Showing papers on "Deformation (meteorology) published in 2017"

Adsorption-induced deformation of nanoporous materials—A review

Abstract: When a solid surface accommodates guest molecules, they induce noticeable stresses to the surface and cause its strain. Nanoporous materials have high surface area and, therefore, are very sensitive to this effect called adsorption-induced deformation. In recent years, there has been significant progress in both experimental and theoretical studies of this phenomenon, driven by the development of new materials as well as advanced experimental and modeling techniques. Also, adsorption-induced deformation has been found to manifest in numerous natural and engineering processes, e.g., drying of concrete, water-actuated movement of non-living plant tissues, change of permeation of zeolite membranes, swelling of coal and shale, etc. In this review, we summarize the most recent experimental and theoretical findings on adsorption-induced deformation and present the state-of-the-art picture of thermodynamic and mechanical aspects of this phenomenon. We also reflect on the existing challenges related both to the f...

Review of Relationship Between Particle Deformation, Coating Microstructure, and Properties in High-Pressure Cold Spray

Abstract: In the cold spray (CS) process, deposits are produced by depositing powder particles at high velocity onto a substrate. Powders deposited by CS do not undergo melting before or upon impacting the substrate. This feature makes CS suitable for deposition of a wide variety of materials, most commonly metallic alloys, but also ceramics and composites. During processing, the particles undergo severe plastic deformation and create a more mechanical and less metallurgical bond with the underlying material. The deformation behavior of an individual particle depends on multiple material and process parameters that are classified into three major groups—powder characteristics, geometric parameters, and processing parameters, each with their own subcategories. Changing any of these parameters leads to evolution of a different microstructure and consequently changes the mechanical properties in the deposit. While cold spray technology has matured during the last decade, the process is inherently complex, and thus, the effects of deposition parameters on particle deformation, deposit microstructure, and mechanical properties remain unclear. The purpose of this paper is to review the parameters that have been investigated up to now with an emphasis on the existent relationships between particle deformation behavior, microstructure, and mechanical properties of various cold spray deposits.

Deformation Microstructure and Deformation-Induced Martensite in Austenitic Fe-Cr-Ni Alloys Depending on Stacking Fault Energy

Abstract: The deformation microstructure of austenitic Fe-18Cr-(10-12)Ni (wt pct) alloys with low stacking fault energies, estimated by first-principles calculations, was investigated after cold rolling The

High-temperature tensile deformation behavior and microstructure evolution of Ti55 titanium alloy

Abstract: High temperature tensile and electron backscatter diffraction (EBSD) techniques were combined to perform a systematic investigation for the hot deformation behavior and microstructure evolution of the Ti55 alloy Under temperatures ranging from 885 to 935 °C and stain rates of 83×10−4 s−1−133×10−2 s−1, all the flow curves of the Ti55 alloy exhibit similar behaviors: after reaching the peak flow stress, the curves enter into a softening stage and then remain a steady level, where the maximum superplastic elongation of 987% indicates good superplasticity Detailed microstructure characterizations under different deformation stages show that the grain aspect ratios decrease greatly and the fractions of high angle boundaries (>15°) increase rapidly at the softening stage These observations are attributed to the dynamic recrystallization, in which low angle grain boundaries (

Three-Dimensional-Printed Multistable Mechanical Metamaterials With a Deterministic Deformation Sequence

Abstract: Multistable mechanical metamaterials are materials that have multiple stable configurations. The geometrical changes caused by the transition of the metamaterial from one stable state to another, could be exploited to obtain multifunctional and programmable materials. As the stimulus amplitude is varied, a multistable metamaterial goes through a sequence of stable configurations. However, this sequence (which we will call the deformation sequence) is unpredictable if the metamaterial consists of identical unit cells. This paper proposes to use small variations in the unit cell geometry to obtain a deterministic deformation sequence for one type of multistable metamaterial that consists of bistable unit cells. Based on an analytical model for a single unit cell and on the minimization of the total strain energy, a rigorous theoretical model is proposed to analyze the nonlinear mechanics of this type of metamaterials and to inform the designs. The proposed theoretical model is able to accurately predict the deformation sequence and the stress–strain curves that are observed in the finite-element simulations with an elastic constitutive model. A deterministic deformation sequence that matches the sequence predicted by the theory and finite-element simulations is obtained in experiments with 3D-printed samples. Furthermore, an excellent quantitative agreement between simulations and experiments is obtained once a viscoelastic constitutive model is introduced in the finite-element model. [DOI: 10.1115/1.4034706]

