Critical Conditions for Failure in Materials Subjected to High Rates of Loading.
Abstract
Mechanisms of the plastic deformation and failure of steels under dynamic loading conditions have been examined through investigations in three area: dynamic plasticity, shear bands, and fracture initiation. The dynamic plastic response of 4340 VAR steel has been measured in torsion experiments at strain rates from 10 to the minus 4th power minus 1 sec and in pressure-shear experiments at strain rates of 10 to the 5th power minus 1 sec. Torsion experiments were conducted at temperatures from -190C to 23C on three tempers (HRC 55,44,33). Relatively weak strain-rate sensitvity obtained in these experiments has been related to the high athermal stress barrier that must be overcome for plastic deformation at low temperatures. Temperature profiles in the vicinity of the shear bands were measured using a ten-element, infrared detector system. Numerical simulations were used to assess the roles of strain hardening, strain-rate sensitivity, thermal softening and heat conduction on shear band formation. Finite element methods were developed for rate dependent plasticity and applied to calculations of failure through shear band propagation and ductile fracture. The effects of microstructure on dynamic and quasi-static fracture initiation of AISI 1020 steel were investigated by means of our notched-round bar experiment. The results cover the temperature range -150C to 100C. For static loading under ductile conditions the results are now being supplemented by a detailed study to determine tthe instant of fracture initiation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 20, 1985
- Accession Number
- ADA153135
Entities
People
- A. Needleman
- J. Duffy
- Lambert Ben Freund
- R. J. Asaro
- R. J. Clifton
Organizations
- Brown University