Measuring Mechanical Properties of Micro Wire Cross Sections Used
in Cardiovascular Devices

Ning Yu,

and

Andreas A. Polycarpou,

Department of Mechanical and Industrial Engineering

University of Illinois at Urbana-Champaign

Urbana, IL 61801, USA

Abstract

In this study, it is demonstrated that the nanoindentation technique can successfully measure the hardness and Young’s modulus of micro wire cross sections with diameters ranging from 100 to 200 micrometers. Using miniature optics and a specially developed positioning adapter, measurements have been successfully performed on the wire cross sections with an accuracy of 1-2 micrometers. Homogeneous wire cross sections, such as MP35N and composite layered wire such as MP35N with Ag core are studied. Based on AFM surface imaging and the characteristic nanoindentation load-displacement curves, different material regions on the wire cross sections can also be unambiguously identified. Based on the nanoindentation measurements, for each sample, the hardness and Young’s modulus at different positions and depths, i.e., a 3-dimensional hardness and Young’s modulus map are constructed. The data from the cross-section samples, especially the uniform material samples show that the hardness and Young’s modulus are higher in the center of the wires compared to the edges of the wires, possibly due to differences in residual stresses.