PSI - Issue 37

3

Carl Fällgren et al. / Procedia Structural Integrity 37 (2022) 948–955 Carl Fällgren / Structural Integrity Procedia 00 (2019) 000 – 000

950

Figure 1: Cyclically stabilised stress-strain curve and static tensile curve for W360.

2.1. Material modelling

Components are subjected to autofrettage before they are used in their designated environments. The compressive residual stresses introduced during the autofrettage pressure relief are highly affected by the material's initial unloading behaviour, especially by the Bauschinger effect (cf. Bauschinger (1886)). Therefore, this behaviour has to be taken into account when performing autofrettage simulation in order to describe the residual stress field in the components, see Herz et al. (2006), Thumser (2009), Herz et al. (2011) and Chen (1986). To account for this effect, different material modelling strategies are possible. In this report, the initial material loading curve is used during the simulation of the autofrettage pressure-build up. The autofrettage pressure relief is simulated by switching the material behaviour to the doubled cyclically stabilised material curve. The Besseling material model, cf. Besseling (1958), was used to describe the material behaviour. The data points for feeding the Besseling model were taken from the curves shown in Fig. 1. 3. Finite element model and residual stress calculation For the simulation of the autofrettage process finite element models were used which represent a sixteenth of the two geometries used for the real component-like specimens in the project. The two specimen geometries are shown

Figure 2: Geometries of the component like specimens and finite element model.