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Equivalency is often used to enable calculations of overpressures and impulses for explosives other than TNT. Equivalent mass factors are available for far-field detonations but none are available for near-field detonations. These reported factors are associated with incident overpressure and impulse and assumed appropriate for reflected overpressure and impulse. Numerical studies of TNT-equivalent mass factors for four high explosives (PETN, Composition B, Pentolite and Tetryl) for incident and normally reflected peak overpressure and scaled impulse are presented for a wide range of scaled distance 0.06 ≤ Z ≤ 40 m/kg1/3. Emphasis is placed on near-field detonations for which no reliable factors are currently available.

The paper begins with a novel variational formulation of Duffing equation using the extended framework of Hamilton's principle (EHP). This formulation properly accounts for initial conditions, and it recovers all the governing differential equations as its Euler-Lagrange equation. Thus, it provides elegant structure for the development of versatile temporal finite element methods. Herein, the simplest temporal finite element method is presented by adopting linear temporal shape functions. Numerical examples are included to verify and investigate performance of non-iterative algorithm in the developed method.

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