Air Blast Pressure Research Articles

Investigating the performance of an airblast pressure swirl atomizer

Investigating the performance of an airblast pressure swirl atomizer

Performance of One-way Composite Reinforced Concrete Slabs under Explosive-induced Blast Loading

A finite element model is developed in ABAQUS/CAE to simulate the behavior of one-way reinforced concrete slabs under air-blast loading. Several published empirical equations have been utilized to model air-blast pressure, P(t), for different combinations of the explosive charges and standoff distances. The values of the peak overpressure have been taken from the field explosion tests conducted on four normal reinforced concrete (NRC) slabs of size 2000 mm x 1000 mm x 100 mm in the School of Civil, Environmental, and Mining Engineering, The University of Adelaide, Australia (2009). The slabs were doubly reinforced with HYSD steel re-bars of diameter 12 mm spaced at 100 mm c/c in the major bending plane (ρ = 1.34%) and 200 mm c/c in the other plane (ρ = 0.74%), where “c/c” is the center-to-center distance between two adjacent re-bars. A plasticity-based damage model for concrete and an explicit solver in ABAQUS/CAE are adopted in the finite element (FE) simulation. The available test results and finite element analysis predictions, including maximum mid-span displacement and damage to the RC slabs, are presented and weighed. The computed results are found in good agreement with the experimental ones. The validated model is used to examine the performance of RC slabs with 25% replacement of the conventional steel re-bars by the FRP re-bars of equivalent strength on the compression face only, remote face only, and both faces of the slab. The replacement has been done for higher strength and ductility. Substituted FRP re-bars are of (1) Aramid fiber-reinforced polymer (AFRP), (2) Basalt fiber-reinforced polymer (BFRP), (3) Carbon fiber-reinforced polymer (CFRP), and (4) Glass fiber-reinforced polymer (GFRP). The results are also compared with those obtained with a 50% replacement of the steel re-bars by the FRP re-bars.

Performance of masonry heritage building under air-blast pressure without and with ground shock

ABSTRACT In general, the blast-induced ground shock excites the foundation of the structure prior to the air-blast pressure because of the obvious reasons of difference in wave propagation velocities. However, the ground shock and air-blast pressure might act simultaneously on the structure for some standoff distance with a particular quantity of the explosive charge and cause severe damage than by air-blast pressure. Therefore, the ground shock and air-blast pressure both should be considered for estimating the structural response by such a near-field detonation. The objective of the present study is to assess the performance of the masonry heritage building under air-blast pressure without and with ground shock generated from on the ground spherical-shaped TNT explosive charge at varying standoff distances. The considered building is a heritage brick masonry structure in lime-surkhi mortar. The time lag between the ground shock and air-blast pressure for different scaled distances is evaluated. Stresses have been computed and are compared with the provisions of the Indian and Australian Standard Codes of Practice for Structural Use of Unreinforced Masonry. Also, the damage assessment has been carried out using the concrete-damaged plasticity (CDP) model available in the ABAQUS finite element program.

Air blast pressure characteristics of moving charge

Air blast pressure between moving charge and static charge are obviously different, however, due to the limitation of testing means, most blast or impact experiments were conducted under static state, which bring risks to evaluate safety of the target structures. In this paper, based on the finite element software and theoretical analysis, we investigated characteristics of the air blast pressure of moving charge. By introduced the toroidal distribution coefficient and radial distribution coefficient, a calculation model, used to calculate the overpressure with scope of relative distance at range of 0.4∼2 m/kg1/3 around blast center was established. The model could quickly calculate overpressure distribution around the blast center. Furthermore, isobars lines of moving charge were obtained by solving the model, some other phenomena were also analyzed.

Development of a Statistical Model for the Effects of Air Blast Pressure, Melting Time and Fuel Consumed on Iron Melting Rate of an Erythrophleum Suave lens Charcoal-Fired Cupola Furnace

This work was designed to investigate the effects of air blast pressure, melting time and fuel consumed on iron melting rate of an erythrophleum suaveolens charcoal-fired cupola furnace. A regression model was formulated and the model validation established the existence of statistically significant relationships between the control variables and iron melting rate. By using the experimental data, R2 value of 99.8 % was obtained, thus confirming that the model is fit since 99.8 % of the variation in melting rate could be explained by the control variables. The coefficients b0ec, b1ec, b2ec and b3ec are -434.656, 423.864, 1.188 and 1.858 respectively; and the output of the t- test showed that regression coefficients b1ec, b2ec and b3ec were not equal to zero (table t-value=t0.025, 11 = 2.201), hence they are statistically significant. The regression model developed in this work as explained by the model analysis can estimate the melting rate as a function of the control variables and form a basis for developing a computer software which may help energy and foundry managers to significantly monitor and improve on the melting rate of cupola furnace.

