Bridgewire Research Articles

Design, preparation and firing characterization of PCB-EBW

Exploding Bridge Wire (EBW) is a special actuator that drives high-temperature and high-pressure plasma. To address the issues of low efficiency and high cost in the preparation process of EBW detonators, an EBW chip based on Printed Circuit Board (PCB) technology was designed and studied. By utilizing a specially designed "S"-shaped transition region and using copper (Cu) as the bridge wire material, the PCB method has enabled batch production of the PCB-EBW device. Four different types of PCB-EBW chips were constructed by designing bridge wires of varying lengths. Subsequently, electro-thermal simulations, electrical explosion performance studies, and shock wave simulations were conducted on the PCB-EBW. It is inferred from the research findings that the main factor triggering the explosive detonation of the PCB-EBW chip is the coupling effect between the high-temperature plasma generated by the electrical explosion and the electrical explosion shock wave. The speculation on the working mechanism of the PCB-EBW was validated by igniting PETN, with the minimum firing voltage determined to be 550 V (for a bridge wire length of 200 μm). This novel EBW design expands the application prospects and provides new insights into the mechanism of EBW for future research.

A stochastic modeling method for three-dimensional corrosion pits of bridge cable wires and its application

ABSTRACT Cables have usually served as critical and vulnerable structural components in long span cable-supported bridges. Cable inspections revealed that corrosion, fatigue or coupled corrosion-fatigue were the ones of the main failure mechanisms. This paper proposed a stochastic modelling method for three-dimensional (3-D) corrosion pits of high-strength bridge wires, which can be applied to rapid fatigue life evaluation according to mass loss caused by surface corrosion pits of bridge wires nondestructively. High-strength steel wire specimens dismantled from the cable-stayed bridge served for 15 years were scanned to obtain the original surface corrosion data. The spatial position coordinate of corrosion pits were considered as random variable and can be well fitted by uniform distribution. While the number of corrosion pits can be fitted with generalized extreme value (GEV) distribution. The uniform corrosion depth du, which can be equivalent to mass loss rate, was calculated as the input corrosion parameter for 3-D corrosion pit modelling. The maximum pitting depth dmax for the steel wire was found to be associated with du. The geometric parameters for individual corrosion pits were recognized as pit depth d, depth-to-width ratio d/b, and aspect ratio b/a, which were fitted with different probability distributions. What follows is 3-D spatial corrosion pits simulation based on the individual corrosion parameter that were sampled and combined from the corresponding probabilistic distributions. Hereafter, fatigue life evaluation of corroded wires was conducted based on equivalent surface defect method and compared with the experimental results, verifying the effectiveness of the proposed modelling approaches.

Analysis of the Electromagnetic Effect Mechanism of EED under Continuous Wave Radiation

The electromagnetic radiation sensitivity of the electric explosive device (EED) and its installed use state is closely related to the size of the equipment and radiation field strength constraints. The use of the traditional all-level electromagnetic radiation method for the effect of the actual installed EED test in the electromagnetic environment simulation encountered a technical bottleneck. The microwave band is difficult to effectively assess through the current standing wave distribution and skin effect. The temperature rise of the EED bridge wire has no relationship with the frequency of the electromagnetic wave. In this paper, through the analysis of the electromagnetic effect mechanism of the EED, the coupled power model of electromagnetic irradiation of the EED is obtained, and the relationship between the temperature rise of the bridge wire of the EED and the electric field strength model is established. Under the action of high-frequency continuous waves, the electromagnetic effect of the device is tested to verify the correctness of the mechanism analysis of the electromagnetic effect of the device under the action of continuous waves. The results provide crucial technical support for the electromagnetic protection of the device under the harsh electromagnetic environment of the battlefield.