Deformation of an amorphous polymer during the fused-filament-fabrication method for additive manufacturing

Abstract: Three-dimensional (3D) printing is rapidly becoming an effective means of prototyping and creating custom consumer goods. The most common method for printing a polymer melt is fused filament fabrication (FFF) and involves extrusion of a thermoplastic material through a heated nozzle; the material is then built up layer-by-layer to fabricate a 3D object. Under typical printing conditions, the melt experiences high strain rates within the FFF nozzle, which are able to significantly stretch and orient the polymer molecules. In this paper, we model the deformation of an amorphous polymer melt during the extrusion process, where the fluid must make a 90° turn. The melt is described by a modified version of the Rolie–Poly model, which allows for flow-induced changes in the entanglement density. The complex polymer configurations in the cross section of a printed layer are quantified and visualized. The deposition process involving the corner flow geometry dominates the deformation and significantly disentangles the melt.

Severe Morphological Deformation of Spiro-OMeTAD in (CH3NH3)PbI3 Solar Cells at High Temperature

Abstract: The hole transport material, spiro-OMeTAD, in MAPbI3 perovskite solar cells undergoes severe morphological deformation at high temperature, showing big voids in the layer when the devices are heated at 80 °C and above. It is puzzling that the voids emerge only in the area where the spiro-OMeTAD is capped with Au film and only in the case where the HTM contains both LiTFSI and TBP as additives.

Particle breakage and deformation of carbonate sands with wide range of densities during compression loading process

Abstract: In this technical note, evolutions of the particle size distribution, particle breakage, volume deformation and input work of carbonate sands with varying relative densities were investigated through performing a series of one-dimensional compression tests. Loading stress levels ranged from 0.1 to 3.2 MPa. It was found that the initial relative density could greatly affect the magnitude of particle size distribution, particle breakage, volume deformation and input work. Particularly, it was observed that the specimen at a lower relative density underwent much more particle breakage than that at a higher relative density. This could be attributed to the change of the coordination number with the initial density. However, a unique linear relationship between the particle breakage and input work per volume could be obtained, which is independent of the initial relative density.

India plate angular velocity and contemporary deformation rates from continuous GPS measurements from 1996 to 2015.

Abstract: We estimate a new angular velocity for the India plate and contemporary deformation rates in the plate interior and along its seismically active margins from Global Positioning System (GPS) measurements from 1996 to 2015 at 70 continuous and 3 episodic stations. A new India-ITRF2008 angular velocity is estimated from 30 GPS sites, which include stations from western and eastern regions of the plate interior that were unrepresented or only sparsely sampled in previous studies. Our newly estimated India-ITRF2008 Euler pole is located significantly closer to the plate with ~3% higher angular velocity than all previous estimates and thus predicts more rapid variations in rates and directions along the plate boundaries. The 30 India plate GPS site velocities are well fit by the new angular velocity, with north and east RMS misfits of only 0.8 and 0.9 mm/yr, respectively. India fixed velocities suggest an approximate of 1–2 mm/yr intra-plate deformation that might be concentrated along regional dislocations, faults in Peninsular India, Kachchh and Indo-Gangetic plain. Relative to our newly-defined India plate frame of reference, the newly estimated velocities for 43 other GPS sites along the plate margins give insights into active deformation along India’s seismically active northern and eastern boundaries.

The effect of grain boundary water on deformation mechanisms and rheology of rocksalt during long-term deformation

Abstract: Reliable modeling of the deformation of rocksalt under the very low strain rates characterizing long term engineering conditions or natural halokinesis requires extrapolation of experimentally-derived flow laws to rates much lower than those attainable in the laboratory. This extrapolation must be based on an understanding of the microscale deformation mechanisms operating under these conditions, from studies of natural laboratories. The engineering creep laws generally used in the salt mining industry are based on dislocation creep processes quantified in laboratory experiments of necessarily limited duration. However, a large body of evidence clearly demonstrates that under conditions of long-term deformation, grain boundary dissolution-precipitation processes, such as solution-precipitation creep (or “pressure solution”) and dynamic recrystallization, play a significant role. In this contribution, we briefly review the microphysics of grain boundary water related, solution-precipitation processes in halite, together with the flow behaviour associated with these processes, and we discuss the contribution of these mechanisms to the strain rate during long-term creep.

