TY - JOUR
TI - Shear induced diffusive mixing in simulations of dense Couette flow of rough, inelastic hard spheres
AU - Zamankhan, Piroz
AU - Tafreshi, Hooman Vahedi
AU - Polashenski, William, Jr.
AU - Sarkomaa, Pertti
AU - Hyndman, Caroline L.
T2 - The Journal of Chemical Physics
AB - Large-scale numerical simulations of a system of inelastic, rough, hard spheres of volume fraction φs=0.565, which are initially distributed randomly in a Couette geometry, show clear evidence of the movement of the particles in directions transverse to the bulk motion. This behavior of the aforementioned system, which has been considered as a model for a granular fluid, is consistent with recent experimental observations [Hsiau and Hunt, J. Fluid Mech. 251, 299 (1993)]. Based on the results obtained, there are indications that a bounded rapid granular flow could be a diffusive system at volume fractions even higher than 0.56. This finding contradicts earlier computer experiments [Campbell, J. Fluid Mech. 348, 85 (1997)] which found a rapidly flowing granular material is a diffusive system except at large solids concentrations (i.e., φs>0.56).
DA - 1998/9/15/
PY - 1998/9/15/
DO - 10.1063/1.477076
VL - 109
IS - 11
SP - 4487-4491
J2 - The Journal of Chemical Physics
LA - en
OP -
SN - 0021-9606 1089-7690
UR - http://dx.doi.org/10.1063/1.477076
DB - Crossref
ER -
TY - JOUR
TI - Shear-induced particle diffusion in inelastic hard sphere fluids
AU - Zamankhan, Piroz
AU - Polashenski, William
AU - Tafreshi, Hooman Vahedi
AU - Shakib Manesh, Amir
AU - Sarkomaa, Pertti J.
T2 - Physical Review E
DA - 1998/11/1/
PY - 1998/11/1/
DO - 10.1103/physreve.58.r5237
VL - 58
IS - 5
SP - R5237–R5240
SN - 1063-651X 1095-3787
UR - http://dx.doi.org/10.1103/physreve.58.r5237
ER -
TY - JOUR
TI - Bond-orientational order in sheared dense flows of inelastic hard spheres
T2 - Applied Physics Letters
AB - Three-dimensional bond-orientational order is studied using computer simulations with 4296 hard, monodisperse inelastic spheres flowing in a Couette geometry at a high shear rate. At an average volume fraction close to 0.6, a state with extended correlations in the orientations of particle clusters starts to develop for rough particles after sufficiently long run times. However, no clear evidence of crystallization is found in the system. Further tests of a sheared system comprised of smooth, inelastic spheres reveal crystallization consistent with the previous experimental observations.
DA - 1998///
PY - 1998///
DO - 10.1063/1.121896
VL - 73
IS - 4
SP - 450-452
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0010233091&partnerID=MN8TOARS
ER -
TY - CONF
TI - Computer Modeling of Fabric Drape
AU - Eischen, J.W.
T2 - 35th Annual Society of Engineering Science Conference
C2 - 1998///
C3 - Proceedings of the 35th Annual Society of Engineering Science Conference
CY - Pullman, WA
DA - 1998///
PY - 1998///
ER -
TY - CONF
TI - Drape Modeling of Cloth
AU - Eischen, J.W.
T2 - 1998 SIGGRAPH Computer Graphics Conference
C2 - 1998///
C3 - Course 31- Cloth and Clothing in Computer Graphics
DA - 1998///
PY - 1998///
ER -
TY - CONF
TI - Discontinuous feedback control of a planar rigid body with an unactuated degree of freedom
AU - Reyhanoglu, M.
AU - Cho, Sangbum
AU - McClamroch, N.H.
AU - Kolmanovsky, I.
T2 - 37th IEEE Conference on Decision and Control
AB - We study the problem of controlling a specific mechanical system consisting of a rigid base body with an unactuated internal degree of freedom. The key assumptions are that the translational and rotational motion of the base body can be completely controlled by external forces and moments, while the internal degree of freedom is unactuated. It was shown in our previous work (1998) that although the system is not asymptotically stabilizable to a given configuration using a time-invariant continuous feedback, it is strongly accessible and small-time locally controllable at any equilibrium. We construct a time-invariant discontinuous feedback law to control the system to the desired configuration with exponential convergence rates. A simulation example is included to demonstrate the results.
C2 - 1998/11/28/
C3 - Proceedings of the 37th IEEE Conference on Decision and Control (Cat. No.98CH36171)
CY - Tampa, FL
DA - 1998/11/28/
PY - 1998/12/18/
DO - 10.1109/cdc.1998.760714
PB - IEEE
SN - 0780343948
UR - http://dx.doi.org/10.1109/cdc.1998.760714
ER -
TY - CONF
TI - Control problems for planar motion of a rigid body with an unactuated internal degree of freedom
AU - McClamroch, N.H.
AU - Rui, Chunlei
AU - Kolmanovsky, I.
AU - Cho, Sangbum
AU - Reyhanoglu, M.
T2 - Proceedings of the 1998 American Control Conference (ACC)
AB - We study control problems for a specific mechanical system consisting of a rigid base body with an unactuated internal degree of freedom. The key assumptions are that the translational and rotational motion of the base body can be completely controlled by external forces and moments, while the internal degree of freedom is unactuated. This specific example is representative of a class of underactuated mechanical control systems that are not linearly controllable. This class of control problems presents major theoretical and practical difficulties, and such models do arise in important terrestrial and spacecraft applications. Our focus in this paper is on the simplest mechanical example in this class; it illustrates important features and difficulties associated with the class of such problems.
C2 - 1998///
C3 - Proceedings of the 1998 American Control Conference. ACC (IEEE Cat. No.98CH36207)
DA - 1998///
DO - 10.1109/acc.1998.694665
PB - IEEE
SN - 0780345304
UR - http://dx.doi.org/10.1109/acc.1998.694665
DB - Crossref
ER -
TY - JOUR
TI - Regulation and tracking of the nonholonomic double integrator: A field-oriented control approach
AU - Escobar, G.
AU - Ortega, R.
AU - Reyhanoglu, M.
T2 - Automatica
AB - In this paper we show how a slight modification to the well-known field-oriented control of induction motors allows us to provide simple solutions to the problems of global regulation and tracking for the nonholonomic double integrator. Two controllers are proposed, one motivated by the well-known direct field-oriented motor control, which is a simple continuous static-state feedback that guarantees exponential convergence for all initial conditions in R3 — {x2 = x2 = 0}. To overcome the latter restriction we add a dynamic extension to transfer this (initial conditions) singularity to the controller state, hence making the stability global. This controller is a direct outgrowth of indirect field oriented motor control. In view of the well-known Brockett's condition we obviously do not ensure Lyapunov stability.
DA - 1998/1//
PY - 1998/1//
DO - 10.1016/s0005-1098(97)00155-6
VL - 34
IS - 1
SP - 125-131
J2 - Automatica
LA - en
OP -
SN - 0005-1098
UR - http://dx.doi.org/10.1016/s0005-1098(97)00155-6
DB - Crossref
KW - nonlinear systems
KW - nonholonomic systems
KW - induction motor
ER -
TY - CHAP
TI - THE NUMERICAL SIMULATION OF STRONGLY UNSTEADY FLOW WITH HUNDREDS OF MOVING BODIES
AU - Löhner, Rainald
AU - Baum, Joseph D.