Wavefield boundary interactions in a multi-domain environment—Experimental results

Acoustic and seismic signals may be generated and received in land, air, and water domains within a multi-domain environment such as a littoral (nearshore) zone. As the energy moves between domains, the waves undergo complex transformations at the media boundaries. Separate consideration of each physical domain (land, air, water) leads to an incomplete understanding of the full cross-domain wavefield, leading to significant challenges in interpreting signals and creation of accurate models that realistically couple multiple domains. To address this knowledge gap, a team at the US Army Engineer Research and Development Center constructed a simplified, uniform levee to enable the measurement of signals that had passed through undisturbed boundaries. Sensor types were medium-specific, with microphones in the air, hydrophones in the water, and accelerometers in the soil. Using electric bridge wire detonators (EBW’s), impulsive signals were generated in each medium type and measured on sensors in all three media. This presentation begins with an overview of the experimental design, discusses the medium-specific measurement results, and concludes with a discussion of joint multi-domain data analysis results. Approved for public release: distribution is unlimited.

Imaging high jitter, very fast phenomena: A remedy for shutter lag.

Dielectric breakdown is an example of a natural phenomenon that occurs on very short time scales, making it incredibly difficult to capture optical images of the process. Event initiation jitter is one of the primary challenges, as even a microsecond of jitter time can cause the imaging attempt to fail. Initial attempts to capture images of dielectric breakdown using a gigahertz frame rate camera and an exploding bridge wire initiation were stymied by high initiation jitter. Subsequently, a novel optical delay line apparatus was developed in order to effectively circumvent the jitter and reliably image dielectric breakdown. The design and performance of the optical delay line apparatus are presented. The optical delay line increased the image capture success rate from 25% to 94% while also permitting enhanced temporal resolution and has application in imaging other high-jitter, extremely fast phenomena.

Measurement, calibration, and verification on the critical ignition temperature of hot bridge wire electro-explosive device

To address the problem of the difference in temperature between the exposed and amorce-filled state of the bridge wire in the fiber optic thermometry, this paper proceeds from a mathematical model of the temperature rise of the hot bridge wire electro-explosive device (EED), the relationship between the critical ignition temperature and the current of hot bridge wire EED is discussed. Combining thermal ignition theory, the technique of measurement and calibration the critical ignition temperature of hot bridge wire EED is proposed, and the technique is validated by injection versus radiation. The results show that the critical ignition temperature of the tested hot bridge wire EED obtained by testing and calibration is 337.53 °C. The 50% ignition field strength of the hot bridge wire EED under radiation conditions obtained by the up-and-down method test is 1271 V m−1, while the equivalent ignition field strength determined from the critical ignition temperature under the same radiation conditions is 1345 V m−1, the error between the two is only 0.49 dB, which demonstrates the high accuracy of the proposed measurement and calibration technique.

Study on calibration method of electrical parameter tester for industrial digital electronic detonator

By the end of 2022, the civil explosive industry has realized the full use of industrial electronic detonators, which has promoted the upgrading of the electrical parameter tester of industrial electronic detonators. The original calibration method can no longer meet its traceability requirements. According to the working principle of the industrial digital electronic detonator electrical parameter tester, this paper studies the calibration method of the delay time, DC resistance (firing bridge wire resistance), DC current, internal crystal oscillator signal (frequency) and other parameters, simulates and assembles a set of measuring standard device, and analyzes the sources of uncertainty of the industrial digital electronic detonator electrical parameter tester, which is solved the problem of quantity value traceability of industrial digital electronic detonator electrical parameter tester in civil explosive industry.

Simulation and experimental on sensitive criterion of hot bridge wire EED

To address the problem of complex process and inaccurate results in the simulation for the sensitivity of hot bridge wire electro-explosive devices (EEDs) which is caused by subjective factors in the sensitive criterion, this paper established a temperature rise model for the hot bridge wire EED first, then, through theoretical and numerical analysis, the sensitive criterion of hot bridge wire EED was proposed, and based on the sensitive criterion, the simulation process for the critical ignition current of hot bridge wire EED was given, finally, the correctness of the proposed sensitive criterion was verified by simulation analysis and experimental tests. The simulation results show that the critical ignition current of the tested EED under constant current condition is 182.6 mA and the ignition temperature is 481.52 °C, the maximum error between the ignition temperature under pulse excitation and that under constant current excitation is 7.75 %. The experimental test showed that the 50 % ignition current of the tested EED under constant current condition is 189.4 mA, with an error of only 0.32 dB from the theoretical calculation, demonstrating the correctness of the theoretical model and the sensitive criterion.

