Spherical Indentation Testing on Ballistic Gelatin and Perma-Gel

2014 ◽  
Author(s):  
Amélie Caron-Laramée ◽  
Martin Brouillette
Keyword(s):  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Indentation Test ◽  
Spherical Indentation ◽  
Strain Rates ◽  
Dynamic Indentation ◽  
Hertz Theory ◽  
Static Indentation ◽  
Indentation Tests ◽  
Ballistic Gelatin

This paper reports on a series of indentation tests performed on ballistic gelatin (10%) and Perma-Gel. In these experiments, both gels were submitted to strain rates varying from 0.1 and 2.7 s−1 in quasi-static indentation. Two methods were used to evaluate the Young’s modulus from quasi-static indentation test: the Hertz theory and the Oliver-Pharr model. The dependence of strain rate was also analyzed. Finally, dynamic indentation tests were performed on both gels at frequencies of 0.1 and 1.0 Hz to evaluate the gel’s viscoelastic properties characterized by the storage modulus, the loss modulus and the phase angle.

Identification of Hardening Parameters of Metals From Spherical Indentation Tests

2001 ◽  
Vol 123 (3) ◽  
pp. 245-250 ◽  
Author(s):  
S. Kucharski ◽  
Z. Mro´z
Keyword(s):  
Indentation Test ◽  
Strain Curve ◽  
Load Level ◽  
Spherical Indentation ◽  
Indentation Tests ◽  
Geometric Sequence ◽  
Loading And Unloading ◽  
Plastic Hardening ◽  
Hardening Curve ◽  
Two Parameters

The identification method of hardening parameters specifying stress-strain curve is proposed by applying spherical indentation test and measuring the penetration depth during loading and unloading. The loading program is composed of a geometric sequence of loading and partial unloading steps from which the variation of permanent penetration with load level is determined. This data is used for specification of two parameters k and m occurring in the plastic hardening curve εp=σ/k1/m, where εp denotes the plastic strain.

Dynamic indentation response of ZrHf-based bulk metallic glasses

2007 ◽  
Vol 22 (2) ◽  
pp. 478-485 ◽  
Author(s):  
Ghatu Subhash ◽  
Hongwen Zhang
Keyword(s):  
Shear Band ◽  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Shear Bands ◽  
Indentation Hardness ◽  
Strain Rates ◽  
Dynamic Indentation ◽  
Confinement Pressure ◽  
Static Indentation ◽  
Deformation Features

Static and dynamic Vickers indentations were performed on ZrHf-based bulk amorphous alloys. A decrease in indentation hardness was observed at higher strain rates compared with static indentation hardness. For equivalent loads, dynamic indentations produced more severe deformation features on the loading surface than static indentations. Using bonded interface technique, the induced shear band patterns beneath the indentations were studied. In static indentations, the majority of the deformation was primarily accommodated by closely spaced semicircular shear bands surrounding the indentation. In dynamic indentations two sets of widely spaced semicircular shear bands with two different curvatures were observed. The observed shear band patterns and softening in hardness were rationalized based on the variations in the confinement pressure, strain rate, and temperature within the indentation region during dynamic indentations. It is also proposed that free volume migration and formation of nano-voids leading to cracking are favored due to adiabatic heating and consequently cause the observed softening at high strain rates.

Local Mechanical Characterization of Metal Foams by Nanoindentation

2015 ◽  
Vol 662 ◽  
pp. 59-62 ◽  
Author(s):  
Jiří Němeček ◽  
Vlastimil Kralik
Keyword(s):  
Cell Walls ◽  
Plastic Material ◽  
Spherical Indentation ◽  
Isotropic Hardening ◽  
Plastic Properties ◽  
Macro Scale ◽  
Static Indentation ◽  
Indentation Tests ◽  
Constitutive Parameters

This paper deals with microstructure and micromechanical properties of two commercially available aluminium foams (Alporas and Aluhab). Since none of the materials is available in a bulk and standard mechanical testing at macro-scale is not possible the materials need to be tested at micro-scale. To obtain both elastic and plastic properties quasi-static indentation was performed with two different indenter geometries (Berkovich and spherical tips). The material phase properties were analyzed with statistical grid indentation method and micromechanical homogenization was applied to obtain effective elastic wall properties. In addition, effective inelastic properties of cell walls were identified with spherical indentation. Constitutive parameters related to elasto-plastic material with linear isotropic hardening (the yield point and tangent modulus) were directly deduced from the load–depth curves of spherical indentation tests using formulations of the representative strain and stress introduced by Tabor.

