Showing papers on "Deformation (meteorology) published in 2009"

Two-dimensional digital image correlation for in-plane displacement and strain measurement: a review

Abstract: As a practical and effective tool for quantitative in-plane deformation measurement of a planar object surface, two-dimensional digital image correlation (2D DIC) is now widely accepted and commonly used in the field of experimental mechanics. It directly provides full-field displacements to sub-pixel accuracy and full-field strains by comparing the digital images of a test object surface acquired before and after deformation. In this review, methodologies of the 2D DIC technique for displacement field measurement and strain field estimation are systematically reviewed and discussed. Detailed analyses of the measurement accuracy considering the influences of both experimental conditions and algorithm details are provided. Measures for achieving high accuracy deformation measurement using the 2D DIC technique are also recommended. Since microscale and nanoscale deformation measurement can easily be realized by combining the 2D DIC technique with high-spatial-resolution microscopes, the 2D DIC technique should find more applications in broad areas.

A practical guide for analysis of nanoindentation data.

Abstract: Mechanical properties of biological materials are increasingly explored via nanoindentation testing. This paper reviews the modes of deformation found during indentation: elastic, plastic, viscous and fracture. A scheme is provided for ascertaining which deformation modes are active during a particular indentation test based on the load–displacement trace. Two behavior maps for indentation are presented, one in the viscous–elastic–plastic space, concerning homogeneous deformation, and one in the plastic versus brittle space, concerning the transition to fracture behavior when the threshold for cracking is exceeded. Best-practice methods for characterizing materials are presented based on which deformation modes are active; the discussion includes both nanoindentation experimental test options and appropriate methods for analyzing the resulting data.

The deformation of flexible PDMS microchannels under a pressure driven flow.

Abstract: Poly(dimethylsiloxane) (PDMS) microchannels are commonly used microfluidic structures that have a wide variety of biological testing applications, including the simulation of blood vessels to study the mechanics of vascular disease. In these studies in particular, the deformation of the channel due to the pressure inside is a critical parameter. We describe a method for using fluorescence microscopy to quantify the deformation of such channels under pressure driven flow. Additionally, the relationship between wall thickness and channel deformation is investigated. PDMS microchannels of varying top wall thickness were created using a soft lithography process. A solution of fluorescent dye is pumped through the channels at constant volume flow rates and illuminated. Pressure and fluorescence intensity are measured at five positions along the length of the channel. Fluorescence measurements are then used to determine deformation, using the linear relationship of dye layer thickness and intensity. A linear relationship between pressure and microchannel deformation is measured. Pressure drops and deformations closely correspond to values predicted by the model in most cases. Additionally, measured pressure drops are found to be up to 35% less than the pressure drop in a rigid-walled channel, and channel wall thickness is found to have an increasing effect as the channel wall thickness decreases.

A finite element method for transient analysis of concurrent large deformation and mass transport in gels

Abstract: A gel is an aggregate of polymers and solvent molecules. The polymers crosslink into a three-dimensional network by strong chemical bonds and enable the gel to retain its shape after a large deformation. The solvent molecules, however, interact among themselves and with the network by weak physical bonds and enable the gel to be a conduit of mass transport. The time-dependent concurrent process of large deformation and mass transport is studied by developing a finite element method. We combine the kinematics of large deformation, the conservation of the solvent molecules, the conditions of local equilibrium, and the kinetics of migration to evolve simultaneously two fields: the displacement of the network and the chemical potential of the solvent. The finite element method is demonstrated by analyzing several phenomena, such as swelling, draining and buckling. This work builds a platform to study diverse phenomena in gels with spatial and temporal complexity.

Semantic deformation transfer

Abstract: Transferring existing mesh deformation from one character to another is a simple way to accelerate the laborious process of mesh animation. In many cases, it is useful to preserve the semantic characteristics of the motion instead of its literal deformation. For example, when applying the walking motion of a human to a flamingo, the knees should bend in the opposite direction. Semantic deformation transfer accomplishes this task with a shape space that enables interpolation and projection with standard linear algebra. Given several example mesh pairs, semantic deformation transfer infers a correspondence between the shape spaces of the two characters. This enables automatic transfer of new poses and animations.

Deformation prediction and error compensation in multilayer milling processes for thin-walled parts

Abstract: Deformation prediction and error compensation are effective approaches to improve machining accuracy in milling thin-walled parts. In this paper, it is considered that the machining deformation of the previous layer will influence the nominal cutting depth of the current layer. Therefore, a dynamical model is established to predict the deformation in multilayer machining a thin-walled part. The coupling relation between cutting force and machining deformation is taken into account using iterative computation. The dynamical model is validated by comparing the simulation result with the experimental one. A new approach of active error compensation is proposed, in which the machining error is compensated at each layer. By comparing the simulation results of compensation at the last layer with the results of compensation at per-layer, a conclusion is drawn that compensation at per-layer makes smaller machining errors and the errors are more uniform.

