Resistivity based evaluation of the fatigue behaviour of cast irons

摘要

Cast irons are used in particular for highly stressed components in the automotive and commercial vehicle industry, e.g. for crankcases and in the wind power industry, e.g. for rotor hubs. The microstructure of cast irons and consequently their mechanical properties are strongly influenced by parameters like graphite shape, micro-shrinkage cavities, micro-pinholes and micro-cracks. The measurement of the electrical resistance in the unloaded state and its change during fatigue loading offers the possibility to get detailed information about the actual defect density and the cyclic deformation behaviour. In the scope of the present research work stress-controlled load increase tests and constant amplitude tests were carried out at ambient temperature with specimens of the perlitic cast irons EN-GJL-250 (ASTM A48 35B), EN-GJV-400 and EN-GJS-600 (ASTM 80-55-06). Beside electrical measurements scanning electron microscopy (SEM) was used to characterize the microstructure and to correlate the change of microstructural details with cyclic properties.