Characterization of Material Parameters by Reverse Finite Element Modelling Based on Dual Indenters Vickers and Spherical Indentation (original) (raw)
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Applied Mechanics and Materials, 2014
In this work, finite element (FE) model of spherical indentation has been developed and validated. The relationships between constitutive materials parameters (σy and n) of elastic-plastic materials, indentation P-h curves and hardness on spherical indenters has been systematically investigated by combining representative stress analysis and FE modelling using steel as a typical model material group. Parametric FE models of spherical indentation have been developed. Two new approaches to characterise the P-h curves of spherical indentation have been developed and evaluated. Both approaches were proven to be adequate and effective in predicting indentation P-h curves. The concept and methodology developed is to be used to predict Rockwell hardness value of materials through direct analysis and validated with experimental data on selected sample of steels. The Hardness predicted are compared with the experimental data and showed a good agreement. The approaches established was success...
Determination of the hardness and elastic modulus from continuous vickers indentation testing
Journal of Materials Science, 1996
Continuous Vickers (Hv) indentation tests were performed on different materials (ion crystals, metals, ceramics, silica glass and plastic). Load-indentation depth curves were taken during the loading as weil as during the unloading period by a computer controlled hydraulic mechanical testing machine (MTS 810). The indentation work measured both the loading and the unloading periods, and these were used for the evaluation of parameters characterizing the materials. It was found empirically that there were linear connections between the maximum load to the power 312 and the indentation work. These connections were used to relate the conventional hardness number, Hv, and Young's modulus, E, with the work performed during loading and unloading. This work can be determined with great accuracy from the measurements.
Determining Plastic Properties of Material Through Instrumented Indentation Approach
INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN ENGINEERING & TECHNOLOGY, 2019
One significant advantage of indentation tests is that this test only requires a small amount of test material, this makes it very attractive for material characterization with gradient properties where standard specimens are not available such as in situ or in vivo. Regarding tests for spot welded joints, standardized testing does not apply to characterize HAZ and nuggets because of their complex structure and small size. This has opened the possibility to characterize material properties based on the Indentation method to characterize inverse parameters of constitutive material laws for nuggets, HAZ and base metals. The numerical approach based on the Finite Element (FE) model has been developed and validated. The established formulation is used for reverse (inverse) prediction of the nature of constitutive material (ie yield stress (σy), strain hardening coefficient (n)) for the welded joint zone namely the nugget, HAZ and parent metals (base). Then able to predict the effect of the nugget size and the thickness of the sheet metal on the strength of the spot welded joint with dissimilar material.
Mechanics of Materials, 2014
The application of the concept of the representative strain is often used in the stress-strain curve determination from indentation test because it can significantly simplify the analysis of the indentation response. A new methodology for determining the representative strain for Vickers indentation is presented in this article. Following a procedure based on finite element simulations of indentation of elastoplastic materials, two representative strains are defined: the representative strain characteristic of the mean pressure and the representative strain characteristic of the Martens hardness or the indentation loading curvature. The results obtained from this methodology show that there is no universal value of representative strain independent of the mechanical parameters of materials indented by Vickers indentation. It is also shown that the representative strain, obtained by Vickers indentation is much lower when it is obtained from the relationship between the applied force and the penetration depth, F-h, rather than from the relationship between the applied force and the contact radius, F-a. The values of the calculated representative strains show that simultaneous measurement of relationships F-a and F-h make it possible to characterize the hardening law with two unknown parameters by Vickers indentation.
Computational Materials Science, 2009
We proposed an application of inverse approach to experimental indentation data in order to determine combined hardening models parameters. It was shown that the use of a model combining isotropic and kinematic hardening allows a better description of cyclic indentation than isotropic hardening models. It was also shown that inverse analysis applied to experimental cyclic indentation curves can give a quite good approximation of the monotonic stress-strain curve and the beginning of cyclic tensile test. However, it appeared that the combined hardening model, used in this paper, is not sufficient to take into account all phenomenons coming in the steels behaviour under cyclic indentation.