Simulation on correlation of pulse ignition sensitivity for hot bridge wire EED

To solve the problem of testing the sensitivity under electromagnetic pulse radiation for a hot bridge wire electro-explosive device (EED), this paper simulated and analyzed the correlation between the critical ignition current under steady and pulse excitation. The simulation results showed that, under single pulse excitation, the critical ignition current of the EED decreases with the increase in the pulse width, and the variation law can be divided into three pieces: adiabatic, transition, and constant; while under pulse train excitation, due to the thermal cumulative effect, the critical ignition current is related to both material properties and excitation parameters. By analyzing the simulation results and considering the thermal ignition theory, the mathematical model of the critical ignition current under pulse excitation was established, and the mathematical model showed that under pulse train excitation, the critical ignition current is relevant not only to the single pulse excitation critical ignition current, pulse period, and duty cycle, but also to the ratio of single pulse and steady excitation critical ignition current and the thermal time constant. It was verified that the errors between the theoretical values obtained from the mathematical model and the results obtained from the simulation were within 2.5%.

Design Method and Performance Study of Insensitive Bridge Wire

An insensitive “fishbone” bridge wire was designed by dividing the bridge wire into a heat collection zone and a heat dissipation zone, leading to the improved safety and reliability of initiating explosive devices. The surface temperature of the bridge wire was investigated by using finite element simulation. The performance of insensitive initiating explosive devices composed of bridge wire was analyzed by using resistance and ignition performance tests. The results show that the designed collector area of the bridge wire is the highest surface temperature during operation, initiating explosive devices consisting of insensitive “fishbone” bridge wires that meet the requirements of insensitivity.

Study on the relationship between the design parameters of bridge wire electric initiating devices and the electrothermal response curve

The parameter settings of the transient thermal response test conditions of bridge wire electric initiating devices are studied. The effects of bridge wire resistance parameters and charge pressure on the electrothermal response curve were explored. The results show that when the state of the bridge wire and the surrounding agents are basically the same, the electrothermal response curve can clearly reflect the difference in the resistance of the bridge wire. The larger the bridge wire resistance, the more sensitive the bridge wire to the electrical pulse, and the charging pressure parameters also have a significant impact on the electrothermal response curve. The smaller the charging pressure, the more sensitive the product electrothermal response. When the density of the agent is basically the same, the approximate response curve and parameter calculation results can be obtained.

Glowing contact in electrical fires: Experimental investigation and modeling on its heat intensity and thermal hazards

Glowing contact triggered by poor electrical contacts is a typical heat source. A fire accident shows that the glowing phenomenon lasted for 8 h before flashover. Thus, it is vital to study the electrical fire risks and fire mechanisms concerning glowing contact. In this research, temperature distribution of the glowing contact is measured. A glowing contact heat transfer model is proposed based on the finite element method. Finally, experiments of thermal hazards exerted by glowing contact on insulation layers are developed. Results show that the proposed model is consistent with experimental data. It is discovered that the temperature and overheating range will increase as the oxide bridge grows. At the boundary of the oxide bridge and unoxidized wires, a turn point temperature exists. It is attributed by the low heat conductivity of the copper oxide and the good thermal conductivity of copper wires. The insulation does not catch fire but undergoes intense pyrolysis, softening, bubbling, and carbonization within a length of approximately 30 mm. According to the fire case, it can be inferred that the bared copper conductors or carbonized insulations caused by glowing contact can trigger physical short or arc short prior to electrical fires.

