Pressure Pulse Loading Research Articles

Microscopic Physical and Chemical Responses of Slip Systems in the <em>β</em>-HMX Single Crystal under Low Pressure and Long Pulse Loading

Microscopic Physical and Chemical Responses of Slip Systems in the <em>β</em>-HMX Single Crystal under Low Pressure and Long Pulse Loading

Response of sandwiches undergoing static and blast pulse loading with tailoring optimization and stitching

A numerical study is presented where tailoring optimization and stitching are applied to improve the structural performances of sandwich plates undergoing static and blast pulse pressure loading. The purpose is to recover the critical interlaminar stresses at the interface with the core and contemporaneously keep maximal the flexural stiffness. Optimized distributions of the stiffness properties for the faces are obtained solving an extremal problem whose target is the minimization of the energy due to transverse shear and bending stresses under spatial variation of the stiffness properties, along with the maximization of the energy due to in-plane stresses. The contribution of stitching is computed through 3D finite element analysis and it is incorporated as modified elastic moduli into the refined, hierarchic zig-zag model employed as structural model to carry out the analysis accurately accounting for the layerwise effects of the out-of-plane transverse shear and transverse normal stresses and deformations. Approximate solutions giving the ply fibre orientation at any point (compatible with the current manufacturing technologies) are considered in the numerical applications. The numerical results show that stitched sandwiches incorporating optimized low-cost glass-fibre plies can achieve the same bending stiffness as sandwiches with uniform stiffness carbon-fibre faces, with a consistent reduction of critical out-of-plane stresses. The amplitude of vibrations under blast pulse loading can be consistently reduced with a proper choice of the curvilinear paths of fibres incorporated in the faces.

Local facesheet pulse buckling in a curved, composite sandwich panel

Local facesheet buckling of a curved sandwich panel subjected to external pressure pulse loading was investigated in this paper. Equations of motion for the facesheet transient deformations in the sandwich shell were derived from Lagrange’s equations of motion, and solutions using this approach compared well with FEA results from ABAQUS Standard. Both facesheet fracture during stable deformation response and local dynamic pulse buckling of facesheets were considered as possible modes of failure in the curved sandwich panel. Parametric studies indicated that local facesheets buckling is more likely to occur than facesheet fracture in thin and deep curved sandwich panels. The facesheet laminate layup can also be adjusted to improve the local buckling resistance of the curve panel.

Transient pressure loading of clamped metallic plates with pre-formed holes

The combined effect of blast and impact loading against protective structures is still not fully understood. In this paper, the motivation is to investigate the combined effect of pressure and fragment loading on steel plates. To simplify the approach, it is assumed that the fragments strike and perforate the flexible target before the pressure load arrives. These perforations are idealized as pre-formed holes of generalized shapes in thin, ductile Docol 600DL steel plates, which are then subjected to controlled pressure pulses in the laboratory. The tests were carried out in a Pulse Pressure Loading Rig, and two different pressure levels were applied for each plate design. After the tests, the deflections caused by the pressure pulses were measured. Even though the plates were much deformed in some of the tests, no sign of failure was observed. Based on a number of material tests, the parameters in the modified Johnson–Cook constitutive relation were identified. Several sets of non-linear finite element simulations of the pressure loading process were then conducted. The agreement between standard Lagrangian simulations and the experimental results was in general good, but the simulations failed to give an accurate description of the deflection around the pre-formed holes. Fully coupled FSI simulations of the experimental tests were then carried out and these simulations demonstrate significant spatial variation of the pressure load. The FSI simulations also showed that this spatial variation of the pressure load influence the deflection profile, especially in the vicinity of the holes.

On pulse pressure loading of plates with holes

Abstract This paper reports the application of an energy solution to a complex problem involving large inelastic deformation in thin, clamped ductile square plates with either square or circular holes under the action of transverse pulse pressure loading. The work is part of a collaborative project to study blast loading of steel plates with penetrations as used for deck plating or bulkheads that may be required to resist loading far in excess of their design limit due to the effects of an accidental explosion. A novel differential pressure loading device was used to impart dynamic loading to 1/8 scaled 0.5 m, 1.1 mm thick, clamped mild steel square plates with a central aperture up to 4% of the plate area. This data was used to validate the energy approach that considers both plastic hinge formation and extensional effects. Accounting for strain rate, scaling and dynamic effects in the tests gave more than acceptable results when compared with final deflections in the tested plates. It is concluded that the energy approach together with small-scale test validation paves the way for a versatile robust design methodology which can be used to advantage for screening purposes and/or early stage conceptual design studies.

