Characterisation and validation of the JWL equation of state parameters for PE4

• Published in: International journal of impact engineering 2022-06, Vol.164, p.104190, Article 104190
• Main Authors: Bornstein, Huon, Kuznetsov, Valerian, Lu, Jing-Ping, Stojko, Steven, Freundt, Jared
• Format: Article
• Language: English
• Subjects: Blast loading; Blast loads; Blasting (explosive); Cylex; Cylinders; Equations of state; Experiments; Explosions; Inverse modeling; JWL equation of state; Modelling; Near fields; Optical fibers; Parameters; PE4; Predictions
• ISSN: 0734-743X; 1879-3509
• DOI: 10.1016/j.ijimpeng.2022.104190

•CYLEX experiments were conducted to characterise the PE4 explosive.•The JWL parameters were determined via an empirical and inverse modeling approach.•Validated against near-field and mid-field experimental data.•Inverse modeling methodology provided the best fit to experimental data. This investigation focused on determining the Jones-Wilkins-Lee (JWL) equation of state (EoS) parameters for the Australian made explosive PE4-MC. Four cylinder expansion (CYLEX) experiments were conducted using the T-20 methodology with measurements of the time of arrival of the copper cylinder on the perspex plate made using optical fibres connected to an optical pulse timer. Three different model parameter fits were then generated from the CYLEX test data. These were based on; (1) Traditional least-squares fit of CYLEX data to JWL EoS and (2) Inverse modeling method using LS-DYNA and LS-OPT (two different fits). The three parameter sets were then compared in terms of the accuracy of their predictions against two sets of blast loading experiments. The first set of blast loading experiments evaluated the different parameter fits at a scaled distance (Z) of 1.77–2.55 m/kg1/3, representing a mid-field blast loading scenario while the second set of blast loading experiments represented a near-field blast loading scenario (Z = 0.08–0.1 m/kg1/3). The JWL EoS parameters which were derived using the standard fitting method from the CYLEX test data (CYLEX) were shown to provide accurate predictions (within 5% of experiments) in the near-field but under-predicted the peak reflected pressure in the mid-field by more than 20%. The best predictions across both the near and mid-field blast loading scenarios was provided by the two parameters sets (LS-OPT Final and LS-OPT Select), which were derived using an inverse modeling approach, with the LS-OPT Select set of parameters being the preferred option. Additionally, comparisons between the experimental data and predictions using the JWL EoS parameters for the US made C4 explosive indicated that the blast loading in the mid-field was similar between C4 and PE4-MC, which was consistent with the previous literature. However, in the near-field C4 was predicted to provide higher blast loadings. This highlights the importance of validating an explosives EoS across a range of different scaled distances.