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Nitrocellulose (NC) is prone to spontaneous decomposition with exothermic heat release and thus is generally evaluated for stability during the storage process using standardized test methods such as the Abel test that measures the amount of nitrogen oxides (NOx) released from NC. In the present study, we evaluated the relative stability of various NC and NC-based propellants by monitoring the heat release behavior in an oxygen atmosphere via isothermal calorimetry. The results were compared with ones of the Abel test to evaluate the validity of the conventional stability test. The comparison revealed that there was no correlation between the stabilities predicted by the isothermal calorimetry and the results of the Abel test; some of the samples were evaluated as stable in the Abel test even if they released the decomposition heat easily, which means that the Abel test can occasionally overestimate the NC stability. In addition, the time change in the NOx release behavior based on the chemiluminescence method suggested that the Abel test mainly determined the desorption amount of NOx physically adsorbed on the surface of the samples, not that derived directly from the decomposition of NC. This possibly resulted in the incongruity with the results of the isothermal calorimetry, which instantly measures the heat released during decomposition.

Accelerated adoption of hydrogen gas for energy storage requires improved safety for hydrogen storage. In particular, control of self-ignition of hydrogen vented through tubes by pressure relief devices (overpressure protection devices), such as rupture disks, is needed. We clarify the process of self-ignition in tubes of various lengths during venting of high-pressure hydrogen and observe flame behavior at the tube exit. The importance of distance from the rupture disk for flame front evolution is revealed. Specifically, in a tube longer than a critical value, the self-ignited flame undergoes a quenching process, possibly due to steam formation, before it exits the tube. A tube that is too short does not give the gas sufficient time for hydrogen and air mixing to initiate self-ignition. Finally, at slightly longer tube lengths, the hydrogen ignites, but the flame does not fully develop before it exits, and the vortex formed by expanding gas extinguishes it.

Turpentine is a renewable resource, has good combustion performance, and is considered to be a fuel or promising additive to diesel fuel. This is very important for the investigation of thermal stability and energy oxidation characteristics, because evaluation of energy or fuel quality assurance and use safety are necessary. The main components of turpentine are α-pinene and β-pinene, which have unsaturated double bonds and high chemical activity. By investigating their thermal stability and oxidation reaction characteristics, we know the chemical thermal properties and thermal explosion hazard of turpentine. In this present study, the thermal stability and oxidation characteristics of α-pinene, β-pinene and α-pinene/β-pinene mixture were investigated using a high sensitivity accelerating rate calorimeter (ARC) and C80 calorimeter. The important parameters of oxidation reaction and thermal stability were obtained from the temperature, pressure and exothermic behavior in chemical reaction. The results show that α-pinene and β-pinene are thermally stable without chemical reaction under a nitrogen atmosphere even when the temperature reaches 473 K. The initial exothermic temperature of the two pinenes and their mixture is 333–338 K, and the heat release (−ΔH) of their oxidation is 2745–2973 J g−1. The oxidation activation energy (Ea) of α-pinene, β-pinene and α-pinene/β-pinene mixture is 116.25 kJ mol−1, 121.85 kJ mol−1, and 115.95 kJ mol−1, respectively. There are three steps in the oxidation of pinenes: the first is the induction period of the oxidation reaction; the second is the main oxidation stage, and the pressure is reduced; the third is thermal decomposition to produce gas.