AU - Yang, Chi
AU - Luo, Hong
T2 - Computational Fluid Dynamics Review 1998
PY - 1998/11//
DO - 10.1142/9789812812957_0056
SP - 1027-1033
OP -
PB - WORLD SCIENTIFIC
SN - 9789810235642 9789812812957
UR - http://dx.doi.org/10.1142/9789812812957_0056
DB - Crossref
ER -
TY - JOUR
TI - Analytical Criterion for Chaotic Dynamics in Flexible Satellites with Nonlinear Controller Damping
AU - Gray, Gary L.
AU - Mazzoleni, Andre P.
AU - Campbell, David R., III
T2 - Journal of Guidance, Control, and Dynamics
AB - In this work, we study the attitude dynamics of a single body spacecraft that is perturbed by the motion of a small flexible appendage constrained to undergo only torsional vibration. In particular, we are interested in the chaotic dynamics that can occur for certain sets of the physical parameter values of the spacecraft when energy dissipation acts to drive the body from minor to major axis spin. Energy dissipation, which is present in all spacecraft systems and is the mechanism that drives the minor to major axis transition, is implemented by a quantitative energy sink that is modeled with a nonlinear controller. We obtain an analytical test for chaos in terms of satellite parameters by Melnikov's method. This analytical criterion provides a useful design tool to spacecraft engineers who are concerned with avoiding potentially problematic chaotic dynamics in their systems. In addition, we show that a spacecraft with a control system designed to provide energy dissipation can exhibit chaos because of the inherent flexibility of its components.
DA - 1998/7//
PY - 1998/7//
DO - 10.2514/2.4294
VL - 21
IS - 4
SP - 558-565
J2 - Journal of Guidance, Control, and Dynamics
LA - en
OP -
SN - 0731-5090 1533-3884
UR - http://dx.doi.org/10.2514/2.4294
DB - Crossref
ER -
TY - JOUR
TI - Multipoint Inverse Method for Multielement Airfoil Design
AU - Gopalarathnam, Ashok
AU - Selig, Michael S.
T2 - Journal of Aircraft
AB - A multipoint inverse method has been developed for the design of multielement airfoils with desired velocity distributions in incompressible potential flow. The method uses an isolated-airfoil, multipoint, inverse code to generate each element of the multielement airfoil and a two-dimensional panel method to analyze the multielement airfoil. Through Newton iteration, the variables associated with the design of the elements in isolation are adjusted to achieve desired multielement velocity distributions. As the paper demonstrates, changes in the velocity distributions over the elements in isolation result in remarkably similar changes in the velocity distributions over the corresponding elements of the multielement airfoil. This similarity results in two key features of the design method: 1) the use of the isolated airfoil velocity distributions as design variables to achieve desired distributions over the multielement airfoil, and 2) the calculation of the gradient information for the Newton iteration during the design of the isolated airfoils rather than by several panel-method analyses, resulting in substantial savings in computation time
DA - 1998/5//
PY - 1998/5//
DO - 10.2514/2.2337
VL - 35
IS - 3
SP - 398-404
J2 - Journal of Aircraft
LA - en
OP -
SN - 0021-8669 1533-3868
UR - http://dx.doi.org/10.2514/2.2337
DB - Crossref
ER -
TY - JOUR
TI - Structure and propagation of methanol-air triple flames
AU - Echekki, T.
AU - Chen, J.H.
T2 - Combustion and Flame
AB - The structure and propagation for a methanol (CH3OH)–air triple flame are studied using direct numerical simulations (DNS). The methanol (CH3OH)–air triple flame is found to burn with an asymmetric shape due to the different chemical and transport processes characterizing the mixture. The excess fuel, CH3OH, on the rich premixed flame branch is replaced by more stable fuels CO and H2 which burn at the diffusion flame. On the lean premixed flame side, a higher concentration of O2 leaks through to the diffusion flame. The general structure of the triple point features the contribution of both differential diffusion of radicals and heat. A mixture fraction–temperature phase plane description of the triple flame structure is proposed to highlight some interesting features in partially premixed combustion. The effects of differential diffusion at the triple point add to the contribution of hydrodynamic effects in the propagation of the triple flame. Differential diffusion effects are measured using two methods: a direct computation using diffusion velocities and an indirect computation based on the difference between the normalized mixture fractions of C and H. The mixture fraction approach does not clearly identify the effects of differential diffusion, in particular at the curved triple point, because of ambiguities in the contribution of carbon and hydrogen atoms’ carrying species.
DA - 1998///
PY - 1998///
DO - 10.1016/S0010-2180(97)00287-3
VL - 114
IS - 1-2
SP - 231-245
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0032128242&partnerID=MN8TOARS
ER -
TY - JOUR
TI - Statistics of flame displacement speeds from computations of 2-D unsteady methane-air flames
AU - Peters, N.
AU - Terhoeven, P.
AU - Chen, J.H.
AU - Echekki, T.
T2 - Symposium (International) on Combustion
AB - Results of two-dimensional numerical computations of turbulent methane flames using detailed and reduced chemistry are analyzed in the context of a new theory for premixed turbulent combustion. This theory defines the thin reaction zones regine, where the Kolmogorov scale is smaller than the preheat zone thickness but larger than the reaction zone thickness. The two numerical computations considered in this paper fall clearly within this regime. A lean and a stoichiometric flame are considered. The former is characterized by a large ratio of the turbulence intensity to the laminar burning velocity and the latter by a smaller value of that ratio. The displacement speed of the reaction zone relative to the flow is defined as the displacement speed of the isoscalar line at a fuel mass fraction corresponding to 10% of the upstream value. The three different mechanisms that are contributing to the displacement of the reaction zone, namely, normal and tangential diffusion and reaction, are analyzed and their probability density functions are evaluated. Although these contributions fluctuate considerably, the mean value of the overall displacement speed is found to be only around 40% different from the burning velocity of a plane premixed flame at the same equivalence ratio. Furthermore, the contribution of tangential diffusion, which can be expressed as a curvature term, cancels as far as the mean overall displacement speed is concerned, while the contributions of normal diffusion and reaction are large but have opposite signs. These contributions depend implicitly on curvature. This dependence is small for the lean flame but considerable for the stoichiometric flame where it leads to an enhanced diffusivity. This diffusivity is compared to the Markstein diffusivity that describes the equivalent curvanture effect in the corrugated flamelet regime.
DA - 1998///
PY - 1998///
DO - 10.1016/S0082-0784(98)80479-7
VL - 27
IS - 1
SP - 833-839
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0032286618&partnerID=MN8TOARS
ER -
TY - JOUR
TI - A fast, matrix-free implicit method for compressible flows on unstructured grids
AU - Luo, H
AU - Baum, JD
AU - Lohner, R
T2 - JOURNAL OF COMPUTATIONAL PHYSICS
AB - A fast, matrix-free implicit method has been developed to solve the three-dimensional compressible Euler and Navier?Stokes equations on unstructured meshes. An approximate system of linear equations arising from the Newton linearization is solved by the GMRES (generalized minimum residual) algorithm with a LU-SGS (lower?upper symmetric Gauss?Seidel) preconditioner. A remarkable feature of the present GMRES+LU-SGS method is that the storage of the Jacobian matrix can be completely eliminated by approximating the Jacobian with numerical fluxes, resulting in a matrix-free implicit method. The method developed has been used to compute the compressible flows around 3D complex aerodynamic configurations for a wide range of flow conditions, from subsonic to supersonic. The numerical results obtained indicate that the use of the GMRES+LU-SGS method leads to a significant increase in performance over the best current implicit methods, GMRES+ILU and LU-SGS, while maintaining memory requirements similar to its explicit counterpart. An overall speedup factor from eight to more than one order of magnitude for all test cases in comparison with the explicit method is demonstrated.
