Designing nanoindentation simulation studies by appropriate indenter choices: Case study on single crystal tungsten

Goel, Saurav; Cross, Graham L. W.; Stukowski, Alexander; Gamsjäger, Ernst; Beake, Ben D.; Agrawal, Anupam

doi:10.1016/j.commatsci.2018.04.044

Cited by 50 publications

(25 citation statements)

References 55 publications

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“…Beside, MD conditions were such that the tests were made in vacuum. These situation leads to an overestimated forces compared to when modelling a real diamond indenter and this aspect was recently highlighted by the authors [37]. In light of this, it is safe to say that the main inference from figure 14 should be that the DPs showed higher COF than the CP's but their absolute value depicted in figure 14 may be subjected to change based on more realistic modelling conditions.…”

Section: Scratch Forces and Friction Ratiomentioning

confidence: 89%

“…A total of twenty five indents were made on pure Mg and on both type of precipitate regions to ensure the repeatability and average data with standard deviation was obtained. Nano hardness values were determined from loaddisplacement curves by applying the Oliver-Pharr method [36] that relies on using loaddisplacement profiles without measurement of the actual projected contact area postindentation [37,38].…”

Section: Nano-hardness Testmentioning

confidence: 99%

“…A force-field providing interaction of carbon atoms (diamond indenter) with Mg and al atoms is not readily available and therefore, an imaginary spherical shaped rigid indenter of radius R= 5 nm, described by a potential with a repulsive force constant F(r) = -K(r-R) 2 where K is 2 keV/Å 3 = 3204 nN/Å 2 = 320.4 TPa, was modelled to mimic a spherical probe. This assumption has some implications of underestimating the cutting forces but it is a reasonable choice [37,48]. After equilibration of the model at 300 K, the repulsive indenter was prescribed a constant velocity of 100 m/s to move a total distance of 32.984 nm of which 31.984 nm was through the workpiece.…”

Section: Simulation Setupmentioning

confidence: 99%

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Towards an improved understanding of plasticity, friction and wear mechanisms in precipitate containing AZ91 Mg alloy

et al. 2020

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This work reports a combined experimental and atomistic simulation study on continuous precipitates (CPs) and discontinuous precipitates (DPs) affecting the scratch induced wear in AZ91 magnesium alloy. Nanoscratching experiments complemented by atomic simulations were performed to understand the directional dependence and origins of plasticity, friction and wear mechanisms as benchmarked to nanocrystalline HCP magnesium. Post scratch deformation analysis was performed using electron back scattering diffraction, scanning electron microscope and molecular dynamics (MD) simulation. The direction of orientation of the precipitates was observed to make a significant influence on the deformation behaviour.For example, regardless of the precipitates type (CP or DP), a ductile-brittle transition becomes pronounced while scratching along the direction (orientation) of precipitates, whilst a fully ductile response was obtained while scratching along the direction normal to the precipitates.However, regardless of the direction of orientation, DPs showed a higher wear resistance and coefficient of friction compared to the CPs. These observations were supported by the quantitative analysis of the planar defects such as coherent twins, extrinsic and intrinsic stacking faults in the deformation zone as well as 1/3 < 11 ̅ 00 > and 1/3 < 12 ̅ 10 > . Please refer to any applicable publisher terms of use.2 dislocations type extracted from the MD analysis.These observations will facilitate an improved design of AZ91 alloys in particular and intermetallic precipitate containing alloys in general.

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Section: Scratch Forces and Friction Ratiomentioning

confidence: 89%

Section: Nano-hardness Testmentioning

confidence: 99%

Section: Simulation Setupmentioning

confidence: 99%

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Towards an improved understanding of plasticity, friction and wear mechanisms in precipitate containing AZ91 Mg alloy

et al. 2020

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“…Earlier, Ruestes, Stukowski, Tang, Tramontina et al [15] had investigated the importance of choosing appropriate interatomic potentials among other parameters in assessing the simulated nano-indentation behavior of another bcc metal, tantalum. Goel, Cross, Stukowski, Gamsjäger, Beake and Agrawal [16] have also reported on the design aspects of simulated nano-indentation tests, with application to simulated and experimental tests on (isotropic) bcc tungsten. For modeled diamond indentation at 10 K of a (100) tungsten crystal surface, a higher E r than the extrapolated experimental value was obtained, seemingly consistent with the Alhafez et al [5] result based on comparison with the (111) experimental α-iron value.…”

