bluuebunny/crossref_metadata_2025 huggingface dataset:
Bending of a Layered Isotropic Plate With Periodic Debondings
Authors: Danicki E.
Published: April 2008

A layered, isotropic, and infinite elastic plate which has periodic cracks (debondings) between the layers is considered. The plate is subjected to a surface traction. The traction is spatially sinusoidal but is oriented arbitrarily. A solution for the particle displacement is obtained in form of a Fourier series expansion which accounts for the field singularities at the edges of the cracks. An average elastic property (homogenization) of the sample plate is discussed.
An Exact Solution of the Unsteady Navier-Stokes Equations Resulting From a Stretching Surface
Authors: Smith S. H.
Published: April 2008

When a stretching surface is moved quickly, for a short period of time, a pulse is transmitted to the surrounding fluid. Here we describe an exact solution in terms of a similarity variable for the Navier-Stokes equations which represents the effect of this pulse for two-dimensional flow. The unusual feature is that this solution is only valid for a limited range of the Reynolds number; outside this domain unbounded velocities result.
Exact Transient Full-Field Analysis of an Antiplane Subsurface Crack Subjected to Dynamic Impact Loading
Authors: Ma Chien-Ching , Chen Szu-Kuzi
Published: April 2008

The transient problem of a half-space containing a subsurface inclined semi-infinite crack subjected to dynamic antiplane loading on the boundary of the half-space has been investigated to gain insight into the phenomenon of the interaction of stress waves with material defects. The solutions are determined by superposition of the fundamental solution in the Laplace transform domain. The fundamental solution is the exponentially distributed traction on crack faces. The exact close-form transient solutions of stresses and displacement are obtained in this study. These solutions are valid for an infinitely long time and have accounted for the contributions of incident, reflected, and diffracted waves. Numerical results of the transient stresses are obtained and compared with the corresponding static values. The transient solution has been shown to approach the static value after the first few diffracted waves generated from the crack tip have passed the observation point.
Plausibility of Structural Constitutive Equations for Isotropic Soft Tissues in Finite Static Deformations
Authors: Lanir Y.
Published: April 2008

Soft tissues are binary systems of fibers embedded in a fluid matrix. Their equilibrium response to external loading is the sum of the fibers’ stress and the matrix osmotic pressure. The present study examines the conditions under which the elastic response of isotropic tissues, as modeled by structural constitutive equations, is physically plausible. The analysis shows that plausibility is ensured if the fibers’ stretch force increases monotonically with the stretch and if the matrix osmotic pressure increases convexly with the concentration. Published data shows that both conditions prevail in soft tissues. It is thus concluded that structural modeling is compatible with physically plausible response.
A Sufficient Stability Condition for Linear Conservative Gyroscopic Systems
Authors: Wu Jinn-Wen , Tsao Tsu-Chin
Published: April 2008

A sufficient stability condition for linear conservative gyroscopic systems with negative definite stiffness matrices is given. The condition for the stability is stated in terms of the coefficients of system matrices without solving the spectrum of the entire system. An example is given for comparison with existing results.
Stress Intensity Factors for Plate Bending and Shearing Problems
Authors: Zehnder A. T. , Hui Chung-Yuen
Published: April 2008

Stress intensity factors for a finite crack in an infinite plate are calculated assuming Kirchhoff plate theory. Two problems are considered: a cracked plate subjected to uniform far-field shearing, and a cracked plate subjected to uniform far-field bending moment. In both cases the crack is oriented at an arbitrary angle to the axis of loading.
Post-buckling Behavior of Beams Under Contact Constraints
Authors: Adan N. , Sheinman I. , Altus E.
Published: April 2008

An analytical model of the post-buckling behavior of a beam under contact constraints was derived. Experiments were carried out in order to characterize the various phenomenon involved in the problem. Two experiments with symmetric response with various contact surface and initial imperfection, and one experiment of asymmetric behavior were chosen for validation of the analytical results. The theory is based on a nonlinear kinematic approach and on the moving boundary procedure. The nonlinear equations are derived by the variational principle and solved through truncated approximating functions. A modification of an “arc-length” procedure was developed for solving the equation which incorporates the snapping effect. A comprehensive parametric study of the dominant parameters (distance between the beam and the contact surface, initial imperfections, contact location, magnitude of the contact forces, etc.) is carried out through numerical examples. Very good agreement with experimental results for the various phenomena involved in the problem was obtained for a clamped beam.
The Folding of Triangulated Cylinders, Part II: The Folding Process
Authors: Guest S. D. , Pellegrino S.
Published: April 2008

In the first paper of this series we have introduced a class of foldable triangulated cylinders. In this paper we consider three particular examples of these cylinders and analyse computationally the way they fold. We show that this process is nonuniform and that it consists of two phases. The first unsteady phase involves the gradual buildup of strain energy in a “shape transition region.” In the second phase the transition region moves toward the bottom of the cylinder under almost zero force. Although the behavior of the three example cylinders is qualitatively similar, the peak force on the cylinder, as well as the peak strain, have different magnitudes, in agreement with a result in our first paper.
Mixed Modes I and II Concrete Fracture: An Experimental Analysis
Authors: Guo Z. K. , Kobayashi A. S. , Hawkins N. M.
Published: April 2008

