Thermo-micro-mechanical simulation of bulk metal forming processes

The newly proposed microstructural constitutive model for polycrystal viscoplasticity in cold and warm regimes (Motaman and Prahl, 2019), is implemented as a microstructural solver via user-defined material subroutine in a finite element (FE) software. Addition of the microstructural solver to the default thermal and mechanical solvers of a standard FE package enabled coupled thermo-micro-mechanical or thermal-microstructural-mechanical (TMM) simulation of cold and warm bulk metal forming processes. The microstructural solver, which incrementally calculates the evolution of microstructural state variables (MSVs) and their correlation to the thermal and mechanical variables, is implemented based on the constitutive theory of isotropic hypoelasto-viscoplastic (HEVP) finite (large) strain/deformation. The numerical integration and algorithmic procedure of the FE implementation are explained in detail. Then, the viability of this approach is shown for (TMM-) FE simulation of an industrial multistep warm forging

The anisotropic grain size effect on the mechanical response of polycrystals: The role of columnar grain morphology in additively manufactured metals

Additively manufactured (AM) metals exhibit highly complex microstructures, particularly with respect to grain morphology which typically features heterogeneous grain size distribution, anomalous and anisotropic grain shapes, and the so-called columnar grains. In general, the conventional morphological descriptors are not suitable to represent complex and anisotropic grain morphology of AM microstructures. The principal aspect of microstructural grain morphology is the state of grain boundary spacing or grain size whose effect on the mechanical response is known to be crucial. In this paper, we formally introduce the notions of axial grain size and grain size anisotropy as robust morphological descriptors which can concisely represent highly complex grain morphologies. We instantiated a discrete sample of polycrystalline aggregate as a representative volume element (RVE) which has random crystallographic orientation and misorientation distributions. However, the instantiated RVE incorporates the typical morphological features of AM microstructures including distinctive grain size heterogeneity and anisotropic grain size owing to its pronounced columnar grain morphology. We ensured that any anisotropy arising in the macroscopic mechanical response of the instantiated sample is mainly associated with its underlying anisotropic grain size. The RVE was then used for meso-scale full-field crystal plasticity simulations corresponding to uniaxial tensile deformation along different axes via a spectral solver and a physics-based crystal plasticity constitutive model. Through the numerical analyses, we were able to isolate the contribution of anisotropic grain size to the anisotropy in the mechanical response of polycrystalline aggregates, particularly those with the characteristic complex grain morphology of AM metals. Such a contribution can be described by an inverse square relation

Numerical and Experimental Investigations of the Effect of Melt Delivery Nozzle Design on the Open- to Closed-Wake Transition in Closed-Coupled Gas Atomization

The single-phase gas-flow behavior of a closed-coupled gas atomization was investigated with four different melt nozzle tip designs with two types of gas die. Particular attention was paid to the open- to closed-wake transition. Experimental Schlieren imaging and numerical modeling techniques were employed, with good agreement between the two being found in relation to the wake closure pressure. It was found that the melt nozzle tip design had a significant impact on the WCP, as did the type of die used, with a convergent–divergent gas die giving significantly high WCPs

Data for: Thermo-micro-mechanical simulation of bulk metal forming processes

#TMM-FE-SimulationThis repository is created for sharing Abaqus material subroutines and finite element (FE) models for thermo-micro-mechanical (TMM) FE simulation of metal forming processes

Data for: Thermo-micro-mechanical simulation of bulk metal forming processes

#TMM-FE-SimulationThis repository is created for sharing Abaqus material subroutines and finite element (FE) models for thermo-micro-mechanical (TMM) FE simulation of metal forming processes.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Metallic Materials (Microstructure, Microscopy, Modelling)

V2, Ü

The effect of melt nozzle geometry of close-coupled gas atomization

In this paper we report a numerical modelling study to understand the effect of different internal geometry profiles of four melt delivery nozzles on the gas flow pattern around a melt nozzle tip and atomisation performance during close-coupled gas atomization. The computational modelling of single phase (gas-only) flow at gas atomization pressures of 1, 2, 3, 4 and 5MPa(145, 290, 435.1, 580.1 and 725.1psi) were considered. We found that the geometry of the melt delivery nozzle can have a significant influence on gas flow, recirculation zone and atomisation behaviour. In particular, a nozzle with a hemispherical tip profile appeared to behave quite differently to those with some degree of internal taper