Performance-Related Characterization of Forming-Induced Initial Damage in 16MnCrS5 Steel under a Torsional Forward-Reverse Loading Path at LCF Regime

Abstract

Forming technology and in particular cold forward rod extrusion is one of the key manufacturing technologies with regard to the production of shafts. The selection of process parameters determines the global and local material properties. This particularly implies forming-induced initial damage in representation of pores. On this background, this study aims on describing the influence of these pores in the performance of the material 16MnCrS5 (DIN 1.7139, AISI/SAE 5115) under a torsional load path in the low cycle fatigue regime, which is highly relevant for shafts under operation conditions. For this purpose, the method of cyclic forward-reverse torsional testing was applied. Additionally, intermittent testing method and the characterization of the state of crack growth using selective electron microscopy analysis of the surface were combined. A first attempt was made to describe the influence of forming-induced initial damage on the fatigue performance and the crack growth mechanisms. The correlation of fatigue performance and initial damage was contiguous in the sense that the initial damage corresponds with a decrease of material performance. It was concluded that the focus of further investigations must be on small crack growth and the related material changes to identify the role of initial damage under cyclic loads.

Separation of Damage Mechanisms in Full Forward Rod Extruded Case-Hardening Steel 16MnCrS5 Using 3D Image Segmentation

“…Fractographic investigations and previous studies [ 12 , 22 , 23 , 30 ] have shown that MnS inclusions also play a significant role in pore formation during the full forward rod extrusion process and in fatigue with respect to crack initiation and crack propagation. For this reason, a 3D CAD MnS model was generated from the segmented 510 Inlens images ( Figure 14 b).…”

“… Diagram of fatigue specimen geometry and removal area from the component formed via full forward rod extrusion (all dimensions in mm) based on Möhring [ 22 ]. …”

“…Teschke et al performed fatigue tests in the range of 10 to 10 6 cycles on hot-rolled sheets [ 21 ]. Moehring and Walther [ 22 ] investigated the influence of forming-induced ductile damage in the LCF range under torsional loading. The influence on forming-induced ductile damage in the LCF range under axial loading was investigated by Langenfeld et al [ 12 ], who showed a significant impact of forming-induced damage on the fatigue performance.…”

FEM Simulation of the Riveting Process and Structural Analysis of Low-Carbon Steel Tubular Rivets Fracture

“…In tensile-compression cracking, the loads generated during forming of low-carbon steel in the longitudinal direction (rivets forming process) promote the nucleation of cracks along grain boundaries of ferrite, which in this case are initiated by the net of tertiary cementite at grain boundaries [ 32 , 33 , 34 ]. Nucleation cracks at Fe 3 C III have been shown to play a decisive role here.…”

Characterization and Separation of Damage Mechanisms of Extruded Case-Hardening Steel AISI 5115 under Cyclic Axial-Torsional Loading

“…Furthermore, the temperature effect on cubic body centered cell structures in terms of fatigue properties were also investigated [9]. Moehring et al [10] investigated the effect of forming-induced damage on LCF during torsional loading. The effect of forming-induced damage during cold extrusion regarding the axial-torsional LCF behavior has not yet been discussed.…”