Cyclic microindentations on monocrystalline silicon in air and in water

This paper studies the difference in the mechanical response of monocrystalline silicon to cyclic microindentations in air and in water. It shows that in air the indentations with a spherical indenter generated consequent phase transformations. In the first indentation cycle, the decomposition featured amorphous phase at low maximum indentation load, Pmax, that was converged to a crystalline compound in repeated indentations. A high Pmax generated crystalline R8/BC8 phases only. After a few cycles, the transformed material behaved linearly elastically, and its properties became stable. However, when the same indentations were conducted in water, the property stabilization process of the transformed material was significantly slowed down, featuring non-linear elasticity. It seemed that at a high Pmax a chemical effect took place in the central part of the transformation zone.

Download Full-text

THE PLASTICITY OF MONOCRYSTALLINE SILICON UNDER NANOINDENTATION

International Journal of Modern Physics B ◽

10.1142/s0217979208051522 ◽

2008 ◽

Vol 22 (31n32) ◽

pp. 6022-6028 ◽

Cited By ~ 5

Author(s):

LI CHANG ◽

L. C. ZHANG

Keyword(s):

Plastic Deformation ◽

Shape Change ◽

Indentation Load ◽

Monocrystalline Silicon ◽

Displacement Curve ◽

Wide Range ◽

Rapid Loading ◽

Load Displacement ◽

The Difference ◽

Critical Contact

This paper focuses on a fundamental understanding of the plastic deformation mechanism in monocrystalline silicon subjected to nanoindentation. It was found that over a wide range of indentation loads from 100 μN to 30 mN and loading/unloading rates from 3.3 μN/s to 10 mN/s, the plasticity of silicon is mainly caused by stress-induced phase transitions. The results indicate that the critical contact pressure for phase transition at unloading is almost constant, independent of the maximum indentation load ( P max ) and loading/unloading rates. However, the shape of the load-displacement curves greatly relies on the loading/unloading conditions. In general, higher P max and lower unloading/loading rates favor an abrupt volume change and thus a discontinuity in the load-displacement curve, commonly referred to as pop-in and/or pop-out events; whereas smaller P max and rapid loading/loading processes tend to generate gradual slope changes of the curves. This study concludes that the difference in the curve shape change does not indicate the mechanism change of plastic deformation in silicon.

Download Full-text

“Pop-in” and “pop-out” effect in monocrystalline silicon. A statistical investigation

Journal of the Mechanical Behavior of Materials ◽

10.1515/jmbm-2017-0015 ◽

2017 ◽

Vol 26 (1-2) ◽

pp. 65-71

Author(s):

Alexandros D. Sidiropoulos ◽

Evghenii Harea ◽

Avraam A. Konstantinidis ◽

Elias C. Aifantis

Keyword(s):

Phase Transformations ◽

Statistical Investigation ◽

Indentation Load ◽

Monocrystalline Silicon ◽

Displacement Discontinuity ◽

Sudden Expansion ◽

Statistic Analysis ◽

Short Period ◽

Sudden Contraction ◽

Unloading Rate

AbstractPop-in and pop-out effects in silicon (Si) have long been known. They were evidenced in the indentation loading-unloading curves as a sudden displacement discontinuity. They consist in a sudden contraction (pop-in) or a sudden expansion (pop-out) of the material underneath the indenter in a short period of time and are attributed to Si phase transformations that take place during the nanoindentation procedure. In this paper, first we provide a statistic analysis of such pop-in/pop-out events depending on the maximum indentation load and second we examine the dependence of their appearance on the indentation loading-unloading rate.

Download Full-text

Phase transformations in (111) Si after spherical indentation

Journal of Materials Research ◽

10.1557/jmr.2009.0249 ◽

2009 ◽

Vol 24 (6) ◽

pp. 1967-1975 ◽

Cited By ~ 13

Author(s):

Ayesha J. Haq ◽

P.R. Munroe

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

High Pressure ◽

Phase Transformation ◽

Phase Transformations ◽

Indentation Load ◽

Spherical Indentation ◽

Cross Sectional ◽

Transformation Zone ◽

Transmission Electron

Phase transformations in (111) Si after spherical indentation have been investigated by cross-sectional transmission electron microscopy. Even at an indentation load of 20 mN, a phase transformation zone including the high-pressure crystalline Si phases was observed within the residual imprints. The volume of the transformation zone, as well as that of the crystalline phases increased with the indentation load. Below the transformation zone, slip was found to occur on {311} planes rather than on {111} planes, usually observed on indentation of (100) Si. The distribution of defects was asymmetric, and for indentation loads up to 80 mN, their density was significantly lower than that reported for (100) Si. The experimental observations correlated well with modeling of the applied stress through ELASTICA.