Flexibles: Deformation-Aware 3D-Printed Tangibles for Capacitive Touchscreens

Abstract: We introduce Flexibles: 3D-printed flexible tangibles that are deformation-aware and operate on capacitive touchscreens. Flexibles add expressive deformation input to interaction with on-screen tangibles. Based on different types of deformation mapping, we contribute a set of 3D-printable mechanisms that capture pressing, squeezing, and bending input with multiple levels of intensities. They can be integrated into 3D printed objects with custom geometries and on different locations. A Flexible is printed in a single pass on a consumer-level 3D printer without requiring further assembly. Through a series of interactive prototypes, example applications and a technical evaluation, we show the technical feasibility and the wide applicability of Flexibles.

Application of InSAR Techniques to an Analysis of the Guanling Landslide

Abstract: On the afternoon of 28 June 2010, an enormous landslide occurred in the Gangwu region of Guanling County, Guizhou Province. In order to better understand the mechanism of the Guanling landslide, archived ALOS/PALSAR data was used to acquire the deformation prior to the landslide occurrence through stacking and time-series InSAR techniques. First, the deformation structure from InSAR was compared to the potential creep bodies identified using the optical remote sensing data. A strong consistency between the InSAR detected deformed regions and the creep bodies detected from optical remote sensing images was achieved. Around 10 creep bodies were suffering from deformation. In the source area, the maximum pre-slide mean deformation rate along the slope direction reached 160 mm/year, and the uncertainty of the deformation rates ranged from 15 to 34 mm/year. Then, the pre-slide deformation at the source area was analyzed in terms of the topography, geological structure, and historical rainfall records. Through observation and analysis, the deformation pattern of one creep body located within the source area can be segmented into three sections: a creeping section in the front, a locking section in the middle, and a cracking section in the rear. These sections constitute one of the common landslide modes seen in the south-west of China. This study concluded that a sudden shear failure in the locking segment of one creeping body located within the source area was caused by a strong rainstorm, which triggered the Guanling landslide.

Compound dislocation models (CDMs) for volcano deformation analyses

Abstract: Volcanic crises are often preceded and accompanied by volcano deformation caused by magmatic and hydrothermal processes. Fast and efficient model identification and parameter estimation techniques for various sources of deformation are crucial for process understanding, volcano hazard assessment and early warning purposes. As a simple model that can be a basis for rapid inversion techniques, we present a compound dislocation model (CDM) that is composed of three mutually orthogonal rectangular dislocations (RDs). We present new RD solutions, which are free of artefact singularities and that also possess full rotational degrees of freedom. The CDM can represent both planar intrusions in the near field and volumetric sources of inflation and deflation in the far field. Therefore, this source model can be applied to shallow dikes and sills, as well as to deep planar and equidimensional sources of any geometry, including oblate, prolate and other triaxial ellipsoidal shapes. In either case the sources may possess any arbitrary orientation in space. After systematically evaluating the CDM, we apply it to the co-eruptive displacements of the 2015 Calbuco eruption observed by the Sentinel-1A satellite in both ascending and descending orbits. The results show that the deformation source is a deflating vertical lens-shaped source at an approximate depth of 8 km centred beneath Calbuco volcano. The parameters of the optimal source model clearly show that it is signicantly different from an isotropic point source or a single dislocation model. The Calbuco example reflects the convenience of using the CDM for a rapid inter- pretation of deformation data.

Apparatuses and methods for monitoring tendons of steerable catheters

Abstract: Methods and apparatuses for detecting tension on a tendon and/or mechanical deformation (e.g., breakage) of one or more steering tendon of a steerable and flexible articulating device. Theses apparatuses may have one or more tendons that are each electrically conductive and configured to steer the apparatus when tension is applied to the proximal end of the tendon. Tension and/or breakage (or other deformation) of one or more of these tendons may be detected by monitoring the electrical resistance of the tendons.