Performance of Glare panels subjected to intense pressure pulse loading

AbstractA robust and efficient computational model has been developed which is capable of modelling the dynamic non-linear behaviour of Glare panels subjected to blast loadings. High strain rate material characterisation and modelling of interfacial debonding between adjacent sublaminates have been taken into consideration. Numerical model validation have been performed considering case studies of Glare panels subjected to a blast-type pressure pulse for which experimental data on the back face- displacement and post-damage observations were available. Excellent agreement of mid-point deflections and evidence of severe yield line deformation were shown and discussed against the performed blast tests. A further parametric study identified Glare as a potential blast attenuating structure, exhibiting superior blast potential against monolithic aluminium plates. The results were normalised and showed that for a given impulse, Glare exhibited a smaller normalised displacement, outperforming monolithic Aluminium 2024-T3 plates. It was concluded that further work needed to be carried out to take into account the influence of geometry (cylindrical structures), pre-pressurisation effects and boundary conditions

Pressure pulse response of composite sandwich panels with plastic core damping

An analytical technique is presented for obtaining the large amplitude, damped response of a foam-core composite sandwich panel subjected to uniform pressure pulse loading. The predicted panel response was in agreement with finite element analysis, and it was used to examine the blast resistance of panels with various foam cores. Although blast resistance generally increased with the increasing core density, panels with the densest cores exhibited no energy absorption before panel failure. The panel with the PVC H200 foam also sustained higher failure pressure per unit areal weight density than the denser panels with Klegecell R300 and HCP100 foams.

Shock loading of 3D woven composites: A validated finite element investigation

Abstract In a companion paper in this issue (Pankow et al., 2010 [1] ), experimental results for the deformation response of 3D glass fiber textile composites subjected to shock wave pulse pressure loading were presented. In this paper, finite element models are developed to simulate the deformation response and damage development observed in the experiments. Two levels of models are presented, with the first focused on a layered, homogenous orthotropic model that examined the bulk macroscopic deformation response. In the second model, each layer is represented to capture the interactions between fiber tows and matrix, taking into account the discrete non-homogeneous material distribution in each layer. Both models incorporated a user defined subroutine within the commercial software ABAQUS to capture matrix micro-cracking, which is responsible for damage development and growth. Results from the computational models correlated well with experimental results and observed locations of matrix micro-cracking.

The influence of elastic shear deformation on the transverse shear failure of a fully clamped beam subjected to idealized blast loading

The influence of elastic shear deformation on the transverse shear response of a fully clamped beam is investigated in the present paper. The beam is made from a rigid, perfectly plastic material and subjected to a uniformly distributed pressure pulse loading. The elastic shear deformation is idealized by an elastic, perfectly plastic spring with a constant spring coefficient. Analytical solutions are obtained for the transverse shear response, which are then used to predict the occurrence of a transverse shear failure. The method presented in the paper may be extended to study the blast-induced shear failure of other structural elements when the elastic shear deformation needs to be considered.

Pulse pressure loading of aircraft structural panels

The main aim of the work reported in this paper was to assess the reponse of panels representative of aircraft structures, to pulse pressure loading by means of experimental and finite element (FE) techniques. A series of experiments were conducted to compare the responses and failure modes of stiffened, aluminium alloy panels, joined using conventional riveting techniques and laser welding. The failure pressures of the riveted panels ranged from 29 to 36 kPa and a number of principal modes of failure were identified, namely (1) rivet shear/tensile failure, (2) frame buckling, (3) stringer buckling and (4) frame rupture. In the case of the laser-welded panels, failure pressures were between 28 and 33 kPa and failure was dominated by significant tearing along the weld heat affected zone at the frame–skin interface. The FE models correctly modelled most of the principal modes of failure observed experimentally and central panel displacement was also predicted well up until the time at which failure initiated.