Numerical simulation of the ignition law for a hot bridge wire electroexplosive device

Hot bridge wire electroexplosive devices (EEDs) are widely used as starting elements in aerospace and other fields. Their thermal ignition process and safety testing technology have always been a focus of research. In this paper, we construct a temperature rise model for a hot bridge wire EED by using the law of conservation of energy, and the temperature response of the bridge wire and the reagent is obtained. According to the theoretical and numerical analysis, the sensitive criterion for a hot bridge wire EED is given, and the simulation process for the critical ignition current is designed. Based on this process, the law of the influence of the bridge wire and reagent parameters on the ignition of a hot bridge wire EED was studied. The research results show that a first derivative of the reagent temperature with respect to the radial distance of greater than zero is a sensitive criterion for the ignition of a hot bridge wire EED with high accuracy. Compared with traditional numerical methods, the proposed process makes the acquisition of the critical ignition current more precise and programmable due to the use of sensitive criteria. In addition, the following significant features are noted: the critical ignition current first increases as the square root of the bridge wire radius and then linearly; the square of the critical ignition current increases linearly with the activation energy of the reagent; there is rapid exponential decay of the critical ignition current with increasing reagent combustion heat; asymptotic values are present. In engineering use, it is possible to conveniently design the ignition characteristics of a hot bridge wire EED by changing the radius of the bridge wire. This study serves as a foundational work for the safety testing of hot bridge wire EEDs and can provide theoretical guidance for the safety testing, actual production and use of hot bridge wire EEDs.

Determination of spin Hall angle in the Weyl ferromagnet Co2MnGa by taking into account the thermoelectric contributions

The spin Hall effects of various materials, including Weyl semimetals, have been studied by the spin absorption method with the nonlocal spin valve structures. Here, we study ${\mathrm{Co}}_{2}\mathrm{MnGa}$ (CMG) by using the standard spin absorption method. A considerable amount of thermoelectric signal superimposes on the inverse spin Hall signal in the measurement configuration: the applied electric current between the spin injector (permalloy) and bridge (copper) wires produces heating or cooling at the interface via the Peltier effect, which causes an out-of-plane temperature gradient in CMG. As a result, a voltage signal induced by the anomalous Nernst effect (ANE) of CMG comes into the inverse spin Hall signal. We quantitatively separate these signals by combining the experiment and a numerical simulation. About 75% of the detected signal is found attributable to the thermoelectric effects. The superposing thermoelectric contribution is a general and unavoidable problem in this method when the spin Hall materials exhibit ANE. After eliminating the thermoelectric signal, the spin Hall angle of CMG turns out to be $\ensuremath{\theta}=\ensuremath{-}0.09$ at room temperature.

Feasibility and Error Analysis of Using Fiber Optic Temperature Measurement Device to Evaluate the Electromagnetic Safety of Hot Bridge Wire EEDs.

Most studies assessing the safety of hot bridge wire EEDs employ temperature sensors that directly use the measurements of the temperature measurement device without analyzing the accuracy of the temperature measurement. This study establishes the response function of the exposed bridge and exposed bridge temperature rise system of hot bridge wire EEDs through the Rosenthal’s temperature rise equation and Laplace transformation as well as experimental tests, and through the response function, the response law and numerical characteristics of the two are compared and analyzed under four typical excitations. Under steady current injection and continuous-wave radiation, both exposed bridge and exposed bridge temperature measurement systems can reach thermal equilibrium, and the equilibrium temperature of both are the same. However, under pulse excitation, the temperature rise measurement value is significantly different from the actual value due to the large difference in response time of the exposed bridge (1 ms) and the exposed bridge temperature measurement device (0.82 s). Studies have shown that under steady current injection and continuous-wave radiation, temperature rise measurements can be directly applied to the safety assessment of hot bridge wire EEDs, while under pulsed conditions, temperature rise measurements cannot be directly applied.