Rosin is a sustainable resource, which is mainly composed of resin acid. Rosin-modified resin is widely used in adhesives, inks, coatings, and other fields, and its stability is very important for the production, storage, and use of products. Thermal stability and reactivity of three resin acids (levopimaric acid, neoabietic acid, and dehydroabietic acid) and four rosin-modified resins were studied using an accelerating rate calorimeter (ARC). They are stable, and exothermic reactions do not occur even when they were heated to 200 °C under a nitrogen atmosphere, but they are unstable under an oxygen atmosphere. The mechanism of the oxidation reaction process was found: first, resin acids absorb oxygen, and then an exothermic oxidation occurs. The initial exothermic temperature (T 0) of levopimaric acid, neoabietic acid, and dehydroabietic acid are 354.01, 353.83, and 398.20 K, the initial oxidation kinetics shows a second-order reaction, and the activation energies (E a) are 42.90, 58.05, and 46.60 kJ/mol, respectively. Peroxide concentration of three resin acids were determined by iodometry. The T 0 values of hydrogenated rosin, disproportionated rosin, hydrogenated rosin glyceride, and hydrogenated rosin pentaerythritol ester, the four rosin-modified resin, are 353.71, 348.32, 412.85, and 412.44 K. Levopimaric acid and neoabietic acid have higher oxidative reactivity and easily undergoes an oxidation reaction at lower temperature. Rosin-modified resins are stable and find it difficult to undergo oxidation reactions.

A quantitative risk assessment of human life during the operation of a hydrogen refueling station (HRS) is conducted. We calculate the risks for three accident scenarios: a hydrogen leak from the external piping surrounding a dispenser, a hydrogen leak from an accumulator connection piping and a hydrogen leak from a compressor/connection piping in the HRS. We first calculate the probability of accident by multiplying the estimated leak frequency with the incident occurrence probability considering the ignition probability and failure probability of the safety barrier systems obtained through event tree analysis for each scenario. We next simulate the blast and flame effects of the ignition of concentration fields formed by hydrogen leakage. We then use existing probit functions to estimate the consequences of eardrum rupture, fatalities due to displacement by the blast wave, fatalities due to head injuries, first-degree burns, second-degree burns, and fatal burn injuries by accident scenario, leak size, and incident event, and we estimate the risk distribution in 1-m cells. We finally assess the risk reduction effects of barrier placement and the distance to the dispenser and quantify the risk level that HRSs can achieve under existing law. Quantitative risk assessment reveals that the risk for a leak near the dispenser is less than 10−6 per year outside a distance of 6 m to the dispenser. The risk for a leak near the accumulators and compressors exceeds 10−4 per year within a distance of 10 m from the ignition point. A separation of 6 m to the dispenser and a barrier height of 3 m keep the fatal risk from burns to the workers, consumers and residents and passersby below the acceptable level of risk. Our results therefore show that current laws sufficiently mitigate the risks posed by HRSs and open up the possibility for a regulatory review.

It is well known that detonation velocity and loading density of high explosive exhibits linear relationship for various explosives. Using this linear relationship, in a previous paper we proposed EOS for detonation products which could applied to arbitrary initial density without changing parameter set. This paper reports the results of applying the proposed method to RDX, PETN and TNT.

In modern mining industry, rock blasting is one of the essential working for rock breakage in terms of economic and efficient aspects. Blast-induced ground vibration may give serious impacts on wide range of surrounding environment, so it has to be paid much attention in the blasting process. Peak Particle Velocity (PPV) is one of the most important parameters related with blast-induced ground vibration. The prediction of PPV is very important in order to design an appropriate blasting standard and minimize its environmental impacts. However, general prediction equations and/or methods have not been developed yet because they do not consider the impact of rock mass and geological conditions. Therefore, in this paper, indoor tests, field tests and numerical simulation were conducted for assessing the effect of fragment in the rock mass on propagation behavior of ground vibration. In order to enable versatile vibration prediction at different sites with different blasting and geological condition, we investigated the differences in vibration behaviors due to blasting design, and the difference in geological condition. The result of a series of tests suggested that fragments in the rock mass related with the damping behavior of the blast-induced ground vibrations and more accurate prediction of the ground vibration (PPV) could be performed by considering fragment condition in the rock mass.

The dynamic strain distribution behavior of a mortar block blasting was experimentally investigated. A small-scale blasting experiment using a mortar block with well-defined property was conducted and the dynamic strain distribution on the mortal block surface was analyzed using a Digital Image Correlation (DIC) method to establish the effective method for investigating the relationship between blast design and fracture mechanism. The block was blasted by simultaneous detonation of Composition C4 explosive charges with an electric detonator in two boreholes. The behavior of the block surface was observed by two high-speed cameras for three-dimensional DIC analysis and it was also measured by a strain-gauge for comparison. The three-dimensional displacements of the free surface of the block were obtained and dynamic strain distributions were computed. A point strain profile extracted from the analyzed strain distribution data was compared with a directly observed strain profile by the strain gauge.

