Engineering topics

Perry, William Lee

Publications and source records attributed to Perry, William Lee.

5 records

DOE OSTI2023

Microwave ignition systems with launcher affixed to or located within a gun spindle

Microwave ignition systems with a launcher affixed to or located within a gun spindle. Use of a planar, impedance matched system that include a launcher affixed to or located within a gun spindle and a receiver affixed the propelling charge, where the receiver is engineered and impedance matched to efficiently deposit energy into the receiving igniter material, may result in significantly better timing and reliability than conventional mechanical gun ignition systems and other microwave ignition systems. A pressure-tolerant feed through system can route the microwave energy to the inside of the breech.

Duque, Amanda Lynn↗

DOE OSTI2022

Toward a machine-guided approach to energetic material discovery

In this article, we trained a machine learning (ML) model to connect microstructural details of an energetic material formulation to its performance for the purpose of guiding the discovery of new explosive formulations. Our hypothesis was that the algorithm would robustly learn the training data and produce an accurate surrogate model. Specifically, the algorithm learned the relationship between details of the void size distribution (VSD), initiating shock pressure, and the energetic material performance. We used realistic constraints on the VSD and a range of cases were ingested by a physically informed reactive flow model working within a hydrodynamic solver running on high-performance computing resources. The ML algorithm produced a surrogate model that accurately predicted known test points around the parameter space. In addition to the utility of the model and the process used for its development, we noted interesting comparisons between what we, the authors—subject matter experts, would heuristically conclude from the training data and the surrogate model predictions. We detected nuanced details that were missed by the surrogate model; however, these details are not important to an energetic material formulator. We concluded that the algorithm did indeed robustly learn the training data and produce an accurate surrogate model. We further concluded that the surrogate model is a powerful tool to guide the formulator in the absence of subject matter experts and limited-access computing resources.

42 ENGINEERING↗

DOE OSTI2022

Novel method to control explosive shock sensitivity: A mesoscale study to understand the effect of thermally expandable microsphere (TEM) inclusions in high explosives (HE) microstructure

When the void content and/or void structure of a high explosive (HE) is altered by some means (i.e., bulk heating or mechanical damage), the shock initiation behavior of the material changes. The ability to precisely predict the change in shock sensitivity after an HE has undergone microstructural changes is a crucial capability in multi-scale reactive flow models. Here, we utilize thermally expandable microspheres (TEMs) as a dopant in a polymer bonded explosive (PBX) matrix to alter the shock initiation properties in a controlled fashion. Here, using a mesoscale modeling approach, we evaluated how a single TEM (before and after thermal expansion) behaves under shock compression, as well as how the matrix PBX in the direct vicinity of the TEM is affected. We first examined the effect of an unexpanded TEM in the explosive matrix and found that its presence does not significantly perturb the bulk flow and by extension will not affect bulk sensitivity. Next, we examined the effect of an expanded TEM and found that its presence significantly perturbs the flow via hydrodynamic jetting, which causes a secondary shock wave with a strength that exceeds that of the incident wave. Finally, we showed that this secondary shock interacts with the downstream porosity to ignite a larger fraction of the overall pore volume, commensurate with the secondary shock strength and the affected volume, increasing the global (bulk) shock sensitivity.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2020

Microwave ignition of energetic material housed within a gun

The systems and methods for microwave ignition of energetic material housed within a gun (e.g., primers and/or propellants) allow for the use of insensitive energetic materials and/or insensitive gas-generating materials in place of sensitive energetic materials relied upon by mechanical ignition systems. In some embodiments, the use of insensitive energetic materials and/or insensitive gas-generating materials increase the safety and reliability of guns that would otherwise need to depend on sensitive energetic material required by mechanical or laser ignition mechanisms. Additionally, in some embodiments, the systems and methods provide greater versatility with respect to the variety of energetic materials that may be employed within guns.

42 ENGINEERING↗

DOE OSTI2017

Electromagnetic enhanced ignition

Here, we investigate how EM radiation affects the thermal decomposition pathway in HMX. The experiment used an external heat source (CO 2 laser) to rapidly heat the surface of HMX and observe the response upon application of EM energy that, on its own, is not enough power to induce heating or ignition. We hypothesize that charged intermediate decomposition species and free radicals in the gas phase interact strongly with EM energy, leading to plasma formation. These gas phase species form as a result of HMX sublimation and decomposition, and will act as “virtual antennas” and strongly couple to EM energy. The rapid absorption of EM energy during this coupling event is observed in the measured reflected power data. Ignition and plasma formation were monitored using both visible and IR photodiode probes, as well as imaged using a high-speed video camera. These observations support the hypothesis that the presence of an EM field will perturb the thermal decomposition pathway of HMX, and cause ignition to occur at a lower temperature than what is predicted under typical thermal conditions. This intense interaction results in electrically excited molecules that propagate the energy and surpass the activation barrier for ignition before the predicted ignition temperature of the bulk sample has been reached. In conclusion, understanding the decomposition of energetic materials under the influence of EM energy is important to understand and predict material response under a variety of environmental conditions.

42 ENGINEERING↗