Journal of Materials Science, 2013
In the present article, a new method for the determination of the hardening law using the load displacement curve, F-h, of a spherical indentation test is developed. This method is based on the study of the error between an experimental indentation curve and a number of finite elements simulation curves. For the smaller values of these errors, the error distribution shape is a valley, which is defined with an analytic equation. Except for the fact that the identified hardening law is a Hollomon type, no assumption was made for the proposed identification method. A new representative strain of the spherical indentation, called "average representative strain", ε aR was defined in the proposed article. In the bottom of the valley, all the stress-strain curves that intersect at a point of abscissa ε aR lead to very similar indentation curves. Thus, the average representative strain indicates the part of the hardening law that is the better identified from spherical indentation test. The results show that a unique material parameter set (yield stress σ y , strain hardening exponent n) is identified when using a single spherical indentation curve. However, for the experimental cases, the experimental imprecision and the material heterogeneity lead to different indentation curves, which makes the uniqueness of solution impossible. Therefore, the identified solution is not a single curve but a domain that is called "solution domain" in the yield stress-work hardening exponent diagram, and "confidence domain" in the stress-strain diagram. The confidence domain gives clear answers to the question of uniqueness of the solution and on the sensitivity of the indentation test to the identified hardening laws parameters.
Journal of Mechanical Engineering and Sciences, 2021
Instrumented indentation technique gives the possibility to determine the mechanical properties for small specimens and material in service. Several researchers have attempted to evaluate this approach experimentally and investigated the factors that affect it by using different indenter’s geometries for different engineering materials. In this work, the instrumented indentation technique was used to evaluate the mechanical properties experimentally and numerically using finite element simulation to understand the contact mechanics between the indenter surface and the substrate for two types of steel alloys namely ASTM516-G70 and AISI1010 steel. Two shapes of indenters, blunt (spherical) and sharp (Vickers) were used. The results were then compared with the experimental results extracted from the instrumented indentation test. The results have demonstrated a good agreement between the experimental and the finite element simulation results with error bound a ±5 % for young’s modulus ...
2019
A new technique that can determine the elastic-plastic properties of metallic materials using an instrumented indentation testing and iterative finite element (FE) simulations is proposed. This non-destructive technique can be applied to isotropic, additively manufactured, and/or surface treated metallic components of various scale. Currently, the measurement of material properties using the instrumented microor nanoindentation test is limited to the elastic modulus and surface hardness. A number of experimental and numerical approaches have been suggested for prediction of monotonic properties of metallic materials including yield strength, strain hardening parameters, ultimate strength, and fracture toughness. However, the past efforts to measure the stress-strain behavior using a single instrumented indentation test were not successful because there is no straightforward correlation between forcedisplacement relation and the elastic-plastic relation. In this study, both experimen...
Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, 2013
Conventional indentation tests do not provide an accurate estimation of viscoplastic material properties. In this work, a combined finite element analysis and optimization approach is developed for the determination of elastic–plastic and creep material properties using only a single indentation loading–unloading curve based on a two-layer viscoplasticity model. Utilizing the indentation loading–unloading curve obtained from a finite element-simulated experiment with a spherical and a conical indenter, a set of six key material properties (Young’s modulus, yield stress, work hardening exponent and three creep parameters) can be determined. Non-linear optimization algorithms are used with different sets of initial material properties, leading to good agreements with the numerically simulated target loading–unloading curves.
Materials Science and Engineering: A, 2014
The identification of plastic properties with spherical indentation has been the subject of many studies in last decades. In the present work, a new method for the determination of the hardening law of materials using the load-displacement curve of a spherical indentation test is proposed. This method is based on the use of an average representative strain. The advantage of the proposed average representative strain is that it is strictly obtained from the material response to the indentation test. By using various values of penetration depth, the proposed method gives the range of strain for which the hardening law is precisely identified and allows determining a confidence domain that takes into account experimental imprecision and material heterogeneity. The influence of penetration depth and the error formula on the identified Hollomon hardening law are discussed in the present study. The present study clarifies many problems that were observed in previous studies such as the uniqueness of solution and the sensitivity of the indentation test to the plastic parameters of the Hollomon hardening law.