Shear Localization and Fracture in Shocked Metals

Becker, R ; Belak, J ; Campbell, G

Lawrence Livermore National Laboratory

关键词: Acceleration;    Fractures;    Chemical Explosives;    36 Materials Science;    Dislocations;   

DOI  :  10.2172/15004900
RP-ID  :  UCRL-ID-145389
RP-ID  :  W-7405-ENG-48
RP-ID  :  15004900

美国|英语

来源: UNT Digital Library

【 摘 要 】

Metals are used in structural engineering applications because they can yield and deform before they break. However, under certain conditions of dynamic loading, metals can fail prematurely. This behavior is often associated with shear localization phenomena, with a shear band acting as a precursor to crack formation. These phenomena have been observed in metals for some time, however modeling this behavior in a continuum simulation code has met with very limited success. We are pursuing a series of model experiments closely linked to new model development in order to gain a fundamental understanding of shear localization and fracture. Many NNSA and DoD related missions require modeling and simulation of the response of metals to high explosive (HE) loading and whether those metals fail or fracture. HE loading differs from the loading experienced by a specimen in a traditional engineering application. In HE loading, the first process to occur is the passage of a strong shock through the metal due to detonation. This shock completely changes the microstructure of the metal by inducing intense dislocation multiplication, sometimes accompanied by the formation of deformation twins. This change in microstructure strongly modifies the mechanical response of the metal, changing its yield strength, work hardening rate, and strain to failure. Only after this complete change of microstructure does the metal start to deform due to the velocity imparted by the shock and the further acceleration from the high pressure HE detonation gasses.