PSI - Issue 10

D.G. Ntritsos et al. / Procedia Structural Integrity 10 (2018) 288–294

291

D.G. Ntritsos et al. / Structural Integrity Procedia 00 (2018) 000 – 000

4

 The test is carried on until the specimen breaks or the revolution counter surpasses the 10 7 mark.  The specimen is then removed and placed on an individual case for further study.

3. Analytical approach

The analytical approach consists of two studies. Firstly the calculation of the stand-alone notches stress concentration factors with the existing analytical theory and then after the simulation of the experiment procedure using the Finite Element Analysis.

3.1. Stress concentration factor of stepped shaft

According to Peterson (1953) the stress concentration factor of a shaft step can be accurately determined using data from past photoelastic tests. The static stress concentration factor K t of a shaft stepped area is calculated accordingly using Eq.(1):

2

3 C D D D 4 2       h ( 2 )   h C 2       h

3

(1)

  K C C

t

1

2

Where D is the larger shaft’ s diameter and h the step height. Applying Eq.(1) for the tested single stepped specimen geometry is calculated below. Thus for 2.5 6.25 2 20 0.4      h h r r The C parameters are

h

h

1 1.232 0.832   C *

0.008 3.262  *



r

r

h

h

C

3.813 0.968 *

*

0.26

3.018

  



 

2

r

r

h

h

C

7.423 4.868 *

0.869 0.68425  *

 



3

r

r

h

h

C

3.839 3.070 *

0.6 0.086  *

  



4

r

r

Finally from the Eq.(1) K t is

2

3

2       h

2       h

2 2.34 h

     

  K C C

C

C







t

1

2

3

4

D D D Thus the static stress for a bended stepped shaft is calculated as follows

32 ( 2 )  M π D h

 σ K

(2)

s

t

3

Where M is the applied bending load.