Blast testing of high performance geopolymer composite walls reinforced with steel wire mesh and aluminium foam

Two blast tests were conducted to study the blast resistance of high performance geopolymer composite walls reinforced with steel wire mesh (SWM) and aluminium foam (AF). Conventional reinforced concrete (CRC) walls were also tested as control specimens. In total seven walls were tested under different blast loading conditions. The first blast test was conducted on one 2260 mm × 2260 mm × 150 mm SWM reinforced, one 2260 mm × 1000 mm × 150 mm SWM reinforced and one 2260 mm × 1000 mm × 150 mm combined SWM and AF reinforced high performance geopolymer composite walls under 50 kg TNT explosives at a standoff distance of 2.3 m. The second blast test was conducted on one 2260 mm × 2260 mm × 150 mm SWM reinforced and one 2260 mm × 2260 mm × 150 mm combined SWM and AF reinforced high performance geopolymer composite walls under 100 kg TNT explosives on the ground at the same standoff distance. Blast tests were also performed on two 2260 mm × 2260 mm × 150 mm CRC walls under such two designed explosions to compare their behaviours with reinforced high performance geopolymer composite walls. LVDT (linear variable differential transformer) devices were used to record the deflection histories and pressure sensors were used to measure the airblast pressure histories. The testing results indicated that the combined SWM and AF reinforced high performance geopolymer composite walls had a better blast resistance than the CRC walls, and the SWM reinforced high performance geopolymer composite wall was superior to both.

MODELING THE MELTING RATE OF AN ERYTHROPHLEUM SUAVEOLENS CHARCOAL-FIRED CUPOLA FURNACE WITH OXYGEN ENRICHMENT

Scraps of cast iron were melted and the melt ratios for ES charcoal-fired cupola furnace with oxygen enrichment was 9.2:1. Multiple linear regression model was formulated for the effects of air pressure, melting time and fuel consumed on melting rate in the iron melting cupola furnace. An R2 value of 99.5% confirms the validity of the models and established the existence of statistically significant relationships between the melting rate and the control variables. The coefficients b0eco, b1eco, b2eco and b3eco are -941.940, 918.840, 1.117 and 3.897 respectively; and the results of the ttest indicated that regression coefficients b1eco, b2eco and b3eco were statistically significant and not equal to zero (as given by hypothesis ii) at 0.025 level of significance and 11 degrees of freedom (table t-value=t0.025, 11 = 2.201). The residuals’ average was zero with the standard deviation of approximately 1.0 implying that residuals were actually independent. The average variance inflation factor VIF of 1.562 indicated that multi co-linearity was not a problem (i.e. VIF < 4), which clearly demonstrated that air blast pressure; melting time and fuel consumed was not significantly interacting factors. The developed model can be used to develop a computer software to predict the behavior of melting rate of an erythrophleum suaveolens charcoal-fired cupola furnace with oxygen enrichment as a function of air blast pressure, melting time and fuel consumed.

Vichada meteorite impact effects from simulation of regional environmental consequences of a meteoroid impact on Earth

