Manganin Gauges Research Articles

Effects of encapsulation of manganin gauges on the pressure profiles from shock initiation experiments

AbstractThe Lagrangian test can measure the shock initiation process of explosives for different incident shock pressures. The manganin gauges record pressure histories for several DNAN‐based melt‐cast explosives. The encapsulation of the gauges results in three types of characteristic signals: (1) a step signal on the low‐pressure shock front, (2) a flatten Von Neuman's (VN's) spike on the high‐pressure shock front, and (3) a V‐shape signal behind the shock front. To reveal the mechanism underlying these characteristic signals, a one‐dimensional Lagrangian hydrocode, was used to simulate the propagation of a sustained shock in both ideal and non‐ideal systems. The simulation results show that the impedance mismatch between encapsulation material and explosives is the main reason for the three characteristic signals. The calibration of shock initiation model should take the encapsulation material into account so as to determine shock initiation model parameters accurately.

Capacitive Effect and Electromagnetic Coupling on Manganin Gauge Limiting the Bandwidth for Pressure Measurements under Shock Conditions.

In this study, we investigated the capacitive effect and the electromagnetic coupling on the measurement chain induced by impact experiments with a gas gun or powder gun. Reduced bandwidth and noise were noticed on experimental signals. Rogowski coil measurements were added on the cables to characterize the electromagnetic coupling. The perturbation currents on the cables were quantified depending on the configuration. The gauge, the transmission line and the conditioning system were modeled. The calculations reproduced the electrical wave arrival time, the transmission line transfer impedance and the conditioning system transfer impedance; and the bandwidth limitation has been displayed. A capacitive effect with the piezoresistive manganin gauge embedded into the sample was identified, depending on the experimental setup.

Shock Initiation Experiments with Modeling on a DNAN Based Melt-Cast Insensitive Explosive

2,4-dinitroanisole (DNAN) is a good replacement for 2,4,6-trinitrotoluene (TNT) in melt-cast explosives due to its superior insensitivity. With the increasing use of DNAN-based melt-cast explosives, the prediction of reaction violence and hazard assessment of the explosives subjected to shock is of great significance. This study investigated the shock initiation characteristics for a DNAN-based melt-cast explosive, DHFA, using the one-dimensional Lagrangian apparatus. The embedded manganin gauges in the apparatus record the pressure histories at four Lagrangian positions and show that shock-to-detonation transition in DHFA needs a high input shock pressure. The experimental data are analyzed to calibrate the Ignition and Growth model. The calibration is performed using an objective function based on both pressure history and the arrival time of shock. Good agreement between experimental and calculated pressure histories indicates the high accuracy of the calibrated parameters with the optimization method.

Hugoniot and dynamic strength in polyurea

Polyurea is of interest for blast mitigation of structures, which requires a good understanding of the dynamic properties including the shock Hugoniot and dynamic spall and shear strength. In this study, reverse impact experiments were used to determine the shock Hugoniot, direct impact experiments were used to determine the spall strength, and lateral manganin gauge experiments were used to determine the dynamic shear strength. Reverse impact experiments revealed that the Hugoniot has a linear fit at low pressures and appears to be undergoing a reaction at higher pressures. The spall strength experiments in this study in combination with the literature data showed that the spall strength increases as a function of pressure, which is unusual in polymers and may be attributed to polyurea transforming to a glassy phase. In the shear strength experiments, the shear stress was shown to increase with increasing longitudinal stress in polyurea, similar to estane, another elastomer.

