Application of JWL parameters for low-density PETN in underwater explosive welding of aluminum-steel composite tubes

Low-density pentaerythritol tetranitrate (PETN, 0.4 g·cm-3) was selected as the welding explosive for underwater explosive welding of metal tubes due to its small critical diameter. Given the significant influence of welding parameters on weld quality, numerical simulations were used to determine the optimal conditions for aluminum-steel composite tube welding, which were experimentally validated. To accurately simulate the explosive behavior during welding, the parameters for the Jones-Wilkins-Lee (JWL) equation of state were derived from a cylinder test. In-situ photon Doppler velocimetry was employed to measure the expansion velocity histories of metal tubes in both cylinder tests and welding experiments. The underwater welding experiment achieved an impact velocity of 510 m·s-1 and a collision angle of 10.4°, with less than 5% deviation between simulated and experimental results, confirming the accuracy of the JWL parameters for low-density PETN. Both numerical and experimental approaches revealed a flat welding interface in the aluminum-steel composite tube, and microstructural observations aligned with simulation predictions. This study demonstrates that precise JWL parameters enable reliable prediction of welding parameters, offering an efficient methodology to optimize underwater explosive welding of metal tubes.