Modeling and Simulation of the Active Jammer Effect in the Crossed Array Detectors Infrared Seeker
IR active jammers or the directed infrared counter measures(DIRCM)generate IR signals which attack the guidance signals passed to the sensors in IR-guided weapons. They provide IR signals with appropriate frequency, phase and intensity which will be superposed on those produced by the IR energy of the target passing through the reticle. When both the jamming signal and the modulated target energy signals are received by the missile‟s IR sensor, they cause the tracker to produce incorrect guidance commands and push the target out of the field of view (FOV). In this paper, the seeker signals of a crossed four slits or crossed array detectors (CAT) infrared seeker will be simulated. Then the active jammer signal is modeled and simulated. After that, the effect of all the active jammer parameters will be discussed and simulated. Finally, the conditions or the ranges of these parameters in which the active jammer can affect the seeking process will be stated.
Design and Simulation a New Unique-Slit Reticle for Pulsed Infrared Seekers
Spin reticle infrared seekers have good linearity, and the pulse-modulated reticle seekers have good digital characteristics for anti-jamming processing. A basic design for a spin pulse-modulated reticle is introduced. This design uses the rotating design of the optical system in the spin infrared seekers and an improved design of the reticle in the pulse-modulated seekers. The reticle contains a unique well-designed slit to produce one pulse for each target in the spinning period. The target data will be carried by the unique pulse parameters. A simulation tool is implemented using the MATLAB packages for analyzing and evaluating the new design.
Damage initiation and propagation in composite shells subjected to impact
Abstract The paper investigates the impact-induced damage initiation and propagation for laminated composite shells under low-velocity impact. A three-dimensional eight-node non-conforming element is described to analyze interlaminar stress distribution, and progressive failure. The damage analysis is performed by using Tsai–Wu quadratic failure criterion, Tsai’s damage modes and an additional delamination formula at all Gaussian points. The damage modes considered are matrix cracking, fiber breakage and delamination. The progressive failure is expressed by reducing stiffness of the material at all failed Gaussian points. Special attention is centered on curved laminates. Impact energy threshold for the onset of damage and transient damage size are predicted for composite shells. The analyses of the flat and curved laminates are compared for discussing their different damage mechanism. In addition, the influence of the stacking sequence, the thickness and the radius of curvature on damage behavior of composite shells are studied.