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UID:0-344@aerospace.technion.ac.il

DTSTART;TZID=Asia/Jerusalem:20190710T163000

DTEND;TZID=Asia/Jerusalem:20190710T173000

DTSTAMP:20230527T134947Z

URL:https://aerospace.technion.ac.il/events/influence-of-pre-stressing-on-
 ballistic-shielding-efficiency/

SUMMARY:Influence of Pre-Stressing on Ballistic Shielding Efficiency
DESCRIPTION:Lecturer:Dana Mendelson\n Faculty:Department of Aerospace Engin
 eering\n Institute:Technion – Israel Institute of Technology\n Location:
 Classroom 165\, ground floor\, Library\, Aerospace Eng.\n Zoom: \n Abstrac
 t: \n Details: \n The long-standing competition between advancing projecti
 les penetration power\, on one hand\, and increasing the efficiency of pro
 tective structures\, on the other hand\, has resulted in a very large body
  of scientific research along with engineering design methodologies. In th
 e latter context\, pre-stressing the target material is a commonly accepte
 d technology aiming at strengthening the resistance to projectile penetrat
 ion.\nThe present research aims at deriving a new and simple analytical mo
 del for assessing the effect of pre-stressing in improving the ballistic w
 orthiness of targets made of pressure sensitive solids like concrete or si
 ntered powder metals. Analysis is within framework of finite strain contin
 uum mechanics of elastoplastic solids\, and centers on the cavity expansio
 n field model.\nWe begin with a brief review of available studies (mainly 
 experimental) on ballistic response of pre-stressed targets. Next\, we add
 ress the basic pattern of spherical cavity expansion under internal pressu
 re (simulating the projectile)\, in presence of remote confining pressure 
 that induces the pre-stresses. New elegant solutions for the cavitation pr
 essure are derived\, reflecting the coupled effect of pre-stresses and pre
 ssure sensitivity. It is shown that compressive pre-stresses are indeed be
 neficial in increasing the ballistic velocity (in plate perforation) and d
 ecreasing the penetration depth (in deep penetration).\nThe underlying vie
 w in this approach (originally due to work by H. Bethe during WWII) is tha
 t the cavity expansion solution provides the specific cavitation energy ne
 eded to create a unit of new volume along the projectile path. Our solutio
 n has been facilitated by further simplifying assumptions of material inco
 mpressibility and perfectly plastic response. The alternative cylindrical 
 cavitation field is analyzed as well\, and results are compared with those
  obtained from the spherical case.\nAnalytical findings are supported by a
 symptotic approximations and reduction to known solutions. We shall examin
 e sensitivities of the cavitation pressure to material parameters and leve
 l of confining pressure. Applications to ballistic perforation and penetra
 tion processes (assuming rigid projectiles and normal impact)\, and to des
 ign of protective structures\, will be discussed in view of model limitati
 ons and experimental results.
CATEGORIES:Seminars
LOCATION:Classroom 165\, ground floor\, Library\, Aerospace Eng.

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DTSTART:20190329T030000

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