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Min Zhou - One of the best experts on this subject based on the ideXlab platform.
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energy dissipation in polymer bonded explosives with various levels of constituent plasticity and internal friction
Computational Materials Science, 2019Co-Authors: Amirreza Keyhani, Seokpum Kim, Yasuyuki Horie, Min ZhouAbstract:Abstract The ignition of energetic materials (EM) under dynamic Loading is mainly controlled by localized temperature spikes known as hotspots. Hotspots occur due to several dissipation mechanisms, including viscoplasticity, viscoelasticity, and internal friction along crack surfaces. To analyze the contributions of these mechanisms, we quantify the ignition probability, energy dissipation, damage evolution, and hotspot characteristics of polymer-bonded explosives (PBXs) with various levels of constituent plasticity of the energetic phase and internal crack face friction. Using PBX9501 consisting of HMX (Octahydro-1,3,5,7-Tetranitro-1,2,3,5-Tetrazocine) and Estane as a reference material, we analyze variants of this material with several values of the yield stress of the energetic phase and coefficients of internal crack face friction, while other parameters are kept unchanged. The impact Loading involves piston velocities between 200 and 1200 m/s. The analysis uses a Lagrangian cohesive finite element framework that explicitly accounts for finite-strain elastic-viscoplastic deformation of the grains, viscoelastic deformation of the binder, arbitrary crack initiation and propagation in the grains and the binder, debonding between the grains and the binder, contact between internal surfaces, friction and frictional heating along internal surfaces, heat generation resulting from inelastic bulk deformation, and heat conduction. To determine the ignition status of the material or “go” or “no-go” state, we use a criterion based on a criticality threshold obtained from chemical kinetics calculations. For PBX with various levels of HMX plasticity and friction, the probability of ignition, the evolution of dissipation caused by plasticity and friction, the density of cracks, and the locations of cracks are quantified. Results show that samples with higher levels of constituent plasticity (lower yield strengths) or lower levels of internal friction are less likely to ignite. The relative importance of plasticity and friction depends on Load Intensity, with frictional heating decreasing as Load Intensity increases. Although the overall viscoplastic heating outweighs the overall frictional heating, friction plays a very important role in hotspot development at all Load intensities analyzed, owing to the fact that frictional heating is more localized than viscoplastic heating. The predicted thresholds and ignition probabilities are expressed in a Load Intensity-Load duration relation for PBX with different constituent properties.
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geometry and size effects in response of composite structures subjected to water based impulsive Loading
2018Co-Authors: Siddharth Avachat, Tao Qu, Min ZhouAbstract:The Load-carrying capacity of composite structures under water-based impulsive Loads is an important consideration in design. The performance is inherently geometry and size dependent. Studies of the issues must be in relation to materials, structural geometries, and Loading conditions. Analyses have focused on the role of fiber orientation, fiber stiffness, and incident impulse Intensity on the deformation and failure in monolithic carbon-fiber and glass-fiber/epoxy composite plates and cylinders of similar mass and thickness. In experiments, structures are subjected to impulsive Loads of different intensities generated using the Underwater Shock Loading Simulator (USLS), a novel projectile-impact-based impulsive Loading facility. In situ high-speed digital imaging has been used to study the deformation and failure, focusing on the effects of Load Intensity, failure modes, and material heterogeneity. The experiments are combined with fully dynamic 3D Coupled Eulerian–Lagrangian (CEL) finite element simulations accounting for the effects of fluid–structure interactions (FSI) and in-ply and inter-ply cracking and failure. It is found that the carbon-fiber laminates provide higher blast resistance, but transmit a greater fraction of the incident impulse to the supports than the glass-fiber laminates. Damage through in-ply and inter-ply cracking in the carbon-fiber laminates is ~25% of that in the glass-fiber laminates. In the case of cylindrical structures, results show that cylindrical sandwich structures have superior blast resistance than cylindrical monolithic structures of equal mass with only relatively minor increases in wall thickness.
