Elastic instability in graphite single crystal under dynamic triaxial compression: Effect of strain-rate on the resulting microstructure

This study aims at determining the effect of water pressure on the mechanical properties of concrete subjected to freeze-thaw (F-T) attack under the dynamic triaxial compression state. Two specimens were used: (1) a 100 mm × 100 mm × 400 mm prism for testing the loss of mass and relative dynamic modulus of elasticity (RDME) after F-T cycles and (2) cylinders with a diameter of 100 mm and a height of 200 mm for testing the dynamic mechanical properties of concrete. Strain rates ranged from 10−5·s−1 to 10−3·s−1, and F-T cycles ranged from 0 to 100. Three levels of water pressure (0, 5, and 10 MPa) were applied to concrete. Results showed that as the number of F-T cycles increased, the mass loss rate of the concrete specimen initially decreased and then increased, but the RDME decreased. Under 5 MPa of water pressure and at the same strain rate, the ultimate compressive strength decreased, whereas the peak strain increased with the increase in the number of F-T cycles. This result is contrary to the variation law of ultimate compressive strength and peak strain with the increase in strain rate under the same number of F-T times. With the increase in F-T cycles or water pressure, the strain sensitivity of the dynamic increase factor of ultimate compressive strength and peak strain decreased, respectively. After 100 F-T cycles, the dynamic compressive strength under all water pressure levels tended to increase as the strain rate increased, whereas the peak strain decreased gradually.

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Observation of dislocations in dynamically loaded Cu-SiO2

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100143705 ◽

1986 ◽

Vol 44 ◽

pp. 424-425

Author(s):

D. S. Pritchard

Keyword(s):

Electron Microscope ◽

Strain Rate ◽

Single Crystal ◽

Transmission Electron Microscope ◽

Volume Fraction ◽

Screw Dislocations ◽

Spherical Inclusions ◽

Transmission Electron ◽

Crystal Dispersion ◽

Strain Rate Loading

The effect of varying the strain rate loading conditions in compression on a copper single crystal dispersion-hardened with SiO2 particles has been examined. These particles appear as small spherical inclusions in the copper lattice and have a volume fraction of 0.6%. The structure of representative crystals was examined prior to any testing on a transmission electron microscope (TEM) to determine the nature of the dislocations initially present in the tested crystals. Only a few scattered edge and screw dislocations were viewed in those specimens.

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Understanding the Strain Path Effect on the Deformed Microstructure of Single Crystal Pure Aluminum

Metals ◽

10.3390/met11081189 ◽

2021 ◽

Vol 11 (8) ◽

pp. 1189

Author(s):

Yingjue Xiong ◽

Qinmeng Luan ◽

Kailun Zheng ◽

Wei Wang ◽

Jun Jiang

Keyword(s):

Strain Rate ◽

Single Crystal ◽

Strain Path ◽

Mechanical Response ◽

Pure Aluminum ◽

Lattice Rotation ◽

Softening Behavior ◽

Theoretical Support ◽

Commercial Applications ◽

Electron Back Scattered Diffraction

During plastic deformation, the change of structural states is known to be complicated and indeterminate, even in single crystals. This contributes to some enduring problems like the prediction of deformed texture and the commercial applications of such material. In this work, plane strain compression (PSC) tests were designed and implemented on single crystal pure aluminum to reveal the deformation mechanism. PSC tests were performed at different strain rates under strain control in either one-directional or two-directional compression. The deformed microstructures were analyzed according to the flow curve and the electron back-scattered diffraction (EBSD) mappings. The effects of grain orientation, strain rate, and strain path on the deformation and mechanical response were analyzed. Experimental results revealed that the degree of lattice rotation of one-dimensional compression mildly dependents on cube orientation, but it is profoundly sensitive to the strain rate. For two-dimensional compression, the softening behavior is found to be more pronounced in the case that provides greater dislocations gliding freeness in the first loading. Results presented in this work give new insights into aluminum deformation, which provides theoretical support for forming and manufacturing of aluminum.

