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VERSION:2.0
PRODID:icalendar-ruby
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
DTSTAMP:20260715T020339Z
UID:https://www.mpie.de/events/3596/2768772
DTSTART:20151214T130000Z
DTEND:20151214T140000Z
CLASS:PUBLIC
CREATED:20151120T134204Z
DESCRIPTION:The analysis of deformation and failure mechanisms in small-sca
 le devices and thin films is a critical issue\, not yet solved. In this pr
 esentation\, we describe recent advances and developments for the measurem
 ent of fracture toughness at small scales by the use of nanoindentation-ba
 sed methods including techniques based on micro-cantilever\, beam bending 
 and micro-pillar splitting. A critical comparison of the techniques is mad
 e 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 inde
 ntation 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 t
 he upper portion of the specimen. Nanoindentation splitting tests are perf
 ormed in-situ and the deformation mechanisms corresponding to each class o
 f materials have been investigated. Experimental results from a selected g
 roup of materials show good agreement between single cantilever and pillar
  splitting methods\, while a discrepancy of ~25% is found between the pill
 ar splitting technique and double-cantilever testing. The limitations of t
 he method are finally discussed. In particular\, a minimum pillar’s diam
 eter for the nucleation and growth of a crack during indentation is identi
 fied and quantified for a wide range of materials properties. It is conclu
 ded that both the micro-cantilever and pillar splitting techniques are val
 uable 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 be
 cause their higher toughness prevents splitting\, and in this case\, micro
 -cantilever bend testing is preferred.\nSpeaker: Dr. Marco Sebastiani
LAST-MODIFIED:20180214T113605Z
LOCATION:Max-Planck-Institut für Eisenforschung GmbH\, Room: Seminar Room 
 1
ORGANIZER;CN=Prof. Gerhard Dehm / Dr. Christoph Kirchlechner    :mailto:
SUMMARY:Measurement of fracture toughness by nanoindentation methods: recen
 t advances and future challenges
URL;VALUE=URI:https://www.mpie.de/events/3596/2768772
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