Department of Mechanical Engineering 26th Annual James F. Bell Memorial Lecture in Continuum Mechanics

Description

Ellen M. Arruda, chair of the Mechanical Engineering Department and a professor of mechanical, biomedical, and macromolecular science and Engineering at the University of Michigan, will give the 26th Annual James F. Bell Memorial Lecture in Continuum Mechanics, entitled "Soft Material Characterization by Magnetic Resonance Phase Field Imaging," for the Department of Mechanical Engineering.

Please attend the event by using the Zoom link (Passcode 781551).

Abstract:

The characterization of the mechanical properties of soft materials, including elastomers and the soft tissues of knee and shoulder joints has been a major focus of my laboratory. Obtaining the mechanical properties of soft tissues is particularly challenging for a number of reasons, the first of which is that they are very soft, and direct gripping is fraught with problems. They are also anisotropic, therefore testing in multiple directions and deformation states is typically required. Our interest in developing full-knee computational models necessitates accurate constitutive models of the soft tissues of the knee. Finite element (FE) models of the knee can provide specific information on individual tissue contributions with respect to global joint function, as well as the coupling and coordination among tissues during macroscopic joint motions. Computational models offer precise, full-field, and complete descriptions of deformation manifesting from normal motions, injury causing activities, injured and diseased joints, and reconstructive procedures. FE models further have the potential to conduct clinically meaningful, individualized joint analyses.

In this talk I will show how geometric effects, heterogeneous deformation, and experimental uncertainty have manifested as subject-to-subject variability in the mechanical response of the anterior cruciate ligament (ACL). I will describe our use of fullfield methods to overcome these challenges and the tremendous opportunity they afford in characterization of the non-linear, anisotropic mechanical properties of soft tissues. Specifically, we have pioneered a new experimental method for finite strain characterization of soft materials using the phase field signal during in-situ mechanically deforming materials with magnetic resonance imaging. We have validated our approach using a well-characterized elastomer and recently applied the approach to the bundles of the ACL and the patellar tendon of the knee. We add to our approach to virtual fields method of characterization. Time permitting I will also describe our very recent efforts to also characterize materials without assuming a constitutive model a priori.