Depth-sensing indentation response of ordered silica foam

2004 ◽  
Vol 19 (1) ◽  
pp. 260-271 ◽  
Author(s):  
Yvete Toivola ◽  
Andreas Stein ◽  
Robert F. Cook
Keyword(s):  
Cell Walls ◽  
Colloidal Crystal ◽  
Pore Collapse ◽  
Depth Sensing ◽  
Load Range ◽  
Peak Displacement ◽  
Load Displacement ◽  
Colloidal Crystal Templating ◽  
Film Substrate ◽  
Microscopy Images

Depth-sensing indentation was applied to three-dimensionally ordered silica foams of two different pore diameters—500 nm and 850 nm—formed by colloidal crystal templating. The contact responses of indentations with Berkovich and hemispherical indentation tips are presented over a load range of 1 mN to 100 mN. Scanning electron microscopy images of residual indentation impressions showed homogeneous deformation for small loads in which the peak displacement was shallow relative to the film–substrate interface. The characteristics of the load–displacement responses changed from periodic discontinuities, associated with cell wall fracture and pore collapse, to smooth and increased stiffness, as a result of densification due to the accumulation of material under the indentation tip and proximity (and contact) of the substrate. Load–displacement responses were translated into pressure–volume space, in which the average pressure during indentation is a measure of the crushing pressure of the cell walls.

Indentation responses of time-dependent films on stiff substrates

2004 ◽  
Vol 19 (8) ◽  
pp. 2487-2497 ◽  
Author(s):  
Michelle L. Oyen ◽  
Robert F. Cook ◽  
John A. Emerson ◽  
Neville R. Moody
Keyword(s):  
Peak Load ◽  
Elastic Response ◽  
Depth Sensing ◽  
Indentation Tests ◽  
Unloading Rate ◽  
Loading And Unloading ◽  
Load Displacement ◽  
Film Substrate ◽  
Single Set ◽  
Substrate Influence

A viscous-elastic-plastic indentation model was extended to a thin-film system, including the effect of stiffening due to a substrate of greater modulus. The system model includes a total of five material parameters: three for the film response (modulus, hardness, and time constant), one for the substrate response (modulus), and one representing the length-scale associated with the film-substrate interface. The substrate influence is incorporated into the elastic response of the film through a depth-weighted elastic modulus (based on a series sum of film and substrate contributions). Constant loading- and unloading-rate depth-sensing indentation tests were performed on polymer films on glass or metal substrates. Evidence of substrate influence was examined by normalization of the load-displacement traces. Comparisons were made between the model and experiments for indentation tests at different peak load levels and with varying degrees of substrate influence. A single set of five parameters was sufficient to characterize and predict the experimental load-displacement data over a large range of peak load levels and corresponding degrees of substrate influence.

Fatigue at Nanoscale: An Integrated Stiffness and Depth Sensing Approach to Investigate the Mechanisms of Failure in Diamondlike Carbon Film

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
R. Ahmed ◽  
Y. Q. Fu ◽  
N. H. Faisal
Keyword(s):  
Failure Modes ◽  
Low Cycle Fatigue ◽  
Contact Stiffness ◽  
Depth Sensing ◽  
Load Range ◽  
Appreciable Change ◽  
Contact Depth ◽  
Substrate Interface ◽  
Diamondlike Carbon ◽  
Film Substrate

Nanoscale impact fatigue tests were conducted to comprehend the relative fatigue performance and failure modes of 100 nm thick diamondlike carbon (DLC) film deposited on a 4 in. diameter Si (100) wafer of 500 μm thickness. The nanofatigue tests were performed using a calibrated TriboIndenter equipped with Berkovich indenter in the load range of 300–1000 μN. Each test was conducted for a total of 999 fatigue cycles (a low cycle fatigue test). Contact depth in this load range varied from 10 to 30 nm. An integrated contact stiffness and depth sensing approach was adapted to understand the mechanisms of fatigue failure. The contact depth and stiffness data indicated some peculiar characteristics, which provided some insights into the mechanisms of cohesive and adhesive failure in thin films. Based on the contact stiffness and depth data, and surface observations of failed DLC films using atomic force microscope and scanning probe microscopy, a five-stage failure mechanism is proposed. The failure of films starts from cohesive failure via cracks perpendicular to the film/substrate interface, resulting in a decrease in contact depth with number of fatigue cycles and no appreciable change in contact stiffness. This is followed by film delamination at the film/substrate interface and release of elastic stored energy (residual stress) resulting in an increase in contact stiffness. Finally, as the film breaks apart the contact stiffness decreases with a corresponding increase in contact depth.

scholarly journals Constitutive Modeling of the Densification Behavior in Open-Porous Cellular Solids

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2731
Author(s):  
Ameya Rege
Keyword(s):  
Constitutive Model ◽  
Cell Walls ◽  
Compressive Strain ◽  
Pore Collapse ◽  
Compressive Response ◽  
Linear Elastic ◽  
Nonlinear Springs ◽  
Different Types ◽  
Point Of Intersection ◽  
Good Agreement

