Showing papers on "Deformation (meteorology) published in 2013"

Universal deformation of soft substrates near a contact line and the direct measurement of solid surface stresses.

Abstract: Droplets deform soft substrates near their contact lines. Using confocal microscopy, we measure the deformation of silicone gel substrates due to glycerol and fluorinated-oil droplets for a range of droplet radii and substrate thicknesses. For all droplets, the substrate deformation takes a universal shape close to the contact line that depends on liquid composition, but is independent of droplet size and substrate thickness. This shape is determined by a balance of interfacial tensions at the contact line and provides a novel method for direct determination of the surface stresses of soft substrates. Moreover, we measure the change in contact angle with droplet radius and show that Young's law fails for small droplets when their radii approach an elastocapillary length scale. For larger droplets the macroscopic contact angle is constant, consistent with Young's law.

Giant voltage-induced deformation in dielectric elastomers near the verge of snap-through instability

Abstract: Dielectric elastomers are capable of large voltage-induced deformation, but achieving such large deformation in practice has been a major challenge due to electromechanical instability and electric breakdown. The complex nonlinear behavior suggests an important opportunity: electromechanical instability can be harnessed to achieve giant voltage-induced deformation. We introduce the following principle of operation: place a dielectric elastomer near the verge of snap-through instability, trigger the instability with voltage, and bend the snap-through path to avert electric breakdown. We demonstrate this principle of operation with a commonly used experimental setup—a dielectric membrane mounted on a chamber of air. The behavior of the membrane can be changed dramatically by varying parameters such as the initial pressure in the chamber, the volume of the chamber, and the prestretch of the membrane. We use a computational model to analyze inhomogeneous deformation and map out bifurcation diagrams to guide the experiment. With suitable values of the parameters, we obtain giant voltage-induced expansion of area by 1692%, far beyond the largest value reported in the literature.

A domain decomposition approach to implementing fault slip in finite-element models of quasi-static and dynamic crustal deformation

Abstract: [1] We employ a domain decomposition approach with Lagrange multipliers to implement fault slip in a finite-element code, PyLith, for use in both quasi-static and dynamic crustal deformation applications. This integrated approach to solving both quasi-static and dynamic simulations leverages common finite-element data structures and implementations of various boundary conditions, discretization schemes, and bulk and fault rheologies. We have developed a custom preconditioner for the Lagrange multiplier portion of the system of equations that provides excellent scalability with problem size compared to conventional additive Schwarz methods. We demonstrate application of this approach using benchmarks for both quasi-static viscoelastic deformation and dynamic spontaneous rupture propagation that verify the numerical implementation in PyLith.

Development of 3rd generation AHSS with medium Mn content alloying compositions

Abstract: In this paper, four different steel compositions, centered on Mn as the main alloying element, are designated as candidates for Third Generation AHSS grades. The design of these steels is based on controlling the deformation behavior of the retained austenite. Thus, heat treatment process parameters are determined in order to obtain different amounts and morphologies of retained austenite. The evolution of the microstructure, during processing as well as deformation, is characterized by using optical, electron microscopy techniques and mechanical tests. The effect of alloy composition and processing parameters on the deformation mechanisms of these steels is discussed.

Comparison of geomechanical deformation induced by megatonne-scale CO2 storage at Sleipner, Weyburn, and In Salah

Abstract: Geological storage of CO2 that has been captured at large, point source emitters represents a key potential method for reduction of anthropogenic greenhouse gas emissions. However, this technology will only be viable if it can be guaranteed that injected CO2 will remain trapped in the subsurface for thousands of years or more. A significant issue for storage security is the geomechanical response of the reservoir. Concerns have been raised that geomechanical deformation induced by CO2 injection will create or reactivate fracture networks in the sealing caprocks, providing a pathway for CO2 leakage. In this paper, we examine three large-scale sites where CO2 is injected at rates of ∼1 megatonne/y or more: Sleipner, Weyburn, and In Salah. We compare and contrast the observed geomechanical behavior of each site, with particular focus on the risks to storage security posed by geomechanical deformation. At Sleipner, the large, high-permeability storage aquifer has experienced little pore pressure increase over 15 y of injection, implying little possibility of geomechanical deformation. At Weyburn, 45 y of oil production has depleted pore pressures before increases associated with CO2 injection. The long history of the field has led to complicated, sometimes nonintuitive geomechanical deformation. At In Salah, injection into the water leg of a gas reservoir has increased pore pressures, leading to uplift and substantial microseismic activity. The differences in the geomechanical responses of these sites emphasize the need for systematic geomechanical appraisal before injection in any potential storage site.

