Page 333 - Biaxial Multiaxial Fatigue and Fracture

Influence of Defects on Fatigue Life of Aluminium Pressure Diecastings 317

This equation represents a good tool for fatigue life prediction of diecastings. In fact, a
diecasting company, using a non-destructive test, like the X-Rays control, can detect the
maximum defect of one component. Considering the size of the detected defect and the
estimated service stress level of the component, it is possible to estimate the number of the
cycles that the component can withstand until breaking.

150 1000

-
m 800 g-
a
%
z, 100 W
al L
-0 t‘ 600 $2
.- E
3
m
a - 400 .-
50 m
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- 200 2

0 10
100 1000 lo4 lo5 lo6 10’
Number of Cycles

Fig. 20. Effect of the stress amplitude (upper curve) and mean pore diameter (lower curve) on
the number of cycles of all samples. The mean diameter of each sample is indicated with the
standard deviation.

The results achieved represent the first part of a more complete study about the influence of
defects on the fatigue life of diecasting components. The second part of the work will include
fatigue tests in the aluminium rocking arm of the Fig. 21. Using the Solid Works software, the
displacements and the equivalent stress levels will be calculated by the finite element method
(FEM). This allows the localization of the regions, which will preferentially suffer fatigue
fracture. Using the X-Rays analysis, all large size defects present in the parts will be identified
and the parts separated in different lots, characterized by the maximum defect size and location.
The results of the fatigue tests will then be compared with the ones just presented. It is
expected that the conclusions of the study can supply interesting data for the software under
development.