Search NASA⌕ Search

SEARCH · Search NASA

Results for “slip prediction”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

A kinematic model for the evolution of the Gorda Plate

The magnetic lineation pattern produced by the Gorda Rise reflects a complex tectonic history marked by propagating ridges and nonrigid deformation of the Gorda plate. The Pacific-side lineation pattern is matched using a kinematic model which incorporates northward and southward propagating ridge segments and ridge rotation. By superimposing flexural-slip style deformation on the resulting Gorda-side lineations, and allowing convergent motion at the Mendocino Fracture Zone, the Gorda magnetic pattern is also successfully predicted. A similar model, but one which does not allow convergence at the Mendocino Fracture Zone, fails to produce the observed lineation pattern. Model predictions of the amount of material that would be 'obducted' at the Mendocino due to convergence between the Gorda and Pacific agree with bathymetric and density estimates of the amount of material located along the Mendocino Ridge.

Stoddard, Paul R.↗
NASA NTRS1995

Coseismic fault slip associated with the 1992 M(sub w) 6.1 Joshua Tree, California, earthquake: Implications for the Joshua Tree-Landers earthquake sequence

Coseismic surface deformation associated with the M(sub w) 6.1, April 23, 1992, Joshua Tree earthquake is well represented by estimates of geodetic monument displacements at 20 locations independently derived from Global Positioning System and trilateration measurements. The rms signal to noise ratio for these inferred displacements is 1.8 with near-fault displacement estimates exceeding 40 mm. In order to determine the long-wavelength distribution of slip over the plane of rupture, a Tikhonov regularization operator is applied to these estimates which minimizes stress variability subject to purely right-lateral slip and zero surface slip constraints. The resulting slip distribution yields a geodetic moment estimate of 1.7 x 10(exp 18) N m with corresponding maximum slip around 0.8 m and compares well with independent and complementary information including seismic moment and source time function estimates and main shock and aftershock locations. From empirical Green's functions analyses, a rupture duration of 5 s is obtained which implies a rupture radius of 6-8 km. Most of the inferred slip lies to the north of the hypocenter, consistent with northward rupture propagation. Stress drop estimates are in the range of 2-4 MPa. In addition, predicted Coulomb stress increases correlate remarkably well with the distribution of aftershock hypocenters; most of the aftershocks occur in areas for which the mainshock rupture produced stress increases larger than about 0.1 MPa. In contrast, predicted stress changes are near zero at the hypocenter of the M(sub w) 7.3, June 28, 1992, Landers earthquake which nucleated about 20 km beyond the northernmost edge of the Joshua Tree rupture. Based on aftershock migrations and the predicted static stress field, we speculate that redistribution of Joshua Tree-induced stress perturbations played a role in the spatio-temporal development of the earth sequence culminating in the Landers event.

Bennett, Richard A.↗
NASA NTRS1994

Deformation across the western United States: A local estimate of Pacific-North America transform deformation

We obtain a locally based estimate of Pacific-North America relative motion and an uncertainly in this estimate by integrating deformation rate along three different paths leading west across southwestern North America from east of the Rio Grande Rift to near the continental escarpment. Data are primarily Quatenary geologic slip rates estimates, and resulting deformation determinations therefore are 'instantaneous' in a geologic sense but 'long term' with respect to earthquake cycles. We deduce a rate of motion of the Pacific plane relative to North America that is 48 +/- 2 mm/yr, a rate indistinguishable from that predicted by the global kinematics models RM2 and NUVEL-1; however, we obtain an orientation that is 5-9 deg counterclockwise of these models. A more westerly motion of the Pacific plate, with respect to North America, is calculated from all three paths. The relatively westerly motion of the Pacific plate is accomodated by deformation in the North American continent that includes slip on relatively counterclockwise-oriented strike-slip faults (including the San Andreas fault), whic is especially relevant in and south of the Transverse Ranges, and a margin-normal component of net extension across the continent, which is especially relevant north of the Transverse Ranges. Deformation of the SW United States occurs in regionally coherent domains within the style of deformation is approximately uniform.

