Life Assessment and Crack Growth Properties of Laser Cut Dual-Phase Steel
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The effect of laser cut-edges has been studied as a method for producing an optimum fatigue life performance of advanced high-strength steel. During this study, DP600 high-strength steel laser cut-edges have been fatigue tested under S-N and E-N fatigue loading regimes. The cut-edge surface characteristic properties and internal metallurgical alterations have been observed to directly influence fatigue life of the steel. This paper has investigated the crack initiation and growth properties of the initial crack to mode two. It is shown that alterations in the surface properties can be harnessed so that beneficial properties can be produced to retard crack initiation. It was determined that the laser power and cutting speed can be used independently to produce the appropriate balance between microstructure and optimum surface properties. Optimal fatigue lives were attained by minimizing the laser cut-edge surface damage, maintaining the formation of wide area striations and by forming a uniform layer of martensitic material close to the cut-edge. These results suggest that laser cutting can be used to enhance the fatigue life to failure of fracture-sensitive steel grades.
KeywordsLaser processing Laser cutting Fatigue life Crack growth
List of Symbols
Elongation to failure
Advanced high-strength steel
High cycle fatigue
Arithmetic mean of departures from the mean line
RMS of the R a
Maximum height of profile above the mean line
Maximum depth of profile below the mean line
Total R p − R v
The present research was funded by a grant from the Engineering and Physical Sciences Research Council (EPSRC). The author wishes to thank the support of Tata Steel during the pursuit of this research.
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