Opposite grain size dependence of strain rate sensitivity of copper at low vs high strain rates

2018 ◽  
Vol 738 ◽  
pp. 430-438 ◽  
Author(s):  
Z.N. Mao ◽  
X.H. An ◽  
X.Z. Liao ◽  
J.T. Wang
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Size Dependence ◽  
High Strain ◽  
Rate Sensitivity ◽  
Strain Rates ◽  
High Strain Rates

Strain-Rate Sensitivity Enhanced by Grain-Boundary Sliding in Creep Condition for AZ31 Magnesium Alloy at Room Temperature

2016 ◽  
Vol 838-839 ◽  
pp. 106-109 ◽  
Author(s):  
Tetsuya Matsunaga ◽  
Hidetoshi Somekawa ◽  
Hiromichi Hongo ◽  
Masaaki Tabuchi
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Room Temperature ◽  
High Strain ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Strain Rates ◽  
High Strain Rates ◽  
Boundary Sliding

This study investigated strain-rate sensitivity (SRS) in an as-extruded AZ31 magnesium (Mg) alloy with grain size of about 10 mm. Although the alloy shows negligible SRS at strain rates of >10-5 s-1 at room temperature, the exponent increased by one order from 0.008 to 0.06 with decrease of the strain rate down to 10-8 s-1. The activation volume (V) was evaluated as approximately 100b3 at high strain rates and as about 15b3 at low strain rates (where b is the Burgers vector). In addition, deformation twin was observed only at high strain rates. Because the twin nucleates at the grain boundary, stress concentration is necessary to be accommodated by dislocation absorption into the grain boundary at low strain rates. Extrinsic grain boundary dislocations move and engender grain boundary sliding (GBS) with low thermal assistance. Therefore, GBS enhances and engenders SRS in AZ31 Mg alloy at room temperature.

Investigation on Strain Rate Sensitivity of 3D Printed sPEEK-HAP/rGO Composites

2021 ◽  
Author(s):  
Sagar Mahalingappa Baligidad ◽  
Chethan Kumar Gangadhara ◽  
Maharudresh Aralikatte Chandrashekhar
Keyword(s):  
Strain Rate ◽  
Polymer Composites ◽  
Strain Rate Sensitivity ◽  
High Strain ◽  
Rate Sensitivity ◽  
Sensitivity Factor ◽  
Strain Rates ◽  
High Strain Rates ◽  
Compression Behaviour ◽  
Yield Behaviour

Abstract Nanofillers can be added to polymers to improve their mechanical behavior. However, the yield behaviour of most polymer composites is influenced by strain rate. The majority of the research focused on the behaviour of polymer composites at high strain rates. This work aims to investigate how hydroxyapatite (HAP) and reduced Graphene Oxide (rGO) nanofillers affect the mechanical properties of sulphonated polyetheretherketone (sPEEK) at low (tensile and compression behaviour) and high strain rates (compression behaviour). The thermal, mechanical, and energy absorption responses of sPEEK filled with HAP and varying mass fraction (Mf) of rGO (0.5%, 1%, and 1.5%) at different strain are studied in detail. The strong strain rate effect was seen in HAp and rGO loaded sPEEK composites. The strain rate sensitivity factor of sPEEK-HAP/rGO improved as the strain rate increased, but decreased when the Mf of rGO increased. Under low strain rate compression, HAp and rGO loaded sPEEK absorbed more energy at Mf about 4%. SEM micrography was used to study the microstructures of the fractured interfaces of the components, revealing that the HAp and sPEEK materials formed a good compatibility in presence of rGO.

