Digital twins (DT) of industrial processes have become increasingly important. They aim to digitally represent the physical world to help evaluate, optimize, and predict physical processes and behaviors. Therefore, DT is a vital tool to improve production automation through digitalization and becomes more sophisticated due to rapidly evolving simulation and modeling capabilities, integration of IoT sensors with DT, and high-capacity cloud/edge computing infrastructure. However, the fidelity and reliability of DT software are essential to represent the physical world. This paper shows an automated and systematic test architecture for DT that correlates DT states with real-time sensor data from a production line in the forging industry. Our evaluation shows that the architecture can significantly accelerate the automatic DT testing process and improve its reliability. A systematic online DT testing method can significantly detect the performance shift and continuously improve the DT's fidelity. The snapshot creation methodology and testing agent architecture can be an inspiration and can be generally applicable to other industrial processes that use DT to generalize their automated testing.

Defects during production may lead to material waste, which is a significant challenge for many companies as it reduces revenue and negatively impacts sustainability and the environment. An essential reason for material waste is a low degree of automation, especially in industries that currently have a low degree of digitalization, such as steel forging. Those industries typically rely on heavy and old machinery such as large induction ovens that are mostly controlled manually or using well-known recipes created by experts. However, standard recipes may fail when unforeseen events happen, such as an unplanned stop in production, which may lead to overheating and thus material degradation during the forging process. In this paper, we develop a digital twin-based optimization strategy for the heating process for a forging line to automate the development of an optimal control policy that adjusts the power for the heating coils in an induction oven based on temperature data observed from pyrometers. We design a digital twin-based deep reinforcement learning (DTRL) framework and train two different deep reinforcement learning (DRL) models for the heating phase using a digital twin of the forging line. The twin is based on a simulator that contains a heating transfer and movement model, which is used as an environment for the DRL training. Our evaluation shows that both models significantly reduce the temperature unevenness and can help to automate the traditional heating process.

With the recent discovery of in-plane chemically ordered MAX phases (i-MAX) of the general formula ((M2/3M1/32)-M-1)(2)AC comes addition of non-traditional MAX phase elements. In the present study, we use density functional theory calculations to investigate the electronic structure, bonding nature, and mechanical properties of the novel (W2/3Sc1/3)(2)AlC and (W2/3Y1/3)(2)AlC i-MAX phases. From analysis of the electronic structure and projected crystal orbital Hamilton populations, we show that the metallic i-MAX phases have significant hybridization between W and C, as well as Sc(Y) and C states, indicative of strong covalent bonding. Substitution of Sc for Y (M-2) leads to reduced bonding strength for W-C and Al-Al interactions while M-2-C and M-2-Al interactions are strengthened. We also compare the Voigt-Reuss-Hill bulk, shear, and Young's moduli along the series of M-1 = Cr, Mo, and W, and relate these trends to the bonding interactions. Furthermore, we find overall larger moduli for Sc-based i-MAX phases.

We have uncovered two inherently laminated transition metal carbides, (Cr2/3Sc1/3)(2)A1C and (Cr2/3Y1/3)(2)A1C, which display in-plane chemical order in the carbide sheet and a Kagome pattern in the Al layer. The phases belong to the most recently discovered family of so-called i-MAX phases. The materials were synthesized and the crystal structures were evaluated by means of analytical high resolution scanning transmission electron microscopy, selected area electron diffraction, and X-ray diffraction Rietveld refinement. An orthorhombic structure of space group Cmcm (#63) and a monoclinic structure of space group C2/c (#15) are solved. The compounds were investigated by first-principles calculations based on density functional theory, suggesting close to degenerate anti-ferro- and ferromagnetic spin states, dynamical and mechanical stability, and a Voigt bulk modulus in the range 134-152 GPa.

We have calculated electronic, vibrational, and elastic properties of (Mo2/3Sc1/3)2AlC and (Mo2/3Y1/3)2AlC, two recently discovered nanolaminated materials in the family of so-called i-MAX phases. A comparison is made to the properties of the related hypothetical MAX phases Sc2AlC, Y2AlC, and Mo2AlC. From an analysis of the electronic band structures and projected crystal orbital Hamilton populations (pCOHP), we show that the i-MAX phases have more isotropic band structures than the MAX phases, but that their bonding characteristics are very similar, despite belonging to different space groups. However, the similar bonding notwithstanding, qualitative as well as significant quantitative differences are seen in the phonon density of states (PDOS). We also compare the Voigt-Reuss-Hill (VRH) bulk, shear, and Young's moduli. For (Mo2/3Sc1/3)2AlC, BVRH = 132 GPa, GVRH = 89 GPa, and EVRH = 218 GPa, all of which are higher values than for Sc2AlC, but lower than for Mo2AlC. For (Mo2/3Y1/3)2AlC, BVRH = 117 GPa, GVRH = 85 GPa, and EVRH = 205 GPa, which are higher than for Y2AlC, but lower than for Mo2AlC.

