Virtual design procedure of material structure for optimal fatigue resistance of highly loaded applications

Purpose and goal

The main aim with the project has been to support Scanias transition to virtual product development where both hardening process and mechanical loading are simulated. The project adress the link between microstructure of the steel, hardness and fatigue properties. This allow for optimization of the heat treatment to obtain the optimal case depth with respect to fatigue properties. As a result, the case depth may be reduced for some components leading to a reduction of COx emissions from productions. Potentially this allow for lighter components beneficial for fuel economy.

Expected results and effects

The key result of the project is a model for predicting fatigue life of case hardened components. The proposed model calculates the probability of fatigue failure and, if failure occurs, the probability that the component survives a certain number of load cycles. This model will be a key component for development of new drive train components to reduce time to market and increased profitability.

Planned approach and implementation

Fatigue testing of case hardened specimens has been performed on series with varying hardness and microstructure. Controlling the microstructure efficiently proved difficult and the data only allowed for correlation versus hardness. Additional testing is required to obtain a correlation to microstructure with respect to fatigue properties. The model was used to predict fatigue failure for initiation at the gear tooth root and subsurface on the tooth flank.