scholarly journals Guidelines to inform the generation of clinically relevant and realistic blast loading conditions for primary blast injury research

2021 ◽  
pp. bmjmilitary-2021-001796
Author(s):  
J W Denny ◽  
A S Dickinson ◽  
G S Langdon
Keyword(s):  
Blast Wave ◽  
Blast Loading ◽  
Wave Interaction ◽  
Blast Waves ◽  
Experimental Investigations ◽  
Loading Conditions ◽  
Primary Blast ◽  
Blast Overpressure ◽  
Engineering Theory ◽  
Blast Traumatic Brain Injury

‘Primary’ blast injuries (PBIs) are caused by direct blast wave interaction with the human body, particularly affecting air-containing organs. With continued experimental focus on PBI mechanisms, recently on blast traumatic brain injury, meaningful test outcomes rely on appropriate simulated conditions. Selected PBI predictive criteria (grouped into those affecting the auditory system, pulmonary injuries and brain trauma) are combined and plotted to provide rationale for generating clinically relevant loading conditions. Using blast engineering theory, explosion characteristics including blast wave parameters and fireball dimensions were calculated for a range of charge masses assuming hemispherical surface detonations and compared with PBI criteria. While many experimental loading conditions are achievable, this analysis demonstrated limits that should be observed to ensure loading is clinically relevant, realistic and practical. For PBI outcomes sensitive only to blast overpressure, blast scaled distance was demonstrated to be a useful parameter for guiding experimental design as it permits flexibility for different experimental set-ups. This analysis revealed that blast waves should correspond to blast scaled distances of 1.75<Z<6.0 to generate loading conditions found outside the fireball and of clinical relevance to a range of PBIs. Blast waves with positive phase durations (2–10 ms) are more practical to achieve through experimental approaches, while representing realistic threats such as improvised explosive devices (ie, 1–50 kg trinitrotoluene equivalent). These guidelines can be used by researchers to inform the design of appropriate blast loading conditions in PBI experimental investigations.

scholarly journals Defining blast loading ‘zones of relevance’ for primary blast injury research: A consensus of injury criteria for idealised explosive scenarios

2021 ◽  
Author(s):  
Jack Denny ◽  
Alexander Dickinson ◽  
Genevieve Langdon
Keyword(s):  
Blast Wave ◽  
Blast Loading ◽  
Wave Interaction ◽  
Blast Injury ◽  
Blast Injuries ◽  
Loading Conditions ◽  
Primary Blast ◽  
Injury Criteria ◽  
The 1960S ◽  
Injury Research

Blast injuries remain a serious threat to defence and civilian populations around the world. ‘Primary’ blast injuries (PBIs) are caused by direct blast wave interaction with the human body, particularly affecting air-containing organs. Despite development of blast injury criteria since the 1960s, work to define blast loading conditions for safety limits, protective design and injury research has received relatively little attention. With a continued experimental focus on PBI mechanisms and idealised blast assumptions, meaningful test outcomes rely on appropriate simulated conditions. This paper critically evaluates existing predictive criteria for PBIs (grouped into those affecting the auditory system, pulmonary injuries and brain trauma) as a function of incident blast wave parameters, assuming idealised air blast scenarios. Analysis of the multi-injury criteria reveals new insights and understanding. It showed that blast conditions of relevance to realistic explosive threats are limited and they should be an important consideration in the design of clinical trials simulating blast injury. Zones of relevance for PBI research are proposed to guide experimental designs and compare future data. This work will prove valuable to blast protection engineers and clinical researchers seeking to determine blast loading conditions for safety limits, protective design requirements and injury investigations.

Response of Post-Mortem Human Head Under Primary Blast Loading Conditions: Effect of Blast Overpressures

2013 ◽  
Author(s):  
Shailesh Ganpule ◽  
Robert Salzar ◽  
Namas Chandra
Keyword(s):  
Brain Injury ◽  
Blast Loading ◽  
Human Head ◽  
Severe Injury ◽  
Post Mortem ◽  
Loading Conditions ◽  
Primary Blast ◽  
Blast Overpressure ◽  
Moderate Traumatic Brain Injury ◽  
The Brain

