br Background An existing standard

Background An existing standard for description of system vulnerability analysis is the Vulnerability/Lethality (V/L) Taxonomy[2] represented in Fig. 1. Level 1 describes the initial state of thesystem before the attack. Level 2 describes the status of the components after the attack, with regard to the damage criteria. Level 3 describes the platform remaining capability at the functions level while level 4 describes the platform mission remaining effectiveness. Using a different terminology, the “platform incapacitation process” described in Ref. [3] refers to the same stages.
Combat utility prediction methodology In order to predict the impact of IED fragments on platform combat utility, we use a combination of two techniques (Fig. 3):
Validation For individual component vulnerability assessment, various simulation runs of this model with varying projectile-threat configurations have been conducted and analysed in Ref. [24]. Fig. 12 shows an example of such a configuration and results obtained (angular dispersion of BADs). A set of platform configurations has been tested for vulnerability in Ref. [24], with positive results. Fig. 13 is an example of results obtained when exposing a simple platform to IED fragments. Energy absorbed predictions match with the type of damage reported in after-action feedbacks [1] and other modelling methods [16].
Implementation and results
Conclusion and future work
Introduction 18% Ni maraging steels are extensively used in aerospace and defense applications because of their incomparable fracture toughness coupled with high tensile strength. The steels achieve superior mechanical properties through a simple low temperature AMG-900 hardening heat treatment and they are easily weldable as well [1]. Whereas one of the chromium-molybdenum steels, AISI 4130 steel, possesses moderate strength and reasonable ductility in hardened and tempered condition. This feature of AISI 4130 steel makes it highly suitable for various critical applications in air craft and automobile industries [2]. In many cases combination of steels in structures is necessary for technical and economical reasons. Therefore dissimilar joints are inevitable for connecting the components/systems made of different materials. Welding is a major route adopted for fabrication of such components. Though enough number of articles are noticed in open literature about fusion welding of either of these steels in their similar combinations, very few articles are published about dissimilar welding of these two ultra high strength steels. The high strength low alloys (like AISI 4130 steel) are found to be very sensitive to the heat affected zone softening behavior as compared to that of maraging steels [3,4]. So performance of weld joint majorly depends on circulatory system softer HAZ region (which is a weak link in the entire weldment) and thus controlling the extent of softening is highly essential in real time applications in order to realize better performing structures or pressure vessels. Nascimento and Voorwald [5] have studied the repair welding effects on the fatigue strength of aerospace structure made of AISI 4130 steel. They reported that during cyclic loading, the failure of AISI 4130 steel weld joint has occurred in the HAZ region due to the presence of tempered martensite that was formed during repair welding process. There exist several ways to control the HAZ softening behavior during welding of high strength low alloy steels. One way of controlling the degree of softening is by means of applying external cooling methods during and after welding process so that the excess welding heat input can be extracted effectively from the HAZ region. Yan et al. [6] have imposed faster cooling rates in HAZ region of high strength offshore steel by employing compressed air immediately after submerged arc welding process. They found that the fast cooling has improved the efficiency and low temperature impact toughness of the offshore steel weld joints by reducing the width of HAZ. Dong et al. [7] have reported that reducing the welding heat input during gas tungsten arc welding of HSLA steel has substantially increased the hardness and thus the strength of HAZ region by limiting the formation of martensite.