Trinitrotoluene Research Articles

Sensitive electrochemical determination of 3-nitro-1,2,4-triazol-5-one (NTO) by the gold nanoparticles-decorated glassy carbon and smartphone-integrated screen-printed electrodes based on polyethyleneimine linked with crosslinking agent glutaric dialdehyde

Rapid and sensitive voltammetric methods for 3-nitro-1,2,4-triazol-5-one (NTO) determination are scarce in the literature. In the present research, we reported a crosslinked polyelectrolyte-based modified electrode decorated with gold nanoparticles that can be easily formed on the surfaces of both screen-printed electrodes (SPEs) and glassy carbon electrodes (GCEs) for the first time, as well as a voltammetric method for the electrochemical determination of NTO. Cobalt-amine sites formed between PEI and cobalt(II)-acetylacetonate (CoAcAc, an electrocatalyst) are used as a redox mediator. Electrochemical reduction of NTO in the concentration range of 1.3–13 mg L−1 was carried out by both the developed DPV method and a smartphone application. LOD and LOQ values were found to be 0.4 mg L−1 and 1.25 mg L−1 for the developed DPV method and 0.26 mg L−1 and 0.82 mg L−1 for the smartphone implementations, respectively. By taking advantage of the restricted solubility of some other nitro-explosives in water, the solvent medium and the pH of the supporting electrolyte (the pH value at which NTO exists in anionic form, not valid for other explosives) were optimized. In the presence of other nitro explosives, such as trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), 2,4-dinitro toluene (DNT), and 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), the percentage recovery values range from 90.1 to 105.2 % according to the DPV results measured in admixtures with NTO. Surface morphologies of the modified electrode were characterized using scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR), whereas electrochemical studies were performed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The detection method proposed was not adversely affected by common soil ions as well as detergents, sugar, sweeteners, caffeine, and paracetamol-based painkillers as camouflage materials for explosives, the negative impacts of which were either nonexistent or eliminable.

Experimental Evaluation on Blast Resistance of Reinforced Concrete Structures under Partially Confined Explosion

As the risk of accidental explosions at ammunition storage or hydrogen charging station increases in populated area, it is needed to design the facilities against blast loading, particularly subjected to partially confined explosion. However, the partially confined explosion lacks experimental test data to efficiently design the facilities subjected to the potential threat, when compared to unconfined or confined explosion cases. As a fundamental study on partially confined explosion, two partially buried tunnel-type structures with normal- and high-strength concretes were tested under a weight charge of 5.9 kg TNT explosion. The major parameters were concrete compressive strength and reinforcement ratio. The test result showed that the damage of the concrete structure with normal-strength concrete was extremely severe, whereas that of the specimen with high-strength was relatively mild. Further, finite element (FE) analyses were performed to investigate the confinement effect of blast load. The FE analysis result showed that under partially confined explosion, the reduction of the maximum displacement by using higher concrete strength was significant, while preventing the failure of the structure. This study provides fundamental data for designing the facilities with explosives subjected to the partially confined explosion.

Characterization of industrial TNT in ammunition shells: An in-depth study of artificial aging effects using Fourier-Transform infrared spectroscopy and gas chromatography–mass spectrometry

In this study, we comprehensively investigated the degradation of industrial trinitrotoluene (TNT), focusing on the effects of aging and direct contact with steel surfaces, mirroring real-world usage conditions. While practical knowledge exists regarding this degradation, the existing literature lacks in-depth insights into the underlying processes. To address this gap, we conducted experiments using small steel samples, representative of military ammunition casings, which were coated with TNT and subjected to 30 days of heating at 75 °C under vacuum conditions. A subset of these samples was coated with a protective red alkyd paint. After the aging process, the TNT was carefully removed from the metal surfaces and subjected to a comprehensive analysis encompassing scanning electron microscopy, Fourier-transform infrared spectroscopy, and gas chromatography-mass spectrometry. Our results reveal a remarkable preservation of the chemical integrity of industrial TNT, even in the presence of thermal stress and direct steel contact. Although superficial changes were observed in the TNT's appearance, all analytical data consistently demonstrated the maintenance of its chemical composition. Notably, the sole change in composition was attributed to the presence of degradation products associated with the alkyd paint coating, rather than intrinsic TNT degradation. These findings underscore the negligible impact of degradation processes on TNT in scenarios involving the solid-phase thermal stress of TNT in direct contact with metal, significantly enhancing our understanding of TNT safety when packaged within steel artifacts—a common context in military ammunition.