DMF is renewable energy obtained from glucose, its thermal stability and safety need to be investigated. Accelerated rate calorimeter (ARC) is widely used to evaluate the risk of hazardous materials. In this paper, the thermal stability and safety of DMF oxidation were investigated using an ARC. DMF does not react even when the temperature reaches 452 K under nitrogen atmosphere. In oxygen atmosphere, the onset temperature (T0) of DMF oxidation is 323.49 K, and the activation energy (Ea) is 172.35 kJ/mol. The peroxide concentration of oxidation process was determined by iodometry, and the oxidation products were analyzed by gas chromatography - mass spectrometry. The pressure and exothermic behavior of ARC are related to the reaction mechanism. A simple three steps mechanism of DMF oxidation was described: fist DME reacts with oxygen to form peroxide; second is the main oxidation stage, oxidation products are complex; the third step is thermal decomposition.

Organic hydride hydrogen refueling stations are currently being developed in Japan. For these stations, we estimate the consequence and damage caused by explosions and heat radiation after a hydrogen leak, and the acute toxicity caused by the leakage and dispersion of methylcyclohexane and toluene energy carriers. First, the organic hydride hydrogen refueling station is defined, and an accident scenario for four leak sizes of hydrogen and chemical leak accidents is set. Next, simulations of the blast wave pressure and heat radiation after the hydrogen leak and of atmospheric dispersion for the evaporation after liquid methylcyclohexane and toluene leaks are performed. Probit functions or threshold values are created for each type of effects caused by the explosion, heat and the inhalation effect on humans of toluene acute toxicity. Population data for the area surrounding the station are created in a 10-m mesh. The consequence and damage are estimated for each leak size. The results show that although the explosion and chemical leak affects the area around the refueling station, the effects are small in all of the accident scenarios. In contrast, although the area of the heat effect is limited to inside the refueling station, the burn damage is large, and there is a need for conducting quantitative risk assessment.

A high-pressure hydrogen jet released into the air has the possibility of igniting in a tube without any ignition source. The mechanism of this phenomenon, called spontaneous ignition, is considered to be that hydrogen diffuses into the hot air caused by the shock wave from diaphragm rupture and the hydrogen-oxidizer mixed region is formed enough to start chemical reaction. Recently, flow visualization studies on the spontaneous ignition process have been conducted to understand its detailed mechanism, but such ignition has not yet been well clarified. In this study, the spontaneous ignition phenomenon was observed in a rectangular tube. The results confirm the presence of a flame at the wall of the tube when the shock wave pressure reaches 1.2–1.5 MPa in more than 9 MPa burst pressure and that ignition occurs near the wall, followed by multiple ignitions as the shock wave propagates, with the ignitions eventually combining to form a flame.

Accelerated calorimeter (ARC) is widely used to evaluate the hazard of solid or liquid materials, however, there are few literatures on the investigation of gas hazard. In this paper, thermal polymerization and oxidation characteristics of BD were investigated using an ARC. The onset temperature of BD polymerization is 408.5 K under nitrogen atmosphere. Under oxygen atmosphere, the oxidation characteristics of BD with oxygen are: first, pressure is reduced when oxygen reacts with BD, and peroxide is formed; second, an exothermic oxidation reaction has occurred, and the onset temperature of oxidation is 343.2 K, and the activation energy (Ea) of BD oxidation is 112.6 kJ/mol. The products of polymerization and oxidation were analyzed by gas chromatography - mass spectrometry (GC–MS). The brief mechanism of oxidation reaction is described. These results are helpful to understand the characteristics of chemical engineering, and to research and develop the safety technology of BD.

