Colloquia

Summary

Rolled sheet metal plays a vital role in the modern world. A greater volume of material is worked by rolling than by any other metal deformation process. Many current day objects are constructed of rolled sheet metal. Unfortunately, there are production losses in the cold rolling process. A broader understanding of the cold rolling process can help to further reduce these losses. During the cold rolling process, friction plays an essential role. Multiple tribological mechanisms contribute to this friction. The abrasive wear mechanism of interest in this thesis is; ploughing. Ploughing is defined as a wear mode in which the substrate material is displaced from the path of the sliding asperity without shearing off. The velocity difference between the rolls and strip is relatively high, which makes the strain rates effect and its influence on the ploughing friction an important parameter during the process.

This thesis aims to validate the numerical model developed by Leon Jacobs. The simulations are based on a constitutive model by Bergström and later adapted by van Liempt. Multiple ploughing experiments have been executed to validate the simulations. Valuable data is collected during the ploughing experiments, for example, the coefficient of friction.

The ploughing experiments showed interesting results in comparison to the ploughing simulations. It is found that the order of magnitude is similar. In addition, the strain hardening effect due to the cold rolling process is visible in the results. In other words, samples with more strain hardening need more ploughing force per unit cross-sectional groove area. Furthermore, small amounts of buildup were found on the indentation pins. The buildup of material is not possible with only the ploughing mechanism. However, this can be caused by variation in material properties and/or surface characteristics. Furthermore, the strain rate effect occurring in the simulations could not be validated using the experiments. Moreover, when comparing the surface ploughing resistance and pre-strain for the experimental results with the simulation results, it can be seen that the simulations always resulted in a lower surface ploughing resistance. Considering the experimental results compared to the simulated results could help improve the simulation of the friction parameters during the cold rolling process.