Localized Damage Process in Metal Structures Under High Velocity Deformation
Abstract
The ASB initiation and growth in high strength steel are investigated. An integrated energy theoretical approach is suggested for modeling ASB development and identifying post critical structure state in the bands. Criteria are formulated for both micro cracks and macro cracks initiation along the band length. On that basis a numerical simulation model is developed for axially symmetric body. The process of ASB initiation and growth is descritized in time and in space co-ordinate steps. For defining process parameters a variant of the finite difference method, called Method of finite systems, is applied. In this method for every discrete moment of time and for every point of the body space mesh an iterative procedure is realized in which the calculations are made in blocks of the basic groups of equations for the process. The post critical state is calculated with an a priori assuming the type of distribution of the plastic strain and temperature across the ASB thickness. Thus considerable difficulties are overcome in the defining the mechanical-mathematical models for the different ASB structures. The ASB initiation and growth are studied experimentally on high strength martensite steel. The strength properties of the initial material in dynamic conditions are identified by using the Hopkinson bar. An approximation of the yield condition is proposed taking into account the plastic and dynamic hardening and the thermal softening. A series of experiments by Hopkinson bar of various sizes of impulse loading are carried out to investigate the process of plastic and temperature localization. The development of localization bands is studied by optical, scanning and transmission electron microscopy. The micro structural changes caused by localized plastic strain are traced and the required temperature increase for their occurrence accounted for. Zones along the band length are identified where the changed structure types appear.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1999
- Accession Number
- ADA378810
Entities
People
- Angei Baitov
- Ganka Ziateva
- Ivailo Katzarov
- Stefan Vodenicharov
- Zanka Karnenova
Organizations
- Bulgarian Academy of Sciences