The underwater sympathetic detonation of pellet explosives was taken by high-speed photography. The diameter and the thickness of the pellet were 20 and 10 mm, respectively. The experimental system consists of the precise electric detonator, two grams of composition C4 booster and three pellets, and these were set in water tank. High-speed video camera was used with 10 Mfps. The underwater explosion of the C4 booster and a pellet was also taken to estimate the propagation processes of the underwater shock waves. Numerical simulation of the underwater sympathetic detonation of the pellet explosives was also carried out and compared with experiment. The compression process of the pellet caused by interaction of underwater shock wave was clearly taken. Those data could be available to validate the accuracy of reactive flow simulation.

The flame observed during the sudden release of high-pressure hydrogen into a tube filled with air, in the absence of an igniter, has not yet been investigated. In this study, the self-ignition and flame development behavior of high-pressure hydrogen flow in a tube is investigated to obtain fundamental knowledge for safety engineering. Two high-speed cameras are used simultaneously to obtain density gradient data from the shadowgraph image and flame dynamics from the direct image. Self-ignition occurs at the point near the sidewall in the region where cold hydrogen and preheated air are mixed by the precursor shock wave. After ignition, the flame propagates along the wall surface and spreads throughout the mixing region.

Nitrocellulose (NC) is known to undergo spontaneous ignition, and its thermal stability has been previously reported to decrease in the presence of sulfuric acid. In this study, we evaluated the decomposition and ignition behavior of NC in the presence of sulfuric acid using an accelerating rate calorimeter (ARC) and hand-built ignition testing equipment. The results of the ARC experiment indicated that the thermal stability of NC decreased when the amount of sulfuric acid was increased above 10-5 mol/g (NC). In addition, when NC (4 g) mixed with sulfuric acid (6.6 mol/L, 1 g) was isothermally stored at 75°C in a glass flask, the color of the reaction mixture changed from white to brown. After 83–127 min, NC spontaneously ignited and produced a loud explosion.

In order to know accurate information on the non-ideal detonation pressure, steel tube test was carried out on ammonium nitrate (AN) and activated carbon (AC) mixtures. In this test, detonation velocity and pressure were measured simultaneously by varying thickness of PMMA placed between AN/AC and pressure gauge. The length and the diameter of the steel tube were 350 mm and 35.5 mm. The results showed that shock pressure attenuation in PMMA was not observed for this experimental condition (PMMA gap; 3-5 mm). The averaged measured peak pressure and detonation velocity were 3.4 GPa and 3.2 km/s.

We numerically investigated high-pressure hydrogen leakage from transportation facilities, focusing on the steady mass flow rate and pressure distribution in a tube during the leakage. We studied steady leakage from a square opening in a square duct as well as leakage from a ruptured cylindrical tube with unsteady closure of a cutoff valve from fully open. A prediction model for the mass flow rate and pressure distribution inside the tube was proposed; such a model would help prevent physical hazards during an accident. We considered changes in the physical quantities according to the fluid dynamics occurring inside the tube. The flow properties were divided into two phases: (i) the unsteady expansion wave propagating inside a tube filled with hydrogen and (ii) the acceleration of hydrogen due to the reduction in the cross-sectional area between the tube and the leakage opening. To close the prediction model, we introduced contraction coefficient models depending on how the hydrogen leakage occurred. The mass flow rate and pressure drop during the leakage estimated by our prediction model showed good agreement with numerical simulation results when the contraction coefficient model was appropriately chosen. This model is considered highly applicable to the construction condition of pressure sensors, the operating conditions of a valve, and the prediction of mass flow rate during an accident.

A multidimensional analysis code for reactive shocks (MARS), which is developed to solve various problems in the physical hazard analysis of high energetic materials, has been applied to such complex problems as multi-material problem and sympathetic problem because it can employ various types of equations of state and a materials database. However, it was difficult to meet a growing demand for large-scale analysis and fluid-structure interaction (FSI) analysis. To address these issues, this study reports a parallelization of the code and an implementation of the functional capability of FSI analysis, and performance results for sample problems were also shown.

