Elastic indentation problems in thin films on substrate systems (original) (raw)
Related papers
Philosophical Magazine, 2006
Several models have been developed to extract the intrinsic elastic modulus of thin films from the composite film/substrate modulus value obtained from indentation tests on coated systems. Either analytical, semi-analytical or empirical, they generally propose an expression of the composite modulus as a function of the film and substrate elastic moduli and of the film thickness. When the substrate properties and the film thickness are known, the expression without adjustable parameter contains only the film elastic modulus as unknown parameter, which can thus be deduced.
2013
Nanoindentation of thin film-thick substrate system is commonly employed tool to measure the mechanical properties of materials. Finite element simulation (FEM) of nanoindentation experiment can overcome the expense and limitations of sophisticated test procedure. This study focused on the FEM simulation of nanoindentation test in ABAQUS environment to check the effects of film-substrate material properties and geometry. The indentation process in concern involves a two dimensional axisymmetric model where a thin film is placed above substrate and indented by a rigid indenter for specific friction condition. Modulus of elasticity and hardness of thin film has been calculated from analysis results using empirical relationship. For this study, two types of thin film properties i.e. elastic-perfectly plastic and elasto-plastic with specific strain hardening condition are taken for consideration. Firstly, different elastic substrate materials have been used under elastic-perfectly plastic thin film to observe the substrate strength effects. The analysis has been conducted for four different indentation depths to incorporate the influence of depth of penetration also. Secondly, similar analysis has performed for strain-hardening film material for all substrate strength to compare the behavior with perfectly plastic case. Finally, thickness of substrate layer has also been varied to observe the effect of substrate thickness under nanoindentation test. The simulation result shows that substrate strength effect is pronounced on film modulus determination whereas hardness is not significantly sensitive to this effect. Substrate modulus with magnitude of smaller or near film modulus can predict reasonable value of film modulus whereas high strength substrate modulus i.e. rigid body as a substrate produces extremely high film modulus. Indentation derived film hardness affects significantly than elastic modulus due to incorporation of strain hardening in thin film properties. In addition, calculated film properties increases with the increment of indentation depth but shows negligible change due to the variation of substrate thickness.
Spherical indentation of an elastic thin film on an elastic-ideally plastic substrate
Protective harder thin films are commonly deposited on soft ductile substrates to tailor many surface properties in a controlled fashion. To improve the reliability of thin film or to measure their mechanical properties instrumented indentation tests are routinely performed. A comprehensive understanding of the relation among load, displacement and contact radius is necessary for reliable property estimation. In this research, finite element method is used to perform an accurate numerical analysis of the normal indentation of an elastic-plastic layered half-space by a rigid sphere. The effects of yield strain of the substrate on the onset of plasticity are explored. The indentation load and depth as a function of contact size in non-dimensional form are calculated. These results are compared with those of the layered elastic system (elastic layer on elastic substrate) and bulk plastic solid. Competing deformation regimes are presented in the form of an indentation map.
The effects of mechanical properties of thin films on nano-indentation data: Finite element analysis
Computational Materials Science, 1997
Mechanical properties of thin films are commonly determined using nano or ultra-microhardness indentation. Understanding the relationship of the measured data and the mechanical properties of the indented materials is of importance in order to obtain reliable mechanical properties, particularly of the thin films. Using finite element analysis, the effects of the elastic modulus, yield strength, and strain hardening of the film on indentation data are analysed and discussed for the indentation with 2, 8, 10 and 50 pm radius indenters. Elastic modulus of the films on a single ductile substrate shows relatively small influence whereas yield strength and strain hardening are found to have significant effect on the measured data. 0 1997 Published by Elsevier Science B.V.
Adhesive elastic contact between a symmetric indenter and an elastic film
International Journal of Solids and Structures, 2009
This paper examines the frictionless adhesive elastic contact problem of a rigid sphere indenting a thin film deposited on a substrate. The result is then used to model the elastic phase of micro-nanoscale indentation tests performed to determine the mechanical properties of coatings and films. We investigate the elastic response including the effects of adhesion, which, as the scale decreases to the nano level, become an important issue. In this paper, we extend the Johnson-Kendall-Roberts, Derjaguin-Muller-Toporov, and Maugis-Dugdale half-space adhesion models to the case of a finite thickness elastic film coated on an elastic substrate. We propose a simplified model based on the assumption that the pressure distribution is that of the corresponding half-space models; in doing so, we investigate the contact radius/film thickness ratio in a range where it is usually assumed the half-space model. We obtain an analytical solution for the elastic response that is useful for evaluating the effects of the film-thickness, the interface film-substrate conditions, and the adhesion forces. This study provides a guideline for selecting the appropriate film thickness and substrate to determine the elastic constants of film in the indentation tests.