MATERIAL CHARACTERIZATION BASED ON INSTRUMENTED AND SIMULATED INDENTATION TESTS

2009 ◽  
Vol 01 (01) ◽  
pp. 61-84 ◽  
Author(s):  
ZISHUN LIU ◽  
EDY HARSONO ◽  
SOMSAK SWADDIWUDHIPONG
Keyword(s):  
Neural Network ◽  
Material Properties ◽  
Indentation Test ◽  
Network Models ◽  
Spherical Indentation ◽  
Instrumented Indentation ◽  
Neural Network Models ◽  
Advantages And Disadvantages ◽  
Indentation Tests ◽  
Load Displacement

This paper reviews various techniques to characterize material by interpreting load-displacement data from instrumented indentation tests. Scaling and dimensionless analysis was used to generalize the universal relationships between the characteristics of indentation curves and their material properties. The dimensionless functions were numerically calibrated via extensive finite element analysis. The interpretation of load-displacement curves from the established relationships was thus carried out by either solving higher order functions iteratively or employing neural networks. In this study, the advantages and disadvantages of these techniques are highlighted. Several issues in an instrumented indentation test such as friction, size effect and uniqueness of reverse analysis algorithms are discussed. In this study, a new reverse algorithm via neural network models to extract the mechanical properties by dual Berkovich and spherical indentation tests is introduced. The predicted material properties based on the proposed neural network models agree well with the numerical input data.

Determination of stress–strain curves of materials at high strain rates using dynamic indentation technique

2020 ◽  
pp. 030932472094864
Author(s):  
Samaneh Pourolajal ◽  
Gholam Hossein Majzoobi
Keyword(s):  
Indentation Depth ◽  
Indentation Test ◽  
Material Model ◽  
Optimization Techniques ◽  
Strain Rates ◽  
Stress Strain ◽  
Dynamic Indentation ◽  
Simulation And Optimization ◽  
Load Indentation

Determination of dynamic behaviour of materials is a serious challenge in mechanics of materials. In this investigation, a new approach is proposed to obtain stress–strain curves of metals from dynamic indentation test. This approach is based on a combined experiment, simulation, and optimization techniques. In the experiment side, a conical penetrator is shot against the material as the target. The load–indentation depth curve is obtained from the dynamic indentation test. The indentation test is simulated using Ls-dyna and the numerical load–indentation depth is obtained from the simulation. The stress–strain curves are defined by Johnson–Cook material model. From optimization of the difference between the experimental and numerical load–indentation depth curves, the constants of the material model are identified. The material model is validated also by stress–strain curves obtained from quasi-static test conducted using Instron and dynamic tests conducted using Split Hopkinson Bar. The results show a close agreement between the model prediction and the experimental stress–strain curves for different strain rates.

Spherical indentation of ductile power law materials

2004 ◽  
Vol 19 (9) ◽  
pp. 2641-2649 ◽  
Author(s):  
Roberta Mulford ◽  
Robert J. Asaro ◽  
Robert J. Sebring
Keyword(s):  
Power Law ◽  
Contact Surface ◽  
Indentation Test ◽  
Strain Curve ◽  
Spherical Indentation ◽  
Actual Contact ◽  
Indentation Tests ◽  
Surface Profiles ◽  
Constitutive Parameters ◽  
Versus Strain

A procedure for extracting simple constitutive parameters from microindentationtests is described. The analysis used to interpret the indentation tests is based onthe analysis of the spherical indentation test developed by Hill et al. for power law materials. Indentation tests are supplemented by scanning interference microscopyof the residual indented surface profiles and a method is suggested for using the residual surface profiles to estimate the actual contact surface. This, in turn, allowsfor the construction of the entire stress versus strain curve.

