Showing papers on "Deformation (meteorology) published in 2021"

Fracture, fatigue, and friction of polymers in which entanglements greatly outnumber cross-links.

Abstract: In gels and elastomers, the role of entanglements on deformation has been studied, but their effects on fracture, fatigue, and friction are less well understood. In this study, we synthesized polym...

Amorphization in extreme deformation of the CrMnFeCoNi high-entropy alloy

Abstract: Ever-harsher service conditions in the future will call for materials with increasing ability to undergo deformation without sustaining damage while retaining high strength. Prime candidates for these conditions are certain high-entropy alloys (HEAs), which have extraordinary work-hardening ability and toughness. By subjecting the equiatomic CrMnFeCoNi HEA to severe plastic deformation through swaging followed by either quasi-static compression or dynamic deformation in shear, we observe a dense structure comprising stacking faults, twins, transformation from the face-centered cubic to the hexagonal close-packed structure, and, of particular note, amorphization. The coordinated propagation of stacking faults and twins along {111} planes generates high-deformation regions, which can reorganize into hexagonal packets; when the defect density in these regions reaches a critical level, they generate islands of amorphous material. These regions can have outstanding mechanical properties, which provide additional strengthening and/or toughening mechanisms to enhance the capability of these alloys to withstand extreme loading conditions.

Study on seepage and deformation characteristics of coal microstructure by 3D reconstruction of CT images at high temperatures

Abstract: To study the seepage and deformation characteristics of coal at high temperatures, coal samples from six different regions were selected and subjected to computed tomography (CT) scanning studies. In conjunction with ANSYS software, 3D reconstruction of CT images was used for the establishment of fluid-solid conjugate heat transfer model and coal thermal deformation model based on the microstructures of coal. In addition, the structure of coal was studied in 2D and 3D perspectives, followed by the analysis of seepage and deformation characteristics of coal at high temperatures. The results of this study indicated that porosity positively correlated with the fractal dimension, and the connectivity and seepage performances were roughly identical from 2D and 3D perspectives. As the porosity increased, the fractal dimension of coal samples became larger and the pore-fracture structures became more complex. As a result, the permeability of coal samples decreased. In the meantime, fluid was fully heated, generating high-temperature water at outlet. However, when the porosity was low, the outlet temperature was very high. The average deformation of coal skeleton with different pore-fracture structures at high temperatures showed a trend of initial increase and subsequent decrease with the increase of porosity and fractal dimension. The maximum deformation of coal skeleton positively correlated with connectivity but negatively correlated with the fractal dimension.

Optimized free-form surface modeling of point clouds from laser-based measurement

Abstract: Freeform parameterizations to reproduce structure deformation are increasingly important topics in laser-scanner-based deformation analyses. High-accuracy assurance of free-form surface approximati...

Self-Locomotive Soft Actuator Based on Asymmetric Microstructural Ti3C2Tx MXene Film Driven by Natural Sunlight Fluctuation.

Abstract: Soft actuators and microrobots that can move spontaneously and continuously without artificial energy supply and intervention have great potential in industrial, environmental, and military applications, but still remain a challenge. Here, a bioinspired MXene-based bimorph actuator with an asymmetric layered microstructure is reported, which can harness natural sunlight to achieve directional self-locomotion. We fabricate a freestanding MXene film with an increased and asymmetric layered microstructure through the graft of coupling agents into the MXene nanosheets. Owing to the excellent photothermal effect of MXene nanosheets, increased interlayer spacing favoring intercalation/deintercalation of water molecules and its caused reversible volume change, and the asymmetric microstructure, this film exhibits light-driven deformation with a macroscopic and fast response. Based on it, a soft bimorph actuator with ultrahigh response to solar energy is fabricated, showing natural sunlight-driven actuation with ultralarge amplitude and fast response (346° in 1 s). By utilizing continuous bending deformation of the bimorph actuator in response to the change of natural sunlight intensity and biomimetic design of an inchworm to rectify the repeated bending deformation, an inchwormlike soft robot is constructed, achieving directional self-locomotion without any artificial energy and control. Moreover, soft arms for lifting objects driven by natural sunlight and wearable smart ornaments that are combined with clothing and produce three-dimensional deformation under natural sunlight are also developed. These results provide a strategy for developing natural sunlight-driven soft actuators and reveal great application prospects of this photoactuator in sunlight-driven soft biomimetic robots, intelligent solar-energy-driven devices in space, and wearable clothing.

