Characterization of strain rate sensitivity and activation volume using the indentation relaxation test

Xu, Baoxing; Yue, Zhufeng; Chen, Xi

doi:10.1088/0022-3727/43/24/245401

Cited by 25 publications

(15 citation statements)

References 38 publications

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“…The dependence of steady-state indentation creep rate, ɛ·ind (and not necessarily the transient stage) upon applied indentation stress, σind, at the temperature T can be characterized using an Arrhenius type rate equation: 36,37 where A is a material constant that depends on the material's properties (unit of s −1 MPa – n ), n is the creep stress exponent, and Q creep is the apparent creep activation energy (unit of J mol −1 ).…”

Section: Resultsmentioning

confidence: 99%

Depth sensing indentation of magnesium/boron nitride nanocomposites

Haghshenas

Islam

Wang

et al. 2018

Journal of Composite Materials

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Magnesium nanocomposites, considered as energy-saving lightweight materials of future, are a fairly new family of composite materials with enhanced specific strength and ductility compared to pure magnesium and/or magnesium alloys. In the present study, time-dependent plastic deformation of novel light-weight magnesium/boron nitride nanocomposites containing 0.5, 1.5 and 2.5 vol% of nano-boron nitride particulates is studied through a depth-sensing indentation approach against monolithic pure magnesium. The synthesis of magnesium–boron nitride nanocomposites was accomplished using powder metallurgy technique coupled with microwave sintering, followed by hot extrusion (end products are 8-mm diameter rods). The depth sensing indentation creep tests were conducted at room temperature (∼0.32Tm of magnesium) using an instrumented indentation platform via a self-similar pyramidal (Berkovich) indenter. To assess the influence of loading rate on the indentation-induced deformation behavior of the materials, a dual stage indentation creep including a constant loading rate followed by a constant load-holding scheme was used; indentation tests were performed on the specimens. The specimens were loaded at rates of 0.05, 0.5, 5, and 50 mN/s to a peak load of 50 mN then force was held constant for 400 s while load/displacement/time data were recorded continuously. The results of the depth sensing indentation tests were correlated and explained using the microstructural characteristics placing special emphasis on the volume fraction of reinforcement and the indentation loading rate. Finally, the controlling creep mechanisms of the magnesium–boron nitride nanocomposites and the base metal (pure magnesium) were discussed in the present paper. The results of this paper can be used as a baseline for high-temperature creep analysis of magnesium–boron nitride nanocomposites which is of engineering significance.

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Section: Resultsmentioning

confidence: 99%

Depth sensing indentation of magnesium/boron nitride nanocomposites

Haghshenas

Islam

Wang

et al. 2018

Journal of Composite Materials

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“…The compression relaxation rate ( R IT ) was used to characterize the spherical nanoindentation relaxation of materials under different holding h s, which was often modeled with eq. (1):

R_{IT} = \frac{p_{1} - p_{2}}{p_{1}} \times 100 %

…”

Section: Resultsmentioning

confidence: 99%

Mechanical responses in the length direction and thickness direction of quaternary 1,4‐diazabicyclo‐[2.2.2]‐octane polysulfone alkaline anion‐exchange fuel‐cell membranes

Zhang

Tian

et al. 2019

J of Applied Polymer Sci

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A quaternary 1,4-diazabicyclo-[2.2.2]-octane polysulfone (QDPSU) alkaline anion-exchange fuel-cell membrane was synthesized. Nanoindentation and uniaxial tension methods were used to test the mechanical properties of this membrane in both the thickness direction and length direction at 26 C and 40% relative humidity. We found that the QDPSU membrane exhibited remarkable viscoelastic properties with significant loading rate-dependent behavior and time-dependent behavior (creep-relaxation). The value of compression creep rates and compression relaxation rates of the QDPSU membrane were measured to be about 0.2 by a spherical indenter and changed very little with different holding loads. Compared with Nafion, a most widely used fuel-cell membrane, the QDPSU alkaline anion-exchange membrane showed a better creep resistance. During the nanoindentation fatigue test, the variation of depths with the indentation cycles were divided into a rising primary region, a steady-state secondary region, and a continuous declining region. This was different from the uniaxial tension fatigue test. The cross-scale and cross-direction mechanical study from this work will help provide new evidence for bridging the gap between nanoindentation and uniaxial tensile testing.

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“…This is called strain sensitivity owing to the time dependent phenomenon in dislocation motion, such as creep and atomic diffusion [21,22]. As mentioned above (see Section 1), the present indentation test attempts to evaluate mechanical properties (i.e.…”

Section: Methodsmentioning

confidence: 99%