DA - 1998/11/1/
PY - 1998/11/1/
DO - 10.1006/jcph.1998.6076
VL - 146
IS - 2
SP - 664-690
SN - 0021-9991
ER -
TY - JOUR
TI - Syngas production using superadiabatic combustion of ultra-rich methane-air mixtures
AU - Drayton, M. K.
AU - Saveliev, A. V.
AU - Kennedy, L. A.
AU - Fridman, A. A.
AU - Li, Y.-E.
T2 - Symposium (International) on Combustion
AB - Two common methods for the production of synthesis gas (syngas) are: (1) methane partial oxidation and (2) methane steam re-forming. This paper discusses the experimental results obtained from the partial oxidation of “ultrarich,” (=4), methane-air mixtures in a new type of chemical reactor based on filtration combustion. Experimental results show that the reciprocal flow burner (RFB), due to its high heat recuperation efficiency (approximately 90%), can support self-sustained combustion of ultrarich methane-air mixtures up to an equivalence ratio of 8, well beyond the conventional flammability associated with a methane-air flame in free space. For the range of equivalence ratios (2 Parametric studies demonstrate that the maximum temperature in the combustion zone, which varies from 1100 to 1400°C, is a function of the equivalence ratio, filtration velocity, reactor pressure, and porous body diameter. Kinetic simulations reveal that methane partial oxidation occurs in a two-stage process: (1) ignition, a fast process that accounts for approximately 60% of the total hydrogen conversion relative to thermodynamic equilibrium and (2) steam reformation, a slow process where the remaining conversion of hydrogen occurs when water reacts with unburned methane.
DA - 1998///
PY - 1998///
DO - 10.1016/s0082-0784(98)80541-9
VL - 27
IS - 1
SP - 1361-1367
ER -
TY - JOUR
TI - Employing plasma as catalyst in hydrogen production
AU - Mutaf-Yardimci, O
AU - Saveliev, AV
AU - Fridman, AA
AU - Kennedy, LA
T2 - INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
AB - A novel approach in hydrogen production via reforming of hydrocarbons that will use catalytic properties of non-equilibrium plasma gas discharge is presented. CH4/CO2 mixtures are heated to a temperature of 900°C, so that mixture will have approximately 80% of the energy required for thermal reforming. Preheated mixtures are then processed in a Pulsed Corona Discharge type plasma source and the catalytic effect of a non-equilibrium plasma is observed for promotion of hydrogen generation.
DA - 1998/12//
PY - 1998/12//
DO - 10.1016/s0360-3199(98)00005-6
VL - 23
IS - 12
SP - 1109-1111
SN - 0360-3199
ER -
TY - BOOK
TI - Thermodynamics: an engineering approach. (3rd ed.)
AU - Cengel, Y. A.
AU - Boles, M. A.
CN - TJ265 .C43 1998
DA - 1998///
PY - 1998///
PB - Boston: McGraw-Hill
SN - 0070119279
ER -
TY - JOUR
TI - Analytical study of fluid flow and heat transfer during forced convection in a composite channel partly filled with a Brinkman-Forchheimer porous medium
AU - Kuznetsov, AV
T2 - FLOW TURBULENCE AND COMBUSTION
DA - 1998///
PY - 1998///
DO - 10.1023/A:1009998703180
VL - 60
IS - 2
SP - 173-192
SN - 1386-6184
KW - porous medium
KW - forced convection
KW - Brinkman-Forchheimer-extended Darcy equation
KW - interface region
ER -
TY - JOUR
TI - Transition closure model for predicting transition onset
AU - Warren, ES
AU - Hassan, HA
T2 - JOURNAL OF AIRCRAFT
DA - 1998///
PY - 1998///
DO - 10.2514/2.2368
VL - 35
IS - 5
SP - 769-775
SN - 0021-8669
ER -
TY - JOUR
TI - Finite element modeling of machining: From proof-of-concept to engineering applications
AU - Athavale, SM
AU - Strenkowski, JS
T2 - MACHINING SCIENCE AND TECHNOLOGY
AB - ABSTRACT For the past fifty years researchers have developed various machining models to improve cutting performance. Several approaches have been taken including analytical techniques, slipline field solutions, empirical approaches and finite element techniques. Of these, the finite element approach provides the most detailed information on chip formation and chip interaction with the cutting tool. Finite element models have been developed for calculating the stress, strain, strain-rate, and temperature distributions in both the chip and the workpiece. In addition, tool temperatures, machining forces and cutting power requirements can be determined. This information is extremely, useful for developing more fundamental understanding of complex machining problems. This paper presents a critique of finite element approaches used for simulating machining processes. Several applications of the finite element technique for simulating various machining problems are also reviewed. A new application for determining diffusion wear rates in cutting tools is described, and future directions for finite element modeling of machining processes are discussed.
DA - 1998///
PY - 1998///
DO - 10.1080/10940349808945674
VL - 2
IS - 2
SP - 317-342
SN - 1532-2483
ER -
TY - JOUR
TI - Two-equation turbulence closure model for wall bounded and free shear flows
AU - Robinson, DF
AU - Hassan, HA
T2 - AIAA JOURNAL
AB - The κ-ζ model can be used for both wall bounded and free shear flows using one set of model constants
DA - 1998/1//
PY - 1998/1//
DO - 10.2514/2.360
VL - 36
IS - 1
SP - 109-111
SN - 0001-1452
ER -
TY - JOUR
TI - Sliding-mode control of a nonlinear-input system: Application to a magnetically levitated fast-tool servo
AU - Gutierrez, HM
AU - Po, PI
T2 - IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS
AB - Magnetic servo levitation (MSL) is currently being investigated as an alternative to drive fast-tool servo systems that could overcome the range limitations inherent to piezoelectric driven devices while operating over a wide bandwidth. To control such systems, a feedback-linearized controller coupled with a Kalman filter has been previously described. Performance limitations that degrade tracking accuracy suggest the use of a more robust controller design approach, such as sliding-mode control. Current literature on sliding mode deals almost exclusively with systems that are affine on the input, while the magnetic fast-tool servo is nonlinear on it when the control action is current command. This paper discusses a sliding mode-based controller that overcomes the aforementioned problem by defining a modified sliding condition to calculate control action. Experimental results demonstrate the feasibility of achieving long-range fast tracking with magnetically levitated devices by using sliding-mode control.
DA - 1998/12//
PY - 1998/12//
DO - 10.1109/41.735336
VL - 45
IS - 6
SP - 921-927
SN - 0278-0046
KW - fast-tool servo systems
KW - magnetic servo levitation
KW - nonaffine systems
KW - sliding-mode control
ER -
TY - JOUR
TI - Simulation of particle-hemodynamics in a partially occluded artery segment with implications to the initiation of microemboli and secondary stenoses
AU - Buchanan, , JR
AU - Kleinstreuer, C
T2 - JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME
AB - Computational results of laminar incompressible blood-particle flow analyses in an axisymmetric artery segment with a smooth local area constriction of 75 percent have been presented. The flow input waveform was sinusoidal with a nonzero average. The non-Newtonian behavior of blood was simulated with a modified Quemada model, platelet concentrations were calculated with a drift-flux model, and monocyte trajectories were described and compared for both Newtonian and Quemada rheologies. Indicators of “disturbed flow” included the time-averaged wall shear stress (WSS), the oscillatory shear index (OSI), and the wall shear stress gradient (WSSG). Implications of the vortical flow patterns behind the primary stenosis to the formation of microemboli and downstream stenoses are as follows. Elevated platelet concentrations due to accumulation in recirculation zones mixed with thrombin and ADP complexes assumed to be released upstream in high wall shear stress regions, could form microemboli, which are convected downstream. Distinct near-wall vortices causing a local increase in the WSSG and OSI as well as blood-particle entrainment with possible wall deposition, indicate sites susceptible to the onset of an additional stenosis proximal to the initial geometric disturbance.