Understanding Calibration and Error Propagation in Longitudinal and Lateral Manganin Gauge Shock Experiments

Soda-lime glass remains elastic under shock pressures up to approximately 6.5 GPa. In this paper, soda lime glass shock experiments are used to understand the calibration and error propagation in longitudinal and lateral manganin gauge experiments. The errors in the calibration process for both longitudinal and lateral manganin gauge experiments are identified and discussed. Five soda-lime glass experiments up to 3 GPa are analyzed using this refined technique. The results show good agreement between the experimental data and the published calibration by Rosenberg and Moshel. Errors are propagated from the experimental data measurements and the assumptions that are made in the calibration, where the bulk of the error seems to come from uncertainty in the dynamic yield strength of manganin. The method presented in this paper allows for analysis of dynamic shock experiments with longitudinal and lateral manganin gauges including error propagation.

Embedded Manganin Gauge Measurements and Modeling of Shock Initiation in HMX‐Based PBX Explosives with Different Particle Sizes and Porosities

AbstractA series of shock initiation experiments on the explosive PBXC03 (87 % HMX, 7 % TATB, and 6 % Viton by weight) with different particle sizes and porosities under various shock loadings have been performed, and it is found that the particle size and the porosity of the explosives have much influence on the shock initiation characteristics. That is, the smaller the particle size, the more difficult the explosive to be ignited but the faster the detonation grows once the explosive is ignited. It is also found that the detonation grows the fastest in the explosive with moderate porosity. Moreover, a modified mesoscopic reaction rate model based on the experimental results and the pore collapse hot‐spot ignition mechanism is developed, which allows for a separate reaction mechanism evaluation at different reaction stages for the shock initiation and detonation growth processes in the explosives. The calculated pressure‐time histories and Pop‐Plots for PBXC03 are founded to be all in good agreement with the experimental data. The modified mesoscopic reaction rate model shows its potentiality for quantitatively predicting the effects of the mesostructure of PBXs on the shock initiation and detonation growth processes with a high degree of confidence.

The Dynamic Response of Dense 3 Dimensionally Printed Polylactic Acid

Polylactic acid (PLA) is commonly used as a feedstock material for commercial 3D printing. As components manufactured from such material become more commonplace, it is inevitable that some of the resultant systems will be exposed to high strain-rate/impact events during their design-life (for example, components being dropped or even involved in a high-speed crash). To this end, understanding the shock properties of polylactic acid, in its role as a major raw material for 3D printed components, is of particular importance. In this work, printed samples of PLA were deformed by one-dimensional shock waves generated via the plate impact technique, allowing determination of both the Hugoniot Equation of State (EOS) and shear strength of the material. Both linear and non-linear EOS forms were considered in the US-Up plane, with the best-fit found to take the general form U_{S} = 1.28 + 3.06 - 1.09U_{p}^{2} in the U_{s} {-}U_{p} plane, consistent with other polymers. Use of lateral Manganin gauges embedded in the material flow allowed consideration of lateral stress evolution at impact pressures ranging from 0.3 to 4.0 GPa. Shear strength was observed to increase with impact stress, however, with minimal strengthening behind the shock front. Deviation of the measured stress from the predicted elastic measurement (corresponding to the PLA’s Hugoniot Elastic Limit) was observed at longitudinal stress of 0.90 ± 0.05 GPa, within range of polymeric materials of similar characteristics—the first time this important parameter has been measured for PLA. As a result, this material characterisation will allow numerical modellers to accurately predict the structural response of PLA-based components/structures against high strain rates such as impacts or drops.

Measurement of shock pressure and shock-wave attenuation near a blast hole in rock

