Numerical modeling of drilling

Drilling is a material-removal machining process widely used in industry for its robustness and high productivity. This process creates cylindrical holes in a solid material using a cutting tool: the drill. As drilled holes are often intended to facilitate the assembly of various structures, drilling is one of the most widespread processes in many leading-edge industrial sectors (automotive, aerospace, energy, medical, etc.).

Despite its ubiquity in industry, drilling is a complex process to study, due to the cylindrical shape it produces. Indeed, cutting mechanisms are not directly observable, as they occur in a confined environment throughout the drilling phase. This geometric specificity contributes to concentrating all the physical phenomena in a restricted volume of material. For this reason, drilling is often considered to be the most penalizing machining operation for both tool and material.

The applications of this process mainly concern metals and their alloys, and in particular those considered "difficult to machine", such as titanium alloys and nickel-based superalloys. This class of materials offers a high level of performance in terms of mechanical strength. On the other hand, their mechanical and metallurgical characteristics are at the root of their poor machinability, and mean that machined functional surfaces need to be closely monitored.

Despite its robustness, the drilling process induces residual stresses that are often difficult to understand. These can affect the quality of drilled holes in terms of fatigue life. In an increasingly competitive industrial context, companies are seeking to optimize production costs and lead times, particularly for parts with very high added value. That's why mastery of manufacturing processes and their impact on innovative materials is a key success factor.

In this context, numerical modelling of the drilling process appears to be a privileged means of better understanding the mechanical consequences induced by the phenomena brought into play inside a drilled hole. The aim of this article is to take stock of the numerical modeling methods used in the drilling process, using various examples. The first part of the article deals with the drilling process and the difficulties involved in multiphysics modeling. The second part focuses on the modeling of thermomechanical phenomena at play during the drilling operation. Finally, before concluding on the prospects of the article, the third part presents various application cases, including the modeling of residual stresses induced by the process.