test. Failure of the specimen was based on
the change in resonance frequency. When
micro-cracking led to final fracture, the
natural frequency of the system reduced
compared to operating frequency of the
system and the test was terminated.
Figure 5 shows exemplary surface
micrographs for the two investigated
batches1. The remnant porosity is viewed
as only the gas porosity. A difference in the
pore fraction of the samples without and
with base plate heating was observed. In
the samples with base plate heating, large
size gas pores which are very critical in
fatigue performance were absent. The
reduction of large pores is attributed to the
de-gassing in the manufacturing chamber
due to pre-heating.
Figure 6 represents S-N curves for
batches I and II in the region from high
cycle fatigue to very high cycle fatigue, cf.
2. Experiments showed that fatigue
fracture occurred beyond the high cycle
fatigue region in both batches. Results of
the experiments indicated that fatigue
strength in very high cycle regime of
114 SHOWCASE 2020 \\ AEROSPACETESTINGINTERNATIONAL.COM
samples manufactured with base plate
heating was about 45% higher than fatigue
strength of sample without base plate
heating. Fatigue strength at one giga cycle
for batches I and II was 60.5 ± 4.7MPa and
88.7 ± 3.3MPa respectively. This increase in
strength is attributed to elimination of the
New developments in analytical and
testing systems enabled going beyond
previously known limits of knowledge.
This opens the door towards more
intensive testing in the most realistic
New capabilities in analytical and
testing systems are providing R&D
departments in aerospace industries and
researchers in general with powerful tools
to further investigate the effect of
processing parameters on the resulting
functional performance for enhanced
understanding of process-structureproperty
relationships and knowledge of
component capabilities in service-relevant
loading ranges and scenarios.\\
Dr Olesia Khafizova is market manager composites
and additive manufacturing at Shimadzu’s
European Innovation Center
1 Siddique, S.; Imran, M.; Wycisk, E.; Emmelmann,
C.; Walther, F.: Influence of process-induced
microstructure and imperfections on mechanical
properties of AlSi12 processed by selective laser
melting. Journal of Materials Processing Technology
221 (2015) 205–213.
2 Siddique, S.; Awd, M.; Tenkamp, J.; Walther, F.:
High and very high cycle fatigue failure mechanisms
in selective laser melted aluminum alloys. Journal of
Materials Research 32, 23 (2017) 4296-4304.
3 Pyttel, B.; Schwerdt, D.; Berger, C.: Very high cycle
fatigue – Is there a fatigue limit? International
Journal of Fatigue 33 (2011) 49–58.
4 Benedetti, M.; Fontanari, V.; Bandini, M.: Very
high cycle fatigue resistance of shot-peened high
strength aluminium alloys. Experimental and
Applied Mechanics 4 (2013) 203–211.
5 Morrissey, R.J.; Nicholas, T.: Fatigue strength of
Ti-6Al-4V at very long lives. International Journal
of Fatigue 27 (2005) 1608–1612.
6 Siddique, S.; Imran, M.; Rauer, M.; Kaloudis,
M.; Wycisk, E.; Emmelmann, C.; Walther, F.:
Computed tomography for characterization of
fatigue performance of selective laser melted parts.
Materials & Design 83 (2015) 661-669.
7 Awd, M.; Siddique, S.; Johannsen, J.;
Emmelmann, C.; Walther, F.: Very high-cycle
fatigue properties and microstructural damage
mechanisms of selective laser melted AlSi10Mg alloy.
International Journal of Fatigue 124 (2019) 55-69.
4 // Specimen geometry
for ultrasonic fatigue tests
5 // Exemplary surface
micrographs for sample
without base plate heating
(a) and with base plate
6 // S-N characterization
for ultrasonic fatigue