Issue 33
C. Bagni et alii, Frattura ed Integrità Strutturale, 33 (2015) 105-110; DOI: 10.3221/IGF-ESIS.33.14
directly be taken equal to the average inter-aggregate distance, the results generated by testing the un-notched specimens being used to determine a suitable value for the reference strength.
Linear-elastic stress fields - Batch A
Linear-elastic stress fields - Batch B
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
y,max [MPa]
y,max [MPa]
Linear-elastic stress-distance curve (K t =4.32)
Un-notched Material Endurance Limit 0,MAX =5.1 MPa
Un-notched Material Endurance Limit 0,MAX =3.3 MPa
Linear-elastic stress-distance curve (K t =4.32)
L/2=2.9 mm
L/2=2.9 mm
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0
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20
Distance, x [mm]
Distance, x [mm]
Figure 3 : Critical distance L determined for Batch A and Batch B according to the PM.
Linear-elastic stress fields - Batch A Un-notched Blunt Intermediate Sharp Un-notched Material Endurance Limit 0,MAX =3.3 MPa Error= +20%
Linear-elastic stress fields - Batch B Un-notched Blunt Intermediate Sharp Un-notched Material Endurance Limit 0,MAX =5.1 MPa Error= +20%
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
y,max [MPa]
y,max [MPa]
Error= -20%
Error= -20%
l =2.05 mm
l =2.05 mm
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Distance, x [mm]
Distance, x [mm]
Figure 4 : Accuracy of GE applied by taking l = 2.05 mm, Eq. (6) .
Linear-elastic stress fields - Batch A Un-notched Blunt Intermediate Sharp Un-notched Material Endurance Limit GE0,MAX =2.8 MPa
Linear-elastic stress fields - Batch B Un-notched Blunt Intermediate Sharp Un-notched Material Endurance Limit GE0,MAX =4.3 MPa Error= +20%
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
y,max [MPa]
y,max [MPa]
Error= +20%
Error= -20%
Error= -20%
l =4.0 mm
l =4.0 mm
0
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20
0
5
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Distance, x [mm]
Distance, x [mm]
Figure 5 : Accuracy of GE applied by taking l equal to the average inter-aggregate distance ( l = 4 mm).
The charts reported in Fig. 5 show the linear-elastic gradient-enriched stress-distance curves plotted, at the endurance limit, under the maximum loading in the cycle. According to this figure, the reference strength, GE0,MAX , determined from the results generated by testing the un-notched specimens was equal to 2.8 MPa for Batch A and to 4.3 for Batch B. These diagrams clearly prove that the use of the gradient-enriched notch tip stresses determined by taking l equal to the average
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