Optimisation of thickness of miniature tensile specimens for evaluation of mechanical properties

Kumar, Kuljit; Pooleery, Arun; Madhusoodanan, K.; Singh, Ranjit; Chatterjee, Arindam; Dutta, B.K.; Sinha, R.K.

doi:10.1016/j.msea.2016.08.032

Cited by 66 publications

(24 citation statements)

References 16 publications

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“…In addition, the build-up of back stresses is limited in those grains and therefore they do not inhibit the operation of dislocation sources to the same extent as a fully constrained grain. A recent study was performed by Kumar et.al into the effect of specimen geometry on bulk samples including the specimen thickness to grain diameter ratio (t/d) for various steels [47]. It was demonstrated that the loss of strain hardening due to t/d was in the order of 0.03 for the most similar alloy (CrMoV) to that studied here.…”

Section: Finite Element Analysismentioning

confidence: 60%

On the Application of Xe+ Plasma FIB for Micro-fabrication of Small-scale Tensile Specimens

et al. 2019

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Section: Finite Element Analysismentioning

confidence: 60%

On the Application of Xe+ Plasma FIB for Micro-fabrication of Small-scale Tensile Specimens

et al. 2019

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“…However, in contrast to the standard tensile specimen specified in ASTM E8 or ISO 6892, many different designs of miniature tensile specimens have been proposed. 4,5,[7][8][9][10][11][12] They feature different dimensions of the gauge section, aspect ratio of the cross-section, radius of the fillet, and gripping mechanism. One conclusion that could be drawn from the results of various miniature tensile tests is that the determined yield strength, ultimate strength, and uniform elongation are comparable to the standard specimen results.…”

Section: Introductionmentioning

confidence: 99%

Determination of constitutive relation from miniature tensile test with digital image correlation

Zhang

Karnati

Pan

et al. 2020

The Journal of Strain Analysis for Engineering Design

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The determination of constitutive relation from the miniature tensile test is of high interest in multiple areas. Here, a convenient experimental method is proposed to determine the true stress–strain curve from the miniature tensile test. The instantaneous cross-sectional area is estimated by only one camera in aid of digital image correlation technique. This method was applied on commercial pure titanium and aluminum 6061 alloys, and the results indicate that the extracted true stress–strain curves are not scale-dependent. The derived mechanical properties from miniature specimens match well with the results of standard specimens. The correctness of the true stress–strain curve was evaluated by the finite element analysis method. The results suggest that the derived true stress–strain curve is capable to represent the constitutive behavior of the tested materials.

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“…bulk) will harden at a higher rate due to the contributions of back stresses generated by dislocations accumulating in the larger fraction of fully constrained grains 19,58 . It has been shown that the strain hardening parameter (n) raises with increased t/d before stabilising and accurately reflecting bulk hardening 59 , the position and shape of this threshold value can vary considerably between materials 60 .…”

Section: Discussionmentioning

confidence: 99%

Novel Methods for Recording Stress-Strain Curves in Proton Irradiated Material

Smith

Garner

Lunt

et al. 2020

Sci Rep

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proton irradiation is often used as a proxy for neutron irradiation but the irradiated layer is typically <50 μm deep; this presents a problem when trying to obtain mechanical test data as a function of irradiation level. two novel methodologies have been developed to record stress-strain curves for thin proton-irradiated surface layers of SA-508-4N ferritic steel. In the first case, in-situ loading experiments are carried out using a combination of X-ray diffraction and digital image correlation on the near surface region in order to measure stress and strain, thereby eliminating the influence of the non-irradiated volume. the second approach is to manufacture small-scale tensile specimens containing only the proton irradiated volume but approaching the smallest representative volume of the material. this is achieved by high-speed focused ion beam (fiB) milling though the application of a Xe + plasma-fiB (PFIB). It is demonstrated that both techniques are capable of recording the early stage of uniaxial flow behaviour of the irradiated material with sufficient accuracy providing a measure of irradiation-induced shift of yield strength, strain hardening and tensile strength.The limited penetration depth of proton irradiation makes measurement of mechanical properties difficult using established techniques 16,17 . Over the last decade, the use of Ga + focussed ion beam (FIB) instruments has allowed for the preparation of small scale samples from proton irradiated layers 18-23 . The mechanical properties of these samples are then tested using a MEMS chip or piezo-actuated test rig without contributions from the non-irradiated volume. This development has allowed studies to take advantage of the increased dose rates and to probe changes in properties previously only attainable using indentation testing [24][25][26][27][28] . However, milling rates are slow because for Ga + FIBs the useable milling currents are limited due to the point source of Ga + ions. Consequently, specimen diameters achievable in a practical time frame are limited to ~10 µm. For most engineering materials, the maximum achievable scale is therefore in the order of single to only a few grains. Hence, the technique is most applicable to single and bi-crystal investigations rather than representing the bulk response of polycrystalline specimens. It has been demonstrated that small scale specimens exhibit an increased hardening inversely proportional to specimen diameter [29][30][31][32][33] . In order to obtain a bulk response, specimens require a minimum length scale sufficient to overcome size reduction effects. The optimum specimen size would have the smallest representative volume (SRV), which would retain the benefits of scale reduction whilst exhibiting bulk behaviour 34 .Recent work by the authors has explored two techniques to increase the sampling volume in low energy proton irradiated samples prepared for mechanical testing 35,36 . The first, an adaptation of the technique outlined by Foecke et al. 37 , combines in-situ X-ray diffraction ...

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Optimisation of thickness of miniature tensile specimens for evaluation of mechanical properties

Cited by 66 publications

References 16 publications

On the Application of Xe+ Plasma FIB for Micro-fabrication of Small-scale Tensile Specimens

On the Application of Xe+ Plasma FIB for Micro-fabrication of Small-scale Tensile Specimens

Determination of constitutive relation from miniature tensile test with digital image correlation

Novel Methods for Recording Stress-Strain Curves in Proton Irradiated Material

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