growth perpendicular to the plane dominated by glass/matrix property. Experimental data shows a 30–40% increase of fracture toughness for various layup as the loading rate was increase by 1000 times. The specimens examined under microscopic indicates the strengthening might due to different failure mechanism in the matrix. In addition, there is no visible rate effect if the crack propagation is perpendicular to the graphite dominant plane.
Modeling and Simulation of Pressure Oscillations in a Gas Pressure Regulator
Authors: Delenne Bruno , Mode Laurent
Published: November 2021

Pressure stability on gas networks is a major concern for designers and operators of Gaz de France transmission and distribution networks. Pressure level is controlled by pressure regulators. To improve the process control and optimise the design of pressure regulating stations (PRS), experimental and numerical studies have been carried out by the Research and Development Division.

The purpose of this paper is to provide an analytical model for pilot controlled gas pressure regulators and to determine the operating conditions that avoiding oscillating pressure regime. Frequency and amplitude of the oscillations depend on many parameters such as flow rate, inlet and outlet pressure mean levels, the downstream volume size, the length of the sensing line or diameter of the outlet pipe.

Particular attention is required to represent pressure loss and flow dynamics in pipes and process lines. The model has been developed under the ALLAN.® Simulation environment, a general software for the description and simulation of dynamic systems.

It turned out from simulations and measurements that the upstream pressure and the volume of the downstream buffer are very sensitive parameters that influence amplitude and frequency. From a qualitative point of view, numerical and experimental results are in good agreement.
A Semi-Analytical Solution for Responses of the Surface of an Elastic Half-Space Subjected to Vertical, Harmonic, Concentrated Forces
Authors: Hamidzadeh Hamid R. , Luo Albert C. J.
Published: November 2021

The dynamic response of a soil medium surface subjected to a vertical, harmonic, concentrated force is investigated. The half-space soil medium is considered to be elastic, isotropic and homogeneous. The expression of surface displacement is given analytically through a double Fourier transformation, integrals and Rayleigh functions. For numerical results of the surface response, the Modified Gaussian quadrature method is used. The in-phase and quadrature components of the displacements for any position on the surface of the unloaded half-space are illustrated for the Poisson’s ratio of 0.25 as a sample problem.
Experimental and Theoretical Analysis of a Power Transmission Belt
Authors: Pellicano Francesco , Vestroni Fabrizio , Fregolent Annalisa
Published: November 2021

In this paper, the effect of a pulley eccentricity on the vibration of a power transmission belt is experimentally investigated and a theoretical model is developed for validation and identification purposes. This eccentricity gives rise dangerous operating conditions for the system, especially when it excites the frequency range of the belt resonances. As expected, the system shows a hardening nonlinear behavior. Moreover, the fluctuation of the belt tension, due to the pulley eccentricity, gives rise to a parametric instability that can undergo to catastrophic failures of the structure. Experimental observations with quantitative measurements are obtained by means of a laser telemeter. Frequency response curves are drawn when the beam is harmonically excited close to the first and second linear natural frequency. A simple analytical approximation of the system response is obtained by one complex mode approximation. An asymptotic solution justifies the experimental evidence and allows the identification of the main parameters of the equation of motion. The excellent agreement between theoretical and experimental data confirms the consistency of the analytical model and the identification of the parameters.
High-Speed Passenger and Intercity Train Aerodynamic Computer Modeling
Authors: Holmes Samuel , Schroeder Martin , Toma Elton
Published: November 2021

With the onset of high-speed passenger train service in the United States, the Federal Railroad Administration (FRA) and railroad agencies are concerned with the aerodynamic effects these trains will have on lightweight freight equipment, such as empty double stack container cars. This paper presents the results of a research project that evaluated this interaction. In this study we conducted a series of computational fluid dynamic (CDF) calculations to characterize the aerodynamic loads on a container consist passed by a high-speed train. A train motion simulation program was used to determine resultant motion and risk of overturning or derailment of the container consist. Numerous cases were studied in which train speed and wind speed and direction were varied.
Identification and Prediction of Frame Structure Dynamics by Spatial Matrix Identification Method
Authors: Okuma Masaaki , Heylen Ward , Matsuoka Hisayoshi , Sas Paul
Published: November 2021

