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In this study, hydrogen-storage glass microballoons were introduced into emulsion explosives to improve the detonation performance of the explosives. The effect of hydrogen-storage pressure on the detonation characteristics of emulsion explosives was systematically investigated. Detonation velocity experiments shows that the change of sensitizing gas and the increase of hydrogen pressure have different effects on the detonation velocity. The experimental parameters of underwater explosion increase first and then decreases with the increase of hydrogen pressure. The decrease of these parameters indicates that the strength of glass microballoons is the limiting factor to improve the detonation performance of hydrogen-storage emulsion explosives. Compared with the traditional emulsion explosives, the maximum peak pressure of shock wave of hydrogen-storage emulsion explosives increases by 10.6% at 1.0 m and 10.2% at 1.2 m, the maximum values of shock impulse increase by 5.7% at 1.0 m and 19.4% at 1.2 m. The stored hydrogen has dual effects of sensitizers and energetic additives, which can improve the energy output of emulsion explosives.

The vortex at the Ta/Fe explosively welded interface is featured by the intermediate zone being fully bounded by Ta matrix, which differs from the vortex structures observed in the most bimetallic interfaces. In this work, advanced characterizations and numerical simulations were integrated to establish a detailed evolution model of the special vortex, and the associated governing mechanisms were identified. It was also inferred that the mesoscale cavity and microcracks within the vortex resulted from the geometric hole and extrusion movement that generated during the vortex evolution, respectively. Furthermore, a diversity of metallurgical structure was revealed at the Ta/Fe interface, which did support the deformation path of the interface material observed in the simulations. The insights gathered here benefit an in-depth comprehension of impact welding.

This work presents a systematic study of microstructure and mechanical property of TiNi Alloy/Q235 steel explosive-welded interface. The structure evolution as well as the thermodynamic state during the welding process was simulated using Smoothed Particle Hydrodynamic (SPH) numerical method. The interface is featured by regular wave structure with a period of ∼400 μm and an amplitude of ∼120 μm, resulting from the periodic interaction process of jets and colliding plates. Furthermore, it was found that the waves do not form in the initial collision zone, but undergo an evolutionary process of straight-irregular small wave-steady wave transformation. Intermetallic compounds like Fe2Ti and Ni3Ti were found in melting zones, which are the source of the microscopic cracks. Even so, the interface exhibits good bonding strength of 291 MPa that is higher than the Q235 steel of 180 MPa. The nanoindentation results show the hardness values decrease at first and then increase to the initial value with increasing distance from the bonding interface. The melting zone exhibits an ultrahigh hardness of 11.06 GPa, which confirms the formation of brittle intermetallic in the melting zone.

An innovative explosive welding method for the fabrication of multiple plates (EWMP) was proposed to further improve the energy efficiency of explosive welding explosive charges and reduce the impact on the surrounding environment. In this method, six metal plates were placed in parallel and three composite plates were obtained through one explosion in this paper. The microstructure of the joint was analyzed by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electron backscattering diffraction (EBSD). Compared to traditional explosive welding (TEW), the EWMP dramatically reduced the noise and vibration and increased the energy efficiency of explosives. The results showed the vibration data of EWMP were reduced by 16.7, 16.4, 2.8, and 1.5%, respectively, and at places of 3, 4, 5, and 6 m away from the explosion center, and explosive consumption of EWMP was reduced by at least half, compared to the traditional method when obtaining the same amount of welded plates. Through numerical simulation, the collision speeds of the composite plate are 610, 516, and 471 m/s, respectively, and the waveform of the composite plate is basically in coincidence with the result of the experiment.

In this study, copper/steel composite tubes were produced by an underwater explosive welding process. Scanning electron microscopy, energy dispersive spectroscopy, electron backscatter diffraction ...

In this study, a novel type of composite explosive was prepared by adding titanium fiber into the RDX explosive. The effects of the content of titanium fiber on the performance of the RDX explosive...

Porous materials can be used for accidental explosion prevention and suppression in process industries. In this study, an experimental study was conducted to study the effect of an aluminum foam pl...

