Electroactive Polymers as Artificial Muscles Changing Robotics Paradigms
The recent emergence of EAP materials with large displacement response enabled great potentials for these materials.
EAP Actuators Electroactive Polymers Artificial Mu↗
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Diaphragm Pump With Resonant Piezoelectric Drive
A diaphragm pump driven by a piezoelectric actuator is undergoing development. This pump is intended to be a prototype of lightweight, highly reliable pumps for circulating cooling liquids in protective garments and high-power electronic circuits, and perhaps for some medical applications. The pump would be highly reliable because it would contain no sliding seals or bearings that could wear, the only parts subject to wear would be two check valves, and the diaphragm and other flexing parts could be designed, by use of proven methods, for extremely long life. Because the pump would be capable of a large volumetric flow rate and would have only a small dead volume, its operation would not be disrupted by ingestion of gas, and it could be started reliably under all conditions. The prior art includes a number piezoelectrically actuated diaphragm pumps. Because of the smallness of the motions of piezoelectric actuators (typical maximum strains only about 0.001), the volumetric flow rates of those pumps are much too small for typical cooling applications. In the pump now undergoing development, mechanical resonance would be utilized to amplify the motion generated by the piezoelectric actuator and thereby multiply the volumetric flow rate. The prime mover in this pump would be a stack of piezoelectric ceramic actuators, one end of which would be connected to a spring that would be part of a spring-and-mass resonator structure. The mass part of the resonator structure would include the pump diaphragm (see Figure 1). Contraction of the spring would draw the diaphragm to the left, causing the volume of the fluid chamber to increase and thereby causing fluid to flow into the chamber. Subsequent expansion of the spring would push the diaphragm to the right, causing the volume of the fluid chamber to decrease, and thereby expelling fluid from the chamber. The fluid would enter and leave the chamber through check valves. The piezoelectric stack would be driven electrically to make it oscillate at the resonance frequency of the spring and- mass structure. This frequency could be made high enough (of the order of 400 Hz) that the masses of all components could be made conveniently small. The resonance would amplify the relatively small motion of the piezoelectric stack (a stroke of the order of 10 m) to a diaphragm stroke of the order of 0.5 mm. The exact amplification factor would depend on the rate of damping of oscillations; this, in turn, would depend on details of design and operation, including (but not limited to) the desired pressure rise and volumetric flow rate. In order to obtain resonance with large displacement, the damping rate must be low enough that the energy imparted to the pumped fluid on each stroke is much less than the kinetic and potential energy exchanged between the mass and spring during each cycle of oscillation. To minimize the power demand of the pump, a highly efficient drive circuit would be used to excite the piezoelectric stack. This circuit (see Figure 2) would amount to a special-purpose regenerative, switching power supply that would operate in a power-source mode during the part of an oscillation cycle when the excitation waveform was positive and in a power-recovery mode during the part of the cycle when the excitation waveform was negative. The circuit would include a voltage-boosting dc-to-dc converter that would convert between a supply potential of 24 Vdc and the high voltage needed to drive the piezoelectric stack. Because of the power-recovery feature, the circuit would consume little power. It should be possible to build the circuit as a compact unit, using readily available components.
Izenson, Michael G.↗
Subsonic Ultra Green Aircraft Research: Truss Braced Wing Design Exploration - Phase II - Volume I
This report summarizes the Truss Braced Wing (TBW) work accomplished by the Boeing Subsonic Ultra Green Aircraft Research (SUGAR) team, consisting of Boeing Research and Technology, Boeing Commercial Airplanes, General Electric, Georgia Tech, Virginia Tech, NextGen Aeronautics, and Microcraft. A multi-disciplinary optimization (MDO) environment defined the geometry that was further refined for the updated SUGAR High TBW configuration. Airfoil shapes were tested in the NASA TCT facility, and an aeroelastic model was tested in the NASA TDT facility. Flutter suppression was successfully demonstrated using control laws derived from test system ID data and analysis models. Aeroelastic impacts for the TBW design are manageable and smaller than assumed in Phase I. Flutter analysis of TBW designs need to include pre-load and large displacement non-linear effects to obtain a reasonable match to test data. With the updated performance and sizing, fuel burn and energy use is reduced by 54% compared to the SUGAR Free current technology Baseline (Goal 60%). Use of the unducted fan version of the engine reduces fuel burn and energy by 56% compared to the Baseline. Technology development roadmaps were updated, and an airport compatibility analysis established feasibility of a folding wing aircraft at existing airports.