Blast induced neurotrauma (BINT), and posttraumatic stress disorder (PTSD) are identified as the “signature injuries” of recent conflicts in Iraq and Afghanistan. The occurrence of mild to moderate traumatic brain injury (TBI) in blasts is controversial in the medical and scientific communities because the manifesting symptoms occur without visible injuries. Whether the primary blast waves alone can cause TBI is still an open question, and this work is aimed to address this issue. We hypothesize that if a significant level of intracranial pressure (ICP) pulse occurs within the brain parenchyma when the head is subjected to pure primary blast, then blast induced TBI is likely to occur. In order to test this hypothesis, three post mortem human heads are subjected to simulated primary blast loading conditions of varying intensities (70 kPa, 140 kPa and 200 kPa) at the Trauma Mechanics Research Facility (TMRF), University of Nebraska-Lincoln. The specimens are placed inside the 711 mm × 711 mm square shock tube at a section where known profiles of incident primary blast (Friedlander waveform in this case) are obtained. These profiles correspond to specific field conditions (explosive strength and stand-off distance). The specimen is filled with a brain simulant prior to experiments. ICPs, surface pressures, and surface strains are measured at 11 different locations on each post mortem human head. A total of 27 experiments are included in the analysis. Experimental results show that significant levels of ICP occur throughout the brain simulant. The maximum peak ICP is measured at the coup site (nearest to the blast) and gradually decreases towards the countercoup site. When the incident blast intensity is increased, there is a statistically significant increase in the peak ICP and total impulse (p<0.05). Even after five decades of research, the brain injury threshold values for blunt impact cases are based on limited experiments and extensive numerical simulations; these are still evolving for sports-related concussion injuries. Ward in 1980 suggested that no brain injury will occur when the ICP<173 kPa, moderate to severe injury will occur when 173 kPa<ICP<235 kPa and severe injury will occur when ICP>235 kPa for blunt impacts. Based on these criteria, no injury will occur at incident blast overpressure level of 70 kPa, moderate to severe injuries will occur at 140 kPa and severe head injury will occur at the incident blast overpressure intensity of 200 kPa. However, more work is needed to confirm this finding since peak ICP alone may not be sufficient to predict the injury outcome.

scholarly journals In silico investigation of biomechanical response of a human subjected to primary blast

2021 ◽  
Author(s):  
Sunil Sutar ◽  
Shailesh Ganpule
Keyword(s):  
White Matter ◽  
Blast Wave ◽  
Rotational Motion ◽  
Blast Waves ◽  
Primary Blast ◽  
Body Model ◽  
The Past ◽  
Biomechanical Response ◽  
The Brain ◽  
Full Body

The response of the brain to the explosion induced primary blast waves is actively sought. Over the past decade, reasonable progress has been made in the fundamental understanding of bTBI using head surrogates and animal models. Yet, the current understanding of how blast waves interact with the human is in nascent stages, primarily due to lack of data in humans. The biomechanical response in human is critically required so that connection to the aforementioned bTBI models can be faithfully established. Here, using a detailed, full-body human model, we elucidate the biomechanical cascade of the brain under a primary blast. The input to the model is incident overpressure as achieved by specifying charge mass and standoff distance through ConWep. The full-body model allows to holistically probe short- (<5 ms) and long-term (200 ms) brain biomechanical responses. The full-body model has been extensively validated against impact loading in the past. In this work, we validate the head model against blast loading. We also incorporate structural anisotropy of the brain white matter. Blast wave human interaction is modeled using a conventional weapon modeling approach. We demonstrate that the blast wave transmission, linear and rotational motion of the head are dominant pathways for the biomechanical loading of the brain, and these loading paradigms generate distinct biomechanical fields within the brain. Blast transmission and linear motion of the head govern the volumetric response, whereas the rotational motion of the head governs the deviatoric response. We also observe that blast induced head rotation alone produces a diffuse injury pattern in white matter fiber tracts. Lastly, we find that the biomechanical response under blast is comparable to the impact event. These insights will augment laboratory and clinical investigations of bTBI and help devise better blast mitigation strategies.

Design Considerations for Compression Gas Driven Shock Tube to Replicate Field Relevant Primary Blast Condition

2013 ◽  
Author(s):  
Aravind Sundaramurthy ◽  
Raj K. Gupta ◽  
Namas Chandra
Keyword(s):  
Shock Tube ◽  
Blast Wave ◽  
Gaseous Product ◽  
Burst Pressure ◽  
Membrane Thickness ◽  
Time Duration ◽  
Primary Blast ◽  
Blast Overpressure ◽  
Direct Exposure ◽  
Positive Time

Detonation of a high explosive (HE) produces shock-blast wave, noise, shrapnel, and gaseous product; while direct exposure to blast is a concern near the epicenter; shock-blast can affect subjects even at farther distances. The latter is characterized as the primary blast with blast overpressure, time duration, and impulse as shock-blast wave parameters (SWPs). These parameters in turn are a function of the strength of the HE and the distance from the epicenter. It is extremely important to carefully design and operate the shock tube to produce a field relevant SWPs. In this work, we examine the relationship between shock tube adjustable parameters (SAPs) and SWPs to deduce relationship that can be used to control the blast profile and emulate the field conditions. In order to determine these relationships, 30 experiments by varying the membrane thickness, breech length (66.68 to 1209.68 mm) and measurement location was performed. Finally, ConWep was utilized for the comparison of TNT shock-blast profiles with the profiles obtained from shock tube. From these experiments, we observed the following: (a) burst pressure increases with increase in the number of membrane used (membrane thickness) and does not vary significantly with increase in the breech length; (b) within the test section, overpressure and Mach number increases linearly with increase in the burst pressure; however, positive time duration increases with increase in the breech length; (c) near the exit of the shock tube, there is a significant reduction in the positive time duration (PTD) regardless of the breech length.