The development of the fracture process zone associated with subcritical crack growth in a three-point bend concrete specimen with an off-centered, single-edged precrack was monitored with moire interferometry. The applied load and the crack opening and sliding displacements together with a finite element model of the concrete specimen were used to determine the crack closing stress due to aggregate bridging. Under this mixed-mode fracture, aggregate interlocking increased the crack closing stresses in the fracture process zone and hence the load carrying capacity of the concrete specimen. The dissipated energy rate in the fracture process zone also increased with aggregate interlocking.
Analysis of Vickers Hardness by the Finite Element Method
Authors: Murakami Y. , Matsuda K.
Published: April 2008

A particular formulation of the three-dimensional finite element method specifically for analyzing the Vickers hardness test is established. The Vickers hardness of 0.46 percent carbon steel and 70/30 brass is calculated using the proposed method using the stress-strain curve obtained from a tensile test. The calculated values correlate well with the experimental results for 0.46 percent steel and 70/30 brass. In addition, the analysis predicts the extension of the plastic zone induced by indentation, the stresses at the maximum load, and the residual stresses present after complete removal of the load. At the maximum load there are no tensile stresses in the vicinity of the indenter. However, after removal of the load, large tensile residual stresses are present on the diagonal edge beneath the indentation in the direction perpendicular to the diagonal edge. These results imply that it is necessary to reconsider the accuracy and validity of the conventional indentation method used for the determination of Klc for brittle materials such as ceramics.
Interfacial Zener-Stroh Crack
Authors: Fan Hui
Published: April 2008

Zener-Stroh crack is formed via coalescing dislocations piled up against an obstacle such as an interface of bimaterial. The crack is loaded by the total number of dislocations entered it, while the well-known Griffith crack is loaded by the stress traction acting on the crack surfaces. In the present paper, a Zener-Stroh crack at the interface of an anisotropic elastic bimaterial is formulated with recent improvements in two dimensional anisotropic elasticity and interfacial Griffith crack. Many interesting features of the Zener-Stroh crack are drawn from the present study and compared with those of the Griffith crack.
Antiplane Elastic Wave Scattering From a Curved Randomly Rough Crack
Authors: Bostro¨m A. , Jansson P.-A˚. , Olsson P.
Published: April 2008

The problem of scattering of antiplane elastic waves from a rough crack is solved by means of an extension of the null field approach. The extension consists of the expansion of certain matrix elements in terms of a small parameter followed by an analytical ensemble averaging. The geometry is taken to be two-dimensional, and the scatterer is a curved crack with a small random roughness. Both effects due to overall curvature and effects due to surface roughness are thus included in the analysis. It is assumed that the roughness is one where the height has less effect on the scattering than does the gradient (this is satisfied whenever the correlation length of the surface roughness is much smaller than the curvature of the crack), and some numerical results are given for this case. However, it is a straightforward extension of the analysis to consider cases where the height effects are included.
Eigenfunction Expansion and Higher Order Weight Functions of Interface Cracks
Authors: Chen Yi-Zhou , Hasebe Norio
Published: April 2008

In this paper the properties of the eigenfunction expansion form in the interface crack problem of plane elasticity are discussed in detail. After using the Betti’s reciprocal theorem to the cracked dissimilar bonded body, several path-independent integrals are obtained. All the coefficients in the eigenfunction expansion form, including the K1 and K2 values, and the J-integral can be related to corresponding path independent integrals. Possibility for formulating the weight function is also suggested.
Nonlinear Spatial Equilibria and Stability of Cables Under Uni-axial Torque and Thrust
Authors: Lu C.-L. , Perkins N. C.
Published: April 2008

Low tension cables subject to torque may form complex three-dimensional (spatial) equilibria. The resulting nonlinear static deformations, which are dominated by cable flexure and torsion, may produce interior loops or kinks that can seriously degrade the performance of the cable. Using Kirchhoffrod assumptions, a theoretical model governing cable flexure and torsion is derived herein and used to analyze (1) globally large equilibrium states, and (2) local equilibrium stability. For the broad class of problems described by pure boundary loading, the equilibrium boundary value problem is integrable and admits closed-form elliptic integral solutions. Attention is focused on the example problem of a cable subject to uni-axial torque and thrust. Closed-form solutions are presented for the complex three-dimensional equilibrium states which, heretofore, were analyzed using purely numerical methods. Moreover, the stability of these equilibrium states is assessed and new and important stability conclusions are drawn.
A Global Extremum Principle in Mixed Form for Equilibrium Analysis With Elastic/Stiffening Materials (a Generalized Minimum Potential Energy Principle)
Authors: Taylor J. E.
Published: April 2008