DA - 1998/8//
PY - 1998/8//
DO - 10.1115/1.2798013
VL - 120
IS - 4
SP - 446-454
SN - 1528-8951
ER -
TY - JOUR
TI - Signal response of elastically coated plates
AU - Keltie, RF
T2 - JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
AB - An analytical model of a compliant elastic coating attached to a submerged thin plate has been developed. A plane acoustic wave, representing the signal, is incident from the water on to the elastic coating. The normal and tangential velocity components induced in the coating by the acoustic wave are calculated. The effects of incidence angle, frequency, location throughout the coating, and coating properties on the signal response velocity components are evaluated. Many details of the coating velocity components are explained based on simple uncoupled waveguide characteristics of the coating. In general, the normal velocity components are several tens of decibels higher in amplitude than the tangential velocity components. It was shown, however, that the tangential velocity component could be increased by an average amount of about 20 dB, without serious degradation of the normal component, by altering the coating properties. In particular, combinations of high longitudinal wave speed and low shear wave speed were found to be advantageous.
DA - 1998/4//
PY - 1998/4//
DO - 10.1121/1.421336
VL - 103
IS - 4
SP - 1855-1863
SN - 0001-4966
ER -
TY - JOUR
TI - Role of boundary conditions in Monte Carlo simulation of microelectromechanical systems
AU - Nance, RP
AU - Hash, DB
AU - Hassan, HA
T2 - JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER
DA - 1998///
PY - 1998///
DO - 10.2514/2.6358
VL - 12
IS - 3
SP - 447-449
SN - 0887-8722
ER -
TY - JOUR
TI - Experimental study of a precision, hydrodynamic wheel spindle for submicron cylindrical grinding
AU - Tu, JF
AU - Corless, M
AU - Gehrich, MJ
AU - Shih, AJ
T2 - PRECISION ENGINEERING-JOURNAL OF THE AMERICAN SOCIETY FOR PRECISION ENGINEERING
AB - Abstract Hydrodynamic journal bearings have been widely used in various types of rotating machinery, ranging from heavy duty, high-impact applications, such as the crank shaft of an internal combustion engine and turbine rotor, to high-precision, light load applications, such as precision spindles in cylindrical grinding machines. Although extensive theoretical and experimental results have been presented for hydrodynamic bearings, the available literature seems to be limited for precision hydrodynamic bearing spindles. In this study, practical methods have been developed to quantify the performance of a hydrodynamic wheel spindle operating in the horizontal mode to produce precision parts with submicron roundness tolerance and very fine surface finish. These methods can easily and cost effectively be implemented on various machines in an actual production environment for effective predictive maintenance. The main experimental results show that the long-term drift of the spindle at steady state is less than 1 μm vertically and 0.2 μm horizontally, and the radial error motion of the spindle based on unfiltered data is less than 1.6 μm for all the speeds tested. It is also found that the shaft center position (vertical lift and horizontal shift) at the cold condition is substantially different from that in the steady-state warm condition. From the results, an optimal spindle speed is recommended.
DA - 1998/1//
PY - 1998/1//
DO - 10.1016/S0141-6359(98)00003-8
VL - 22
IS - 1
SP - 43-57
SN - 0141-6359
KW - hydrodynamic bearing
KW - spindle
KW - radial error motion
KW - cylindrical grinding roundness
KW - radial error motion
KW - whirl
KW - spindle rotating accuracy
ER -
TY - JOUR
TI - An empirical tool force model for precision machining
AU - Arcona, C
AU - Dow, TA
T2 - JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME
AB - The accuracy of precision machining operations could be improved through tool force feedback. Tool force is ideally suited for use in a control algorithm because it contains information on the instantaneous depth of cut, feed rate and condition of the tool. A tool force model that could form the basis of this new control technique has been developed. By measuring the shear angle from micrographs of chip cross sections, equations for the forces due to chip formation and the friction between the chip and the tool have been written. Furthermore, the effects of elastic deformation of the workpiece (spring back) on chip formation and the measured forces, which can be significant in precision machining, have been included in the model. Machining experiments were conducted with a 0 deg rake diamond tool and four metals that are commonly diamond turned. For machining with newly lapped as well as worn tools, the calculated forces were in excellent agreement with the measured values for the array of workpiece materials.
DA - 1998/11//
PY - 1998/11//
DO - 10.1115/1.2830209
VL - 120
IS - 4
SP - 700-707
SN - 1528-8935
ER -
TY - JOUR
TI - Alternative to the e(n) method for determining onset of transition
AU - Warren, EW
AU - Hassan, HA
T2 - AIAA JOURNAL
AB - We employ a two-equation model similar to that employed in turbulent calculations. It is based on the premise that, if a flow quantity can be written as the sum of a mean and a fluctuating quantity, then the exact equations that govern the fluctuations and their averages are identical irrespective of the nature of the oscillations, i.e., laminar, transitional, or turbulent
DA - 1998/1//
PY - 1998/1//
DO - 10.2514/2.361
VL - 36
IS - 1
SP - 111-113
SN - 0001-1452
ER -
TY - JOUR
TI - A discussion of modal uncoupling and an approximate closed-form solution for weakly coupled systems with application to acoustics
AU - Franzoni, LP
AU - Bliss, DB
T2 - JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
AB - Modal analysis is often used to solve problems in acoustics, leading to a system of coupled equations for the modal amplitudes. A common practice in analytical work utilizing modal analysis has been to assume that weak modal coupling is negligible, thereby enabling the modal coefficients to be solved independently in closed form. The validity of this assumption, as well as the order of the error from neglecting modal coupling, is discussed. It is possible to incorporate the principal effects of weak modal coupling in a very simple way without solving the fully coupled system. An approximate closed-form solution for weakly coupled systems of equations is developed. The procedure gives insight into the errors incurred when coupling is neglected, and shows that these errors may be unacceptably large in systems of practical interest. A model problem involving a pipe with an impedance boundary condition is solved when the one-dimensional sound field is harmonically driven, and when it undergoes reverberant decay from initial conditions. The approximate solution derived in this paper is compared with results for the fully coupled and fully uncoupled equivalent problems. The approximation works well even for systems where the coupling is fairly strong. The results show that modal coupling must be included, at least approximately, if certain salient features of the sound field, such as intensity flow and detailed reverberant structure, are to be predicted correctly.
DA - 1998/4//
PY - 1998/4//
DO - 10.1121/1.421344
VL - 103
IS - 4
SP - 1923-1932
SN - 0001-4966
ER -
TY - JOUR
TI - Three-dimensional wave propagation in composite cylindrical shells
AU - Yuan, FG
AU - Hsieh, CC
T2 - COMPOSITE STRUCTURES
AB - An exact solution of free harmonic wave propagation in a composite laminated cylindrical shell is presented within the framework of the theory of three-dimensional cylindrically anisotropic elasticity. The dispersion equation governing these motions is established through a helical solution form in conjunction with a Frobenius power series method. Degenerate cases of infinite wavelength, axisymmetric waves, and of orthotropic shells are derived and discussed. Analytical results are presented for a variety of cases and are compared with those obtained from a Flügge shell theory.