The macroscopic mechanical behavior of open-porous cellular materials is dictated by the geometric and material properties of their microscopic cell walls. The overall compressive response of such materials is divided into three regimes, namely, the linear elastic, plateau and densification. In this paper, a constitutive model is presented, which captures not only the linear elastic regime and the subsequent pore-collapse, but is also shown to be capable of capturing the hardening upon the densification of the network. Here, the network is considered to be made up of idealized square-shaped cells, whose cell walls undergo bending and buckling under compression. Depending on the choice of damage criterion, viz. elastic buckling or irreversible bending, the cell walls collapse. These collapsed cells are then assumed to behave as nonlinear springs, acting as a foundation to the elastic network of active open cells. To this end, the network is decomposed into an active network and a collapsed one. The compressive strain at the onset of densification is then shown to be quantified by the point of intersection of the two network stress-strain curves. A parameter sensitivity analysis is presented to demonstrate the range of different material characteristics that the model is capable of capturing. The proposed constitutive model is further validated against two different types of nanoporous materials and shows good agreement.

scholarly journals Temperature-Dependent Creep Behavior and Quasi-Static Mechanical Properties of Heat-Treated Wood

Forests ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 968
Author(s):  
Dong Xing ◽  
Xinzhou Wang ◽  
Siqun Wang
Keyword(s):  
Mechanical Properties ◽  
Creep Behavior ◽  
Cell Walls ◽  
Treated Wood ◽  
Crosslinking Reaction ◽  
Depth Sensing ◽  
Temperature Dependent ◽  
Heat Treated ◽  
Static Mechanical ◽  
Static Mechanical Properties

In this paper, Berkovich depth-sensing indentation has been used to study the effects of the temperature-dependent quasi-static mechanical properties and creep deformation of heat-treated wood at temperatures from 20 °C to 180 °C. The characteristics of the load–depth curve, creep strain rate, creep compliance, and creep stress exponent of heat-treated wood are evaluated. The results showed that high temperature heat treatment improved the hardness of wood cell walls and reduced the creep rate of wood cell walls. This is mainly due to the improvement of the crystallinity of the cellulose, and the recondensation and crosslinking reaction of the lignocellulose structure. The Burgers model is well fitted to study the creep behavior of heat-treated wood cell walls under different temperatures.

scholarly journals Synthesis of Metal Oxide Inverse Opals from Metal Nitrates by PMMA Colloidal Crystal Templating

2020 ◽  
Author(s):  
Xuyang Zhang ◽  
Christian Weinberger ◽  
Sabrina Amrehn ◽  
Xia Wu ◽  
Michael Tiemann ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Colloidal Crystal ◽  
Inverse Opals ◽  
Metal Nitrates ◽  
Colloidal Crystal Templating

An investigation of the creep processes in tin and aluminum using a depth-sensing indentation technique

1992 ◽  
Vol 7 (3) ◽  
pp. 627-638 ◽  
Author(s):  
V. Raman ◽  
R. Berriche
Keyword(s):  
Stress Exponent ◽  
Constant Load ◽  
Indentation Creep ◽  
Depth Sensing ◽  
Creep Tests ◽  
Si Substrates ◽  
Uniaxial Creep ◽  
Rate Versus ◽  
Deformation Properties ◽  
Film Substrate

Constant load creep experiments were conducted using a depth-sensing indentation instrument with indentation depths in the submicron range. Experiments were conducted on polycrystalline Sn and sputtered Al films on Si substrates. The results show that the plastic depth versus time curves and the strain rate versus stress plots from these experiments are analogous to those obtained from conventional creep experiments using bulk specimens. The value of the stress exponent for Sn is close to the reported values from uniaxial creep tests. Tests on Al films showed that the stress exponent is dependent on the indentation depth and is governed by the proximity to the film/substrate interface. Load change experiments were also performed and the data from these tests were analyzed. It is concluded that indentation creep experiments may be useful in elucidating the deformation properties of materials and in identifying deformation mechanisms.

Simulation of sub-micron indentation tests with spherical and Berkovich indenters

2001 ◽  
Vol 16 (7) ◽  
pp. 2149-2157 ◽  
Author(s):  
A. C. Fischer-Cripps
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Material Properties ◽  
Indentation Testing ◽  
Depth Sensing ◽  
Displacement Response ◽  
Analysis Methods ◽  
Detailed Treatment ◽  
Indentation Tests ◽  
Load Displacement

The present work is concerned with the methods of simulation of data obtained from depth-sensing submicron indentation testing. Details of analysis methods for both spherical and Berkovich indenters using multiple or single unload points are presented followed by a detailed treatment of a method for simulating an experimental load–displacement response where the material properties such as elastic modulus and hardness are given as inputs. A comparison between simulated and experimental data is given.

Fabricating Ordered Voids in a Colloidal Crystal Film–Substrate System by Using Organic Liquid Patterns as Templates

2002 ◽  
Vol 14 (24) ◽  
pp. 1799-1802 ◽  
Author(s):  
G. Lu ◽  
X. Chen ◽  
J. Yao ◽  
W. Li ◽  
G. Zhang ◽  
...  
Keyword(s):  
Colloidal Crystal ◽  
Organic Liquid ◽  
Crystal Film ◽  
Film Substrate

On the determination of the film hardness in hard film/substrate composites using depth-sensing indentation

2013 ◽  
Vol 39 (6) ◽  
pp. 6251-6263 ◽  
Author(s):  
N.A. Sakharova ◽  
M.C. Oliveira ◽  
J.M. Antunes ◽  
J.V. Fernandes
Keyword(s):  
Depth Sensing ◽  
Film Hardness ◽  
Film Substrate
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