Here, we report, for the first time, on the first‐order Raman spectra of the layered Mo‐based ternaries: MoAlB, Mo2Ga2C and Mo2GaC. Polycrystalline samples were fabricated, and well‐defined Raman spectra were recorded. When the experimental peak positions were compared with those predicted from density functional theory, good agreement was obtained, indirectly validating both. Furthermore, all modes in the three compounds were symmetry assigned. Copyright © 2017 John Wiley & Sons, Ltd.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

In this work, we employ and critically evaluate a first-principles approach based on supercell calculations for predicting the magnetic critical order-disorder temperature T-c. As a model material we use the recently discovered nanolaminate Mn2GaC. First, we derive the exchange interaction parameters J(ij) between pairs of Mn atoms on sites i and j of the bilinear Heisenberg Hamiltonian using the novel magnetic direct cluster averaging method (MDCA), and then compare the J's from the MDCA calculations to the same parameters calculated using the Connolly-Williams method. We show that the two methods yield closely matching results, but observe that the MDCA method is computationally less effective when applied to highly ordered phases such as Mn2GaC. Secondly, Monte Carlo simulations are used to derive the magnetic energy, specific heat, and T-c. For Mn2GaC, we find T-c = 660 K. The uncertainty in the calculated T-c caused by possible uncertainties in the J's is discussed and exemplified in our case by an analysis of the impact of the statistical uncertainties of the MDCA-derived J's, resulting in a T-c distribution with a standard deviation of 133 K.

We here use first-principles calculations to investigate the phase stability of the hypothetical laminated material V2Ga2C and the related alloy (Mo1−xVx)2Ga2C, the latter for a potential parent material for synthesis of (Mo1−xVx)2C, a new two-dimensional material in the family of so called MXenes.

Inherently layered magnetic materials, such as magnetic ${M}_{n+1}A{X}_{n}$ (MAX) phases, offer an intriguing perspective for use in spintronics applications and as ideal model systems for fundamental studies of complex magnetic phenomena. The MAX phase composition ${{M}_{n}}_{+1}A{X}_{n}$ consists of ${M}_{n+1}{X}_{n}$ blocks separated by atomically thin $A$-layers where $M$ is a transition metal, $A$ an A-group element, $X$ refers to carbon and/or nitrogen, and $n$ is typically 1, 2, or 3. Here, we show that the recently discovered magnetic $\mathrm{M}{\mathrm{n}}_{2}\mathrm{GaC}$ MAX phase displays structural changes linked to the magnetic anisotropy, and a rich magnetic phase diagram which can be manipulated through temperature and magnetic field. Using first-principles calculations and Monte Carlo simulations, an essentially one-dimensional (1D) interlayer plethora of two-dimensioanl (2D) Mn-C-Mn trilayers with robust intralayer ferromagnetic spin coupling was revealed. The complex transitions between them were observed to induce magnetically driven anisotropic structural changes. The magnetic behavior as well as structural changes dependent on the temperature and applied magnetic field are explained by the large number of low energy, i.e., close to degenerate, collinear and noncollinear spin configurations that become accessible to the system with a change in volume. These results indicate that the magnetic state can be directly controlled by an applied pressure or through the introduction of stress and show promise for the use of $\mathrm{M}{\mathrm{n}}_{2}\mathrm{GaC}$ MAX phases in future magnetoelectric and magnetocaloric applications.