This paper presents the result of using an experimental spatial matrix identification method to predict the dynamics of a frame structure under a different boundary condition. The single-input-multiple-output frequency response functions of the test structure under the free-free boundary condition are measured by hammer testing. Using the FRFs, a set of spatial matrices is determined to represent its structural dynamic characteristics by the method. Then, using the identified spatial matrices, the dynamic characteristics of the test structure under the boundary condition of clamping 4 points is predicted. The prediction is practically accurate. The result of the prediction demonstrates that the spatial matrices identified by the method can be used for structural modification and substructure synthesis in the field of computer aided mechanical engineering.
A Determination of Biophysical Parameters Related to Freezing of an ELT-3 Cell Line
Authors: Berrada Marwane S. , Bischof John C.
Published: November 2021

This study investigates two destructive biophysical mechanisms during freezing (extensive dehydration and intracellular ice formation) at the cellular level in the rodent ELT-3 uterine fibroid cell-line. The osmotically inactive volume fraction (Vb) of ELT-3 cells was approximated to 0.35 of the initial isotonic cell volume (Vo). The water transport characteristics of this cell-line are such that ELT-3 cells are highly permeable with a strong ability to lose water even at low subzero temperatures. The hydraulic reference permeability, Lpg and activation energy, Elp associated with Lp were found to be 0.13 (μm/min.atm) and 19.0 (kcal/mole) [R2 = 0.86] respectively. Intracellular Ice Formation (IIF) occurs at lower temperatures than many cell-types (i.e. TIIF 50% below −15°C) at cooling rates > 25 °C/min. Darkening IIF, which was assumed to occur by Surface Catalyzed Nucleation (SCN), is governed by kinetic Ωo and thermodynamic κo biophysical parameters, which were found to be 6.1×108(m2.s)−1 and 5.3×109(K5) [R2 = 0.94] respectively. At a cooling rate of 100°C/min, twitching IIF (non-darkening IIF) was observed. Viability data from a separate study (Bischof et. al., 2000) indicated that at cooling rates ≤ 1°C/min and ≥ 50°C/min with an end-temperature of −20°C, extensive damage to cells was observed. The current biophysical study shows that extensive dehydration occurs at 1°C/min while substantial IIF (77%) occurs at 50 °C/min. This data suggests that while biophysics can explain some of the destruction occurring at the investigated temperatures, other effects or mechanisms may be playing a role at lower end-temperatures.
H∞ Optimization of Fixed Structure Controllers
Authors: Ibaraki Soichi , Tomizuka Masayoshi
Published: November 2021

In this paper, the H∞ optimization problem of fixed structure linear controllers is considered. Applications of the problem include tuning of SISO (Single-Input Single-Output) PID (Proportional plus Integral plus Derivative) controller gains. The proposed algorithm starts with transformation of the original problems into a static output feedback controller synthesis problem, which does not impose any constraints on the controller structure except for its order. Unlike the full-order H∞ controller synthesis case, the H∞ optimization problem of static output feedback controllers cannot be reparameterized as a convex optimization problem. The cone complementarity linearization algorithm is used to overcome the nonconvexity problem due to the constraint on the controller order. The proposed algorithm is applied to the design of a SISO PID controller for head positioning of a magnetic hard disk drive.
Modeling and Coordinated Control of an Earthmoving Vehicle Powertrain
Authors: Prasetiawan Eko , Zhang Rong , Alleyne Andrew
Published: November 2021

An earthmoving vehicle powertrain is modeled as a MIMO hydrostatic system. Its control inputs include the engine throttle, an electro-hydraulic pump displacement and flow valve commands. These inputs offer a great control freedom but need to be coordinated. As a starting point for the ultimate MIMO control, a coordinated MISO controller for one of the load nodes is designed by using an LQG technique. Modeling and control design are accomplished and validated by both first principles and experimental data. The experimental data are obtained upon an Earthmoving Vehicle Power-train Simulator (EVPS) at the University of Illinois. The paper details the utilization of this “hardware-in-the-loop” testbed in investigating generic power-optimization problems for hydrostatic transmissions. Simulation results as well as experimental data are presented.
Lapping Control of Hard Disk Drive Heads: Part II—Control
Authors: Mei Youping , Stelson Kim A.
Published: November 2021

