PSI - Issue 75

Benjamin Causse et al. / Procedia Structural Integrity 75 (2025) 205–218 Author name / Structural Integrity Procedia (2025)

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2.2. Angle variation We propose to study the influence on the service life of a variation in the load angle of the main directions during a cycle, the other loading parameters being constant and such that : σ I (t) =  m +  R sin  t and  II =0. Since the Eurocode does not take this variation in loading angle into account, the Eurocode calculation will be the reference for a zero variation in loading angle ( =) . To be able to compare the two methods, we apply 2 successive events: a first event for  =0°, and a second event for pour  =  max varying from 0° to 90° in steps of 5°. For each event, we apply 2 harmonic cycles in R=0 ranging from 0 to 200 MPa (σI(t) =  m +  R sin ( t) and  II =0 with  m =  R =100 MPa). Dang Van can then be used to calculate the lifetime N DV =f(  ). The service life obtained for each value of  is compared with that of the Eurocodes N E =N DV (  =0). The N DV lifetimes according to the Dang Van criterion are obtained as a function of the maximum load angle rotation during the cycle noted  max , varying from 0° to 90°, according to the following load path scenarios (examples with a step  max of 5°):

 max = 0° : Harmonic oscillation from 0 to 200 MPa for  = 0° Assessment of the number of cycles N E (typical Eurocode service life reference).

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 max = 5° : Harmonic oscillation from 0 to 200 MPa for  = 0° Harmonic oscillation from 0 to 200 MPa for  = 5° Assessment of the number of cycles N DV (according to Dang Van)  max = x° : Harmonic oscillation from 0 to 200 MPa for  = 0° Harmonic oscillation from 0 to 200 MPa for  = x° Assessment of the number of cycles N DV (according to Dang Van)

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Figure 1 shows an example of stress tensor for  max max =30°.

Fig. 1. Loading angle variation study hypothesis (a) Calculation parameters and studied scenario (b) Example of stress tensor input for  max =30°