252 Matching Results

Search Results

Advanced search parameters have been applied.

Modal parameters for a flat plate supported by an oil film.

Description: This paper examines the resonant frequencies, Mode shapes, and damping values for a square plate suppcirted by an oil film. Such a study is motivated by interesl: in oil-supported slip tables used for vibration testing. Rtssonant frequencies and percent critical damping were measured for four cases: plate freely suspended; plate with free end conditions and suppoited by an oil film; plate fixed at several locations; and plate fixed at several locations while supported by an oil film. Analytical estimates of the modal properties and modal propertie!j derived from measured data are compared and discrepancies discussed.
Date: January 1, 2003
Creator: Jauhola, A. G. (Andrew G.); Kinzel, E. C. (Edward C.); Reding, D. (Derek) & Hunter, N. F. (Norman F.)
Partner: UNT Libraries Government Documents Department

Slip stacking experiments at Fermilab main injector

Description: In order to achieve an increase in proton intensity, Fermilab Main Injector will use a stacking process called ''slip stacking''. The intensity will be doubled by injecting one train of bunches at a slightly lower energy, another at a slightly higher energy, then bringing them together for the final capture. Beam studies have started for this process and we have already verified that, at least for a low beam intensity, the stacking procedure works as expected. For high intensity operation, development work of the feedback and feedforward systems is under way.
Date: June 2, 2003
Creator: al., Kiyomi Koba et
Partner: UNT Libraries Government Documents Department

Slip stacking

Description: We have started beam studies for ''slip stacking''[1] in the Main Injector in order to increase proton intensity on a target for anti-proton production. It has been verified that the system for slip stacking is working with low intensity beam. For a high intensity operation, we are developing a feedback[2][3] and feedforward system.
Date: September 19, 2002
Creator: Steimel, Kiyomi Koba and James
Partner: UNT Libraries Government Documents Department

6 Batch Injection and Slipped Beam Tune Measurements in Fermilab?s Main Injector

Description: During NOVA operations it is planned to run the Fermilab Recycler in a 12 batch slip stacking mode. In preparation for this, measurements of the tune during a six batch injection and then as the beam is decelerated by changing the RF frequency have been carried out in the Main Injector. The coherent tune shifts due to the changing beam intensity were measured and compared well with the theoretically expected tune shift. The tune shifts due to changing RF frequency, required for slip stacking, also compare well with the linear theory, although some nonlinear affects are apparent at large frequency changes. These results give us confidence that the expected tunes shifts during 12 batch slip stacking Recycler operations can be accommodated.
Date: May 1, 2012
Creator: Scott, D. J.; Capista, D.; Kourbanis, I.; Seiya, K. & Yan, M.-J.
Partner: UNT Libraries Government Documents Department

Mechanical Deformation of KD2xH2(1-x)PO4

Description: The deformation behavior of rapidly-grown tetragonal KD{sub 2x} H{sub 1(1-x)} PO{sub 4} (KDP and DKDP) single crystals, with a deuteration degree x of 0.0, 0.3, and 0.6, is studied by nanoindentation with a 1 {micro}m radius spherical indenter. Within experimental error, the deformation behavior is found to be independent of deuterium content and different for (001) and (100) surfaces. Multiple discontinuities (so called ''pop-in'' events) in force-displacement curves are observed during indentation loading, but not during unloading. Slip is identified as the major mode of plastic deformation in DKDP, and pop-in events are attributed to the initiation of slip.
Date: November 10, 2003
Creator: Kucheyev, S; Siekhaus, W; Land, T & Demos, S
Partner: UNT Libraries Government Documents Department

Calculation of the Slip System Activity in Deformed Zinc Single Crystals Using Digital 3-D Image Correlation Data

