Blasting simulation using LS-DYNA for safer industrial equipments

Federico Valente, Stefano Scardino



The simulation of blast waves is maintaining and maybe increasing its role in fluid dynamics, due to the many important applications primarily in the defense and the oil&gas sectors. In the past, due to the complexity of the phenomenon to be modelled, this type of analysis was exclusively approached by offices equipped with very powerful facilities. Recently,the application of theALEmethodfor blast simulationshas been associated withother methods in order toreducethe computational time, without affectingthe accuracyof the results.There is alreadyliterature on this subjectthat describesapplications with such methods as the "LoadBlastEnhanced" (LBE) approach, the Multi-Material Arbitrary Lagrange Eulerian (MM-ALE) solver and the LBE-MMALE coupling.
LBE is a purely Lagrangian approach,wheretheair blast pressure is computed empirically and directly applied to Lagrangian elements of thestructure. The purpose is to define an air blast function for the application of pressure loads due the detonation of aconventional explosive.In the context of blast simulation, the general Multi-Material Arbitrary Lagrangian-Eulerian (MMALE) formulation involves explicit modeling of the explosive, the blast transmission media and the structure subjected to the blast within the MMALE solver. The structure is generally treated as Lagrangian and fluid-structure interaction (FSI) is used for coupling with the MMALE domain. This computational approach is able to predict accurately the relevant aspects of the blast-structure interaction problem, including the blast wave propagation in the medium for pressurized loading cases and the response of the structure to blast loading.

In the presented example,the combination of theLBEapproach and MM-ALE solveris used to build afinite element analysisofthe impact of ablast waveagainstan assembly. The goal istoevaluatepermanentdeformations of the assembly and each parts, which could affect their functionality(e.g. loss of contact between coupledparts). The blast wave generated by an explosion is a plane wave front whose pressure value is set to 20 kPaabove ambient pressure (0.198 barg). The generatedblast wave is the result ofa calculationof adequately chosen and setparametersof the explosive.LS-Dyna is the software used to model thephenomenon. The approach can be appliedfruitfully to assess the accomplishment of the designof a structure, which will beclosed to dangerous environments to minimum blast protection requirements, defined experimentally or by international safety specifications.