Uncertainty Quantification of a High-Throughput Profilometry-Based Indentation Plasticity Test of Al 7075 T6 Alloy (original) (raw)
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Advanced Engineering Materials
Herein, the effect of dispersed (relatively low levels of) porosity within a metal on its plastic deformation is examined. Stainless steel samples, made via additive manufacturing, are used in the work. It's found that porosity reduces stress levels during yielding and work hardening, approximately in proportion to the pore content. There is no significant difference between the strength of the effect during tension and compression, although porosity does reduce the tensile ductility. Finally, the profilometry‐based indentation plastometry (PIP) methodology (for obtaining stress–strain curves from indentation testing) are used. Porosity tends to bring the inferred yield stress down more strongly than during tensile testing and give higher initial rates of work hardening. This is associated with high local strains near the indenter causing closure of pores, so that volume is not conserved during the test. The resultant reduction in the pile‐up around the indent creates errors in ...
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.
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...
The method we introduced in 1992 for measuring hardness and elastic modulus by instrumented indentation techniques has widely been adopted and used in the characterization of small-scale mechanical behavior. Since its original development, the method has undergone numerous refinements and changes brought about by improvements to testing equipment and techniques as well as from advances in our understanding of the mechanics of elastic-plastic contact. Here, we review our current understanding of the mechanics governing elastic-plastic indentation as they pertain to load and depth-sensing indentation testing of monolithic materials and provide an update of how we now implement the method to make the most accurate mechanical property measurements. The limitations of the method are also discussed.
Acta Materialia, 2003
Indentation testing is a common method to assess the mechanical properties of materials near their surface. The elasto-plastic properties may be determined from the force penetration curves measured in indentation using inverse methods. In this spirit, Dao et al. [1] (Acta Materialia, 49, 2001) have established a forward and a reverse analysis for engineering metals using the equivalent conical indenter of the Berkovich and the Vickers pyramids, which has an included angle q of 70.3°. Extending Dao's approach, we studied, based on a finite element analysis on elasto-plastic materials, the influence of the included angle of conical indenters (q = 70.3, 60, 50 and 42.3°) and the friction coefficient on the force penetration curves. Based on this analysis, we suggest a more general method for determining the plastic properties of metals. The mechanical behaviour is modeled with the Young's modulus, E, the yield strength, s y , and the strain hardening exponent, n. We have shown that friction has a significant effect on the normal force measured on tips having included angles lower or equal to 50°. We have constructed, for each indenter geometry, a dimensionless function relating the characteristic parameters of the loading curve in indentation to the elasto-plastic parameters of metals. These functions have been generalized for any included angle. We show that the use of a second indenter with an included angle lower than q = 70.3°allows us to determine the strain hardening exponent with greater accuracy. Moreover, the sharper the indenter, the better the accuracy.
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 ...
Materials Science and Engineering: A, 2006
Algorithms for extracting mechanical properties from instrumented sharp indentation results (P-h curves) were recently developed on the basis of extensive finite element simulations coupled with the identification of a representative strain underneath the indenter and construction of characteristic dimensionless functions. The representative strain varies with the cone angle and a critical experimental verification of this concept was performed recently. In this paper, we ascertain the robustness of the algorithms, by subjecting the load versus depth of penetration curves (generated using finite element simulations on solids that were subjected to different levels of prior-plastic strains) to the reverse algorithms and comparing the extracted flow stress and the work-hardening exponent to the uniaxial data generated experimentally. A good match between the experiments and simulations validates the key assumptions made during the algorithm development.
Measurement, 2007
Indentation tests were performed on a large automotive component (a van gearbox) by means of a FIMEC apparatus. No surface treatment or component machining was performed before testing and small indentation marks were left on the part skin. The test results provide a yield strength distribution in the part geometry, according to the die casting procedure. Higher yield strength values are measured close to the metal injection gates. XRD analyses were also performed on samples extracted from the gearbox. The comparison between XRD data and FIMEC ones shows that the FIMEC test is useful to recognise differences in bulk material properties even if the skin properties are identical.
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.