Description: A 3-D image correlation system, which measures the full-field displacements in 3 dimensions, has been used to experimentally determine the full deformation gradient matrix for two zinc single crystals. Based on the image correlation data, the slip system activity for the two crystals has been calculated. The results of the calculation show that for one crystal, only the primary slip system is active, which is consistent with traditional theory. The other crystal however, shows appreciable deformation on slip systems other than the primary. An analysis has been conducted which confirms the experimental observation that these other slip system deform in such a manner that the net result is slip which is approximately one third the magnitude and directly orthogonal to the primary system.
Date: February 21, 2006
Creator: Florando, J; Rhee, M; Arsenlis, A; LeBlanc, M & Lassila, D
Partner: UNT Libraries Government Documents Department

Behavior of Repeating Earthquake Sequences in Central California and the Implications for Subsurface Fault Creep

Description: Repeating earthquakes (REs) are sequences of events that have nearly identical waveforms and are interpreted to represent fault asperities driven to failure by loading from aseismic creep on the surrounding fault surface at depth. We investigate the occurrence of these REs along faults in central California to determine which faults exhibit creep and the spatio-temporal distribution of this creep. At the juncture of the San Andreas and southern Calaveras-Paicines faults, both faults as well as a smaller secondary fault, the Quien Sabe fault, are observed to produce REs over the observation period of March 1984-May 2005. REs in this area reflect a heterogeneous creep distribution along the fault plane with significant variations in time. Cumulative slip over the observation period at individual sequence locations is determined to range from 5.5-58.2 cm on the San Andreas fault, 4.8-14.1 cm on the southern Calaveras-Paicines fault, and 4.9-24.8 cm on the Quien Sabe fault. Creep at depth appears to mimic the behaviors seen of creep on the surface in that evidence of steady slip, triggered slip, and episodic slip phenomena are also observed in the RE sequences. For comparison, we investigate the occurrence of REs west of the San Andreas fault within the southern Coast Range. Events within these RE sequences only occurred minutes to weeks apart from each other and then did not repeat again over the observation period, suggesting that REs in this area are not produced by steady aseismic creep of the surrounding fault surface.
Date: July 9, 2007
Creator: Templeton, D C; Nadeau, R & Burgmann, R
Partner: UNT Libraries Government Documents Department

Finite element modeling for validation of structural damage identification experimentation.

Description: The project described in this report was performed to couple experimental and analytical techniques in the field of structural health monitoring and darnage identification. To do this, a finite dement model was Constructed of a simulated three-story building used for damage identification experiments. The model was used in conjunction with data from thie physical structure to research damage identification algorithms. Of particular interest was modeling slip in joints as a function of bolt torque and predicting the smallest change of torque that could be detected experimentally. After being validated with results from the physical structure, the model was used to produce data to test the capabilities of damage identification algorithms. This report describes the finite element model constructed, the results obtained, and proposed future use of the model.
Date: January 1, 2001
Creator: Stinemates, D. W. (Daniel W.) & Bennett, J. G. (Joel G.)
Partner: UNT Libraries Government Documents Department

Halliburton Composite Bridge Plug Assembly

Description: The overall objectives of this CRADA were to assist Halliburton in analyzing a composite bridge plug and to determine why their original design was failing in the field. In Phase 1, finite element analyses were done on the original composite slip design and several alternative designs. The composite slip was the component in the bridge plug that was failing. The finite element code ABAQUS was used for these calculations and I-DEAS was used as the pre- and post-processor in the analyses. Several different designs and materials were analyzed and recommendations were made towards improving the design. In Phase 2, the objective was to develop finite element models that would accurately represent the deformations in the entire all-composite 4-1/2' diameter bridge plug assembly. The finite element code LS-DYNA was used and the results from this effort were intended to expand Halliburton's composite design and analysis capabilities with regard to developing future composite components for downhole tools. In addition to the finite element modeling, this effort involved the utilization of micromechanics to determine the necessary composite material properties that were needed as input for finite element codes.
Date: January 15, 2005
Creator: Starbuck, J.M.; Luttrell, C.R. & Aramayo, G.
Partner: UNT Libraries Government Documents Department

