Browsing by Author "Islam, Md Rushdie Ibne"

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Ballistic performance of ceramic and ceramic-metal composite plates with JH1, JH2 and JHB material models
(Elsevier, 2020-03) Islam, Md Rushdie Ibne
The ceramic and ceramic-metal composite plates upon high velocity impact by a kinetic energy rod may undergo spalling, fragmentation, interface debonding, perforation, bending, and stretching. A challenge in studying these problems is using a material model that realistically simulates the material response at high plastic strains, plastic strain rates and hydrostatic pressures. The choice of the material model and the computational framework influence predictions of deformations of the projectile-target system. Three constitutive relations generally employed to study deformations of a ceramic are due to Johnson and Holmquist, generally abbreviated as JH1, JH2 and JHB. We have implemented these in a computational algorithm using Smoothed Particle Hydrodynamics (SPH) basis functions and a pseudo-spring technique to simulate the initiation and propagation of material failure. After ensuring that the computed results for two flyer plate impact experiments agree well with the test findings, we have studied penetration of monolithic ceramic and ceramic/aluminium targets by kinetic energy rods having blunt, hemispherical and conical nose shapes. It is shown that the present approach can successfully predict spalling, formation of conoid, fragmentation and crack branching in the ceramic, and bending/stretching of metal backing plates. Whereas results from the JH1 and the JHB material models are qualitatively similar, those using the JHB constitutive relation are closest to the test observations. This work suggests that one should use the JHB model for analyzing impact and penetration of a ceramic plate.
A comparison of numerical stability for ESPH and TLSPH for dynamic brittle fracture
(Elsevier, 2023-10) Islam, Md Rushdie Ibne
Dynamic brittle fracture is a numerically challenging problem that involves crack nucleation, formation, propagation, and material fragmentation. In this work, we use two forms of Smoothed Particle Hydrodynamics (SPH), namely Eulerian SPH (ESPH) and Total Lagrangian SPH (TLSPH) augmented with the pseudo-spring or virtual-link analogy for seamless modelling of crack formation, subsequent propagation, and material fragmentation. Being particle-based in nature, SPH is naturally capable of capturing finite deformation in materials, and the pseudo-spring or virtual-link analogies provide modelling of multiple discrete cracks without any additional condition, such as visibility criteria. We simulate the crack branching and propagation in a brittle polymeric material subjected to biaxial tensile loading with a pre-existing central notch. The numerical results using ESPH and TLSPH agree with the previously published experimental and numerical results. We have also simulated the dynamic fragmentation of a cylinder and compared the results. This work shows the capability of both ESPH and TLSPH frameworks to model dynamic brittle fracture especially crack branching and curving. It is also observed that the ESPH and TLSPH frameworks present similar results for minor material deformation problems. However, the ESPH framework shows better stability and capability for finite material deformation problems.
A computational framework for modelling impact induced damage in ceramic and ceramic-metal composite structures
(Elsevier, 2017-03) Islam, Md Rushdie Ibne
When 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.
A computational model for failure of ductile material under impact
(Elsevier, 2017-10) Islam, Md Rushdie Ibne
In addition to an accurate mathematical representation of the material, a computational modelling method for assessing impact problems involving large plastic deformation, damage localization, fracture etc. requires a suitable discretization scheme which can simulate the relevant physical processes without introducing any numerical artifact or being unstable. In this paper, a computational framework based on Smoothed Particle Hydrodynamics (SPH) is presented for studying the deformation and failure of ductile material, steel plate, under impact loading. This provides a useful design tool to simulate penetration of the plate. Crack propagation is modelled through a pseudo spring analogy wherein the interacting particles are assumed to be connected through pseudo-springs and the interaction is continuously modified through an order-parameter based on the accumulated damage in the spring. At the onset of crack formation i.e., when the accumulated damage reaches the critical value, the spring breaks which results in termination of interaction between particles on either sides of the spring. A key feature of the computational model is that it can capture arbitrary propagating cracks without introducing any special treatment such as discontinuous enrichment, particle-splitting etc. This computational framework is used herein to study adiabatic shear plugging in metal plates when modelling penetration under impact loading by a flat-ended, cylindrical projectile. The effects of different damage criteria are discussed. Computed results are compared with the experimental observation given in the literature and the efficacy of the framework is demonstrated.