Download Full-text

Microcracking in Monocrystalline Silicon due to Indentation and Scratching

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.312.345 ◽

2006 ◽

Vol 312 ◽

pp. 345-350 ◽

Cited By ~ 2

Author(s):

Irena Zarudi ◽

Liang Chi Zhang

Keyword(s):

Critical Loads ◽

Indentation Load ◽

Spherical Indenter ◽

Monocrystalline Silicon ◽

Berkovich Indenter ◽

Transformation Zone

This paper discusses the cracking in monocrystalline silicon induced by microindentation with spherical and Berkovich indenters and scratching. It was found cracks always commenced in a specimen’s subsurface beneath the transformation zone. While using a Berkovich indenter the level of the maximum indentation load, Pmax, to initiate microcracking was lower than the case with a spherical indenter. In both indentation and scratching all microcracks took place at the sites of slip intersection or emanated from the bottom of a transformation zone. The paper also discussed critical loads for microcracking.

Download Full-text

Effect of Water on the Mechanical Response of Monocrystalline Silicon to Repeated Micro-Indentation

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.233-236.609 ◽

2003 ◽

Vol 233-236 ◽

pp. 609-614 ◽

Cited By ~ 10

Author(s):

Irena Zarudi ◽

Liang Chi Zhang ◽

Michael V. Swain

Keyword(s):

Mechanical Response ◽

Monocrystalline Silicon ◽

Effect Of Water ◽

Micro Indentation

Download Full-text

Numerical Analysis of Branch Mechanical Response to Loading

Arboriculture & Urban Forestry ◽

10.48044/jauf.2019.011 ◽

2019 ◽

Vol 45 (4) ◽

Author(s):

Barbora Vojáčková ◽

Jan Tippner ◽

Petr Horáček ◽

Luděk Praus ◽

Václav Sebera ◽

...

Keyword(s):

Finite Element ◽

Cross Sections ◽

Mechanical Response ◽

Mechanical Analysis ◽

Beam Deflection ◽

Design System ◽

Elliptical Cross ◽

Static Mechanical ◽

The Difference ◽

Tree Uprooting

Failure of a tree can be caused by a stem breakage, tree uprooting, or branch failure. While the pulling test is used for assessing the first two cases, there is no device-supported method to assess branch failure. A combination of the optical technique, pulling test, and deflection curve analysis could provide a device-supported tool for this kind of assessment. The aim of the work was to perform a structural analysis of branch response to static mechanical loading. The analyses were carried out by finite element simulations in ANSYS using beam tapered elements of elliptical cross-sections. The numerical analyses were verified by the pulling test combined with a sophisticated optical assessment of deflection evaluation. The Probabilistic Design System was used to find the parameters that influence branch mechanical response to loading considering the use of cantilever beam deflection for stability analysis. The difference in the branch’s deflection between the simulation and the experiment is 0.5% to 26%. The high variability may be explained by the variable modulus of the elasticity of branches. The finite element (FE) sensitivity analysis showed a higher significance of geometry parameters (diameter, length, tapering, elliptical cross-section) than material properties (elastic moduli). The anchorage rotation was found to be significant, implying that this parameter may affect the outcome in mechanical analysis of branch behavior. The branch anchorage can influence the deflection of the whole branch, which should be considered in stability assessment.

Download Full-text

A Method to Optimize the Electron Spectrum for Simulating Thermo-Mechanical Response to X-ray Radiation

Symmetry ◽

10.3390/sym12010059 ◽

2019 ◽

Vol 12 (1) ◽

pp. 59

Author(s):

Xianwen Ran ◽

Bo Wang ◽

Kun Zhang ◽

Wenhui Tang

Keyword(s):

Electron Spectrum ◽

Mechanical Response ◽

Least Squares Method ◽

Mechanical Deformation ◽

X Rays ◽

Linear Least Squares ◽

X Ray ◽

Relativistic Electron Beams ◽

Transport Code ◽

The Difference

The X-ray pulse originating from high altitude nuclear detonation (HAND) is mainly soft X-ray and its intensity is high enough to gasify the penetrated material and then lead to the severe thermo-mechanical deformation of unpenetrated material from the gasified blow-off effect. This effect cannot be directly reproduced in a lab for the lack of the X-ray source like HAND. At present, the low-energy relativistic electron beams resulting from an electron accelerator are usually used to approximately reproduce this effect, but the difference in the energy-deposited profile in materials between the electron and X-ray cannot be eliminated. In this paper, the symmetric linear least squares method was used to optimize the electron spectrum, and the general Monte Carlo N-Particle Transport Code calculations showed the optimized spectrum can produce the same energy-deposited profile in aluminum, copper, and tantalum with the soft X-rays like 1 keV or 3 keV spectrums. This indicates that it is possible to simulate the severe thermo-mechanical deformation resulting from HAND using the optimized electron spectrums.