Humphreys, Eugene D.↗
NASA NTRS1984

Structure of nonevaporating sprays - Measurements and predictions

Structure measurements were completed within the dilute portion of axisymmetric nonevaporating sprays (SMD of 30 and 87 microns) injected into a still air environment, including: mean and fluctuating gas velocities and Reynolds stress using laser-Doppler anemometry; mean liquid fluxes using isokinetic sampling; drop sizes using slide impaction; and drop sizes and velocities using multiflash photography. The new measurements were used to evaluate three representative models of sprays: (1) a locally homogeneous flow (LHF) model, where slip between the phases was neglected; (2) a deterministic separated flow (DSF) model, where slip was considered but effects of drop interaction with turbulent fluctuations were ignored; and (3) a stochastic separated flow (SSF) model, where effects of both interphase slip and turbulent fluctuations were considered using random sampling for turbulence properties in conjunction with random-walk computations for drop motion. The LHF and DSF models were unsatisfactory for present test conditions-both underestimating flow widths and the rate of spread of drops. In contrast, the SSF model provided reasonably accurate predictions, including effects of enhanced spreading rates of sprays due to drop dispersion by turbulence, with all empirical parameters fixed from earlier work.

Solomon, A. S. P.↗
NASA NTRS1972

Momentum flux in two phase two component low quality flow.

Values of a one-dimensional momentum flux at a test section discharge station of a two-phase two-component low quality flow computed by two methods, one based on a one-dimensional homogeneous model and the other on a variable slip model, are compared to experimental values for a range of two-phase flow conditions. The comparison seems to indicate the superior accuracy in momentum flux predictions to be on the side of the one-dimensional homogeneous model.

Baumeister, K. J.↗
NASA NTRS1984

On the prediction of auto-rotational characteristics of light airplane fuselages

A semi-empirical theory is presented for the estimation of aerodynamic forces and moments acting on a steadily rotating (spinning) airplane fuselage, with a particular emphasis on the prediction of its auto-rotational behavior. This approach is based on an extension of the available analytical methods for high angle of attack and side-slip and then coupling this procedure with strip theory for application to a rotating airplane fuselage. The analysis is applied to the fuselage of a light general aviation airplane and the results are shown to be in fair agreement with experimental data.

Pamadi, B. N.↗
NASA NTRS2010

Two-Speed Gearbox Dynamic Simulation Predictions and Test Validation

Dynamic simulations and experimental validation tests were performed on a two-stage, two-speed gearbox as part of the drive system research activities of the NASA Fundamental Aeronautics Subsonics Rotary Wing Project. The gearbox was driven by two electromagnetic motors and had two electromagnetic, multi-disk clutches to control output speed. A dynamic model of the system was created which included a direct current electric motor with proportional-integral-derivative (PID) speed control, a two-speed gearbox with dual electromagnetically actuated clutches, and an eddy current dynamometer. A six degree-of-freedom model of the gearbox accounted for the system torsional dynamics and included gear, clutch, shaft, and load inertias as well as shaft flexibilities and a dry clutch stick-slip friction model. Experimental validation tests were performed on the gearbox in the NASA Glenn gear noise test facility. Gearbox output speed and torque as well as drive motor speed and current were compared to those from the analytical predictions. The experiments correlate very well with the predictions, thus validating the dynamic simulation methodologies.

Lewicki, David G.↗
NASA NTRS1987

Life prediction and constitutive models for engine hot section anisotropic materials

The results are presented of a program designed to develop life prediction and constitutive models for two coated single crystal alloys used in gas turbine airfoils. The two alloys are PWA 1480 and Alloy 185. The two oxidation resistant coatings are PWA 273, an aluminide coating, and PWA 286, an overlay NiCoCrAlY coating. To obtain constitutive and fatigue data, tests were conducted on uncoated and coated specimens loaded in the CH76 100 CH110 , CH76 110 CH110 , CH76 111 CH110 and CH76 123 CH110 crystallographic directions. Two constitutive models are being developed and evaluated for the single crystal materials: a micromechanic model based on crystallographic slip systems, and a macroscopic model which employs anisotropic tensors to model inelastic deformation anisotropy. Based on tests conducted on the overlay coating material, constitutive models for coatings also appear feasible and two initial models were selected. A life prediction approach was proposed for coated single crystal materials, including crack initiation either in the coating or in the substrate. The coating initiated failures dominated in the tests at load levels typical of gas turbine operation. Coating life was related to coating stress/strain history which was determined from specimen data using the constitutive models.

