Mechanical properties of Metals and Alloys (Ⅱ)

1.The tesile test (cont’ d) Because of necking, the capacity of the ma-terial for plastic deformation in tension, i. e.the ductility, is not truly indicated by thestrain to fracture measured along the gaugelength. A longer gauge length would give asmaller value. A better measure of ductility isthe reduction of area at the narrowest part of theneck. This can be expressed as a logarithmicstrain in the form ln (A/A) where AandAare the initial and final areas. In an ideallyductile material a total reduction of area occurs,