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Molecular Dynamics Simulation of Crack Propagation in Single-Crystal Aluminum Plate with Central Cracks

Journal of Nanomaterials ◽

10.1155/2017/5181206 ◽

2017 ◽

Vol 2017 ◽

pp. 1-12 ◽

Cited By ~ 6

Author(s):

Jun Ding ◽

Lu-sheng Wang ◽

Kun Song ◽

Bo Liu ◽

Xia Huang

Keyword(s):

Molecular Dynamics ◽

Plastic Deformation ◽

Crack Propagation ◽

Strain Rate ◽

Single Crystal ◽

Crack Length ◽

Crack Growth ◽

Plastic Yield ◽

Model Size ◽

Dislocation Multiplication

The crack propagation process in single-crystal aluminum plate (SCAP) with central cracks under tensile load was simulated by molecular dynamics method. Further, the effects of model size, crack length, temperature, and strain rate on strength of SCAP and crack growth were comprehensively investigated. The results showed that, with the increase of the model size, crack length, and strain rate, the plastic yield point of SCAP occurred in advance, the limit stress of plastic yield decreased, and the plastic deformability of material increased, but the temperature had less effect and sensitivity on the strength and crack propagation of SCAP. The model size affected the plastic deformation and crack growth of the material. Specifically, at small scale, the plastic deformation and crack propagation in SCAP are mainly affected through dislocation multiplication and slip. However, the plastic deformation and crack propagation are obviously affected by dislocation multiplication and twinning in larger scale.

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Influence of strain rate effect on material removal and deformation mechanism based on ductile nanoscratch tests of Lu2O3 single crystal

Ceramics International ◽

10.1016/j.ceramint.2018.08.210 ◽

2018 ◽

Vol 44 (17) ◽

pp. 21486-21498 ◽

Cited By ~ 15

Author(s):

Chen Li ◽

Feihu Zhang ◽

Yueqin Wu ◽

Xuan Zhang

Keyword(s):

Strain Rate ◽

Single Crystal ◽

Deformation Mechanism ◽

Material Removal ◽

Strain Rate Effect ◽

Rate Effect

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Damage evolution and recrystallization enhancement of frozen loess

International Journal of Damage Mechanics ◽

10.1177/1056789517731138 ◽

2017 ◽

Vol 27 (8) ◽

pp. 1131-1155 ◽

Cited By ~ 21

Author(s):

Zhiwei Zhou ◽

Wei Ma ◽

Shujuan Zhang ◽

Cong Cai ◽

Yanhu Mu ◽

...

Keyword(s):

Mechanical Properties ◽

Strain Rate ◽

Damage Evolution ◽

Deformation Process ◽

Triaxial Compression ◽

Confining Pressure ◽

Recrystallization Process ◽

Frozen Soils ◽

Time Deformation ◽

Pressure Melting

A series of multistage triaxial compression, creep, and stress relaxation tests were conducted on frozen loess at the temperature of −6℃ in order to study the damage evolution and recrystallization enhancement of mechanical properties during deformation process. The effect of strain rate, confining pressure, and hydrostatic stress history in the degradation laws of mechanical properties is investigated further. The strain rate has a significant influence on the stress–strain curve which dominates the evolution trend of mechanical properties. The mechanical behaviors (strength, stiffness, and viscosity) of frozen loess all exhibit evident response for the consolidation and pressure melting phenomenon caused by the confining pressure. The multistage loading tests under different hydrostatic stresses are capable of differentiating the development characteristics of mechanical properties during axial loading and hydrostatic compression process, respectively. The testing results indicated that the recrystallization of the ice particle in the frozen soils is an important microscopic factor for enhancement behaviors of mechanical parameters during the deformation process. This strengthening degree of mechanical properties is determined by temperature, duration time, deformation degree, and stress state during the recrystallization process. The phase transformation led by pressure melting and ice recrystallization is a nonnegligible changing pattern of frozen soils microstructure, which has apparent role in the damage evolution of mechanical properties.

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