This study estimates the regional environmental consequences of the impactor extraterrestrial body that could produce the probable Vichada impact crater structure on the Vichada Plain, in Colombia, South America. This paper details the parameter assumptions upon which the estimation is made. It describes an approach to quantifying the principal impact processes that could have affected the landscape in the vicinity of the probable Vichada impact event in the past. The key parameters are impactor diameter, impactor density, impact velocity before atmospheric entry, impact angle, and the distance from the impact at which the environmental effects are to be calculated, and the target type of sedimentary rock or crystalline rock. These parameters were chosen with support from The Vichada Structure dimensions obtained from remote sensing data interpretation, regional geologic mapping and interpreted satellite data and ground-based gravity and magnetic anomalies. The calculations are based on compiled novel algorithms for estimating the thermal radiation emitted by the impact-generated vapor plume or fireball, and the intensity of seismic shaking. Model validation is performed by obtaining the approximates various dimensions of the Vichada impact crater and ejecta deposit, as well as estimating the severity of the air blasting both crater-forming and air burst impacts. We illustrate the utility of the calculations by examining the predicted environmental consequences in seven localities of the Colombian territory, through hypothetical impact scenarios occurring in Cumaribo and Puerto Carreño (Vichada), Puerto Inirida (Guainía), Puerto Gaitán and Villavicencio (Meta), Mitú (Vaupes) and Bogotá, D.C. It is concluded that the most wide-reaching environmental consequence is seismic shaking. Both ejecta deposit thickness and air-blast pressure decay much more rapidly with distance than with seismic ground motion. Close to the impact site, the most devastating effect is from thermal radiation; however, the curvature of the Earth implies that distant localities are shielded from direct thermal radiation because the fireball is below the horizon. These results would guide further detailed fieldwork hunting for direct impact crater evidence and interpret high-resolution geophysical studies and borehole that could be carried out in the probable Vichada impact crater area shortly.

Design of air blast pressure sensors based on miniature silicon membrane and piezoresistive gauges

Available commercial piezoelectric pressure sensors are not able to accurately reproduce the ultra-fast transient pressure occurring during an air blast experiment. In this communication a new pressure sensor prototype based on a miniature silicon membrane and piezoresistive gauges is reported for significantly improving the performances in terms of time response. Simulation results demonstrate the feasibility of a pressure transducer having a fundamental resonant frequency almost ten times greater than the commercial piezoelectric sensors one. The sensor uses a 5μm-thick SOI membrane and four P-type silicon gauges (doping level ≅ 1019 at/cm3) in Wheatstone bridge configuration. To obtain a good trade-off between the fundamental mechanical resonant frequency and pressure sensitivity values, the typical dimension of the rectangular membrane is fixed to 30μm x 90μm with gauge dimension of 1μm x 5μm. The achieved simulated mechanical resonant frequency of these configuration is greater than 40MHz with a sensitivity of 0.04% per bar.

Passive Control Systems for the Blast Enhancement of Glazing Curtain Walls Under Explosive Loads

Glass curtain walls are used in modern buildings as envelopes for wide surfaces due to a multitude of aspects. In glass curtain walls, tensile brittle panels are connected - through mechanical or adhesive joints - with steel frameworks or aluminum bracing systems, and due to the interaction of several structural components, the behaviour of the so assembled system is complex to predict, especially under exceptional loading conditions such as explosive events. In the paper, glazing curtain walls are investigated by means of Finite-Element (FE) numerical simulations, under the effect of air blast pressures of variable intensity. Their typical dynamic behaviour and criticalities under high-strain impact loads are first analyzed. By means of extended nonlinear dynamic FE parametric studies, innovative devices are applied to traditional curtain walls, at their support points, in order to improve their expected dynamic response. Two possible solutions, namely consisting of viscoelastic (VE) or elasto-plastic (PL) dampers, are proposed as passive control systems for the mitigation of maximum effects in the façade components deriving from the incoming blast pressures. As shown, although characterized by specific intrinsic mechanical behaviours, either VE or PL dampers can offer beneficial structural effects. In the first case, major advantages for the façade components derive from the additional flexibility and damping capacities of VE devices. In the latter case, PL dampers introduce additional plastic energy dissipation in the traditional curtain wall assembly, hence allowing preventing severe damage in the glazing components. It is thus expected that the current outcomes could represent a valid background for further experimental validation as well as detailed assessment and optimization of the proposed design concept.

Internal explosion tests for scaled subsurface magazines

A subsurface magazine is proposed to reduce the debris and the air-blast pressure caused by an accidental explosion. First, 1/20-scale indoor explosion model tests for subsurface magazines were conducted to examine the characteristics of an air-burst and ground shock vibration. It was found from the test results that the peak blast pressure ( P0) for an overburden thickness ( T) of 50 cm was 0.84–0.98 times that for T = 15 cm, and the P0 for a loading density R = 9.0 kg/m3 was 1.09–1.39 times that for R = 4.5 kg/m3. It was also found that the maximum ground shock velocity Vmax for T = 50 cm was 0.57–1.07 times that for T = 15 cm. Second, the P0 was formulated as a function of the scaled distance Z, T, and R. Third, the Vmax was formulated as a function of Z and T. Finally, these formulae were validated using the test data obtained by performing a 1/10-scale field test.