DA - 1998/6//
PY - 1998/6//
DO - 10.1016/S0263-8223(98)00063-4
VL - 42
IS - 2
SP - 153-167
SN - 0263-8223
ER -
TY - JOUR
TI - Special issue: Deformation and failure modes in multiphase materials
AU - Zikry, M. A.
AU - Garmestani, H.
T2 - International Journal of Plasticity
DA - 1998///
PY - 1998///
VL - 14
IS - 8
SP - 671
ER -
TY - JOUR
TI - Parametric modeling and control of a long-range actuator using magnetic servo levitation
AU - Gutierrez, HM
AU - Ro, PI
T2 - IEEE TRANSACTIONS ON MAGNETICS
AB - A mechatronic device based on magnetic servo levitation (MSL) is proposed for long range and wide bandwidth actuation. The force capability of this type of actuator can be significantly larger than a linear motor or voice-coil actuator of similar dimensions. A novel parametric model of the electromagneto-mechanical coupled system has been developed to describe its behavior over a large range of motion and frequency, as opposed to more conventional attractive force small-perturbation models. It also provides a convenient way of devising a feedback linearizing control scheme that eliminates the need for high biasing currents present in most magnetic bearing systems. This paper presents a feedback-linearized controller coupled with a Kalman filter as a first approach to solve the tracking problem for such an actuator. Good tracking performance have been found both in simulation and experiments.
DA - 1998/9//
PY - 1998/9//
DO - 10.1109/20.718530
VL - 34
IS - 5
SP - 3689-3695
SN - 0018-9464
KW - feedback linearization
KW - magnetic servo levitation
KW - parametric modeling
ER -
TY - JOUR
TI - Further development of the k-zeta (enstrophy) turbulence closure model
AU - Robinson, DF
AU - Hassan, HA
T2 - AIAA JOURNAL
AB - The k‐‡ model is extended to the study of two-dimensional and three-dimensional separated external e ows where Morkovin’ s hypothesis is expected to hold. The resulting model is free of damping and wall functions and is coordinate independent. Further, all modeled correlations are tensorially consistent and Galilean invariant. Applications include a variety of separated e ows over airfoils and a cylinder/offset e are juncture. Comparisons are made with other turbulence models and experiment. In general, good agreement with experiment is indicated. The results demonstrate that it is possible to develop a two-equation turbulence model that is capable of predicting separated e ows without sacrie cing performance for free shear layers.
DA - 1998/10//
PY - 1998/10//
DO - 10.2514/2.298
VL - 36
IS - 10
SP - 1825-1833
SN - 0001-1452
ER -
TY - JOUR
TI - Concerning time and length scale estimates made from burst-mode LDA autocorrelation measurements
AU - Benedict, LH
AU - Gould, RD
T2 - EXPERIMENTS IN FLUIDS
DA - 1998/3//
PY - 1998/3//
DO - 10.1007/s003480050171
VL - 24
IS - 3
SP - 246-253
SN - 0723-4864
ER -
TY - CONF
TI - Vitreous bond CBN wheel for high speed grinding of ceramic and M2 steel
AU - Shih, A. J.
AU - Yonushonis, T. M.
AU - Grant, M. B.
AU - Morris, T. O.
AU - McSpadden, S. B.
C2 - 1998///
C3 - Transaction of 26th NAMRC (North American Manufacturing Research Conference), 1998
DA - 1998///
SP - 195-200
M1 - 1998
ER -
TY - JOUR
TI - On control and optimization of elastic multilink mechanisms
AU - Wang, HL
AU - Eischen, JW
AU - Silverberg, LM
T2 - COMPUTERS & STRUCTURES
AB - Abstract This paper presents a simple method for control of nonlinear elastic multilink mechanisms. The associated control law consists of open and closed loop components. The open loop component produces the desired overall rigid body motion, while the closed loop component suppresses the elastic motion relative to rigid body motion. Both the control law and the structural dynamics are referred to an inertial coordinate system. As a consequence, the control forces and control moments are easily simulated in a dynamic finite element analysis program. A series of numerical simulations illustrate the generality of this new method.
DA - 1998/6//
PY - 1998/6//
DO - 10.1016/s0045-7949(98)00060-1
VL - 67
IS - 6
SP - 483-502
SN - 0045-7949
ER -
TY - JOUR
TI - Intergranular and transgranular crack growth at triple junction boundaries in ordered intermetallics
AU - Kameda, T
AU - Zikry, MA
T2 - INTERNATIONAL JOURNAL OF PLASTICITY
AB - Abstract Coincident site-lattice (CSL) and random grain boundaries (GBs) effects on intergranular and transgranular crack propagation paths in ordered intermetallics that are subjected to high rates of strain are investigated. A three dimensional dislocation density based multiple slip crystalline formulation and computational scheme are used for a detailed understanding and accurate characterization of interrelated deformation and failure mechanisms that can occur due to the generation, trapping, interaction, and annihilation of mobile and immobile dislocation densities that are generally associated with finite strain high strain-rate plasticity in L1 2 ordered intermetallics. Results from this study indicate that intergranular crack growth is along the GBs, normal to the stress-axis, and is due to the dominance of normal stresses in the crack-tip region. Transgranular crack growth is along slip-planes, and is due to the dominance of shear stresses in the crack-tip region.
DA - 1998///
PY - 1998///
DO - 10.1016/S0749-6419(98)00017-5
VL - 14
IS - 8
SP - 689-702
SN - 0749-6419
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0032309910&partnerID=MN8TOARS
KW - crack propagation
KW - intermetallics
ER -
TY - JOUR
TI - Inelastic three dimensional high strain-rate dislocation density based analysis of grain-boundary effects and failure modes in ordered intermetallics
AU - Zikry, MA
AU - Kameda, T
T2 - MECHANICS OF MATERIALS
AB - A three dimensional dislocation density based multiple slip crystalline formulation and computational scheme are introduced for a detailed understanding and accurate characterization of interrelated failure mechanisms that may occur on different length scales in intermetallics subjected to high strain-rates. This constitutive framework accounts for the generation, trapping, interaction, and annihilation of mobile and immobile dislocations densities that are generally associated with finite strain high strain-rate plasticity in Ll 2 ordered intermetallics. Coincident site-lattice (CSL) and random grain boundaries (GBs) effects on intergranular and transgranular failure at triple junctions are investigated. Results from this study indicate that intergranular cracks can nucleate due to dislocation pile-ups along the GBs, and that transgranular failure occurs on slip-planes that intersect the GB.
DA - 1998/5//
PY - 1998/5//
DO - 10.1016/S0167-6636(97)00026-4
VL - 28
IS - 1-4
SP - 93-102
SN - 0167-6636
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0032068356&partnerID=MN8TOARS
ER -
TY - CONF
TI - High speed and high material removal rate grinding of ceramics using the vitreous bond CBN wheel
AU - Shih, A. J.
AU - Yonushonis, T. M.
AU - Grant, M. B.
AU - Morris, T. O.
AU - McSpadden, S. B.