Using numerical modeling as a tool, the pressure dynamics of bar lapping is identified. The process model is constructed based on the pressure dynamics and the Preston model. A controller is then designed using a trajectory following formulation. Simulation of the controller designed as such shows that it is robust to parameter uncertainties. This controller is implemented on a Seagate lapping system. Experiment results show that the proposed method is less sensitive to the quality of the preparation processes. However, the gains should be appropriately adjusted for optimal performance. With good preparation processes and appropriate gains, performance of the two methods are statistically comparable. Otherwise, the proposed method performs better. The proposed method is inferior to the existing method only when its gains are improperly adjusted.
Integration of Geometric and Mechanistic Models of NC Machining Into an Open-Architecture Machine Tool Controller
Authors: Jerard Robert B. , Fussell Barry K. , Ercan Mustafa T. , Hemmett Jeffrey G.
Published: November 2021

A great deal of research has been done during the last twenty years on the modeling and control of NC machining. Despite the promise of substantial productivity improvements these methods are sparsely used outside their academic birthplaces. We believe that Open-Architecture Controllers (OAC) are the key to unlocking this unfulfilled potential. We describe the implementation of novel methods for feedrate optimization which utilize a commercially available OAC. In this paper an example is given of how substantial improvements in machining processes can be achieved by implementing geometric and mechanistic models of the cutting process on an OAC. These benefits should provide motivation for a more universal adoption of OACs.
Real-Time Detection of Wheel and Work-Piece Contact/Release in Reciprocating Surface Grinding
Authors: Razavi H. Ali , Kurfess Thomas R.
Published: November 2021

In this paper a signal-processing algorithm to detect wheel and work-piece contact/release is introduced. Simulation is used to demonstrate the approach followed by a series of experiments for real-time validation. Although, the method is implemented on a special application, there exists potential for other applications.
An Energy-Enhanced Design of Experiments Method
Authors: Christensen Bjorn G. , Ferris John B. , Stein Jeffrey L.
Published: November 2021

Computer models of complex mechanical systems are being used more frequently and effectively due to ever increasing computing power. These models have improved the design process by allowing designers to create virtual prototypes of systems. Computer models permit iterative designs, thereby allowing the designer to run hundreds of simulations in the time it would take to make one physical model and test it. This ease of iteration has made design of experiments (DOE) analyses easy to carry out on the computer models. A DOE analysis provides excellent information regarding the specific output function being examined, but may overlook some of the global effects that these changes may have on the system. A new design tool is developed in this work that addresses this deficiency. The new method greatly improves upon existing design tools such as DOE. Specifically, the new method augments a traditional DOE study with an Activity study, which focuses on the energy flow in the system and provides a larger picture of the system dynamics. Instead of using only a DOE analysis to determine which elements’ properties should be changed, the Activity of the elements is also considered. This helps prevent altering a parameter or set of parameters to achieve a desired response at the expense of other unforeseen results. This idea is demonstrated by investigating the issue of designing a vehicle for improved ride quality. A simple quarter car model is used so that the results can be clearly seen. The example shows that design changes based on a DOE analysis alone can improve the ride quality, but also can alter other system responses significantly. When an Activity analysis is combined with the DOE study, the ride quality is improved, but the effects on other aspects of the system are greatly reduced. Augmentation of DOE with Activity allows a specific design goal to be achieved and also provides global information about the system. This allows the engineer to make informed decisions about the effects of changes on the system.
The Development of a Split-Tube Flexure
Authors: Goldfarb Michael , Speich John E.
Published: November 2021

This paper describes the design of a flexure joint, called the split-tube flexure, which can provide a considerably larger range of motion and significantly better multi-axis revolute joint characteristics than a conventional beam-type flexure. Specifically, the flexure joint contrasts the torsional compliance of a thin-walled open-section member with its bending rigidity to produce kinematically well-behaved revolute motion. The joint proves particularly useful in applications requiring kinematically well-behaved large motions, such as in robot manipulators.
Robust Dynamic Locomotion Through Feedforward-Preflex Interaction
Authors: Cham Jorge G. , Bailey Sean A. , Cutkosky Mark R.
Published: November 2021