Extending incompressible SPH framework for simulation of axisymmetric free-surface flows
(Elsevier, 2017-11) Islam, Md Rushdie Ibne
Dynamics of a Newtonian fluid in a cylindrical symmetric domain can be conceptualized as axisymmetric flow. Full-scale 3D simulation of such problems requires large computational overhead. A new divergence-free Axisymmetric Incompressible Smoothed Particle Hydrodynamics (AxISPH) framework is proposed for modeling of Newtonian fluid flow with free-surface. The formulation employs the concept of variable axisymmetric volume based on current particle position to incorporate symmetry around the central axis. The framework utilizes a semi-implicit two-step approach to obtain hydrodynamic variables and minimizes errors in particle position. Laplace and gradient operators are modified to incorporate axisymmetric nature. A radial dam-break flow has been simulated with the proposed model and compared with three-dimensional ISPH result.
High precise benchmarks by CSD (computational solid dynamics) with meshfree methods
(SAE International, 2019) Islam, Md Rushdie Ibne
The virtual optimisation of tooling equipment is nowadays one of the common challenges in mechanical serial production. Even some numerical Eulerian approaches (grid-based) exist for modelling solid materials under dynamic loading, most of them are not very successful. Especially the solids undergoing large deformation and the subsequent material separation and propagating cracks demonstrate the limitations: variables become discontinuous across the crack surface, and the computational domain loses its continuum nature. Grid-based methods are not naturally equipped to deal with such situations due to the mesh distortion, mesh entanglement and requirement of mesh refinement. Very promising alternatives to the Eulerian methods are meshfree Lagrangian methods. Among them, smoothed particle hydrodynamics (SPH) is entirely meshfree and naturally equipped to handle large material deformation. In SPH the computational domain is discretised by a set of particles. A given particle interacts only with its neighbouring particles through a kernel function whose support is defined by the smoothing length. The Bell-shape of the kernel function ensures that the interaction is at a maximum between immediate neighbours and gradually decreases with an increase in distance between interacting particles. During the deformation process, previously interacting particles may leave each other's influence domains and cease to interact further which makes SPH natural in handling large material deformation. Based on the SPH, a solver with multi-GPU acceleration for modelling solid materials has been developed, and is proven to be effective in several practical applications involving large deformation and material failure. In the present work, we discuss the current needs for virtual tool optimisation, the limitations of existing simulation software and the potential advantages and disadvantages of Lagrangian particle-based approaches especially SPH.
Implementation of three-dimensional physical reflective boundary conditions in mesh-free particle methods for continuum fluid dynamics: Validation tests and case studies
(AIP, 2019-10) Islam, Md Rushdie Ibne
Mesh-free particle methods applied to continuum fluid dynamics still use fictitious, ghost or virtual particles, and/or molecular dynamics concepts in the treatment of the boundaries. The aim of this paper is to present the implementation of the physical reflective boundary conditions (RBC), based on Newton’s restitution law and the foundations of analytical geometry, in the treatment of contours in a three-dimensional (3D) domain. In a previous paper [C. A. D. Fraga Filho, “An algorithmic implementation of physical reflective boundary conditions in particle methods: Collision detection and response,” Phys. Fluids 29, 113602 (2017)], RBC validation tests and simulation results were presented for a two-dimensional (2D) domain. The current work presents the validation of the collision detection and response algorithm employed for the RBC and its application in two cases (hydrostatics and hydrodynamics) in a 3D domain. Following an analysis of the simulation results, the applicability of the RBC to 3D continuum fluid dynamic problems is verified. In the hydrostatics case, a still liquid (Newtonian, incompressible, uniform, and isothermal) inside an immobile reservoir is studied. The fluid flow is modeled using an improved Smoothed Particle Hydrodynamics (SPH) formulation utilizing a modified concept of pressure. The simulation results are excellent, showing complete agreement with the analytical solution and the nonmotion of the particles throughout the simulation time. In the hydrodynamics case, 3D dam break flow modeling is carried out using the standard SPH formulation. Results provided by the RBC and standard SPH modeling are compared with the literature data demonstrating good agreement with the experimental findings.
