BITS Faculty Publications
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Item A computational framework for modelling impact induced damage in ceramic and ceramic-metal composite structures(Elsevier, 2017-03) Islam, Md Rushdie IbneWhen ceramic or ceramic-metal composite structures are subjected to impact loading, they undergo various deformation phases such as plastic yielding, pulverization, fragmentation, tensile spalling, interface debonding, penetration etc. In order to study these phenomenological characteristics and produce insightful observation, numerical simulation is inevitable. Apart from reasonably accurate constitutive model, a numerical scheme must also accommodate any possible loss (in the case of fragmentation and material separation) of the continuum nature of the problem domain. This is generally difficult to achieve through mesh-based methods. In this study a computational framework based on smoothed particle hydrodynamics (SPH), a particle-based method, is explored and revamped. Damage growth and localized cracks are modelled through a pseudo-spring analogy, wherein particle-interactions are modulated based on material strength reduction after damage initiation. Different material models are coupled in this analogy for investigating different paradigms of penetration mechanics in ceramic and ceramic-metal composites. The computational framework is first validated through experimentally obtained results of flyer plate tests on Silicon Carbide (SiC) disc. Subsequently the framework is explored in simulating more complex failure mechanisms involving multiaxial crack interaction and fragmentation in ceramic-metal composite target system.Item Numerical modelling of crack initiation, propagation and branching under dynamic loading(Elsevier, 2020-02) Islam, Md Rushdie IbneIn this paper crack initiation, propagation and branching phenomena are simulated using the Pseudo-Spring Smoothed Particle Hydrodynamics (SPH) in two and three-dimensional domains. The pseudo-spring analogy is used to model material damage. Here, the interaction of particles is limited to its initial immediate neighbours. The particles are connected via springs. These springs do not provide any extra stiffness in the system but only define the level of interaction between the connecting pairs. It is assumed that a crack has passed through a spring connecting a particle pair if the damage indicator of that spring becomes more than a predefined value. The crack branching of a pre-notched plate under dynamic loading and the effect of loading amplitude are studied. The computed crack speeds, crack paths and surfaces are compared with experimental and numerical results available in the literature and are found to be in good agreement. Next, the effect of notch location for a plate with a circular hole is studied. The ability of the framework to model arbitrary crack paths and surfaces are also demonstrated via three-dimensional simulations of chalk under torsion, Kalthoff-Winkler experiment, Taylor bullet impact and crack branching.Item Pseudo-spring SPH simulations on the perforation of metal targets with different damage models(Elsevier, 2020-02) Islam, Md Rushdie IbneThe behaviour of circular plates made of Weldox 460E steel under projectile impact are numerically investigated by the pseudo-spring Smoothed Particle Hydrodynamics (SPH) framework. The Johnson-Cook material model is used to consider the plastic deformation of materials. Six damage models (Wilkins, maximum shear stress, constant fracture strain, Cockcroft–Latham, Johnson–Cook and Bao–Wierzbicki fracture models) are implemented to study the plate failure. The crack is modelled through the pseudo-spring analogy in which each interacting particle pair is connected through springs. These springs define the level of interaction based on the accumulated damage. The interaction between particle pair is terminated when the accumulated damage in the connecting spring reaches a critical value. Pseudo-spring SPH is efficient to capture any arbitrary crack propagation without any special treatment. The failure behaviour of the target plates and the residual velocities of the projectile are compared with the experimental results available in the literature. The effects of the fracture models on the numerical prediction are investigated. The implications of the projectile geometry are discussed briefly. The failure of a 12 mm thick target made of 2024-T351 aluminium alloy is also simulated with different damage models by the pseudo-spring SPH.