PSI - Issue 14

K. Shridhar et al. / Procedia Structural Integrity 14 (2019) 375–383

380

6

K. Shridhar et al./ Structural Integrity Procedia 00 (2018) 000–000

6. Results and Discussions A geometrical non-linear static stress analysis has been carried out to estimate the stress concentration factor for different radius ratios. An attempt is made to investigate the effect of loading angle on the stress concentration factor. Further, fatigue crack growth life of the lug with through the thickness crack emanating from the lug hole has been evaluated and stress intensity factor for varied crack lengths is evaluated using analytical relations and FE analysis. MVCCI method has been used in the determination of stress intensity factor through FE analysis. 6.1. Determination of stress concentration factor. The stress concentration factors for radius ratios 1.5,2 and 3 have been found by both FEA and analytical approach. Results are listed in table 2.

Table 2. Analytical and FEA stress concentration factor results

Analytical K t

Applied stress (MPa)

FEA K t

o in

R o /R i R

R i in mm Max stress (MPa)

Sl.no

mm

1 2 3

1.5

50 50 50

33.34

209 181 171

50

4.2

4.4

2 3

25

66.66

2.72 1.71

2.75 1.72

16.67

100

Analytical and FEA results are in good agreement with each other. From the above data it was observed that as radius ratio increases, stress concentration factor reduces. A maximum stress concentration factor 4.2 was observed for radius ratio 1.5 and minimum stress concentration factor 1.71 was observed for radius ratio 3.Stress concentration factor v/s radius ratio plot as shown in fig 3(a). From the fig 3(b) it is observed that maximum stress concentration occurs at a location approximately perpendicular to the loading direction.

b

a

0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0

Analytical FEA

Kt

1

1,5

2

2,5

3

3,5

Ro/Ri

Fig 3 .( a) K t v/s Radius ratio; (b) Stress distribution plot for radius ratio 3 loaded in axial direction.

6.3. Estimation of stress intensity factor. Radius ratio 1.5 fig 4(a): For the 2mm crack, SIF observed was 13MP√m.For 4mm crack it shows significant rise by 30%.Further, for each 2mm crack increments average 15.5% rise was observed. The SIF for 12mm crack was 30.1MP√m. Radius ratio 2 fig 4(b):For the 2mm crack, SIF observed was 10.9MP√m.For 4mm crack it shows significant rise by 28%.Further, for each 2mm crack increments average 9.1% rise was observed. The SIF for 20mm crack was 27.9MP√m. Radius ratio 3 fig 4(c):For the 2mm crack, SIF observed was 9.1MP√m.For 4mm crack it shows significant rise by 18.6%.Further, for each 2mm crack increments average 3.3% rise was observed. The SIF for 20mm crack was 14MP√m.