MECHANICAL PROPERTIES OF FERROELECTRIC CERAMIC NANOCOMPOSITES

2005 ◽  
Vol 04 (04) ◽  
pp. 607-613
Author(s):  
KWOK LUN LEE ◽  
AI KAH SOH ◽  
XIAO XING WANG ◽  
KIN WING KWOK
Keyword(s):  
Mechanical Properties ◽  
Indentation Size Effect ◽  
Ferroelectric Ceramic ◽  
Nano Particles ◽  
Compression Tests ◽  
Indentation Size ◽  
Depth Sensing ◽  
Reduced Modulus ◽  
Hardness Values ◽  
True Hardness

The micro- and nano-indentation techniques and compression tests were employed to determine the mechanical properties of PZT based composites dispersed with Al 2 O 3 nano-particles for comparison. Compared with the reduced modulus, the nano-hardness, which exhibited indentation size effect (ISE), seemed to be more sensitive to the indentation depth. The true hardness values were deduced, based on the modified proportional specimen resistance (PSR) model, from the depth sensing machine and micro-indenter. Both the micro- and nano-hardness of the nano-composites confirmed that the hardness was best improved by addition of 0.5wt% of Al 2 O 3.

Microstructure and Indentation Size-Effect in Pure Niobium Subjected to SPD via ECAP and HPT

2008 ◽  
Vol 584-586 ◽  
pp. 215-220 ◽  
Author(s):  
Jon Alkorta ◽  
C.J. Luis-Pérez ◽  
E.N. Popova ◽  
Martin Hafok ◽  
Reinhard Pippan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Dislocation Density ◽  
Size Effect ◽  
Indentation Size Effect ◽  
Outer Region ◽  
Rate Sensitivity ◽  
Indentation Size ◽  
Pure Niobium ◽  
Average Grain Size ◽  
Hardness Values

A commercially pure niobium has been subjected to SPD at room temperature ( ~0.11 TM) via ECAP (90º, route BC) up to 16 passes and via HPT up to shear strains γ =1000. ECAP-ed samples show an equiaxed structure after 8 and 16 passes with a decreasing average grain size. The results show that both the microstructure and mechanical properties of ECAP-ed samples do not reach a steady state up to at least 16 passes. HPT samples show at outer region a finer structural size but similar hardness values at similar equivalent strains. The nanoindentation results show an evident indentation size-effect even for the most deformed samples. The hardness values at the nano level converge for the recrystallized, the ECAP-ed and the HPT samples. This implies that, at the nano level, when the geometrically necessary dislocation density overcomes significantly the (initial) statistically stored dislocation density, hardness depends mainly on the physical intrinsic properties of the material (Burgers modulus, bulk modulus...) and the contribution of bulk mechanical properties (i.e., bulk yield strength) to hardness is smoothed down. Strain-rate sensitivity (SRS) of plastic strength has been also measured by means of rate-jump nanoindentation tests. The SRS is proportional to the inverse of hardness.

Characterization of Indentation Size Effect of Hardness Using a Loading Curve from Crystalline Materials

2007 ◽  
Vol 29-30 ◽  
pp. 55-58 ◽  
Author(s):  
Y.L. Chiu ◽  
W. George Ferguson
Keyword(s):  
Size Effect ◽  
Indentation Size Effect ◽  
Indentation Test ◽  
Indentation Size ◽  
Depth Sensing ◽  
Crystalline Materials ◽  
Nanoindentation Technique ◽  
Series Measurement ◽  
Hardness Values

Nanoindentation technique has been widely used for measuring mechanical properties from a very small volume of material. The hardness measured using the depth sensing nanoindentation technique often decreases with increasing indentation size, the so called indentation size effect (ISE)[1, 2]. It has been generally acknowledged that the ISE in crystalline materials originates from the density change of geometrically necessary dislocations (GND) needed to accommodate a permanent indentation imprint. Conventionally, to characterize an ISE often requires a series measurement of hardness values at different indentation size. Based on the celebrated Oliver-Pharr scheme[3]. We propose a method to derive the ISE from the loading curve of one single indentation test. The application and limitation of the proposed method will be discussed.

Micro-Hardness and Morphology of LDPE Influenced by Beta Radiation

2014 ◽  
Vol 606 ◽  
pp. 253-256 ◽  
Author(s):  
Martin Ovsik ◽  
Petr Kratky ◽  
David Manas ◽  
Miroslav Manas ◽  
Michal Stanek ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Hardness Test ◽  
Polymer Materials ◽  
Beta Radiation ◽  
Micro Hardness ◽  
X Ray Diffraction ◽  
Depth Sensing ◽  
Surface Layers ◽  
Hardness Values ◽  
Different Doses

This article deals with the influence of different doses of Beta radiation to the structure and mico-mechanical properties of Low-density polyethylene (LDPE). Hard surface layers of polymer materials, especially LDPE, can be formed by radiation cross-linking by β radiation with doses of 33, 66 and 99 kGy. Material properties created by β radiation are measured by micro-hardness test using the DSI method (Depth Sensing Indentation). Individual radiation doses caused structural and micro-mechanical changes which have a significant effect on the final properties of the LDPE tested. The highest values of micro-mechanical properties were reached at radiation dose of 66 and 99 kGy, when the micro-hardness values increased by about 21%. The changes were examined and confirmed by X-ray diffraction.

