TODAY: ** SPECIAL LOCATION ** Berg, 27-Feb-24, 12:20pm Central
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Ellad Tadmor
Feb 27, 2024, 9:51:14 AMFeb 27
to aem-solid...@umn.edu
AEM Mechanics Research Seminar
** NOTE: Due to technical difficulties in our regular venue, today's Seminar will take place in Room 321 of the Mechanical Engineering building (ME 321) **
Tuesday 27-Feb-2024, 12:20pm Central
Dr. Brian T. Berg
In-person: Room 321, Mechanical Engineering, University of Minnesota
Online: Webinar registration link
R&D Corporate Distinguished Fellow, Boston Scientific, Maple Grove, MN
Title: Metallography & Fractography in Designing and Assessing Nitinol Cardiovascular Device Fatigue Durability
Abstract: Nitinol is widely used in medical devices including life sustaining permanent implants such as replacement heart valves. The mostly reversible stress-induced phase transition allows near complete recovery from small diameter delivery systems to functional devices with much larger diameters. However, like most any solid, Nitinol is subject to fatigue due to cyclic loads. In this lecture, I show many factors governing Nitinol fatigue by examining the physical and mechanical history of the material from the melt to the in vivo use. Combining this examination with a battery of tests - including testing the Nitinol to failure out to 1 billion cycles and examining the metallography and fractography [1] – analysis shows there are two failure modes – low-cycle fatigue due to phase transitions interacting with inclusions from the melt and ultra-high cycle fatigue due to sub-Kth crack progression from inclusions from the melt. Recent experiments are showing that 100 Million and 1 Billion fatigue life with cyclic phase transformation is possible when inclusions are <2 microns.
For more information, visit the AEM Mechanics Research Seminar website:
Title: Metallography & Fractography in Designing and Assessing Nitinol Cardiovascular Device Fatigue Durability
Abstract: Nitinol is widely used in medical devices including life sustaining permanent implants such as replacement heart valves. The mostly reversible stress-induced phase transition allows near complete recovery from small diameter delivery systems to functional devices with much larger diameters. However, like most any solid, Nitinol is subject to fatigue due to cyclic loads. In this lecture, I show many factors governing Nitinol fatigue by examining the physical and mechanical history of the material from the melt to the in vivo use. Combining this examination with a battery of tests - including testing the Nitinol to failure out to 1 billion cycles and examining the metallography and fractography [1] – analysis shows there are two failure modes – low-cycle fatigue due to phase transitions interacting with inclusions from the melt and ultra-high cycle fatigue due to sub-Kth crack progression from inclusions from the melt. Recent experiments are showing that 100 Million and 1 Billion fatigue life with cyclic phase transformation is possible when inclusions are <2 microns.
For more information, visit the AEM Mechanics Research Seminar website:
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Ellad B. Tadmor, Ph.D.
Russell J. Penrose Professor
Department of Aerospace Engineering and Mechanics
University of Minnesota
https://dept.aem.umn.edu/~tadmor/
Russell J. Penrose Professor
Department of Aerospace Engineering and Mechanics
University of Minnesota
https://dept.aem.umn.edu/~tadmor/
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