A positional isomer of LLM-116: N—NO2 moiety enhancing the laser ignition combustion performance of nitrogen-rich energetic materials

It has long been a driving force in the development of energetic materials to hunt for novel energetic materials (EMs) with high energy and low sensitivities. Recently, the combination of nitrogen-heterocycles and NNO2 moiety could generate novel energetic derivatives with high energy content and low sensitivity benefiting from the high heat of formation and abundant hydrogen bonding interactions. The critical role of isomerism strategy in tuning the laser ignition combustion performances of EMs is rarely mentioned in the chemical enterprise, although some researches reveal that isomerism strategy has significant effects on their thermal behaviors, mechanical sensitivity and detonation performance. In this work, the positional isomerism of nitramine-pyrazole was investigated, and 3-nitramine-4-nitropyrazole and a series of energetic derivatives were synthesized and well characterized. Their physical properties, energy performance, as well as laser-ignited combustion performance, were further explored. The experimental results showed that all compounds possess excellent detonation pressure, and detonation velocity (P: 26.5∼30.4 GPa, D: 7876∼8377 m·s−1), which were much better than those of trinitrotoluene (TNT) (P: 19.5 GPa and D: 6881 m·s−1). Moreover, all of the resulting energetic derivatives exhibited low mechanical sensitivities (IS>40 J). Interestingly, they also had excellent laser ignited combustion properties owing to the NNO2 moiety attached to nitropyrazole backbone.

The interplay of casing material and detonation wave shock parameters in steel witness plate dent formation

This study uses both experimentation and simulation to investigate how varying casing material around cylindrical Composition-B charges affects witness plate response and diagnoses the cause of the differences in the dents produced. Through experimentation, it was found that consistent dents are produced from repeated tests and characteristically different dents are produced by charges with different casing material. Charges cased in viscoelastic materials produced shallower dents than those without casing. Simulation was validated against the experimental dents, and the detonation wave parameters were measured for 25 differently cased charges: 15 metals and 10 polymers. Regression fit relationships were derived relating dent parameters to casing density, casing impedance, casing tensile strength, detonation pressure, detonation velocity, impulse, and time of arrival. Specifically, it was found that the dent volume was negatively correlated with the detonation velocity and the impulse of the detonation wave was negatively correlated with dent depths across the charge. The density of the casing material was shown to be linked to the width of the witness dents. Additional dent tests were simulated for trinitrotoluene (TNT) charges cased in a single polymer and a single metal. The relationships derived for Composition-B were adjusted to fit TNT using TNT equivalency and calculated the measured detonation wave values to within 10% accuracy. Finally, it was concluded that the measurable distinctions observed in the witness dents were not a result of the casing material itself, but of the changes in the detonation wave caused by its interaction with the casing material.

Motion measurements of explosive shock waves based on an event camera

Shock wave measurement is vital in assessing explosive power and designing warheads. To obtain satisfactory observation data of explosive shock waves, it is preferable for optical sensors to possess high-dynamic range and high-time resolution capabilities. In this paper, the event camera is first employed to observe explosive shock waves, leveraging its high dynamic range and low latency. A comprehensive procedure is devised to measure the motion parameters of shock waves accurately. Firstly, the plane lines-based calibration method is proposed to compute the calibration parameters of the event camera, which utilizes the edge-sensitive characteristic of the event camera. Then, the fitted ellipse parameters of the shock wave are estimated based on the concise event data, which are gained by utilizing the characteristics of the event triggering and shock waves’ morphology. Finally, the geometric relationship between the ellipse parameters and the radius of the shock wave is derived, and the motion parameters of the shock wave are estimated. To verify the performance of our method, we compare our measurement results in the TNT explosion test with the pressure sensor results and empirical formula prediction. The relative measurement error compared to pressure sensors is the lowest at 0.33% and the highest at 7.58%. The experimental results verify the rationality and effectiveness of our methods.