Bradley, Marty K.↗
Subsonic Ultra Green Aircraft Research: Phase II- Volume III-Truss Braced Wing Aeroelastic Test Report
This Test Report summarizes the Truss Braced Wing (TBW) Aeroelastic Test (Task 3.1) work accomplished by the Boeing Subsonic Ultra Green Aircraft Research (SUGAR) team, which includes the time period of February 2012 through June 2014. The team consisted of Boeing Research and Technology, Boeing Commercial Airplanes, Virginia Tech, and NextGen Aeronautics. The model was fabricated by NextGen Aeronautics and designed to meet dynamically scaled requirements from the sized full scale TBW FEM. The test of the dynamically scaled SUGAR TBW half model was broken up into open loop testing in December 2013 and closed loop testing from January 2014 to April 2014. Results showed the flutter mechanism to primarily be a coalescence of 2nd bending mode and 1st torsion mode around 10 Hz, as predicted by analysis. Results also showed significant change in flutter speed as angle of attack was varied. This nonlinear behavior can be explained by including preload and large displacement changes to the structural stiffness and mass matrices in the flutter analysis. Control laws derived from both test system ID and FEM19 state space models were successful in suppressing flutter. The control laws were robust and suppressed flutter for a variety of Mach, dynamic pressures, and angle of attacks investigated.
Bradley, Marty K.↗
Linear or Rotary Actuator Using Electromagnetic Driven Hammer as Prime Mover
We claim a hammer driven actuator that uses the fast-motion, low-force characteristics of an electro-magnetic or similar prime mover to develop kinetic energy that can be transformed via a friction interface to produce a higher-force, lower-speed linear or rotary actuator by using a hammering process to produce a series of individual steps. Such a system can be implemented using a voice-coil, electro-mechanical solenoid or similar prime mover. Where a typical actuator provides limited range of motion or low force, the range of motion of a linear or rotary impact driven motor can be configured to provide large displacements which are not limited by the characteristic dimensions of the prime mover.
Paine, Jeffrey S. N.↗
Micro-Horn Arrays for Ultrasonic Impedance Matching
Thin-layered structures containing arrays of micromachined horns, denoted solid micro-horn arrays (SMIHAs), have been conceived as improved means of matching acoustic impedances between ultrasonic transducers and the media with which the transducers are required to exchange acoustic energy. Typically, ultrasonic transducers (e.g., those used in medical imaging) are piezoelectric or similar devices, which produce small displacements at large stresses. However, larger displacements at smaller stresses are required in the target media (e.g., human tissues) with which acoustic energy is to be exchanged. Heretofore, efficiencies in transmission of acoustic energy between ultrasonic transducers and target media have been severely limited because substantial mismatches of acoustic impedances have remained, even when coupling material layers have been interposed between the transducers and the target media. In contrast, SMIHAs can, in principle, be designed to effect more nearly complete acoustic impedance matching, leading to power transmission efficiencies of 90 percent or even greater. The SMIHA concept is based on extension, into the higher-frequency/ lower-wavelength ultrasonic range, of the use of horns to match acoustic impedances in the audible and lower-frequency ultrasonic ranges. In matching acoustic impedance in transmission from a higher-impedance acoustic source (e.g., a piezoelectric transducer) and a lowerimpedance target medium (e.g., air or human tissue), a horn acts as a mechanical amplifier. The shape and size of the horn can be optimized for matching acoustic impedance in a specified frequency range. A typical SMIHA would consist of a base plate, a face plate, and an array of horns that would constitute pillars that connect the two plates (see figure). In use, the base plate would be connected to an ultrasonic transducer and the face plate would be placed in contact with the target medium. As at lower frequencies, the sizes and shapes of the pillars could be tailored for impedance matching in a specified ultrasonic frequency range. In a design that would be simplest to implement by micromachining, the horns would have constant cross-sectional areas as shown in the upper part of the figure. In this case, the dimensions of the horns could be chosen on the basis of a Mason equivalent-circuit model (a simplified model, well-known in the piezoelectric-transducer art, in which the electrical and mechanical dynamics, including electromechanical couplings, are expressed as electrical circuit elements that can include inductors, capacitors, and lumped-parameter complex impedances.) In a more complex, more nearly optimum design, the cross-sectional area of each horn would be either stepped or made to vary as a continuous function of through-the thickness position, as shown in the lower part of the figure.
