Testing Orthotropic Material Properties

1. Three-Dimensional Fracture Properties of the Florida Manatee Rib BoneJeff Leismer, MEnggMechanical & Aerospace Engineering Department, University of Florida, Gainesville, FL Material Properties E=Elastic Modulus u=Poisson’s Ratio G=Shear Modulus Resulting Strains Due to Applied Stresses Orthotropic Compliance Matrix Hooke’s Law crack tip Three-Dimensional Fracture Properties of the Florida Manatee Rib BoneJeff Leismer, MEnggMechanical & Aerospace Engineering Department, University of Florida, Gainesville, FL • Introduction • -25% of all manatees die as a result of collisions with watercraft • -Reducing boat speed in manatee zones can greatly reduce the energy of impact in the event of a collision • University of Florida researchers previously correlated the energy associated with traveling at various speeds in a small boat to the energy required to fracture manatee bone • One of the goals of my dissertation work is to build on this information to further reinforce speed restrictions in manatee zones so that this docile creature can remain in existence for future generations to admire Visual Image Correlation (VIC) -Two cameras take simultaneous pictures of a specimen as it is loaded -Correlation software maps the specimen surfaces from the images to digitized 3D space -Images of the loaded specimen are used to digitally measure deformations relative the reference photo of the undeformed specimen • Aims • Characterize manatee rib bone material properties • Determine anisotropic fracture properties • Predict the anisotropic stress intensity factors (KI,KII,KIII) using finite element methods and fracture analysis software Finite Element Analysis (FEA) -FEA is a computational tool that divides representative domains (e.g., structures) into subdomains, called finite elements -The finite element method provides a systematic method for approximating the domain’s response to outside perturbations -Here., FEA is used to calculate crack-tip opening displacements (CTODs) in pre-cracked specimens subjected to loading • Testing Orthotropic Material Properties • -Six experiments are run, each with the application of only a single component of stress • From the measured strain, we can calculate all of the orthotropic elastic constants (i.e., material properties) Specimens Measured Properties Tests Elastic Moduli & Poisson’s Ratios E1, E2, E3, u23, u13, u12 Tension Torsion Compact Tension Computational Fracture Analysis -CTODs from FEA are used to determine the 3D anisotropic stress intensity factors in a specimen -Numerical results are compared with those from experiment to determine the predictive capacity of the model for fracture analyses Shear Moduli G23, G13, G12 Conclusions -Comparison of experimental and FEA results can help identify the contribution of internal structural artifacts to fracture resistance -This analysis will provide insight into the way that manatee bone fractures and thus will assist in determining risk potential for bone fracture in the Florida manatee Stress Intensity Factors, Fracture Toughness 1) KI, KII, KIII, KIC 2) KI, KII, KIII, KIC 3) KI, KII, KIII, KIC 2006 University of Florida Graduate Student Council Forum