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Mechanics of Cortical Bone at Multi-length Scale

Wednesday, October 11, 2017

4:00 PM-5:30 PM

BIOMED Seminar

Mechanics of Cortical Bone at Multi-length Scale

Ahmad Raeisi Najafi, PhD
Assistant Professor
Department of Mechanical Engineering and Mechanics (MEM)
College of Engineering
Drexel University

Bone tissue has an intricate arrangement of material structures at multiple length scales, which work in harmony to perform a variety of mechanical, biological and chemical functions. The hierarchical structure of bone, spanning from the nanoscale, sub-microscale, microscale, mesoscale to the macroscale, significantly contributes to high stiffness, strength, toughness, and energy absorption, light weight, and other remarkable mechanical properties of bone.

In this seminar, we present our results on the multiscale characterization and modeling of bone, which provide structure-composition-properties relations. To characterize the bone structure and composition, we use microcomputed tomography, transmission electron microscopy, and ash and water contents, whereas we implement nanoindentation, microindentation (reference point indentation), and other traditional mechanical tests, such as fracture test to measure mechanical properties of bone.

The outcomes of our experimental studies are used as inputs for our numerical and analytical models, as well as the validation of modeling results. Our finite element and analytical model investigates the cortical bone fracture at the microscale level. The results indicate that cortical bone microcrack propagation is greatly influenced by osteonal density and bone microstructural heterogeneity, suggesting bone resistance to fracture can be predicted, at least in part, by quantification of osteonal density and bone material mismatch. Modelling of bone, accounting for different scales in conjunction with experimental works, provides new and needed insights into the fracture and strength of bone, which, in turn, can lead to improved diagnostic tools and drugs for the treatment of bone diseases, such as osteoporosis.

Ahmad Raeisi Najafi, PhD, is an Assistant Professor in the Department of Mechanical Engineering and Mechanics and is the director of the Multiscale Computational Mechanics and Biomechanics LAB (MCMBLAB). He received a BS degree in Mechanical Engineering (Solid Mechanics) from Shiraz University, Iran, in 1997, then an MS and his first PhD degree in Biomedical Engineering (Biomechanics), both from the Amirkabir University of Technology in 1999 and 2006, respectively. In 2012, Dr. Najafi joined Department of Mechanical Science and Engineering at the University of Illinois at Urbana-Champaign (UIUC) for his second PhD degree, working on the design of advanced materials, and received his degree in 2016.

Dr. Najafi was a Postdoctoral Research Associate at the NIH Center for Macromolecular Modeling & Bioinformatics in the Beckman Institute for Advanced Science and Technology at University of Illinois at Urbana–Champaign (UIUC) from 2016 to 2017, working on computational modeling of membrane protein structures.

Dr. Najafi's research interests are in Multiscale Computational Mechanics/Biomechanics/Biology, Design Optimization, Design of Biomimetic Materials, Mechanics of Biological Composites and Biomaterials, and Bone Fracture. He is a member of ASME and the Biophysical Society.

Contact Information

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