Jacek Selejdak

Fatigue Strength of Ductile Iron in Ultra-High Cycle Regime

Machine and equipment safety is the most essential factor that determines the choice of a particular material used in the construction phase. Failure analyses in engineering praxis demonstrate that nearly 90 % of all cases of failures are caused by fatigue. For popular technical applications such as cars and trains, the durability expected for some components ranges from 108 to 1010 loading cycles. However, only few studies have been carried out for more than 107 cycles. The SN curve in the ultra-wide life region must be determined in order to ensure actual fatigue strength and safety of these components. This paper presents the results obtained from fatigue tests carried out by means of a high-frequency fatigue testing machine for the three grades of ductile iron: with ferritic-pearlitic matrix (GGG50), with pearlitic-ferritic matrix (GGG60) and ADI cast iron in the range from 106 up to 1010 cycles.

Analysis of Structure of Elements for Automotive Industry

The paper presents the results of the structure and chemical composition of materials used to manufacture of gear wheel for the automotive industry. Analyzed gear wheel that is a part of one of the mechanical systems of an automotive vehicle was made of sinter Sint-D 32 in the technology of powder metallurgy and alloy structural steel for quenching and tempering 42CrMo4. The cause of the analysis was to research for an alternative material for sinter Sint-D 32 after identified low static strength according to the requirements applicable in the automotive industry. For the analysis were used standard test methods applicable in materials science. Based on microstructure and mechanical properties analysis performed according to requirements applicable in the automotive industry, the research found that steel 42CrMo4 is relevant material to be used in serial production for this particular gear wheel.