Nonlinear Analysis Techniques for Shear Band Formation at High Strain-Rates

1992 ◽  
Vol 45 (3S) ◽  
pp. S82-S94 ◽  
Author(s):  
Athanasios E. Tzavaras
Keyword(s):  
Strain Rate ◽  
Shear Strain ◽  
Nonlinear Analysis ◽  
Strain Rate Sensitivity ◽  
Strain Softening ◽  
High Strain ◽  
Rate Sensitivity ◽  
Strain Rates ◽  
High Strain Rates ◽  
Analysis Techniques

One of the most striking manifestations of instability in solid mechanics is the localization of shear strain into narrow bands during high speed, plastic deformations of metals. According to one theory, the formation of shear bands is attributed to effective strain-softening response, which results at high strain rates as the net outcome of the influence of thermal softening on the, normally, strain-hardening response of metals. Our objective is to review some of the insight obtained by applying nonlinear analysis techniques on simple models of nonlinear partial differential equations simulating this scenario for instability. First, we take up a simple system, intended as a paradigm, that describes isothermal shear deformations of a material exhibiting strain softening and strain-rate sensitivity. As it turns out, for moderate amounts of strain softening strain-rate sensitivity exerts a dissipative effect and stabilizes the motion. However, once a threshold is exceeded, the response becomes unstable and shear strain localization occurs. Next, we present extensions of these results to situations where explicit thermal effects are taken into account.

scholarly journals On the grain size dependence of shock responses in nanocrystalline sic ceramics at high strain rates

2020 ◽  
Vol 200 ◽  
pp. 632-651 ◽  
Author(s):  
Wanghui Li ◽  
Eric N. Hahn ◽  
Xiaohu Yao ◽  
Timothy C. Germann ◽  
Biao Feng ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Dependence ◽  
High Strain ◽  
Strain Rates ◽  
High Strain Rates ◽  
Sic Ceramics

Grain Refinement during Superplastic Deformation of Coarse-Grained Al-Mg-Cu Alloys

2006 ◽  
Vol 509 ◽  
pp. 75-80 ◽  
Author(s):  
M.I. Cruz-Palacios ◽  
D. Hernández-Silva ◽  
L.A. Barrales-Mora ◽  
M.A. García-Bernal
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Grain Refinement ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Mg Alloy ◽  
Coarse Grained ◽  
Dislocation Creep ◽  
Rolled Plate ◽  
Strain Rates

In the present study the superplastic behavior of Al-6%Mg–0.5%Cu and Al–8%Mg– 0.5%Cu in a coarse grain size condition has been studied. The alloys are melted in an electrical furnace under argon atmosphere. The ingots (25 mm thick) are homogenized at 400 °C during 72 h and then rolled at 430 °C to a thickness of 5 mm. The mean grain size after rolling is 55 µm for the 6%Mg alloy and 61 µm for the 8%Mg alloy. Tensile test specimens are machined from the rolled plate in the rolling direction. Strain-rate-change tests at temperatures between 300 and 450 °C and strain rates between 1x10-4 and 1x10-1 s-1 are carried out to determine the strain rate sensitivity of the flow stress. Finally, elongation to failure tests are conducted at temperatures and strain rates where the alloys show a high strain rate sensitivity. Elongations higher than 390 % are obtained for the 8%Mg alloy. It is observed that the grip regions of the deformed samples show coarser grains than the regions near to the fracture surface. This means that grain refinement takes place during deformation, suggesting that the principal deformation mechanism is dislocation creep.

High Strain Rate Behaviour of Iron and Nickel

1972 ◽  
Vol 14 (3) ◽  
pp. 161-167 ◽  
Author(s):  
T. Muller
Keyword(s):  
Strain Rate ◽  
High Strain ◽  
True Strain ◽  
Rate Sensitivity ◽  
Correction Method ◽  
Strain Rates ◽  
High Strain Rates ◽  
Controlling Mechanism ◽  
Split Hopkinson ◽  
Rate Behaviour

An investigation into the mechanical behaviour of iron and nickel at high strain rates is carried out, using a split Hopkinson bar method. Some special adaptations, a correction method for the effects arising from the adiabatic conditions of dynamic deformation and a simplified data processing procedure are described in detail. The test conditions covered a range of strain rates between 500 and about 10 000/s and temperatures from 20 to 500°C. For both metals, the results are presented by means of a family of true stress-true strain curves. The strong strain rate sensitivity at high strain rates indicates that the rate controlling mechanism differs from that operative at ‘static’ strain rates.

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