The objective of this study was to investigate granite responses to blasting. The focus was on the pressure and attenuation of shock waves in granite. Tests are reported on ten cylinders subjected to explosions from central pressed trinitrotoluene (TNT) charges with approximate density of 1.6 g/cm3. Three cylinders had dimensions Ø150 mm × 200 mm; seven, Ø240 mm × 300 mm. Specimens had concentric holes drilled from both ends: one 20-mm hole to position the explosive charge and one 50-mm hole to insert a granite plug equipped with Manganin gauges, which were applied to monitor the pressures of the shock waves. The configuration of the gauges was analyzed before testing to investigate how precisely they could measure shock waves in the granite. One or two gauges were used in each cylinder at distances of 7, 15, 22 or 35 mm from the explosive charge in the cylinder axis. At detonation of the charge, the measured peak pressure values ranged from 15.9–4.4 GPa depending on distance from the explosive, with pressure rise times of ∼0.5 μs. In one specimen, deflagration occurred, resulting in a low peak pressure of 1.35 GPa 11 mm from the explosive and a 16-μs pressure rise time. For specimens with two gauges, shock-wave velocities were found to depend strongly on the distance from the explosive. Fitting a curve to the experimental data, an exponential relation for the shock-wave peak pressure and its attenuation was obtained, expressing pressure (GPa) as a function of increasing distance (mm) from the explosive: p=19.4exp(−0.04x). The findings, especially regarding the damping term, may for instance be useful for verification of numerical models for blasting simulation.

A Manganin Thin Film Ultra-High Pressure Sensor for Microscale Detonation Pressure Measurement.

With the development of energetic materials (EMs) and microelectromechanical systems (MEMS) initiating explosive devices, the measurement of detonation pressure generated by EMs in the microscale has become a pressing need. This paper develops a manganin thin film ultra-high pressure sensor based on MEMS technology for measuring the output pressure from micro-detonator. A reliable coefficient is proposed for designing the sensor’s sensitive element better. The sensor employs sandwich structure: the substrate uses a 0.5 mm thick alumina ceramic, the manganin sensitive element with a size of 0.2 mm × 0.1 mm × 2 μm and copper electrodes of 2 μm thick are sputtered sequentially on the substrate, and a 25 μm thick insulating layer of polyimide is wrapped on the sensitive element. The static test shows that the piezoresistive coefficient of manganin thin film is 0.0125 GPa−1. The dynamic experiment indicates that the detonation pressure of micro-detonator is 12.66 GPa, and the response time of the sensor is 37 ns. In a word, the sensor developed in this study is suitable for measuring ultra-high pressure in microscale and has a shorter response time than that of foil-like manganin gauges. Simultaneously, this study could be beneficial to research on ultra-high-pressure sensors with smaller size.

Determination of Hugoniot Elastic Limit (HEL) and Equation of State (EOS) of Ceramic Materials in the Pressure Region 20 GPa to 100 GPa

The light weight ceramics materials like silicon carbide, boron carbide and alumina have major application in vehicle armour and tank amours due to their low density and high compressive strength properties. The mechanical response of these ceramic materials has been investigated using explosive driven plate impact method. In present studies, hugoniot elastic limit (HEL) from pressure-time profile using manganin gauge and shock EOS in the pressure region 20 GPa to 100 GPaof boron carbide, silicon carbide and alumina were determined. In manganin gauge trace, the delayed failure observed also during shock loading.

Shock Response of Polymethylmethacrylate

Polymethylmethacrylate (PMMA) from two suppliers is subjected to shock loading up to 2 GPa to develop understanding of the effect of manufacturing process on the shock response. The particle velocity, shock velocity, and longitudinal and lateral stresses are measured simultaneously and independently using photon Doppler velocimetry and manganin gauges. The particle velocity measurements agree with data in the literature. The calculated shear stress was seen to deviate from linear behavior at approximately 2 GPa, which is consistent with other experiments. Overall, the selection of material is shown to have up to a 10 % effect on shock properties, but the average difference is less than 2 %, which indicates that the varying the PMMA supplier may not have a dramatic effect on test using PMMA as a window or gap material.

