ABSTRACT
The concept of TNT equivalence is often invoked to predict the blast parameters generated from explosions, in which high explosives other than Trinitrotoluene (TNT) are used. This paper discusses the TNT equivalence concept for bare charges using Pentaerythritol tetranitrate (PETN). At first, a review of different methods to derive TNT equivalence factors is given. After that, numerical simulations are conducted in order to obtain overpressure and impulse data, which is fitted by using the curve-fitting method. Meanwhile, the equations representing the fitted curves of peak overpressures and maximum impulses are employed to calculate the TNT equivalence factors for overpressure and impulse, respectively. Fitting these data, formulae are developed to calculate the TNT equivalence factors of PETN for overpressure and impulse. It is found that a single value, i.e. 1.258 for overpressure and 1.272 for impulse, can be used to convert the charge mass of PETN to TNT in the far field. This statement is confirmed by a series of free field air blast measurements. However, the TNT equivalence factors of PETN vary significantly in the near field. The value can be as large as 2.6 times the one in the far field.
ABSTRACT
Musculoskeletal simulations of lumbar spine loading rely on a geometrical representation of the anatomy. However, this data has an inherent inaccuracy. This study evaluates the influence of defined geometrical parameters on lumbar spine loading utilising five parametrised musculoskeletal lumbar spine models for four different postures. The influence of the dimensions of vertebral body, disc, posterior parts of the vertebrae as well as the curvature of the lumbar spine was studied. Additionally, simulations with combinations of selected parameters were conducted. Changes in L4/L5 resultant joint force were used as outcome variable. Variations of the vertebral body height, disc height, transverse process width and the curvature of the lumbar spine were the most influential. These parameters can be easily acquired from X-rays and should be used to morph a musculoskeletal lumbar spine model for subject-specific approaches with respect to bone geometry. Furthermore, the model was very sensitive to uncommon configurations and therefore, it is advised that stiffness properties of discs and ligaments should be individualised.