An extremum problem formulation is presented for the equilibrium mechanics of continuum systems made of a generalized form of elastic/stiffening material. Properties of the material are represented via a series composition of elastic/locking constituents. This construction provides a means to incorporate a general model for nonlinear composites of stiffening type into a convex problem statement for the global equilibrium analysis. The problem statement is expressed in mixed “stress and deformation” form. Narrower statements such as the classical minimum potential energy principle, and the earlier (Prager) model for elastic/locking material are imbedded within the general formulation. An extremum problem formulation in mixed form for linearly elastic structures is available as a special case as well.
A Theoretical Study of the Application of the Optical Caustics to High-Temperature Creep Fracture Mechanics
Authors: Ding J. L. , Chen Y. G.
Published: April 2008

In the current study, a theoretical basis is established for interpreting and correlating the optical caustic patterns with the transition of the crack-tip stress and strain fields under high-temperature creep condition. The theory forms a foundation for a possible experimental method based on optical caustics for characterizing the time-dependent fracture at elevated temperatures. Some numerical simulations of the high-temperature caustic phenomena were also performed based on the proposed theory.
An Analytical Model to Predict Optimal Material Properties in the Context of Optimal Structural Design
Authors: Bendsoe M. P. , Guedes J. M. , Haber R. B. , Pedersen P. , Taylor J. E.
Published: April 2008

This paper deals with the simultaneous optimization of material and structure for minimum compliance. Material properties are represented in the most general form possible for a (locally) linear elastic continuum, namely the unrestricted set of elements of positive semi-definite constitutive tensors and cost measures based on certain invariants of the tensors. Analytical forms are derived for the optimized material properties. These results, which apply in general, indicate that the optimized material is orthotropic with the directions of orthotropy following the directions of principal strains. The analysis for optimization of the material leads to a reduced structural optimization problem, for which the existence of solutions can be shown and for which effective methods for computational solution can be devised.
Transient Hygrothermal Stresses Induced in Two-Dimensional Problems by Nonlinear Theory of Coupled Heat and Moisture
Authors: Chen Tei-Chen , Hwang Bai-Hsing
Published: April 2008

According to some experimental data, the value of moisture diffusivity for composite and porous materials is strongly dependent on temperature. Therefore, if the temperature variation of the problem is not confined within a small range, this coefficient may not be regarded as a constant. The purpose of this paper is to study the effect of this temperature-dependent coefficient on the hygrothermal stresses of two-dimensional composite or porous body by nonlinearly coupled hygrothermal theory. In this article, a powerful numerical method, consisting of discretizing the space domain by the finite element method, treating the time domain by Laplace and inverse Laplace transform, and handling the nonlinear term by direct Newton-Raphson iteration, is developed to study the nonlinear coupled transient problem. It can be found from a number of examples that the nonlinear and linear solutions have significant discrepancy in moisture distributions but only a small difference in temperature distributions. In the early stages of the transient period, the induced heat source by rate of moisture based on nonlinear theory is weaker than that based on linear theory. Therefore, the temperature distribution corresponding to linear theory is higher. However, in the latter stage of the transient period, the tendency is the reverse, and the temperature distribution predicted by the nonlinear theory becomes larger.
Automation and Assessment of Augmented Lagrangian Algorithms for Frictional Contact Problems
Authors: Laursen T. A. , Oancea V. G.
Published: April 2008

In recent work, the augmented Lagrangian approach to large deformation frictional contact problems has been advocated for finite element calculations. The resulting algorithms have been shown to facilitate accurate constraint enforcement in a robust manner, while providing an effective technique for removal of the nonsymmetry associated with most frictional constitutive laws. In this work, we examine automation schemes for the algorithm, such that multipliers can be determined to a specified degree of accuracy without user intervention. The performance of the resulting automatic augmentation algorithm is then examined, providing important information about practical attributes of the procedure.
Measurements of Surface Effects on Bio-Fluids Flow in Micro-Channel by Using SPM
Authors: Kanda Kensuke , Yang Ming
Published: April 2008

For the establishment of the design methodologies of micro fluidic chips, the essential analysis of the flow behavior on the micro-meter scale and surface interactions on the nano-scale has been investigated. The understanding of bio-fluid flow behavior in the micro-systems includes both the basic fluid dynamic problems and driving forces from the fields of application. Attention has been focused on the clarification of the surface effects on the solution of bio-molecular flow at micro-scale dimensions. Investigations of pressure drop measurements in bio-molecular flow together with measurements of biomolecular absorption and the lateral forces on various surfaces were carried out on both micro and nano scale. The results demonstrated a clear correlation between flow drag and bio molecular interaction with the surface. The validity is demonstrated of the evaluation method suggested in this paper.
Incorporating Finite Element in Mechanical Engineering Technology Program via Three Existing Courses and by Introducing a Senior Level Elective in the Curriculum
Authors: Mitra Aniruddha
Published: April 2008