Long-term slip rate of the southern San Andreas Fault, from 10Be-26Al surface exposure dating of an offset alluvial fan

Description: We determine the long-term slip rate of the southern San Andreas Fault in the southeastern Indio Hills using {sup 10}Be and {sup 26}Al isotopes to date an offset alluvial fan surface. Field mapping complemented with topographic data, air photos and satellite images allow to precisely determine piercing points across the fault zone that are used to measure an offset of 565 {+-} 80 m. A total of twenty-six quartz-rich cobbles from three different fan surfaces were collected and dated. The tight cluster of nuclide concentrations from 19 samples out of 20 from the offset fan surface implies a simple exposure history, negligible prior exposure and erosion, and yield an age of 35.5 {+-} 2.5 ka. The long-term slip rate of the San Andreas Fault south of Biskra Palms is thus 15.9 {+-} 3.4 mm/yr. This rate is about 10 mm/yr slower than geological (0-14 ka) and short-term geodetic estimates for this part of the San Andreas Fault implying changes in slip rate or in faulting behavior. This result puts new constraints on the slip rate of the San Jacinto and on the Eastern California Shear Zone for the last 35 ka. Our study shows that more sites along the major faults of southern California need to be targeted to better constrain the slip-rates over different time scales.
Date: January 13, 2006
Creator: der Woerd, J v; Klinger, Y; Sieh, K; Tapponnier, P; Ryerson, F & M?riaux, A
Partner: UNT Libraries Government Documents Department

Comments on the slip factor and the relation Delta phi = -h Delta theta

Description: The definition of the slip factor can be obtained from the phase equation. However, a derivation using the relation {Delta}{phi} = -h{Delta}{theta} leads to a different slip-factor definition. This apparent paradox is examined in detail and resolved. Here {Delta}{phi} is the rf phase difference and {Delta}{theta} is the azimuthal phase difference around the accelerator ring between an off-momentum particle and the synchronous particle, while h is the rf harmonic.
Date: September 1, 2009
Creator: Ng, K.Y.
Partner: UNT Libraries Government Documents Department

A dynamic dispersion insert in the Fermilab Main Injector for momentum collimation

Description: The Fermilab Main Injector (MI) accelerator is designed as a FODO lattice with zero dispersion straight sections. A scheme will be presented that can dynamically alter the dispersion of one of the long straight sections to create a non-zero dispersion straight section suitable for momentum collimation. During the process of slip stacking DC beam is generated which is lost during the first few milliseconds of the ramp. A stationary massive primary collimator/absorber with optional secondary masks could be utilized to isolate beam loss due to uncaptured beam.
Date: June 1, 2007
Creator: Johnson, D. E.
Partner: UNT Libraries Government Documents Department


Description: Ultra-high strength metallic multilayers are ideal for investigating the effects of length scales in plastic deformation of metallic materials. Experiments on model systems show that the strengths of these materials increase with decreasing bilayer period following the Hall-Petch model. However, as the layer thickness is reduced to the nm-scale, the number of dislocations in the pile-up approaches one and the pile-up based Hall-Petch model ceases to apply. For nm-scale semi-coherent multilayers, we hypothesize that plastic flow occurs by the motion of single dislocation loops, initially in the softer layer, that deposit misfit type dislocation arrays at the interface and transfer load to the harder phase. The stress concentration eventually leads to slip in the harder phase, overcoming the resistance from the misfit arrays at the interface. A model is developed within the framework of classical dislocation theory to estimate the strengthening from this mechanism. The model predictions are compared with experimentally measured strengths.
Date: December 1, 2000
Creator: MISRA, A. & HIRTH, J.
Partner: UNT Libraries Government Documents Department