Section: Comparison Of Hertzian Elastic Loading Behaviorsmentioning

confidence: 99%

Dislocation Reaction Mechanism for Enhanced Strain Hardening in Crystal Nano-Indentations

Armstrong

Elban

2019

Crystals

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Stress–strain calculations are presented for nano-indentations made in: (1) an ammonium perchlorate (AP), NH4ClO4, {210} crystal surface; (2) an α-iron (111) crystal surface; (3) a simulated test on an α-iron (100) crystal surface. In each case, the calculation of an exceptionally-enhanced plastic strain hardening, beyond that coming from the significant effect of small dislocation separations in the indentation deformation zone, is attributed to the formation of dislocation reaction obstacles hindering further dislocation movement. For the AP crystal, the exceptionally-high dislocation reaction-based strain hardening, relative to the elastic shear modulus, leads to (001) cleavage cracking in nano-, micro- and macro-indentations. For α-iron, the reaction of (a/2) <111> dislocations to form a [010] Burgers vector dislocation obstacles at designated {110} slip system intersections accounts for a higher strain hardening in both experimental and simulated nano-indentation test results. The α-iron stress–strain calculations are compared, both for the elastic deformation and plastic strain hardening of nano-indented (100) versus (111) crystal surfaces and include important observations derived from internally-tracked (a/2) <010> Burgers vector dislocation structures obtained in simulation studies. Additional comparisons are made between the α-iron calculations and other related strength properties reported either for bulk, micro-pillar, or additional simulated nano-crystal or heavily-drawn polycrystalline wire materials.

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“…The nanoindentation method has a very small measurement area. Therefore, it is expected to be able to measure the effect of the crystal orientation or microdefects of specimens on the mechanical properties of a material [3][4][5][6][7]. In this report, in order to investigate the effect of the crystal orientation, the hardness and the reduced modulus of the single crystal of sapphire were measured by changing the direction angle of Berkovich indenter.…”

Section: Introductionmentioning

confidence: 99%

Orientation Dependence of Hardness and Reduced Modulus of Single Crystal Sapphire Surface Measured by Nanoindentation

Okawa¹,

Clark²,

Tashiro³

et al. 2019

IJMSA

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Nowadays, industrial products are downsized, and the structure of materials is controlled with the nanometer precision, and it becomes very important to measure the mechanical properties of local area of bulk material. Especially the hardness and the elastic modulus are important mechanical properties. The orientation dependence of hardness and reduced modulus of single crystal sapphire surface was investigated by nanoindentation. The conventional technique to measure the hardness of materials using an optical micrometer cannot evaluate mechanical properties of a local region of several µm or less. However, nanoindentation can measure mechanical properties of very small surface area of materials, and is expected to detect the micro structure dependence of mechanical properties. Nanoindentation uses very small indenter made of diamond, and measures the indentation depth. The measured depth is converted to the indented area size using the area function. The area function of the indenter can be obtained using a standard material (fused quartz) in advance. Therefore nanoindentation can measure the indented area size without using an optical micrometer. In this report, it was shown that the nanoindentation could detect the structure dependence of mechanical properties of materials. The specimen was a single crystal sapphire with c -axis surface, and the indenter was Berkovich type diamond tip. It was confirmed that the nanoindentation hardness was the lowest, and the reduced modulus was the largest, when the ridge line of indenter was oriented to the m -axis of single crystal. The nanoindentation could detect the structure dependence of a local area of mechanical properties materials.

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Designing nanoindentation simulation studies by appropriate indenter choices: Case study on single crystal tungsten

Cited by 50 publications

References 55 publications

Towards an improved understanding of plasticity, friction and wear mechanisms in precipitate containing AZ91 Mg alloy

Towards an improved understanding of plasticity, friction and wear mechanisms in precipitate containing AZ91 Mg alloy

Dislocation Reaction Mechanism for Enhanced Strain Hardening in Crystal Nano-Indentations

Orientation Dependence of Hardness and Reduced Modulus of Single Crystal Sapphire Surface Measured by Nanoindentation

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