Fatigue Assessment of Notches and Cracks in Ductile Cast Iron

The steadily increasing use of ductile cast iron and the necessity for building larger cast components present new challenges to the designers. In despite of large cast components are designed adhered to standards, unexpected failure sometime occurs. One reason is the inevitable manufacturing defects containing within the cast components that behave like cracks under cyclic loading. In addition the probability of a large defect to be situated at a critical region of the component increases with the size. Another reason is the effect of geometric discontinuities such as holes, threads and fillets, which are part unavoidable of the designs. These discontinuities that are usually called notches disturb the stress field and cause high local stress concentration. Thus dealing with these severe stress risers (defects and notches) is not an easy task. Therefore most designers resort to use very high and unnecessary safety factors