A detailed lumbar spine FE component model (including vertebrae, inter-vertebral discs, all ligaments and facet joints of T12-L5) was built per the Global Human Body Model Consortium (GHBMC) CAD data. The lumbar model was correlated with the Post-Mortem Human Subject (PMHS) lumbar spine tests under flexion, compression and anterior shear loading modes in the physiological ranges (Belwadi, 2008), and was validated with the tests of PMHS functional spine units (FSU) of three adjunct vertebrae in fracture loading conditions (Belwadi, 2008). The lumbar model was integrated into the Takata in-house 50th percentile full human body model. The full body model was validated with the Wayne State University (WSU) PMHS vertical sled tests under +Gz loading in the range of 6G to 10G (Prasad, 1973). Good agreements were found between the test results and the FE model. At the lumbar component levels, stiffness and failure loads along with failure modes were correlated. At the full body level, the seat pan load cell forces, intravertebral body force, and the tissue level strains along superior-inferior direction at the anterior vertebral shells were correlated.
Using the validated human model, impactor tests were simulated for a mid-sized human male lying on a table in a vertically sitting posture impacted with a 44kg impactor of 300mmX300mm size onto the buttocks and thigh area at multiple impact speeds from 5.8 m/s to 15 m/s. The simulation results showed that the threshold impactor speeds (or energies) at which the human lumbar vertebrae fractures at the L1 level occurred were in the range of 8.92-10.6m/s (or 1750-2475J impact energy), varying with the fracture type and the test set up conditions.
Physical lab impactor tests in the same test setup configuration were run for the H3 50th%ile dummy at multiple impact speeds in the range of 5.8m/s-7.5m/s. The test data showed that the dummy lumbar