The relationship between the initial temperature dependence of the detonation velocity and the initial density is examined using a proposed unified form of the EOS for pentaerythritol tetranitrate (PETN). First, the derivatives of the variables at Chapman-Jouguet (C-J) points are calculated. These derivatives are used to investigate the initial state dependence of the detonation velocity using the relationship between the detonation velocity and the initial state variables. As a result, the contributions of the coefficient of thermal expansion and the increment of the initial internal energy to the detonation velocity are clarified. We found that the initial temperature derivative of the detonation velocity can be estimated from the initial density derivative of the detonation velocity.

In this study, a high strain rate test method of a steel plate under blast loading from high explosive was designed and was conducted by a combined experimental/numerical approach to facilitate the estimation process for the dynamic stress-strain curve under practical strain rate conditions. The steel plate was subjected to a blast load, which was generated by Composition C4 explosive and the dynamic deformation of the plate was observed with a high-speed video camera. Time-deformation relations were acquired by image analysis. A numerical simulation for the dynamic behaviors of the plate identical to the experimental condition was conducted using a coupling analysis of finite element method (FEM) and discrete particle method (DPM). Explosives were modeled by discrete particles and the steel plate and other materials were modeled by finite element. The blast load on the plate was described fluid-structure interaction (FSI) between DPM and FEM. As inverse analysis scheme to estimate dynamic stress-strain curve, an evaluation using a quasistatic data was conducted. In addition, two types of approximations for stress-strain curve were assumed and optimized by least square method. One is a 2-piece approximation, and was optimized by least squares method using a yield stress and a tangent modulus as parameters. The other is a continuous piecewise linear approximation, in which a stress-strain curve was divided into some segments based on experimental time-deformation relation, and was sequentially optimized using youngs modulus or yield stress as parameter. The results showed that the piecewise approximation can gives reasonably agreement with SS curve obtained from the experiment.

The present paper deals with auto-ignition and combustion of high pressure hydrogen leaks through a tube with air into atmosphere. The experiments using a high pressure tube with hydrogen and an extension tube with air of 10 mm diameter are performed to clarify the auto-ignition and combustion behavior of high pressure hydrogen jet spouting through the extension tube. In order to improve repeatability and reliability of experiments, a plunger system with a needle is applied to control a rupture of a PET diaphragm, which separates hydrogen from air. The most important result obtained in the present study is that the minimum diaphragm burst pressure at which the auto-ignition is registered, is found to be between 1.0 and 1.2 m of the extension tube length. This tube length is longer compared to tubes used in the previous studies. Combustion and Mach disk at the extension tube exit to atmosphere are observed using a high speed camera which is set at the frame speed of 1 × 10 5 fps when the ignited hydrogen jet is spouted out the tube.

To establish the effective method for blasting, the understanding of the dynamic fracture process is important. We have propo sed the dynamic fracture test for rock which has employed the underwater shock wave generated by explosion of explosive. This report presents the estimation method for the tensile strength of rock materials using the experimental results obtained by o ur proposed fracture test.

In order to investigate the hazard of the fragments caused by the explosion damage, the simply-simulated explosion experiment and numerical simulation were conducted. In this study, the behavior of the disk supposing the fragment driven by an explosive was investigated. In the experiment, the optical observation using a high-speed camera was performed to obtain the basic data about a disk, such as flying velocity. Moreover, numerical simulation was performed using analysis software LS-DYNA. Comparison and examination for experimental results and numerical results were reported.

This study involves a screening-level risk assessment of the impairment of human health and life related to hydrogen explosion and chemical release during the operation of a hydrogen refueling station (HRS) that uses organic hydride. First, twenty-one accident scenarios were identified involving the leakage of hydrogen, toluene and methylcyclohexane (MCH) in the HRS. Next, the leakage frequency for each scenario was estimated using a hierarchical Bayesian model. Simulations were then performed of the blast-wave pressure and heat radiation after a hydrogen leak and of atmospheric dispersion of evaporated chemicals after leaks of liquid MCH and toluene. The consequences were estimated for each scenario according to leak size using the existing probit functions and threshold values. Finally, the risk due to explosion, heat radiation, and acute toxicity was estimated by multiplying the consequence by the leakage frequency. The results show that the mortality risk of explosion and acute effect is less than 10−6 per year, which is a negligible level of concern. However, the mortality risk of heat radiation in the scenarios involving hydrogen leakage from the pipe connected to the cylinders and compressors exceeds 10−4 per year inside the HRS, thereby requiring additional steps if a more-detailed risk assessment is needed.

