Critical conditions for failure in materials subjected to high rates of loading. Final report, 15 August 1981-30 November 1984

Technical Report · Wed Mar 20 00:00:00 EST 1985

OSTI ID:5526774

Clifton, R J; Asaro, R J; Duffy, J; Freund, L B; Needleman, A

Mechanisms of the plastic deformation and failure of steels under dynamic loading conditions were examined through investigations in three area: dynamic plasticity, shear bands, and fracture initiation. The dynamic plastic response of 4340 VAR steel were measured in torsion experiments at strain rates from 10/sup -4/ sec/sup -1/ and in pressure-shear experiments at strain rates of 10/sup -5/ sec/sup -1/. 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 were 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.

• Research Organization: Brown Univ., Providence, RI (USA). Dept. of Engineering
• OSTI ID: 5526774
• Report Number(s): AD-A-153135/9/XAB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
42 ENGINEERING
STEELS
DEFORMATION
DYNAMIC LOADS
DUCTILITY
FRACTURES
LOW TEMPERATURE
MICROSTRUCTURE
SENSITIVITY
SHEAR PROPERTIES
STATIC LOADS
STRAIN HARDENING
STRAIN RATE
THERMAL CONDUCTIVITY
TORSION
ALLOYS
CRYSTAL STRUCTURE
FAILURES
HARDENING
IRON ALLOYS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
PHYSICAL PROPERTIES
TENSILE PROPERTIES
THERMODYNAMIC PROPERTIES
360103* - Metals & Alloys- Mechanical Properties
420500 - Engineering- Materials Testing