C2 - 1998///
C3 - ASPE 13th annual meeting, St. Louis, MO, Oct. 25-30, 1998
DA - 1998///
SP - 25-30
M1 - 1998
ER -
TY - JOUR
TI - Analytical solution to flux enhancement in laminar concentrically stratified pipe flow of Bingham and Newtonian fluids
AU - Buchanan, CD
AU - Kleinstreuer, C
AU - Longest, PW
T2 - JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME
DA - 1998/9//
PY - 1998/9//
DO - 10.1115/1.2820711
VL - 120
IS - 3
SP - 629-631
SN - 0098-2202
ER -
TY - JOUR
TI - A study of solutions for the anisotropic plate subjected to a concentrated force
AU - LaMattina, B
AU - Klang, EC
AU - Eischen, JW
T2 - JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME
AB - One of the objectives of this brief note is to present all three solutions and show how they are applied to the boundary element method formulation. Secondly, differences between these solutions are illustrated and discussed. The implications of these discrepancies is examined for the infinite plate as well as typical boundary value problem
DA - 1998/3//
PY - 1998/3//
DO - 10.1115/1.2789039
VL - 65
IS - 1
SP - 273-276
SN - 0021-8936
ER -
TY - JOUR
TI - Nonlinear optimization-based motion planning of nonholonomic systems using an iterative algorithm
AU - Yih, C. C.
AU - Ro, P. I.
T2 - Intelligent Automation and Soft Computing
AB - ABSTRACTA nonlinear optimization-based scheme is developed for the motion planning of nonholonomic systems. By specifying the final states constraints and using the performance criteria involving the control energy, the motion planning of nonholonomic systems can be recast as a nonlinear optimization problem which is to find suitable control inputs for steering the system along a feasible path from an initial state to a final state. An iterative algorithm is proposed to solve for a feasible path satisfying nonholonomic constraints and necessary optimality conditions. First, multi-point shooting is used to convert the motion planning problem into the problem of finding the solution of nonlinear equations. Modified Newton's method with line search is then used to ensure the global convergence of the numerical algorithm. The proposed scheme is applied to an one-leg hopping robot and a two-wheeled mobile robot. The results of numerical simulation clearly demonstrate the effectiveness of the proposed motion pl...
DA - 1998///
PY - 1998///
DO - 10.1080/10798587.1998.10750733
VL - 4
IS - 3
SP - 227-239
ER -
TY - JOUR
TI - Wear characteristics of a woodworking knife with a vanadium carbide coating only on the clearance surface (back surface)
AU - Kato, C
AU - Bailey, JA
T2 - ADVANCED CERAMIC TOOLS FOR MACHINING APPLICATION - III
DA - 1998///
PY - 1998///
DO - 10.4028/www.scientific.net/kem.138-140.479
VL - 138-1
SP - 479-520
SN - 1013-9826
KW - wood cutting
KW - orthogonal cutting
KW - up milling
KW - vanadium carbide coated tool
KW - chromium coated tool
KW - self-sharpening
ER -
TY - JOUR
TI - Stresses around the crack tip due to electric current and self-induced magnetic field
AU - Cai, GX
AU - Yuan, FG
T2 - ADVANCES IN ENGINEERING SOFTWARE
AB - Abstract Mode-I stress distributions around the crack tip in a thin conducting plate under a uniform electric current flow are investigated. The stresses are generated by the electromagnetic forces, which in turn are caused by the interplay between electric current and the self-induced magnetic field. The current flow is disturbed by the presence of the crack and so is the magnetic field, which is induced by the electric current. A numerical analysis procedure is developed to analyze the coupled problem of magnetic field and stress distributions, and an algorithm based on the Biot–Savart integral is proposed to reduce the calculation of magnetic field in the thin plate to a two-dimensional analysis problem. The electric current, magnetic flux, and stress fields show the −1/2 singularity at the crack tip and the normalized mode-I stress intensity factors are determined numerically.
DA - 1998///
PY - 1998///
DO - 10.1016/S0965-9978(97)00078-1
VL - 29
IS - 3-6
SP - 297-306
SN - 0965-9978
KW - crack tip
KW - stress
KW - self-induced magnetic field
ER -
TY - JOUR
TI - Low-diffusion flux-splitting methods for flows at all speeds
AU - Edwards, , JR
AU - Liou, MS
T2 - AIAA JOURNAL
AB - Methods for extending the advective upwind splitting method (AUSM) family of low-diffusion flux-splitting schemes to operate effectively at all flow speeds are developed. The extensions developed are designed for use with time-derivative preconditioning and are based on the idea that the speed of sound should cease to be an important scaling parameter for the diffusive contributions to the interface flux as the Mach number becomes small. Using this criterion, alternative definitions for the interface Mach numbers are developed, and methods for ensuring pressure-velocity coupling at low speeds are formulated. Results are presented for inviscid flows through a channel at various Mach numbers, developing viscous flow in a two-dimensional duct, driven-cavity flows at various Mach and Reynolds numbers, flow over a backward-facing step, and hydrogen-nitrogen mixing layers
DA - 1998/9//
PY - 1998/9//
DO - 10.2514/2.587
VL - 36
IS - 9
SP - 1610-1617
SN - 0001-1452
ER -
TY - JOUR
TI - Development of a new standard laboratory protocol for estimating the field attenuation of hearing protection devices. Part III. The validity of using subject-fit data
AU - Berger, EH
AU - Franks, , JR
AU - Behar, A
AU - Casali, JG
AU - Dixon-Ernst, C
AU - Kieper, RW
AU - Merry, CJ
AU - Mozo, BT
AU - Nixon, CW
AU - Ohlin, D
AU - Royster, JD
AU - Royster, LH
T2 - JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
AB - The mandate of ASA Working Group S12/WG11 has been to develop "laboratory and/or field procedure(s) that yield useful estimates of field performance" of hearing protection devices (HPDs). A real-ear attenuation at threshold procedure was selected, devised, tested via an interlaboratory study, and incorporated into a draft standard that was approved in 1997 [J. D. Royster et at., "Development of a new standard laboratory protocol for estimating the field attenuation of hearing protection devices. Part I. Research of Working Group 11, Accredited Standards Committee S12, Noise," J. Acoust. Soc. Am. 99, 1506-1526 (1996); ANSI S12.6-1997, "American National Standard Methods for Measuring Real-Ear Attenuation of Hearing Protectors" (American National Standards Institute, New York, 1997)]. The real-world estimation procedure utilizes a subject-fit methodology with listeners who are audiometrically proficient, but inexperienced in the use of HPDs. A key factor in the decision to utilize the subject-fit method was an evaluation of the representativeness of the laboratory data vis-à-vis attenuation values achieved by workers in practice. Twenty-two field studies were reviewed to develop a data base for comparison purposes. Results indicated that laboratory subject-fit attenuation values were typically equivalent to or greater than the field attenuation values, and yielded a better estimate of those values than did experimenter-fit or experimenter-supervised fit types of results. Recent data which are discussed in the paper, but which were not available at the time of the original analyses, confirm the findings.