Swanson, G. A.↗
NASA NTRS1978

Wind Field and Trajectory Models for Tornado-Propelled Objects

A mathematical model to predict the trajectory of tornado born objects postulated to be in the vicinity of nuclear power plants is developed. An improved tornado wind field model satisfied the no slip ground boundary condition of fluid mechanics and includes the functional dependence of eddy viscosity with altitude. Subscale wind tunnel data are obtained for all of the missiles currently specified for nuclear plant design. Confirmatory full-scale data are obtained for a 12 inch pipe and automobile. The original six degree of freedom trajectory model is modified to include the improved wind field and increased capability as to body shapes and inertial characteristics that can be handled. The improved trajectory model is used to calculate maximum credible speeds, which for all of the heavy missiles are considerably less than those currently specified for design. Equivalent coefficients for use in three degree of freedom models are developed and the sensitivity of range and speed to various trajectory parameters for the 12 inch diameter pipe are examined.

Redmann, G. H.↗
NASA NTRS1999

Fatigue Failure Criteria for Single Crystal Nickel Superalloys

High Cycle Fatigue (HCF) induced failures in aircraft gas-turbine and rocket engine turbopump blades is a pervasive problem. Single crystal turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry and NASA because of their superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys. Single-crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the pan geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades is complicated to predict due to the material orthotropy and variations in crystal orientations. A fatigue failure criteria based on the maximum shear stress amplitude [delta t max] on the 30 slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criteria reduces the scatter in uniaxial LCF test data, for four different specimen orientations, for PWA 1484 at 1200 F in air, quite well. A power law curve fit of the failure parameter, delta t max, vs. cycles to failure is presented.

Arakere, Nagaraj K.↗
NASA NTRS1995

Centrifugal and Axial Pump Design and Off-Design Performance Prediction

A meanline pump-flow modeling method has been developed to provide a fast capability for modeling pumps of cryogenic rocket engines. Based on this method, a meanline pump-flow code PUMPA was written that can predict the performance of pumps at off-design operating conditions, given the loss of the diffusion system at the design point. The design-point rotor efficiency and slip factors are obtained from empirical correlations to rotor-specific speed and geometry. The pump code can model axial, inducer, mixed-flow, and centrifugal pumps and can model multistage pumps in series. The rapid input setup and computer run time for this meanline pump flow code make it an effective analysis and conceptual design tool. The map-generation capabilities of the code provide the information needed for interfacing with a rocket engine system modeling code. The off-design and multistage modeling capabilities of PUMPA permit the user to do parametric design space exploration of candidate pump configurations and to provide head-flow maps for engine system evaluation.

Veres, Joseph P.↗
NASA NTRS1984

An extensive region of off-ridge normal-faulting earthquakes in the southern Indian Ocean

A verified prediction of the theory of plate tectonics is that the focal mechanisms of earthquakes on the mid-ocean ridge system indicate either normal faulting on ridge segments or strike-slip faulting on transform faults. A broad region in the southern Indian Ocean which differs from typical ridge and intraplate regimes has been identified. In this region a number of large off-ridge earthquakes have occurred in the last 20 years. The mechanisms for these events, where known, all involve normal faulting. Nine of these earthquakes have been studied in detail using a formal inversion technique based on matching synthetic body waves to observed seismograms.

Bergman, E. A.↗
NASA NTRS1993

Mechanically fastened composite laminates subjected to combined bearing-bypass and shear loading