Dynamic Properties of RHA Steel under Planar Shock Loading using Explosive Driven Plate Impact System

Planar shock loading of rolled homogeneous armour (RHA) steel has been studied at high pressures in the range of 20-100 GPa using an explosive-driven plate impact system. Shock velocities and flyer velocities are measured using time of arrival pins embedded in the target at known depths. The shock equation of state of RHA steel has been determined. α → e phase transition stress and hugoniot elastic limit (HEL) of RHA steel have been determined through manganin gauge and found to be 12.2 ±0.6 GPa and 4.1 ± 0.2 GPa, respectively. The experimental stress of phase transition has been compared with the stress calculated using ThermoCalc software. The shock properties have been incorporated in the Autodyn simulation package and simulations were performed to determine flyer velocity, pressures and the results are compared with that of experiments. Defence Science Journal, Vol. 65, No. 3, May 2015, pp.196-202, DOI: http://dx.doi.org/10.14429/dsj.65.7952

A new approach for Hugoniot equation of state of polycarbonate

The plate impact experiment is an important way to measure the equation of state of solid material in high pressure. However, traditional methods always have some defects, such as high failure rate, indefinite and inaccurate result in the test, and lack of comparison. Meanwhile, few of published data concerned the high strain rate behavior of polycarbonate during shock loading. In the present study, a new approach was therefore carried out to obtain the equation of state of polycarbonate material in a single-stage gas gun, which consists of asymmetric impact technology, manganin gauges, PVDF, electromagnetic particle velocity gauges and electrical pins. The least square method was used to analyze the fitting goodness and scatter degree of the single and the combined method respectively. The results showed that manganin gauges have the best property of stability, followed by particle velocity gauges, PVDF gauges and electrical pins. Compared with other single method, the combined method can improve the accuracy of measurement in a relatively less number of experiments than previous data. At last, the D−u Hugoniot curve of polycarbonate in high pressure was gained, and the manganin gauges were calibrated by the experimental data.

Phase transitions in shock-loaded titanium at pressures up to 150 GPa

Phase transformations in VT1-0 titanium were studied. Shock profiles in the pressure range of 10–26 GPa were recorded by polyvinylidene fluoride sensors. Sound velocities in shock-compressed titanium samples were measured by two methods. At a pressure less than 30 GPa, the speed of sound in titanium was determined by the counter unloading method using Manganin gauges, and at a pressure of 30–150 GPa, it was determined by the overtaking unloading method using indicator liquids. At a pressure of 20–40 and 60–90 GPa, the pressure dependences of the speed of sound have breaks, the first of which is apparently associated with the α → ω conversion, and the second with melting. X-ray analysis revealed the presence of the ω phase in the samples in steel capsules recovered after loading at a pressure of 9–23 GPa. The dependence of the yield of the ω phase on the loading pressure has the form of a curve with a maximum at p ≈ 15 GPa.

Revisiting the calibration of manganin gauges for lateral stress measurements in shock-loaded solids

The calibration of manganin gauges for lateral stress measurements, in shock loaded specimens, is revisited through a simplified analysis, which is based on the dependence of the gauge's strength on shock amplitude. This dependence is derived from the measured resistive hysteresis of the gauge, as obtained in shock and release experiments. The resulting values for the gauge's strength, as a function of shock amplitude, are about half the values which were obtained previously by a different analysis. With the revised strength values, a new calibration curve is derived for the commercial grid-like gauges, as lateral stress transducers in planar impact experiments.

Polymorphic transformations in nanostructured anatase (TiO2) under high-pressure shock compression

The action of dynamic pressure and temperature on polymorphic transformations in nanostructured (grain size of 8–20 nm) anatase (TiO2) is studied. The dynamic pressure of a loading pulse (10–45 GPa) is measured with a manganin gauge. The temperature of shock-compressed specimens, which is varied by varying the initial temperature and initial porosity, is found to fall into the range 500–2500 K. It is shown that as the temperature and shock compression pressure rise, the nanostructured anatase turns into a nanoanatase-nanocolumbite or columbite-rutile mixture or into almost impurity-free (pure) nanocolumbite or impurity-free microcrystalline rutile.

