Effects of section Size on static tensile Properties of mild steel Bars

Abstract

Tensile strength of notched -plates or -bars decreases considerably as the absolute size of a specimen increases and an increase in tested size is known to be a potent embrittling factor. To find the reason why larger steel bars become brittle, tensile tests of round bars of various diameters (0.7∼50mm) were made. The percentage contraction of area showed marked size dependence. This is due to the fact that plastic deformation does not take place similarly in the specimen in accordance with its size. The stress distribution in the specimens under pull were studied by measuring residual stress in their unloaded state. In specimens, pulled to stress above the yield point, the stress distribution is severely uneven. The uneveness, however, decreases as the load increases and at the maximum load, which the specimen can hold up during the test, stress distribution becomes even. The stress at the necked portion of the specimen was discussed.