Nitrous oxide has a wide range of applications, and the explosion in presence of nitrous oxide can cause serious disaster. In this study, we reported the explosion characteristics of hydrogen-metha...

In order to obtain high-quality CuCrZr/316L clad plates prepared by explosive welding (EW), theoretical analysis and numerical simulation were introduced to optimize welding parameters. The bonding properties of the achieved joints were systematically studied through multiscale interface analyses, mechanical performance tests, and evaluation of sealing properties. It was concluded that the theoretical analysis in collaboration with numerical calculations is an effective way to design parameters, because its predicted result was in good agreement with the ultrasonic test (UT) one. In both microstructure observations and mechanical tests, an excellent bonding quality of the CuCrZr/316L bimetallic plate was confirmed, where a uniform wavy morphology without defects such as voids and cracks was found at the bonding interface. The bonding strength was higher than the CuCrZr alloy. Moreover, a self-designed hydraulically pressed mold method was developed to manufacture a U-shaped CuCrZr/316L component, and the resulting sample matches well with the designed dimensions. Finally, the helium-leak test results demonstrate that the sealing property of the CuCrZr/316L bimetallic plate meets the practical requirements, indicating that the welded specimens were sound.

Cenospheres are the main component of industrial waste of fly ash and taking full advantage of them has good economic and environmental values. In this paper, cenospheres sensitized emulsion explos...

In this paper, experiments were conducted in a cylinder vessel at room temperature ( 293 K ) and initial pressure 100 KPa to study the effect of a crimped-ribbon plate on the explosion behaviors of methane, propane, ethylene, and hydrogen in air. The research gap of using crimped-ribbon plate obstacles to reduce explosion hazard was filled by testing the change of explosion pressure ( P m a x ), explosion time ( θ ) and maximum rate of pressure rise ( d p / d t ) m a x . The experimental results showed that a crimped-ribbon plate existence resulted in a drop in maximum explosion pressure due to the remarkable heat loss. With the growing activity (or decreasing MESG) of fuels, the effect of the crimped-ribbon plate on explosion pressure reduced. For hydrogen-air mixtures, the explosion time increased when a crimped-ribbon plate present. But for propane-air mixtures and ethylene-air mixtures, there was no obvious variation trend in the explosion time. The maximum pressure rise rate was decreased when the crimped-ribbon plate was introduced for the more sensitive mixtures (i.e., propane-air, ethylene-air and hydrogen-air mixtures). Two stages appeared when the flame quenched in the slit. The first was the extinguishment of the flame, and the second was that the temperature of the inert gas jet got lowered. After the flammable gas reached a certain concentration, it could no longer pass through the slit channel, because of the speed decrease. The smaller the critical speed for the more active gas.

Energetic hollow microcapsules (EHMs) were designed as dual-functional sensitizers for emulsion explosive with pentane/TiH2 and poly(methyl methacrylate) (PMMA) as core and shell, respectively. SEM...

An experimental study was performed in a rectangular duct to investigate the detonation diffraction process in stoichiometric methane-oxygen mixtures. A wedge was placed in the duct to form two channels between the wedge and the channel walls, i.e., an upper channel and a divergence channel. The upper channel heights were 27 mm, 47 mm and 67 mm, and the deviation angles ( α ) were 60 ° and 30 ° . On the bottom wall and side wall, soot foils were placed to record the cellular structure evolution. For the larger deviation angle ( α =60 ° ), the re-initiation mechanisms can be varied, which are affected by the upper channel height. Two overdriven detonation regions are generated behind the wedge on the bottom wall as well as the side wall for more sensitive mixtures (characterized by smaller detonation cell sizes). However, for insensitive mixtures, the re-initiation process seems to be more complicated. More regions containing finer cells can be observed on the foils. In case of α =30 ° , the detonation re-initiates at the divergence wall and propagates toward the side wall. Universally, the re-initiation is facilitated as the upper channel height increases, and equivalently, the re-initiation distance is reduced.