Stress analysis of carotid plaque rupture based on in vivo high resolution MRI

Atheromatous carotid plaque rupture is responsible for the majority of ischaemic strokes in the developed world. Plaque rupture has been associated with plaque morphology, plaque components’ properties, inflammation and local stress concentration. High resolution multi-spectral magnetic resonance imaging (MRI) has allowed the plaque components to be visualized in vivo. This study combined the recent advances in finite element analysis (FEA) and MRI, and performed stress analysis of five vulnerable carotid plaques based on the geometry derived from in vivo MRI. Image segmentation was based on multi-spectral MRI and co-registered with histology for plaque characterization. Plaque fibrous cap, lipid pool and vessel wall were modelled as isotropic, incompressible hyperelastic materials undergoing large deformation under pulse pressure loading. High stress concentrations were predicted at the shoulders and the thinnest fibrous cap regions of the plaque, and the mean maximal stresses were found to be higher in the ruptured plaques (683.3 kPa) than those in the unruptured plaques (226.9 kPa). The effect of the relative stiffness of fibrous cap to lipid pool on the stress within the cap itself was studied. It was shown that larger relative stiffness of fibrous cap to lipid pool resulted in higher stress within the cap. Thus, it is likely that high stress concentrations in vulnerable plaque may cause plaque rupture and lead to acute ischaemic sequelae. A combination of in vivo high resolution MRI and FEA could potentially act as a useful tool to assess plaque vulnerability and risk stratify patients with carotid atheroma.

Pulse–pressure loading effects on aviation and general engineering structures—review

This paper reviews various aspects of modeling an explosion on an aircraft, which can be extended to more general structures. A brief summary of material and structural models is given, followed by a detailed history of pulse–pressure loading models with an emphasis on free–free beams and how pulse characteristics affect a structure's response. Techniques to desensitize pulse shape effects are discussed, which culminate in the form of pressure–impulse isodamage curves. Studies using random loading models are also presented.

Deformation and failure of profiled stainless steel blast wall panels. Part III: finite element simulations and overall summary

This three-part article presents the results of experimental, analytical and numerical studies on the response of 1 4 scale stainless steel blast wall panels and connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Part I reported on the experimental investigations, whilst the analytical modelling considerations were examined in Part II. Finite element analysis, with ABAQUS, was used to simulate the blast wall panel behaviour and is discussed in Part III. Large permanent plastic deformations were produced in the panels without rupture, and localised buckling developed at the centre of the corrugations. The work highlights the importance of correctly modelling the support details and the variation in strength with blast direction (the blast wall panels being stronger in the design direction). The modelling approaches predict a design capacity that is 39% higher than the current design guidance predicts, as a result of modelling the supports and including membrane action.

Scaling of pulse loaded mild steel plates with different edge restraint

This paper reports the results of scaled tests on mild steel square plates with different edge restraint subjected to uniformly distributed triangular pulse pressure loading producing large inelastic deformations without tearing or rupture. The loading is representative of overpressure loading arising from a confined hydrocarbon explosion. A scale factor of 0.5 was examined in this series of tests on 16 plates, eight 1 m by 1 m × 2 mm thick and eight 0.5 m × 0.5 m × 1 mm thick. Both static and dynamic test results are presented. A quasi-static rigid–plastic and elastic–plastic analysis of a fully restrained square plate is also presented and compared with the test results. The transient response of the plates under dynamic loading show some divergence from the laws of geometrically similar scaling while the permanent deformations in both the static and dynamic tests show good compliance with the laws of similitude, within the accuracy expected in such tests.

Scale Testing Of Profiled Stainless Steel BlastWalls

A series of laboratory tests were carried out at the University of Liverpool Impact Research Centre on panels of ¼ scale stainless steel blast walls and on various panel/connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the test panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Large permanent plastic deformations were produced in the panel without rupture. The work has shown that the connection detail can significantly influence the response of the panel to extreme pressure loading.

