Abstract
Recently, the authors in this paper proposed a correction function to determine material's equivalent stress-strain curve with axisymmetric-notched tensile specimens. In this study, tensile tests were performed at room temperature, −30 °C and − 60 °C with axisymmetric notched tensile specimens to verify this method and to identify the equivalent stress-strain curves of a 420 MPa structural steel. A high-speed camera was used together with the so-called edge-tracing method to calculate average true strain. The material's equivalent stress-strain curve was also measured with extensometer and smooth round bar specimens. Experimental results show that equivalent stress-strain curve of this structural steel is sensitive to test temperature. Equivalent stress-stress curves obtained from axisymmetric notched tensile specimens by using the proposed correction function show good agreement with those from extensometer before diffuse necking and from Bridgman correction at large strain using smooth tensile specimens. Since fracture strain strongly depends on the notch geometry, it is recommended to use axisymmetric notched tensile specimens with smaller a0/R0 when applying the proposed correction function to measure material's equivalent stress-strain curve.
Highlights
Identifying material’s equivalent stress-strain curve in large strain is very important for large deformation analysis, such as plastic forming [1, 2], ductile fracture analysis with finite element method [3,4,5,6,7,8]
9 Recently, we proposed a correction function to determine material’s equivalent stress-strain curve with 10 axisymmetric-notched tensile specimens
With Zhang’s method, true stress-strain curves from flat tensile specimens can be obtained at large strain
Summary
Identifying material’s equivalent stress-strain curve in large strain is very important for large deformation analysis, such as plastic forming [1, 2], ductile fracture analysis with finite element method [3,4,5,6,7,8]. 76 To measure the true stress-strain curve of each individual material zone in a weldment, Zhang [26] proposed a correction function, with which the true stress-strain curve from an axisymmetric notched tensile specimen can be converted to the corresponding one from a smooth round bar specimen. This method is not accurate at large strain, but lay a foundation for our recent work [27, 28].
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