Dynamic loads on human and animal surrogates at different test locations in compressed-gas-driven shock tubes

Alay, Eren; Skotak, Maciej; Misistia, Anthony; Chandra, Namas

doi:10.1007/s00193-017-0762-4

Cited by 22 publications

(21 citation statements)

References 27 publications

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“…Animal models tested inside experience a higher level of loading caused by static pressure, simply because higher peak overpressures and durations can be achieved inside when compared with the outside. This difference is demonstrated in reported durations in the published literature where unlike inside the shock tube, overpressure durations longer than 2 ms have not been reported outside of the shock tube ( 18 – 22 ). Furthermore, acceleration of the rodent head, and body caused by dynamic pressure (jet effect) of expanding shock wave (classified as tertiary blast injury) are characterized by increased level of injury compared with primary blast TBI ( 23 ).…”

Section: Introductionmentioning

confidence: 79%

On the Accurate Determination of Shock Wave Time-Pressure Profile in the Experimental Models of Blast-Induced Neurotrauma

2018

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Measurement issues leading to the acquisition of artifact-free shock wave pressure-time profiles are discussed. We address the importance of in-house sensor calibration and data acquisition sampling rate. Sensor calibration takes into account possible differences between calibration methodology in a manufacturing facility, and those used in the specific laboratory. We found in-house calibration factors of brand new sensors differ by less than 10% from their manufacturer supplied data. Larger differences were noticeable for sensors that have been used for hundreds of experiments and were as high as 30% for sensors close to the end of their useful lifetime. These observations were despite the fact that typical overpressures in our experiments do not exceed 50 psi for sensors that are rated at 1,000 psi maximum pressure. We demonstrate that sampling rate of 1,000 kHz is necessary to capture the correct rise time values, but there were no statistically significant differences between peak overpressure and impulse values for low-intensity shock waves (Mach number <2) at lower rates. We discuss two sources of experimental errors originating from mechanical vibration and electromagnetic interference on the quality of a waveform recorded using state-of-the-art high-frequency pressure sensors. The implementation of preventive measures, pressure acquisition artifacts, and data interpretation with examples, are provided in this paper that will help the community at large to avoid these mistakes. In order to facilitate inter-laboratory data comparison, common reporting standards should be developed by the blast TBI research community. We noticed the majority of published literature on the subject limits reporting to peak overpressure; with much less attention directed toward other important parameters, i.e., duration, impulse, and dynamic pressure. These parameters should be included as a mandatory requirement in publications so the results can be properly compared with others.

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Section: Introductionmentioning

confidence: 79%

On the Accurate Determination of Shock Wave Time-Pressure Profile in the Experimental Models of Blast-Induced Neurotrauma

2018

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“…In the early days, the experimental were frequently performed on the outside or at the end of the shock tube [ 6 , 7 , 19 , 33 ]. This approach while not without some merit is a convenience-driven rather than rational design to replicate true field conditions [ 34 , 35 ], with a possibility of the significant contribution of dynamic loading [ 36 ]. The testing of the specimen with the dimensions of the human head requires a broad cross-section shock tube to be employed, which otherwise would result in the pressure artifacts associated with the blockage [ 36 ].…”

Section: Discussionmentioning

confidence: 99%

Effective testing of personal protective equipment in blast loading conditions in shock tube: Comparison of three different testing locations

et al. 2018

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We exposed a headform instrumented with 10 pressure sensors mounted flush with the surface to a shock wave with three nominal intensities: 70, 140 and 210 kPa. The headform was mounted on a Hybrid III neck, in a rigid configuration to eliminate motion and associated pressure variations. We evaluated the effect of the test location by placing the headform inside, at the end and outside of the shock tube. The shock wave intensity gradually decreases the further it travels in the shock tube and the end effect degrades shock wave characteristics, which makes comparison of the results obtained at three locations a difficult task. To resolve these issues, we developed a simple strategy of data reduction: the respective pressure parameters recorded by headform sensors were divided by their equivalents associated with the incident shock wave. As a result, we obtained a comprehensive set of non-dimensional parameters. These non-dimensional parameters (or amplification factors) allow for direct comparison of pressure waveform characteristic parameters generated by a range of incident shock waves differing in intensity and for the headform located in different locations. Using this approach, we found a correlation function which allows prediction of the peak pressure on the headform that depends only on the peak pressure of the incident shock wave (for specific sensor location on the headform), and itis independent on the headform location. We also found a similar relationship for the rise time. However, for the duration and impulse, comparable correlation functions do not exist. These findings using a headform with simplified geometry are baseline values and address a need for the development of standardized parameters for the evaluation of personal protective equipment (PPE) under shock wave loading.

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“…The 7 m long square (0.71 × 0.71 m) cross section shock tube was used in all experiments. This device was previously characterized in detail [24,26]. The driver gas was compressed helium (ultra-high purity, 99.99%, Airgas, Oakland, NJ), which was allowed to flow into the breech separated from the driven section of the shock tube with membranes made of Mylar (Grafix, Cleveland, OH).…”

Section: The Shock Tubementioning

confidence: 99%

“…It's been demonstrated that head acceleration might lead to the development of tertiary blast injuries, which have different injury characteristics than those resulting from shock wave loading [22,23]. The importance of the test location in the shock tube was a subject of the experimental evaluation in the past by our group [24][25][26]. These results illustrate significant differences between testing the specimen inside of the shock tube, i.e., at the distance from the exit enough to eliminate influence of any end-effects, versus at the end and outside.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Geometrical Factors on the Surface Pressure Distribution on a Human Phantom Model Following Shock Exposure: A Computational and Experimental Study

Skotak¹,

Townsend²,

Alay³

et al. 2020

Fracture Mechanics Applications

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Experimental data and finite element simulations of an anthropometric surrogate headform was used to evaluate the effect of specimen location and orientation on surface pressures following shock exposures of varying intensity. It was found that surface pressure distributions changed with local flow field disturbances, making it necessary to use data reduction strategies to facilitate comparisons between test locations, shock wave intensities and headform orientations. Non-dimensional parameters, termed amplification factors, were developed to permit direct comparisons of pressure waveform characteristics between incident shock waves differing in intensity, irrespective of headform location and orientation. This approach proved to be a sensitive metric, highlighting the flow field disturbances which exist in different locations and indicating how geometric factors strongly influence the flow field and surface pressure distribution.

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Dynamic loads on human and animal surrogates at different test locations in compressed-gas-driven shock tubes

Cited by 22 publications

References 27 publications

On the Accurate Determination of Shock Wave Time-Pressure Profile in the Experimental Models of Blast-Induced Neurotrauma

On the Accurate Determination of Shock Wave Time-Pressure Profile in the Experimental Models of Blast-Induced Neurotrauma

Effective testing of personal protective equipment in blast loading conditions in shock tube: Comparison of three different testing locations

The Effect of Geometrical Factors on the Surface Pressure Distribution on a Human Phantom Model Following Shock Exposure: A Computational and Experimental Study

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