On the Indentation Modulus of Sintered Materials

2013 ◽  
Vol 586 ◽  
pp. 190-193
Author(s):  
Miriam Kupková ◽  
Martin Kupka
Keyword(s):  
Experimental Data ◽  
Indentation Size Effect ◽  
Displacement Curve ◽  
Indentation Modulus ◽  
Indentation Size ◽  
Depth Sensing ◽  
Nano Indentation ◽  
Individual Grains ◽  
Theoretical Results ◽  
Sintered Materials

When the depth-sensing (nano)indentation is applied to sintered samples, measured properties, which are expected to represent the material of an individual grain, seem to depend on the overall porosity of the macroscopic sample. To understand such a result, it is assumed that while the nanoindenter penetrates into the surface grain and probes the properties of its material, the grain itself serves as another, larger indenter indenting the rest of sample and probing the properties that represent the bulk of material rather than individual grains. Load vs. displacement curve reflects the synergetic response of these two “indenters” and so it contains information about the sample’s mechanical properties at both microscopic and macroscopic scales. Obtained theoretical results agree qualitatively with the experimental data (the dependence of the indentation modulus on the porosity of sample; the indentation size effect).

scholarly journals Effect of Beta Low Irradiation Doses on the Filled PA66 Measured by Micro-Indentation Test

2014 ◽  
Vol 1025-1026 ◽  
pp. 415-418
Author(s):  
Martin Ovsik ◽  
David Manas ◽  
Miroslav Manas ◽  
Michal Stanek ◽  
Martin Reznicek ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Glass Fibers ◽  
Indentation Test ◽  
Radiation Doses ◽  
Micro Hardness ◽  
Polyamide 66 ◽  
Depth Sensing ◽  
Micro Indentation ◽  
Hardness Values ◽  
Different Doses

The presented article deals with the research of micro-mechanical properties in the surface layer of modified Polyamide 66 filled by 30% of glass fibers. These micro-mechanical properties were measured by the Depth Sensing Indentation - DSI method on samples which were non-irradiated and irradiated by different doses of the β - radiation. Radiation doses used were 0, 15, 30 and 45 kGy for filled Polyamide 66 with the 6% cross-linking agent (triallyl isocyanurate). Individual radiation doses caused structural and micro-mechanical changes which have a significant effect on the final properties of the polyamide 66 tested. The highest values of micro-mechanical properties were reached at radiation dose of 30 kGy, when the micro-hardness values increased by about 64%. The aim of the article is to find out the influence of the radiation on the micro-hardness of the modified glass fiber-filled Polyamide 66 (PA66).

Investigation of the Mechanical Properties in Al/Al3Zr FGMs Fabricated by Centrifugal Casting Method

2009 ◽  
Vol 631-632 ◽  
pp. 379-384 ◽  
Author(s):  
Shimaa El Hadad ◽  
Hisashi Sato ◽  
Yoshimi Watanabe
Keyword(s):  
Mechanical Properties ◽  
Centrifugal Force ◽  
Volume Fraction ◽  
Centrifugal Casting ◽  
Compression Tests ◽  
Casting Method ◽  
Proof Stress ◽  
Force Direction ◽  
Hardness Values ◽  
Distribution Trends

Al-5mass%Zr FGMs fabricated by centrifugal casting method (CCM) have a very interesting microstructure. Since the intermetallics compounds of Al3Zr are plate in shape, Al3Zr platelet particles are almost oriented normal to the applied centrifugal-force direction. Considering this microstructure, the mechanical properties of Al/Al3Zr FGMs would vary for the same sample depending on the particles orientation and their volume fraction in the tested position. In this study, some mechanical properties of Al/Al3Zr FGMs were investigated. Al/Al3Zr FGMs rings were produced by CCM, under applied centrifugal force of 30, 60 and 120G (units of gravity). Microstructural observation along the centrifugal force direction was carried out. The platelet Al3Zr particles were almost oriented normal to the applied centrifugal force direction. The volume-fraction of Al3Zr particles increases close to the ring surface. Moreover, this distribution range of Al3Zr particles becomes broader with decreasing the applied centrifugal force. The same distribution trends were also observed for the hardness values. The Compression tests were also performed for further investigation of the mechanical properties. Samples under G=30 showed the lowest the 0.2%proof stress while those cast under G=120 had the highest 0.2% proof stress.

