ROpt of a welded link

In order to reduce the weight of a welded link of a VOLVO wheel loader, a shape optimisation of the structure was performed. The aim of the optimisation was to minimise the weight of the link while increasing or maintaining it's service life. The service life is predicted using fracture mechanics and stress intensity factors (SIF) were used as a constraint in the optimisation.


Geometry of the optimised link. The entire FE-model including loads and boundary conditions was imported into ROpt. The fork end of the link where parametrisized using eleven independent shape variables and six more controlled the ring end. An extensive amount of stress constraints were used in weld areas to control the optimisation and keep stresses within allowed limits. Linked design variables were used to maintain constant element size around the crack tip.

The optimisation gave the following results:

• -10% weight reduction of the complete link
• 0% stress increase in fatigue critical areas of fork end
• -8% delta Keff (SIF) in root crack of ring end

Conclusion:

By using ROpt it is possible to perform fracture mechanics together with optimisation. In this project the weight of the link were reduced and the predicted service life increased.