Download Full-text

Microstructural Properties of Common Yew and Norway Spruce Determined with Silviscan

IAWA Journal ◽

10.1163/22941932-90000212 ◽

2009 ◽

Vol 30 (2) ◽

pp. 165-178 ◽

Cited By ~ 13

Author(s):

Daniel Keunecke ◽

Robert Evans ◽

Peter Niemz

Keyword(s):

Mechanical Behaviour ◽

Mechanical Response ◽

Elastic Anisotropy ◽

Longitudinal Direction ◽

Structural Features ◽

Structure Property ◽

Tangential Plane ◽

Cross Sectional ◽

X Ray ◽

The Difference

Yew wood holds a special position within the softwoods with regard to its exceptional elasto-mechanical behaviour. Despite a relatively high density, it is highly elastic in the longitudinal direction (the modulus of elasticity is low and the stretch to break high). In the radial-tangential plane, its elastic anisotropy is clearly less pronounced compared to other softwoods such as spruce. Knowledge of the anatomical organisation of yew wood is an indispensable precondition for the correct interpretation of this conspicuous mechanical behaviour. The aim of this study, therefore, was to interpret the difference in elasto-mechanical behaviour of yew and spruce (as a reference) through their relative microstructures as measured by SilviScan, a technology based on X-ray densitometry, X-ray diffractometry and optical microscopy. This system is able to measure a variety of structural features in a wood sample. The results reveal that the elasto-mechanical response of yew is primarily due to large microfibril angles and a more homogeneous cross-sectional tissue composition (regarding tracheid dimensions and density distribution) compared to spruce. With respect to structure-property relationships, it was concluded that yew wood combines properties of normal and compression wood and therefore takes an intermediate position between them.

Download Full-text

Crystallographic Texture of Nitinol and its Effects on Macrophage

Volume 2: Biomedical and Biotechnology Engineering ◽

10.1115/imece2010-37109 ◽

2010 ◽

Author(s):

Matthew Fonte ◽

Anil Saigal

Keyword(s):

Phase Transformations ◽

Cellular Proliferation ◽

Mechanical Response ◽

Solid Phase ◽

Bypass Graft ◽

Biological Response ◽

Coronary Bypass ◽

Inflammatory Cytokine Production ◽

Surface Finishes ◽

Coronary Bypass Graft

The use of Nitinol for medical purposes was first reported in the late 1960’s. Today Nitinol is commonly used for the manufacture of stents, which are primarily used in peripheral and coronary bypass graft interventions. The application of NiTi in orthopedics is an exciting prospect but one that has yet to be realized. Nitinol’s unique mechanical behavior is derived from the coordinated atomic movements manifesting in phase transformations from cubic austenite to monoclinic martensite. These phase transformations are solid-to-solid phase transformations that occur without diffusion or plasticity, potentially making them reversible. They involve changes in the crystalline structure that can be induced by changes in either temperature or stress. In addition to phase transformations, Nitinol’s mechanical strength is strongly dependent on the alloy composition and the method in which the material is processed, i.e. rolled, drawn, extruded, or forged. The mechanical work, combined with the intermediate heat treatment steps, contribute to modify microstructure, transformation temperatures and mechanical properties. These manufacturing processing steps lead to texturing (crystallographic alignment) of the material. Alignment of the atomic planes from texture in the polycrystalline material have a marked influence on the mechanical response by either limiting or promoting phase transformations and shape recovery strains. Nitinol is an established biomaterial, whose biocompatibility is heavily grounded on the inertness of titanium based oxides that usually dominate the surface exterior. Surfaces that vary significantly in their chemistry, topography and corrosion resistance have different degrees of biocompatibility. As such, a better understanding of the biological response of NiTi’s surfaces with different crystallographic textures in needed. In the present research, a macrophage study is performed whereby 6 plates that are highly textured NiTi with different surface finishes are incubated with cells for approximately 3 days and then tumor necrosis factor (TNF), a pro-inflammatory cytokine production and cellular proliferation are assessed.

Download Full-text