Unlike most legged robotic systems built to date, even simple animals have the ability to quickly and robustly traverse through rough terrain and over large obstacles and gaps. Recent evidence from insect physiology research indicates that arthropods achieve this fast robust locomotion largely without relying on sensory feedback or reflex response. Instead, locomotion is the result of the interaction between a basic feedforward motor pattern and the visco-elastic properties of the mechanical system, termed “preflexes.” In this paper, we consider the implications of this control hypothesis for the design of small running robots for uncertain environments. We present working prototypes that show how robust dynamic locomotion can be achieved without the use of sensory feedback. We then discuss modeling approaches for these kinds of systems and present results from simulations of representative models.
A High-Bandwidth Force-Controlled Haptic Interface
Authors: Lee Christopher D. , Lawrence Dale A. , Pao Lucy Y.
Published: November 2021

The design and control of a 5 degree-of-freedom (DOF) haptic interface that provides accurate rendering of forces as well as a large range of motion is presented. We review a number of design approaches that have been considered in other haptic interfaces and the reasons for choosing a parallel mechanism for our design. The choice and motivation for the actuators, sensors, and materials used are also discussed. High bandwidth transmission of forces is achieved through a force control loop in each degree of freedom. Details of the single actuator control design process and the robustness of the controllers are also overviewed. The resulting interface is able to provide a workspace of about 40 cm in translation in 3 DOF and about ±60 degrees in 2 DOF of angular motion, and the force controllers have closed-loop bandwidths of about 175 Hz.
Nonlinear Crack Growth Monitoring
Authors: Welch Donald E. , Hively Lee M. , Holdaway Ray F.
Published: November 2021

Structures subject to crack growth spend 90–95% of their lifetime in nucleation of very tiny flaws into measurable crack sizes. Due to the large variation in initial flaw sizes and the mathematics of flaw growth, the fatigue lifetimes, even of high-quality structures, can vary by a factor of as much as 10 to 20 even in a small fleet. This large variation in fatigue lifetimes leads to conservative statistics, which often prompts the premature retirement or overhaul of structures, since they focus on the weakest members of the fleet, while the remainder of the fleet is sound.

In the past two years, Oak Ridge National Laboratory (ORNL) has developed a new Griffith energy-based technique that can provide useful warning of the impending failure of a structure due to end-of-life crack propagation. This technique has been demonstrated by test and analysis in fiberglass composite for tension-tension fatigue.
High Speed Crash Barrier Investigation Using Simulation
Authors: Reid John D. , Faller Ronald K. , Sicking Dean L.
Published: November 2021

Auto racing has become one of the most popular sporting venues in the United States. For these events, vehicles typically travel around oval tracks at extremely high speeds, in some cases in excess of 365 km/h. At these higher speeds, these vehicles may be involved in multi-car collisions or impacts with the exterior rigid walls, potentially resulting in serious driver injuries or fatalities. Although infrequent, serious harm has also occurred to spectators as flying vehicle debris has passed over protective fencing. As a result of these accidents, researchers at the Midwest Roadside Safety Facility, in cooperation with the Indy Racing League, Indianapolis Motor Speedway, and Kestrel Advisors, Inc., have been investigating and developing several energy-absorbing barrier concepts that would provide increased track safety. Two concepts — one using HDPE plates and one using crushable foam — are described herein. Preliminary results from the computer simulation effort show great potential for increasing the safety of race track barriers.
A Sub-System Test Methodology for Simulating EEVC Side Impact
Authors: Aekbote Krishnakanth , Sundararajan Srinivasan , Prater Joseph A. , Abramczyk Joe E.
Published: November 2021