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high speed digital imaging and computational modeling of dynamic failure in composite structures subjected to underwater impulsive Loads
International Journal of Impact Engineering, 2015Co-Authors: Siddharth Avachat, Min ZhouAbstract:Abstract The Load-carrying capacity of composite structures under water-based impulsive Loads is evaluated in relation to different core materials and Load Intensity. The analysis focuses on the role of core density and the effect of varying structural attributes and environmental conditions on deformation and failure mechanisms in monolithic as well as sandwich composites. The structures analyzed are simply supported planar composites with PVC foam cores and E-glass/vinylester facesheets. For the analysis carried out, the material properties of the sandwich cores are varied while the total mass is kept constant. The structures are subjected to impulsive Loads of different intensities using a novel new projectile-impact-based facility called the Underwater Shock Loading Simulator (USLS). In-situ high-speed digital imaging and postmortem analysis are used to study the deformation and failure of individual components, focusing on the effects of Loading intensities, failure modes and material heterogeneity. Depending on the Loading rate, shear cracking and/or collapse are the primary failure modes of the polymeric foam cores. Core density and height also significantly influence the response and failure modes. On a per unit weight basis, structures with low density cores consistently outperform structures with high density cores because the former undergo smaller deflections, acquire lower velocities and transmit a smaller fraction of incident impulses. Scaling relations in the form of deflection and impulse transmitted as functions of core density and Load Intensity are obtained to provide guidance for structural design.
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prediction of probabilistic ignition behavior of polymer bonded explosives from microstructural stochasticity
Journal of Applied Physics, 2013Co-Authors: Ananda Barua, Seokpum Kim, Yasuyuki Horie, Min ZhouAbstract:Random variations in constituent properties, constituent distribution, microstructural morphology, and Loading cause the ignition of explosives to be inherently stochastic. An approach is developed to computationally predict and quantify the stochasticity of the ignition process in polymer-bonded explosives (PBXs) under impact Loading. The method, the computational equivalent of carrying out multiple experiments under the same conditions, involves subjecting sets of statistically similar microstructure samples to identical overall Loading and characterizing the statistical distribution of the ignition response of the samples. Specific quantities predicted based on basic material properties and microstructure attributes include the critical time to ignition at given Load Intensity and the critical impact velocity below which no ignition occurs. The analyses carried out focus on the influence of random microstructure geometry variations on the critical time to ignition at given Load Intensity and the critic...
Peng Ren - One of the best experts on this subject based on the ideXlab platform.
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dynamic response and failure of pvc foam core metallic sandwich subjected to underwater impulsive Loading
Composites Part B-engineering, 2016Co-Authors: Nan Ye, Peng Ren, Wei Zhang, Wei Huang, Yubo GaoAbstract:Abstract The sandwich structures with metallic facesheets and PVC foam cores subjected to water-based impulsive Loads are investigated experimentally. The blast resistance in terms of dynamic deformation, failure modes and associated mechanisms is evaluated in relation to the effect of Load Intensity, core density and core height under air-backed and water-backed conditions. The plates are subjected to underwater impulsive Loads of different intensities with a lab-scaled underwater explosive simulator. 3D digital imaging correlation and postmortem analysis are used to investigate the deformation and failure of individual components, focusing on the effects of Loading intensities, structural properties and Loaded conditions. The primary failure modes of cores transfer from core crushing and inelastic deformation to cracks and fragmentation with the increasing applied impulse and core density. The distinct trends of deflection shown by front faces and back faces are influenced by the effect of core density significantly. Unlike the air-backed condition, water-backed condition affects the damage and deflection of the sandwich structure in a different way because of the critical Intensity of impulsive Loads. Quantitative structure-Loading-performance relation is carried out to provide guidance for structural design.
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Dynamic failure of honeycomb-core sandwich structures subjected to underwater impulsive Loads
European Journal of Mechanics A Solids, 2016Co-Authors: Wei Huang, Wenbo Xie, Dacheng Li, Nan Ye, Wei Zhang, Peng RenAbstract:The aluminum sandwich structures with hexagonal honeycomb cores subjected to water-based impulsive Loading are studied experimentally. The blast resistance in terms of dynamic deformation, failure modes and associated mechanisms is evaluated in relation to the Load Intensity, core relative density under air-backed and water-backed conditions. 3D digital imaging correlation and postmortem analysis are used to investigate the deformation and failure of individual components, focusing on the effects of Loading intensities, core relative density and Loaded condition. The failure mode maps of sandwich panels are summarized to study the different regimes of deflection resistance in different experimental cases. The results show that the effect of relative core density significantly influences the blast resistance of sandwich panels under the different Loaded conditions. The sandwich panels with denser cores perform better blast resistance at high impulsive Loads under air-backed condition. Only slight discrepancy of deflection resistance has been observed under the water-backed condition. The honeycomb sandwich panels suffer significantly smaller backface deflections than solid plates of identical mass per area under air-backed condition, while the discrepancy of deflection is negligible under the water-backed condition.