Operability thresholds for thermally damaged EBW detonators

Operability thresholds that differentiate between functional RP-87 exploding bridge wire (EBW) detonators and nonfunctional RP-87 EBW detonators (duds) were determined by measuring the time delay between initiation and early wall movement (function time). The detonators were inserted into an externally heated hollow cylinder of aluminum and fired with current flow from a charged capacitor using an exploding bridge wire (EBW initiated). Functioning detonators responded like unheated pristine detonators when the function time was 4 μs or less. The operability thresholds of the detonators were characterized with a simple decomposition cookoff model calibrated using a modified version of the Sandia Instrumented Thermal Ignition (SITI) experiment. These thresholds are based on the calculated state of the PETN when the detonators fire. The operability threshold is proportional to the positive temperature difference (ΔT) between the maximum temperature within the PETN and the onset of decomposition (∼406 K). The temperature difference alone was not sufficient to define the operability threshold. The operability threshold was also proportional to the time that the PETN had been at elevated temperatures. That is, failure was proportional to both temperature and reaction rate. The reacted gas fraction is used in the current work for the reaction correlation. Melting of PETN also had a significant effect on the operability threshold. Detonator failure occurred when the maximum temperature exceeded the nominal melting point of PETN (414 K) for 45±5 s or more.

Equivalent Test Method for Strong Electromagnetic Field Radiation Effect of EED

The present study proposed the equivalent test method for the strong electromagnetic field radiation of electric explosive devices (EEDs) of the weapon equipment to satisfy the military requirements of the electromagnetic radiation safety test, as well as the evaluation of the electric ignition, the electric initiation ammunition, or missiles. Under stable conditions, the ignition excitation test and the bridge wire temperature increase test were performed to determine the ignition temperature of the EED. As radiated by the strong electromagnetic field, the relationship between the temperature increase of the bridge wire and the electric field intensity of the EED was developed based on the theoretical analysis and the experimental test. Given the ignition temperature of the EED, the radiation field intensity of the EED at 50% ignition was determined. As compared with the 50% ignition field intensity of the EED directly radiated by the strong electromagnetic field, an error less than 1 dB was caused. On that basis, the correctness of the equivalent test method was verified. Accordingly, this method was suggested to act as an effective method and technical means to test and evaluate the electromagnetic radiation safety of ammunition and missiles in unfavorable electromagnetic environments.

Deformation Law of Cold Drawing Process of High Strength Bridge Cable Steel

High-strength cable-steel bridge is the “lifeline” of steel structure bridges, which requires high comprehensive mechanical properties, and cold-drawing is the most important process to produce high-strength cable-steel bridge. Therefore, through the ABAQUS platform, a bridge wire drawing model was established, and the simulation analysis on the process of stress strain law and strain path trends for high-strength bridge steel wire from Φ 12.65 mm by seven cold-drawing to Φ 6.90 mm was conducted. The simulation results show that the wire drawing the heart of the main axial deformation, surface and sub-surface of the main axial and radial deformation occurred, with the increase in the number of drawing the road, the overall deformation of the wire was also more obvious non-uniformity. In the single-pass drawing process, the change in the potential relationship of each layer of material was small, and multiple inflection points appeared in the strain path diagram; the change in the seven-pass potential relationship was more drastic, which can basically be regarded as a simple superposition of multiple single-pass pulls.

Safe preparation of CuN3 for improved ignition performance of Ni-Cr bridge wire electric initiating explosive devices

The electric initiating explosive devices (EIEDs) are playing an increasingly important role in both military and civilian applications. With respect to good electrical conductivity and flexural strength, carbon paper can be endowed with primary explosive so that it serves as an independent module just like an ignition component in the EIEDs to satisfy the modular integration of EIEDs. But a traditional primary explosive cannot meet the need of sustainably developed devices. New energetic films need to be designed for EIEDs. The heat release and activation energy of the CA-CP film are 1402 J·g−1 and 104 kJ·mol−1, respectively. The electrostatic sensitivity of the CA film, whose E50 reaches up to 4.81 mJ, has been well improved due to its interweaved fibers. Moreover, the cuprous azide film could be successfully ignited under water after a hydrophobicity treatment. Herein, the CA-loaded carbon paper has been successfully integrated with the Ni-Cr bridge EIEDs for a greatly improved ignition performance, which will subsequently lead to a vast enhancement in the ability of EIEDs to ignite the secondary explosives or devices.

Experimental Investigation of the High-Temperature Performance of High-Strength Steel Suspension Bridge Wire

Abstract Quantification of the mechanical properties of suspension bridge main cables during fire hazards is a vital part of holistic safety assessment of infrastructure. While some researchers hav...