Related Experiment Video
Updated: Oct 8, 2025

Research and Development of High-performance Explosives
Published on: February 20, 2016
Shock Pressure Dependence of Hot Spots in a Model Plastic-Bonded Explosive
Belinda P Johnson1, Xuan Zhou1, Dana D Dlott1
1School of Chemical Sciences and Fredrick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.
Abstract:
Shock initiation of plastic-bonded explosives (PBX) begins with the formation of so-called "hot spots", which are energetic reactions localized in regions where the PBX microstructure concentrates the input shock wave energy. We developed a model PBX system to study hot spots which consists of a single crystal of the high explosive HMX (cyclotetramethylene-tetranitramine) embedded in a transparent polyurethane binder (J. Phys Chem. A, 2020, 124, 4646-4653). In the current work we use this model system to study the influence of input shock pressure (12-26 GPa) on hot spot generation using micrometer-resolved high-speed imaging and nanosecond-resolved optical pyrometry. By shocking ∼100 HMX single crystals (HMX-SC), two distinct shock pressure thresholds were observed. The threshold for producing single hot spots in some crystals was 15 GPa. At 23 GPa, hot spot density was sufficiently high to lead to rapid deflagration of the entire HMX-SC. It takes about 25 ns after the shock passes for the hot spots to appear to our visible-light detection apparatus which has a noise floor at about 2000 K. That indicates the shock produces nascent hot spots that undergo a thermal explosion that reaches temperatures >2000 K in 25 ns. The initial hot spot temperature is roughly 3800 K which settles down to 3400 K, the adiabatic flame temperature of HMX. The higher initial temperature is attributed to release of stored interfacial strain energy produced by the shock. An initial estimate for the velocity of the flame front originating at an HMX hot spot is 550 m/s.
Related Concept Videos
Plastic Behavior
Members Made of Elastoplastic Material
As the bending moment...
Sound as Pressure Waves
The pressure fluctuation depends on the difference in displacements between the successive points in the...
Plastic Deformations
Plastic Deformations of Members with a Single Plane of Symmetry
Stress-Strain Diagram - Brittle Materials