A new paradigm in thin film indentation
Journal of Materials Research, 2010
A new method to accurately and reliably extract the actual Young's modulus of a thin film on a substrate by indentation was developed. The method involved modifying the discontinuous elastic interface transfer model to account for substrate effects that were found to influence behavior a few nanometers into a film several hundred nanometers thick. The method was shown to work exceptionally well for all 25 different combinations of five films on five substrates that encompassed a wide range of compliant films on stiff substrates to stiff films on compliant substrates. A predictive formula was determined that enables the film modulus to be calculated as long as one knows the film thickness, substrate modulus, and bulk Poisson's ratio of the film and the substrate. The calculated values of the film modulus were verified with prior results that used the membrane deflection experiment and resonance-based methods. The greatest advantages of the method are that the standard Oliver ...
A Discontinuous Elastic Interface Transfer Model of Thin Film Nanoindentation
Experimental Mechanics, 2009
A new model of thin film indentation that accounted for an apparent discontinuity in elastic strain transfer at the film/substrate interface was developed. Finite element analysis suggested that numerical values of strain were not directly continuous across the interface; the values in the film were higher when a soft film was deposited on a hard substrate. The new model was constructed based on this discontinuity; whereby, separate weighting factors were applied to account for the influence of the substrate in strain developed in the film and vice-versa. By comparing the model to experimental data from thirteen different amorphous thin film materials on a silicon substrate, constants in each weighting factor were found to have physical significance in being numerically similar to the bulk scale Poisson's ratios of the materials involved. When employing these material properties in the new model it was found to provide an improved match to the experimental data over the existing Doerner and Nix and Gao models. Finally, the model was found to be capable of assessing the Young's modulus of thin films that do not exhibit a flat region as long as the bulk Poisson's ratio is known.
Dimensionless Analysis to Determine Elastoplastic Properties of Thin Films by Indentation
Coatings
By assuming the elastoplastic properties of thin-film materials, a reverse analysis method is proposed by deriving a dimensionless function for the indentation process. The substrate effect is taken into account by assuming a perfect interface between thin-film and substrate materials. In order to obtain the applied load–penetration depth (P-h) curves, the indentation process is numerically modeled as an axisymmetric problem with a rigid-body Berkovich indenter on the semi-infinite substrate when performing finite element (FE) simulations. As a typical soft film/hard substrate problem, the elastic substrate is assumed and the power–law model is used to describe the constitutive properties of thin-film materials. Varying elastic modulus (10–50 GPa), yield strength (60–300 MPa), and hardening exponent (0.1–0.5) characterize different elastoplastic mechanical properties of thin-film materials with film thickness of 10–30 μm. Owing to the good trending P-h curves with the maximum indent...
Surface and Interface Analysis, 2014
In this work, we focused on investigations of mechanical properties of SiN x and diamond-like carbon thin films deposited by plasma-enhanced chemical vapour deposition method for application in optical devices or solar cells. Mechanical properties of thin films deposited on clean and oxidized silicon substrates were determined by nanoindentation. The main difficulty with the characterization of thin films using nanoindentation method is related to the influence of the substrate on the measured properties of thin layers. We proposed a method to determine the mechanical properties (hardness and Young's modulus) of thin films in single-layer/substrate or double-layer/substrate system through combining the finite element method, nanoindentation experiments and numerical simulations. In this study, a three-dimensional numerical model of nanoindentation tests performed with Vickers diamond indenter was examined to determine the stress distributions during measurement with various maximum loads. The hardness and Young's modulus of the examined layers were determined using two types of procedures, depending on the von Mises equivalent stress distribution obtained at the maximum load. If the size of an elastically deformed region was sufficiently small compared with the thickness of the measured layers, we applied a standard method of measuring at the depth equal to 10% of the layer thickness; otherwise, an approximation method was used to reduce the substrate influence.
Mechanical properties of thin film–substrate systems
Journal of Materials Processing Technology, 2003
This paper is devoted to a study of the mechanical properties of thin film-substrate systems using indentation methods. The magnitude of the load used for indentation, the properties of the system thin film-substrate and the thickness of the thin film, determine the type of material properties which can be analyzed such as microhardness (nanohardness), adhesive and cohesive behavior, fracture properties and wear resistance. Nanoindentor Shimadzu DUH2, scratch tester CSEM Revetest and common hardness tester Ernst were used for the investigation of mechanical properties. Useful indentation methods and the magnitudes of the load are discussed for each mechanical property.