In this work, an improved explosive welding technique was introduced to obtaining high-quality metal coatings, where titanium (TA2) foils with different thicknesses of 0.1, 0.2, 0.3, and 0.4 mm were successfully coated on Q235 steel. Systematic investigations of the achieved claddings were conducted using macro- and micro-morphology observations, EDS elemental analyses, mechanical tests (three-point bending and nanoindentation), and electrochemical measurements. It was concluded that the explosive welding technique was an effective way to produce high-quality TA2 coatings. In both morphological analyses and mechanical tests, an excellent bonding quality was confirmed for the cases of TA2 foils with a thickness of greater than 0.1 mm. Meanwhile, the welding window was proved still being practical for predicting the bonding interface characteristics in the explosive welding of the metal foil. The EDS analyses and nanoindentation tests signified inhomogeneous properties of the materials near the bonding interface due to shock-induced work hardening and the formation of molten zone. Eventually, TA2 foil coatings were certified by electrochemical measurement to remarkably enhance the corrosion resistance of the Q235 substrate.

Through an unique manufacturing process which we call it “the Russian-doll-like experimental arrangement”, Steel/Cu pipes and Al/Cu pipe/rod are simultaneously explosively welded in a single experiment. After that, optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), longitudinal compression, transversal compression and compression-shear tests are conducted to analyze samples’ microstructure and mechanical properties. Results show that bonding interfaces of Al/Cu and Steel/Cu couples change from unstable ones, via regular/wavy ones, to final flat ones along the detonation direction. AlCu and Al2Cu are identified around the Al/Cu interface via EDS analysis, and atomic ratios of steel and copper around the Steel/Cu interface varies from 47/53 to 75/25. Samples’ yield strength/strain in longitudinal compression and transversal compression for Al/Cu couple are respectively 340 MPa/4.8% and 120 MPa/4.5%. Steel/Cu specimens’ yield strength/strain in longitudinal compression and compressive strength/failure strain in transversal compression are 598 MPa/5.8% and 90.97 MPa/21.0%, respectively.

This paper presents the first extensive research on secondary hazards and welding quality of a nover explosive welding technique, where colloidal water is used to cover the upper surfaces of the explosives. The use of the colloid water is proposed for improvement of energy efficiency and reduction of pollution of noise and dust. Welding tests were carried out to consider the effects of covering thickness on impact velocity of flyer plate, microstructure of bonding interface, explosion noise and dust. The results show that the colloid water significantly improves the ability of the explosive to drive the flyer plate, and reduce environmental pollution caused by explosion. The noise and dust decrease exponentially with increasing covering thickness, due to part of the shock energy and dust being absorbed by the colloidal water. Microstructure studies show that all the welds display wavy interfaces, and the wavelength and amplitude first increase and then decrease with increasing covering thickness. Vortices characterized by localized melting zone surrounded by strongly deformed bulk materials are formed for the welds performed with covering, and the EDS results indicate that the distribution of elements in the vortex region is gradually varied. Keywords: Explosive welding, Colloid water, Energy efficiency, Environmental pollution

An experimental investigation on the explosion characteristics of hydrogen-air mixtures diluted with inert gases (Ar, N2, CO2) was carried out in a cylinder chamber at room temperature (298 K) sub-atmospheric pressures (40 kPa, 60 kPa, 80 kPa, 100 kPa). Based on the pressure history recording, some explosion parameters, e.g., maximum explosion pressure ( P m a x ), maximum rate of pressure rise ( ( d p / d t ) m a x ), deflagration index ( K G ) and combustion duration ( θ ) were derived. Effects of initial pressure ( P 0 ), equivalence ratio ( φ ) and dilution fraction ( Z % ) on these explosion indices were discussed. The results show that with the increase of initial pressure, the maximum explosion pressure, maximum rate of pressure increase and deflagration index increase monotonously while the combustion duration decrease. The diluent effect on these parameters is increased in the order of Ar, N2 and CO2. Linear correlations P m a x / P 0 = f ( Z ) , P m a x = f ( P 0 ) and ( d p / d t ) m a x = f ( P 0 ) were found. In addition, the heat loss to the walls during the explosion propagation was estimated on the basis of the difference between the adiabatic and experimental measured pressure. The energy loss increases with the increase of initial pressure and specific heat of the dilutions.