On the glass transition temperature of TNT

In prior work (N. Shamim, Y. P. Koh, S. L. Simon and G. B. McKenna, "The glass transition of trinitrotoluene (TNT) by Flash DSC," Thermochimica Acta,620, 36–39 (2015)) results for the glass transition temperature Tg of TNT based on measurements using a rapid chip calorimeter were reported. In that work a silver paste was used to contain the liquid TNT on the chip sensor. In the present work we show that there was an interaction between the paste and the TNT that cause the reported Tg to be approximately 10 °C higher than what we find for the material when placed directly on the chip calorimeter sensor. The reasons for the differences in Tg values and similarities in the glassy fragility index m from the different sample preparations are presented and discussed.

Near-infrared spectroscopy combined with deep convolutional generative adversarial network for prediction of component content in melt-cast explosive

Rapid and nondestructive prediction of component content is the key to improve industrial production efficiency. However, limited data sets also result in low generalization capabilities of the model, and it is time-consuming to obtain a large amount of content reference values and costly. Here, near infrared (NIR) spectroscopy technique combined with deep convolutional generated countermeasure network (DCGAN) was used to predict the trinitrotoluene (TNT) content of the melt-cast explosive. DCGAN was used to simultaneously extend its spectral data and content data. After several iterations, fake data were produced, which was very similar to the experimental data. The partial least squares (PLS) regression model was established and the performance was compared before and after data enhancement. The results showed that this method not only improved the performance of regression model, but also solved the problem of requiring large number of training data.

Development of Anti-TNT@Cu-BTC MOF thin film using drop caste method for trinitrotoluene (TNT) sensing

Antibody functionalised Cu-BTC MOF thin film was prepared using drop-casting method on indium tin oxide (ITO) coated glass substrate for trinitrotoluene (TNT) sensing under certain experimental conditions. Initially, APTES functionalization on ITO substrate using EDC-NHS chemistry was carried out, after which biofunctionalization of Anti-TNT on Cu-BTC MOF (1,3,5-tricarboxylic acid as an organic linker and copper ions as metal) thin film was carried out. Each step of sensor fabrication was characterised by the X-ray diffraction, microscopic and spectroscopic techniques. The interaction of one layer with another is confirmed with the help of FTIR and EDX. ITO substrate modification increases resistance at each stage from 1.29 to 3.3 KΩ. This modified substrate used as a working electrode during the sensing experiment. Afterward, response cum detection of 2,4,6-trinitrotoluene (TNT) in the 0.1 ppm to 0.6 ppm range has been noted by impedance method using three electrode systems of an electrochemical workstation. Host-guest interaction cum mechanism between TNT antibody functionalised APTES@Cu-BTC and TNT analyte has been observed which origins change in their resistance/impedance. The variation in resistance is directly proportional to the concentrations, exhibiting a strong linear relationship with 0.9702 value for R2. We find out that the presence of TNT antibody increases the specificity of TNT sensing and minimizes cross-reactivity with unknown/other interfering compounds. The concentration–response graph shows a 0.04 ppm limit of detection at room temperature.

