An analysis of a tensile nanoindentation process for film/substrate systems

Here we present an in-depth analysis of a tensile nanoindentation process to measure Young's modulus and yield strength of nanofilms and materials under tensile loading. The proposed methodology utilizes a truncated conical indenter and an upwardly obtruded well-shaped tube structure from substrate. It has been numerically shown that the maximum indentation load and unloading slope are independent of contact area over a fairly large range of indenter stroke. The apparent correlation between load-displacement result and material properties in the tensile nanoindentation has been understood in terms of a modified thick-walled cylinder model, based upon the assumption of frictionless and uniform radial expansion of the film. When the model parameters were determined numerically, the modified cylinder model predicted Young's modulus and yield strength of nanofilms close to the results of the finite element analysis, indicating that the newly proposed nanoindentation process is not far away from the behavior of the modified thick-walled cylinder and that a necessity exists to refine the model parameters.