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Simulation of linear-elastic fracture mechanics with Ansys
Determination of stress intensity factors using FEM

Fracture mechanics evaluation for estimating brittle fracture resistance

Sector: Machinery and plant engineeringSpecialist field: Structural mechanics

CADFEM determined stress intensity factors for a wind turbine manufacturer using FEM analysis in Ansys Workbench.

Summary

Task

A fracture mechanics evaluation is to be performed for a transition radius on a transmission component to estimate the brittle fracture resistance under cold climate conditions. The crack geometry is assumed to be a semi-elliptical surface crack.

Solution

Ansys provides a number of tools for determining fracture mechanics parameters, with which this can be solved very conveniently.

Customer benefits

The applied crack can be correctly assessed in terms of its effect.

Project Details

Task

A fracture mechanics evaluation is to be performed for a transition radius on a transmission component to estimate the brittle fracture resistance under cold climate conditions. The crack geometry is assumed to be a semi-elliptical surface crack. Since only a limited geometry variety is available for the analytical solutions, which can be found in the literature, it is still an understandable disadvantage. However, the fact that the analytical models often only provide results for KI mode I loads, it can easily lead to a significant false evaluation of a crack if KII and KIII are neglected.


Customer Benefit

  • For the issue at hand, no analytical approaches are available for mode II and III loading.
  • The FEM analysis shows that the stress intensities of all modes are of the same order of magnitude (see diagram).
  • The effect of the applied crack can thus be correctly assessed.

Solution

Ansys provides a number of tools for determining fracture mechanics characteristic values. A new method has been integrated into version 12, which makes it very easy to determine fracture-mechanical parameters in connection with the ANSYS® Workbench™ environment. In the present case, the component is first calculated without a crack. In a second step, assuming a small crack, the highly stressed area of the transition curve is examined in a submodel with a crack. The geometry of the submodel is set up parametrically, so that slightly different crack sizes and crack positions can be examined. The curves of stress intensity factors KI, KII and KIII are output as a result.

Images: © REpower


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