Examination of Prestressed Coating/Substrate Systems Using Spherical Indentation—Determination of Film Prestress, Film Modulus, and Substrate Modulus

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
James A. Mills ◽  
Hang Xiao ◽  
Xi Chen
Keyword(s):  
Material Properties ◽  
Indentation Test ◽  
Spherical Indentation ◽  
Indentation Force ◽  
Forward Analysis ◽  
Substrate Properties ◽  
Error Sensitivity Analysis ◽  
Film Substrate

There have been many studies performed with respect to the indentation of thin films affixed to a corresponding substrate base. These studies have primarily focused on determining the mechanical properties of the film. It is the goal of this paper to further understand the role that the film plays and how a potential prestressing of this film has on both the film and substrate base. It is equally important to be able to understand the material properties of the substrate since during manufacturing or long-term use, the substrate properties may change. In this study, we establish through spherical indentation a framework to characterize the material properties of both the substrate and film as well as a method to determine the prestress of the film. It is proposed that through an initial forward analysis, a set of relationships are developed. A single spherical indentation test can then be performed, measuring the indentation force at two prescribed depths, and with the relationships developed from the forward analysis, the material properties of both the film and substrate can be determined. The problem is further enhanced by also developing the capability of determining any equibiaxial stress state that may exist in the film. A generalized error sensitivity analysis of this formulation is also performed systematically. This study will enhance the present knowledge of a typical prestressed film/substrate system as is commonly used in many of today’s engineering and technical applications.

Determination of Poisson’s Ratio by Spherical Indentation Using Neural Networks—Part I: Theory

2000 ◽  
Vol 68 (2) ◽  
pp. 218-223 ◽  
Author(s):  
N. Huber ◽  
A. Konstantinidis ◽  
Ch. Tsakmakis
Keyword(s):  
Poisson Ratio ◽  
Indentation Test ◽  
Inverse Function ◽  
Elastic Half Space ◽  
Spherical Indentation ◽  
Isotropic Hardening ◽  
Plastic Yield ◽  
Load Response ◽  
Reduced Modulus

When studying analytically the penetration of an indenter of revolution into an elastic half-space use is commonly made of the fraction Er=E/1−ν2. Because of this, only Er is determined from the indentation test, while the value of ν is usually assumed. However, as shown in the paper, if plastic deformation is involved during loading, the depth-load trajectory depends on the reduced modulus and, additionally, on the Poisson ratio explicitly. The aim of the paper is to show, with reference to a simple plasticity model exhibiting linear isotropic hardening, that the Poisson ratio can be determined uniquely from spherical indentation if the onset of plastic yield is known. To this end, a loading and at least two unloadings in the plastic regime have to be considered. Using finite element simulations, the relation between the material parameters and the quantities characterizing the depth-load response is calculated pointwise. An approximate inverse function represented by a neural network is derived on the basis of these data.

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.

scholarly journals New Inverse Method for Determining Uniaxial Flow Properties by Spherical Indentation Test

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Guoyao Chen ◽  
Xiaocheng Zhang ◽  
Jiru Zhong ◽  
Jin Shi ◽  
Qiongqi Wang ◽  
...  
Keyword(s):  
Tensile Properties ◽  
Inverse Method ◽  
Engineering Application ◽  
Indentation Test ◽  
New Method ◽  
Spherical Indentation ◽  
Flow Properties ◽  
Indentation Force ◽  
Non Destructive ◽  
Depth Curves

AbstractThe spherical indentation test has been successfully applied to inversely derive the tensile properties of small regions in a non-destructive way. Current inverse methods mainly rely on extensive iterative calculations, which yield a considerable computational costs. In this paper, a database method is proposed to determine tensile flow properties from a single indentation force-depth curves to avoid iterative simulations. Firstly, a database that contain numerous indentation force-depth curves is established by inputting varied Ludwic material parameters into the indentation finite elements model. Secondly, for a given experimental indentation curve, a mean square error (MSE) is designated to evaluate the deviation between the experimental curve and each curve in the database. Finally, the true stresses at a series of plastic strain can be acquired by analyzing these deviations. To validate this new method, three different steels, i.e. A508, 2.25Cr1Mo and 316L are selected. Both simulated indentation curves and experimental indentation curves are used as inputs of the database to inversely acquire the flow properties. The result indicates that the proposed approach provides impressive accuracy when simulated indentation curves are used, but is less accurate when experimental curves are used. This new method can derive tensile properties in a much higher efficiency compared with traditional inverse method and are therefore more adaptive to engineering application.