Wei Huang - One of the best experts on this subject based on the ideXlab platform.
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dynamic response and failure of pvc foam core metallic sandwich subjected to underwater impulsive Loading
Composites Part B-engineering, 2016Co-Authors: Nan Ye, Peng Ren, Wei Zhang, Wei Huang, Yubo GaoAbstract:Abstract The sandwich structures with metallic facesheets and PVC foam cores subjected to water-based impulsive Loads are investigated experimentally. The blast resistance in terms of dynamic deformation, failure modes and associated mechanisms is evaluated in relation to the effect of Load Intensity, core density and core height under air-backed and water-backed conditions. The plates are subjected to underwater impulsive Loads of different intensities with a lab-scaled underwater explosive simulator. 3D digital imaging correlation and postmortem analysis are used to investigate the deformation and failure of individual components, focusing on the effects of Loading intensities, structural properties and Loaded conditions. The primary failure modes of cores transfer from core crushing and inelastic deformation to cracks and fragmentation with the increasing applied impulse and core density. The distinct trends of deflection shown by front faces and back faces are influenced by the effect of core density significantly. Unlike the air-backed condition, water-backed condition affects the damage and deflection of the sandwich structure in a different way because of the critical Intensity of impulsive Loads. Quantitative structure-Loading-performance relation is carried out to provide guidance for structural design.
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Dynamic failure of honeycomb-core sandwich structures subjected to underwater impulsive Loads
European Journal of Mechanics A Solids, 2016Co-Authors: Wei Huang, Wenbo Xie, Dacheng Li, Nan Ye, Wei Zhang, Peng RenAbstract:The aluminum sandwich structures with hexagonal honeycomb cores subjected to water-based impulsive Loading are studied experimentally. The blast resistance in terms of dynamic deformation, failure modes and associated mechanisms is evaluated in relation to the Load Intensity, core relative density under air-backed and water-backed conditions. 3D digital imaging correlation and postmortem analysis are used to investigate the deformation and failure of individual components, focusing on the effects of Loading intensities, core relative density and Loaded condition. The failure mode maps of sandwich panels are summarized to study the different regimes of deflection resistance in different experimental cases. The results show that the effect of relative core density significantly influences the blast resistance of sandwich panels under the different Loaded conditions. The sandwich panels with denser cores perform better blast resistance at high impulsive Loads under air-backed condition. Only slight discrepancy of deflection resistance has been observed under the water-backed condition. The honeycomb sandwich panels suffer significantly smaller backface deflections than solid plates of identical mass per area under air-backed condition, while the discrepancy of deflection is negligible under the water-backed condition.
Bengt Lundberg - One of the best experts on this subject based on the ideXlab platform.
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stationary contact between a cylindrical metallic projectile and a flat target surface under conditions of dwell
International Journal of Impact Engineering, 2004Co-Authors: Rene Renstrom, Patrik Lundberg, Bengt LundbergAbstract:Abstract Armour systems capable of defeating an incoming projectile on the surface of a ceramic target have been reported. This capability, called interface defeat or dwell, signifies that the projectile material is forced to flow radially on the surface of the target without penetrating significantly. Under such flow conditions, the hydrodynamic pressure is normally the most important part of the normal Load on the target surface. Therefore, projectile properties such as yield strength and compressibility are commonly ignored or assumed to contribute only marginally. In order to investigate the effects of these properties, an analytical expression was derived for the normal Load from a cylindrical metallic projectile impacting on a flat, rigid and friction-free surface, which includes the contributions from yield strength and compressibility in addition to that of inertia. At an impact velocity representative of today's ordinance velocities, the contributions to Load Intensity on the axis from yield strength and compressibility were found to be 15% and 3.4%, respectively, of that of inertia. The analytical results and Autodyn-2D numerical simulations show good agreement within a projectile radius from the axis.
