Browsing by Subject "Nodular iron"

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    Fracture behavior of overmatched ductile iron weldment
    (Carl Hanser Verlag, 2007) Cetinel H.
    The fracture behavior of welded ductile iron is discussed by means of experimental and theoretical studies. Ferritic nodular cast irons were joined by cold arc welding in order to obtain over-matched weldment in which the yield strength of the weld metal is higher than that of the base metal. As a result of the welding process, various regions with different mechanical properties formed in the welded specimens. In the experimental part of the study, the mechanical properties of the different regions in the welded specimens were identified and J-Integral toughness values were determined by fracture toughness tests for different crack locations including the base metal, the heat affected zone and the weld metal. In the numerical part of the study, finite element analyses were conducted by fixing 3-D models precracked at different locations for different crack lengths. In these models, after stress-strain analysis, stress triaxiality and plastic deformation characteristics around the crack tip were determined for each crack location and different crack sizes. It was found that stress triaxiality values increase with growing crack length. Different regions with different strength levels in the weldment affect the extension of plastic deformation in the models. Hindrance to the extension of plastic deformation at the heat affected zone and diffusion line causes an extra increase in stress triaxiality at the crack tip.
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    Fracture behavior of overmatched ductile iron weldment
    (Carl Hanser Verlag, 2007) Cetinel H.
    The fracture behavior of welded ductile iron is discussed by means of experimental and theoretical studies. Ferritic nodular cast irons were joined by cold arc welding in order to obtain over-matched weldment in which the yield strength of the weld metal is higher than that of the base metal. As a result of the welding process, various regions with different mechanical properties formed in the welded specimens. In the experimental part of the study, the mechanical properties of the different regions in the welded specimens were identified and J-Integral toughness values were determined by fracture toughness tests for different crack locations including the base metal, the heat affected zone and the weld metal. In the numerical part of the study, finite element analyses were conducted by fixing 3-D models precracked at different locations for different crack lengths. In these models, after stress-strain analysis, stress triaxiality and plastic deformation characteristics around the crack tip were determined for each crack location and different crack sizes. It was found that stress triaxiality values increase with growing crack length. Different regions with different strength levels in the weldment affect the extension of plastic deformation in the models. Hindrance to the extension of plastic deformation at the heat affected zone and diffusion line causes an extra increase in stress triaxiality at the crack tip.
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    The effect of undermatching on crack tip constraint in a welded structure of nodular irons
    (2008) Cetinel H.; Aksoy T.
    The main aim of this paper is to investigate the effect of yield strength mismatch of parent and weld metal on the fracture behavior of plain and heat-treated welded nodular cast iron. For this, experimental and theoretical studies were performed. Nickel electrode, which has lower yield strength value than that of the parent material, was used to join nodular cast iron by cold arc welding method. In experimental study, fracture toughness (J-integral) values were determined for various crack locations including base, weld metal and heat affected zone. In theoretical study, finite element analyses were performed for the same crack locations with different crack lengths. Stress triaxiality and equivalent plastic strain values were determined for all crack locations and various crack lengths. Finally, fracture toughness values of the base metal were determined as lower than those of the other regions including the weld metal and the heat affected zones. Stress triaxiality and equivalent plastic strain values used to clarify the effect of yield strength mismatch on the constraint around crack tip increased with growing crack length in annealed and under-matched models. In annealed models, stress triaxiality values became slightly lower but equivalent plastic strain values appeared higher than those of under-matched models. © 2007.