PSI - Issue 42
R. Fernandes et al. / Procedia Structural Integrity 42 (2022) 992–999 Fernandes et al./ Structural Integrity Procedia 00 (2019) 000 – 000
997
6
10 1
10 1
300ºC stress relief As-built
T6 As-built
Ă
Ă
10 0
Ă
10 0
Ă͕Ğ
Ă͕Ğ
10 -1
10 -1
Ă͕Ɖ
Strain amplitude (%)
Strain amplitude (%)
Ă
Ă͕Ɖ
(a)
(b)
Ă͕Ɖ
Ă͕Ɖ
10 -2
10 -2
10 1
10 2
10 3
10 4
10 5
10 6
10 7
10 1
10 2
10 3
10 4
10 5
10 6
10 7
Number of reversals to failure
Number of reversals to failure
10 1
10 1
250ºC stress relief + HIP As-built
250ºC stress relief As-built
Ă
Ă
10 0
10 0
Ă
Ă
Ă͕Ğ
Ă͕Ğ
10 -1
10 -1
Strain amplitude (%)
Strain amplitude (%)
Ă͕Ɖ
Ă͕Ɖ
Ă͕Ɖ
(c)
(d)
Ă͕Ɖ
10 -2
10 -2
10 1
10 2
10 3
10 4
10 5
10 6
10 7
10 1
10 2
10 3
10 4
10 5
10 6
10 7
Number of reversals to failure
Number of reversals to failure
Fig. 4. Strain-life relationships: (a) T6; (b) 300ºC stress-relief; (c) 250ºC stress-relief; and (d) 250ºC stress-relief and HIP treatment. The dashed lines represent the strain-life relationships (total strain and plastic strain components) for the as-built condition.
from the that of the as-built condition, the total strain versus life curves are almost overlapped for numbers of reversals to failure lower than 10 6 . On the contrary, the 300ºC stress relief treatment, see Figure 4(b), introduces a significant change in the total strain versus life relationship for 2 N f values lower than 10 4 . The above-mentioned function is shifted to upwards in the low-cycle fatigue region and then tends to overlap the as-built function for higher fatigue lives. In relation to the 250ºC stress relief treatment (see Figure 4(c)) and the 250ºC stress relief with HIP treatment (see Figure 4(d)), it can be concluded that the strain-life relationships are relatively similar which suggests, as referred to above, that the HIP treatment has not caused a limited effect on the fatigue behaviour of the SLM-manufactured AlSi10Mg aluminium alloy. In these two cases, the differences in terms of total strain versus life relationships relative to the as-built condition are not much expressive. The more relevant differences are concerned the plastic strain versus life relationships. Overall, the functions of the treated conditions are shifted upwards when compared with the non treated material. As far as the energy-based relationships are concerned, the total strain energy density ( W T ) is one of the most popular energy-based parameters to deal with fatigue design problems. Figure 5 shows the typical relationships between W T and the number of reversals to failure for the different material conditions. In this study, the total strain energy density was calculated from the mid-life hysteresis loops via the sum of both the plastic and the elastic positive components. As can be seen in the figure, irrespective of the material condition, the datapoints are relatively close and follow approximately the same trends. Moreover, it is interesting to note that these energy-life results can be fitted by a straight line on log-log scales, i.e. a power function (see dashed line in Figure 5), and that a single function can
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