Material Strength at High Pressure LDRD Strategic Initiative Final Report

Lassila, D H ; Bonner, B P ; Bulatov, V V ; Cazamias, J U ; Chandler, E A ; Farber, D L ; Moriarty, J A ; Zaug, J M

Lawrence Livermore National Laboratory

关键词: Flow Stress;    Plastics;    Strain Rate;    National Security;    Plasticity;   

DOI  :  10.2172/15009805
RP-ID  :  UCRL-TR-202805
RP-ID  :  W-7405-ENG-48
RP-ID  :  15009805

美国|英语

来源: UNT Digital Library

【 摘 要 】

Various aspects of the Laboratory's national security mission are now highly dependent on accurate computer code simulations of plastic flow (i.e., non-reversible deformation) of materials under conditions of high hydrostatic pressure. Strength models are typically dependent on pressure, temperature, and strain rate. Current strength models can not be extrapolated to high pressure because they are not based on the underlying mechanisms of plastic deformation. The critical need for predictive models of material strength, which describe flow stress in computer code simulations, has motivated LLNL's multiscale modeling efforts. Over the past three years, the ''Material Strength at High Pressure'' LDRD Strategic Initiative has established a framework for the development of predictive strength models for deformation of metals under conditions of high hydrostatic pressure. Deformation experiments have been developed to measure the effect of high pressure on the yield strength and work hardening behavior of high purity Mo and Ta single crystals. The over arching goal of the SI is to experimentally validate multiscale-modeling capabilities for deformation of metals under conditions of high pressure. The work performed and accomplished is a necessary next step in the development of predictive strength models. Our initial experimental results show that the influence of pressure is to dramatically increase the work hardening rate of Ta. Bridgman also observed this in experiments performed in the 1950's. Currently there is very little modern data on this phenomena, or theoretical understanding. The work started by this SI is a first step in a comprehensive understanding of plasticity under conditions of high pressure and we expect eventually to be able to incorporate the proper physics into dislocation dynamics (DD) simulations to capture the increase in work hardening that we observe experimentally. In the following sections we briefly describe the work that was performed in the areas of theory and DD simulation development (Section 2) and experimental work (Section 3). Journal articles and technical reports, which are essentially drafts of papers that will be submitted, are attached to this final report.