Blast wave measurements close to explosive charges

Edwards, David Hughes; Thomas, G.O.; Milne, A.; Hooper, G; Tasker, D.G.

doi:10.1007/bf01414759

Cited by 17 publications

(15 citation statements)

References 8 publications

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“…An alternative, developed in 1914 by Bertram Hopkinson, is the apparatus now known as the Hopkinson pressure bar (HPB) [9], consisting of a length of cylindrical bar which propagates an elastic stress pulse along its axis to be recorded by sensitive equipment situated a safe distance from the loaded end. Whilst it is now more commonly used in its 'split' form for high strain-rate material testing [10], the HPB is still a valuable tool for measuring highmagnitude, short-duration loading [11][12][13][14][15][16]. HPBs are used in this study at UoS to record the spatial and temporal distribution of loading acting on a rigid target located close to an explosive.…”

Section: Literature Reviewmentioning

confidence: 99%

Experimental Measurement of Specific Impulse Distribution and Transient Deformation of Plates Subjected to Near-Field Explosive Blasts

et al. 2018

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The shock wave generated from a high explosive detonation can cause significant damage to any objects that it encounters, particularly those objects located close to the source of the explosion. Understanding blast wave development and accurately quantifying its effect on structural systems remains a considerable challenge to the scientific community. This paper presents a comprehensive experimental study into the loading acting on, and subsequent deformation of, targets subjected to nearfield explosive detonations. Two experimental test series were conducted at the University of Sheffield (UoS), UK, and the University of Cape Town (UCT), South Africa, where blast load distributions using Hopkinson pressure bars and dynamic target deflections using digital image correlation were measured respectively. It is shown through conservation of momentum and Hopkinson-Cranz scaling that initial plate velocity profiles are directly proportional to the imparted impulse distribution, and that spatial variations in loading as a result of surface instabilities in the expanding detonation product cloud are significant enough to influence the transient displacement profile of a blast loaded plate.

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Section: Literature Reviewmentioning

confidence: 99%

Experimental Measurement of Specific Impulse Distribution and Transient Deformation of Plates Subjected to Near-Field Explosive Blasts

et al. 2018

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“…[27] and Figure 8(a), one should expect to see gradual particle motion away from the target centre. This behaviour would not have been witnessed in the work by Edwards et al [14] because the analysis was conducted in 1D only. reasons outlined previously, Figure 9(b) shows horizontal velocity-time for the same gauge locations, i.e.…”

Section: Localised Clearingmentioning

confidence: 77%

“…Previous researchers, therefore, have primarily relied on numerical modelling approaches to simulate the detonation, air-shock propagation and shock-structure interaction in the near-field. From these studies, authors have been able to research the complex interaction between the shock wave and expanding detonation products [14], scaled-distance relationships for near-field explosions [15], the limits of representing the explosive as an ideal gas [16], mesh sensitivity effects [17] and the complex 3D waveform of an expanding shock wave [18]. Despite these valuable observations, little definitive, well controlled experimental data is offered to validate such numerical modelling.…”

Section: Introductionmentioning

confidence: 99%

Observations from Preliminary Experiments on Spatial and Temporal Pressure Measurements from Near-Field Free Air Explosions

