C6 - Fatigue Behavior (funding period 2)
Fatigue behavior of sheet-bulk-metal formed workpieces
Project Status: finished
Last Update: 23.01.2017
Members
Objective of subproject C6 - "Fatigue behavior" is the analysis of fatigue mechanisms due to cyclic loads for workpieces produced by sheet-bulk metal forming (SBMF). Due to cold forming operations with high degrees of deformation and three-dimensional stress states a ductile damage occurs in the material that is characterized by the formation, growth and coalescence of voids. These cavities are possible crack initiators and determine the fatigue life of the components.
For the investigation of the fatigue behavior miniature specimens taken from SBMF components are tested under cyclic loads in the low cycle fatigue regime. Exemplary the figure shows the results of fatigue tests on samples extracted from processadapted tailored blanks (TP A1). Here, as process variants, two different forming forces have been studied and compared with the initial state of the semi-finished sheet metal product.

Figure: Results of fatigue tests on samples extracted from tailored blanks
In addition, in situ studies of miniature specimens using a tension-compression-module in a scanning electron microscope are provided. Thereby, the influence of an alternating load on the microstructure can be observed. The obtained data will be merged into a model to describe the fatigue life. Therefore, microstructural approaches for the formation of ductile damage will be combined with a continuum mechanical description of crack propagation for a fatigue life prediction. The crack propagation is examined in miniature CT-specimens (CT = compact tension) with adjusted microstructures to complement the model.

Figure: Scheme of specimen preparation (left), Micro-Tension-Compression-Module (right)
Working Groups
Publications
2016
- Besserer, H.; Dalinger, A.; Rodman, D.; Nürnberger, F.; Hildenbrand, P.; Merklein, M.; Maier, H.: Induction heat treatment of sheet-bulk metal formed parts assisted by water-air spray cooling. In: Steel Research International, 87(2016)9, pp. 1220-1227
- Besserer, H.; Hildenbrand, P.; Gerstein, G.; Rodman, D.; Nürnberger, F.; Merklein, M.; Maier, H.: Ductile Damage and Fatigue Behavior of Semi-Finished Tailored Blanks for Sheet-Bulk Metal Forming Processes. In: Journal of Materials Engineering and Performance, 25(2016)3, pp. 1136-1142
- Besserer, H.; Gerstein, G.; Dalinger, A.; Jablonik, L.; Rodman, D.; Nürnberger, F.: Ion Beam Processing in the Sample Preparation for the Analysis of Ductile Damage in Deep Drawing Steels. In: Praktische Metallographie, 53(2016)4, pp. 221-236
- Besserer, H.; Boiarkin, V.; Rodman, D.; Nürnberger, F.: Qualifying Electrically Conductive Cold Embedding-Media for Scanning Electron Microscopy. In: Metallography, Microstructure and Analysis, 5(2016)4, pp. 332-341
2015
- Gerstein, G.; Besserer, H.; Nürnberger, F.; Maier, H.: Comparison of the Mechanisms of Void Formation by Plastic Deformation in Single- and Dual-Phase BCC- Steels. In: 2015 TMS Annual Meeting & Exhibition, Proceedings Characterization of Minerals, Metals and Materials, (2015), Hoboken, New Jersey: Wiley, pp. 75-81
- Hildenbrand, P.; Sieczkarek, P.; Matthias, S.; Löffler, M.; Besserer, H.; Merklein, M.; Tekkaya, A.; Reithmeier, E.; Maier, H.: Inkrementelles Umformen dünnwandiger Funktionsbauteile unter Einsatz prozessangepasster Halbzeuge durch Verfahren der Blechmassivumformung. In: Tekkaya, A. E.; Liewald, M.; Merklein, M.; Behrens, B.-A. (Edt.): Tagungsband zum 18. Workshop Simulation in der Umformtechnik & 3. Industriekolloquium Blechmassivumformung 2015 - DFG Transregio 73, (2015), Aachen: Shaker Verlag, pp. 149-170
- Gerstein, G.; Besserer, H.; Jablonik, L.; Dalinger, A.; Nürnberger, F.; Höpner, A.: Präparation plastisch umgeformter Stahlproben durch Ionenstrahlbearbeitung für die Untersuchung von duktiler Schädigung. In: Schneider, G.; Zschech, E.; Petzow, G. (Edt.): Fortschritte in der Metallographie. Berichte der 49. Metallographie-Tagung Dresden, 16. bis 18. September 2015, 47(2015), Sankt Augustin: DGM Inventum, pp. 153-158
Presentations
2016
- 26.04.2016: Besserer, H.: Ermüdungsverhalten blechmassivumgeformter Bauteile, Werkstoff- und Leichtbau-Forum, Hannover Messe, Hannover
2015
- 27.02.2015: Hildenbrand, P.: Inkrementelles Umformen dünnwandiger Funktionsbauteile unter Einsatz prozessangepasster Halbzeuge durch Verfahren der Blechmassivumformung, 18. Workshop Simulation in der Umformtechnik & 3. Industriekolloquium Blechmassivumformung, Dortmund
- 17.03.2015: Nürnberger, F.: Comparsion of the mechanisms of void formation by plastic deformation in single- and dual-phase bcc-steels, TMS 2015, Orlando, Florida
- 17.09.2015: Gerstein, G.: Präparation plastisch umgeformter Stahlproben durch Ionenstrahlbearbeitung für die Untersuchung von duktiler Schädigung, 49. Metallographie-Tagung, Dresden