Energy-based image deformation

Abstract: We present a general approach to shape deformation based on energy minimization, and applications of this approach to the problems of image resizing and 2D shape deformation. Our deformation energy generalizes that found in the prior art, while still admitting an efficient algorithm for its optimization. The key advantage of our energy function is the flexibility with which the set of "legal transformations" may be expressed; these transformations are the ones which are not considered to be distorting. This flexibility allows us to pose the problems of image resizing and 2D shape deformation in a natural way and generate minimally distorted results. It also allows us to strongly reduce undesirable foldovers or self-intersections. Results of both algorithms demonstrate the effectiveness of our approach.

Surface deformation electroactive polymer transducers

Abstract: Electroactive polymer transducers configured for surface mode deformation to provide thickness mode actuation.

How the Continents Deform: The Evidence From Tectonic Geodesy*

Abstract: Space geodesy now provides quantitative maps of the surface velocity field within tectonically active regions, supplying constraints on the spatial distribution of deformation, the forces that drive it, and the brittle and ductile properties of continental lithosphere. Deformation is usefully described as relative motions among elastic blocks and is block-like because major faults are weaker than adjacent intact crust. Despite similarities, continental block kinematics differs from global plate tectonics: blocks are much smaller, typically ∼100–1000 km in size; departures from block rigidity are sometimes measurable; and blocks evolve over ∼1–10 Ma timescales, particularly near their often geometrically irregular boundaries. Quantitatively relating deformation to the forces that drive it requires simplifying assumptions about the strength distribution in the lithosphere. If brittle/elastic crust is strongest, interactions among blocks control the deformation. If ductile lithosphere is the stronger, its fl...

Modeling deformable objects from a single depth camera

Abstract: We propose a novel approach to reconstruct complete 3D deformable models over time by a single depth camera, provided that most parts of the models are observed by the camera at least once. The core of this algorithm is based on the assumption that the deformation is continuous and predictable in a short temporal interval. While the camera can only capture part of a whole surface at any time instant, partial surfaces reconstructed from different times are assembled together to form a complete 3D surface for each time instant, even when the shape is under severe deformation. A mesh warping algorithm based on linear mesh deformation is used to align different partial surfaces. A volumetric method is then used to combine partial surfaces, fix missing holes, and smooth alignment errors. Our experiment shows that this approach is able to reconstruct visually plausible 3D surface deformation results with a single camera.

Microstructured Surfaces Cause Severe but Non‐Detrimental Deformation of the Cell Nucleus

Abstract: Surface features on the length scale of organelles allow their manipulation. Here, we present observations of an unexpected deformation of nuclei within cells growing on surfaces with micrometer‐sized pillars. Our results demonstrate that a microstructured surface can induce strong shape deformations in cells, without harmful consequences, and strongly suggest that these are limited to cancerous cells.

Ultrafine Grain Refinement of Biomedical Co-29Cr-6Mo Alloy during Conventional Hot-Compression Deformation

Abstract: In order to examine the microstructural evolution during hot-compression deformation of the biomedical Co-29Cr-6Mo (weight percent) alloy without the addition of Ni, hot-compression tests have been conducted at deformation temperatures ranging from 1050 °C to 1200 °C at various strain rates of 10−3 to 10 s−1. The grain refinement due to dynamic recrystallization (DRX) was identified under all deformation conditions by means of field-emission scanning electron microscopy/electron backscattered diffraction (FESEM/EBSD) and transmission electron microscopy (TEM) observations. Although the DRX grain size (d) of the deformed specimens considerably decreased with an increasing Zener–Hollomon (Z) parameter at strain rates ranging from 10−3 to 0.1 s−1, a grain size coarser than that predicted from the d-Z relation was obtained at strain rates of 1.0 and 10 s−1. An ultrafine-grained microstructure with a grain size of approximately 0.6 μm was obtained under deformation at 1050 °C at 0.1 s−1, from an initial grain size of 40 μm. The grain refinement to a submicron scale of biomedical Co-Cr-Mo alloys has been achieved with hot deformation by ~60 pct due to DRX, in which the bulging mechanism is not operative. The ultrafine grains obtained due to DRX without bulging is closely related to the considerably low stacking-fault energy (SFE) of the Co-Cr-Mo alloy at deformation temperatures.

Joint-aware manipulation of deformable models

Abstract: Complex mesh models of man-made objects often consist of multiple components connected by various types of joints. We propose a joint-aware deformation framework that supports the direct manipulation of an arbitrary mix of rigid and deformable components. First we apply slippable motion analysis to automatically detect multiple types of joint constraints that are implicit in model geometry. For single-component geometry or models with disconnected components, we support user-defined virtual joints. Then we integrate manipulation handle constraints, multiple components, joint constraints, joint limits, and deformation energies into a single volumetric-cell-based space deformation problem. An iterative, parallelized Gauss-Newton solver is used to solve the resulting nonlinear optimization. Interactive deformable manipulation is demonstrated on a variety of geometric models while automatically respecting their multi-component nature and the natural behavior of their joints.