Finite Element Analysis has become a powerful tool for Industry, specially, in the Design and Development sector. In response to that, Mechanical Engineering Programs followed by Mechanical Engineering Technology programs all across the country are incorporating Finite Element Analysis as a part of their curricula. This paper describes the distribution of Finite Element Analysis amongst the junior and senior level courses in Mechanical Engineering Technology curriculum at Georgia Southern University. The links between these classes with sophomore classes are established. A stand alone senior level elective course that covers more in depth of Finite Element theory is also developed.
Conceptual Designs of Strong Hybrid Vehicle Powertrains
Authors: Liao Gene Y. , Weber Trudy R. , Sarbacker Shawn D. , Pfaff Donald P.
Published: April 2008

This paper describes four conceptual designs of strong hybrid vehicle powertrains. These concepts enable conversion of conventional powertrains into strong hybrid powertrains with minimal tear-up to the existing architecture. These concepts are configured as follows: (1) incorporates an electric machine attached to the front axle of a conventional rear-wheel-drive vehicle; (2) a Flywheel-Alternator-Starter (FAS) system with a motor placed between the torque converter and the transmission; (3) same as previous one but where the torque converter is replaced by a starting clutch; and (4) a dual mode Electric Variable Transmission (EVT). These concepts provide extensive hybrid functionality such as, electric motor-only drive; launch assist, braking energy recovery and regeneration. Simulation results indicate that the proposed strong hybrid concepts have the potential to provide fuel economy gains of 19% to 26% over conventional powertrains.
Commercializing an Automatically Deployable Rollover Protective Structure (AutoROPS) for a Zero-Turn Riding Mower: Initial Product Safety Assessment Criteria
Authors: Etherton J. R. , McKenzie E. A. , Powers J. R.
Published: April 2008

Fatal injuries have occurred to operators of zero-turn riding mowers when these machines rolled over during high speed sharp turns or on uneven terrain. These mowers are frequently operated in low clearance conditions such as around trees and when loaded onto low-roofed trailers. The automatically deployable rollover protective structure (AutoROPS) can provide both protection during rollover events and the capability to operate a mower in low clearance conditions. Until recently, AutoROPS technology development has occurred only in a government laboratory. In the current phase of development, private industry has taken an interest in the AutoROPS technology and is pursuing, with NIOSH, the product testing and development needed to commercialize the AutoROPS on a zero-turn riding mower. The government’s role, as a partner with private industry in bringing new safety technology into practical application, is discussed. Importantly, for the AutoROPS product to be as effective as possible, it should not introduce additional, unacceptable risks. Previous product safety assessments led by government laboratories are reviewed. These assessments were made to minimize hazards in products developed in government labs. A product safety assessment was performed on the AutoROPS during its design phase. In addition to minimizing the severity and frequency of operator injury resulting from an accidental rollover, the assessment considered 1) environmental factors such as corrosion, electromagnetic interference, and vibration; 2) human error avoidance; and 3) safeguard reliability analysis. This assessment was a cooperative effort between the safety engineering design team at the Division of Safety Research of the National Institute for Occupational Safety and Health; a ROPS manufacturer; and a zero-turn riding mower manufacturer. Design features are being incorporated into the prototype AutoROPS to address hazards encountered in normal use of these machines.
Use of an Air Process Control Trainer to Teach PID Control
Authors: Bluestein Maurice
Published: April 2008

In the Mechanical Engineering Technology (MET) program at Indiana University - Purdue University Indianapolis (IUPUI), all bachelor degree students are required to take a course in Instrumentation. This course includes material on measuring and controlling mechanical parameters such as temperature, pressure and flow. Students are taught the basis of feedback control systems, primarily proportional-integral-derivative (PID) control. The MET approach is physical, rather than the mathematical approach favored by electrical engineering technology. Such a pedagogical method relies on laboratory equipment and experiments whereby the features of PID control may be properly demonstrated. As an example, the student observes how different PID settings affect the fan speed in the control of air flow through a duct. Through the support of an ILI grant from the National Science Foundation, the MET program was able to purchase six Air Process Control Trainers to be used with personal computers supplied by the MET department. These units are used to control air speed and temperature in forced air flow through an instrumented duct. This paper will describe the equipment, the experimental procedure utilized, and the results, with a summary of the benefits to the students.
Force Dipoles in Anisotropic Materials: Cell Orientation Guided by Substrate Anisotropy?
Authors: Pan E.
Published: April 2008

Recent studies on cell orientation have shown that cells can actively sense the elastic properties of their environment and strengthen contacts and cytoskeleton in a direction of large effective stiffness. For example, it was found that cells oriented perpendicular to clamped boundaries whilst parallel to free boundaries. It was also suggested that active mechanosensing in an elastically anisotropic medium might lead to cell orientation. In this paper, we first develop an analytical force-dipole solution in anisotropic materials. We then apply this solution to investigate the effect of substrate anisotropy on cell orientation. In our numerical examples, the substrate will be assumed to be cubic, but oriented in different orientations. The interactive energy of the cells is calculated for different boundary conditions (free and clamped) on the surface of the anisotropic substrate.
Warpage Analysis of Panelized Molding Process for Plastic IC Packages
Authors: Vijayakumar Bhuvaneshwaran , Guo Yifan
Published: April 2008

