Experimental-numerical approach to efficient TTT-generation for simulation of phase transformations in thermomechanical forming processes

Behrens, Bernd‐Arno; Chugreev, Alexander; Kock, Christoph

doi:10.1088/1757-899x/461/1/012040

Cited by 13 publications

(10 citation statements)

References 7 publications

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“…At MP2, in contrast, significantly different residual stresses of 192 MPa in the material 1.7225 and 138 MPa in the material 1.3505 were determined. The comprehensive material characterisation of the authors in [37] has shown that the plastic behaviour, the transformation-related and the transformation-plastic parameters of the two materials are different. Of particular importance is the material-specific martensitic transformation behaviour, which starts much later in 1.3505 with Ms 184°C compared to 1.7225 with Ms 334°C.…”

Section: Difficulties Related To the Analysis Of The Formation Of Resmentioning

confidence: 99%

Strategies for residual stress adjustment in bulk metal forming

et al. 2021

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The family of bulk forming technologies comprises processes characterised by a complex three-dimensional stress and strain state. Besides shape and material properties, also residual stresses are modified during a bulk metal forming process. The state of residual stresses affects important properties, like fatigue behaviour and corrosion resistance. An adjustment of the residual stresses is possible through subsequent process steps such as heat treatments or mechanical surface modification technologies, like shot peening and deep rolling. However, these additional manufacturing steps involve supplementary costs, longer manufacturing times and harmful effects on the product quality. Therefore, an optimized strategy consists in a targeted introduction of residual stresses during the forming processes. To enable this approach, a fundamental understanding of the underlying mechanisms of residual stress generation in dependence of the forming parameters is necessary. The current state of the art is reviewed in this paper. Strategies for the manipulation of the residual stresses in different bulk forming processes are classified according to the underlying principles of process modification.

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Section: Difficulties Related To the Analysis Of The Formation Of Resmentioning

confidence: 99%

Strategies for residual stress adjustment in bulk metal forming

et al. 2021

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“…The phase transformation behaviour is investigated with and without previous deformation in cooling tests on the Quench and Deformation Dilatometer DIL 805A/D + T. Figure 7b shows the transformation behaviour in a continuous cooling transformation (cct) diagram. For modelling, the cct is converted into a time temperature transformation (ttt) diagram using an experimental numerical approach [45].…”

Section: Characterisation Of the Thermo-mechanical-metallurgical Matementioning

confidence: 99%

Targeted adjustment of residual stresses in hot-formed components by means of process design based on finite element simulation

et al. 2021

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The aim of this work is to generate an advantageous compressive residual stress distribution in the surface area of hot-formed components by intelligent process control with tailored cooling. Adapted cooling is achieved by partial or temporal instationary exposure of the specimens to a water–air spray. In this way, macroscopic effects such as local plastification caused by inhomogeneous strains due to thermal and transformation-induced loads can be controlled in order to finally customise the surface-near residual stress distribution. Applications for hot-formed components often require special microstructural properties, which guarantee a certain hardness or ductility. For this reason, the scientific challenge of this work is to generate different residual stress distributions on components surfaces, while the geometric as well as microstructural properties of AISI 52100 alloy stay the same. The changes in the residual stresses should therefore not result from the mentioned changed component properties, but solely from the targeted process control. Within the scope of preliminary experimental studies, tensile residual stresses in a martensitic microstructure were determined on reference components, which had undergone a simple cooling in water (from the forming heat), or low compressive stresses in pearlitic microstructures were determined after simple cooling in atmospheric air. Numerical studies are used to design two tailored cooling strategies capable of generating compressive stresses in the same components. The developed processes with tailored cooling are experimentally realised, and their properties are compared to those of components manufactured involving simple cooling. Based on the numerical and experimental analyses, this work demonstrates that it is possible to influence and even invert the sign of the residual stresses within a component by controlling the macroscopic effects mentioned above.

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“…The previously described thermo-mechanical cylinder upsetting tests were numerically modeled with the commercial FE software Simufact.forming 14 using MSC.marc solver. A time-temperature-transformation (ttt) diagram, accounting for polymorphic behavior of the investigated steel alloy 1.3505 was implemented in the FE-software; see [43]. To simulate the viscoplastic material flow during hot forming, the flow stress of the material was implemented in the model as a function of equivalent plastic strain ε eq , equivalent plastic strain rateε eq and temperature T. To calibrate this multidimensional function, flow curves were experimentally determined as described in Section 3.…”

Section: Numerical Procedures For Macroscopic Fe Simulationmentioning

confidence: 99%

Experimental and Numerical Investigations of the Development of Residual Stresses in Thermo-Mechanically Processed Cr-Alloyed Steel 1.3505

Behrens

Schröder

Brands

et al. 2019

Metals

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Residual stresses in components are a central issue in almost every manufacturing process, as they influence the performance of the final part. Regarding hot forming processes, there is a great potential for defining a targeted residual stress state, as many adjustment parameters, such as deformation state or temperature profile, are available that influence residual stresses. To ensure appropriate numerical modeling of residual stresses in hot forming processes, comprehensive material characterization and suitable multiscale Finite Element (FE) simulations are required. In this paper, experimental and numerical investigations of thermo-mechanically processed steel alloy 1.3505 (DIN 100Cr6) are presented that serve as a basis for further optimization of numerically modeled residual stresses. For this purpose, cylindrical upsetting tests at high temperature with subsequently cooling of the parts in the media air or water are carried out. Additionally, the process is simulated on the macroscale and compared to the results based on the experimental investigations. Therefore, the experimentally processed specimens are examined regarding the resulting microstructure, distortions, and residual stresses. For the investigation on a smaller scale, a numerical model is set up based on the state-data of the macroscopic simulation and experiments, simulating the transformation of the microstructure using phase-field theory and FE analysis on micro- and meso-scopic level.

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Experimental-numerical approach to efficient TTT-generation for simulation of phase transformations in thermomechanical forming processes

Cited by 13 publications

References 7 publications

Strategies for residual stress adjustment in bulk metal forming

Strategies for residual stress adjustment in bulk metal forming

Targeted adjustment of residual stresses in hot-formed components by means of process design based on finite element simulation

Experimental and Numerical Investigations of the Development of Residual Stresses in Thermo-Mechanically Processed Cr-Alloyed Steel 1.3505

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