Finite element simulation of plates under non-uniform blast loads using a point-load method: Blast wave clearing

There are two primary challenges associated with assessing the adequacy of a protective structure to resist explosive events: firstly the spatial variation of load acting on a target must be predicted to a sufficient level of accuracy; secondly, the response of the target to this load must also be quantified. If a target is embedded within a finite reflecting surface then the process of blast wave clearing will occur. Diffraction of the blast around the target edge causes a low pressure relief wave to propagate inwards towards the centre of the target, reducing the late-time development of pressure and resulting in high spatial non-uniformity of the blast load. This paper presents experimental measurements of the dynamic displacement-time histories of steel plates subjected to blast loads where the plate was situated within a finite reflecting surface to allow for clearing effects to take place. Associated finite element modelling is presented, where coupled blast-target interaction is modelled explicitly using the Arbitrary Lagrangian-Eulerian solver in LS-DYNA. An alternative method is presented, where the loading is applied as discrete load predictions at individual nodes. The results show that vast computational savings can be made when modelling the load in this manner, as well as better agreement with the experimental measurements owing to a more accurate representation of the applied load.