PSI - Issue 5

Przemyslaw Strzelecki et al. / Procedia Structural Integrity 5 (2017) 832–839 Przemyslaw Strzelecki et al. / Structu al Integrity Procedia 00 (2017) 000 – 000

5

836

a)

b)

S u

S u

Stress amplitude , S a (log) S e

Stress amplitude , S a (log) S e S GCF

b

1

1

m

1

m'

N k

N k

B

N GCF

N up

1

Number of cycles, N (log)

Number of cycles, N (log)

Fig. 2 Illustration of the S-N curve for S-N a) model II, b) model III

0.2 1

  

  

 a HB c

3.4



,

(13)

B



   

   

 GCF N N S S   0.2 GCF k

e

,

(14)

a



0.2



   

   

0.2

0.2





S N



e GCF

k GCF

,

(15)

 c S N

 N N 0.2 GCF 

0.2



k



    HB

   

   

1 / 3

HB

HB

0.233

120

1 / 3 1.7







    HB

HB

0.0105

120



k N

,

(16)

10



  HB



 120

1 / 3 

,

(17)

S

HB

0.138







GCF

This approach will be hereinafter referred to as model III. For structural elements, this method proposes that the stress amplitude is multiplied by K t stress concentrator factor. Schematic representation of this model is presented in Fig. 2 b). The authors of the model assumed applicability of this model to steel materials. Both these methods require the same input values, i.e. material hardness.

3. Verification of presented models

Structural steels and an aluminium alloy were used to perform verifications of the described models. The mechanical properties of these materials are presented in Table 1. The material hardness was measured using Rockwell method, where scale C or B was applied, depending on the material hardness. Then, the obtained results were converted to Brinell scale values as per PN-H 04357 (1993). The mechanical properties of materials, derived from literature, are presented in Table 2, where the authors of these tests conducted the measurement using the Brinell or Vikers method. For the latter measurement method, the obtained results were converted to Brinell scale values as per PN-H 04357 (1993).