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Blast Testing Issues and TBI: Experimental Models That Lead to Wrong Conclusions.

Needham CE, Ritzel D, Rule GT, Wiri S, Young L - Front Neurol (2015)

Bottom Line: This basic understanding must include the differences and interrelationships of static pressure, dynamic pressure, reflected pressure, and total or stagnation pressure in transient shockwave flows, how they relate to loading of objects, and how they are properly measured.This paper provides guidance regarding proper experimental methods and offers insights into the implications of improperly designed and executed tests.Through application of computational methods, useful data can be extracted from well-documented historical tests, and future work can be conducted in a way to maximize the effectiveness and use of valuable biological test data.

View Article: PubMed Central - PubMed

Affiliation: Southwest Division, Applied Research Associates, Inc. , Albuquerque, NM , USA.

ABSTRACT
Over the past several years, we have noticed an increase in the number of blast injury studies published in peer-reviewed biomedical journals that have utilized improperly conceived experiments. Data from these studies will lead to false conclusions and more confusion than advancement in the understanding of blast injury, particularly blast neurotrauma. Computational methods to properly characterize the blast environment have been available for decades. These methods, combined with a basic understanding of blast wave phenomena, enable researchers to extract useful information from well-documented experiments. This basic understanding must include the differences and interrelationships of static pressure, dynamic pressure, reflected pressure, and total or stagnation pressure in transient shockwave flows, how they relate to loading of objects, and how they are properly measured. However, it is critical that the research community effectively overcomes the confusion that has been compounded by a misunderstanding of the differences between the loading produced by a free field explosive blast and loading produced by a conventional shock tube. The principles of blast scaling have been well established for decades and when properly applied will do much to repair these problems. This paper provides guidance regarding proper experimental methods and offers insights into the implications of improperly designed and executed tests. Through application of computational methods, useful data can be extracted from well-documented historical tests, and future work can be conducted in a way to maximize the effectiveness and use of valuable biological test data.

No MeSH data available.


Related in: MedlinePlus

Free field, conical, and exit jet load waveform comparisons (6).
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Figure 2: Free field, conical, and exit jet load waveform comparisons (6).

Mentions: The three waveforms in Figure 2 compare the incident and load pressures on similar targets. In all cases, the incident overpressure is just over 100 kPa and a target duration of about 4 ms. The conical tube does a reasonable job of duplicating the free field environment, but has introduced some secondary shocks. The experiment with the head in the exit jet shows significant deviations from the free field case. The load on the front of the helmet remains high for a time of more than twice the incident duration of the free field case resulting in an artificially enhanced impulse exposure. This is caused by a combination of area blockage and the greatly enhanced dynamic pressure in the “exit jet.” The pressures on the crown (top) and rear of the helmet are reduced, with a shortened positive duration and a long negative phase (6). Such a pressure distribution leads to great overestimations of the total forces and impulses delivered to the target. A surprising number of papers presented in biomedical journals employ end-jet testing exacerbated by high-blockage.


Blast Testing Issues and TBI: Experimental Models That Lead to Wrong Conclusions.

Needham CE, Ritzel D, Rule GT, Wiri S, Young L - Front Neurol (2015)

Free field, conical, and exit jet load waveform comparisons (6).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4389725&req=5

Figure 2: Free field, conical, and exit jet load waveform comparisons (6).
Mentions: The three waveforms in Figure 2 compare the incident and load pressures on similar targets. In all cases, the incident overpressure is just over 100 kPa and a target duration of about 4 ms. The conical tube does a reasonable job of duplicating the free field environment, but has introduced some secondary shocks. The experiment with the head in the exit jet shows significant deviations from the free field case. The load on the front of the helmet remains high for a time of more than twice the incident duration of the free field case resulting in an artificially enhanced impulse exposure. This is caused by a combination of area blockage and the greatly enhanced dynamic pressure in the “exit jet.” The pressures on the crown (top) and rear of the helmet are reduced, with a shortened positive duration and a long negative phase (6). Such a pressure distribution leads to great overestimations of the total forces and impulses delivered to the target. A surprising number of papers presented in biomedical journals employ end-jet testing exacerbated by high-blockage.

Bottom Line: This basic understanding must include the differences and interrelationships of static pressure, dynamic pressure, reflected pressure, and total or stagnation pressure in transient shockwave flows, how they relate to loading of objects, and how they are properly measured.This paper provides guidance regarding proper experimental methods and offers insights into the implications of improperly designed and executed tests.Through application of computational methods, useful data can be extracted from well-documented historical tests, and future work can be conducted in a way to maximize the effectiveness and use of valuable biological test data.

View Article: PubMed Central - PubMed

Affiliation: Southwest Division, Applied Research Associates, Inc. , Albuquerque, NM , USA.

ABSTRACT
Over the past several years, we have noticed an increase in the number of blast injury studies published in peer-reviewed biomedical journals that have utilized improperly conceived experiments. Data from these studies will lead to false conclusions and more confusion than advancement in the understanding of blast injury, particularly blast neurotrauma. Computational methods to properly characterize the blast environment have been available for decades. These methods, combined with a basic understanding of blast wave phenomena, enable researchers to extract useful information from well-documented experiments. This basic understanding must include the differences and interrelationships of static pressure, dynamic pressure, reflected pressure, and total or stagnation pressure in transient shockwave flows, how they relate to loading of objects, and how they are properly measured. However, it is critical that the research community effectively overcomes the confusion that has been compounded by a misunderstanding of the differences between the loading produced by a free field explosive blast and loading produced by a conventional shock tube. The principles of blast scaling have been well established for decades and when properly applied will do much to repair these problems. This paper provides guidance regarding proper experimental methods and offers insights into the implications of improperly designed and executed tests. Through application of computational methods, useful data can be extracted from well-documented historical tests, and future work can be conducted in a way to maximize the effectiveness and use of valuable biological test data.

No MeSH data available.


Related in: MedlinePlus