Correlation of tensile test parameters and bendability of high-strength steels

The aim of the study was to investigate correlation between bendability and tensile properties of high-strength steels. Strength and elongation in tensile test have traditionally been basic values in evaluating bending properties. Advanced high-strength (AHS) steels often have tendency for strain localization, causing risk of fractures and impairing the shape of the bend. Practice has shown that tensile test results, indicating bendability well, are not sufficiently accurate when using AHS steels. Since tensile test is a fast, simple and cheap testing method, it would be beneficial to rework it to suit better for predicting of bendability. In this study, the usability of tensile test results to predict failures in bending AHS steels has been investigated. The most common failures and failure mechanisms in bending are also presented. Test materials used were 6 mm thick AHS wear-resistant, protection and structural steels with good and poor bending properties. Minimum bending radii were determined and then compared with tensile test results to estimate the correlation. Conventional tensile test results, fracture surfaces and necking through width and thickness were analyzed. Correlation coefficient for measured tension properties and minimum bending radius was calculated. Results showed that in tensile test, have the best correlation with minimum bending radius with necking through the thickness and actual strain in necking area.