Study of the local forces along a drill edge – comparison of two methodologies

Abstract

In aerospace applications, drilling is one of the most common operations. However, this machining stays complex and expensive, especially in hard to cut materials. Because of the closed aspect of the operation, the measure or evaluation of the phenomenon on the cutting area is difficult, especially decomposing the forces for various parts of the edge. This study focuses on two methodologies allowing a study of the forces along the drill’s edge. The first methodology is based on a physical decomposition of the drill edge. This approach, like the following one, is based on the hypothesis of the independency of the segments: each part of the edge is cutting the material independently from its neighbors (for the chip flow or the local forces). By measuring the forces on the drilling of samples of various external diameters, smaller or bigger than the drill diameter, and with or without pilot hole, the reconstruction of the forces along the drill edge and on the margin could be done. The second methodology, still based on the hypothesis of the independency of the segments, decomposes the forces during the drill point sinking on the material. On each entry altitude, the drill edge engagement is known, allowing the recomposition of the forces along the edge and on the margin. Experiments have been done to compare the two methodologies with one drill and one batch of Ti6Al4V alloy.