Hayden Petterson posted an update 6 months, 1 week ago
Improved Cell Cycle Compound Library of generalized weighting factor functionsPieces of work made by V. Cech form the core of the theory [33,34].ConclusionThis article presents our newly-conceived theory of generalized meteo-ballistic weighting factor functions – WFF as a special kind of sensitivity functions – Fig. 10. The limited extent of this contribution has allowed us only to indicate the applicational possibilities of the new theory.In the publications that will follow we plan to especially apply the new theory to the problematics of calculating the reference height of the projectile trajectory YR[2,3,18,28,31,33,34] that will mainly demand a detailed analysis of WFFs for the virtual temperature [20,32].AcknowledgmentsThis work originated with the support of financing from the Research Project for the Development of the Department of Weapons and Ammunition, Faculty of Military Technology, University of Defence, Brno, DZRO K – 201.IntroductionThe tuneable effects warhead concept is based on QinetiQ patented  technology, previously explored using bare explosive charges . This work showed significant differences in peak blast pressures between two detonation modes (35%) while maintaining quasi-static pressure. The study reported here looked at developing a metal cased variant with the aim to demonstrate a tuneable fragmentation output, whilst maintaining the demonstrated blast performance.Tuneable warhead conceptThe concept consists of an energetic fill constructed from three principal components arranged in co-axial layers (Fig. 1), namely:Two modes are available:Case designThe diameter and length of the charge were kept at the dimensions of the previous uncased study , the compositions of the energetic layers were also kept nominally the same.Split-X and hydrocode modellingThe design study applied Split-X to calculate the required steel case thickness to perforate a 5 mm steel plate in the high mode. Split-X  is an analytical code for the assessment of fragmenting warheads. Given the functionality of Split-X, the explosive, detonating in the mode, was modelled as a single cylinder with an inert surround. Given the available explosive mass, the assessment indicated that a case thickness of 10 mm with defined fragment sizes (approximately 10 mm cubes) was required to perforate the plate. The case steel selected was EN24 condition W. It was chosen based on the expected strength and ductility properties preferred for the case.The typical arrangement for the GRIM hydrocode simulations is shown in Fig. 2. The central core of PBXN110 was 35 mm in diameter, the annulus of HTPB-Al was 15 mm thick and the next annulus of PBXN109 was 15 mm thick. This gave a total explosive diameter of 95 mm. The length was 200 mm. For constitutive models to describe metals, the physically-based constitutive model due to Armstrong and Zerilli and modified by Goldthorpe et al. , Equation 1, is the preferred model used by QinetiQ. The Body Centred Cubic (BCC) form of the equation, relevant to the metals (Steel) in this study, is shown.In this equation Y is the flow stress, T is the temperature, έ is the strain rate, and εP is the plastic strain, with C1 through C5, n and a1 and a2, which describe the temperature dependence of the shear modulus, constants derived from the characterisation tests.As part of the drive to develop a system of physically based material models, Goldthorpe developed a path dependent ductile failure model . The QinetiQ algorithm used in the code is Equation 2In this equation S is the measure of ductile deformation/damage, is the stress state (pressure/stress) and is the shear strain with derived from characterisation tests. The material fails when S reaches SF, which was also derived from characterisation tests.The parameters for the EN24 W condition steel are listed in Table 1.The polymer composite materials, aluminised HTPB and PBXN109, were both represented with tabular equations of state, and for PBXN109 the QinetiQ Porter-Gould constitutive model . Table 2 lists the parameters, and the initial moduli are provided for the dynamic regime of interest (i.e. in an unrelaxed condition).