Dynamic compression and recovery of cancellous bone for microstructural investigation

¹ Departement de génie mécanique (DGM) ENS Cachan, 61 avenue du Président Wilson, 94235 Cachan Cedex, France
² Blast Impact and Survivability Research Unit (BISRU), Department of Mechanical Engineering, University of Cape Town, Private bag X3, Rondebosch 7701, South Africa
³ L.M.T. Cachan, 61 avenue du Président Wilson, 94235 Cachan Cedex, France

^a e-mail: marianne.prot@ens-cachan.fr
^b e-mail: trevor.cloete@uct.ac.za
^c e-mail: pattofat@lmt.ens-cachan.fr

Abstract

Knowledge of soft porous materials, such as cancellous bone, under dynamic loading requires accurate descriptions of high-rate mechanical responses. A novel modification of the standard Split Hopkinson Pressure Bar (SHPB) technique, that makes dynamic specimen recovery possible, is presented. Two impedance matched tubes, operating in tandem, are concentrically aligned with the incidence bar and placed in contact with a collar at the striker end. The collar transfers half of the incidence stress wave and most (>90%) of the reflected stress wave into the concentric tubes. In other words, the tubes act as sequential momentum traps and provide a single specimen loading event of predefined intensity and duration. This approach allows for routine testing without the need for initial “gap setting” , i.e. an accurate initial offset of the momentum trap with respect to the collar. Experimental results from a series of tests on cancellous bovine bone are presented. Furthermore, results from a microstructural investigation of the recovered specimens are presented and compared with quasi-statically loaded specimens.