An Initial Overview of Iwan Modeling for Mechanical Joints

Description: The structural dynamics modeling of engineering structures must accommodate the energy dissipation due to microslip in mechanical joints. Given the nature of current hardware and software environments, this will require the development of constitutive models for joints that both adequately reproduce the important physics and lend themselves to efficient computational processes. The exploration of the properties of mechanical joints--either through fine resolution finite element modeling or through experiment--is itself an area of research, but some qualitative behavior appears to be established. The work presented here is the presentation of a formulation of idealized elements due to Iwan, that appears capable of reproducing the important joint properties as they are now understood. Further, methods for selecting parameters for that model by joining the results from experiments in regimes of small and large load are developed. The significance of this work is that a reduced order model is presented that is capable of reproducing the important qualitative properties of mechanical joints using only a small number of parameters.
Date: March 1, 2001
Partner: UNT Libraries Government Documents Department

Deformation by grain boundary sliding and slip creep versus diffusional creep

Description: A review is presented of the debates between the present authors and other investigators regarding the possible role of diffusional creep in the plastic flow of polycrystalline metals at low stresses. These debates are recorded in eleven papers over the past seventeen years. ln these papers it has been shown that the creep rates of materials in the so-called �diffusional creep region� are almost always higher than those predicted by the diffusional creep theory. Additionally, the predictions of grain size effects and stress exponents from diffusional creep theory are often not found in the experimental data. Finally, denuded zones have been universally considered to be direct evidence for diffusional creep; but, those reported in the literature are shown to be found only under conditions where a high stress exponent is observed. Also, the locations of the denuded zones do not match those predicted. Alternative mechanisms are described in which diffusion-controlled dislocation creep and/or grain boundary sliding are the dominant deformation processes in low-stress creep. It is proposed that denuded zones are formed by stress-directed grain boundary migration with the precipitates dissolving in the moving grain boundaries. The above observations have led us to the conclusion that grain boundary sliding and slip creep are in fact the principal mechanisms for observations of plastic flow in the so-called �diffusional creep regions. �
Date: November 4, 1998
Creator: Ruano, O. A.; Sherby, O. D. & Wadsworth, J.
Partner: UNT Libraries Government Documents Department

Operating stresses in aircraft-engine crankshafts and connecting rods 1: slip-ring and bush combinations for dynamic-strain measurements

Description: From Summary: "Tests were conducted to develop a slip-ring and brush system that will perform satisfactorily in aircraft-engine, dynamic-strain-measuring applications where resistance-wire strain gages are the means of measuring the strain and to correlate the data obtained from tests in order to provide a basis for predicting the performance of similar slip-ring and brush systems operating under conditions similar to those imposed by these tests." 24 combinations of materials were tested dry and 8 were tested in oil. The five most predictable systems were identified.
Date: March 30, 1945
Creator: Dutee, Francis J.; Phillips, Franklyn W. & Kemp, Richard H.
Partner: UNT Libraries Government Documents Department

Estimated bounds on rock permeability changes from THM Processes

Description: We performed THM modeling to estimate bounds on permeability changes in the NFE. For our modeling, we used the TM three-dimensional (3-D) finite-difference code FLAC{sup 3D} version 2.0 (Itasca Consulting Group Inc. 1997) to compute changes in stress and displacement in an elastic model subjected to temperature changes over time. Output from TH modeling (Hardin et al., 1998, Chapter 3) using the code NUFT (Nitao 1993) provided the temperature changes for input to FLAC{sup 3D}. We then estimated how the stress changes could affect permeability. For this report, we chose to base our 3-D THM modeling on a coarser version of the 2-D model we ran for the work described in Chapter 4 of the Near-Field/Altered Zone Models Report (Hardin et al., 1998, Chapter 4). The grid and temperature field were based on those used by the TH code for 50 yr of heating for the reference Case 1 TH model calculated using Total System Performance Assessment-Viability Assessment (TSPA-VA) base-case properties, nominal infiltration, and a point-load repository design (Hardin et al., 1998, Chapter 3). The stress field rotated in the region between and below the drifts after 50 yr of heating. High vertical shear stresses were computed for these regions. The maximum computed displacement was about 7 cm, mainly vertical. Estimates of permeability changes were obtained by analyzing stresses, following a method we developed previously for 2-D models. In our 3-D modeling for this report, we only considered vertical and horizontal fractures. We extended our 2-D method to a simplified 3-D case. We conclude that widespread permeability enhancement is likely for fractures parallel to NS fracture set No.2, the vertical fractures that strike north-south, for regions above the drifts. In some regions just above the drifts, permeability may increase by a minimum of a factor of two and possibly more ...
Date: August 1, 1998
Creator: Berge, P A; Blair, S C & Wang, H F
Partner: UNT Libraries Government Documents Department

