Pipe With Weld

This sample application shows the effect of material property assumptions for a fatigue crack growing at a weld in a pipe. This type of configuration was presented in a paper using the crack-block methodology (see Reference section at the end of the page). The example here uses the approach described in the paper with the remeshing method in Zencrack.

The pipe is modelled with hex elements and a clearly defined region for the weld, as shown in Figure 1. Constant amplitude cyclic internal pressure is applied. Two analyses are performed:

• Same Youngs's modulus, Poisson ratio and crack growth law for pipe and weld regions.
• Different Youngs's modulus, Poisson ratio and crack growth law for pipe and weld regions.

The issue for this type of model when different material properties are used is the conflict between requirements for modelling the material boundary and the crack region. This is described in more detail in the reference paper. The solution is the use of user subroutines to allow the crack modelling to determine the mesh, with user subroutines used to impose the correct material definitions in the remeshed region around the crack.

Figures 2 and 3 show the effect of the change in material definition on crack shape development, which is smooth in the single material model, but irregular in the two material model.

Animations of the crack growth for the two simulations are shown in Figures 4 and 5.