# Simulation slip-up leads to retraction of explosives paper

Applied Sciences has retracted a 2012 article by a researcher whose efforts to model a particular kind of explosion called a shaped charge proved to be a dud.

The paper, “Steady State Analytical Equation of Motion of Linear Shaped Charges Jet Based on the Modification of Birkhoff Theory,” was written by Seokbin Lim, a mechanical engineer in the Energetic Systems Research Group at  New Mexico Tech, in Socorro.

According to the abstract:

Birkhoff theory exhibits an analytical steady state liner collapse model of shaped charges followed by jetting process. It also provides the fundamental idea in study of shaped charges and has widened its application in many areas, including a configuration where the detonation front strikes the entire liner surface at the same time providing the α = β (liner apex angle α, and the liner collapse point angle β) condition in the literature. Upon consideration of the detonation front propagation along the lateral length of the core charge in LSCs (linear shaped charges), a further modification of the Birkhoff theory motivated by the unique geometrical condition of LSCs and the α = β condition is necessary to correctly describe the jetting behavior of LSCs which is different than that of CSCs (conical shaped charges). Based on such unique geometrical properties of LSCs, the original Birkhoff theory was modified and an analytical steady state LSCs model was built. The analytical model was then compared to the numerical simulation results created from Autodyn™ in terms of M/C ratio and apex angles in three different sized LSCs, and it exhibits favorable results in a limited range.

Except, not so favorable after all. Here’s the retraction notice:

The following article: doi:10.3390/app2010035 [1] has been retracted by the author due to problems in the hydrocode simulation configuration.

The paper aims to develop an analytical approach in calculation of the jet/slug velocity of typical linear shaped charges (LSCs) based on a rather simple modification of the conventional Birkhoff theory. In the context, the author uses a simple 2D simulation to prove the accuracy of the analytical calculation and to identify general characteristics of the proposed analytical method. However, later it was found that the author ignored the unique geometrical configuration of LSCs in simulations (properly addressable in 3D configuration), creating a questionable comparison between the analytical calculation and the simulation result; causing the retraction of the paper [1]. The author, however, confirmed that the analytical calculation does not contain any flaws. As an author, I take full responsibility for the retraction and any other errors in its contents.

That “any other errors” bit makes us wonder. But Lim has not responded to our request for comment.

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