Microecological characteristics of water bodies/sediments and microbial remediation strategies after 50 years of pollution exposure in ammunition destruction sites in China

The effects of long-term ammunition pollution on microecological characteristics were analyzed to formulate microbial remediation strategies. Specifically, the response of enzyme systems, N/O stable isotopes, ion networks, and microbial community structure/function levels were analyzed in long-term (50 years) ammunition-contaminated water/sediments from a contamination site, and a compound bacterial agent capable of efficiently degrading trinitrotoluene (TNT) while tolerating many heavy metals was selected to remediate the ammunition-contaminated soil. The basic physical and chemical properties of the water/sediment (pH (up: 0.57–0.64), nitrate (up: 1.31–4.28 times), nitrite (up: 1.51–5.03 times), and ammonium (up: 7.06–70.93 times)) were changed significantly, and the significant differences in stable isotope ratios of N and O (nitrate nitrogen) confirmed the degradability of TNT by indigenous microorganisms exposed to long-term pollution. Heavy metals, such as Pb, Zn, Cu, Cd, Cs, and Sb, have synergistic toxic effects in ammunition-contaminated sites, and significantly decreased the microbial diversity and richness in the core pollution area. However, long-term exposure in the edge pollution area induced microorganisms to use TNT as a carbon and nitrogen sources for life activities and growth and development. The Bacteroidales microbial group was significantly inhibited by ammunition contamination, whereas microorganisms such as Proteobacteria, Acidobacteriota, and Comamonadaceae gradually adapted to this environmental stress by regulating their development and stress responses. Ammunition pollution significantly affected DNA replication and gene regulation in the microecological genetic networks and increased the risk to human health. Mg and K were significantly involved in the internal mechanism of microbial transport, enrichment, and metabolism of TNT. Nine strains of TNT-utilizing microbes were screened for efficient TNT degradation and tolerance to typical heavy metals (copper, zinc and lead) found in contaminated sites, and a compound bacterial agent prepared for effective repair of ammunition-contaminated soil significantly improved the soil ecological environment.

Structural evolvement of 1-methyl-3,4,5-trinitropyrazole at high pressure

Explosives, a type of energetic material (EM), face a high-pressure environment in the detonation process or under shock conditions. Determining their high-pressure behavior is critical to their explosion and safety. 1-Methyl-3,4,5-trinitropyrazole (MTNP), a carrier of melt-cast explosives, exhibits the potential for replacing trinitrotoluene (TNT). However, there is limited knowledge about its structural evolvement at high pressure. Using a diamond anvil cell (DAC), this study investigated the structural variation of MTNP through in situ high-pressure synchrotron angle-dispersive X-ray diffraction (ADXRD) experiments and Raman measurements. As evidenced by the results, MTNP underwent phase transition at 8.7 GPa and amorphization at 15.3 GPa due to high pressure. Through the analysis of first-principles calculations and Raman spectra, this study proposed the mechanisms behind the changes in MTNP at high pressure. Furthermore, this study systematically explored the structural evolvement of MTNP and the evolution of its weak intermolecular interactions at high pressure, gaining further understanding of MTNP's detonation and safety.

Canine detection of explosives under adverse environmental conditions with and without acclimation training.

Canines are one of the best biological detectors of energetic materials available; however, canine detection of explosives is impacted by a number of factors, including environmental conditions. The objectives of this study were: 1) determine how canine detection limits vary when both the canine and odorant are tested in varying temperature and humidity conditions (canine and odor interactive effects); and 2) determine if an acclimatization plan can improve detection limits in an adverse environmental condition. Eight working line canines were trained to detect four energetics: prill ammonium nitrate (AN), Composition 4 (C4), trinitrotoluene (TNT) and double base smokeless powder (SP). In Experiment 1, canines completed a 3-alternative forced choice 3-down-1-up staircase threshold assessment in five environmental conditions: 40°C and 70% relative humidity (RH), 40°C and 40% RH, 0°C and 90% RH, 0°C and 50% RH and 21°C and 50% RH. Canines showed a 3.5-fold detection limit increase (poorer detection) for C4 in 40°C and 70% RH compared to their detection limit at 21°C and 50% RH. In Experiment 2, the eight canines were split into two groups (n = 4), control and acclimation groups. The control group completed the threshold assessment for C4 at 21°C and 50% RH each day for 20 days, with 5 minutes of petting prior to testing. The acclimation group completed the same assessment daily starting at 21°C and 50% RH but temperature and RH were incremented daily over the course of 6 days to the 40°C and 70% RH condition. After the initial six days, the acclimation group completed daily assessments at 40°C and 70% RH condition for the remainder of the experiment. All acclimatization group canines started their session with 5 minutes of toy or food retrieves. Detection limits for C4 for all dogs were tested in 40°C and 70% RH on day 11 and day 22. The acclimatization plan improved detection limits in the 40°C and 70% RH condition for C4 compared to the non-acclimated group. In this set of experiments, canine detection limits for four explosive odorants were found to vary based on environmental condition and were mostly driven by impacts on the canine rather than odor availability. The acclimatization plan did result in lower detection limits (i.e., increased performance). Future work should determine what factor (exercise or environmental exposure) is more effective in acclimatization for odor detection work.

