Mats G. Hartmann and Pernilla E. Magnusson
Vulnerability/lethality (V/L) tools used to assess weapons effects in targets often need some kind of rule to assess the status of each vital component being hit. The target functionality on a system level can then be decided, based on the components that are functional as opposed to non-functional (killed). Rules of this kind are often referred to as component kill criteria. Descriptions of criteria and methods of how to assess them are rare in scientific journals, probably due to economic values, classified V/L tools, as well as classified input data to the tools. This paper presents the results from an attempt to define the penetration kill criterion of a relay via simulations. The result is compared with previously published experimental results and the methodology is discussed. Despite some shortcomings in tools and methodology it is believed that simulations can, to a large extent, be a successful way to define kill criteria for components since experimental studies will rarely be feasible due to the cost.
Manmohan Dass Goel, Tanusree Chakraborty, and Vasant A. Matsagar
The present study focuses on the effectiveness of steel-sand composite stiffened plates under impulsive loading. Dynamic response of steel-sand composite stiffened plates, with various stiffener layouts under impulsive loading is analysed using commercially available finite element software Abaqus/Explicit. The steel plates and stiffeners are modelled using shell elements and the effect of strain rates is incorporated through Johnson-Cook (J-C) material model. Sand is modelled as a continuum between the two steel plates. Sand response is simulated using the built-in Drucker-Prager plasticity model in Abaqus considering the strain rate effect. The contact planes between sand and the steel plates are modelled using the general contact formulation in Abaqus. Impulsive load is applied in the form of a rectangular uniform pressure pulse. The effect of different thicknesses of the sand layer in response mitigation has been investigated. The steel-sand composite stiffened plates exhibit lesser central point displacement under impulsive loading as compared to when no stiffeners are provided.
Alexander J. Braden and Kevin M. Jaansalu
A design specification was written for a “non-lethal” artillery round, with the aim of mimicking the explosion characteristics of the M107 high-explosive round, while minimizing the lethal radius. An M107 round contains 6.95 kg of Composition B, with a 100% kill radius of roughly 20–30 m. The required explosive mass was reduced to 3.00 kg, to account for the fact that no explosive energy would be required to expand a steel shell and propel the resulting fragments. Since a lethal radius of 1–2 m exists due to blast overpressure, the round is referred to as a “reduced lethality artillery round” (REDLAR). Eight concepts for a REDLAR were developed, then screened and ranked on the basis of the design specification. Two concepts were selected and refined into detailed computer models: a base-ejecting charge round (BEC), and a 155 mm sabot round. Using the PRODAS© software package, simulations of the interior and exterior ballistic performance of each round were conducted. Results showed that the BEC was a close ballistic match to the M107, while the Sabot Round was gyroscopically unstable. The BEC round was also calculated to have a 50% probability of a lethality radius of 1 m or less.
Robert Bryce and Kevin Sprague
Aggregate violence data in Afghanistan from 1 January 2005 to 30 June 2011 is considered. The time series is characterized by correlated stochastic fluctuations around a smoothly growing and seasonally varying mean intensity level, as well as sudden and large spikes in intensity. These spiky outliers are directly correlated with election day violence and appear decoupled from the underlying dynamics. Key results are as follows: (1) approximate exponential growth ( = (144.7 ± 15.5) × 10–5 /day) in long-term conflict intensity, (2) election day violence exhibiting the same growth rate ( = (145.2 ± 7.6) × 10–5 /day) as the day-to-day conflict growth – these growth rates are comparable to that of coalition fatalities ( = (91.6 ± 0.3) × 10–5 /day), and (3) fluctuations displaying nominal power-law scaling ( = 0.63 ± 0.01) with the conflict intensity. Smoothing allows forecasting of the expected (mean) intensity while the observed power-law scaling enables usage of surrogate time series to forecast the stochastic fluctuations enveloping the mean. One crucial finding arising from the nominal exponential growth in election day violence is an expectation of a more than doubling in violence in the next election day over the 2010 elections.
Peter Dobias and James A. Wanliss
Previous research shows that security incidents in an asymmetric conflict (counter-insurgency, war on terror) exhibit power-law behaviour in terms of casualties and incidents. This study, covering a significantly larger data set than the previous works, confirms the general findings of these earlier analyses. However, it appears that the daily incident counts obey power law distributions only for values greater than the value expected from corresponding monthly average count. The low counts seem to be driven by a completely different mechanism. The present paper proposes that this behaviour is consistent with a dynamical model of insurgency based on a time-dependent Hamiltonian system with a slow free energy (for the insurgency corresponding to their supplies and morale) build-up, followed by a rapid, avalanche-like release. Then the asymmetry in the behaviour for low and high counts can be accounted for as follows. The high counts redistribute the free energy in the form of avalanches of violent incidents (akin to explosive instabilities in many physical systems). On the other hand, the low counts correspond to introducing artificial energy sinks in the system (for example, by localized disruptions to the enemy supply chain or weather-related obstacles). The findings and the model seem to be in line with the studies suggesting that self-organized criticalities form a universality class, opening the door for modeling and possible predictive analysis.
