The standoff distance between the explosive and the structure and the depth of the explosion are the most dominant factors in UNDEX loading.
Hence, for precise design and analysis of structures subjected to UNDEX, experimental studies on reduced scale models are invaluable.
Lagrangian-Eulerian procedures are common to get feasible results from FSI UNDEX problems.
where [p.sub.i] is the incident fluid pressure (here UNDEX overpressure and pulsations), [p.sub.s] is the scattered pressure of the structure, G is a matrix that couples structural degrees of freedom to the fluid grid, and [A.sub.f] is the matrix that stores information of areas of Lagrangian elements in fluid cells.
In most UNDEX loadings, strain rate can reach up to [10.sup.4]/s; hence, to get accurate results, an acceptable rate sensitive strength model must be used.
Jen  used finite element software ABAQUS to simulate and analyze the transient dynamic response of a midget submersible vehicle (MSV) pressure hull that experiences loading by an acoustic pressure shock wave resulting from an underwater explosion (UNDEX).
Figure 1 shows the different events occurring during the UNDEX event in a pressure against time history plot .
In explicit dynamic analysis, the shortest wavelength can be estimated using the highest frequency in the UNDEX load or prescribed boundary conditions .
The location of the charge and the stand-off point defined as reference points, prior to the interaction, and the effect of the UNDEX event are transferred to the structure by means of the incident wave loading feature .
The plate is loaded due to the UNDEX with charge mass 7 kg TNT at standoff distance of 5 m from the central point of the plate.
The UNDEX analyst identifies the location of the charge, the location of a reference point (typically the point on the submarine closest to the charge), and the pressure pulse history at the reference point.
Since there are many advantages to using simulation rather than expensive destructive testing, application of UNDEX technology will continue to develop in both military and civil arenas."