PSI - Issue 2_B

Andrzej Kubit et al. / Procedia Structural Integrity 2 (2016) 3330–3336 A. Kubit et al./ Structural Integrity Procedia 00 (2016) 000 – 000

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 for the SP specimens increased by 1.8 times in comparison to WT (from 243000 cycles for WT to 442000 cycles for SP);  for the Q&T specimens increased by 4 times in comparison to SP specimens (from 442000 cycles for SP to 1770000 cycles for Q&T).

Fig. 4. Comparison of the S-N curves for 51CrV4 spring steel.

4. Conclusion Based on the results of the experiment, it is evident that both strengthening processes, namely Q&T and SP, have significant effect on increasing fatigue strength 51CrV4 steel. In the case of Q&T steel, a 5.3% increase was observed in comparison to WT. On the other hand, a 1.5% increase was observed for SP specimens. The fatigue life of spring steel, after both pr ocesses, increased between 45 ÷ 86.3 %. The Q&T specimens have the greatest ultimate strength and the highest yield point. While the SP specimens did not have a definite yield point. The degree of hardening of the Q&T specimens surface layer was 52%, however it was 22.6% after SP. The highest roughness was observed for shot peened 51CrV4 steel, which was most likely affected by the small dimples left from the operation. In conclusion, it can be stated that the mechanical properties and microhardness of 51CrV4 steel after Q&T and SP are closely related to fatigue strength. Acknowledgements This work was supported by the European Research Agency - FP7-PEOPLE-2011-IAPP - grant agreement No. 284544. Experiments were performed using aperture completed thanks to financial support of the POPW 01.03.00 18-012/09-00 and UDA-RPPK.01.03.00-18-003/10 projects co-financed by the European Union from the European Regional Development Fund for the years 2007-2013.

References

Babu S.S., 2007. Classification and Mechanisms of Steel Transformation, in Steel Heat Treatment Metallurgy and Technologies, In: Totten GE, Editors. New York, Taylor & Francis Group, pp. 107-108. Benedetti M., Bortolamedi T., Fontanari V., Frendo F., 2004. Bending fatigue behaviour of differently shot peened Al 6082 T5 alloy.