Large deformation analysis of geomaterials using stabilized total Lagrangian smoothed particle hydrodynamics
(Elsevier, 2022-03) Islam, Md Rushdie Ibne
Smoothed particle hydrodynamics (SPH) based on Eulerian kernels is widely-used in large deformation analysis of geomaterials. Despite being popular, it has tensile instability and rank-deficiency; thus, it needs several numerical treatments to be stable. In this work, a stabilized total Lagrangian SPH method is presented, which is inherently free of tensile instability. A stiffness-based hourglass control algorithm is employed to cure the instability caused by rank-deficiency. Periodic update of reference configuration is employed to allow the modeling of large deformation. Numerical examples are presented to show the performance of the method. The comparison between the presented method and the conventional smoothed particle hydrodynamics are discussed. The influences of hourglass control and configuration update are also investigated. It is found that the presented method is robust and can model large deformation and plastic flows in geomaterials. Particularly, the stabilized method delivers better stress results.
Modelling dynamic brittle fracture with fourth-order phase-field integrated Eulerian Sph
(2025-05) Islam, Md Rushdie Ibne
Dynamic brittle fracture presents substantial numerical challenges due to the complex nature of crack initiation, propagation, branching, and fragmentation. In this work, we develop a fourth-order phase-field model for brittle fracture within the Eulerian Smoothed Particle Hydrodynamics (ESPH) framework. The use of higher-order spatial derivatives in the phase-field formulation enables enhanced resolution of crack topology, stable interfaces and smoother energy dissipation. The ESPH method, operating in the current configuration, is particularly suited for modelling large deformations and complex fracture behaviours without the need for remeshing, which might be required for mesh-based methods. We validate our model against several benchmark problems, such as dynamic crack branching in notched plates under tensile loading and asymmetric crack propagation in three-point bending tests. The results highlight the capability of the proposed fourth-order ESPH-phase-field model to accurately predict crack paths, branching, and coalescence phenomena with improved interface regularity and numerical robustness.
Multi-scale modelling of fatigue crack propagation due to liquid droplet impingement
(RSC, 2023-01) Islam, Md Rushdie Ibne
We develop a sequential multi-scaling framework for studying the problem of fatigue crack propagation due to liquid droplet impingement. The scope is limited to a hypothetical material and a hypothetical liquid. The multi-scaling is achieved by handshaking the atomistic scale molecular dynamics (MD) simulations with the continuum scale smoothed particle hydrodynamics (SPH). The handshaking, in turn, is performed by evaluating the material, the fracture and the loading properties from MD simulations, and using them as inputs in the continuum scale SPH model. Due to the qualitative agreement of the pressure developed in the fluid and the substrate between the MD simulations and already published results, the liquid droplet impact in SPH is simulated through appropriate surface stresses. Further, we incorporate the pseudo-spring approach within the SPH model to develop a methodology for studying mixed-mode fatigue crack propagation. Our methodology provides good agreement with the existing literature for several cases. Lastly, we calculate the fatigue life of an edge-cracked specimen due to liquid droplet impingement.
Multiscale modelling of fracture in graphene sheets
(Elsevier, 2022-12) Islam, Md Rushdie Ibne
Most of the continuum scale processes, such as fracture, plasticity, etc., trace their origin to atomistic scale phenomena. To gain deeper insights into these processes, one needs to understand the behaviour of materials through the lens of multiscale methods. In this manuscript, we study the problem of fracture crack propagation in graphene sheets through a sequential multiscaling technique. The continuum-mechanical smoothed particle hydrodynamics (SPH) is coupled with the atomistic scale molecular dynamics (MD) simulations through proper constitutive modelling — the non-linear material properties and the mechanical equation of state which serve as the inputs to the SPH model are evaluated directly from the MD simulations. Such handshaking ensures that the continuum-scale SPH model is able to faithfully reproduce the atomistic scale stress–strain behaviour until failure. Using a pre-notched continuum scale graphene sheet, we show that the mode-I stress intensity factor obtained from our SPH model agrees well with the published literature. We subsequently study crack propagation in pre-notched graphene sheets, where the influence of the orientation of the notch is evaluated. Lastly, we take the case of a continuum-scale graphene sheet having randomly oriented cracks and identify the changes in the stress–strain behaviour vis-à-vis a pristine graphene sheet.