Inelastic deformation and failure of profiled stainless steel blast wall panels. Part I: experimental investigations

This three-part article presents the results of experimental, analytical and numerical studies on the response of 1 4 scale stainless steel blast wall panels and connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Part I reports on the experimental investigations, whilst the analytical modelling considerations are examined in Part II. Finite element analysis, with ABAQUS, was used to simulate the blast wall panel behaviour and is discussed in Part III. Large permanent plastic deformations were produced in the panels without rupture, and localised buckling developed at the centre of the corrugations. The work highlights the importance of correctly modelling the support details and the variation in strength with blast direction (the blast wall panels being stronger in the design direction). The modelling approaches predict a design capacity that is 39% higher than the current design guidance predicts, as a result of modelling the supports and including membrane action.

Inelastic deformation and failure of profiled stainless steel blast wall panels. Part II: analytical modelling considerations

This three-part article presents the results of experimental, analytical and numerical studies on the response of 1/4 scale stainless steel blast wall panels and connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Part I reports on the experimental investigations, whilst the analytical modelling considerations are examined in Part II. Finite element analysis, with ABAQUS, was used to simulate the blast wall panel behaviour and is discussed in Part III. Large permanent plastic deformations were produced in the panels without rupture, and localised buckling developed at the centre of the corrugations. The work highlights the importance of correctly modelling the support details and the variation in strength with blast direction (the blast wall panels being stronger in the design direction). The modelling approaches predict a design capacity that is 39% higher than the current design guidance predicts, as a result of modelling the supports and including membrane action.

Experimental investigation of corner-supported architectural glazing under pulse pressure loading

City centre bombings demonstrate the vulnerability of buildings to the effects of an explosion. Glazing panels on buildings, which shatter in the blast, are the main cause of injury due to the high-velocity fragments produced. A special test facility recently developed in the University of Liverpool Impact Research Centre has been used to investigate the dynamic behaviour of glazing components under pulse pressure loading. The type of glazing system studied in this work is supported at discrete points, unlike conventional glazing systems, which are usually supported along all edges. Novel experimental techniques have been used successfully to apply dynamic pressure pulses to full-size, 1 m by 1 m by 10mm thick glazing panels supported at four corner points under controlled laboratory conditions.

Inelastic deformation and failure of clamped aluminium plates under pulse pressure loading

An experimental and analytical study is presented of the inelastic deformation and failure (rupture) of clamped aluminium plates measuring 0.5 m×0.5 m at the clamped edge by 1 mm thick under pulse pressure loading. The pulse loading was applied by generating a dynamic pressure gradient across the plates using a fast differential pressure device. Both static and dynamic test results are reported together with the results of an investigation of the failure surface using scanning electron microscopy. An assumed-modes, elastic–plastic analysis of the plates using a finite strip model was used to predict the maximum displacement of the plates. A simple uniaxial strain-based failure criterion was used in the analysis to predict the failure pressure of the ruptured plates. The rigid-plastic method was used to estimate the permanent deformation of some of the plates. Reasonable agreement is obtained between the predictions of the simplified elastic–plastic analysis and the experimental results. The rigid-plastic results were less accurate at predicting the permanent deformation of the plates due to the long duration of the loading relative to the fundamental natural period of the plates.

Bifurcation Buckling Analysis of Conical Roof Shell Subjected to Dynamic Internal Pressure by the Finite Element Method

Cylindrical tanks with conical roof shells are utilized as oil storage tanks and for some containment vessels. It is known that conical roof shells and torispherical shells subjected to static internal pressure buckle into a displaced shape with circumferential waves caused by an instability condition commonly called bifurcation buckling. It can be important to obtain the dynamic bifurcation buckling load in designing conical roof shells. In this paper, the bifurcation buckling pressure is calculated for dynamic pressure during accident conditions as characterized by step pressure loading, ramp pressure loading and pulse pressure loading. The minimum bifurcation buckling pressure is shown to be a linear function of radius-to-thickness ratio R/h of the shell in a linear fashion on a logarithmic scale. The minimum bifurcation buckling pressure is minimum for conical roof shells subjected to the step loading. The minimum dynamic bifurcation buckling pressure for step loading is about half of the static bifurcation buckling pressure.