The development study of blast containment vessels for anti-terrorism has been conducted. The goal of this study is to develop safe disposal vessel for 10 kg of explosives. Considering of the use at the airport or railroad stations, it needs to be more compact compared with the conventional explosion chamber. By introducing both the internal structure and attenuation technology in the vessel, sufficient blast proof ability to contain internal explosion is realized. The blast containment vessel can be used repeatedly by exchanging the internal structure. To realize these concepts, model experiments were carried out using high speed photography, strain and pressure measurements. By introducing these technologies, the vessel for the 1 kg of explosive materials has been made, and the experiments employing 1 kg C4 explosive have been conducted. Finally, the compact blast containment vessel for 10 kg explosives was made, and its blast proof ability was shown by the internal blast test.

This paper presents a projectile impact experiment using a compact accelerator driven directly by explosives, and a numerical simulation of the impact. The compact projectile accelerator has been developed to evaluate the perforation resistance of structural materials. Projectile shooting tests were conducted and the relationship between the explosive weight and the injected projectile velocity was obtained. A series of impact tests on the targets, with varying projectile velocity, was examined using the developed accelerator. The projectile was made of SNCM (nickel–chromium–molybdenum special steel of the Japanese Industrial Standard) and the targets were aluminum 5052S alloy plates. The projectile track and the impact process on the targets were observed with a SHIMAZU HPV-1 high-speed video camera and the velocity of the projectile and interactive behavior were evaluated. A numerical simulation study was conducted using the parallel version of the non-linear finite element code of LS-DYNA to follow the impact experiments and determine the ballistic limit of the projectile for the targets.

The behaviors of the high explosive near the critical conditions for shock initiation of detonation are investigated by high speed photography and pressure measurements in gap tests. The sample is RDX base explosive, and the inner diameter of donor and acceptor charges is 26 mm. Gap material is PMMA. Near the critical condition, the results under the following conditions have been discussed. 1) Shock to detonation transition (SDT) take place in acceptor, 2) The SDT does not occur, but the reaction wave affects the leading shock front in acceptor, and 3) The gap length in which the effect of the reaction wave to shock front almost disappears. These results are very useful to construct the initiation model for solid explosive.

To design a cylindrically-shape explosion container, the experiment of a high explosive charge detonating in a steel pipe has been performed. The charges, composition C4, were positioned at the geometrical centre of the steel pipe. Two kinds of measurements were performed on the steel pipe: circumferential strain and outside diameter. The strain-time history shows that the pipe structure vibrates and the vibration is decaying. It has been reported that this type of response is explained as the mechanism of strain growth, and this problem is taken up to verify computer simulation in this study. This simulation code could be strong tool to estimate the geometries of the explosion container. The relationship among the pipe parameter, explosive charge and pipe’s final deformation is proposed as practical guidance for predicting radius and thickness of the pipe correspond to the level of internal blast loading.

This paper presents the design of a compact size projectile accelerator, and its application. To meet the various needs such as a compact body size to use under various experimental conditions, an easy maintenance for repetitive experiments during a certain period, and a capability of the velocity control, the compact accelerators were newly designed with a direct explosive drive method. Two different types of accelerator were designed: a PMMA accelerator and a metal accelerator. The pictures of the projectile shoot using the designed accelerators were recorded by SHIMADZU HyperVision HPV-1 high-speed video camera. As a result, it was recognized that the PMMA accelerator was failed to accelerate the projectile, while the metal accelerator succeeded to accelerate it effectively. The accelerating performance of the metal accelerator was further investigated. The explosives for projectile acceleration were Emulsion explosive and Composition C4 explosive weighing 5 to 35g. It was found that the metal accelerator has the capability to control the projectile velocity adjusting the weight of the explosives, and there is an approximate linear correlation between them in our experimental range. A series of impact tests on 5052S aluminum alloy targets was examined using the accelerator.