Implementing of Fourier Deconvolution Multiplexing to Fast Polarity Switching Miniaturized Ion Mobility Spectrometer.

Ion mobility spectrometry (IMS) is a reliable and sensitive technique for the detection and analysis of compounds at the trace level. Depending on the chemical composition of the sample, compounds may be positively or negatively charged to form different polarity ions and detected in positive or negative polarity of the electric field. In order to detect multiple threats simultaneously with miniaturized devices, using a single detection unit to achieve high resolving power and high sensitivity is important. In this work, a miniaturized drift tube with fast polarity switching capabilities integrated with Fourier deconvolution multiplexing techniques is proposed for the first time as a means to improve the performance of ion mobility spectrometry. The sensitivity and resolving power are improved compared to traditional polarity switching signal averaging data acquisition methods. The displayed device had a high resolving power up to 52 at a drift length of 41 mm and a drift tube voltage of 2 kV. Trinitrotoluene (TNT), methamphetamine (MA), benzene, toluene, methyl tert-butyl ether (MTBE), acetic acid, and methylene chloride were evaluated using the proposed fast polarity switching multiplexing spectrometer and exhibited satisfied performance.

Numerical study on perforation damage and fragmentation of reinforced concrete slab under close-in explosion

Reinforced concrete (RC) structure is prone to suffer localized damage when exposed to close-in explosions. Spalling damage might occur due to the reflected tensile stress wave exceeding the concrete dynamic tensile strength. When the blast wave is intensive enough, it can also cause significant crushing damage on the contact surface, potentially leading to perforation when the crushing depth aligns with the spalling depth. This perforation/spalling damage can generate a large number of secondary fragments with high ejecting velocities. Additionally, the blast wave might pass through the perforation hole and cause further acceleration of the secondary fragments. In the author’s previous study, an ALE-FEM-SPH numerical model was established and validated with the existing testing data for the prediction of spalling damage as well as fragment sizes and velocities. As a continuous work, this study conducts numerical simulations to predict the perforation damage and fragmentation under higher-intensity blast loading. The results including centre perforation hole, spalling area on back surface, fragment ejecting velocities, fragment landing distance and fragment characteristics distributions are reported and studied. The acceleration effect on the secondary fragments by the traversed blast wave that further carries the fragments flying is also investigated. The numerical results show that using the scaled distance Z might not reliably quantify the perforation/spalling damage under close-in cylindrical TNT explosion. Given the identical scaled distance, the scenarios with different combinations of charge weight and standoff distance can result in large variations up to 300% in the predictions of damaged area and 50% for the maximum fragment ejecting velocities, respectively. A scaled blast parameter Z* is suggested and the empirical formulae are proposed for better quantification of the damaged area of RC slab as well as the fragment velocity and kinetic energy under close-in cylindrical TNT explosions.

