Normal and oblique impact of small arms bullets on AA6082-T4aluminium protective platesTore Børvik a ,b ,*,Lars Olovsson c ,Sumita Dey a ,b ,Magnus Langseth aaStructural Impact Laboratory (SIMLab),Centre for Research-based Innovation (CRI)and Department of Structural Engineering,Norwegian University of Science and Technology,Rich.Birkelands vei 1A,NO-7491Trondheim,Norway bNorwegian Defence Estates Agency,Research and Development Section,PB 405Sentrum,NO-0103Oslo,Norway cImpetus Afea AB,SE-14160Huddinge,Swedena r t i c l e i n f oArticle history:Received 19June 2010Received in revised form 26January 2011Accepted 1February 2011Available online 12March 2011Keywords:Normal and oblique impact Small arms bullets Aluminium armour3D numerical simulationsa b s t r a c tNormal and oblique impact on 20mm thick AA6082-T4aluminium plates are studied both experi-mentally and numerically.Two types of small arms bullets were used in the ballistic tests,namely the 7.62Â63mm NATO Ball (with a soft lead core)and the 7.62Â63mm APM2(with a hard steel core),fired from a long smooth-bore Mauser ri fle.The targets were struck at 0 ,15 ,30 ,45 and 60 obliquity,and the impact velocity was about 830m/s in all tests.During testing,the initial and residual bullet velocities were measured by various laser-based optical devices,and high-speed video cameras were used to photograph the penetration process.Of special interest is the critical oblique angle at which the pene-tration process changes from perforation to embedment or ricochet.The results show that the critical oblique angle was less than 60 for both bullet types.A material test programme was also conducted for the AA6082-T4plate to calibrate a modi fied Johnson e Cook constitutive relation and the Cockcroft e Latham failure criterion,while material data for the bullets mainly were taken from the literature.3D non-linear FE simulations with detailed models of the bullets were finally run.Good agreement between the FE simulations and the experimental results for the APM2bullets was in general obtained,while it was more dif ficult to get reliable FE results for the soft core Ball bullets.Ó2011Elsevier Ltd.All rights reserved.1.IntroductionThe need for protection against small arms and light weapons is large both from a civilian and a military point of view [1,2].Even so,few investigations exist in the open literature where the hazard from such weapons has been systematically studied.The majority of ballistic studies are further concerned with the worst-case scenario,i.e.the normal impact condition where the angle between the velocity vector of the projectile and the normal vector of the target is zero.However,in most real cases the projectile will strike the target with some degree of obliquity.Earlier works on oblique impact have been collected in the review papers by Backman and Goldsmith [3],Johnson et al.[4],Corbett et al.[5]and Goldsmith [6].Of these earlier works,the paper by Awerbuch and Bodner [7]is of particular interest.They showed experimentally that the velocity drop during perforation of aluminium plates by 0.22calibre softcore lead bullets was almost unaffected by the oblique angle to around 30 .At higher oblique angles,the velocity dropped considerably.Similar results were obtained by Gupta and Madhu [8]for hard core steel bullets.More recent studies of oblique impacts on various materials can be found in Piekutowski et al.[9],Zhou and Stronge [10],Iqbal et al.[11,12],Teng et al.[13],Lopez-Puente et al.[14]and Shokrieh and Javadpour [15].In this paper,normal and oblique impact on 20mm thick AA6082-T4aluminium plates are studied both experimentally and numerically.Two different types of small arms bullets were used in the ballistic tests,namely the 7.62Â63mm NATO Ball (with a soft lead core)and the 7.62Â63mm APM2(with a hard steel core).The bullets were fired from a long smooth-bore Mauser ri fle at a constant velocity of about 830m/s in all tests.The targets were struck at 0 ,15 ,30 ,45 and 60 obliquity,and the critical oblique angle was determined.Initial and residual bullet velocities were accurately measured during testing by various laser-based optical devices,and two synchronized Photron Fastcam-Ultima APX high-speed video cameras were used to photograph the penetration process.A material test programme for the AA6082-T4aluminium plate was conducted to identify the material parameters for the modi fied Johnson e Cook constitutive relation and the*Corresponding author.Structural Impact Laboratory (SIMLab),Centre for Research-based Innovation (CRI)and Department of Structural Engineering,Norwegian University of Science and Technology,Rich.Birkelands vei 1A,NO-7491Trondheim,Norway.Tel.:þ4773594647;fax:þ4773594701.E-mail address:tore.borvik@ntnu.no (T.Børvik).Contents lists available at ScienceDirectInternational Journal of Impact Engineeringjournal homep age:www.elsevier.com/locate/ijimpeng0734-743X/$e see front matter Ó2011Elsevier Ltd.All rights reserved.doi:10.1016/j.ijimpeng.2011.02.001International Journal of Impact Engineering 38(2011)577e 589