Metals Identification from Instrumented Spherical Indentation Testing

Abstract

A new integrated system consisting of a testing machine, denominated Diaptometro, and of an algorithm for metallic materials identification via instrumented spherical indentation testing is presented. The identification is carried out by analyzing the experimental load – penetration depth curve ( curve) from shallow indentation tests, thus preventing any contact condition effects in the material properties estimation. Accuracy in the experimental data collecting and the curve representation were recognized to be the key factors at the basis of reliable and accurate estimations. A new equipment with accuracies of 0.075% and 0.1% for the penetration depth and indentation load respectively was specifically built-up, whereas a four-terms power expansion is proposed for modeling the curve in the identification procedure. Experimental validation campaigns confirm the effectiveness of the adopted solutions.

Modelling and simulation of the hardness profile and its effect on the stress‐strain behaviour of punched electrical steel sheets

“…Considering the direct approach, the material properties are directly determined from experimental indentation tests, which has the advantage of taking into account the actual experimental setup and boundary conditions [13]. In this context, Tabor introduced the concept of indentation stress-strain curves in a pioneering work by defining a representative strain and stress [4][5][6][13][14][15][16]. Based on the findings of Meyer, who identified the relation between indentation load and the contact radius of a spherical indenter, Tabor established a physical description of the material deformation during the indentation process [4,17].…”

“…The conversion of the loaddisplacement curve into the corresponding stress-strain curve can be performed by using either a direct or an indirect approach [6]. The latter refers to mathematical and numerical methods, in which finite-element models of the indentation test are verified by corresponding experimental data to identify a relation between indentation process and material properties [13,16]. Reliable estimations, however, are difficult to achieve, since the realistic modelling of friction between the contact surfaces of indenter and specimen is difficult, which influences the strain evolution in the indentation region.…”