Panelized molding process is vastly used in low cost molding process for PBGA (Plastic Ball Grid Array), LGA (Land Grid Array), QFP (Quad Flat Pack) and other types of packages. In a panelized molding process, arrays of packages are assembled on a substrate board, which is then molded as a single panel. After the molding process, the package array is cut into single packages. When laminated substrates are used, panel warpage formed during the molding process is very common due to the mismatches of material properties in the substrates and molding compounds. The warpage, however, is one of the major issues in the back-end assembly process. For example, the warpage can cause great difficulties in singulation. Large warpage could also cause high stresses in the components and results in reliability problems in the packages. In this paper, a 3-D finite element model is created to study the relations between the panel warpage and the material properties of the substrate boards and mold compounds. In a 40mmx50mm panel area, the model shows that the global warpage can be as high as +/-10 mils (0.25 mm) using different mold compounds. Test vehicles are assembled to validate the simulation results. The measurement data on warpage from the testing vehicles, although at first seems to vary over a large range across different panel designs, a closer observation and analysis suggests a definite trend and a strong correlation between the substrate panel and the mold compound properties.
Dynamics of Thermal Field and Powder Sublimation in an Inductively Heated AlN Bulk Crystal Growth Process
Authors: Wu Bei , Zhang Hui
Published: April 2008

In this paper, an integrated model considering induction heating, transient heat transfer and crystal growth has been developed to study dynamic response of temperature and powder sublimation in an aluminum nitride (AlN) growth system. The electromagnetic field and induction heat generation are calculated by the Maxwell equations. Transient temperature distribution in the growth chamber is simulated by energy equation accounting for conduction/radiation within and between various components. In order to provide proper temperature control during sublimation growth, dynamic responses of temperature and temperature difference of the bottom and top external surfaces of the growth crucible to power variation and coil position movement are simulated. Finally the crystal and powder shapes as a function of time are predicted and compared with dynamic experimental observation.
Thermodynamic Study of Influence of Steam Injection in Combustion Chamber of Simple Gas/Steam Combined Cycle
Authors: Yadav J. P. , Singh Onkar
Published: April 2008

Steam injection is seen as one of the popular ways for power augmentation by number of turbine manufacturers and number of steam injected turbines such as Allison 501-K, GE LM 2500, and LM5000 are already in use. This paper presents the thermodynamic study of influence of steam injection in combustion chamber of topping cycle in a simple gas / steam combined cycle power plants upon the efficiency and specific work out put of topping cycle, bottoming cycle and combined cycle. The simple gas / steam combined cycle power plant configuration considered for the study has topping cycle gas turbine with film cooled stages employing air / steam as coolants and single pressure steam generation in the heat recovery steam generator (HRSG). Air for cooling has been bled out from compressor depending upon the requirement and the steam requirement as coolant is met from the steam generated in heat recovery steam generator (HRSG). Thermodynamic analysis of the simple combined cycle configuration considered has been completed with the variation in various parameters such as cycle pressure ratio, type of coolant used for gas turbine stages, mass fraction of the steam being injected in combustion chamber of topping cycle. Results obtained have been plotted suitably for the critical evaluation of influence of one parameter upon the other.
Three-Dimensional Quantification of Multi-Point Contact Loads During Lumbar Spinal Manipulation
Authors: Gudavalli Maruti R. , Rowell Robert M.
Published: April 2008

The objective of this study was to measure the complete three-dimensional loads at each of the support contacts namely both hand contacts, and the support loads at the rib cage and the pelvis during chiropractic treatments for low back pain. Two small force transducers were used to measure hand contact loads, and a specially instrumented force plate table was used for measuring support loads. A doctor of chiropractic delivered fourteen spinal manipulations to the lumbar spines of five subjects during a period of three weeks. The results showed that there are three dimensional loads at each of the four contact points. The loads at the thrusting hands reached as high as 382N. For the stabilizing hands the maximum loads were 160N. The support loads reached as high as 727N at the pelvic support and 660N at the rib cage support. This study reports for the first time data on the loads at each of the hand contact points and the support locations during chiropractic spinal manipulation.
An Illustrated Technique for Assessing the Risk From Phenomenological Events Involving Fluid Leakage
Authors: Everline C. J.
Published: April 2008

Leakage, especially in confined spaces, can result in hazardous concentrations of toxic or flammable fluids. Quantifying the probability that a hazardous condition occurs is dependent upon the leakage frequency, the fluid flow rate, mixing between the leaking fluid and ambient environment, the hazardous limits for the resulting mixture, as well as the time available for mitigation measures. This paper describes a generic technique for quantifying the probability that a hazardous condition occurs, and provides an illustration of the methodology application.
Analytical Predictive Modeling of Serrated Chip Formation in High Speed Machining of 7075-T6 Aluminum Alloy
Authors: Fang Ning , Yang Juhchin , Liu Nan
Published: April 2008

