Finite Element Simulation of drilling in titanium alloy plates: Burr Formation and Structural Implications

Burrs are unwanted material projections formed during machining processes, such as milling, drilling, turning, or grinding, that deviate from the ideal geometry of the workpiece. Their presence has long been recognized as detrimental for both structural integrity and manufacturing efficiency. On a mechanical level, burrs can reduce strength under static and fatigue loading, damage protective coatings, and generate subsurface defects or contamination. Functionally, they interfere with assembly by causing misalignments and increasing surface roughness, while from a production perspective they require costly, labor-intensive, and non-value-added deburring operations. Indeed, deburring may account for 5–30% of the total manufacturing cost, with significant implications for cycle time, manpower, and rejection rates, especially in the case of small and high-precision aerospace components. The aerospace industry is particularly affected by burr formation, since drilling represents one of its most common processes. A civil aircraft may require up to three million drilled holes, mainly for the mechanical fastening of aluminum, titanium, or hybrid stacks. Current standards demand that burr height remain below 100 μm, yet such precision is difficult to achieve without deburring. Traditionally, assembly involves intermediate steps of disassembly for cleaning and deburring, which add no value to the product. To overcome this limitation, the One Way Assembly (OWA) concept has been introduced: holes are drilled directly during assembly without subsequent separation. This method offers clear advantages in terms of cost reduction, lead time, automation, and production planning, and has been progressively adopted by leading manufacturers such as Boeing and Airbus. However, eliminating deburring raises critical challenges, particularly concerning burr-induced contamination and chip entrapment at the interface, which may compromise joint fatigue performance. Effective implementation of OWA therefore requires improved control of drilling parameters, precise clamping strategies to minimize inter-part gaps, and robust inspection and predictive assessment methods. The aim of this project, conducted in collaboration with ISAE-SUPAERO, is to develop a finite element model of the drilling process for titanium alloy Ti6Al4V. The model is designed to predict final hole geometry and simulate burr formation mechanisms, with a particular focus on evaluating their influence on fatigue strength. By extracting residual stresses from the simulated hole walls and implementing them in numerical tensile tests, the work provides new insights into the correlation between burr presence, residual stress distribution, and structural performance.