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Residual stresses induced by hard‐turning are the result of a combination of mechanical and thermal effects, leading to a compressive or tensile stress state at the surface, depending on the machining parameters and the tool wear state. In this work, the residual stress depth profiles generated on steel grade F‐521 (AISI D2) by hard‐turning with tools of different wear states were measured by X‐ray diffraction. An integral method was applied to determine the full stress tensor and the stress gradient tensors in the tangential, radial and depth directions. Both macroscopic and microscopic residual stresses were investigated. Compressive residual stresses were measured below the surface in all machined specimens. The magnitude of the compressive stress was much lower and the depth was much shallower when using new cutting tools than when using worn tools. However, the sample that has been hard‐turned with a worn tool suffered strong microstructural changes in a layer more than 150 µm thick, especially at the surface, where the presence of a hard and very brittle layer of untempered martensite was evidenced.

The present work focuses on the manufacturing of Ti-6Al-4V parts using hot single point incremental forming (SPIF), a non-conventional forming technology mainly oriented toward the fabrication of prototypes, spare parts, or very low volume series. In the used procedure, the entire sheet is heated and kept at uniform temperature while the tool incrementally forms the part, with the limited accuracy of the obtained parts being the major drawback of the process. Thus, this work proposes two approaches to improve the geometric accuracy of Ti-6Al-4V SPIF parts: (i) correct the tool path by applying an intelligent process model (IPM) that counteracts deviations associated with the springback, and (ii) skip overforming deviations associated with the deflection of the sheet along the perimeter of the part based on a design improvement. For this purpose, a generic asymmetric design that incorporates features of a typical aerospace Ti-6Al-4V part is used. The results point out the potential of both solutions to significantly improve the accuracy of the parts. The application of the IPM model leads to an accuracy improvement up to 49%, whereas a 25.4% improvement can be attributed to the addendum introduction. The geometric accuracy study includes the two finishing operations needed to obtain the part, namely decontamination and trimming.

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