Military personnel are exposed to occupational levels of blast overpressure during training. This study characterizes the pressure-time histories of air, underwater, and localized blast, and correlates blast parameters with neuropathology. Blast overpressure was produced by a howitzer, a bazooka, an automatic rifle, underwater explosives, or a shock tube. Anesthetized pigs were exposed in positions that simulated real training scenarios. Underwater exposures were performed using explosives at distances recommended by safety requirements. In other experiments, rats were exposed via a shock tube. The pressure changes were recorded with a hydrophone sensor in the brain of the pig and in rats with an optical fiber sensor. Histological examination of porcine brains revealed small parenchymal and subarachnoid hemorrhages, predominately in the occipital lobe, cerebellum, and medulla oblongata. Relative to the peak pressure in air, that in porcine brain (Pmax brain/air) was 0.7 for the bazooka and 0.5 and 0.7, respectively, for the 9- and 30-kPa howitzer. The attenuation was stronger in water: the detonation pulse had a brain/water ratio of 0.1, and the secondary pulses had ratios of 0.3-0.4. The results indicate that low-frequency spectra penetrate easily from air or water into the brain, but high-frequency spectra appear to be filtered by body structures. In addition, blast waves were recorded in the brain and abdomen of pigs after local exposure via shock tube to either the abdomen or the top of the skull. When the abdomen was exposed, the maximal peak value in the brain was only 3% of that in the abdomen. Moreover, part of this pressure could have been derived from the air outside the head. The results gave little support to significant transmission of pressure within the body.

This paper focuses on the mathematical modelling required to support the development of new primary standard systems for traceable calibration of dynamic pressure sensors. We address two fundamentally different approaches to realising primary standards, specifically the shock tube method and the drop-weight method. Focusing on the shock tube method, the paper presents first results of system identification and discusses future experimental work that is required to improve the mathematical and statistical models. We use simulations to identify differences between the shock tube and drop-weight methods, to investigate sources of uncertainty in the system identification process and to assist experimentalists in designing the required measuring systems. We demonstrate the identification method on experimental results and draw conclusions.

Within the Euromet region a regional key comparison (Euromet.M.P-K1.b) was carried out in order to compare national vacuum standards in the pressure range from 3 × 10-4 Pa to 0.9 Pa. The participants were the BNM-LNE (France), CEM (Spain), IMGC-CNR (Italy), IMT (Slovenia), NPL (United Kingdom), UME (Turkey), and the PTB (Germany) as pilot laboratory. The measurements were carried out from April 2000 to February 2002.Two spinning rotor gauges served as transfer standards and showed a good transport stability. The effective accommodation coefficients of the rotors had to be determined at eight target points at and between 3 × 10-4 Pa and 0.9 Pa. The uncertainty of the generated pressure in the calibration standard was reported as part of the calibration report by each laboratory. All additional uncertainties that were related to the transfer standard were evaluated by the pilot laboratory in order to have a uniform uncertainty analysis for all participants and in order to emphasize the importance of the reported uncertainty of the generated pressure.From the available data a Euromet reference value was calculated at each target pressure. The results from most of the laboratories showed a good agreement with the reference value within the combined uncertainties. A few values of three of the laboratories were significantly off the reference value.At the highest target pressure of 0.9 Pa a linkage to the lowest target pressure at 1 Pa of the key comparison CCM.P-K4 was possible by means of the results of three laboratories that took part in both comparisons.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the Mutual Recognition Arrangement (MRA).

Measurements of mechanical quantities such as pressure often take place under dynamic conditions, yet no traceable standards for the primary dynamic calibration of pressure sensors currently exist. In theory, shock tubes can provide a close to perfect step-function ideal for the calibration of pressure transducers. In this paper we investigate a system consisting of a shock tube and an ultra-fast fiber-optical sensor that is designed to be a future primary system for dynamic pressure calibrations. For reference, the fiber-optical sensor is compared to a piezoelectric sensor, and their corresponding frequency spectra are calculated. Furthermore, an investigation of the repeatability of the fiber-optical sensor, as well as a comparison with a second shock tube, is performed.

An optical method for measuring the gas density by monitoring the refractive index inside a high-finesse Fabry–Perot cavity is presented. The frequency of a narrow linewidth Er:fiber laser, locked to a mode of the cavity, is measured with the help of an optical frequency comb while the gas density inside the cavity changes. A resolution of 1.4 × 10−6 mol m−3 is achieved in 3 s for nitrogen, which allows measurement of a relative gas density change of 3.4 × 10−8 at atmospheric pressure.

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Accurate dynamic pressure measurements are increasingly important. While traceability is lacking, several National Metrology Institutes (NMIs) and calibration laboratories are currently establishing calibration capacities. Shock tubes generating pressure steps with rise times below 1 µs are highly suitable as standards for dynamic pressures in gas. In this work, we present the results from applying a fast-opening valve (FOV) to a shock tube designed for dynamic pressure measurements. We compare the performance of the shock tube when operated with conventional single and double diaphragms and when operated using an FOV. Different aspects are addressed: shock-wave formation, repeatability in amplitude of the realized pressure steps, the assessment of the required driver pressure for realizing nominal pressure steps, and economy. The results show that using the FOV has many advantages compared to the diaphragm: better repeatability, eight times faster to operate, and enables automation of the test sequences.

Blast-induced traumatic brain injury caused by road bombs has lately become a larger part of allied injuries. The same mechanisms may also be responsible for milder injuries of similar nature, resulting from training with large caliber weapons and explosives. In this paper, the blast effects from a weapon on the brain are investigated. Using the hydrocode AUTODYN, numerical simulations of shock wave propagation into the brain are performed. The shock wave is calculated from a complete numerical simulation of the weapon, including the burning gun powder gas inside the barrel, acceleration of the projectile, and the rapid gas flow out of the muzzle. An idealized head is placed in the simulation at the position of personnel firing the weapon. Here we focus on the qualitative mechanisms of the propagation of the shock wave through the skull and into the brain. The results are compared with experiments carried out on anesthetized animals. To simulate real training scenarios, pigs were placed in position of personnel and exposed to impulse noise generated from weapons. Blast parameters in the air were correlated with those in the brain.