Shock Tube Design for High Fidelity Blast Wave Simulation

2015 ◽  
Author(s):  
Christopher Ostoich ◽  
Mark Rapo ◽  
Brian Powell ◽  
Humberto Sainz ◽  
Philemon Chan
Keyword(s):  
Shock Tube ◽  
Blast Wave ◽  
Laboratory Data ◽  
Blast Waves ◽  
High Fidelity ◽  
Ongoing Research ◽  
Wave Simulation ◽  
Blast Overpressure ◽  
Blast Exposure ◽  
Significant Pathway

Traumatic brain injury (TBI) has been recognized as the signature wound of the current conflicts and it has been hypothesized that blast overpressure can contribute a significant pathway to TBI. As such, there are many ongoing research efforts to understand the mechanism to blast induced TBI, which all require blast testing using physical and biological surrogates either in the field or in the laboratory. The use of shock tubes to generate blast-like pressure waves in a laboratory can effectively produce the large amounts of data needed for research into blast induced TBI. A combined analytical, computational, and experimental approach was developed to design an advanced shock tube capable of generating high quality out-of-tube blast waves. The selected tube design was fabricated and laboratory tests at various blast wave levels were conducted. Comparisons of tube-generated laboratory data with explosive-generated field data indicated that the shock tube could accurately reproduce blast wave loading on test surrogates. High fidelity blast wave simulation in the laboratory presents an avenue to rapidly and inexpensively generate the large volumes of data necessary to validate and develop theories linking blast exposure to TBI.

scholarly journals Clearing of Blast Waves on Finite-Sized Targets – an Overlooked Approach

2011 ◽  
Vol 82 ◽  
pp. 669-674 ◽  
Author(s):  
Andrew Tyas ◽  
Terry Bennett ◽  
James A. Warren ◽  
Stephen D. Fay ◽  
Sam E. Rigby
Keyword(s):  
Blast Wave ◽  
Experimental Testing ◽  
Experimental Studies ◽  
Blast Loading ◽  
Blast Waves ◽  
Total Impulse ◽  
Cast Doubt ◽  
The Face ◽  
Loading Parameter ◽  
Semi Empirical

The total impulse imparted to a target by an impinging blast wave is a key loading parameter for the design of blast-resistant structures and façades. Simple, semi-empirical approaches for the prediction of blast impulse on a structure are well established and are accurate in cases where the lateral dimensions of the structure are sufficiently large. However, if the lateral dimensions of the target are relatively small in comparison to the length of the incoming blast wave, air flow around the edges of the structure will lead to the propagation of rarefaction or clearing waves across the face of the target, resulting in a premature reduction of load and hence, a reduction in the total impulse imparted to the structure. This effect is well-known; semi-empirical models for the prediction of clearing exist, but several recent numerical and experimental studies have cast doubt on their accuracy and physical basis. In fact, this issue was addressed over half a century ago in a little known technical report at the Sandia Laboratory, USA. This paper presents the basis of this overlooked method along with predictions of the clearing effect. These predictions, which are very simple to incorporate in predictions of blast loading, have been carefully validated by the current authors, by experimental testing and numerical modelling. The paper presents a discussion of the limits of the method, concluding that it is accurate for relatively long stand-off blast loading events, and giving some indication of improvements that are necessary if the method is to be applicable to shorter stand-off cases.

Experimental and Numerical Investigation of Blast Wave Interaction With a Three Level Building

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Jacques Massoni ◽  
Laurent Biamino ◽  
Georges Jourdan ◽  
Ozer Igra ◽  
Lazhar Houas
Keyword(s):  
Shock Tube ◽  
Blast Wave ◽  
Wave Interaction ◽  
Wave Pattern ◽  
Blast Waves ◽  
Building Model ◽  
Experimental Part ◽  
Level Building ◽  
Blast Wave Interaction ◽  
Good Agreement

The present work shows that weak blast waves that are considered as being harmless can turn to become fatal upon their reflections from walls and corners inside a building. In the experimental part, weak blast waves were generated by using an open-end shock tube. A three level building model was placed in vicinity to the open-end of the used shock tube. The evolved wave pattern inside the building rooms was recorded by a sequence of schlieren photographs; also pressure histories were recorded on the rooms' walls. In addition, numerical simulations of the evolved flow field inside the building were conducted. The good agreement obtained between numerical and experimental results shows the potential of the used code for identifying safe and dangerous places inside the building rooms penetrated by the weak blast wave.

