Modeling the Charpy Impact Energy of Functionally Graded Steels at Different Strain Rates

Charpy impact energy of functionally graded steels produced by electroslag remelting in crack divider configuration has been modeled in various strain rates. It has been well known that majority of materials indicate different behaviors under different strain rates and temperatures. Therefore, modifying the elastic-plastic model considering the effects of strain rates and temperature gives us an acceptable prediction of these composites behaviors in impact test. In this investigation, graded steel was divided in to several layers in which the layers have the same strains under the impact. Constitutive equation describing the flow stress variations as a function of strain rates and temperatures, have been used to express the stressstrain behavior of layers. The parameter values of constitutive equation determined for all the layers via using the boundary conditions based on composite graded behaviors which were the characterized ferrite, austenite, bainite and martensitte phases. Consequently by applying the rule of phase mixtures and ascribing the impact energy of each layer to the area of stress-strain curve of the same layer, the whole impact energy of composite is the sum of layers impact energy with considering the layers volume fraction.