DA - 1998/2//
PY - 1998/2//
DO - 10.1121/1.423236
VL - 103
IS - 2
SP - 665-672
SN - 1520-8524
ER -
TY - JOUR
TI - Analytical investigation of heat transfer in Couette flow through a porous medium utilizing the Brinkman-Forchheimer-extended Darcy model
AU - Kuznetsov, AV
T2 - ACTA MECHANICA
DA - 1998///
PY - 1998///
DO - 10.1007/BF01379647
VL - 129
IS - 1-2
SP - 13-24
SN - 0001-5970
ER -
TY - JOUR
TI - Analytical investigation of Couette flow in a composite channel partially filled with a porous medium and partially with a clear fluid
AU - Kuznetsov, AV
T2 - INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
DA - 1998/8//
PY - 1998/8//
DO - 10.1016/S0017-9310(97)00296-2
VL - 41
IS - 16
SP - 2556-2560
SN - 0017-9310
ER -
TY - JOUR
TI - Velocity and thermal structure, and strain-induced extinction of 14 to 100% hydrogen-air counterflow diffusion flames
AU - Pellett, GL
AU - Isaac, KM
AU - Humphreys, WM
AU - Gartrell, LR
AU - Roberts, WL
AU - Dancey, CL
AU - Northam, GB
T2 - COMBUSTION AND FLAME
AB - Extensive results from axisymmetric convergent-nozzle and straight-tube opposed jet burners (OJBs) characterized strain-induced extinction of unanchored (free-floating), laminar H 2 /N 2 -air flames. Parameters included (a) plug-flow and parabolic input velocity profiles, (b) jet exit diameters ranging 2.7 to 7.2 mm for nozzles and 1.8 to 10 mm for tubes, (c) various relative jet gaps, and (d) 14 to 100% H 2 in the fuel jet. Extinction, a sudden rupture (blowoff) of the mostly-airside disk flame, occurred as fuel and air flows were slowly increased and a critical radial strain rate was exceeded. The disk flame was restored at much lower flows, unique to H 2 systems. Focusing schlieren, thermocouple, and airside LDV (and PIV) data confirmed the one-dimensional (I-D) character of nozzle-OJB flow fields; axial widths of velocity- and thermal-layers varied as (input strain rate) −1/2 for both nozzles and tubes. The global approximation of a I-D applied stress rate (ASR), using average air jet velocity divided by exit diameter, enabled high quality correlations of extinction data with varied H 2 concentrations, for both nozzles and tubes. Pre-extinction ASRs for nozzles agreed closely with LDV-measured centerline input strain rates; for tubes, however, an empirical factor of 3 produced close agreement. For methane-air extinction, nozzle-OJB ASRs agreed within 4% of independent nozzle and Tsuji burner results. For extinction of 100% H 2 -air, an ASR of 5670 1/s compared with 7350, 8140, and 8060 from independent 1-D numerical evaluations using potential-flow inputs; for 50 to 14% H 2 inputs, agreement was much closer. The nozzle-ASR/tube-ASR ratio for extinction was ≥3 for <50% H 2 inputs, 2.74 ± 0.03 for 50 to 100% H 2 inputs, and 2.83 for methane-air. Because these ratios exceeded 2.0, which “accounted” for centerline velocity inputs from parabolic profiles, an additional 3/2 radial strain component was apparent and was supported by the axial velocity gradient measurements.
DA - 1998/3//
PY - 1998/3//
DO - 10.1016/S0010-2180(97)00169-7
VL - 112
IS - 4
SP - 575-592
SN - 0010-2180
ER -
TY - JOUR
TI - Shear strength of an adhesively bonded paper-metal interface
AU - Ramasubramanian, M. K.
AU - Crews, W. R.
T2 - Journal of Pulp and Paper Science
DA - 1998///
PY - 1998///
VL - 24
IS - 1
SP - 31-36
ER -
TY - JOUR
TI - Preconditioned multigrid methods for two-dimensional combustion calculations at all speeds
AU - Edwards, , JR
AU - Roy, CJ
T2 - AIAA JOURNAL
AB - The development of an effective implicit integration strategy for two-dimensional (axisymmetric) combustion calculations at all speeds is presented. A time-derivative preconditioning technique is first combined with an implicit line relaxation algorithm to yield an approach capable of removing the acoustic time step restriction at low flow speeds while handling stiff chemical kinetics in a fully implicit fashion. Numerical performance is further improved through the addition of a full multigrid/full approximation storage (FMG-FAS) convergence acceleration strategy. Numerical simulations of a subsonic reacting shear layer (finite rate hydrogen-air chemistry), a subsonic bluff-body stabilized flame (mixing-limited methane-air chemistry), and a supersonic jet diffusion flame (finite rate hydrogen-air chemistry) are presented to test the basic attributes of the algorithm. Comparisons with experimental data are presented for all cases, and a detailed examination of the computational efficiency of the new procedure is conducted. The strengths and weaknesses of multigrid ideas for fully coupled combustion calculations are particularly highlighted.
DA - 1998/2//
PY - 1998/2//
DO - 10.2514/2.7500
VL - 36
IS - 2
SP - 185-192
SN - 0001-1452
ER -
TY - JOUR
TI - The interlaminar Mode I fracture of IM7/LaRC-RP46 composites at high temperatures
AU - Wang, WX
AU - Takao, Y
AU - Yuan, FG
AU - Potter, BD
AU - Pater, RH
T2 - JOURNAL OF COMPOSITE MATERIALS
AB - In this paper, the interlaminar Mode I fracture behavior of IM7/LaRC-RP46 composite laminate at elevated temperatures was investigated by DCB (double cantilever beam) static fracture testing. Straight-sided DCB specimens were made from unidirectional laminates and tested at three high temperature levels of 232°C (450°F), 288°C (550°F) and 343°C (650°F) at five crosshead rates from 0.51 mm/min. (0.00033 in./sec) to 6.1 mm/min. (0.004 in./sec). Unlike the linear load-displacement response observed at room temperature, the load-displacement response at high temperatures behaves nonlinearly.. before reaching the maximum load. Two crack growth regions of slow crack extension and relatively fast crack propagation were observed and the slow crack extension caused the nonlinear load-displacement response. The initial fracture toughness, G IC , decreased slightly, while the propagation value increased by nearly 30% to 100% with increased temperature. The materials exhibited the highest fracture toughness at 288°C among the three different tested temperatures. The complex combination effects of fiber bridging and the change of matrix properties and fiber/matrix interfacial adhesion at elevated temperatures are found to be the major reason resulting in the variation of G IC with temperature. After the temperature increased beyond T g (glass transition temperature). which is approximately 310°C, the propagation fracture toughness decreased drastically and aging effects of the high temperature on the matrix are observed. No significant effects ofcrosshead rate on the G IC were observed in the range ofthe present rates. However, the crosshead rate is found to significantly influenced the crack growth rate.
DA - 1998///
PY - 1998///
DO - 10.1177/002199839803201603
VL - 32
IS - 16
SP - 1508-1526
SN - 0021-9983
KW - IM7/LaRC-RP46 composites
KW - DCB test
KW - interlaminar Mode I fracture toughness
KW - high temperature
KW - crack growth rate
KW - crosshead rate
ER -
TY - JOUR
TI - Rotary truing of vitreous bond diamond grinding wheels using metal bond diamond disks
AU - Shih, AJ
T2 - MACHINING SCIENCE AND TECHNOLOGY
AB - Abstract Experiments on rotary truing of vitreous bond diamond grinding wheels were conducted to investigate the effects of truing speed ratio, type of diamond in the metal bond truing disks (synthetic versus natural), and diamond grit size in the grinding wheel on the wear of truing disk and on the cylindrical grinding of zirconia. Similar to G-ratio, a new parameter called D-ratio is defined to quantify the wear rate of the diamond truing disks. Experimental results show that, under the same truing condition, the truing disk with blocky, low friability synthetic diamond has a higher D-ratio than the truing disk with natural diamond. Diamond wheels trued by the disk with synthetic diamond also generate lower grinding force and rougher surface finish. High truing disk surface speed, 1.8 times higher than the surface speed of the grinding wheel, was tested and did not show any improvement in D-ratio. This study indicates that μm-scale precision form truing of the vitreous bond diamond wheel is difficult du...
DA - 1998///
PY - 1998///
DO - 10.1080/10940349808945656
VL - 2
IS - 1
SP - 13-28
SN - 1091-0344
ER -
TY - JOUR
TI - Mars' atmosphere: A study with microstation network
AU - Marov, M. Y.
AU - Walberg, G. D.
