A numerical study of the indentation mechanics of shape memory alloys in different temperature regimes

Anuja, J.; Narasimhan, R.; Ramamurty, Upadrasta

doi:10.1016/j.mechmat.2019.103212

Cited by 10 publications

(12 citation statements)

References 47 publications

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“…Lawn et al [72] suggested that the widely-used expanding cavity models for describing the deformation fields underneath indenter are then no longer valid when a material undergoes densification by compaction within the immediate contact zone of a sharp indenter. (This is also true when phase transformations occur underneath the indenter [73,74].) This is because of the intense hydrostatic compressive stresses that render the volume of the indentation to be more readily accommodated within the compaction zone, diminishing the intensity of any residual stresses.…”

Section: Crack Initiation and Cracking Resistancementioning

confidence: 99%

Indentation of glasses

Rouxel

Jang

Ramamurty

2021

Progress in Materials Science

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Section: Crack Initiation and Cracking Resistancementioning

confidence: 99%

Indentation of glasses

Rouxel

Jang

Ramamurty

2021

Progress in Materials Science

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“…Furthermore, it is important to note that the ECM solution derived in this work is valid only up to indentation strain of 0.04, which would correspond to normalized indentation depth h/R of 0.02. Recent finite element simulations by Anuja et al [10,12] have shown that at such low normalized indentation depths, plastic strains beneath the indenter are negligible and therefore would have little influence on the indentation response irrespective of temperature. [9] along with ECM solution given by Eq.…”

Section: Discussionmentioning

confidence: 99%

“…For example, the yield strength under uniaxial compression is related to p m as p m ≃ 3σ y for rigid-perfectly plastic materials [8]. However, interpreting the indentation response of SMAs is a challenging task as the non-homogeneous stress state underneath the indenter can invoke a complex interaction between SIMT and plastic deformation [9][10][11][12]. Therefore, theoretical studies and numerical modeling are essential to obtain useful information about elastic and transformation properties from indentation test results [13].…”

Section: Introductionmentioning

confidence: 99%

An Expanding Cavity Model for Indentation Analysis of Shape Memory Alloys

Anuja

Narasimhan

Ramamurty

2019

Journal of Applied Mechanics

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The mechanical and functional responses of shape memory alloys (SMAs), which are often used in small volume applications, can be evaluated using instrumented indentation tests. However, deciphering the indentation test results in SMAs can be complicated due to the combined effects of the non-uniform state of stress underneath the indenter and stress-induced phase transformation. To address this issue, an expanding cavity model (ECM) applicable to spherical indentation of SMAs is developed in this work based on an analytical solution for an internally pressurized hollow sphere. Analytical expressions for key indentation parameters such as the mean contact pressure and size of the transforming zone are obtained, whose validity is evaluated by recourse to finite element simulations and published experimental data for a Ni–Ti alloy. It is shown that the ECM predicts the above parameters reasonably well for indentation strains varying from 0.01 to 0.04. Also, a method is proposed to determine the critical stress required to initiate phase transformation under uniaxial compression based on the application of the ECM to interpret the indentation stress–strain response.

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“…Microindentation and nanoindentation are some of the most important and efficient non-destructive techniques to measure the mechanical properties (i.e., elastic moduli, hardness) of materials at small scale. In the last years, many efforts were spent in modeling micro-and nanoindentation for the numerical characterization of SMAs [33][34][35][36][37] and several experiments were also carried out to study the local transformation mechanisms by nanoindentation [38][39][40][41][42][43][44][45].…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Local Functional Evolution in NiTi Shape Memory Alloys by Multicycle Nanoindentations

Furgiuele

Greco

Magarò

et al. 2023

Shap. Mem. Superelasticity

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In this work, NiTi pseudoelastic alloy was studied to investigate the local functional response using nanoindentation. Two different experiments were carried out to analyze the recovery capability and stiffness evolution: single indentation tests in depth control mode, for maximum penetration depth ranging from 500 to 3000 nm and multicycle indentations, which consist in indenting the same point multiple times. For both cases, a sharp (Berkovich) and a blunt (spherical) tip were used. For a better interpretation of the results, microstructural analysis and finite element simulations were also carried out. A stiffer response and a lower recovery capability of the material are recorded for Berkovich indentations compared to the spherical ones. In multicycle tests, it was observed a first relative quick functional degradation of the material response, in terms of recovery capability, and a subsequent stabilization that typically occurs after 100–150 cycles. Furthermore, for both tips, it was observed that the material stiffness tends to decrease with the number of indentation cycles and by increasing the penetration depth. These results are attributed to the different strain maps induced by the different geometries of the tips, the evolution of the martensitic region in the process zone, and the interactions with the microstructure.

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A numerical study of the indentation mechanics of shape memory alloys in different temperature regimes

Cited by 10 publications

References 47 publications

Indentation of glasses

Indentation of glasses

An Expanding Cavity Model for Indentation Analysis of Shape Memory Alloys

Analysis of the Local Functional Evolution in NiTi Shape Memory Alloys by Multicycle Nanoindentations

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