Sabina Cherneva

Finite Element Simulation of Nanoindentation Process

Recently, nanoindentation technique is gaining importance in determination of the mechanical parameters of thin films and coatings. Most commonly, the instrumented indentation data are used to obtain two material characteristics of bulk materials: indentation modulus and indentation hardness. In this paper the authors discuss the possibility by means of numerical simulations of nanoindentation tests to obtained the force-displacement curve employing various constitutive models for both the substrate and the coating. Examples are given to demonstrate the influence of some features of the numerical model and the model assumptions on the quality of the simulation results. The main steps in creation of the numerical model and performing the numerical simulation of nanoindentation testing process are systematically studied and explained and the conclusions are drawn.

In Vitro Complex Shear Modulus of Bovine Muscle Tissue

In living tissue, there exists a reciprocal relationship between mechanical properties and function. That is, properties affect function, and function can affect properties by means of adaptation. Thus, knowledge of mechanical properties leads directly to knowledge of function. Dynamic instrumented indentation provides a way to measure the mechanical properties of soft biological tissue that is relevant, localized, and accurate.

Investigation of the influence of the concentrations of Sn in electrochemically deposited CuSn alloy films on their mechanical properties

Mechanical properties of thin CuSn alloy films containing different content of Sn (0.06 – 67.5 wt.%) were investigated by means of nanoindentation experiments, using Nanoindenter G200 (Agilent Technologies), equipped with Berkovich indenter tip. The films were electrochemically deposited on screen-intermediate Ni film with thickness about 3 µm electrodeposited on Cu or brass (Cu66Zn34) substrates with thickness respectively 300 µm and 500 µm. The thicknesses of investigated CuSn films varied from 0.138 to 5.47 µm. Mechanical properties of the Cu and brass substrates were investigated too. As a result of nanoindentation experiments, load–displacement curves were obtained and two mechanical characteristics of the substrate and investigated films – indentation hardness (HIT) and indentation modulus (EIT) – were calculated using Oliver & Pharr approximation method. Dependence of indentation modulus and indentation hardness on the depth of indentation, content of Sn, structure and phase composition of the allo...

Experimental-Numerical Approach for Characterization of Mechanical Properties of Thin Electrochemically Deposited Chromium and Copper Films

A hybrid experimental-numerical approach, which combines microindentation experiments (where we measure the diagonal of the residual imprint after unloading) and numerical simulations by means of the finite-element method has been developed. The investigated materials in the present work are electrochemically deposited on brass substrates chromium and copper films with known thickness and unknown mechanical properties. Mechanical properties of the brass (CuZn36) substrate are known. Vickers’ microindentation experiments were carried out on the films and as a result the experimental load-displacement curves were obtained. After that the process of microindentation was modelled numerically by means of the finite-element method. Numerically obtained load-displacement curves were compared with the experimental curves. The results show good coincidence between numerical and experimental curves. Additionally it was realized nanoindentation experiment of thin copper film and these two methods (nanoindentation experiment and hybrid experimental-numerical method which combines experiment of microindentation and numerical simulations) for determination of mechanival properties of thin copper films were compared. Results obtained by means of the afore-mentioned two methods almost coincide but the second method is cheaper and gives more information about material properties of the film than the first method. It is shown that the second method is preferable to determine the mechanical properties of thin metal films.