Efficient Mesh Generation and Deformation for Aerodynamic Shape Optimization

Abstract: Mesh generation and deformation are critical elements in gradient-based aerodynamic shape optimization (ASO). Improperly generated or deformed meshes may contain bad-quality cells that degrade the ...

Additive friction stir deposition: a deformation processing route to metal additive manufacturing

Abstract: As the forging counterpart of fusion-based additive processes, additive friction stir deposition offers a solid-state deformation processing route to metal additive manufacturing, in which every vo...

Sparse Data Driven Mesh Deformation

Abstract: Example-based mesh deformation methods are powerful tools for realistic shape editing. However, existing techniques typically combine all the example deformation modes, which can lead to overfitting, i.e., using an overly complicated model to explain the user-specified deformation. This leads to implausible or unstable deformation results, including unexpected global changes outside the region of interest. To address this fundamental limitation, we propose a sparse blending method that automatically selects a smaller number of deformation modes to compactly describe the desired deformation. This along with a suitably chosen deformation basis including spatially localized deformation modes leads to significant advantages, including more meaningful, reliable, and efficient deformations because fewer and localized deformation modes are applied. To cope with large rotations, we develop a simple but effective representation based on polar decomposition of deformation gradients, which resolves the ambiguity of large global rotations using an as-consistent-as-possible global optimization. This simple representation has a closed form solution for derivatives, making it efficient for our sparse localized representation and thus ensuring interactive performance. Experimental results show that our method outperforms state-of-the-art data-driven mesh deformation methods, for both quality of results and efficiency.

In-plane dynamics crushing of a combined auxetic honeycomb with negative Poisson's ratio and enhanced energy absorption

Abstract: In order to improve the energy absorption capacity of the honeycomb, a combined auxetic honeycomb is designed in this paper. By using the double-inclined walls replacing the horizontal walls of the star-shaped honeycomb (SSH), and introducing a thin-walled circle contacting with the four concave corners of the SSH, the star-circle honeycomb (SCH) is designed. The in-plane dynamic crushing behaviors was explored based on finite element method (FEM). There are three types of deformation modes observed with different impact velocity, including low-, medium- and high-velocity loading modes and the stress-strain curve exhibits two plateau stress stages. Based on the deformation characteristics of the representative unit, theoretical calculation models were established to estimate the plateau stress of the SCH under low- and high-velocity loading according the conservation of energy and the theoretical calculation was in keep well with the numerical simulation. A deformation modes map was summarized to investigate the effects of the impact velocity and the relative density on the deformation modes and the energy absorption capability and the dynamic Poisson's ratio were studied. The result shows that the SCH presents better energy absorption compared with SSH as well as retaining the negative Poisson's ratio property. The deformation mechanism was revealed form the structural design and plastic hinge dissipation. This work presents a different design strategy for the auxetic honeycomb, expected to guide the design of more novel auxetic with better energy absorption and mechanical property.

Deformation limit for the ultimate strength of hollow section joints

Abstract: In order to determine the ultimate load capacity of hollow section joints with CHS or RHS chords, in cases the load - deformation diagrams or moment - rotation diagrams do not show a pronounced peak load, a deformation criterion has been discussed and evaluated. For this aim, various research activities have been carried out for the following types of connections: plate or I-beams to CHS connections, plate or I-beams to RHS connections, X-joints in CHS, X- and T-joints in RHS. From the previous research, it has been shown that the behaviour of hollow section joints is mainly dependent on the local plastification of the chord if the connection is designed in such way that the failure of the brace does not occur before connection failure. Therefore, the deformation limit criteria should be based on the local deformation of the chord face at the intersection between brace and chord. For the design of connections, it must be ensured that conditions with regard to the ultimate strength, deformation capacity and serviceability are satisfied. For this reason, the given deformation limit has been verified by checking the numerical results for the above mentioned types of connections loaded by axial compression or in-plane bending moment. Finally, the ultimate strengths at the deformation limit for connections with RHS chord have been compared with available design formulae from several references.

