https://doi.org/10.1051/epjconf/201818302001
Temperature dependent crack initiation of 42CrMo4 steel at high loading rates
Institute of Materials Engineering, TU Bergakademie Freiberg,
Gustav-Zeuner-Str. 5,
09599
Freiberg,
Germany
* e-mail: sebastian.henschel@iwt.tu-freiberg.de
Published online: 7 September 2018
Dynamic crack initiation with crack tip loading rates K˙ of approximately 2 ‧ 106 MPa√ms− in high-strength 42CrMo4 steel was investigated. To this end, a recently developed split Hopkinson pressure bar with four-point bending was utilized. V-notched and precracked Charpy specimens were tested. The tests were performed at temperatures of –40 °C and 20 °C. The loading of the specimen was determined by analyzing the strain in the incident and transmission bars. Furthermore, strain gauges at the specimen’s surface were applied to measure the crack tip loading. High-speed photography complemented the analysis of the specimens loading and the detection of the crack initiation. Fracture surface analysis by means of scanning electron microscopy enabled the measurement of the fracture surface topography and, consequently, stretch zone height and width. Hence, the macroscopically measured dynamic crack initiation toughness was correlated with the toughness at microscopic scale. It was observed that the resistance against dynamic crack initiation decreased with decreasing temperature. Microscopically, a decrease in toughness was analogously observed. Non-metallic inclusions resulted in crack path deflection with localized shear zones. After a small stable crack extension, cleavage fracture was observed.
© The Authors, published by EDP Sciences, 2018
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