To obtain an explosive suitable for the explosive welding of foils and produce a new way to reuse demilitarized explosives, RDX powders and high amounts of hollow glass microballoons (GMs) ...

In this study, a multi-step welding method combining explosive welding, laser welding, and Tungsten Inert Gas (TIG) welding was developed to manufacture 316L/CuCrZr hollow structural component. The welding parameters were selected according to theoretical calculations and preliminary tests, and the bonding qualities were evaluated by microstructure analyses and mechanical tests. The results demonstrated that this method was a feasible way to manufacture hollow structural components. All the joints exhibited good quality without micropores and cracks, and the tensile shear testing confirmed that the joining section was not the weakest element of the component. Under bending load, no separation, tearing or fracture was observed at the 316L/CuCrZr interface. The helium leak test results also proved that the welded specimens were sound. In addition, a hardening phenomenon near the 316L/CuCrZr interface was revealed by microhardness tests and fractography studies on tensile specimens.

Explosion tests were performed underwater to study the blast resistance of water-backed sandwich panels. Effects on the structural response of face-sheet and core configurations, including face-sheet thickness, cell wall thickness of the honeycomb, core thickness and charge mass, were investigated by a large number of experiments. Quantitative results were obtained in the tests with corresponding sensors and further processing. Further results characterized the permanent deformation of sandwich panels. A failure mode map was adopted to identify the effect of design parameters on the structural failure mechanism at this blast magnitude. Finally, a comparison between sandwich panels and monolithic plates was performed. The comparative study provided further experimental evidence for the benefits of sandwich in water-backed configuration. Present study led to the apprehension of blast resistance of water-backed sandwich structure to underwater blast load, thereby developed useful guidelines for the design of blast-resistant structural systems.

In order to improve the CuCrZr/316L transition joints manufactured by explosive welding (EW), a new EW method was developed to obtain meshing bonding interfaces. The welding parameters adopted in the experiment were close to the lower limit, and the bonding quality was evaluated by systematically microstructure and mechanical tests. The results showed that the meshing interfaces can effectively enhance CuCrZr/316L EW-joints by increasing bonding area. The microstructure results indicated that metallurgical bonding of CuCrZr alloy to 316L stainless steel was created along the meshing interfaces, and two types of bond were observed at the bonding interfaces, namely metal/metal and metal/solidified melt. The EDS analysis indicated that the melt mainly consisted of Cu. Fractography studies on tensile specimens showed cleavage fracture on the CuCrZr side and ductile fracture on the 316L side near the interfaces. The tensile shear test results showed that the shear strength of the meshing interface 0° and 90° was increased by 19% and 9%, when compared to the ordinary CuCrZr/316L EW-joints. The results of microhardness test revealed that the values of microhardness decreased as the distance from the interface increased.

In this paper, the low-cost syntactic foams were prepared by incorporating the fly ash cenospheres into the rigid polyurethane foams. The empirical relations were developed for predicting the porosity of the syntactic foams. Effects of the density and cenospheres size on the mechanical response of both the plain foams and aluminum foils reinforced foams were examined under quasi-static compression. The results show that, when the relative density was below 0.29, the cenospheres size marginally influenced the mechanical properties. When the relative density was above 0.29, the plain foams containing larger cenospheres exhibited better mechanical performances. For the reinforced foams, however, the mechanical properties were significantly improved by using smaller cenospheres. Moreover, the extra mechanical enhancement apart from the addition of the aluminum honeycombs was only effective for the composites containing smaller cenospheres. The reinforcing mechanisms of these composites were identified by the comparison of the mechanical properties and the analysis on their deformation behaviors. It demonstrated that the remarkable reinforcement was dominated by the failure pattern transition in the plain foams. This study may help to develop a comprehensive use of the fly ash cenospheres in civil engineering as functional materials.