Similar simulation study on the deformation and failure of surrounding rock of a large section chamber group under dynamic loading

Abstract: Large and super-large section chamber groups in coal mines are frequently affected by dynamic loads resulting from production activities such as roadway driving and blasting The stability of the surrounding rock is poor, and it is difficult to control In this paper, a similar simulation test was used to study the deformation and evolution laws of the surrounding rock of a triangle-shaped chamber group under different dynamic loads The results showed that under dynamic loading, the vertical stress of the surrounding rock of the chamber group increased in an oscillatory form The maximum stress concentration coefficient reached 409 The damage degree of the roof was greater than that of the two sides The deformation of the roof was approximately 12 times that of the two sides For the chamber closer to the power source, the stress oscillation amplitude of the surrounding rock was larger, and the failure was more serious The force of the anchorage structure showed a phased increasing characteristic; additionally, the force of the anchorage structure on the adjacent side of the chambers was greater than that on the other side This study reveals the deformation and failure evolution laws of the surrounding rock of large section chamber groups under dynamic loading

Analysis of deformation control mechanism of prestressed anchor on jointed soft rock in large cross-section tunnel

Abstract: Prestressed anchorage systems have been gradually applied in the treatment of large deformation in soft rock tunneling. However, the research of support parameters on the mechanical behavior of large section cavern surrounding rocks with high joint density and deep buried high ground stress is not enough. In order to study the mechanical behavior of surrounding rocks under prestressed anchor support, a mechanical model is established. It is determined that the main controlling factors of the support effect are prestress, anchor cable length, and anchor cable spacing. Therefore, considering the distribution characteristics of surrounding rock joints, the discrete element simulation of different anchor cable lengths, circumferential spacing, and prestress is carried out. Similar simulation verification experiments further substantiated the accuracy of numerical simulation. The experimental results are applied to field engineering. The results indicate that the numerical simulation method of ubiquitous-joint and DFN (Discrete Fracture Network) can attain accurate results. The primary deformation and plastic zone of the tunnel is mainly located at the left shoulder of the inclined shaft, wherein the plastic zone is mainly tensile failure. The depth of the outer bearing arch, i.e., the length of the long anchor cable, is preferably 10 m. With the increase of circumferential spacing and prestress, the deformation and plastic zone of tunnel surrounding rock show a linear decrease. This paper can provide a theoretical basis for applying the prestressed anchorage system to control the large deformation of tunnel soft rock.

Coseismic and early postseismic deformation due to the 2021 M7.4 Maduo (China) earthquake

Abstract: Key Points: • We use Sentinel-1 Synthetic Aperture Radar (SAR) data to derive a finite fault model for the 2021 M7.4 Maduo (Qinghai, China) earthquake • The along-strike averaged coseismic slip has...

Coal Structure and Its Implications for Coalbed Methane Exploitation: A Review

Abstract: Coal structure refers to the internal structural characteristics of coals including the degree of macroscopic and microscopic deformation, pore structure, and mechanical properties after various ge...

In-situ carbide-reinforced CoCrFeMnNi high-entropy alloy matrix nanocomposites manufactured by selective laser melting: Carbon content effects on microstructure, mechanical properties, and deformation mechanism

Abstract: The fabrication of high-entropy alloy (HEA) matrix nanocomposites by additive manufacturing (AM) is challenging due to that the control of defect-low sample having even distribution of reinforcement via AM is extremely hard. In this study, we investigated the effect of carbon content on the microstructure evolution, tensile properties, and deformation mechanisms of Cx(Co20Cr20Fe20Mn20Ni20)100–x (x = 0.5, 1.0, and 1.5 at.%) HEA matrix nanocomposites additively manufactured by selective laser melting (hereafter referred to as SLM-built C-HEAs). SLM-built C-HEAs showed epitaxial growth grains, dislocation networks, and nano-sized carbides. In addition, with an increase in carbon content, the number density of nano-sized carbides, and the average grain sizes and columnar widths increased. In addition, the strength, work hardening rate, and elongation of SLM-built C-HEAs were enhanced as the carbon content increased. Dislocation networks in the as-built samples hindered the dislocation motion in the early to later stages of deformation, thus leading to high back stresses in SLM-built C-HEAs. Deformation twins were also formed in the three samples, because the critical stress for twinning was similar to the flow stresses at an early stage of deformation of SLM-built C-HEAs. Further, the yield strengths of SLM-built C-HEAs were predicted using six strengthening mechanisms that considered the microstructural factors. Based on the above findings, we discussed the correlations between the microstructure, mechanical properties, and deformation mechanisms of SLM-built C-HEAs with different carbon contents.

