PSI - Issue 54

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Martin Matušů et al. / Procedia Structural Integrity 54 (2024) 135 – 142 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 3. a) Comparison of heat-treated specimen with T200 on two different printing platforms. b) Comparison of heat-treated specimen with T300 on two different printing platforms.

Lastly, we compare specimens from platform n°3 and from platform n°5, which used the most reused printing powder. This comparison is illustrated on specimens with the same T300 heat treatment. The differences between these platforms are evident across the entire S-N curve, as illustrated in Figure 3 b). Notably, the slope of the S-N curve in the region of finite life shows a noticeable disparity, as does the transition to the fatigue limit domain. Interestingly, it should be mentioned that the transition to the quasi-static domain is higher for the more reused powder from platform n°5, which is an intriguing result. As mentioned previously, the platform n°5 differed slightly from the other platforms due to the addition of a fresh powder delivered by another powder manufacturer. However, even with the addition of new printing powder, the fatigue strength in the HCF domain is significantly lower compared to the previously tested cases, as depicted in Figure 3 b). To quantify the reduction in fatigue performance across the various platforms, the fatigue strengths  FS6 were compared at 10 6 cycles as delivered by the K&V model, see Table 3. The same table also contains the values of the slope of the S-N curve as obtained from the common power law. According to [4] the value of k is much closer to a specimen with a notch ( k = 5), this indicates steeper decline to the HCF domain compared to non-notched specimen as Haibach states that is k = 15. In this case not a notch causes shorter lifespan in HCF but the inner structure. As evident from Table 3, there is a consistent decrease in the observed fatigue strength for each successive printed platform. Notably, a distinct trend emerges in platform n°3, where the fatigue strength amplitudes are similar across all heat treatment (HT) configurations. This observation suggests that the amplitude decrease experienced by each HT configuration would likely persist. The fatigue strength reduction from platform n°1 to n°3 was 16.6% for the T240 configuration and 30% for the T300 configuration and the transition from platform n°3 to n°5. The most substantial variation in performance is observed within the T300 series. The slope parameter remains consistent among HT configurations for different printed platforms, except for the T300 series, where a significant change in the slope is evident. This discrepancy could potentially be attributed to the introduction of a new fresh powder, albeit of the same specifications but from a different brand. Despite the powder adhering to the same specifications, discernible changes in fatigue performance are evident from both Table 3 and Figure 3a. Ordinarily, the addition of fresh powder should enhance fatigue performance; however, this case demonstrates a contrary outcome.