High speed machining has received increasingly broad applications in various industries, especially in the aircraft and aerospace industry, where a large number of structural frames are machined. Based on Manyindo and Oxley’s descriptive model of serrated chip formation, this paper proposes a new mathematical model for high speed machining of 7075-T6 aluminum alloy. The new model integrates Johnson-Cook’s material model with Oxley’s machining theory and is validated by using the published experimental data. A good agreement between the predicted and experimental degree of chip segmentation is reached. The effects of cutting conditions and tool geometry on the serrated chip geometry, the cutting forces, and the shear-plane angles are quantitatively investigated. The analysis shows that a large undeformed chip thickness, a negative tool rake angle, and a high cutting speed strengthen the degree of chip segmentation in high speed machining.
Fiber Bragg Grating Sensors for Measurement of Tool Displacement
Authors: Bartow Matthew J. , Bayly Philip V. , Mann Brian P.
Published: April 2008

This work introduces a novel method for measuring machine tool displacement using embedded fiber Bragg grating strain sensors. Fiber Bragg grating sensors have many advantages including greatly reduced size, immunity to electromagnetic interference, and high operating temperature resistance, which makes them a good choice for manufacturing applications. The fiber optic system components were tailored to meet the dynamic requirements of a micro-machining environment. A simple bench-top cantilever beam apparatus was instrumented to demonstrate the feasibility of the measurement approach. Sensors were then potted in the through-coolant holes of a 1/8” (3.175mm) carbide micro end-mill using a high-viscosity gap-filling cyanoacrylate adhesive applied through a custom suction device. The results of modal tests using the small, lightweight Bragg sensors are compared with conventional hammer and accelerometer modal analysis techniques. The measurement of tool motion during cutting is demonstrated with a series of lathe-cutting tests.
Modeling, Analysis, and Control of a Four Wheel Steer-by-Wire System for Semi-Autonomous Ground Vehicles
Authors: Ancha Santosh , Baviskar Abhijit , Wagner John , Dawson Darren
Published: April 2008

Hybrid ground vehicles have motivated electric and steer-by-wire steering system technology due to restrictions on power source availability. Although these two steering systems are efficient, flexible, and environment friendly, the steer-by-wire system provides the opportunity for semi-autonomous and autonomous vehicle operation, as well as compliments a drive-by-wire architecture. For greater lateral vehicle performance, reduced maneuver transient time, and avoidance of undesirable vehicle motions through combined traction and steering control, a four wheel steering assembly with front and rear steering mechanism can uniformly control the wheels’ steering angle. In this paper, mathematical models will be developed for a front and rear rack and pinion steer-by-wire system. Accompanying linear and nonlinear controllers will be designed for operator commanded tracking by adjusting the three servo-motor assemblies. Representative numerical results are presented and discussed to support the evaluation of the four-wheel steering systems for sinusoidal and impulse-like steering maneuvers. The simulated vehicle four wheel steer-by-wire system results demonstrated better performance compared to the front steer-by-wire system.
Performance Prediction of a Novel Design for Turbine Vane Film Cooling With Low Aerodynamic Loss and High Effectiveness
Authors: York William D. , Leylek James H.
Published: April 2008

A new film-cooling scheme for the suction surface of a gas turbine vane in a transonic cascade is studied numerically. The concept of the present design is to inject a substantial amount of coolant at a very small angle, approaching a “wall-jet,” through a single row of relatively few, large holes near the vane leading edge. The near-match of the coolant stream and mainstream momentums, coupled with the low coolant trajectory, theoretically results in low aerodynamic losses due to mixing. A minimal effect of the film cooling on the vane loading is also important to realize, as well as good coolant coverage and high adiabatic effectiveness. A systematic computational methodology, developed in the Advanced Computational Research Laboratory (ACRL) and tested numerous times on film-cooling applications, is applied in the present work. For validation purposes, predictions from two previous turbine airfoil film-cooling studies, both employing this same numerical method, are presented and compared to experimental data. Simulations of the new film-cooling configuration are performed for two blowing ratios, M=0.90 and M=1.04, and the density ratio of the coolant to the mainstream flow is unity in both cases. A solid vane with no film cooling is also studied as a reference case in the evaluation of losses. The unstructured numerical mesh contains about 5.5 million finite-volumes, after solution-based adaption. Grid resolution is such that the full boundary layer and all passage shocks are resolved. The Renormalization Group (RNG) k-ε turbulence model is used to close the Reynolds-averaged Navier-Stokes equations. Predictions indicate that the new film-cooling scheme meets design intent and has negligible impact on the total pressure losses through the vane cascade. Additionally, excellent coolant coverage is observed all the way to the trailing edge, resulting in high far-field effectiveness. Keeping the design environment in mind, this work represents the power of validated computational methods to provide a rapid and reasonably cost-effective analysis of innovative turbine airfoil cooling.
Wear Characteristics of Fiber-Reinforced Dental Bio-Composites
Authors: Callaghan D. J. , Vaziri A. , Nayeb-Hashemi H.
Published: April 2008