Rao, Shanti↗
Hydrogen, Methane, Brine Flow Behavior, and Saturation in Sandstone Cores During H 2 and CH 4 Injection and Displacement
Large-scale underground hydrogen storage (UHS) is a critical component in the emerging hydrogen economy. Knowledge of multiphase flow behavior involving hydrogen in storage reservoir formations is crucial to characterizing hydrogen transport properties and essential for the deliverability and storage operations of UHS. There are still many gaps in fully understanding hydrogen–methane–brine multiphase phase flow that require further investigation. In this work, H 2 and CH 4 were injected through brine-saturated sandstone cores using a tri-axial core holder system fitted with flow rate meters and pressure transducers, while the effluent gas concentrations were analyzed using an online micro gas chromatograph. Brine displacement, permeability, and gas breakthrough curves were measured. We studied the flow behavior of hydrogen and methane in sandstone cores through testing brine displacement by gas injection and comparing the hydrogen displacement of methane with the methane displacement of hydrogen. We also tested the differences between horizontal and vertical flow in brine displacement. The results showed that brine displacement was more efficient in a core with higher permeability and porosity, resulting in a higher initial gas saturation. A higher gas injection rate brought about faster gas breakthrough measured by pore volume and sharper concentration curves. Hydrogen did not exhibit abnormal flow in the sandstone when the flow was horizontal and downward vertical. Gas overriding was observed in brine displacements when the flow was horizontal, with hydrogen showing this behavior more profoundly compared to methane. Downward vertical gas injection induced higher efficiency brine displacement compared to horizontal displacement and resulted in a higher initial gas saturation in the sandstone cores. These findings address critical knowledge gaps regarding gas flow patterns and displacement behaviors during hydrogen injection and recovery phases in UHS facilities using methane as the cushion gas. The insights from this research offer valuable guidance for optimizing UHS systems, ensuring operational efficiency, and advancing sustainable energy solutions in alignment with decarbonization goals.
08 HYDROGEN↗
On 'large-scale' stable fiber displacement during interfacial failure in metal matrix composites
Experimental results are presented to show that interfacial failure in sapphire-reinforced niobium is characterized by 'large-scale' (5-15 microns) plasticity-controlled fiber displacements occurring under increasing loads. The results are based on the responses during thin-slice fiber pushout tests wherein the fiber is supported over a hole twice the fiber diameter. The results describe an interfacial failure process that should also occur near fiber ends during pullout when a fiber is well-bonded to a soft, ductile matrix, such that eventual failure occurs by shear within the matrix near the interface.
Petrich, R. R.↗
Curved Displacement Transfer Functions for Geometric Nonlinear Large Deformation Structure Shape Predictions
For shape predictions of structures under large geometrically nonlinear deformations, Curved Displacement Transfer Functions were formulated based on a curved displacement, traced by a material point from the undeformed position to deformed position. The embedded beam (depth-wise cross section of a structure along a surface strain-sensing line) was discretized into multiple small domains, with domain junctures matching the strain-sensing stations. Thus, the surface strain distribution could be described with a piecewise linear or a piecewise nonlinear function. The discretization approach enabled piecewise integrations of the embedded-beam curvature equations to yield the Curved Displacement Transfer Functions, expressed in terms of embedded beam geometrical parameters and surface strains. By entering the surface strain data into the Displacement Transfer Functions, deflections along each embedded beam can be calculated at multiple points for mapping the overall structural deformed shapes. Finite-element linear and nonlinear analyses of a tapered cantilever tubular beam were performed to generate linear and nonlinear surface strains and the associated deflections to be used for validation. The shape prediction accuracies were then determined by comparing the theoretical deflections with the finiteelement- generated deflections. The results show that the newly developed Curved Displacement Transfer Functions are very accurate for shape predictions of structures under large geometrically nonlinear deformations.
