Abstract
Small punch tests were conducted for carbon steel specimens prepared with and without cold working. A digital image correlation technique was applied to measure displacement. Finite element analyses using the true stress-strain curves including post-necking strain could reproduce the load-displacement (LD) curve. Use of the nominal stress-strain curve obtained by the conventional tensile test was not enough to simulate the maximum load. It was found that the maximum load did not depend on the ultimate strength. Therefore, the ultimate strength prediction using the maximum load in the LD curve may not be valid for the general case. On the other hand, the yield strength correlated well with the deflection point in the LD curve. A new equation was proposed to estimate the yield strength that takes into consideration the influence of the specimen thickness.
Highlights
The small punch (SP) test has been applied to estimate tensile properties such as the yield and ultimate strengths [1,2,3]
The SP tests were conducted for carbon steel specimens with and without cold working
Use of the nominal stress-strain curve obtained by the conventional tensile test was not enough to simulate the maximum load Pmax
Summary
The small punch (SP) test has been applied to estimate tensile properties such as the yield and ultimate strengths [1,2,3]. Since a tiny specimen is used for the SP test, it is possible to determine the tensile properties for a small piece taken from an actual component. The tensile properties are determined from the load-displacement (LD) curve, which consists of four regions [2]: the elastic bending, plastic bending, membrane stretching and failure regions. The LD curve exhibits linear (elastic) deformation at the beginning of the SP test, and deflects due to yielding. The deformation of the specimen has been correlated to the stress-strain curve. The yield strength has been correlated to the initial deflection of the LD curve and the ultimate strength has been determined using the maximum load during the SP test [1,2]
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