Explosion power evaluation based on the energy absorption characteristics of expansion tube structure

With the rapid advancement of the new generation of ammunition, the evaluation of the explosion power has received worldwide attention. To assess the power of blast waves generated by explosives, an explosion power evaluation method, based on analyzing the energy absorption characteristics of an expansion tube structure (ETS), is proposed in this paper. Explosion experiments and numerical simulations are carried out to investigate the energy absorption characteristics of the ETS under blast loading, and a verified theoretical model is developed to predict the energy absorption per unit area (EAUA) of the ETS. The parametric studies demonstrate a quadratic positive correlation between the EAUA of ETS and the explosive mass/(standoff distance)2, as well as a linear correlation with the reciprocal of areal density of the ETS. However, the effect of equivalent strength of the ETS on the EAUA is less significant. Furthermore, an explosion power model is established using dimensional analysis. The evaluation errors of this model in estimating explosive mass are -11.34 % to 14.67 % when compared with the actual mass of the explosive trinitrotoluene (TNT), and it also shows errors of -13.94 % to 0.97 % when compared with the explosive mass estimated through free field overpressure sensors, which all fall within the range of ±15 %, demonstrating that the proposed method meets the accuracy requirements for explosion power evaluation. This research provides a novel and accurate methodology for evaluating the power of ammunition in explosion field, especially for testing in extreme conditions.

Exploring the thermal decomposition and detonation mechanisms of 2,4-dinitroanisole by TG-FTIR-MS and molecular simulations.

2,4-dinitroanisole (DNAN), an insensitive explosive, has replaced trinitrotoluene (TNT) in many melt-cast explosives to improve the safety of ammunition and becomes a promising material to desensitize novel explosives of high sensitivity. Here, we combine thermogravimetric-Fourier transform infrared spectrometry-Mass spectrometry (TG-FTIR-MS), density functional theory (DFT), and ReaxFF molecular dynamics (MD) to investigate its thermal decomposition and detonation mechanisms. As revealed by TG-FTIR-MS, the thermal decomposition of DNAN starts at ca. 453 K when highly active NO2 is produced and quickly converted to NO resulting in the formation of a large amount of Ph(OH)(OH2)OCH3+. DFT calculations show that the activation energy of DNAN is higher than that of TNT due to the lack of α-H. Further steps in both thermal decomposition and detonation reactions of the DNAN are dominated by bimolecular O-transfers. ReaxFF MD indicates that DNAN has a lower heat of explosion than TNT, in accordance with the observation that the activation energies of polynitroaromatic explosives are inversely proportional to their heat of explosion. The inactive -OCH3 group and less nitro groups also render DNAN higher thermal stability than TNT.

Synthesis of C-C bonded trifluoromethyl-based high-energy density materials via the ANRORC mechanism.

A trifluoromethyl group substituted C-C bonded nitrogen rich energetic material 3-(3-nitro-1H-pyrazol-4-yl)-5-(trifluoromethyl)-1,2,4-oxadiazole (4), its hydroxyl amine (5) and 3,6,7-triamino-7H-[1,2,4]triazolo[4,3-b][1,2,4]triazol-2-ium (6) salts and hydrazinium 5-(3-nitro-1H-pyrazol-4-yl)-3-(trifluoromethyl)-1,2,4-triazol-1-ide (7) were synthesized and fully characterized using infrared spectroscopy (IR), multinuclear magnetic resonance (NMR) spectroscopy (1H, 13C, and 19F), high-resolution mass spectrometry (HRMS), elemental analysis (EA) and differential scanning calorimetry (DSC) studies. Furthermore, compounds 4 and 7 were confirmed using single-crystal X-ray diffraction studies (SC-XRD). All compounds possess good density (1.70-1.80 g cm-3), detonation velocity (6432-7144 m s-1), pressure (16.38-20.31 GPa), and thermal stability (>170 °C). They are insensitive towards mechanical stimuli, impact (IS > 35 J) and friction (FS > 288 N). Overall, due to their balanced performance, these compounds can be a better replacement for presently used explosives such as trinitrotoluene (TNT).

