Engineering Commons^™

On-Line Free Form Surface Measurement Via A Fuzzy-Logic Controlled Scanning Probe, Ming Chang, Paul P. Lin

Mechanical Engineering Faculty Publications

This paper presents a system and methodology for on-line free form surface measurement via a scanning contact probe installed on a CNC (computer numerical control) machine. The scanning probe provides more sampling points than any traditional touch trigger type of probes used on CNC machines, and better measuring accuracy than laser displacement sensing or structured lighting. The presented measuring system's main advantage is that the number of measured points can vary with the change of surface curvature. To improve the measuring stability and continuity, fuzzy logic control, in lieu of traditional PID control, is employed. As a result, the …

On The Detachment Of Step-Tapered Doublers: Part 2—Evolution Of Pressure Loaded Structures, Anette M. Karlsson, W. J. Bottega

Mechanical Engineering Faculty Publications

One-dimensional edge debonding of layerwise step-tapered patches from both flat and cylindrical structures subjected to applied pressure is studied in the context of the general formulation presented in Part 1. Numerical simulations based on analytical solutions of the problems of interest are performed and intricate results presented in the form of threshold curves/delamination paths for various taper angles and support conditions. Configurations corresponding to full contact of the debonded segments, edge contact of the debonded segments and no contact of the debonded segments of the evolving composite structure are included in the model and found to significantly affect the predicted …

On The Detachment Of Step-Tapered Doublers : Part 1—Foundations, W. J. Bottega, Anette M. Karlsson

Mechanical Engineering Faculty Publications

One-dimensional edge debonding of layerwise step-tapered patches from both flat and cylindrical structures is examined. The problems are approach from a unified point of view, as propagating boundary problems in the calculus of variations, with the models for both flat and curved structures being formulated simultaneously. The effects of a contact zone adjacent to the bonded region are incorporated as is the phenomenon of edge-point contact. The formulation results in a selfconsistent representation of the various intact and debonded segments of the composite structure comprised of a multilayer patch and a base structure. It concurrently yields the conditions which establish …

The Presence Of Edge Contact And Its Influence On The Debonding Of Patched Panels, Anette M. Karlsson, W. J. Bottega

Mechanical Engineering Faculty Publications

A formulation is presented which accounts for configurations of debonding patched cylindrical panels for which the edge of the debonded segment of the patch maintains sliding contact with the corresponding base structure. The formulation is incorporated with that which accounts for configurations for which a contact zone is present and for which no contact between the debonded segments of the patch and base structure occurs during debonding. Analyses are performed for two types of loading conditions: Applied circumferential tension and applied internal pressure. Results of numerical simulations based on analytical solutions of the problems of interest are presented in the …

The Dynamics Of Rotor With Rubbing, Jerzy T. Sawicki, Joe Padovan, Rabih Al-Khatib

Mechanical Engineering Faculty Publications

This paper presents the description of some phenomena associated with dynamic behavior of rotors interacting with stationary components. Numerical simulations show rotor vibration spectrum rich in subharmonic, quasi-periodic, and chaotic vibrations. The nonlinear calculation techniques are applied to demonstrate the changes of the vibration patterns for different operating conditions. Some conclusions are discussed with regard to unique characteristics of rub-induced rotor response, initial conditions, as well as appropriate ranges of system parameters. Of special interest are the changes in the apparent nonlinearity of the system dynamics as rubs are induced at different rotor speeds. In particular, starting with 2nd order …

Computer-Assisted Gait Analysis In Equine Orthopaedic Practice: The Case For Inverse Dynamic Analysis, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

No abstract provided.

Nonlinear Vibrations Of Fractionally Damped Systems, Joe Padovan, Jerzy T. Sawicki

Mechanical Engineering Faculty Publications

This paper deals with the harmonic oscillations of periodically excited nonlinear systems where hysteresis is simulated via fractional operator representations. Employing a diophantine version of the fractional operational powers, the energy constrained Lindstedt–Poincaré perturbation procedure is utilized to establish the harmonic solution. The constrained perturbation procedure was employed since it allows for the handling of strong damping and exciting forces over the full span of the driving frequency range. Based on the approach taken, the long time behavior of the fractionally damped Duffing's equation is studied in detail. Of special interest is the determination of the influence of fractional order …

Mechanical Properties Of The Tendinous Equine Interosseus Muscle Are Affected By In Vivo Transducer Implantation, M. O. Jansen, H. C. Schamhardt, Antonie J. Van Den Bogert, W. Hartman

Mechanical Engineering Faculty Publications

Liquid metal strain gauges (LMSGs) were implanted in the tendinous interosseous muscle, also called suspensory ligament (SL), in the forelimbs of 6 ponies in order to quantify in vivo strains and forces. Kinematics and ground reaction forces were recorded simultaneously with LMSG signals at the walk and the trot prior to implantation, and 3 and 4 days thereafter. The ponies were euthanised and tensile and failure tests were performed on the instrumented tendons and on the tendons of the contra lateral limb, which were instrumented post mortem. The origo–insertional (OI) strain of the SL was computed from pre- and post-operative …

