Professor Marco Sebastiani, University of Rome

Measurement of fracture toughness by nanoindentation methods: recent advances and future challenges
When May 11, 2015
from 02:00 PM to 03:00 PM
Where LR8, IEB Building, Engineering Science
Contact Name
Contact Phone 01865-273925
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The analysis of deformation and failure mechanisms in small-scale devices and thin films is a critical issue, not yet solved.

In this presentation, we describe recent advances and developments for the measurement of fracture toughness at small scales by the use of nanoindentation-based methods including techniques based on micro-cantilever, beam bending and micro-pillar splitting. A critical comparison of the techniques is made by testing a selected group of bulk and thin film materials.

For pillar splitting, cohesive finite element simulations are used for analysis and development of a simple relationship between the critical load at failure, pillar radius, and fracture toughness for a given material. The minimum pillar diameter required for nucleation and growth of a crack during indentation is also estimated. An analysis of pillar splitting for a film on a dissimilar substrate material shows that the critical load for splitting is relatively insensitive to the substrate compliance for a large range of material properties.

Micro-pillars are then produced by Focused Ion Beam (FIB) ring milling, being the pillar diameter approximately equal to its length; this ensures full relaxation of pre-existing residual stress in the upper portion of the specimen. Nanoindentation splitting tests are performed in-situ and the deformation mechanisms corresponding to each class of materials have been investigated.

Experimental results from a selected group of materials show good agreement between single cantilever and pillar splitting methods, while a discrepancy of ~25% is found between the pillar splitting technique and double-cantilever testing.

The limitations of the method are finally discussed. In particular, a minimum pillar’s diameter for the nucleation and growth of a crack during indentation is identified and quantified for a wide range of materials properties. It is concluded that both the micro-cantilever and pillar splitting techniques are valuable methods for micro-scale assessment of fracture toughness of brittle ceramics, provided the underlying assumptions can be validated. Although the pillar splitting method has some advantages because of the simplicity of sample preparation and testing, it is not applicable to most metals because their higher toughness prevents splitting, and in this case, micro-cantilever bend testing is preferred.

Marco Sebastiani – Short biography

Dr. Marco Sebastiani received a PhD in mechanical and industrial engineering in 2008 from university of Rome “Roma TRE”, studying the architecture design and nano-mechanical behavior of thin coatings for advanced mechanical applications, with prof. Edoardo Bemporad.

He was then appointed as an assistant professor of Materials Science at the University of “Roma TRE”, working on the development of innovative methodologies for residual stress assessment in thin films and small-scale devices, by the use of Focused Ion Beam (FIB) and nanoindentation techniques.

He is lecturer of Materials Science and Engineering for Bioengineering at the University of “Roma TRE” and has been advisor or co-advisor of about ten master/bachelor degree theses.

During the last years, the achieved results turned out to be extremely successful making him today an expert in the research fields of thin films technology, residual stress analysis in nanostructured or amorphous materials and nano-mechanical characterization of small-scale structures and micro-devices.

 His research results in fact led to:

  • the award of a Faculty Position as assistant professor (RTD) at university of “Roma TRE”, which was renewed in 2014;
  • the role of Coordinator and Principal Investigator of the large collaborative project ISTRESS (FP7-NMP-2013-LARGE-7, Grant Agreement N. 604646, starting Jan 1st 2014);
  • the role of Associate Editor of the Elsevier Journal “Materials and Design”;
  • the award of a Fulbright Research Scholarship which was spent at the university of Tennessee-Knoxville (USA), March to August 2014;
  • the publication of 52 papers on high-impact international journals with an h-index of 12 and more than 420 citations (Scopus: author ID: 7005846216);
  • Two best paper Awards at international conferences (ICACC 2007 and ITSC 2009)
  • Invitations to be member of the organizing committees of International Conferences and Meetings (among them: ICMCTF 2013, ICMCTF 2014 and NANOMEASURE 2014);
  • Member of the Editorial Board of “Surface Engineering” (peer reviewed journal, IF 1.6);
  • Invitations as reviewer for International Journals (more than 30 reviews up to now);

 

MAJOR COLLABORATIONS

Only those proved by common publications and/or official partnerships in European projects:

Prof. William D. Nix (University of Stanford, Materials Science and Engineering, CA, USA); Prof. George M. Pharr (University of Tennessee and ORNL, TN, USA); Prof. Alexander M. Korsunsky (University of Oxford, UK); Dr. Warren Oliver (president, Nanomechanics inc, Oak Ridge, TN, USA); Prof. Chris Eberl (Fraunhofer Institute, IWM, and University of Freiburg, Germany); Prof. Alberto Diaspro (Italian Institute of Technology, IIT, NAPH / Nanobiophotonics); Prof. Y. T. Cheng (University of Kentucky, USA); Prof. Mathias Goeken (University Erlangen-Nuremberg, Germany); Prof. Erik Bitzek (University Erlangen-Nuremberg, Germany); Prof. Ralph Spolenak (ETH Zurich, Switzerland); Dr. Nigel Jennett and Dr Jerry Lord (National Physics Laboratory, NPL, UK); Prof. Karsten Durst (Technical University Darmstadt, Germany); Prof. Reinhard Pippan, Prof. Jozef Keckes and Prof. Rostislav Daniel (University of Leoben, Austria); Dr. Dietmar Vogel (Fraunhofer Institute, ENAS); Dr. Martin Gall (Fraunhofer institute, IKTS); Prof. Mariana H. Staia and Prof. Eli  Puchi-Cabrera (Central University of Venezuela);