scholarly journals Characterization of strain amplitude-dependent behavior of hardness and indentation size effect of SS400 structural steel

2020 ◽  
Vol 14 (3) ◽  
pp. 15-25
Author(s):  
Nguyen Ngoc Vinh ◽  
Vu Quoc Anh ◽  
Hong Tien Thang
Keyword(s):  
Mechanical Properties ◽  
Cyclic Loading ◽  
Size Effect ◽  
Strain Rate ◽  
Structural Steel ◽  
Indentation Size Effect ◽  
Low Cycle Fatigue ◽  
Indentation Hardness ◽  
Gradient Plasticity ◽  
Indentation Size

In this paper, the continuous stiffness measurement (CSM) indentation is employed to investigate fatigue mechanical properties of structural steel under cyclic loading. For this purpose, several representative analytical approaches were introduced to estimate the basic mechanical properties including Young’s modulus and indentation hardness from the characteristics of the loading/unloading curves. Several experiments including CSM nanoindentation, low-cycle fatigue experiment for four strain amplitude levels, optical microscope (OM), and transmission electron microscopy (TEM) examinations were conducted to observe the variation characteristics of mechanical properties at the microscale and their micro-mechanisms. The microstructural evolution of the specimens deformed by the low-cycle fatigue was observed using the OM and TEM examinations. The standard nanoindentation experiments were then performed at different strain rate levels to characterize the influences of strain rate indentation on hardness of the material. The micro-mechanisms established based on the microstructural evolution and strain gradient plasticity theory were introduced to be responsible for the variation of indentation hardness under cyclic loading. Finally, the indentation size effect (ISE) phenomenon in SS400 structural steel was investigated and explained through the strain gradient plasticity theory regarding geometrically necessary dislocations underneath the indenter tip. The experimental results can be used for practical designs as well as for understanding the fatigue behavior of SS400 structural steel. Keywords: cyclic loading; fatigue; nanoindentation; indentation size effect; strain rate sensitivity; structural steel.

Atomic Force Microscope Measurements of the Hardness and Elasticity of Peritubular and Intertubular Human Dentin

1996 ◽  
Vol 118 (1) ◽  
pp. 133-135 ◽  
Author(s):  
J. H. Kinney ◽  
M. Balooch ◽  
S. J. Marshall ◽  
G. W. Marshall ◽  
T. P. Weihs
Keyword(s):  
Mechanical Properties ◽  
Atomic Force Microscope ◽  
Depth Sensing ◽  
Atomic Force ◽  
Silicon Cantilever ◽  
Human Dentin ◽  
Spatially Homogeneous ◽  
Calcified Tissues ◽  
20 Nm ◽  
Hardness Values

An atomic force microscope was used to measure the hardness and elasticity of fully-hydrated peritubular and intertubular human dentin. The standard silicon nitride AFM tip and silicon cantilever assembly were replaced with a diamond tip and stainless steel cantilever having significantly higher stiffness. Hardness was measured as the ratio of the applied force to the projected indentation area for indentations with depths from 10–20 nm. The sample stiffness was measured by imaging specimens in a force-modulated mode. Hardness values of 2.3 ± 0.3 GPa and 0.5 ± 0.1 GPa were measured for the peritubular and intertubular dentin, respectively. Stiffness imaging revealed that the elastic modulus of the peritubular dentin was spatially homogeneous; whereas, there was considerable spatial variation in the elasticity of the intertubular dentin. The atomic force microscope can be used to measure the mechanical properties of fully hydrated calcified tissues at the submicron level of spatial resolution, thus augmenting more traditional depth sensing probes.

scholarly journals The Effect of Isovalent Cation Substitution on Mechanical Properties of (CuxAg1–x)7SiS5I Superionic Mixed Single Crystals

2020 ◽  
Vol 65 (5) ◽  
pp. 453
Author(s):  
V. S. Bilanych ◽  
K. V. Skubenych ◽  
M. I. Babilya ◽  
A. I. Pogodin ◽  
I. P. Studenyak
Keyword(s):  
Mechanical Properties ◽  
Size Effect ◽  
Single Crystals ◽  
Room Temperature ◽  
Indentation Size Effect ◽  
Mixed Crystals ◽  
Cation Substitution ◽  
Compositional Dependence ◽  
Indentation Size ◽  
Stockbarger Method

(CuxAg1−x)7SiS5I mixed crystals were grown by the Bridgman–Stockbarger method. The microhardness measurements are carried out at room temperature using a Vickers indenter. The compositional dependence of the microhardness is studied. The dependence of the microhardness on the depth of imprint is analyzed in the model of geometrically necessary dislocations. The indentation size effect is observed. It is established that the microhardness of (CuxAg1−x)7SiS5I mixed crystals decreases at the substitution of Cu atoms by Ag atoms.

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