Session: Research Posters

Paper Number: 174253

Investigating the Time-Dependent Interaction Between Mil-Lx Compliant Element and Tibial Loading Under Vertical Impact 

Anti-Vehicular Landmines (AVLs) or under-belly Improvised Explosive Devices (IEDs) are found to be one of the major threats to military vehicles and induce injuries on their occupants. When an AVL or IED is detonated under or to the side of the vehicle, a shock wave with intensive energy is generated (Pandelani, 2014). Wang et al. (2001) noted that the average velocity and acceleration of a floor of a medium-sized armoured vehicle may exceed 12 m/s and 100 g’s (1 000 m/s2) during an AVL incident.

A number of lower limb surrogate legs are used to quantify the loading on the lower extremity when subjected to the impulsive loading caused by such an explosive event (Pandelani et al, 2010a, Pandelani et al, 2014, Mckay, 2010).  Previous studies have demonstrated the low biofidelity of the current standard Anthropomorphic Testing Device (ATD) leg ( Pandelani et al, 2010b, Quennville and Dunning, 2012, Newell et al, 2013), the Hybrid III (HIII) (Nies, 2005). Due to the poor performance of the HIII leg, The Test Device for Human Occupant Restraint (THOR-Lx) leg was developed (Bergeron, 2001, Barbir, 2005). Bir et al (2006) conducted impact tests on the THOR-Lx leg and reported that the leg provides more accurate correlation with cadaveric test data than the HIII at low impulsive loads. This study also revealed that there is a loss of biofidelity in both HIII and THOR-Lx at higher loading conditions. These findings suggest that neither of these surrogates can be used for the evaluation of AVL blast injuries. This led to the development of the military lower extremity (MiL-Lx) leg ( Mckay, 2010). It is more biofidelic for AV mine loading conditions, simple and robust.

Other studies have highlighted significant discrepancies between HIII and MiL-Lx leg in their responses under vertical loading conditions (Mckay, 2010, Pandelani et al, 2010a) . Chirvi et al. (2023) reported substantial differences in peak axial forces recorded by HIII and Mil-Lx under similar loading conditions, underscoring the importance of understanding distinct mechanical behaviors of these legs for accurate injury prediction and effective countermeasure assessment (Mckay, 2010). Similarly, Pandelani et al. (2016) demonstrated the efficacy of different combat boots (Meindl and Lowa) in attenuating peak forces at the lower tibia while noting a slight increase at the upper tibia, illustrating the complexity of boot-ATD interactions and their implications for injury risk.

During the development of this surrogate, MiL-Lx leg response was evaluated under impact loading and compared to cadaveric tibia axial force data for the selection of the new compliant element. The purpose of this study was to investigate the temporal relationship between the compression of the compliant element and characteristics of the tibia load cell time history data. A series of controlled vertical impact tests were conducted to investigate the force transmission characteristics of the upper and lower tibia load cells using the Modified Lower Limb Impactor (MLLI).

The results indicate that with increasing impact severity, the forces in both the upper and lower tibia rise significantly. Notably, the lower tibia load cell exhibits a distinct force plateau, which corresponds with the maximum compression of the tibia element. A double-peak pattern emerged at higher severities, with the first peak attributed to the initial shock and the second due to recoil following full compression of the tibia-compliant element. The time to peak in the lower tibia load cell reduced with increasing severity, whereas the upper tibia time to peak remained relatively stable.

Importantly, the tibia element was found to significantly influence the upper tibia response, highlighting the need for further investigation into the fidelity of these measurements compared to human physiology. The MIL-Lx leg demonstrated sufficient sensitivity to differentiate between a range of loading conditions, validating its utility as a measurement tool.

 

 

 

Presenting Author: Thanyani Abson pandelani University of South Africa

Presenting Author Biography: I am currently the Associate Professor in Mechanical Engineering Design, Biomechanics, Biomedical Engineering, Additive Manufacturing, School of Engineering, Department of Mechanical, Bioresources and Biomedical Engineering, University of South Africa.

My research interests are in the broad areas of human vulnerability with experience is modelling, simulation, analysis, testing and evaluation of landmines and Improvised Explosive Devices. My technical expertise are in computational mechanics, Biomechanics, Soft material mechanics, design of medical devices, mechanical vibration and quality management. I am the leading national authority on the use and application of Anthropomorphic Test Devices (ATD’s) for researching trauma biomechanics due to, and the evaluation of protection levels of vehicles against landmine and IEDs blast. This includes international research support in development of applicable injury criteria and the correct assessment thereof with ATD’s, participation in international research groups and organisations that developed international injury assessment methods.

Authors:

Thanyani Abson pandelani University of South Africa