Blast Wall Shielding Effectiveness

2017 ◽  
Author(s):  
Jihui Geng ◽  
J. Kelly Thomas
Keyword(s):  
Blast Wave ◽  
High Explosive ◽  
Blast Loading ◽  
Blast Waves ◽  
Shielding Effectiveness ◽  
Wave Shape ◽  
Mitigation Option ◽  
Blast Damage ◽  
Wave Parameters ◽  
Vapor Cloud

Blast walls are frequently considered as a potential mitigation option to reduce the applied blast loading on a building or structure in cases where unacceptably high levels of blast damage are predicted. There are three general explosion types of interest with respect to blast loading: High Explosive (HE), Pressure Vessel Burst (PVB), and Vapor Cloud Explosion (VCE). The blast waves resulting from these explosion types can differ significantly in terms of blast wave shape and duration. The effectiveness of a blast wall depends on these blast wave parameters (shape and duration), as well as the blast wall parameters (e.g., height, width and standoff distance from the protected structure). The effectiveness of a blast wall in terms of mitigating the blast loading on a protected structure depends on the combination of the blast wave and blast wall parameters. However, little guidance is available on the effectiveness of blast walls as a mitigation option for non-HE explosion sources. The purpose of this paper is to characterize the effect of blast wave parameters on the effectiveness of a blast wall and to provide guidance on how to determine whether a blast wall is an effective and practical blast damage mitigation option for a given blast loading.

scholarly journals Analysis of Blast Wave Parameters Depending on Air Mesh Size

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Hrvoje Draganić ◽  
Damir Varevac
Keyword(s):  
Numerical Simulations ◽  
Blast Wave ◽  
Large Scale ◽  
Wave Interaction ◽  
Mesh Size ◽  
Blast Waves ◽  
3D Environment ◽  
Close Range ◽  
Blast Wave Propagation ◽  
Optimal Mesh

Results of numerical simulations of explosion events greatly depend on the mesh size. Since these simulations demand large amounts of processing time, it is necessary to identify an optimal mesh size that will speed up the calculation and give adequate results. To obtain optimal mesh sizes for further large-scale numerical simulations of blast wave interactions with overpasses, mesh size convergence tests were conducted for incident and reflected blast waves for close range bursts (up to 5 m). Ansys Autodyn hydrocode software was used for blast modelling in axisymmetric environment for incident pressures and in a 3D environment for reflected pressures. In the axisymmetric environment only the blast wave propagation through the air was considered, and in 3D environment blast wave interaction and reflection of a rigid surface were considered. Analysis showed that numerical results greatly depend on the mesh size and Richardson extrapolation was used for extrapolating optimal mesh size for considered blast scenarios.

Blast Event Recognition Method for Multisensor Data

2012 ◽  
Author(s):  
Mark Rapo ◽  
Chong Whang ◽  
Philemon Chan
Keyword(s):  
Blast Wave ◽  
Pressure Sensors ◽  
Recognition Algorithm ◽  
Blast Waves ◽  
Event Recognition ◽  
Lookup Table ◽  
Sensor Data ◽  
Upright Posture ◽  
Recirculating Flow ◽  
Blast Overpressure

Due to the great concern that blast overpressure can cause mild traumatic brain injury (mTBI), there is strong interest in putting sensors on warfighters to collect theater data for correlation with medical outcomes. One approach is to mount multiple pressure sensors on the warfighter to measure the blast overpressure environment. An event recognition algorithm that is based on the sensor data recordings is needed to reconstruct the incident blast wave that impacts the warfighter. Blast impingement pressure on an object is highly dependent on the angle of incidence at the point of impact; shadowing and recirculating flow effects can complicate the sensor data pattern. Using computational fluid dynamics (CFD) simulation, the present work demonstrates that for a warfighter in an upright posture in an open blast environment, a three-sensor event recognition algorithm can be developed to reconstruct the incident blast wave (generally characterized as a Friedlander wave). Three-dimensional Navier-Stokes’ based CFD simulations were performed to predict pressure recordings at the three sensor locations for a range of horizontal blast waves impacting the warfighter at all angles of incidence. The predicted peak pressures and durations were recorded and stored in a lookup table. Using an inverse problem approach, it was found that based on the three-sensor data recorded for each event, an algorithm exists for reconstructing the blast incident wave. The established event recognition algorithm is limited to warfighters with upright posture in open blast. Work is being continued to generalize and extend the method to include complex blasts involving multiple reflections and other posture orientations.

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