Rigby

Tyas

Clarke

et al. 2015

International Journal of Protective Structures

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It is self-evident that a crucial step in analysing the performance of protective structures is to be able to accurately quantify the blast load arising from a high explosive detonation. For structures located near to the source of a high explosive detonation, the resulting pressure is extremely high in magnitude and highly non-uniform over the face of the target. There exists very little direct measurement of blast parameters in the nearfield, mainly attributed to the lack of instrumentation sufficiently robust to survive extreme loading events yet sensitive enough to capture salient features of the blast. Instead literature guidance is informed largely by early numerical analyses and parametric studies. Furthermore, the lack of an accurate, reliable data set has prevented subsequent numerical analyses from being validated against experimental trials. This paper presents an experimental methodology that has been developed in part to enable such experimental data to be gathered. The experimental apparatus comprises an array of Hopkinson pressure bars, fitted through holes in a target, with the loaded faces of the bars flush with the target face. Thus, the bars are exposed to the normally or obliquely reflected shocks from the impingement of the blast wave with the target. Pressure-time recordings are presented along with associated Arbitary-Langrangian-Eulerian modelling using the LS-DYNA explicit numerical code. Experimental results are corrected for the effects of dispersion of the propagating waves in the pressure bars, enabling accurate characterisation of the peak pressures and impulses from these loadings. The combined results are used to make comments on the mechanism of the pressure load for very near-field blast events.

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“…The situation is still more complex for reflected blast waves in the nearfield, since the air shock does not simply reflect back into air, but will interact with the still-expanding fireball. Numerical modelling of near-field blast suggests that the waveform [6,7] and magnitudes of some parameters, in particular the peak overpressure [8] may vary from the K&B predictions. However, there has been relatively little definitive experimental work conducted into this issue.…”

Section: Far-field Blastmentioning

confidence: 99%

“…Despite the development of the HPB in the mid C20th to include direct measurements of strain pulses propagating along the bar, it has been used relatively sparingly as a pressure transducer. Edwards et al [6] and Esparza [11] conducted a series of tests on detonations in air, using HPBs as near-field pressure transducers, whilst Lee et al [12] conducted similar work measuring loading from underwater explosions and Fourney and co-workers at University of Maryland have used instrumented HPBs to measure the loading from the detonation of shallow-buried charges [13].…”

Section: Near-field Blastmentioning

confidence: 99%

Experimental Measurement of Pressure Loading from Near-Field Blast Events: Techniques, Findings and Future Challenges

Tyas

2018

The 18th International Conference on Experimental Mechanics

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The accurate characterisation of pressure loads imposed on structural members following the detonation of a high explosive is critical to our ability to design protective systems. This poses serious challenges for experimentalists, due to the high magnitude and short duration of loading. If the distance from the detonation to the target is relatively large, the loading is imparted through the interaction of a shock wave travelling away from the detonation through the surrounding medium, say air. Here, pressure magnitudes are typically in the range 10 3-10 6 Pa and are measurable using conventional, commercially available piezo-electric or piezo-resistive pressure transducers. A considerable effort has been expended on experimentally characterizing these "far-field" loads and consequently, we have a strong understanding of the mechanisms and magnitudes of loading. However, we are also interested in the loading when the target is very close to the detonation, for a range of protection applications, from aviation security to the design of personnel protection. Here, very different physical processes dominate. At these so-called "near-field" distances from a detonation (<~1 m/kgTNT 1/3) the high temperature gaseous detonation products are still violently expanding, and loading on a target is generated by the impingement of both the shocked surrounding material and these products themselves. Blast pressures are often higher that the yield strength of structural materials and temperatures can reach several thousand Kelvin. Furthermore, loading can vary by an order of magnitude over very short distances and timescales. This paper will describe experimental work conducted at University of Sheffield on developing approaches to accurately measure and predict near-field blast loading and gain a better understanding of the underlying mechanisms of loading. The challenges inherent to this field of work will be discussed and an attempt made to identify some of the emerging themes for future research.

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Blast wave measurements close to explosive charges

Cited by 17 publications

References 8 publications

Experimental Measurement of Specific Impulse Distribution and Transient Deformation of Plates Subjected to Near-Field Explosive Blasts

Experimental Measurement of Specific Impulse Distribution and Transient Deformation of Plates Subjected to Near-Field Explosive Blasts

Observations from Preliminary Experiments on Spatial and Temporal Pressure Measurements from Near-Field Free Air Explosions

Experimental Measurement of Pressure Loading from Near-Field Blast Events: Techniques, Findings and Future Challenges

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