In this study, the explosion behaviors of methane-air mixtures were investigated experimentally in a cylinder vessel (210 mm inner diameter and 210 mm height) filled with a single orifice plate at atmospheric pressure (1 atm) and room temperature (298 K). The equivalence ratios of the test mixtures ranged from 0.7 to 1.3. The blockage ratios of the orifice plates were from 0.49 to 0.94, and the distance between the orifice plates and the ignition point ( S ) were 25 mm, 50 mm and 75 mm. The results show that the maximum explosion pressure in the presence of an orifice plate. However, the effects of the orifice plate on the maximum rate of pressure rise are various. At the fuel-lean side, the maximum pressure rise rate is increased significantly (larger than that of the stoichiometric condition). As the distance between the orifice plate and ignitor increases, the maximum pressure rise rate increases. In the case of the fuel-rich conditions, the maximum pressure rise rate is the smallest for S = 25 mm, followed by the no plate condition, S = 50 mm and S = 75 mm. The mechanisms are left for further study.

N-hexane is an important alternative fuel for aviation kerosene in recent years. In this study, experiments of n-hexane in air at various initial temperatures of 353–393 K, initial pressures of 60–100 kPa and equivalence ratio of 0.7–1.7 were carried out in a cylindrical vessel with central ignition. The pressure histories and outward propagations of the spherical flame in the explosion process were recorded by the pressure sensor and Schlieren system, respectively. Explosion characteristics including the explosion pressure Pmax, the maximum rate of pressure rise (dP/dt)max and laminar burning velocity U1 were obtained and analyzed. Results show that all explosion parameters strongly depend on the n-hexane/air ratio, initial pressures and temperatures. The explosion pressure Pmax and maximum rate of pressure rise (dP/dt)max raise with the increase in initial pressure and decrease in temperature. However, the dimensionless explosion pressure Pmax/P0 remains constant with an increased initial pressure. Furthermore, the n-hexane/air flame propagation characteristics were investigated and the Markstein length were studied. The unstretched flame propagation speed S1 and laminar burning velocity U1 share the similar variation tendency with equivalence ratios, and they are increased with the increase of initial temperatures and decrease of pressures.

In this study, we report an experimental investigation of detonation propagation in a tube filled with bluff bodies. Experiments were carried out in a 6 m long rectangular cross-section (112 mm × 107 mm) tube. Firstly, the effect of an array of cube bodies (60 mm × 60 mm × 60 mm) on the detonation propagation characteristics were studied. Hydrogen, ethylene and acetylene mixed with air and hydrogen-oxygen diluted with argon were used as the test mixtures. Evenly spaced photodiodes were mounted on the top wall to recorded the optical signals, from which the detonation velocity could be determined. Soot foils were adopted in hydrogen-oxygen-argon mixture to record the evolution of the cellular structure. The results show that the flame accelerates rapidly in the obstructed tube. The critical conditions for deflagration to detonation transition (DDT) are found to be consistent with L/λ > 7, where L is the modified characteristic geometrical size for the tube with repeated cubes and λ is the detonation cell size. The long soot foils indicate that the detonation modes are influenced significantly by the bluff bodies. Near the limits, only some traces of transverse waves and shock waves can be observed, making the distinction between choked flame and quasi-detonation blurred. Secondly, the effect of a single bluff body on the detonation diffraction was investigated. Stoichiometric hydrogen-oxygen and those diluted with argon at sub-atmospheric pressures were used as the test mixtures. In the vicinity of the bluff body, a soot foil was used to record the detonation cellular structure evolution, from which the effect of the geometry of the bluff body on the diffraction and re-initiation processes was studied. Three transition regimes are observed: (1) a detonation propagates continuously over the bluff body; (2) the cellular structure initially fails and then recover due to the two symmetrical diffraction waves collision or interaction between shock waves and the bottom wall; (3) a detonation quenches and then re-initiate by flame acceleration. The re-initiation distance was found to be dependent on mixture sensitivity (chemical length scale) and the geometry of the bluff bodies (physical length scale).

