Dimitrios Kakogiannis

Parametric Study of an Explosive‐Driven Shock Tube as Blast Loading Tool

The need for efficient blast loading tools is increasing with the development of new protective techniques. Among these tools, one can cite the use of an explosive-driven shock tube (EDST). The purpose of the present study is to define analytical equations to predict incident and reflected pressure and impulse generated at a laboratory scale EDST end in terms of the tube length, the tube diameter, the explosive mass, and the stand-off distance. The formulae are obtained based on a dimensional analysis and a numerical parametric study. The analytical study is supported by a set of experiments, in order to validate the obtained analytical models. The EDSTs discussed in this study are open on both sides with diameters ranging from 0.15 to 0.50m and a length ranging from 0.75 to 3m. Two different tube sections, circular, and square, are examined. Explosive charges from 5 to 50 g of C4 are used. Within these conditions reflected pressures ranging from 0.15 to 11 MPa and reflected impulses ranging from 100 to 3000 Pa·s are obtained at the tube end. The obtained analytical equations are compared to several available results and formulae from the literature. In addition to that, a graphic representation is developed in order to estimate the tube geometry and the explosive mass necessary to generate a given couple of pressure–impulse at the tube end.

Modelling the plastic deformation of Ti6Al4V under dynamic loading

In this paper, a multiscale numerical method is presented with the aim to model the response of a Ti6Al4V sheet under explosive forming. The numerical modelling focuses on the accurate definition of the plastic deformation of the Ti6Al4V specimens based on the texture of the material. The viscoplastic self-consistent polycrystal model code (VPSC) is used as a link between macroscopic response and the underlying microstructure taking into account the viscoplastic deformation of the specimen. Comparison is made with experimental results. The Cazacu–Barlat (CB06) material model is used because of its capability to describe the yielding asymmetry between tension and compression and to take into account the anisotropic behaviour of the sheet. The study focuses on the evaluation of the material model parameters and on how these affect the structural response of the Ti6Al4V specimens under explosive loading. This paper is part of a Themed Issue on Euromech 570: Interface-dominated materials.

Impact Study of Textile Reinforced Cementitious Materials: Test Method and Preliminary Results

In building engineering, impact loading and other accidental loads are mostly taken into consideration by measures on the structural level rather than on the material level, the latter one is even seldom explored. Textile reinforced Cements (TRCs) is a composite material group which is still in full development. Its potential to dissipate a significant amount of energy under low velocity impact loading was already indicated in a preliminary study. In the present study, the low velocity impact behaviour of TRC laminates is investigated more closely and this by means of an instrumented drop weight test. This study has shown the ability of the used test method to identify damage mechanisms underlying the energy absorption under low velocity impact loading in TRC composite laminates.