Plane wave method for elastic wave scattering by a heterogeneous fracture

Description: A plane-wave method for computing the three-dimensional scattering of propagating elastic waves by a planar fracture with heterogeneous fracture compliance distribution is presented. This method is based upon the spatial Fourier transform of the seismic displacement-discontinuity (SDD) boundary conditions (also called linear slip interface conditions), and therefore, called the wave-number-domain SDD method (wd-SDD method). The resulting boundary conditions explicitly show the coupling between plane waves with an incident wave number component (specular component) and scattered waves which do not follow Snell's law (nonspecular components) if the fracture is viewed as a planar boundary. For a spatially periodic fracture compliance distribution, these boundary conditions can be cast into a linear system of equations that can be solved for the amplitudes of individual wave modes and wave numbers. We demonstrate the developed technique for a simulated fracture with a stochastic (correlated) surface compliance distribution. Low- and high-frequency solutions of the method are also compared to the predictions by low-order Born series in the weak and strong scattering limit.
Date: February 21, 2003
Creator: Nakagawa, Seiji; Nihei, Kurt T. & Myer, Larry R.
Partner: UNT Libraries Government Documents Department

Polycrystal Simulations of Texture Evolution during Deformation Processing

Description: Some recent research on the hot deformation of aluminum alloys has indicated that at elevated temperatures, slip occurs on {110}<110> systems in addition to the usual {111}<110> systems active at lower temperatures. The effect of these additional slip systems on the texture evolution of aluminum single and polycrystals is studied using finite element simulations. The crystals are deformed in plane strain compression, and the constitutive response is modeled using crystal plasticity to track the reorientation of the crystals. By discretizing each crystal with a large number of elements, the non-uniform deformations due to local inhomogeneities and interactions with neighboring crystals are modeled. The resulting textures and microstructures are examined with regard to effect of including the additional systems, initial orientation of the single crystals, and stability of the cube orientation.
Date: May 11, 1998
Creator: Radhakrishnan, B.; Sarma, G. & Zacharia, T.
Partner: UNT Libraries Government Documents Department

Processing Variables of Alumina Slips and Their Effects on the Density and Grain Size of the Sintered Sample

Description: High densities and small grain size of alumina ceramic bodies provide high strength and better mechanical properties than lower density and larger grain size bodies. The final sintered density and grain size of slip-cast, alumina samples depends greatly on the processing of the slip and the alumina powder, as well as the sintering schedule. There were many different variables explored that include initial powder particle size, slurry solids percent, amount and type of dispersant used, amount and type of binder used, and sintering schedule. Although the experimentation is not complete, to this point the sample with the highest density and smallest grain size has been a SM8/Nano mixture with Darvan C as the dispersant and Polyvinyl Alcohol (PVA) as the binder, with a solids loading of 70 wt% and a 1500 C for 2 hours sintering schedule. The resultant density was 98.81% of theoretical and the average grain size was approximately 2.5 {micro}m.
Date: January 1, 2002
Creator: Rowley, R. & Chu, H.
Partner: UNT Libraries Government Documents Department