Damage severity of sandwich panels to underwater explosion load depend not only on the shock factors, but also on the fluid behind the structure. Underwater explosion tests were performed on water-backed sandwich panels to examine the deformation and failure of such composite structure. The dynamic blast response of water-backed sandwich panel was investigated using the LS-DYNA software. An analytical three-stage model was developed for the deformation history of water-backed sandwich panel subjected to shock loading in water. Blast resistance of water-backed sandwich panel was compared with monolithic plate of equivalent areal mass and air-backed sandwich panel with the same configurations. Water-backed sandwich panel exhibited the best deformation/damage resistant capability. Compared with air-backed sandwich panel, core material exhibited greater volumetric strain when the sandwich structure wetted on both sides. Overpressure in the water behind structure was reduced to about 7% by using sandwich structure over monolithic plate of equivalent thickness. Present study led to the apprehension of dynamic response of water-backed sandwich structure to underwater blast load, thereby developed useful guidelines for the design of blast-resistant structural systems.

A novel energetic microsphere with multicore hollow structure and uniform particle size is prepared by an improved suspension polymerization-thermal expansion method with methyl methacrylate, azodicarbonamide (AC) and TiH2 powder as monomer, blowing agent and core material, respectively. The energetic hollow microspheres (EHMs) can play double roles as sensitizers and energetic additives in emulsion explosive, and experimental results show that the EHMs could increase the power of emulsion explosive without affecting its safety. This method provides a completely new idea for the development of high energy emulsion explosive.

Explosion characteristics and influential factors of hybrid CH4/coal dust explosions are studied using a 20-L spherical explosion vessel. Experimental results show that the maximum explosion pressure and maximum rate of pressure rise increase in the initial phase and then decrease as the coal dust or CH4 concentration increases. The optimum concentrations of coal dust and CH4 are 200 g/m3 and 5 vol.%, respectively, when the initial pressure is equal to the atmospheric pressure. Moreover, the maximum explosion pressure keeps rising with the increasing initial pressure, and the maximum rate of pressure rise also shows an increasing trend. In addition, the optimum concentration of hybrid mixture varies with the initial pressure. The explosion risk of hybrid CH4/coal dust is much higher than that of pure coal dust in all dust concentrations, but it is only higher than that of pure coal dust explosion at high CH4 concentrations.

In this study, the detonation behaviors of stoichiometric methane-oxygen mixture were examined in a round tube filled with orifice plates. The blockage ratio was 0.56 and the plate spacings were 1, 1.5 and 2 times the tube diameter. Detonation velocity measurement and soot foils were adopted to study the propagation characteristics. Experimental results show that the abrupt velocity jump was only observed for the obstacle configuration with S = 2 D , where S and D are the plate spacing and the tube diameter. For a fixed plate spacing, the detonation velocity as well as the detonation limits are independent of the orifice geometry, since the effective diameters ( d e f f ) of the orifices are almost the same. The ratios of d e f f to the detonation cell size ( λ ) were found to be 0.4–0.5. For sensitive mixtures, the soot foils indicate that the detonation re-initiation occurs via hot spots formed on the wall. As the initial pressure decreases, the detonation can travel without hot spots generation. At the limits, no indication of detonation can be observed for obstacle configurations with smaller spacings in spite of the higher velocity (compared with the isobaric sound speed of the products). The propagation mechanism near the limits is left, however, for further investigation.

To study the effects of hydrogen addition on the explosion characteristics (the explosion pressure and maximum rate of pressure rise) of n-hexane/air mixtures, experiments were performed in a cylindrical vessel at 100 kPa, 353 K, with equivalence ratios of 0.8–1.7 and hydrogen addition range from 0% to 80%. Concurrently, flame images were captured by high-speed schlieren photography to study the burning performance. The results indicate that both the explosion pressure and maximum pressure rise rate increase with the increase in hydrogen addition in terms of the lean n-hexane/hydrogen/air mixtures. With respect to the richer mixtures, however, the inverse tendency is observed. With increasing hydrogen fractions, the explosion pressure and maximum pressure rise rate decrease. The peak values of the explosion pressure and maximum pressure rise rate shift to the leaner mixture with increased hydrogen proportion. Moreover, the laminar burning velocities of n-hexane/hydrogen/air mixture were also obtained via the expanding spherical method and the pressure-time histories, respectively. Variation of laminar burning velocity with hydrogen proportion from both methods were studied as well, and the results show that the laminar burning velocity changes significantly under different hydrogen addition.