Diophantinized Fractional Representations For Nonlinear Elastomeric Media, Joe Padovan, Jerzy T. Sawicki

Mechanical Engineering Faculty Publications

This paper explores the use of diophantinized fractional fits for the nonlinear constitutive representation of elastomeric media. These are caste in terms of either the principal stretches or the strain invariants. Both polynomial and rational forms are considered. To construct the requisite complete and physically admissible basis space, the diophantinized set of fractional powers is bound by the curvature properties of the experimental data set. This set is then employed in conjunction with a remezed least square scheme to obtain an optimal fit. To verify the scheme a sample application case is presented.

Comments On Response Errors Of Non-Proportionally Lightly Damped Structures, W. Gawronski, Jerzy T. Sawicki

Mechanical Engineering Faculty Publications

Letters to the editor authors reply

Balanced Dissipative Controllers For Flexible Structures, W. Gawronski, Jerzy T. Sawicki

Mechanical Engineering Faculty Publications

A balanced approach to shaping the closed-loop properties of the dissipative controllers for flexible structures is presented. In the balanced representation the properties of flexible structures are introduced, and a simple method of designing of the dissipative controllers is obtained. It relates the controller gains with the closed-loop pole locations. The examples illustrate the accuracy of the design method.

Diophantine Type Fractional Derivative Representation Of Structural Hysteresis, Part Ii: Fitting, Computational Mechanics, Jerzy T. Sawicki, Joe Padovan

Mechanical Engineering Faculty Publications

Part I of this series introduced the diophantinized fractional model and the decompositional formulation. The various important properties of fractional continuum formulation and its decomposed version were developed. In Part II the dynamic properties of the diophantine representation are investigated. The model fitting scheme will be developed to handle an arbitrary frequency dependent structural hysteriesis. This is followed up with the results of benchmark studies which demonstrate the effectiveness of fitting.

Diophantine Type Fractional Derivative Representation Of Structural Hysteresis, Part I: Formulation, Joe Padovan, Jerzy T. Sawicki

Mechanical Engineering Faculty Publications

Based on a diophantine representation of the operational powers, a fractional derivative modelling scheme is developed to simulate frequency dependent structural damping. The diophantine set of powers is established by employing the curvature properties of the defining empirical data set. These together with a remezed least square scheme are employed to construct a Chebyschev like optimal differintegro simulation. Based on the use of the rational form resulting from the diophantine representation, a composition rule is introduced to reduce the differintegro simulation to first order form. The associated eigenvalue/vector properties are then explored. To verify the robustness-stability accuracy of the overall …

System Identification Methods For Dynamic Testing Of Fluid-Film Bearings, Jerzy T. Sawicki, M. L. Adams, R. J. Capaldi

Mechanical Engineering Faculty Publications

There are various system identification approaches typically used to extract the rotordynamic coefficients from simultaneously measured dynamic force and motion signals. Since the coefficient values extracted can vary significantly as a function of the system identification approach used, more attention is needed to treat this issue than is typically included in the rotor dynamics literature. This paper describes system identification and data reduction methods used for extracting rotordynamic coefficients of fluid-film journal bearings. Data is used from a test apparatus incorporating a double-spoolshaft spindle which permits independent control over the journal spin speed and the frequency of an adjustable-magnitude circular …

Oscillating Flow In Channels With Sudden Change In Cross Section, Mounir B. Ibrahim, Waqar Hashim

Mechanical Engineering Faculty Publications

In this paper, we have computationally examined oscillating flow (zero mean between) two parallel plates with a sudden change in cross section. The flow was assumed to be laminar incompressible with the inflow velocity uniform over the channel cross section but varying sinusoidally with time. The cases studied cover wide ranges of Re_max (from 187.5 to 2000), Va (from 1 to 10.66), the expansion ratio (1:2 and 1:4) and A_r (2 and 4). Also, three different geometric cases were discussed: (a) asymmetric expansion/contraction; (b) symmetric expansion/contraction; and (c) symmetric blunt body. For these oscillating flow conditions, the fluid …

A Fringe Center Detection Technique Based On A Sub-Pixel Resolution, And Its Applications Using Sinusoidal Gratings, Ming Chang, Paul P. Lin, Wen Chih Tai

Mechanical Engineering Faculty Publications

A common problem in optical profilometry is the accuracy in locating fringe centers. This paper presents an accurate fringe center detection technique based on sub-pixel resolution using the fringe projection method. An optimum reconstruction filter is developed which has low sensitivity to noise. In fringe center detection, computer simulation results of using one-pixel and sub-pixel resolutions are compared. The detection technique is then applied to radius measurement of cylindrical objects and surface profile measurement of diffuse objects. The experimental results thus obtained through the proposed optimum reconstruction filter show significant improvement in measurement accuracy.