Formulation of a fuel spray SMD model at atmospheric pressure using Design of Experiments (DoE)

Abstract Herein we describe the application of historical data design under response surface methodology to formulate the correlation of the fuel spray SMD (Sauter Mean Diameter) with factors (viscosity, fuel injection pressure, air-blast pressure). The Design Expert software was used to analyze the experimental data to obtain the equation between the factors and the response. The range of the values of variables used in this experiment were viscosity of the fuels 9.71 × 10−4 Pa–1.207 × 10−3 Pa, the fuel injection pressure 0.1–1.0 MPa, the air-blast pressure from 0 Pa to 2000 Pa and a total of 120 test points were conducted. The data were converted into logarithmic scale in order to utilize the linear fitting function of the DoE (Design of Experiments). According to the ANOVA (analysis of variance), the most influential factor to the fuel spray SMD is fuel injection pressure, followed by fuel viscosity and air-blast pressure. R2 value of 0.9339 demonstrated that the regression equation obtained by historical data design fits the experimental results consistently.

Mitigation of Air-Blast Pressure Impulses on Building Envelopes through Blast Resistant Ductile Connectors

Mitigation of Air-Blast Pressure Impulses on Building Envelopes through Blast Resistant Ductile Connectors

Limits to Deflected Shape Assumptions of the SDOF Methodology for Analyzing Structural Components Subject to Blast Loading

This paper examines the deflected shape assumptions built into the single-degree-of-freedom (SDOF) methodology used for analyzing structural components subject to blast loading. Design professionals use the SDOF models to analyze blast effects on components. It is common knowledge that the SDOF method is an approximation, and is not suitable for large charges with short distances (lower scaled distance −Z). Current design guidelines establish the limit of Z=1.2 m/kg1/3 for using SDOF methodologies for blast-loaded components, which is equivalent to a peak pressure of 5,000 kPa; however, this paper shows that the limit may be significantly higher in Z value (or lower in peak pressure). Higher air-blast pressure and impulse combinations cause hinges to form before the assumed deflected shape dominates the response. Because transformation factors for SDOF are derived using static deflected shapes and the static collapse mechanism, the factors may not produce accurate or conservative responses for blast loading at lower scaled distances. Using the finite element multi-degree-of-freedom (FE-MDOF) model, the paper validates the accuracy of SDOF shape factors for large scaled distances, and shows that the static deflected shape assumptions do not apply at lower scaled distances with higher impulses. Limits to SDOF are established based on the equivalent shape factors, and the variability in the limits based on damping and mass are also discussed.

Experimental investigation of monolithic tempered glass fragment characteristics subjected to blast loads

A series of field blasting tests of glass windows to blast loadings have been recently conducted. This is the second paper to report the testing data on monolithic tempered glass windows. While the first paper reports the glass panel response and failure modes, the current paper concentrates on the glass fragments induced by the blast loadings. Thermally tempered glass has been often adopted for monolithic windows to reduce ejecting fragment hazards after window fracture. However, previous blast tests conducted on monolithic tempered glass reported that in addition to small cubic fragments the shattered glass panes could break into large and jagged fragments similar to the cases in annealed glass which poses much more debris threats than expected. A thorough study on tempered glass fragments produced by air blast pressure is therefore necessary for better protection of human safety. In this paper, fragment characteristics of monolithic tempered glass windows observed in blasting tests are analyzed and presented. 1.5m×1.2m monolithic panes of two commonly used thicknesses, i.e. 6mm and 10mm, fully clamped onto the opening of an enclosed RC frame were tested with 5–10kg TNT charge detonated at 4.5–12.3m stand-off distances. Glass fragment mass and splash distributions both in front of and behind the windows were evaluated with respect to reflected pressure and glass specification. Fragment size and shape were also analyzed. High-speed cameras were used to monitor glass window fracture processes. Fragment velocities were determined by post-processing the high-speed camera images. Fragment ejecting velocities were evaluated with respect to the reflected impulse. Negative pressure was found to significantly influence the fragment ejecting velocity and fragment splash distributions.

