The sensitivity of PBX 9501 and PBX 9502 to milling and sawing

Date

2022-05

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Abstract

Explosive driven pulsed power research benefits from modern polymer-bonded high explosives (HE). In practical application, high precision in the dimensional shape is required, and high machining speeds are desired. The limits of machining speed, driven mainly by the thermal response of the energetic material, are investigated. Specifically, the thermal response of PBX 9501 (95% HMX, 2.5% Estane, 2.5% BDNPA-F) and PBX 9502 (95% TATB, 5% Kel F-800) under conventional milling and sawing methods is examined. The presented work focuses on face milling performed with dry machining on a CNC, remote-controlled milling machine. The primary parameters of interest are the spindle speed (RPM), feed rate (IPM), step size (% dia.), depth of cut (inches), and endmill diameter (inches). The temperature of the system is monitored via high-speed infrared (IR) videography and near the cutting interface with a K-type thermocouple inserted into the endmill’s through-coolant channel. Operational forces and torques are recorded by a 6-axis force sensor mounted beneath the HE samples. An experimental setup for sawing into PBX is also presented. A dual-column horizontal band saw has been modified for remote control operations. Similar to the milling setup, the temperature of the system is measured using a high-speed IR camera and K-type thermocouples. Forces and torques are measured using a 6-axis force sensor mounted beneath the HE samples, with a fixed rail mounted in between the HE and the force sensor to allow the cutting “slice” thickness to be adjusted with each test. An empirical relationship between temperature and the milling parameters is presented. Overall, milling regimes exist outside of DOE-STD-1212-2019 for which milling temperatures remain well below the HE critical temperatures.


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Keywords

Machining, High Explosives, PBX, Milling, Sawing

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