Multiscale modelling of thermally stressed superelastic polyimide
(2025-04) Islam, Md Rushdie Ibne
Many thermo-mechanical processes, such as thermal expansion and stress relaxation, originate at the atomistic scale. We develop a sequential multiscale approach to study thermally stressed superelastic polyimide to explore these effects. The continuum-scale smoothed particle hydrodynamics (SPH) model is coupled with atomistic molecular dynamics (MD) through constitutive modelling, where thermo-mechanical properties and equations of state are derived from MD simulations. The results are verified through benchmark problems of heat transfer. Finally, we analyse the insulating capabilities of superelastic polyimide by simulating the thermal response of an aluminium plate. The result shows a considerable reduction in the thermal stress, strain and temperature field development in the aluminium plate when superelastic polyimide is used as an insulator. The present work demonstrates the effectiveness of the multi-scale method in capturing thermo-mechanical interactions in superelastic polyimide.
Numerical modeling of interfacial cracking with soft and hard inclusions
(Elsevier, 2023-11) Islam, Md Rushdie Ibne
In this work, we use pseudo-spring-augmented smoothed particle hydrodynamics (SPH) framework to understand how the crack paths differ in edge-cracked plates with inclusions when they are made of functionally graded material (FGM) versus homogeneous plates. Modeling crack propagation in such multi-component structural systems is necessary to uncover the underlying failure mechanisms. While traditionally researchers have used mesh-based techniques like the finite element method to understand crack propagation, these methods have limitations. Consequently, mesh-less techniques such as SPH are gaining popularity. After verifying our framework on a plate made of two materials, we compare and contrast the crack path propagation between FGM plates and homogeneous plates, both having soft and hard inclusions. The crack paths get influenced significantly due to the presence of inclusions. Regardless of the type, in presence of soft inclusions, plates fail due to the failure of the inclusion. On the other hand, cracks tend to deflect away from hard inclusions in both plates. The amount of deflection is governed by the relative stiffness of the plate material. Consequently, the deflection is different in FGM plates compared with homogeneous ones.
Numerical modelling of crack initiation, propagation and branching under dynamic loading
(Elsevier, 2020-02) Islam, Md Rushdie Ibne
In 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.
Numerical modelling of metal forming by SPH with multi-gpu acceleration
(SAE International, 2019) Islam, Md Rushdie Ibne
Large material distortion, plastic deformation and forging make the numerical modelling of metal forming a difficult task. Grid-based methods such as the Finite Element Method (FEM) are incapable of simulating this process as these schemes suffer from mesh distortion and mesh entanglement. The mesh-based numerical frameworks with discontinuous enrichment can model finite deformation problems with limited success. Moreover, the presence of flaws, multiple crack surfaces and their interaction make the simulation even more numerically and computationally intensive. In this regard, Lagrangian particle-based meshfree methods are more relevant. There exist several mesh-free methods and among these Smoothed Particle Hydrodynamics (SPH) is a truly meshfree method. In SPH the computational domain is discretised by a set of particles. A given particle interacts only with its neighbouring particles through a kernel function with a constant radius. The interaction between particles stops when the particles move out of each other’s influence domain. Due to the absence of mesh/grids, SPH is naturally equipped to handle large deformation problems. Based on SPH, a solver with multi GPU acceleration for modelling metal forming process is developed. SPH provides a detailed insight into the material deformation, accumulation of plastic strain, and material flow patterns. The effect of different parameters and their influence can also be investigated. The material hardening effects are considered. The presence of voids in the material, the asymmetry in the forging process, the material flaws and their interaction and evolution over time can be modelled accurately. In the present work, we discuss the current needs for a computational framework for metal forming, the limitations of existing simulation software and the potential advantages and disadvantages of SPH.
Numerical simulation of metal machining process with eulerian and total lagrangian SPH
(Elsevier, 2020-08) Islam, Md Rushdie Ibne
This paper presents numerical simulations of metal machining processes with Eulerian and Total Lagrangian Smoothed Particle Hydrodynamics (SPH). Being a mesh-free method, SPH can conveniently handle large deformation and material separation. However, the Eulerian SPH (ESPH) in which the kernel functions are computed based on the current particle positions suffers from the tensile instability. The original Total Lagrangian SPH (TLSPH) based on the initial configuration is free of this instability, but it needs update of reference configuration in large deformation problems. In this work, the two methods are employed to model several metal machining cases with impact, pressing, and cutting, the results are compared with reference solutions. It is found that both the two SPH methods can capture the salient phenomena in metal processing, e.g. strain localisation, large deformation, and material separation. The formulations, implementations, and performance of the two methods are compared.