T2 - Life sciences: Exobiology: Proceedings of the F3.3 and F3.5 Symposia of COSPAR Scientific Commission F which was held during the thirty-second COSPAR Scientific Assembly, Nagoya, Japan, 12-19 July, 1998. (Advances in space research; v. 23, no. 2)
DA - 1998///
PY - 1998///
SP - 459-462
ER -
TY - JOUR
TI - An innovative design of a probe-tube attachment for a microphone
AU - Franzoni, LP
AU - Elliott, CM
T2 - JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
AB - Nonintrusive devices are needed to measure sound pressure levels in the mid- to high-frequency range. This need arises due to the small acoustic wavelengths which are present at these frequencies, and the interference caused by conventional microphones which are typically of relatively large diameter. Smaller microphones are less sensitive, and may not be small enough to be useful at very high frequencies or when physical size constraints are limiting. Simple probe attachments have been developed by others to address these problems; however, generally the transfer functions of these devices have possessed undesirable peaks due to the presence of standing waves within the transducers. In this paper, several possible options for making a microphone attachment that will convert a standard 12-in.-diam microphone into a probe-tube are discussed. Recommendations are made with regard to the particular use and ease of construction of the attachment. The new concepts eliminate standing waves, within certain frequency bands that are controlled by the geometry of the attachment, without the addition of damping material in the sound path.
DA - 1998/11//
PY - 1998/11//
DO - 10.1121/1.423873
VL - 104
IS - 5
SP - 2903-2910
SN - 0001-4966
ER -
TY - JOUR
TI - Three dimensional dislocation-based crystalline constitutive formulation for ordered intermetallics
AU - Kameda, T
AU - Zikry, MA
T2 - SCRIPTA MATERIALIA
AB - A three dimensional multiple-slip crystal plasticity constitutive formulation that is coupled to the temperature dependent evolution of mobile and immobile dislocation densities has been developed for a more detailed understanding of the deformation modes of ordered intermetallics. The predictive capabilities and accuracy of the constitutive formulation and the finite-element computational scheme have been investigated by simulating experimental results for single crystal nickel aluminide. There is good agreement between the computational and the experimental results. The use of the proposed constitutive formulation also resulted in accurate predictions of the increased strength of nickel aluminide as a function of increases in temperature. This is a strong indication that the dislocation based constitutive formulation and the finite-element algorithm result in accurate predictions of the deformation and strength response of monocrystalline nickel aluminide for the strain range and temperatures used in the experimental study. Based on these results, this dislocation based constitutive formulation will be used in future studies to investigate the effects of dislocation motion, interaction, and transmission on finite strain deformation and failure modes in intermetallic materials separated by high angle CSL and random GBs.
DA - 1998/1/13/
PY - 1998/1/13/
DO - 10.1016/s1359-6462(97)00512-5
VL - 38
IS - 4
SP - 631-636
SN - 1359-6462
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0031599393&partnerID=MN8TOARS
ER -
TY - JOUR
TI - Quasi-steady shrinking core analysis of wood combustion
AU - Ouedraogo, A
AU - Mulligan, JC
AU - Cleland, JG
T2 - COMBUSTION AND FLAME
AB - A shrinking core model of the combustion of individual chunkwood and particle wood elements is developed and validated by comparison with literature data. The model is formulated on the physical evidence that large wood specimens inserted into a hot convective environment lose weight mostly over a relatively thin outside layer, while the interior (core) remains relatively undisturbed. The modeling of the complete process requires a correlation of the turbulent heat and mass transfer coefficients which include explicitly the effects of transpiration of volatilized organic compounds and moisture, along with geometry, and equivalent radius. The fuel element burnout time is shown to be a function of fuel properties, moisture content, and size. Drier and smaller elements burn faster while moisture is shown to slow the shrinking rate due to the cooling effects of transpiration and the latent heat of evaporation.
DA - 1998/7//
PY - 1998/7//
DO - 10.1016/S0010-2180(97)00291-5
VL - 114
IS - 1-2
SP - 1-12
SN - 0010-2180
ER -
TY - JOUR
TI - Modeling turbulence in the presence of adverse pressure gradients
AU - Rao, MS
AU - Hassan, HA
T2 - JOURNAL OF AIRCRAFT
DA - 1998///
PY - 1998///
DO - 10.2514/2.2328
VL - 35
IS - 3
SP - 500-502
SN - 0021-8669
ER -
TY - JOUR
TI - Enhanced power spectrum estimates using Kalman reconstruction
AU - Benedict, LH
AU - Gould, RD
T2 - JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME
AB - A number of power spectral density (PSD) estimators were assessed using real laser Doppler anemometer (LDA) data from grid generated turbulence. PSD estimates from the raw data via the slotting technique and direct transform method were compared to those estimated from sample and hold, linear, and Kalman reconstructed velocity time histories. Of the reconstruction schemes, only Kalman reconstruction was shown to significantly reduce the effects of noise on the measurements leading to an additional 2 decades in power of high frequency information.
DA - 1998/6//
PY - 1998/6//
DO - 10.1115/1.2820641
VL - 120
IS - 2
SP - 253-256
SN - 0098-2202
ER -
TY - JOUR
TI - Comment on "conjecture about orthogonal functions" - Reply
AU - Silverberg, L
T2 - JOURNAL OF GUIDANCE CONTROL AND DYNAMICS
AB - I N “ConjectureAbout OrthogonalFunctions,”1 I presenteda conjecture “...to provoke insight that could lead to a proof of the conjecture at a later date.” That insight came from Stephen Hendry in his comment about that paper.Hendry showed that the conjecture follows froma theoremgivenin the1939 textbookentitledOrthogonal Polynomialsby Szego. The theorem is called the Gauss–Jacobi quadraturetheorem,althoughcontributionsto the theoremwere also made by Christoffel, Mehler, and Heine.3i8 The theorem is stated as follows. If x1 < x2 < ¢ ¢ ¢ < xn denote the zeros of the polynomial pn.x/, there exist real numbers31; 32; : : : ; 3n such that Z b
DA - 1998///
PY - 1998///
DO - 10.2514/2.4223
VL - 21
IS - 1
SP - 189-190
SN - 0731-5090
ER -
TY - JOUR
TI - A sliding mode controller for vehicle active suspension systems with non-linearities
AU - Kim, C
AU - Ro, PI
T2 - PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART D-JOURNAL OF AUTOMOBILE ENGINEERING
AB - In this paper, the control of an active suspension system using a quarter car model has been investigated. Due to the presence of non-linearities such as a hardening spring, a quadratic damping force and the ‘tyre lift-off’ phenomenon in a real suspension system, it is very difficult to achieve desired performance using linear control techniques. To ensure robustness for a wide range of operating conditions, a sliding mode controller has been designed and compared with an existing nonlinear adaptive control scheme in the literature. The sliding mode scheme utilizes a variant of a sky-hook damper system as a reference model which does not require real-time measurement of road input. The robustness of the scheme is investigated through computer simulation, and the efficacy of the scheme is shown both in time and frequency domains. In particular, when the vertical load to the sprung mass is changed, the sliding mode control resumes normal operation faster than the nonlinear self-tuning control and the passive system by factors of 3 and 6, respectively, and suspension deflection is kept to a minimum. Other results showed advantages of the sliding mode control scheme in a quarter car system with realistic non-linearities.
DA - 1998///
PY - 1998///
DO - 10.1243/0954407981525812
VL - 212
IS - D2
SP - 79-92
SN - 0954-4070
KW - sliding mode
KW - active suspension
KW - non-linearities
ER -