Effect of the pearlite content of ferritic cast iron material on the crack resistance behaviour under dynamic load

摘要

The factor of safety against rupture of castings subject to high-strength loads,such as transport and pressure vessels as well as windmill components,is assessed taking into account fracture mechanical characteristic values for the static,cyclic and dynamic load condition.The experimental investigation of dynamic crack initiation values with regard to cast iron-specific aspects was the subject of a contribution at the 12th ICF in Ottawa.Continuing the examination,the contribution on hand describes the effect of the microstructure on the mechanical and fracture-mechanic properties of ferritic and ferrite-pearlite cast iron materials at low temperatures.The strength and sensibility to brittle fracture are conventionally evaluated by applying the characteristic values of the tensile test or the notched bar impact test.During the recording of the notched bar impact work-temperature curves in the temperature range of 180 °C to -60 °C,the transition temperature curves are defined by comparing various criteria.The dynamic crack initiation values at -40 °C are determined via the recording of cracking resistance curves (J integral concept).In addition,via the determination of the crack arrest toughness KIa at 50 mm thick CCA samples,the crack arrest behaviour is controlled in the temperature range of -40 °C to -80 °C.