A sled based test method for simulating full-scale EEVC (European) side impact crash test is described in this paper. Both the dummy (Eurosid-1) and vehicle structural responses were simulated, and validated with the full-scale crash tests. The effect of various structural configurations such as foam filled structures, material changes, rocker and b-pillar reinforcements, advanced door design concepts, on vehicle performance can be evaluated using this methodology at the early stages of design. In this approach, an actual EEVC honeycomb barrier and a vehicle body-in-white with doors were used. The under-hood components (engine, transmission, radiator, etc.), tires, and the front/rear suspensions were not included in the vehicle assembly, but they were replaced by lumped masses (by adding weight) in the front and rear of the vehicle, to maintain the overall vehicle weight. The vehicle was mounted on the sled by means of a supporting frame at the front/rear suspension attachments, and was allowed to translate in the impact direction only. At the start of the simulation, an instrumented Eurosid-1 dummy was seated inside the vehicle, while maintaining the same h-point location, chest angle, and door-to-dummy lateral distance, as in a full-scale crash test. The EEVC honeycomb barrier was mounted on another sled, and care was taken to ensure that weight, and the relative impact location to the vehicle, was maintained the same as in full-scale crash test. The Barrier impacted the stationary vehicle at an initial velocity of approx. 30 mph. The MDB and the vehicle were allowed to slide for about 20 inches from contact, before they were brought to rest. Accelerometers were mounted on the door inner sheet metal and b-pillar, rocker, seat cross-members, seats, and non-struck side rocker. The Barrier was instrumented with six load cells to monitor the impact force at different sections, and an accelerometer for deceleration measurement. The dummy, vehicle, and the Barrier responses showed good correlation when compared to full-scale crash tests. The test methodology was also used in assessing the performance/crashworthiness of various sub-system designs of the side structure (A-pillar, B-pillar, door, rocker, seat cross-members, etc.) of a passenger car. This paper concerns itself with the development and validation of the test methodology only, as the study of various side structure designs and evaluations are beyond the scope of this paper.
How Cell Shape Affects the Stresses in a Cell Sheet
Authors: Brodland G. W. , Veldhuis Jim H. , Chen Daniel I-Li
Published: November 2021

Computer simulations and analytical mechanics are used to investigate the mechanics of cell sheets. The simulations are based on a recent finite element formulation [1] in which each cell is modeled using multiple finite elements, and cells can rearrange. Sheet stresses calculated using an analytical expression based on average cell shape are found to agree well with those calculated in the finite element simulations. This is an important step towards the development of constitutive equations to describe real cell sheets.
Finite Element Model of the Human Knee Joint to Study Tibio-Femoral Contact Mechanics
Authors: Donahue Tammy Haut , Hull Maury L. , Rashid Mark M. , Jacobs Christopher R.
Published: November 2021

A finite element model of the tibio-femoral joint in the human knee was created using a new technique for developing accurate solid models of soft tissues (i.e. cartilage and menisci). The model was used to demonstrate that constraining rotational degrees of freedom other than flexion/extension when the joint is loaded in compression markedly affects the load distribution between the medial and lateral sides of the joint. The model also was used to validate the assumption that the bones can be treated as rigid.
Normal Cartilage Thickness and Osteoarthritic Wear Patterns of the Human CMC Joint
Authors: Koff Matthew F. , Cohen Zohara A. , Ugwonali Obinwanne F. C. , Balaguer Eric J. , Ateshian Gerard A. , Mow Van C.
Published: November 2021

Cartilage thickness maps of the trapezium and metacarpal of the human thumb carpometacarpal (CMC) joint were determined from 51 hands. Specimens were divided into 3 groups based on visual staging of the articular cartilage surfaces for osteoarthritis (OA), and average thickness maps were created for both surfaces within each group. Statistical analyses demonstrated that in advanced OA, cartilage on the trapezium thins on the volar and dorso-radial regions, while the metacarpal exhibits thinning on its volar aspect.
Towards Reliable Thermal Spray Coatings: An Integrated Approach
Authors: Sampath Sanjay
Published: November 2021

Thermal sprayed coatings are used extensively in engineering components for a variety of protective coating applications. Thermal spraying is a highly dynamic process resulting from rapid heating /accelerating of powder particles in a flame, followed by impact and rapid solidification of the droplets (splats). A splat resulting from the flattening of an individual droplet is the basic building block (unit cell) of the thermal sprayed microstructure. Phase and microstructure of the splats (intrinsic) and the integration of the splats (extrinsic) are both affected by processing condition and the properties of a plasma sprayed deposit are directly related to this complex anisotropic microstructure. These affect both performance and reliability of sprayed surfaces.