The effects of blast induced imperfections on the energy absorption characteristics of square tubes

Abstract

The geomemc deformalion induced by (
[0 equal blast loads on uppositt sides of a

thin-walled square tube ",ill weaken the siruclure. This will improve i[s energy

absorbrioll charanenstics compared to a gcomccrically "perfect" square tube of the

same size by reducing me crush load when cOlnpressed i11 the axial direction.

Different types of impcrfcnioll can be induced depending on the Sl?e of the blast

loads.

Consequent to the blast loads, high temperalures ""ill also be induced by adiabalic

heating due to large plaslic deformalion and high scrain rate, h is expected tbt the

matenal properties of the tube ",ill be affected in the reglOn of the imperfections. It

IS anticipated that the temperature ",-ill haw a greater effect than the strain rate lrl

mat the material properties of the tube in the region of the blast l,ill soften (increase

il1 tenperature causes yield scress to decrease while an increase in scra.Ln rate causcs

yield scrcss to increase).

This Investigation examines how blast-induced imperfeclions at opposite sides of a

square tube affect the thin-wall stnlCrure and reduce its erush load when compressed

ill tl:e axial direction i,e. its energy absorption characteristics. , senes of

experimcmal results and numerical simularions using the hydro-dynamic code;

AutoDYt, to characterisc the blast load, and fmite clement package;

ABAQlIS/E;..p!lcii .5 -6, to predict the respDrlse of the mild steel tubics, are

reported,

Blast imperfections are mduced m thc square tubcs on 0ppoSl[C sides ith thc use of

plastic explosive (PE4) , The e..'tplosive, in disc shape, is placed at mid length of mild

steel square tubcs, of twO cross-sections S()XSOxL5rrull and 7Sx75x1.6mm. The blast

loads provide the Impulse requlred to create geomctric changes and affcct thc

material propenies of the tubes,