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impact of metallic projectiles on ceramic targets transition between interface defeat and penetration
International Journal of Impact Engineering, 2000Co-Authors: Patrik Lundberg, Rene Renstrom, Bengt LundbergAbstract:The purpose of this thesis is to gain understanding of the Load on flat target surfaces produced by projectile impact. Models are proposed from which upper and lower bounds can be derived for the transition be-tween interface defeat and normal penetration.It is shown that the dominating contribution to the normal Load is generally provided by the hydrodynamic pressure due to the effect of inertia. In addition it is shown that the contributions from yield strength and compressibility are also significant. For a cylindrical tungsten alloy projectile at an impact velocity representative of to-day’s ordnance velocities, the contributions to the Load Intensity on the axis of symmetry from yield strength and compressibility are shown to be 15% and 3.4%, respectively, of that of inertia.Impact tests have shown that for conical projectiles transition from interface defeat to penetration occurs at a significantly lower impact velocity than for cylindrical projectiles. In order to better understand the influence of projectile shape, a conical projectile in axi-symmetric impact is studied by use of an analytical model for self-similar flow, and the results obtained are compared to results of numerical simula-tions. It is shown how the maximum Load Intensity, and the position of the maximum, depends on the apex angle. For an apex angle of 90o, the maximum Load Intensity is found to be almost three times that pro-duced by a cylindrical projectile with the same impact velocity. This maximum occurs well off the axis of symmetry and is 20% larger than the Load Intensity at this axis. Both the self-similar model and the nu-merical simulations show that the contribution to the Load Intensity from compressibility is positive below and negative above an apex angle of around 80o. The contribution of yield strength to the Load in-tensity at centre of impact depends only weakly on the apex angle and is therefore similar to that of a cylindrical projectile.
Siddharth Avachat - One of the best experts on this subject based on the ideXlab platform.
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geometry and size effects in response of composite structures subjected to water based impulsive Loading
2018Co-Authors: Siddharth Avachat, Tao Qu, Min ZhouAbstract:The Load-carrying capacity of composite structures under water-based impulsive Loads is an important consideration in design. The performance is inherently geometry and size dependent. Studies of the issues must be in relation to materials, structural geometries, and Loading conditions. Analyses have focused on the role of fiber orientation, fiber stiffness, and incident impulse Intensity on the deformation and failure in monolithic carbon-fiber and glass-fiber/epoxy composite plates and cylinders of similar mass and thickness. In experiments, structures are subjected to impulsive Loads of different intensities generated using the Underwater Shock Loading Simulator (USLS), a novel projectile-impact-based impulsive Loading facility. In situ high-speed digital imaging has been used to study the deformation and failure, focusing on the effects of Load Intensity, failure modes, and material heterogeneity. The experiments are combined with fully dynamic 3D Coupled Eulerian–Lagrangian (CEL) finite element simulations accounting for the effects of fluid–structure interactions (FSI) and in-ply and inter-ply cracking and failure. It is found that the carbon-fiber laminates provide higher blast resistance, but transmit a greater fraction of the incident impulse to the supports than the glass-fiber laminates. Damage through in-ply and inter-ply cracking in the carbon-fiber laminates is ~25% of that in the glass-fiber laminates. In the case of cylindrical structures, results show that cylindrical sandwich structures have superior blast resistance than cylindrical monolithic structures of equal mass with only relatively minor increases in wall thickness.
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high speed digital imaging and computational modeling of dynamic failure in composite structures subjected to underwater impulsive Loads
International Journal of Impact Engineering, 2015Co-Authors: Siddharth Avachat, Min ZhouAbstract:Abstract The Load-carrying capacity of composite structures under water-based impulsive Loads is evaluated in relation to different core materials and Load Intensity. The analysis focuses on the role of core density and the effect of varying structural attributes and environmental conditions on deformation and failure mechanisms in monolithic as well as sandwich composites. The structures analyzed are simply supported planar composites with PVC foam cores and E-glass/vinylester facesheets. For the analysis carried out, the material properties of the sandwich cores are varied while the total mass is kept constant. The structures are subjected to impulsive Loads of different intensities using a novel new projectile-impact-based facility called the Underwater Shock Loading Simulator (USLS). In-situ high-speed digital imaging and postmortem analysis are used to study the deformation and failure of individual components, focusing on the effects of Loading intensities, failure modes and material heterogeneity. Depending on the Loading rate, shear cracking and/or collapse are the primary failure modes of the polymeric foam cores. Core density and height also significantly influence the response and failure modes. On a per unit weight basis, structures with low density cores consistently outperform structures with high density cores because the former undergo smaller deflections, acquire lower velocities and transmit a smaller fraction of incident impulses. Scaling relations in the form of deflection and impulse transmitted as functions of core density and Load Intensity are obtained to provide guidance for structural design.