An improved description of copper‐ and iron‐cylinder impact (Taylor) test results has been obtained through the use of dislocation‐mechanics‐based constitutive relations in the Lagrangian material dynamics computer program EPIC‐2. The effects of strain hardening, strain‐rate hardening, and thermal softening based on thermal activation analysis have been incorporated into a reasonably accurate constitutive relation for copper. The relation has a relatively simple expression and should be applicable to a wide range of fcc materials. The effect of grain size is included. A relation for iron is also presented. It also has a simple expression and is applicable to other bcc materials but is presently incomplete, since the important effect of deformation twinning in bcc materials is not included. A possible method of acounting for twinning is discussed and will be reported on more fully in future work. A main point made here is that each material structure type (fcc, bcc, hcp) will have its own constitutive beha...

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Dislocation-mechanics-based constitutive relations for material dynamics calculations

Ballistic penetration of steel plates

The high strain rate dependence of the flow stress of metals and alloys is described from a dislocation mechanics viewpoint over a range beginning from conventional tension/compression testing through split Hopkinson pressure bar (SHPB) measurements to Charpy pendulum and Taylor solid cylinder impact tests and shock loading or isentropic compression experiment (ICE) results. Single crystal and polycrystal measurements are referenced in relation to influences of the crystal lattice structures and nanopolycrystal material behaviours. For body centred cubic (bcc) metals, the strain rate sensitivity (SRS) is in the yield stress dependence as compared with the face centred cubic (fcc) case of being in the strain hardening property. An important consequence is that an opposite ductility influence occurs for the tensile maximum load point strain that decreases with strain rate for the bcc case and increases with strain rate for the fcc case. Different hexagonal close packed (hcp) metals are shown to foll...

/pdf/high-strain-rate-properties-of-metals-and-alloys-1vmx3spvaq.pdf

High strain rate properties of metals and alloys

This paper examines the usefulness of cylinder‐impact test data to determine constants for various computational constitutive models. The Johnson–Cook and Zerilli–Armstrong constitutive models are evaluated by comparing model predictions to tension, torsion, and cylinder‐impact test data. Then the cylinder‐impact test data are used to determine constitutive model constants for various forms of these models. Under bounded conditions of strains and strain rates, this approach can produce useful results. It can also produce very erroneous results if not used properly.

Evaluation of cylinder‐impact test data for constitutive model constants

A transmission electron microscopy study of the white-etching layer on a rail head

The mean dynamic yield strength of copper and low carbon steel at elevated temperatures from measurements of the “mushrooming” of flat-ended projectiles

Numerical Modeling of Hydraulic Fracture Propagation and Fault Activation in the Presence of a Sealing Fault and Highly Permeable Damage Zone - A Case Study of the Montney Formation in British Columbia

D Eaton

Papers

The mean dynamic yield strength of copper and low carbon steel at elevated temperatures from measurements of the “mushrooming” of flat-ended projectiles

Numerical Modeling of Hydraulic Fracture Propagation and Fault Activation in the Presence of a Sealing Fault and Highly Permeable Damage Zone - A Case Study of the Montney Formation in British Columbia