Project Details
Projekt
Investigation of residual stress-related elementary processes for forged components in the manufacturing and operating phase
Subject Area
Primary Shaping and Reshaping Technology, Additive Manufacturing
Mechanics
Mechanics
Term
since 2017
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 374688875
Residual stresses (RS) have a significant influence on the operational behavior of formed components. The superordinate objective is therefore to specifically create an advantageous RS state in the component during the forming process, with forward rod extrusion serving as the reference process. For this purpose, the research project is aimed at generating an understanding of the formation and relaxation mechanisms of RS, identifying RS-relevant process factors and determining process-related measures for adjusting component properties in order to achieve an improvement in operating behavior as a result of the forming-induced RS state. In the first phase (start: 01/2018), RS development during component manufacture was investigated. For this purpose, the forming process was analyzed experimentally and numerically using the steels 1.4016 (ferritic) and 1.4462 (ferritic-austenitic). The investigations showed that reproducible introduction of RS and their modification by adjusting process parameters is possible. The measured and computed RS are in qualitative agreement. For numerical RS analyses, special subroutines were developed to track the RS state already during the forming process, for example by incompatibility densities as indicators for inherent distortions. In the second phase (start: 01/2020), the measurement methods were validated qualitatively and quantitatively. The possibility of improving the component RS condition was demonstrated by varying the forming parameters. Here, compressive RS could be induced in the component surface by changing the shoulder opening angle and the lubricant. Regarding the investigations on effects of the introduced RS condition, a test setup for cyclic mechanical loading of the components was developed. The results showed differences in the fatigue behavior between components with RS and annealed components, which are due to superimposed influences of RS and work hardening. For robust process design, the influences of process-side disturbance variables on the resulting component properties were investigated. The focus of the third phase is on the optimization and tolerancing of the forming process as well as the use of the findings and the cause-effect relationships of RS development and stability for the process design for the targeted adjustment of the component service life. To this end, the stability of the RS introduced by the forming process is investigated under specified operating boundary conditions. For the design, layout and optimization of the forming process, RS-relevant mechanisms of action and causal relationships are to be identified on demonstrator components, and generally applicable strategies for improving properties are to be developed and transferred to the manufacturing process of a realistic component. The predictability of the component properties will be ensured by numerical prediction models to be optimized in phase 3.
DFG Programme
Priority Programmes
