Orientation Dependent Compressive Response of Human Femoral Cortical Bone as a Function of Strain Rate

Abstract

Under extreme environments, such as a blast or impact event, the human body is subjected to high-rate loading, which can result in damage such as torn tissues and broken bones. The ability to numerically simulate these events would help improve the design of protective gear by iterating different configurations of protective equipment to reduce injuries. Computer codes capable of simulating these events require accurate rate-dependent material models representing the material deformation and failure (or injury) to properly predict the response of human body during simulation. Therefore, the high-rate material response must be measured to allow for simulation of high-rate events. This study seeks to quantify the highrate mechanical response of human femoral cortical bone for use in high fidelity human anatomical models. Cortical bone compression specimens were extracted from the longitudinal and transverse directions relative to the long axis of the femur from three male donors, ages 36, 43, and 50. The compressive behavior of the cortical bone was studied at quasi-static (0.001/s), intermediate (1/s), and dynamic (*1000/s) strain rates using a split-Hopkinson pressure bar to determine the strain rate dependency and anisotropic effect on the strength of bone. The results indicate that cortical bone is anisotropic and stronger in the longitudinal direction compared to the transverse direction.The human cortical bone compressive response was also rate dependent in both directions, demonstrating significant increase in strength with increase in strain rate. Additionally, as the strain rate increased from intermediate to dynamic, a decrease in the elongation at transverse orientation was observed, which would indicate the bone becomes more brittle.

Ultrasonic bone cutting: Experimental investigation and statistical analyses of cutting forces

“…It should be noted that the hard exterior section and the porous internal part of the bone are named cortical (or compact) and cancellous (or trabecular), respectively, as specified by Ralston [35]. Due to the cortical bone's anisotropic nature, it has different mechanical properties in different directions [36][37][38][39]. Generally, according to [40][41][42], three directions could be defined for the cortical bone: longitudinal or parallel, radial or across, and transverse.…”

Bone and Bone Surrogate Fragmentation Under Dynamic Compression

“…Extensive studies on cortical bone have been performed to help characterize the behavior of this naturally hierarchical structure [16][17][18][19][20]. Uniaxial compression testing of cortical bone is typically performed at strain-rates of 10 -3 s -1 to 10 3 s -1 which represents physiological loading rates of mammals walking or lightly exercising to high impact events such as falls or automobile accidents.…”

“…Conventional uniaxial dynamic compression tests performed with a Kolsky (split-Hopkinson) bar have also been used to characterize cortical bone and to investigate the strain-rate sensitivity behavior [18][19][20]. A more recent study by Sanborn et al [18] on human femoral bone yielded similar compressive strengths, with longitudinal strength of 152 ± 22 MPa at a strain-rate of 10 -3 s -1…”

“…When loaded in the transverse orientation, the strengths decreased to 87 ± 22 MPa at 10 -3 s -1 and 179 ± 26 MPa at 10 3 s -1 [18]. Compression testing at strain-rates of 10 3 s -1 were carried out by Adharapurapu et al [19] on both wet and dried bovine femoral cortical bone.…”

The Image-Based Inertial Release (IBIR) Test: A New High Strain Rate Test for Stiffness Strain-Rate Sensitivity Identification

“…Recently, the coupling of ultra-high speed imaging (> 1Mfps) and full-field measurements has opened up new avenues for developing high strain rate testing techniques. This effort has mainly focused on applying full-field measurements to complement the analysis of existing methods such as the SHPB [2][3][4][5]. However, the use of fullfield measurements combined with inverse identification techniques, such as the virtual fields method, provides an opportunity to create whole new test methods that do not required external load measurement [6][7][8].…”