Studies on Shock Attenuation in Plastic Materials and Applications in Detonation Wave Shaping

Pressure in plastic materials attenuates due to change of impedance, phase change in the medium and plastic deformation. A lot of theoretical and experimental efforts have been devoted to the attenuation of shock wave produced by the impact of explosive driven flyer plate. However comparatively less work has been done on the attenuation of shock waves due to contact explosive detonation. Present studies deal with the attenuation of explosive driven shock waves in various plastic materials and its applications in design of Hybrid Detonation Wave Generator In present work shock attenuating properties of different polymers such as Perspex, Teflon, nylon, polypropylene and viton has been studied experimentally using rotating mirror streak camera and electrical position pins. High explosive RDX/TNT and OCTOL of diameter 75-100mm and thickness 20 to 50mm were detonated to induce shock wave in the test specimens. From experimental determined shock velocity at different locations the attenuation in shock pressure was calculated. The attenuation of shock velocity with thickness in the material indicates exponential decay according to relation US = UOexp(-ax). In few of the experiments manganin gauge of resistance 50 ohms was used to record stress time profile across shock wave. The shock attenuation data of Viton has successfully been used in the design of hybrid detonation wave generator using Octol as high explosive. While selecting a material it was ensured that the attenuated shock remains strong enough to initiate an acceptor explosive. Theoretical calculation were supported by Autodyne 2D hydro-code simulation which were validated with the experiments conducted using high speed streak photography and electrical shock arrival pins. Shock attenuation data of Perspex was used to establishing card gap test and wedge test in which test items is subjected to known pressure pulse by selecting the thickness of the plastic material.

Study on the mechanical behavior of steel reinforced high strength concrete subjected to impact loading

In this paper, the impact experiments of steel fiber reinforced concrete with same impact velocity and different steel fiber contents are processed by one-stage light gas gun. Through the manganin gauges embedded in the target, the voltage-time signals are recorded. Lagrangian method is used to analyze the flow field, then the particle velocity (u), specific energy, specific volume with time are obtained. Moreover, it was observed from the measured pressure-time curves that the decay factor is smaller in the steel reinforced high strength concrete. The dynamic response is analyzed. Key words: Concrete, relationship, steel fiber.

Foil-like manganin gauges for dynamic high pressure measurements

Foil-like manganin gauges with a variety of shapes used in different ranges of pressure for the one-dimensional strain mode and axisymmetric strain mode were designed for measuring the detonation pressures of explosives and high shock pressure in materials. In the stress range of 0–53.5 GPa, the pressure–piezoresistance relationships of the manganin gauges were calibrated by the light gas gun and the planar lens of explosive. The piezoresistance coefficients were obtained in different ranges of pressure. To verify the coefficients, the detonation pressure (CJ pressure) of TNT explosive was measured by the manganin gauges, which give similar CJ pressure values to those reported by Zhang et al (2009 Detonation Physics (Beijing: Ordnance Industry Press)) with the maximum relative deviation being less than 3%.

Estimation of the Reactive Flow Model Parameters for an Ammonium Nitrate–Based Emulsion Explosive Using Genetic Algorithms

A real coded genetic algorithm methodology that has been developed for the estimation of the parameters of the reaction rate equation of the Lee-Tarver reactive flow model is described in detail. This methodology allows, in a single optimization procedure, using only one experimental result and, without the need of any starting solution, to seek the 15 parameters of the reaction rate equation that fit the numerical to the experimental results. Mass averaging and the plate-gap model have been used for the determination of the shock data used in the unreacted explosive JWL equation of state (EOS) assessment and the thermochemical code THOR retrieved the data used in the detonation products' JWL EOS assessments. The developed methodology was applied for the estimation of the referred parameters for an ammonium nitrate–based emulsion explosive using poly(methyl methacrylate) (PMMA)-embedded manganin gauge pressure–time data. The obtained parameters allow a reasonably good description of the experimental data and show some peculiarities arising from the intrinsic nature of this kind of composite explosive.