Performance evaluation of warping characteristic of fused deposition modelling process

Abstract: In recent years, fused deposition modelling (FDM) is gaining more popularity due to its distinct advantages in terms of cost-effectiveness, lower build times, and flexibility. Compared to other 3-D printing processes such as SLS, this process does not use any kind of high-intensity laser power to build functional parts out of CAD models and, hence, makes the process much simpler, cheaper, and adaptable. Past studies reveal that productivity of the FDM process can be further increased by effectively controlling its process parameters such as layer thickness, part orientation, extrusion temperature, and so on. In this regard, many authors have investigated the optimal parameter settings for improving part strength, surface finish, wear, and fatigue properties of FDM made prototypes. However, warping performance behavior has got very recent attention due to complex heat transfer mechanism involved during this process. Experimental investigations are necessary to understand the deformation behavior of prototypes. In addition, the quantification and optimization of warp deformation along with dimensional error poses a challenging multi-objective optimization problem. Therefore, this work proposes an evolutionary system identification (SI) approach to explicitly quantify the warp deformation and dimensional error based on the four inputs such as line width compensation, extrusion velocity, filling velocity, and layer thickness of FDM prototypes. The two models’ performance analysis comprising of error metrics evaluation, cross-validation, and hypothesis tests is performed to validate its robustness. The analysis concluded that the layer thickness and extrusion velocity influence the warp deformation and, while filling velocity and line width compensation, influences the dimensional error the most.

2D cellular automaton simulation of hot deformation behavior in a Ni-based superalloy under varying thermal-mechanical conditions

Abstract: A 2D cellular automaton model (CA) is developed to predict the hot deformation behavior of a Ni-based superalloy over a wide range of thermal-mechanical conditions. Relationships between the model parameters (work hardening parameter, dynamic recovery parameter, nucleation rate, and grain boundary mobility) and the thermal-mechanical conditions are established. The developed CA model is further employed to study the hot deformation behavior of the studied superalloy under varying thermal-mechanical conditions. These varying conditions include the sudden change of strain rate and gradual change of deformation temperature. The evolutions of flow stress, average grain size and fraction of dynamic recrystallization (DRX) under the varying thermal-mechanical conditions are predicted. The reliability of the simulated results is verified by experimental results. It is found that the predicted results under varying thermal-mechanical conditions gradually approach those under constant hot deformed conditions. i.e., constant deformation temperature and strain rate. The varying thermal-mechanical condition makes the complex evolution of dislocation density, fraction of DRX, and average grain size. Additionally, a pseudo-metadynamic recrystallization is found. The pseudo-metadynamic recrystallization is a temporary suspension of dynamic recrystallization during a large and rapid increase of strain rate as a consequence of nucleation inhibition. It resembles metadynamic recrystallization, except that the pseudo-metadynamic recrystallization occurs when the hot deformation is still underway.

In–plane dynamic crushing behavior and energy absorption of honeycombs with a novel type of multi-cells

Abstract: In order to pursue better crashworthiness and higher energy absorption efficiency, a new type of multi-cell honeycomb (quadri-arc) was designed and followed by a series of numerical studies on in-plane dynamic crushing behavior and energy absorption property under different impact loading. Meanwhile, simulations of a regular circular single-cell honeycomb were also conducted as comparisons. Three distinct deformation modes were identified from the observation of deformation profiles: quasi-static, transition and dynamic, respectively. Simulations indicate that deformation modes are not only influenced by impact velocity but also sensitive to relative density of the honeycomb, based on which a deformation map was summarized. Furthermore, the plateau stress and energy absorption of the quadri-arc honeycomb as well as the circular honeycomb were explored and compared, during which effects of impact velocity and relative density of the honeycomb were discussed in detail. The results show that a much higher plateau stress and better energy absorption efficiency for the quadri-arc honeycomb are predicted compared to the circular honeycomb, especially in the quasi-static case. The investigation suggests that design of the quadri-arc multi-cell will enhance the crashworthiness and energy absorption capacity of honeycombs.

Effects of Metamorphism and Deformation on the Coal Macromolecular Structure by Laser Raman Spectroscopy

Abstract: Metamorphism and deformation significantly affect the macromolecular structure of coal. In this study, experiments were conducted using coal samples with different metamorphic degrees and deformation types from different regions of Hebei, Henan, Shanxi, and Anhui province, followed by laser Raman spectral analysis. The results indicated that the Raman spectrum of all coal samples consist of two characteristic peaks, namely the D peak and the G peak, ranging from 1336.7 cm–1 to 1360 cm–1 and from 1591.2 cm–1 to 1600.6 cm–1, respectively. Simultaneously, with the metamorphic degree of coal increasing, certain change rules were observed in both strong and weak tectonically deformed coals: G and D peaks were gradually separated and the sharpness of these peaks was clearly enhanced. In addition, the D-peak position, full width at half maximum for the G-peak (fwhm-G), and the intensity ratio between the D and G-peaks (ID/IG) decreased, but the G-peak position and d(G–D) values increased, while the analysis resu...