Orthogonal Properties of Human Trabecular Bone by Spherical Indentation Test

2006 ◽  
Vol 326-328 ◽  
pp. 793-796
Author(s):  
Tae Soo Bae ◽  
Tae Soo Lee ◽  
Kui Won Choi
Keyword(s):  
Trabecular Bone ◽  
Apparent Density ◽  
Indentation Test ◽  
Spherical Indentation ◽  
Power Relationship ◽  
Ct Scanner ◽  
Diamond Blade ◽  
Custom Made ◽  
Indentation Tests

The elastic modulus and the apparent density of the trabecular bone were evaluated from spherical indentation tests and Computed Tomography and their relationship was quantified. After the femurs were prepared and embedded with respect to their anatomical orientation, the transverse planes of the trabecular bone specimens were scanned at 1mm intervals using a CT scanner. The metaphyseal regions were sectioned with a diamond-blade saw, producing 8mm cubes. Using a custom-made spherical indentation tester, the cubes were mechanically tested in the anteriorposterior (AP), medial-lateral (ML), and inferior-superior (IS) directions. After determination of modulus from the mechanical testing, the apparent densities of the specimens were measured. The results showed that the IS modulus was significantly greater than both the AP and ML moduli with the AP modulus greater than the ML modulus. This demonstrated that orthogonality was a structural characteristic of the trabecular bone. The power relationship between the modulus and the apparent density was also found to be statistically significant.

Inferring the ballistic resistance of thick targets from static deep indentation tests

2018 ◽  
Vol 9 (3) ◽  
pp. 347-361 ◽  
Author(s):  
Zvi Rosenberg ◽  
Alon Malka-Markovitz ◽  
Roman Kositski
Keyword(s):  
Indentation Test ◽  
Rate Sensitivity ◽  
Ballistic Resistance ◽  
Cavitation Phenomenon ◽  
Brittle Solids ◽  
Static Indentation ◽  
Rigid Projectile ◽  
Indentation Tests ◽  
Deep Indentation ◽  
Soft Target

The aim of this work is to demonstrate that one can derive the value of the dynamic resistive stress, which a given target exerts on a rigid projectile, by following the force needed to push a rigid indenter into the target in a static deep indentation test. In this study, we used a relatively soft target made of a lead-antimony alloy and a concrete target, representing ductile metals and brittle solids, respectively. For both targets, we followed the force–distance curves obtained by the deep indentations of hard punches, as they were slowly pushed in the targets by a loading frame. The effect of friction during these tests was taken into account in order to obtain the net axial resisting stresses, which were applied by the targets on these indenters. These static resisting stresses, at deep penetrations, were compared with the dynamic resisting stresses, which were inferred from the impacts of armor-piercing projectiles on these targets. The good agreement between the two sets of values strongly enhances the claim that one can use static indentation tests in order to estimate the ballistic resistance of various targets to rigid projectile penetration. The effect of strain rate sensitivity is highlighted by the test results for both the metallic and concrete targets. In addition, important insights concerning the cavitation phenomenon in the penetration of rigid projectiles are also highlighted in this work.

Quasi-Static Indentation Test on Composite Sandwich Panels with Foam Core

2013 ◽  
Vol 718-720 ◽  
pp. 214-218 ◽  
Author(s):  
Zong Hong Xie ◽  
Qun Yan ◽  
Jiang Tian ◽  
Xiao Yu Liu
Keyword(s):  
Experimental Studies ◽  
Sandwich Panels ◽  
Indentation Test ◽  
Foam Core ◽  
Damage Propagation ◽  
Indentation Force ◽  
Test Standards ◽  
Composite Sandwich ◽  
Static Indentation ◽  
Indentation Tests

In accordance to ASTM test standards, this paper presents experimental studies on quasi-static indentation tests on sandwich panels with carbon fiber reinforced facesheet and foam core. The indentation force vs. displacement curves were obtained. A series of tests with different indentation depth were carried out to study the damage modes and damage propagation process of foam core sandwich panels under quasistatic indentation force.

An Expanding Cavity Model for Indentation Analysis of Shape Memory Alloys

2019 ◽  
Vol 87 (3) ◽  
Author(s):  
J. Anuja ◽  
R. Narasimhan ◽  
U. Ramamurty
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Indentation Test ◽  
Spherical Indentation ◽  
Cavity Model ◽  
Functional Responses ◽  
Indentation Tests ◽  
Indentation Analysis ◽  
Analytical Expressions

Abstract 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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