From the available biocompatible fibers, glass fibers have drawn the most attention due to their esthetic qualities and easy manipulation. While some investigators have studied the effect of the fibers on mechanical properties such as ultimate strength and fracture resistance of these bio-composites [1], the literature survey reflects that there are very few studies on the wear properties of such fiber-reinforced bio-composites. Thus, the main objective of this study is to investigate the wear characteristics of the fiber-reinforced dental bio-composite. The relationship between fiber weight fraction and fiber length of glass fibers incorporated into a dental resin and the wear resistance of these bio-composites is studied for various applied loads. For comparison, a particle filled bio-composite was also subjected to the wear test. The main objective of this study is to gain some insight into the micromechanisms of wear of these dental bio-composites and their relative performance.
Roots Compressor: High Temperature Testing and Modeling
Authors: Blekhman David I. , Mollendorf Joseph C. , Felske James D. , Lordi John A. , Joshi Ashish M.
Published: April 2008

The Roots compressor has enjoyed a multitude of applications. Retuned to produce a high-temperature stream of gas, the Roots compressor can be a part of such applications as pyrolitic synthesis, chemical decomposition, optical fiber production and experimental studies. Presently, it appears that by using advanced materials, a prototype capable of withstanding temperatures up to 1500–2000 K could be built. A series of experiments was performed and various performance data were recorded at 2280 and 3430 rpm. The maximum steady state temperature achieved and the corresponding pressure ratio were 660 K and 3.9. Numerical modeling revealed a good correlation for pressure ratios up to 3. While the outlet pressure signature was accurately reproduced, the magnitude of the actual pressure fluctuation was somewhat in error. A more detailed physical model of gas dynamic processes could improve the agreement. The calculations were based on measurements of the internal leakage, need for modeling of which is emphasized.
Analysis of the Vibration Response of a Gearbox With Gear Tooth Faults
Authors: Tian Xinhao , Zuo Ming J. , Fyfe Ken R.
Published: April 2008

In this study, the steady-state vibration response of a gearbox with gear tooth faults is investigated. Based on the analytical expression of the position-dependent mesh stiffness of the gear with perfect gear teeth derived with the potential energy method and the characteristics of involute gear teeth, expressions of the mesh stiffness of a gear with tooth faults such as tooth chip, tooth crack, and tooth breakage are derived. Using a coupled lateral and torsional vibration model of a one-stage spur gear pair, we have numerically solved a set of nonlinear equations and obtained typical vibration response diagrams of the gear pair with perfect gears and gears with tooth faults. This study reveals the relationship between the waveforms of the vibration and the types of local faults of the gear. These results are useful for identification of vibration signatures when there are these types of tooth faults.
Dynamics Modeling of “CEDRA” Rescue Robot on Uneven Terrains
Authors: Meghdari A. , Mahboobi S. H. , Gaskarimahalle A. L.
Published: April 2008

In this paper an effective approach for kinematic and dynamic modeling of high mobility wheeled mobile robots (WMR) has been presented. As an example of these robots, the method has been applied on CEDRA rescue robot which is a complex, multibody mechanism. The model is derived for 6-DOF motions enabling movement in x, y, z directions, as well as pitch, roll and yaw rotations. Forward kinematics equations are derived using Denavit-Hartenberg method and the wheels Jacobian matrices. Moreover the inverse kinematics of the robot is obtained and solved for the wheel velocities and steering commands in terms of desired velocity, heading and measured link angles. Finally dynamical analysis of the rover has been thoroughly studied. Due to the complexity of this multi-body system especially on rough terrain, Kane’s method of dynamics has been used to model this problem. The approach has been developed in such a way that it can easily be extended to other mechanisms and rovers.
Intelligent Monitoring and Measurement of Tool Wear for the Turning of Stainless Steel Parts
Authors: Liu Tien-I , Song Shin-Da
Published: April 2008

Cutting forces were used as indices in this research for the monitoring and measurement of tool wear during the turning of stainless steel parts. Virtual instrumentation was applied to extract the fourteen features from cutting force signals. The best combination of features, which would be used as input vectors for on-line monitoring and measurement, was selected by using a Sequential Forward Search (SFS) algorithm. Adaptive neuro-fuzzy inference systems (ANFIS) were used for the recognition of tool wear. The tool conditions, which are either usable or worn out, are the outputs for on-line monitoring. The outputs for on-line measurement are estimated values of tool wear. When ANFIS was applied, three features were needed for the monitoring of tool wear. They are the average of radial force, the average of tangential force, and the skewness of tangential force. For on-line measurement, four features were used as inputs. The input vector includes the average of radial force, the average of tangential force, the skewness of tangential force, and the kurtosis of longitudinal force. For the on-line monitoring of turning tool conditions, a 7 × 2 ANFIS can achieve a success rate of higher than 96% to distinguish usable tools from worn-out tools. For the on-line measurement of tool wear, the average flank wear estimation error is below 8.9% using a 3 × 3 ANFIS.
Valve Controlled Teleoperated Skid Steered Mobile Machine
Authors: Vilenius Jani M. , Raneda Albert , Hyvo¨nen Mika O. , Uusisalo Jarno R. A. , Huhtala Kalevi J.
Published: April 2008

