טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentCohen Tal
SubjectCavitation and Shocks in Porous Plasticity
DepartmentDepartment of Aerospace Engineering
Supervisor Professor Emeritus David Durban
Full Thesis textFull thesis text - English Version


Abstract

Recent conflicts have demonstrated that focusing more knowledge and research towards advanced protection technologies, to deal with the increasing threat to population safety, can have beneficial outcomes beyond expectation. An important ingredient in achieving this goal is by modern protective civilian spaces (shelters) which can withstand direct hypervelocity impact, including individual lightweight shields (personal armor). Modern aircrafts are also expected to provide protection against bullets or shrapnel hitting the thin pressurized structure, endangering the integrity of the entire airplane. Likewise, satellites are under constant threat of impact by space debris at extremely high velocities, with even more severe danger imposed by meteorides. These threats are the main motivation for the present research; learning how civilian and airborne structures respond to impact and penetration would facilitate design of more efficient protective systems which can in turn save lives. 


The effect of material porosity on penetration processes via quasistatic and dynamic cavitation models, is examined, attempting at simple analytical results. Hypervelocity loading, which includes propagation of plastic shock waves, is studied and the possibility of a stiffening effect due to high energy absorption, similar to the wave drag effect in fluid dynamics is considered. In that context, finite strain longitudinal plastic shock behaviour is analyzed and compared with shock behaviour in dynamic cavitation.