displacement theory↗
Multibody modeling and verification
A summary of a ten week project on flexible multibody modeling, verification and control is presented. Emphasis was on the need for experimental verification. A literature survey was conducted for gathering information on the existence of experimental work related to flexible multibody systems. The first portion of the assigned task encompassed the modeling aspects of flexible multibodies that can undergo large angular displacements. Research in the area of modeling aspects were also surveyed, with special attention given to the component mode approach. Resulting from this is a research plan on various modeling aspects to be investigated over the next year. The relationship between the large angular displacements, boundary conditions, mode selection, and system modes is of particular interest. The other portion of the assigned task was the generation of a test plan for experimental verification of analytical and/or computer analysis techniques used for flexible multibody systems. Based on current and expected frequency ranges of flexible multibody systems to be used in space applications, an initial test article was selected and designed. A preliminary TREETOPS computer analysis was run to ensure frequency content in the low frequency range, 0.1 to 50 Hz. The initial specifications of experimental measurement and instrumentation components were also generated. Resulting from this effort is the initial multi-phase plan for a Ground Test Facility of Flexible Multibody Systems for Modeling Verification and Control. The plan focusses on the Multibody Modeling and Verification (MMV) Laboratory. General requirements of the Unobtrusive Sensor and Effector (USE) and the Robot Enhancement (RE) laboratories were considered during the laboratory development.
Wiens, Gloria J.↗
Modeling iterative reconstruction and displacement field in the large scale structure
The next generation of galaxy surveys like the Dark Energy Spectroscopic Instrument and Euclid will provide datasets orders of magnitude larger than anything available to date. Our ability to model nonlinear effects in late time matter perturbations will be a key to unlock the full potential of these datasets, and the area of initial condition reconstruction is attracting growing attention. Iterative reconstruction developed by Marcel Schmittfull et al. is a technique designed to reconstruct the displacement field from the observed galaxy distribution. The nonlinear displacement field and initial linear density field are highly correlated. Therefore, reconstructing the nonlinear displacement field enables us to extract the primordial cosmological information better than from the late time density field at the level of the two-point statistics. This paper will test to what extent the iterative reconstruction can recover the true displacement field and construct a perturbation theory model for the postreconstructed field. We model the iterative reconstruction process with Lagrangian perturbation theory (LPT) up to third order for dark matter in real space and compare it with N-body simulations. Here we find that the simulated iterative reconstruction does not converge to the nonlinear displacement field, and the discrepancy mainly appears in the shift term, i.e., the term correlated directly with the linear density field. On the contrary, our 3LPT model predicts that the iterative reconstruction should converge to the nonlinear displacement field. We discuss the sources of discrepancy, including numerical noise/artifacts on small scales, and present an ad hoc phenomenological model that improves the agreement.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Analysis of eccentric annular incompressible seals. I - A new solution using fast Fourier transforms for determining hydrodynamic force
A new analysis procedure is presented which solves for the flow variables of an incompressible-flow annular pressure seal in which the rotor has a large static displacement from the centered position. The analysis begins with a set of governing equations based on a turbulent bulk-flow model and Moody's friction equation. No simplification of these bulk-flow equations is required for the solution procedure. Perturbation of the flow variables yields a set of zeroth and first-order equations. The zeroth-order equations (which model the large static displacement) are integrated by means of an efficient new method which employs fast Fourier transforms. Further integration of the zeroth-order pressures yields the hydrodynamic reactive force. Predictions for the hydrodynamic forces from this analysis procedure are in excellent agreement with available experimental results.