Effects of geometric and material nonlinearities on tunable band gaps and low-frequency directionality of phononic crystals

Abstract: We investigate the effects of geometric and material nonlinearities introduced by deformation on the linear dynamic response of two-dimensional phononic crystals. Our analysis not only shows that deformation can be effectively used to tune the band gaps and the directionality of the propagating waves, but also reveals how geometric and material nonlinearities contribute to the tunable response of phononic crystals. Our numerical study provides a better understanding of the tunable response of phononic crystals and opens avenues for the design of systems with optimized properties and enhanced tunability.

Flexible display apparatus and control method thereof

Abstract: A flexible display apparatus is provided. The flexible display apparatus includes: a display configured to display an object on a screen; an actuator configured to provide shape deformation to the display; and a controller configured to determine deformation information for reconfiguring and displaying the object, control the actuator to provide the shape deformation according to the determined deformation information, and control the display to reconfigure the displayed object and display the reconfigured object.

Flexible display apparatus and operating method thereof

Abstract: A flexible display apparatus is provided. The flexible display apparatus includes a display, a sensor which senses shape deformation of the display, a storage which, if a shape deformation is sensed, stores operation state information of a first operation state of the flexible display apparatus prior to the first shape deformation being performed, and a controller which performs a function corresponding to the first shape deformation if a second shape deformation different from the first shape deformation is sensed, returns to the first operation state according to the operation state information stored in the storage.

A Domain Decomposition Approach to Implementing Fault Slip in Finite-Element Models of Quasi-static and Dynamic Crustal Deformation

Abstract: We employ a domain decomposition approach with Lagrange multipliers to implement fault slip in a finite-element code, PyLith, for use in both quasi-static and dynamic crustal deformation applications. This integrated approach to solving both quasi-static and dynamic simulations leverages common finite-element data structures and implementations of various boundary conditions, discretization schemes, and bulk and fault rheologies. We have developed a custom preconditioner for the Lagrange multiplier portion of the system of equations that provides excellent scalability with problem size compared to conventional additive Schwarz methods. We demonstrate application of this approach using benchmarks for both quasi-static viscoelastic deformation and dynamic spontaneous rupture propagation that verify the numerical implementation in PyLith.

Characterization of flow stress for commercially pure titanium subjected to electrically assisted deformation

Abstract: Uniaxial tension tests were conducted on thin commercially pure titanium sheets subjected to electrically-assisted deformation using a new experimental setup to decouple thermal-mechanical and possible electroplastic behavior. The observed absence of stress reductions for specimens air-cooled to near room temperature motivated the need to reevaluate the role of temperature on modeling the plastic behavior of metals subjected to electrically-assisted deformation, an item that is often overlooked when invoking electroplasticity theory. As a result, two empirical constitutive models, a modified-Hollomon and the Johnson-Cook models of plastic flow stress, were used to predict the magnitude of stress reductions caused by the application of constant DC current and the associated Joule heating temperature increase during electrically-assisted tension experiments. Results show that the thermal-mechanical coupled models can effectively predict the mechanical behavior of commercially pure titanium in electrically-assisted tension and compression experiments.Copyright © 2013 by ASME

Free vibration analysis of functionally graded shells by a higher-order shear deformation theory and radial basis functions collocation, accounting for through-the-thickness deformations

Abstract: This paper deals with free vibration problems of functionally graded shells. The analysis is performed by radial basis functions collocation, according to a higher-order shear deformation theory that accounts for through-the-thickness deformation. The equations of motion and the boundary conditions are obtained by Carrera’s Unified Formulation resting upon the principle of virtual work, and further interpolated by collocation with radial basis functions. Numerical results include spherical as well as cylindrical shell panels with all edges clamped or simply supported and demonstrate the accuracy of the present approach.