Impulsive loading on reinforced concrete wall

This paper deals with the air blast and ground shock parameters for reinforced concrete wall panels. In this investigation peak pressure, pressure wave front arrival time, rising time, decreasing time and duration of the positive pressure phase of air blast time history parameters, and peak particle acceleration, arrival time, shock wave duration and time lag between ground shock and air blast pressure arrival at structures of ground shock owing to air blast were determined experimentally. Empirical relationships have been developed between different parameters. Typical values measured due to various charge weights have been compared with results of previous researchers and Conwep. The SAP2000 was used for stress analysis of wall panels using experimental results. The methodology outlined can be used to estimate the blast response of reinforced concrete walls. It is concluded that an accurate analysis of structure response and damage of structures caused by a nearby surface explosion requires simultaneous consideration of ground shock and air blast pressure.

A damage mitigation measure for steel structures under blast loading

The number of explosive attacks on civilian buildings has recently increased and the pattern of damage inflicted on structures when an explosion takes place remains quite difficult to predict. This paper performs a 3-dimensional dynamic response and damage analysis on steel frame structure, subjected to blast loads created by explosive devices. In this study, advantages of using polymer cables as a means of damage mitigation are investigated. Results from this study shows that synthetic fiber ropes as bracing for steel structures reduce the horizontal displacements of structure caused by air blast pressure. The contribution of fiber ropes in structural stability is also presented.

Meso-Scale Simulation of Concrete: Blast and Penetration Effects and AAR Degradation

The study of concrete dam subjected to extreme loading conditions require theadoption of accurate constitutive equations. In this paper some recent results on the meso-scalesimulation of blast and penetration e ects on concrete will be discussed. The adopted meso-scale constitutive equation is the so-called Lattice Discrete Particle Model (LDPM) recentlyformulated at Rensselaer Polytechnic Institute. LDPM can accurately describe the macroscopicbehavior of quasi-brittle materials, and especially concrete, during elastic, fracturing, softening,and hardening regimes. Tensile dominated experimental tests under both dynamic conditionswere numerically simulated. After presenting examples of simulations relevant to quasi-staticand dynamic concrete behavior, LDPM simulation of the e ect of air blast pressure, on concretewill be discussed. Finally, the problem of the extrapolations of laboratory tests to actual in-situconditions is also presented.

Influence of venting areas on the air blast pressure inside tubular structures like railway carriages

In case of a terrorist bomb attack the influence and efficiency of venting areas in tubular structures like train carriages is of interest. The pressure–time function of an air blast wave resulting from a solid charge is first compared to that of a gas or dust explosion and the capability of a venting structure to fly away is assessed. Several calculations using fluid-structure interaction are performed, which show that after a certain distance from the explosion, the air blast wave inside a tubular structure becomes one-dimensional, and that the influence of venting areas parallel to the wave propagation direction is small. The pressure peak and the impulse at certain points in a tubular structure are compared for several opening sizes. The overall influence of realistic size venting devices remains moderate and their usefulness in mitigating internal explosion effects in trains is discussed.

A coupling of empirical explosive blast loads to ALE air domains in LS-DYNA®

A coupling method recently implemented in LS-DYNA® allows empirical explosive blast loads to be applied to air domains treated with the multi-material arbitrary Lagrangian-Eulerian (ALE) formulation. Previously, when simulating structures subjected to blast loads, two methods of analysis were available: a purely Lagrangian approach or one involving the ALE and Lagrangian formulations coupled with a fluid-structure interaction (FSI) algorithm. In the former, air blast pressure is computed with empirical equations and directly applied to Lagrangian elements of the structure. In the latter approach, the explosive as well as the air are explicitly modeled and the blast wave propagating through the ALE air domain impinges on the Lagrangian structure through FSI. Since the purely Lagrangian approach avoids modeling the air between the explosive and structure, a significant computational cost savings can be realized – especially so when large standoff distances are considered. The shortcoming of the empirical blast equations is their inability to account for focusing or shadowing of the blast waves due to their interaction with structures which may intervene between the explosive and primary structure of interest. The new method presented here obviates modeling the explosive and air leading up the structure. Instead, only the air immediately surrounding the Lagrangian structures need be modeled with ALE, while effects of the far-field blast are applied to the outer face of that ALE air domain with the empirical blast equations; thus, focusing and shadowing effects can be accommodated yet computational costs are kept to a minimum. Comparison of the efficiency and accuracy of this new method with other approaches shows that the ability of LS-DYNA® to model a variety of new blast scenarios has been greatly extended.