Nelson, C. C.↗
The Influence of Interfacial Roughness on Fiber Sliding in Oxide Composites with La-Monazite Interphases
Room temperature debonding and sliding of La-Monazite coated fibers is assessed using a composite with a polycrystalline alumina matrix and fibers of several different single crystal (mullite, sapphire) and directionally solidified eutectic (Al2O3/Y3Al5O12 and Al2O3/Y-ZrO2) compositions. These fibers provide a range of residual stresses and interfacial roughnesses. Sliding occurred over a debond crack at the fiber-coating interface when the sliding displacement and surface roughness were relatively small. At large sliding displacements with relatively rough interfaces, the monazite coatings were deformed extensively by fracture, dislocations and occasional twinning, whereas the fibers were undamaged. Dense, fine-grained (10 nm) microstructures suggestive of dynamic recrystallization were also observed in the coatings. Frictional heating during sliding is assessed. The possibility of low temperature recrystallization is discussed in the light of the known resistance of monazite to radiation damage. The ability of La-Monazite to undergo plastic deformation relatively easily at low temperatures may be enabling for its use as a composite interface.
Davis, J. B.↗
Orbital-Dependent Coulomb Drag in Electron-Hole Bilayer Graphene Heterostructures
Here, we report Coulomb drag studies in an electron-hole bilayer graphene heterostructure in a magnetic field, where the orbital, spin, and valley degrees of freedom are lifted by the combined effects of exchange interaction, Zeeman energy, and a vertical displacement field. Our device enables the application of a large vertical displacement field across both layers. In addition to the well-established strong Coulomb drag between the Landau levels with an orbital quantum number 𝑁 = 0, we observe a Coulomb drag signal between the 𝑁 = 1 Landau levels under a suitable vertical displacement field. As the vertical displacement field increases further, the Coulomb drag signal between 𝑁 = 1 Landau levels weakens, and a Coulomb drag signal emerges between the 𝑁 = 0 and 𝑁 = 1 Landau levels. These findings suggest the important roles of the orbital index and the vertical displacement field in interlayer Coulomb interaction within the quantum Hall regime of coupled bilayer systems.
Landau levels↗
Backed Bending Actuator
Bending actuators of a proposed type would partly resemble ordinary bending actuators, but would include simple additional components that would render them capable of exerting large forces at small displacements. Like an ordinary bending actuator, an actuator according to the proposal would include a thin rectangular strip that would comprise two bonded layers (possibly made of electroactive polymers with surface electrodes) and would be clamped at one end in the manner of a cantilever beam. Unlike an ordinary bending actuator, the proposed device would include a rigid flat backplate that would support part of the bending strip against backward displacement; because of this feature, the proposed device is called a backed bending actuator. When an ordinary bending actuator is inactive, the strip typically lies flat, the tip displacement is zero, and the force exerted by the tip is zero. During activation, the tip exerts a transverse force and undergoes a bending displacement that results from the expansion or contraction of one or more of the bonded layers. The tip force of an ordinary bending actuator is inversely proportional to its length; hence, a long actuator tends to be weak. The figure depicts an ordinary bending actuator and the corresponding backed bending actuator. The bending, the tip displacement (d(sub t)), and the tip force (F) exerted by the ordinary bending actuator are well approximated by the conventional equations for the loading and deflection of a cantilever beam subject to a bending moment which, in this case, is applied by the differential expansion or contraction of the bonded layers. The bending, displacement, and tip force of the backed bending actuator are calculated similarly, except that it is necessary to account for the fact that the force F(sub b) that resists the displacement of the tip could be sufficient to push part of the strip against the backplate; in such a condition, the cantilever beam would be effectively shortened (length L*) and thereby stiffened and, hence, made capable of exerting a greater tip force for a given degree of differential expansion or contraction of the bonded layers. Taking all of these effects into account, the cantilever-beam equations show that F(sub b) would be approximately inversely proportional to d(sup 1/2) for d less than a calculable amount, denoted the transition displacement (dt). For d less than d(sub t), part of the strip would be pressed against the backplate. Therefore, the force F(sub b) would be very large for d at or near zero and would decrease as d increases toward d(sub t). At d greater than d(sub t), none of the strip would be pressed against the backplate and F(sub b) would equal the tip force F of the corresponding ordinary bending actuator. The advantage of the proposal is that a backed bending actuator could be made long to obtain large displacement when it encountered little resistance but it could also exert a large zero-displacement force, so that it could more easily start the movement of a large mass, throw a mechanical switch, or release a stuck mechanism.