Rheology and Non-Newtonian Fluids

Abstract: Classification of Fluids.- Flow Phenomena.- Basic Equations in Fluid Mechanics.- Deformation.- Material.- Generalized Newtonian.- Linearly Viscoelastic.- Advanced Fluid Models.- Problems.

Evolution of activation energy during hot deformation of AA7150 aluminum alloy

Abstract: The hot deformation behavior of a homogenized AA7150 aluminum alloy was studied in compression tests conducted at various temperatures (573–723 K) and strain rates (0.001–10 s −1 ). The flow stress behavior and microstructural evolution were observed during the hot deformation process. A revised Sellars’ constitutive equation was proposed, which considered the effects of the deformation temperature and strain rate on the material variables and which provided an accurate estimate of the hot deformation behavior of the AA7150 aluminum alloy. The results revealed that the activation energy for the hot deformation of the AA7150 aluminum alloy is not a constant value but rather varies as a function of the deformation conditions. The activation energy for hot deformation decreased with increasing deformation temperature and strain rate. The peak flow stresses under various deformation conditions were predicted by a revised constitutive equation and correlated with the experimental data with excellent accuracy.

Model-Free Visually Servoed Deformation Control of Elastic Objects by Robot Manipulators

Abstract: Despite the recent progress in physically interactive and surgical robotics, the active deformation of compliant objects remains an open problem. The main obstacle to its implementation comes from the difficulty to identify or estimate the object's deformation model. In this paper, we propose a novel vision-based deformation controller for robot manipulators interacting with unknown elastic objects. We derive a new dynamic-state feedback velocity control law using the passivity-based framework. Our method exploits visual feedback to estimate the deformation Jacobian matrix in real time, avoiding any model identification steps. We prove that even in the presence of inexact estimations, the closed-loop dynamical system ensures input-to-state stability (i.e., full dissipativity) with respect to external disturbances. An experimental study with several deformation tasks is presented to validate the theory.

Monitoring of long‐term static deformation data of Fei‐Tsui arch dam using artificial neural network‐based approaches

Abstract: SUMMARY The objective of this paper is to develop methods for extracting trends from long-term static deformation data of a dam and try to set an early warning threshold level on the basis of the results of analyses. The static deformation of a dam is mainly influenced by the water pressure (or water level) of the dam and the temperature distribution of the dam body. The relationship among the static deformation, the water level, and the temperature distribution of the dam body is complex and unknown; therefore, it can be approximated by static neural networks. Although the static deformation almost has no change during a very short time, it changes with time for long-term continuous observation. Therefore, long-term static deformation can be approximated dynamically using dynamic neural networks. Moreover, static deformation data is rich, but information is poor. Linear and nonlinear principal component analyses are particularly well suited to deal with this kind of problem. With these reasons, different approaches are applied to extract features of the long-term daily based static deformations of the Fei-Tsui arch dam (Taiwan). The methods include the static neural network, the dynamic neural network, principal component analysis, and nonlinear principal component analysis. Discussion of these methods is made. By using these methods, the residual deformation between the estimated and the recorded data are generated, and through statistical analysis, the threshold level of the static deformation of a dam can be determined on the basis of the normality assumption of the residual deformation. Copyright © 2011 John Wiley & Sons, Ltd.

Plasticity: Modeling & Computation

Abstract: Motivations and Scope.- One-Dimensional Problem.- J2 Plasticity.- Isotropic Functions.- Finite Deformation.- Cap Models.- Discontinuities.- Crystal Plasticity.- Bifurcation.

Structure of orogenic belts controlled by lithosphere age

Abstract: The influence of inherited tectonic-plate strength on the structure of mountain belts is debated. Analysis of geological data collected from mountain belts worldwide shows that the style and amount of deformation in a mountain range are strongly influenced by the age and strength of the colliding plates.