Deformation Behaviors and Mechanical Mechanisms of Double Primary Linings for Large-Span Tunnels in Squeezing Rock: A Case Study

Abstract: Large deformation has always been a focus and difficult issue in the construction of deep-buried tunnels in squeezing rock. Previous studies mainly focused on the large deformation of medium and small span railway/highway tunnels in soft ground. However, there are limited researches on the large deformation control methods for large-span (three-lane) highway tunnels constructed in unfavorable geological environment. Based on the Lianchengshan Tunnel of the Baoji-Hanzhong expressway in Shaanxi Province, China, this paper studied the deformation behaviors and mechanical mechanisms of a large-span tunnel excavated in chlorite schist formation with single primary lining method and double primary lining method by in-situ test and numerical simulation. The achieved results indicate that the double primary lining method is much more effective than that of the single primary lining method in restraining the deformation of surrounding rock, and the maximum vertical displacement and horizontal convergence are reduced by 67% and 66%, respectively. The support method of double HK200b-type steel sets combined with large-diameter foot reinforcement bolt (FRB) and deep invert could effectively control the large deformation of the case tunnel, which effectively avoided the supporting structure failure, repeated clearance invasion and multiple reshaping work caused by the single primary lining method and conformed to the energy-saving construction concept of “no clearance interfering, no support reshaping” of tunnels in squeezing ground. Simulation analysis of surrounding rock deformation, supporting structure stress and plastic zone distribution was performed to evaluate the support effect of the two deformation-controlled methods. Finally, the deformation and stress characteristic curves of rock-support of the two deformation-controlled methods were established, which revealed the supporting mechanism of double primary linings for large-span tunnels in chlorite schist. The research results can provide a theoretical basis and practical reference for the large-deformation control of similar large-span tunnels in squeezing rock.

Physical Model Test on the Deformation Behavior of an Underground Tunnel Under Blasting Disturbance

Abstract: A physical model test is carried out to simulate the blasting disturbance on the underground tunnel. The test including four blasting events with different blasting locations, where two blasting angles ( $$\left| \alpha \right|$$ ) and two blasting distances (D) are designed. The surface deformation characteristics of the physical model are observed by a DIC system. The deformation responses of four strain components during blasting are obtained. The influences of the blasting location on the surface deformation and failure characteristics are analyzed. The distributions of strain components ex, ey, exy, and e1 are obtained for different blasting locations. The different occurrences of failure are compared for cases where the blasthole is at varying locations from the tunnel. The results show that when the blasthole is far from the tunnel, the failure mainly occurs in the vicinity of the blasthole and the failure pattern of the physical model is conical. When the blasthole is close enough to the tunnel and is near the vertical wall, the surrounding rock fail in a V-shape. According to the failure patterns, the anti-disturbance ability of the arch is obviously stronger than that of the vertical wall.

DEM modelling of mini-triaxial test based on one-to-one mapping of sand particles

Abstract: This paper presents a discrete-element method simulation of mini-triaxial tests on a sand with realistically shaped grains. It compares the results with physical experiments at multiple length scal...

Interactions between Dislocations and Boundaries during Deformation.

Abstract: The interactions between dislocations (dislocations and deformation twins) and boundaries (grain boundaries, twin boundaries and phase interfaces) during deformation at ambient temperatures are reviewed with focuses on interaction behaviors, boundary resistances and energies during the interactions, transmission mechanisms, grain size effects and other primary influencing factors. The structure of boundaries, interactions between dislocations and boundaries in coarse-grained, ultrafine-grained and nano-grained metals during deformation at ambient temperatures are summarized, and the advantages and drawbacks of different in-situ techniques are briefly discussed based on experimental and simulation results. The latest studies as well as fundamental concepts are presented with the aim that this paper can serve as a reference in the interactions between dislocations and boundaries during deformation.

Evidence of FCC to HCP and BCC-martensitic transformations in a CoCrFeNiMn high-entropy alloy by severe plastic deformation

Abstract: An equiatomic CoCrFeNiMn high entropy alloy was subjected to high-pressure torsion under a pressure of 10 GPa at room and cryogenic temperatures. Increasing straining and decreasing the deformation temperature led to deformation-induced FCC to HCP and BCC martensitic transformations, which played a significant role in the strengthening of the alloy.