Analysis of Ground Deformation Detected Using the SBAS-DInSAR Technique in Umbria, Central Italy

Abstract: Ground deformation affecting the Umbria region (central Italy) in the 9-year period from 1992 to 2000 was investigated through multi-temporal Differential Synthetic Aperture Radar Interferometry (DInSAR). For the purpose, the Small BAseline Subset (SBAS) technique was adopted, which allows studying the temporal evolution of the detected deformation at two spatial scales: a low-resolution (regional) scale, and a full-resolution (local) scale. For the analysis, SAR data acquired by the European Remote Sensing (ERS-1/2) satellites along ascending and descending orbits were used. The detected deformation was analysed to investigate its relevance to geophysical, geomorphologic, and human-induced processes that may result in hazardous conditions to the population of Umbria. Low-resolution deformation data were used to: (i) determine the amount of displacement caused by the Umbria-Marche earthquake sequence from September 1997 to April 1998 in the Foligno area, (ii) determine the number and percentage of the known landslides that can be monitored by the DInSAR technology in the investigated area, and (iii) identify and measure subsidence induced by exploitation of a confined aquifer in the Valle Umbra. Results indicate that earthquakes moved through the Foligno area westwards up to 3.9 cm and with an uplift reaching 1.7 cm. Intersection in a GIS of the low-resolution deformation maps with a detailed landslide inventory map allowed the determination that the portion of landslides that can be monitored by the SBAS-DInSAR technique in Umbria ranges from 2.7% to 3.4%, and the percentage of the total landslide area ranges from 10.4% to 12.8%. In the Valle Umbra, a dependency was found between the time and the amount of detected ground deformation, and the record of water withdrawal. The full-resolution deformation data were used to investigate the movement of the Ivancich landslide, in the Assisi Municipality. Joint analysis of the spatial and the temporal characteristics of the ground displacement allowed the formulation of a hypothesis on the landslide geometry and deformation pattern.

Nature of deformation of sandy bed forms

Abstract: [1] We explore a stochastic component of topographic evolution of sandy river beds and its relationship to bed material flux. The behavior of trains of mobile bed forms can be decomposed into two independent constituents, translation and deformation. Translation is the mean downstream migration of the bed at velocity that defines the Lagrangian reference frame of the bed. Deformation is the sum of all changes to the bed's topographic profile measured from within the bed's moving reference frame. The occurrence of deformation leads to exponential decorrelation of bed topography that is in dynamic equilibrium with flow conditions. For the field and laboratory data sets used, correlation decays to 0.5 by the time the bed translates 40% and 360% of the mean bed form length, respectively. Proportions of bed material flux responsible for translation and deformation can be straightforwardly calculated. Translation flux is measured using the traditional bed form-bed load equation. Deformation flux is determined by excess topographic change scaled by the ratio of horizontal sediment velocity to fall velocity. Deformation represents the sediment exchanged between bed load and suspended load. Because deformation is a stochastic process with zero mean, the apparent rate of deformation decreases as a function of time interval between bed surveys. For the field case, deformation accounts for 40% of bed material flux while it is only 1% of the flux in the laboratory.

Evaluation of high-resolution sea ice models on the basis of statistical and scaling properties of Arctic sea ice drift and deformation

Abstract: Sea ice drift and deformation from models are evaluated on the basis of statistical and scaling properties. These properties are derived from two observation data sets: the RADARSAT Geophysical Processor System (RGPS) and buoy trajectories from the International Arctic Buoy Program (IABP). Two simulations obtained with the Louvain-la-Neuve Ice Model (LIM) coupled to a high-resolution ocean model and a simulation obtained with the Los Alamos Sea Ice Model (CICE) were analyzed. Model ice drift compares well with observations in terms of large-scale velocity field and distributions of velocity fluctuations although a significant bias on the mean ice speed is noted. On the other hand, the statistical properties of ice deformation are not well simulated by the models: (1) The distributions of strain rates are incorrect: RGPS distributions of strain rates are power law tailed, i.e., exhibit "wild randomness," whereas models distributions remain in the Gaussian attraction basin, i.e., exhibit "mild randomness." (2) The models are unable to reproduce the spatial and temporal correlations of the deformation fields: In the observations, ice deformation follows spatial and temporal scaling laws that express the heterogeneity and the intermittency of deformation. These relations do not appear in simulated ice deformation. Mean deformation in models is almost scale independent. The statistical properties of ice deformation are a signature of the ice mechanical behavior. The present work therefore suggests that the mechanical framework currently used by models is inappropriate. A different modeling framework based on elastic interactions could improve the representation of the statistical and scaling properties of ice deformation.

Material properties for process simulation

Abstract: This paper reviews the recent developments in material property modelling and its applications in processing simulation. Many material properties needed by process simulation can now be readily provided, such as the solidification properties and high temperature stress–strain curves. The solidification properties are affected by changes in composition within the specification range of an alloy; such changes in properties then affect casting simulation results. The mechanical properties are calculated by considering two competing deformation mechanisms (dominated by either dislocation glide or dislocation climb), with automatic selection of the dominant mechanism. Sample calculations are given for a variety of engineering alloys, including steels, aluminum, titanium, and nickel-based superalloys. The material properties data calculated can now be passed directly into commercial computer-aided engineering packages for casting and deformation simulation.