On consistency and energy conservation in smoothed particle hydrodynamics
(Wiley, 2018-08) Islam, Md Rushdie Ibne
Energy conservation and consistency are not easy to achieve simultaneously in smoothed particle hydrodynamics (SPH). In this study, an efficient strategy is proposed to achieve energy conservation in an SPH framework with a consistent basis function. Herein, at every particle pair interaction, a correction term is introduced such that energy conservation is restored locally and, at the same time, the total variation of different variables due to the correction term is minimum. The final form of the proposed formulation is such that no additional computational effort is required and the simplicity of SPH is preserved. The theoretical error estimate of the proposed formulation is performed. The proposed scheme is also compared with benchmark SPH formulations in terms of the L2 error norm for representative functional derivatives both in regular and irregular particle distributions. Finally, the efficacy of the proposed formulation in conserving energy and maintaining accuracy is demonstrated via few elastic, elastic-plastic impact and fracture problems.
On the equivalence of Eulerian Smoothed Particle Hydrodynamics, Total Lagrangian Smoothed Particle Hydrodynamics and molecular dynamics simulations for solids
(Elsevier, 2022-03) Islam, Md Rushdie Ibne
Significant advances in nanoscale research have enabled the continuous miniaturization of devices. With the reduction in the size of the devices, it is important to identify if the continuum scale methods remain applicable to such small-scale systems. Motivated by this, the present work tries to understand the equivalence, or its lack thereof, of the continuum scale Eulerian Smoothed Particle Hydrodynamics (ESPH) and Total Lagrangian Smoothed Particle Hydrodynamics (TLSPH) with the atomistic scale molecular dynamics (MD) simulations. The equivalence is studied using four simple problems — (i) uniaxial tensile testing of a beam, (ii) stress profile in a pre-notched plate under small extension, (iii) head-on collision of two elastic rubber-like rings, and (iv) large deformation of a cantilever beam subjected to an impact at the free end. Using MD simulation data as the pseudo-experimental data, we show that both ESPH and TLSPH provide results that are qualitatively and quantitatively in agreement with the MD simulations if the properties at the continuum scale are obtained directly from the MD simulations, and the same initial conditions are chosen. The comparisons are based on the stress–strain behavior, the distribution of normal and shear stresses, the temporal evolution of the variables such as kinetic energy, etc.
Physical reflective boundary conditions applied to smoothed particle hydrodynamics method for solving three-dimensional fluid dynamics problems
(2019) Islam, Md Rushdie Ibne
The mixing of continuum and microscopic laws is a contradiction often existing in the boundary conditions utilised in meshfree particle methods. Boundary techniques employing fictitious (or ghost) particles and artificial forces (defined in the molecular microscopic scale) are still used in SPH simulations and should be avoided. Currently, there is an effort in replacing boundary techniques that mix concepts of different scales by others that respect the continuum laws. This paper aims to present the implementation of the physical reflective boundary conditions (RBC) in Smoothed Particle Hydrodynamics (SPH) method for solving three dimensional (3-D) fluid dynamics problems. In this work, SPH was applied to solve the physical conservation equations for a Newtonian, incompressible, uniform and isothermal fluid. Applications in hydrostatics and hydrodynamics are presented as well as the validation of the results in 3-D domains. Two problems were studied: a still fluid inside an immobile reservoir and dam breaking flow. The results achieved presented a good agreement with the analytical solution and literature data.
A pseudo-spring based SPH framework for studying fatigue crack propagation
(Elsevier, 2022-09) Islam, Md Rushdie Ibne
The existing smoothed particle hydrodynamics (SPH) approaches for propagating fatigue cracks involve either the deletion of the crack front particle or stopping all its interactions in the total Lagrangian form. Here, we adopt the pseudo-spring-based Eulerian form of SPH to model mode-I fatigue crack propagation. For modeling fatigue crack growth, only the interactions between the crack front particle and its neighbors, which display the largest axial stresses in the connected pseudo-springs, are stopped. We show that our framework can determine accurately the mode-I stress intensity factors (SIFs) and capture both the fatigue crack path and the fatigue life of different specimens.