Costen, Robert C.↗
GPS measurements of deformation associated with the 1987 Superstition Hills earthquake: Evidence for conjugate faulting
Large station displacements observed from Imperial Valley Global Positioning System (GPS) campaigns are attributed to the November 24, 1987 Superstition Hills earthquake sequence. Thirty sites from a 42 station GPS network established in 1986 were reoccupied during 1988 and/or 1990. Displacements at three sites within 3 kilometers of the surface rupture approach 0.5 m. Eight additional stations within 20 km of the seismic zone are displaced at least 10 cm. This is the first occurrence of a large earthquake (M(sub S) 6.6) within a preexisting GPS network. Best-fitting uniform slip models of rectangular dislocations in an elastic half-space indicate 130 + or - 8 cm right-lateral displacement along the northwest-trending Superstition Hills fault and 30 + or - 10 cm left-lateral displacement along the conjugate northeast-trending Elmore Ranch fault. The geodetic moments are 9.4 x 10(exp 25) dyne-cm and 2.3 x 10(exp 25) dyne-cm for the Superstition Hills and Elmore Ranch faults, respectively, consistent with teleseismic source parameters. The data also suggest the post seismic slip along the Superstition Hills fault is concentrated at shallow depths. Distributed slip solutions using Singular Value Decomposition indicate near uniform displacement along the Elmore Ranch fault and concentrated slip to the northwest and southeast along the Superstition Hills fault. A significant component of non-seismic displacement is observed across the Imperial Valley, which is attributed in part to interseismic plate-boundary deformation.
Larsen, Shawn↗
Global positioning system measurements of deformations associated with the 1987 Superstition Hills earthquake - Evidence for conjugate faulting
Large station displacements observed from Imperial Valley Global Positioning System (GPS) compaigns are attributed to the November 24, 1987 Superstition Hills earthquake sequence. Thirty sites from a 42 station GPS network established in 1986 were reoccupied during 1988 and/or 1990. Displacements at three sites within 3 kilometers of the surface rupture approach 0.5 m. Eight additional stations within 20 km of the seismic zone are displaced at least 10 cm. This is the first occurrence of a large earthquake (M(sub S) 6.6) within a preexisting GPS network. Best-fitting uniform slip models of rectangular dislocations in an elastic half-space indicate 130 + or - 8 cm right-lateral displacement along the northwest-trending Superstition Hills fault and 30 + or - 10 cm left-lateral displacement along the conjugate northeast-trending Elmore Ranch fault. The geodetic moments are 9.4 x 10 (exp 25) dyne-cm and 2.3 x 10 (exp 25) dyne-cm for the Superstition Hills and Elmore Ranch faults, respectively, consistent with teleseismic source parameters. The data also suggest the post seismic slip along the Superstition Hills fault is concentrated at shallow depths. Distributed slip solutions using Singular Value Decomposition indicate near uniform displacement along the Elmore Ranch fault and concentrated slip to the northwest and southeast along the Superstition Hills fault. A significant component of non-seismic displacement is observed across the Imperial Valley, which is attributed in part to interseismic plate-boundary deformation.
Larsen, Shawn↗
Tests of crustal divergence models for Aphrodite Terra, Venus
This paper discusses the characteristics of Aphrodite Terra, the highland region of Venus which is considered to be a likely site of mantle upwelling, active volcanism, and extensional tectonics, and examines the relation of these features to three alternative kinematic models for the interaction of mantle convection with the surface. These the 'vertical tectonics' model, in which little horizontal surface displacement results from mantle flow; the 'plate divergence' model, in which shear strain from large horizontal displacements is accommodated only in narrow zones of deformation; and the 'distributed deformation' model, in which strain from large horizontal motions is broadly accommodated. No convincing observational evidence was found to support the rigid-plate divergence, while the evidence of large-scale horizontal motions of Aphrodite argues against purely vertical tectonics. A model is proposed, involving a broad disruption of a thin lithosphere. In such a model, lineaments are considered to be surface manifestations of mantle convective flow.
Grimm, Robert E.↗