Issue 30

P. Livieri, Frattura ed Integrità Strutturale, 30 (2014) 558-568; DOI: 10.3221/IGF-ESIS.30.67

phase shift angle φ

biaxiality ratio λ

Data Set

R

Load case

σ A

[MPa]

τ A

[MPa]

A B C D E

-1 -1 -1 -1 -1 -1

tension torsion

89.9

151.9

combined combined combined combined

0

1 1

74.0 82.6 85.9 99.7 57.5

74.0 82.6 51.5 59.8

90 90

0.6 0.6

F

0

G H

0 0 0 0

tension torsion

109.5

I J

combined combined

0

1 1

56.4 53.3

56.4 53.3

90

Table 2: Results taken from [20].

N UMERICAL S IMULATIONS

T

he proposed approaches are based on the linear elastic stress field. Several FE tools can easily compute the linear elastic stress filed. In the following, Comsol multiphysics FE software has been used because it is the easiest way to solve the Helmholtz equation Eq. (3), necessary for IG, due to the built-in PD equation solver. Authors developed another way to solve the IG with others FE software [25], but it turns out approximate and a direct solution is more accurate. TCD and SED do not need any specific software to be solved. A free mesh was applied on the most part

of the geometry; a mapped mesh was used in the proximity of the notch tip. The investigated geometry has a tensile stress concentration factor K t,σ

and the torsional stress concentration factor K t,τ

respectively equal to K t,σ

= 7.467 and K t,τ

= 3.178.

Figure 3: mapped mesh on the notch tip (element size=r/6.25).

A PPLICATION OF EFFECTIVE STRESS THEORIES

F

or the actual computation of the effective values, according to presented theories, some further descriptions are necessary. First, an equivalent stress value shall be chosen for IG and CD approaches, see Eq. (3) and (5).

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