Detection of nitro-aromatics using C5N2 as an electrochemical sensor: a DFT approach.

Nitroaromatics impose severe health problems and threats to the environment. Therefore, the detection of such hazardous substances is essential to save the whole ecosystem. Herein, the C5N2 sheet is used as an electrochemical sensor for the detection of 1,3-dinitrobenzene (1,3-DNB), trinitrotoluene (TNT), and picric acid (PA) using the PBE0/def2SVP level of theory as implemented in Gaussian 16. The highest interaction energy was observed for the picric acid@C5N2 complex. The trend in interaction energies for the studied system is PA@C5N2 >TNT@C5N2 >1,3-DNB@C5N2. The studied systems were further analysed by qualitative and quantitative analyses to determine the interactions between the nitroaromatic analytes and the C5N2 sheet. Electronic properties of all analytes@C5N2 complexes have been examined by NBO, EDD, FMO and DOS analysis. QTAIM analysis depicts the stronger non-covalent interactions for the PA@C5N2, which shows consistency with interaction energy and NCI analysis. Furthermore, NBO and FMO analyses show that the C5N2 substrate exhibits high sensitivity and selectivity towards the picric acid compared to TNT and 1,3-DNB nitroaromatics. EDD and DOS analyses are in agreement with NBO and FMO analyses. Furthermore, the recovery time of the studied system has been computed to determine the efficiency of C5N2 material as an electrochemical sensor. Overall, the results show that carbon nitride can be a good sensor for the detection of nitroaromatics.

Effect of Obliquely Directed Brick TNT Explosive on Slab Response under Contact Explosion

To design defense infrastructures and facilities, available prominent resources namely UFC 3-340-02, TM 5-1300, ASCE/SEI 59-11 and IS 4991, primarily consider test results from spherical explosives detonations whereas most of the explosives used in warfare and industrial/conventional operations have cylindrical/brick geometric form. Available research works in the literature considering various aspect ratios of cylinder TNT with its longitudinal axis perpendicular to the slab and of brick TNT having its length parallel to the supports and with its length and breadth in contact with the one-way slab, demonstrate that out of the three geometric forms (cylinder, sphere, and brick) of the explosive of the same mass; cylindrical explosive generates maximum pressure and the brick explosive produces the minimum. The authors discern that the obliqueness of the brick/cylindrical explosive with reference to the boundary condition of the slab influences the energy distribution and corresponding slab damage. In this paper, the effect of obliquely directed brick TNT explosive on slab response under contact explosion is examined in Abaqus software with a focus on comparing the slab damage and other responses with varying obliqueness of the explosive from 0° to 90° with increments of 22-1/2 degree. The numerical findings of the brick explosive having its length aligned with the slab supports demonstrate a strong correlation with the experimental results. The findings indicate that the maximum reflected pressure varies with the obliqueness of the brick explosive and consequently affects the slab damage including perforation size and geometry.

Experimental study of the coupled damage characteristics of a large-scale hull girder subjected to an underwater near-field explosion

This paper presents the design and testing of a 10 m box-shaped hull girder model to investigate the overall response characteristics and damage modes of a warship subjected to an underwater near-field explosion. A 100 g trinitrotoluene (TNT) charge was detonated right below the midspan or quarterspan of the girder. On this basis, the structure strain, shock environment, and displacement of the girder were obtained under varying conditions, including the explosion depths and positions of attack. In the study, the coupling motion and frequency response characteristics between the explosion bubble and the hull girder were analyzed. The basic conditions for the occurrence of a whipping response or sagging damage to the hull girder were proposed. The experimental results showed that the girder and the bubble could easily exhibit a coupled resonance when the frequency of the explosion bubble pulsation is close to the first wet frequency of the girder. Also, a bending deformation or an overall damage is more likely to occur when the underwater explosion (UNDEX) happened directly below the midspan of the girder in comparison to other explosions at different attack positions. It was found that the structural damage is mainly concentrated in the middle of the 1/5 girder length region.