A Kalina Cycle Application For Power Generation, Mounir B. Ibrahim, Ronald M. Kovach

Mechanical Engineering Faculty Publications

A multi-component (NB₃/H₂O) Kalina-type cycle that utilizes the exhaust from a gas turbine is investigaed in this paper. The turbine-inlet pressure of 5.96 × 10⁶N/m² and temperature of 755.372 K were kept constant, as well as the working fluid temperature at the condenser outlet (at 290K). The HN₃ mass fraction at the turbine inlet was varied along with the seperator temperature and the effects on the cycle efficiency were studied. The relationships between turbine-inlet flow and the seperator-inlet. How are shown in addition to the upper and lower HN₃ mass-fraction bounds. …

Laminar/Turbulent Oscillating Flow In Circular Pipes, Kyung H. Ahn, Mounir B. Ibrahim

Mechanical Engineering Faculty Publications

A two-dimensional oscillating flow analysis was conducted simulating the gas flow inside Stirling engine heat exchangers. Both laminar and turbulent oscillating pipe flow were investigated numerically for Re_max = 1,920 (Va = 80), 10,800 (Va = 272), 19,300 (Va = 272), and 60,800 (Va = 126). The results are here compared with experimental results of previous investigators. Predictions of the flow regime on present oscillating flow conditions are also checked by comparing velocity amplitudes and phase difference with those from laminar theory and quasi-steady profile. A high Reynolds number k-ε turbulence model was used for turbulent oscillating pipe flow. …

Comparison Of Analysis And Experiment For Gearbox Noise, Fred B. Oswald, A. F. Seybert, T. W. Wu, William J. Atherton

Mechanical Engineering Faculty Publications

Low-contact-ratio spur gears were tested in the NASA gearnoise rig to study the noise radiated from the top of the gearbox. Experimental results were compared with a NASA acoustics code to validate the code for predicting transmission noise. The analytical code is based on the boundary element method (BEM) which models the gearbox top as a plate in an infinite baffle. Narrow-band vibration spectra measured at 63 nodes on the gearbox top were used to produce input data for the BEM model. The BEM code predicted the total sound power based on this measured vibration. The measured sound power was …

Effect Of Operating Conditions On Gearbox Noise, Fred B. Oswald, James J. Zakrajsek, Dennis P. Townsend, William Atherton, Hsiang Hsi Lin

Mechanical Engineering Faculty Publications

Low-contact-ratio spur gears were tested in the NASA gear noise rig to study the noise radiated from the top of the gearbox. The measured sound power from the gearbox top was obtained from a near-field acoustic intensity scan taken at 63 nodes just above the surface. The sound power was measured at a matrix of 45 operating speeds and torque levels. Results are presented in the form of a spectral speed map and as plots of sound power versus torque (at constant speed) and as sound power versus speed (at constant torque) Because of the presence of vibration modes, operating …

Data Communication Between An Expert System Shell And A Conventional Algorithmic Program With Application To Cam Motion Specification, Paul P. Lin, An-Jen Yang

Mechanical Engineering Faculty Publications

Although more and more expert system shells have begun to provide communication interfaces to conventional procedural languages, the interfaces are basically shell- and language-dependent. This paper presents a simple, shell- and language-independent data communication technique between a shell and a procedural language via a concept analogous to the handshake data transmission used in microprocessors. A control file is used for the action of handshake. The communication interface is between two data files in two different language environments. A program written in a LISP-based expert system shell, OPS 5, and one written in a procedural language, FORTRAN, were …

A Turbulence Model For The Heat Transfer Near Stagnation Point Of A Circular Cylinder, Mounir B. Ibrahim

Mechanical Engineering Faculty Publications

A one-equation low-Reynolds number turbulence model has been applied successfully to the flow and heat transfer over a circular cylinder in turbulent cross flow. The turbulence length-scale was found to be equal 3.7y up to a distance 0.05δ and then constant equal to 0.185δ up to the edge of the boundary layer (wherey is the distance from the surface and δ is the boundary layer thickness).

The model predictions for heat transfer coefficient, skin friction factor, velocity and kinetic energy profiles were in good agreement with the data. The model was applied for Re ≤250,000 and Tu_{∞ …}

Automated Acoustic Intensity Measurements And The Effect Of Gear Tooth Profile On Noise, William J. Atherton, Adam Pintz, David G. Lewicki

Mechanical Engineering Faculty Publications

Acoustic intensity measurements were made at NASA Lewis Research Center on a spur gear test apparatus. The measurements were obtained with the Robotic Acoustic Intensity Measurement System developed by Cleveland State University. This system provided dense spatial positioning, and was calibrated against a high quality acoustic intensity system. The measured gear noise compared gearsets having two different tooth profiles. The tests evaluated the sound field of the different gears for two speeds and three loads. The experimental results showed that gear tooth profile had a major effect on measured noise. Load and speed were found to have an effect on …