To assess the assumptions behind the two phase mixture rule for reacting explosives, the shock-to-detonation transition process was calculated for high explosives using a finite difference method. An ignition and growth model and the Jones–Wilkins–Lee (JWL) equations of state were employed. The simple mixture rule assumes that the reacting explosive is a simple mixture of the reactant and product components. Four different assumptions, such as that of thermal equilibrium and isotropy, were adopted to calculate the pressure. The main purpose of this paper is to present the answer to the question of why the numerical results of shock-initiation are insensitive to the assumptions adopted. The equations of state for reactants and products were assessed by considering plots of the specific internal energy E and specific volume V . If the slopes of the constant-pressure lines for both components in the E – V plane are almost the same, it is demonstrated that the numerical results are insensitive to the assumptions adopted. We have found that the relation for the specific volumes of the two components can be approximately expressed by a single curve of the specific volume of the reactant vs that of the products. We discuss this relationship in terms of the results of the numerical simulation.

The effects on the sputtering of zirconium by mixing hydrogen or oxygen with argon plasma were investigated. Plasmas were generated by electron cyclotron resonance (ECR) heating. The zirconium target was cylindrical, 7 cm in diameter, 2 cm in length and 0.1 mm in thickness, and was set on the downstream side from the ECR point. The zirconium sputtering rate was evaluated from the amount of zirconium deposited onto the copper sample collector, which was dissolved with aqua regia after plasma sputtering experiments, and then the zirconium concentration was measured by ICP-AES. The chemical sputtering effect is discussed based on comparison with the physical sputtering effect. It was found that the sputtered zirconium flux depends on the oxygen partial pressure. It is concluded that the sputtering of zirconium in Ar–O2 is governed by chemical interaction between oxygen radicals and the zirconium target.

Since the characteristic values of detonation such as the detonation velocity and pressure are dependent on the initial density of high explosive, the parameters of the equation of state (EOS) for detonation products or unreacted explosive are also dependent to the initial density. In general, the parameter set for each initial density has to be obtained to compute detonation phenomena. For simulation of arbitrary initial densities cases, we try to construct a new simulation procedure that only employs the information of theoretical maximum density (TMD). The well known linear relationship between detonation velocity and initial density for high explosive has been employed for this study. Two types of simulation were carried out. The Gruneisen parameter as function of specific volume was calculated by solving the ordinary differential equation, and was employed as unified form EOS to simulate detonation phenomena. To obtain the information of the EOS for arbitrary initial density, the simulation of another type was executed. The calculation field is filled with the particle for TMD and the air, and the density of the high explosive is adjusted. It is investigated whether the velocity of detonation for an arbitrary density can be reproduced only by information on TMD.

After the detonation of a solid high explosive, the material has extremely high pressure keeping the solid density and expands rapidly driving strong shock wave. In order to investigate the blast wave propagation driven by the 32-kg TNT explosion of the underground magazine a three-dimensional simulation is performed with a stable and accurate numerical scheme without a special modeling for the expansion process of detonation product gas. The compressible fluid equations are solved by a fractional step procedure which consists of the advection phase and non-advection phase. The former employs the Rational function CIP scheme in order to preserve monotone signals and the latter is solved by IDO (Interpolated Differential Operator) scheme for achieving the accurate calculation. For this simulation results, photo-realistic visualization is achieved with combination of volume rendering with isosurface rendering on grid computer.

We have conducted the experiments for shock sensitivity of high energetic materials by gap test. The set up of gap test have been improved to observe the shock initiation phenomena in acceptor charge by high‐speed video. The length of gap material was varied to observe the reaction process under various situations. The luminescence at the surface of acceptor holder was used Go/Nogo decision. The distance from the gap end to the luminescence area increases with increasing in gap length. In the critical gap length in which the sympathetic detonation does not occur, the remarkable decomposition of acceptor charge was observed as gas expansion.