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Local Measurement of Stress–Strain Behaviour of Ductile Materials at Elevated Temperatures in a Split‐Hopkinson Tension Bar System
Author(s) -
Vilamosa V.,
Clausen A. H.,
Fagerholt E.,
Hopperstad O. S.,
Børvik T.
Publication year - 2014
Publication title -
strain
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.477
H-Index - 47
eISSN - 1475-1305
pISSN - 0039-2103
DOI - 10.1111/str.12084
Subject(s) - necking , materials science , split hopkinson pressure bar , composite material , digital image correlation , strain rate , tension (geology) , stress (linguistics) , pyrometer , strain gauge , bar (unit) , strain (injury) , finite element method , fracture (geology) , dynamic tension , temperature measurement , structural engineering , compression (physics) , ultimate tensile strength , thermodynamics , medicine , linguistics , philosophy , physics , meteorology , engineering
ABSTRACT A split‐Hopkinson tension bar system is modified to allow for measuring the stress–strain behaviour of ductile materials at large strains, high strain rates and elevated temperatures. The specimen is heated by induction, and a pyrometer provides a laser‐based temperature measurement that controls the testing temperature in a feed‐back loop. A high‐speed digital camera system and an edge detection algorithm are used to obtain local measures of strain after necking of the axisymmetric specimens. Using the local strain measurements and Bridgman's analytical formulas, it is feasible to find the equivalent stress–strain curve to fracture for different levels of strain rate and temperature. Thermal and thermo‐mechanical finite element simulations of the test set‐up are used to evaluate the validity of the proposed experimental method.