Prediction of damage in cold bulk forming processes

Zapara, Maksim; Augenstein, E.; Helm, Dirk

doi:10.1002/pamm.201410492

Cited by 12 publications

(6 citation statements)

References 9 publications

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“…This also applies to the types of initial damage. As published by Rice et al, the stress-assisted plastic deformation promotes the nucleation and growth of micro-voids ( [33], Figures 7,8 and 10), whereby the shown central role of the non-metallic MnS-inclusions (Table 2 and Figures 7 and 10) is also indicated by Zapara/Augenstein/Helm [34]. The MnS-inclusions are known to induce anisotropic material behavior [35] including the behavior under cyclic load sequences ( [36], for forged and hardened medium carbon steel [37]).…”

Section: Discussionmentioning

confidence: 54%

Load Direction-Dependent Influence of Forming-Induced Initial Damage on the Fatigue Performance of 16MnCrS5 Steel

Moehring

Walther

2020

Materials

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Forming processes influence the mechanical properties of manufactured workpieces in general and by means of forming-induced initial damage in particular. The effect of the latter on performance capability is the underlying research aspect for the investigations conducted. In order to address this aspect, fatigue tests under compressive, tensile and compressive-tensile loads were set-up with discrete block-by-block increased amplitudes and constant amplitudes, and performed up to fracture or distinct lifetimes. Aiming at the correlation of the macroscale mechanical testing results at the mesoscale, intensive metallographic investigations of cross-sections using the microscopical methods of secondary electron analysis, energy dispersive spectroscopy and electron backscatter diffraction were performed. Thereby, the correlation of forming-induced initial damage and fatigue performance was determined, the relevance of compressive loads for the cyclic damage evolution was shown, and material anisotropy under compressive loads was indicated. Finally, the need was addressed to perform further investigations regarding crack propagations and crack arrest investigations in order to clarify the mechanism by which initial damage affects cyclic damage evolution. The relevance of the principal stress axis relative to the extrusion direction was emphasized and used as the basis of an argument for investigations under load paths with different stress directions.

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Section: Discussionmentioning

confidence: 54%

Load Direction-Dependent Influence of Forming-Induced Initial Damage on the Fatigue Performance of 16MnCrS5 Steel

Moehring

Walther

2020

Materials

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“…Forming-induced ductile damage occurs in the form of pores in the matrix material or at non-metallic inclusions, leading to local stress increases [ 11 , 12 ]. The resulting material or component failure under service conditions can be attributed to inhomogeneities [ 13 ], which have been addressed by various authors in their studies on the correlation between fatigue performance and defects, as the defects are determined by the threshold condition for small crack nuclei at the defect tip [ 14 , 15 ]. In addition, a correlation has been shown between the torsional fatigue limit and the threshold for non-propagating branched cracks.…”

Section: Introductionmentioning

confidence: 99%

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

Lingnau,

Heermant,

Otto

et al. 2024

Materials

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In general, formed components are lightweight as well as highly economic and resource efficient. However, forming-induced ductile damage, which particularly affects the formation and growth of pores, has not been considered in the design of components so far. Therefore, an evaluation of forming-induced ductile damage would enable an improved design and take better advantage of the lightweight nature as it affects the static and dynamic mechanical material properties. To quantify the amount, morphology and distribution of the pores, advanced scanning electron microscopy (SEM) methods such as scanning transmission electron microscopy (STEM) and electron channeling contrast imaging (ECCI) were used. Image segmentation using a deep learning algorithm was applied to reproducibly separate the pores from inclusions such as manganese sulfide inclusions. This was achieved via layer-by-layer ablation of the case-hardened steel 16MnCrS5 (DIN 1.7139, AISI/SAE 5115) with a focused ion beam (FIB). The resulting images were reconstructed in a 3D model to gain a mechanism-based understanding beyond the previous 2D investigations.

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“…Hardness changes due to strain hardening, induced residual stresses due to inhomogeneities of the elastic and resilient properties of material matrix, different phases as well as non-metallic inclusions and general microstructural changes with respect to grain orientation and size changes have been investigated [1]. Furthermore, additional forming-induced damage should be considered, which is characterized as pore formation at non-metallic inclusions or different microstructural stress increases under applied forming load, which locally lead to stress increases [2]. In this context, Meya et al [3] found that radially superimposed stresses during forming reduced the number of voids, which had a positive effect on performance in terms of energy absorption during notched bar impact tests.…”

Section: Introductionmentioning

confidence: 99%

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

Lingnau,

Walther

2023

MSF

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Due to the emerging relevance of topics such as climate change or scarcity of resources, the requirements for energy efficiency, emissions and resource conservation are increasing. In this context, components manufactured by metal forming offer a high potential for lightweight construction, cost effectiveness and resource efficiency. The defects resulting from forming processes e.g. in form of micropores and their growth are currently not taken into account. A commercial design is usually based on mechanical material properties and additional safety factors. The knowledge of the ductile forming-induced damage in the component design enables an improved design. In this study, the influence of different forming process parameters during full forward rod extrusion on the structural damage and the fatigue properties were investigated for the case-hardened steel AISI 5115 (16MnCrS5, 1.7131). The intention was to compare the fatigue properties of different damage states under cyclic axial and axial-torsional loading including the identification and separation of underlying damage mechanisms. A significant effect of superimposed cyclic torsional loading on cyclic axial properties and mechanisms was found, which was associated with a decrease of 38 % in the lifetime. Axial-torsional fatigue tests were conducted at various test temperatures to determine the effect of forming-induced damage and test temperature on the fatigue strength. In addition, differences in microstructure as a result of forming-induced and fatigue-induced damages were validated by using scanning electron microscopy.

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Prediction of damage in cold bulk forming processes

Cited by 12 publications

References 9 publications

Load Direction-Dependent Influence of Forming-Induced Initial Damage on the Fatigue Performance of 16MnCrS5 Steel

Load Direction-Dependent Influence of Forming-Induced Initial Damage on the Fatigue Performance of 16MnCrS5 Steel

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

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

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