Physics-based methodology for the non-destructive measurement of residual stresses during hard turning

• Applicant: Professor Dr.-Ing. Thomas Bergs
• Subject Area: Metal-Cutting and Abrasive Manufacturing Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 559207441

In manufacturing, the surface integrity influences the entire production chain, making regular measurements necessary to adjust the process parameters. Advances in high-strength cutting materials have made hard turning of hardened workpieces possible as an alternative to grinding processes. However, hard turning without cooling lubricant results in high mechanical and thermal loads, which can lead to undesirable changes such as white layers and tensile residual stresses (RS). These changes promote cracks and are therefore safety-relevant, which requires careful monitoring of the surface integrity.The surface integrity of the workpiece is crucial for the operational behavior of components such as gears and roller bearings, particularly in drive technology. Frequent testing methods are destructive in nature, which is why alternatives such as eddy current testing, ultrasonic testing and Barkhausen noise analysis (BNA) are being sought. The latter is particularly suitable for ferromagnetic materials in the process.Data-driven or empirical models are usually used to extract boundary zone quality information from the magnetic Barkhausen noise signal (MBN signal). However, these do not offer general applicability. Physics-based models, on the other hand, are more widely applicable but often difficult to link directly to material properties. A physics-based model is proposed to measure residual stress depth profiles using BNA. The project is focusing on the material 100Cr6.The work program comprises several work packages (WP). In WP 1, various mechanically and thermally influenced samples are produced and investigated. The empirical investigations include the production of different samples by means of deep rolling and laser treatment as well as their analysis by metallographic methods and MBN measurements. These serve as the basis for the physics-based model developed in WP 2 to determine the RS depth profiles. This model will be validated in WP 3 and finally transferred to the hard turning process in WP 4. Overall, the project aims to develop a method for the non-destructive measurement of RS depth profiles during hard turning, thereby reducing rejects and increasing component service life.

• DFG Programme: Research Grants