Experimental investigation of strain rate dependence of nanocrystalline Pt films

K. N. Jonnalagadda, Ioannis Chasiotis, S. Yagnamurthy, John Lambros, J. Pulskamp, R. Polcawich, M. Dubey

Research output: Contribution to journalArticlepeer-review

Abstract

A new microscale uniaxial tension experimental method was developed to investigate the strain rate dependent mechanical behavior of freestanding metallic thin films for MEMS. The method allows for highly repeatable mechanical testing of thin films for over eight orders of magnitude of strain rate. Its repeatability stems from the direct and full-field displacement measurements obtained from optical images with at least 25 nm displacement resolution. The method is demonstrated with micron-scale, 400-nm thick, freestanding nanocrystalline Pt specimens, with 25 nm grain size. The experiments were conducted in situ under an optical microscope, equipped with a digital high-speed camera, in the nominal strain rate range 10-6-10 1 s-1. Full field displacements were computed by digital image correlation using a random speckle pattern generated onto the freestanding specimens. The elastic modulus of Pt, E=182±8 GPa, derived from uniaxial stress vs. strain curves, was independent of strain rate, while its Poisson's ratio was v=0.41± 0.01. Although the nanocrystalline Pt films had the elastic properties of bulk Pt, their inelastic property values were much higher than bulk and were rate-sensitive over the range of loading rates. For example, the elastic limit increased by more than 110% with increasing strain rate, and was 2-5 times higher than bulk Pt reaching 1.37 GPa at 101 s -1.

Original languageEnglish (US)
Pages (from-to)25-35
Number of pages11
JournalProceedings of the Society for Experimental Mechanics, Inc.
Volume67
StatePublished - Dec 1 2010

Keywords

  • Digital image correlation
  • Mechanical properties
  • Nanocrystalline platinum
  • Strain rate
  • Thin films

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering

Fingerprint

Dive into the research topics of 'Experimental investigation of strain rate dependence of nanocrystalline Pt films'. Together they form a unique fingerprint.

Cite this