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.

Determination of Young's modulus by spherical indentation

1997 ◽  
Vol 12 (9) ◽  
pp. 2459-2469 ◽  
Author(s):  
N. Huber ◽  
D. Munz ◽  
Ch. Tsakmakis
Keyword(s):  
Finite Element ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Indentation Test ◽  
Spherical Indentation ◽  
Plastic Materials ◽  
Finite Element Calculations ◽  
Loading And Unloading ◽  
Elastic Plastic Materials

In this paper we consider elastic plastic materials that are tested by spherical indentation. Finite element calculations, which take into account nonlinear geometry properties, are carried out in order to determine the influence of the plastic history on the unloading response of the material. Two different iterative methods are proposed for determining Young's modulus under the assumption of a bilinear plasticity law. The first method deals with loading and unloading parts of the indentation test, whereas the second one deals only with unloading parts of the indentation test.

scholarly journals Analysis of O-Ring Seal Failure under Static Conditions and Determination of End-of-Lifetime Criterion

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1251 ◽  
Author(s):  
Anja Kömmling ◽  
Matthias Jaunich ◽  
Payam Pourmand ◽  
Dietmar Wolff ◽  
Mikael Hedenqvist
Keyword(s):  
Material Properties ◽  
Safety Margin ◽  
Mechanical Analysis ◽  
Butadiene Rubber ◽  
Dimensional Changes ◽  
Seal Failure ◽  
Ring Seal ◽  
Static Conditions

Determining a suitable and reliable end-of-lifetime criterion for O-ring seals is an important issue for long-term seal applications. Therefore, seal failure of ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (HNBR) O-rings aged in the compressed state at 125 °C and at 150 °C for up to 1.5 years was analyzed and investigated under static conditions, using both non-lubricated and lubricated seals. Changes of the material properties were analyzed with dynamic-mechanical analysis and permeability experiments. Indenter modulus measurements were used to investigate DLO effects. It became clear that O-rings can remain leak-tight under static conditions even when material properties have already degraded considerably, especially when adhesion effects are encountered. As a feasible and reliable end-of-lifetime criterion for O-ring seals under static conditions should include a safety margin for slight dimensional changes, a modified leakage test involving a small and rapid partial decompression of the seal was introduced that enabled determining a more realistic but still conservative end-of-lifetime criterion for an EPDM seal.

scholarly journals A New Inverse Method for Determining Uniaxial Flow Properties by Spherical Indentation Test

2021 ◽  
Author(s):  
Guoyao Chen ◽  
Xiaocheng Zhang ◽  
Jiru Zhong ◽  
Kaishu Guan
Keyword(s):  
Inverse Method ◽  
Engineering Application ◽  
Indentation Test ◽  
Experimental Curve ◽  
New Method ◽  
Spherical Indentation ◽  
Fe Model ◽  
Flow Properties ◽  
Indentation Force ◽  
Depth Curves

Abstract This study presents a new inverse method to determine tensile flow properties from a single indentation force-depth curves. A database is established to replace the iterative FE calculations in conventional inverse methods and therefore can process the indentation data more quickly and easily. An axisymmetric FE model is constructed to simulate the elastic-plastic response of indention. Assuming the materials follow Ludwic constitutive model, by systematically changing the material parameters, numerous indentation force-depth curves are extracted from simulation results to establish the database. For a given experimental indentation curves, a mean square error (MSE) is designated to evaluate the deviations between the experimental curve and each curve in the database. Then, the relation of deviations versus stresses are investigated to acquire the true stresses at a series of plastic strain. To validate the new method, three different steels, i.e. A508, 316L and 2.25Cr1Mo are selected. Both simulated indentation curves and experimental indentation curves are used as inputs of the database to inversely acquire the flow properties. The result indicates that the proposed approach provides impressive accuracy when simulated indentation curves is used, but is less accurate when an experimental curve is used. This new method can quickly derive tensile properties without iterative calculations that yield a considerable computational costs and are therefore adaptive to engineering application.

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