Bolts and rivets provide a means of load transfer in the construction of aircraft. However, they give rise to stress concentrations and are often the source and location of static and fatigue failures. Furthermore, fastener holes are prone to cracks during take-off and landing. These cracks present the most common origin of structural failures in aircraft. Therefore, accurate determination of the contact stresses associated with such loaded holes in mechanically fastened joints is essential to reliable strength evaluation and failure prediction. As the laminate is subjected to loading, the contact region, whose extent is not known, develops between the fastener and the hole boundary through this contact region, which consists of slip and no-slip zones due to friction. The presence of the unknown contact stress distribution over the contact region between the pin and the composite laminate, material anisotropy, friction between the pin and the laminate, pin-hole clearance, combined bearing-bypass and shear loading, and finite geometry of the laminate result in a complex non-linear problem. In the case of bearing-bypass loading in compression, this non-linear problem is further complicated by the presence of dual contact regions. Previous research concerning the analysis of mechanical joints subjected to combined bearing-bypass and shear loading is non-existent. In the case of bearing-bypass loading only, except for the study conducted by Naik and Crews (1991), others employed the concept of superposition which is not valid for this non-linear problem. Naik and Crews applied a linear finite element analysis with conditions along the pin-hole contact region specified as displacement constraint equations. The major shortcoming of this method is that the variation of the contract region as a function of the applied load should be known a priori. Also, their analysis is limited to symmetric geometry and material systems, and frictionless boundary conditions. Since the contact stress distribution and the contact region are not known a priori, they did not directly impose the boundary conditions appropriate for modelling the contact and on-contact regions between the fastener and the hole. Furthermore, finite element analysis is not suitable for iterative design calculations for optimizing laminate construction in the presence of fasteners under complex loading conditions. In this study, the solution method developed by Madenci and Ileri (1992a,b) has been extended to determine the contact stresses in mechanical joints under combined bearing-bypass and shear loading, and bearing-bypass loading in compression resulting in dual contact regions.

Madenci, Erdogan↗
NASA NTRS1983

Traction behavior of two traction lubricants

In the analysis of rolling-sliding concentrated contacts, such as gears, bearings and traction drives, the traction characteristics of the lubricant are of prime importance. The elastic shear modulus and limiting shear stress properties of the lubricant dictate the traction/slip characteristics and power loss associated with an EHD contact undergoing slip and/or spin. These properties can be deducted directly from the initial slope m and maximum traction coefficient micron of an experimental traction curve. In this investigation, correlation equations are presented to predict m and micron for two modern traction fluids based on the regression analysis of 334 separate traction disk machine experiments. The effects of contact pressure, temperature, surface velocity, ellipticity ratio are examined. Problems in deducing lubricant shear moduli from disk machine tests are discussed.

Loewenthal, S. H.↗
NASA NTRS1983

A renormalization group model for the stick-slip behavior of faults

A fault which is treated as an array of asperities with a prescribed statistical distribution of strengths is described. For a linear array the stress is transferred to a single adjacent asperity and for a two dimensional array to three ajacent asperities. It is shown that the solutions bifurcate at a critical applied stress. At stresses less than the critical stress virtually no asperities fail on a large scale and the fault is locked. At the critical stress the solution bifurcates and asperity failure cascades away from the nucleus of failure. It is found that the stick slip behavior of most faults can be attributed to the distribution of asperities on the fault. The observation of stick slip behavior on faults rather than stable sliding, why the observed level of seismicity on a locked fault is very small, and why the stress on a fault is less than that predicted by a standard value of the coefficient of friction are outlined.

Smalley, R. F., Jr.↗
NASA NTRS1984

Elastic model of the traction behavior of two traction lubricants

In the analysis of rolling-sliding concentrated contacts, such as gears, bearings and traction drives, the traction characteristics of the lubricant are of prime importance. The elastic shear modulus and limiting shear stress properties of the lubricant dictate the traction/slip characteristics and power loss associated with an EHD contact undergoing slip and/or spin. These properties can be deducted directly from the initial slope m and maximum traction coefficient micron of an experimental traction curve. In this investigation, correlation equations are presented to predict m and micron for two modern traction fluids based on the regression analysis of 334 separate traction disk machine experiments. The effects of contact pressure, temperature, surface velocity, ellipticity ratio are examined. Problems in deducing lubricant shear moduli from disk machine tests are discussed. Previously announced in STAR as N83-20116

Loewenthal, S. H.↗
NASA NTRS1985

A renormalization group approach to the stick-slip behavior of faults

A fault which is treated as an array of asperities with a perscribed statistical distribution of strengths is described. For a linear array the stress is transferred to a single adjacent asperity and for a two dimensional array to three adjacent asperities. It is shown that the solutions bifurcate at a critical applied stress. At stresses less than the critical stress virtually no asperities fail on a large scale and the fault is locked. At the critical stress the solution bifurcates and asperity failure cascades away from the nucleus of failure. It is found that the stick slip behavior of most faults can be attributed to the distribution of asperities on the fault. The observation of stick slip behavior on faults rather than stable sliding, why the observed level of seismicity on a locked fault is very small, and why the stress on a fault is less than that predicted by a standard value of the coefficient of friction are outlined.

Smalley, R. F., Jr.↗