29 research outputs found
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
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