Abstract
In this study, the fatigue crack growth (FCG) characteristics of the short surface crack was studied at various stress ratios, R, using the fine grained cemented carbide. The FCG law for the material was studied using two parameters, the maximum stress intensity factor Kmax and the stress intensity factor range ΔK. It was found that the relationship between the rate of FCG, da/dN and ΔK depends on the R value. In the da/dN vs. Kmax relation, at the region of high crack growth rate, the FCG rate was nearly constant by the value of Kmax without depending on R. However, in the low FCG rate region, the FCG rate tended to accelerate as R became lower. Therefore, it was difficult to specify da/dN as a single value at different R ratios using either ΔK or Kmax from the low speed region to the high-speed region. For that reason, the FCG behaviour of the material was studied based on the crack growth law, da/dN = AKmaxmΔKn. The values of m and n were obtained as 6.6 and 1.4, respectively. Therefore, it was found that the FCG rate of the cemented carbide was strongly dependent on Kmax rather than ΔK, like the FCG characteristics of ceramics.
Highlights
Cemented carbide is hard material and has excellent wear resistance, so it has been widely used in cutting tools and so on
It is expected that the initiation and growth behavior of the short surface crack are concerned with wear behavior of the mold [1]
fatigue crack growth (FCG) data obtained from experiments at various stress ratios R was plotted on the log-log graph
Summary
Cemented carbide is hard material and has excellent wear resistance, so it has been widely used in cutting tools and so on. Researches on the fatigue crack growth (FCG) behavior of the cemented carbide have been mainly conducted targeting the long through crack These studies were mainly conducted in the high Kmax area where the FCG speed is faster than 10−9 m/cycle or more. Llanes et al [3, 4] reported the FCG characteristics of the long through crack of the various cemented carbides Both of the above studies focused on the high-speed FCG zone, larger than 10−9 m/cycle. Ishihara et al [5] reported the FCG characteristics of the short surface crack at various stress ratios using the cemented carbide with comparatively large WC grain size. Consideration was given how the prediction accuracy in the crack growth amount was changed depending on whether FCG threshold is taken into consideration or not
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