The goal of the paper is to study the properties of a teleoperated mobile machine and produce a simulation model of the machine for later use. In this paper there are introduced a prototype of the teleoperated mobile machine and a simulation model of that machine. The challenge in teleoperation is to have a smooth and accurate control of the machine, because the operator can not feel any force. The machine is valve controlled and because of that the influence of different type of valves can be significant for the control of the machine. By means of the simulation model it is possible to test new components and hydraulic solutions for power transmission of mobile machine. The new computer controlled prototype of the teleoperated mobile machine is electrically controlled with proportional valves has been developed. The simulation model of the machine is verified with the measurements. The goal is that the main properties of computer controlled and teleoperated mobile machine are at least at the same level than in normal mechanically controlled machine, but controllability must be better because of the teleoperation. In this paper there is also introduced the principle of the automatic virtual gearbox. The prototype is equipped with two constant displacement pumps, electrically controlled pressure relief valve and supply pressure and LS pressure sensor. Therefore the information of load pressure is available and supply pressure can be controlled with the rotational speed of diesel engine and pressure relief valve. In teleoperated mobile machine the rotational speed of diesel engine is controlled with electric gas. With these components and a computer control it is possible to set supply pressure level according to the needed load pressure level.
The Technology Maturity of Product and Its Mapping
Authors: Zhang Huangao , Tan Runhua , Zhao Wenyan
Published: April 2008

Technology maturity (TM) of product is a crucial index for enterprises. But the existing methods of technology maturity mapping do not always work. By integrating some fruits of Altshuller and Darrell Mann, a technique of mapping technology maturity of product based on patent analysis was put forward. The product lifecycle was subdivided, and the algorithm and approaches of mapping TM were discussed. On the basis of above technique the software named TMMS was developed. As an illustration the TM of butterfly valve was mapped by TMMS.
Simulation of Machined Surface Formation While Honing
Authors: Gouskov Alexander M. , Voronov Sergey A. , Butcher Eric A. , Sinha Subhash C.
Published: April 2008

The dynamics of deep hole honing is considered. The mathematical model of the process including the dynamic model of the tool and the interaction of the workpiece surface and honing sticks is analyzed. The honing tool is modeled as a continuous slender beam with a honing mandrel attached at the intermediate cross section. A single row of stones tool rotates and has reciprocational motion in the axial direction. The honing stones are expanded to the machined surface by a special rigid mechanism that provides cutting of workpiece cylindrical surface. The removal of chip and the tool vibrations cause the variation of expansion pressure and depend on the surface state formed by previous honing stone. The equations of new surface formation are separated as a specific set of the dynamic model. These equations inherently consider the regenerative effect of oscillations during machining. The numerical algorithm of machined surface generation has been developed which facilitates the 3D graphical representation and evaluation of the topography of the generated surface. The simulation model accounts for not only the nominal tool motion but also takes into account errors during machining such as tool components deformations and vibrations, tool runout, as well as initial surface distortions produced by previous operation. Based on the surface formation model software for evaluation of typical surface quality and accuracy criteria such as eccentricity, out-of-round, conicity, barrel, axial waviness, misalignment, faceting has been developed. The expansion pressure, tool stiffness, and technology conditions are considered as varying parameters since their influence on the process are different. The process productivity and accuracy can be improved by choosing rational conditions evaluated by simulation. The corresponding models and results of numerical simulation are presented. All the results are given in dimensionless form and therefore they are applicable to a wide range of real manufacturing process conditions. The model of new surface formation presented allows the simulation of the machined surface topography variation in time and to predict workpiece accuracy and possible correction of surface errors.
Mechanical Smoke Exhaust for Small Retail Shop Fires
Authors: Shi C. L. , Li Y. Z. , Huo R. , Yao B. , Chow W. K. , Fong N. K.
Published: April 2008

The performance of mechanical smoke exhaust systems in a small retail shop fire will be evaluated. A series of full-scale burning tests will be carried out and the results will be justified by numerical experiments. A zone model has been developed to predict the fire growth in small retail shops with different equations on axisymmetric fire plume entrainment and spill plume. In addition to verifying the developed model, the results will also be compared with those predicted by another zone model CFAST (version 5.01) and a field or computational fluid dynamics model Fire Dynamics Simulator FDS code (version 3). The correlation between the mechanical exhaust rate and plume entrainment rate for keeping the smoke layer interface at a certain height under a steady burning fire will be analyzed. Further, the application of different plume correlations will be investigated. The effectiveness of mechanical exhaust in retail shop fires will be discussed and some factors affecting the system performance will be analyzed.