The MAX phase family is a set of nanolaminated, hexagonal materials typically comprised of three elements: a transition metal (M), an A-group element (A), and carbon and/or nitrogen (X).In this thesis, first-principles based methods have been used to investigate the phase stability and physical properties of a number of MAX and MAX-like phases.Most theoretical work on MAX phase stability use the constraint of 0 K conditions, due to the very high computational cost of including temperature dependent effects such as lattice vibrations and electronic excitations for all relevant competing phases in the ternary or multinary chemical space.Despite this, previous predictions of the existence of new MAX phases have to a large extent been experimentally verified.In an attempt to provide a possible explanation for this consistency, and thus help strengthen the confidence in future predictions, we have calculated the temperature dependent phase stability of Tin+1AlCn, to date the most studied MAX phases.We show that both the electronic and vibrational contribution to the Gibbs free energies of the MAX phases are cancelled by the corresponding contributions to the Gibbs free energies of the competing phases.We further show that this is the case even when thermal expansion is considered.We have also investigated the stability of two hypothetical MAX-like phases, V2Ga2C and (Mo1-xVx)2Ga2C, motivated by a search for ways to attain new two-dimensional MAX phase derivatives, so-called MXenes.We predict that it is possible to synthesize both phases.For x≤0.25, stability of (Mo1-xVx)2Ga2C is indicated for both ordered and disordered solid solutions on the M sublattice.For x=0.5 and x≥0.75, stability is only indicated for disordered solutions.The ordered solutions are stable at temperatures below 1000 K, whereas stabilization of the disordered solutions requires temperatures of up to 2100 K, depending on the V concentration.Finally, we have investigated the electronic, vibrational, and magnetic properties of the recently synthesized MAX phase Mn2GaC.We show that the electronic band structure is anisotropic, and determine the bulk, shear, and Young's modulus to be 157, 93, and 233 GPa, respectively, and Poisson's ratio to be 0.25.We further predict the magnetic critical order-disorder temperature of Mn2GaC to be 660 K.We base the predictions on Monte Carlo simulations of a bilinear Heisenberg Hamiltonian constructed from magnetic exchange interaction parameters derived using two different supercell methods: the novel magnetic direct cluster averaging method (MDCA), and the Connolly-Williams method (CW).We conclude that CW is less computationally expensive than MDCA for chemically and topologically ordered phases such as Mn2GaC.

This thesis presents theoretical research on MAX phases (M=transition metal, A=A-group element, X=carbon and/or nitrogen), with focus on predictions of phase stability as well as of physical properties.The first part is an investigation of the phase stability of the MAX phases Ti 2 AlC, Ti 3 AlC 2 , and Ti 4 AlC 3 at elevated temperatures, where the former two phases have been obtained experimentally.Phase stability calculations of MAX phases usually do not take temperature dependent effects such as electronic excitations and lattice vibrations into consideration due to significantly increased computational cost.The results have nevertheless so far been quite accurate, with good agreement between theory and experiments.Still, the question whether the inclusion of temperature into the calculations could significantly alter the results as compared to previous 0 K calculations needs to be investigated, since this has bearing on the reliability of future predictions of the stability of not yet known MAX phases.However, it is shown that for Ti n+1 AlC n , the different temperature dependent effects largely cancel each other.The results therefore suggest that to go beyond 0 K calculations for phase stability predictions of MAX phases is motivated only for borderline cases.

In this paper, we report the by first-principles predicted properties of the recently discovered magnetic MAX phase Mn2GaC. The electronic band structure and vibrational dispersion relation, as well as the electronic and vibrational density of states, have been calculated. The band structure close to the Fermi level indicates anisotropy with respect to electrical conductivity, while the distribution of the electronic and vibrational states for both Mn and Ga depend on the chosen relative orientation of the Mn spins across the Ga sheets in the Mn–Ga–Mn trilayers. In addition, the elastic properties have been calculated, and from the five elastic constants, the Voigt bulk modulus is determined to be 157 GPa, the Voigt shear modulus 93 GPa, and the Young's modulus 233 GPa. Furthermore, Mn2GaC is found relatively elastically isotropic, with a compression anisotropy factor of 0.97, and shear anisotropy factors of 0.9 and 1, respectively. The Poisson's ratio is 0.25. Evaluated elastic properties are compared to theoretical and experimental results for M2AC phases where M = Ti, V, Cr, Zr, Nb, Ta, and A = Al, S, Ge, In, Sn.

Methods based on first-principles calculations have proven effective for predicting the thermodynamic stability of materials that have not previously been considered. However, the vast majority of these predictions are based on 0 K calculations, which means that little is known about the effects of temperature on their accuracy. This causes considerable uncertainty with respect to stability predictions of new hypothetical phases.In this work we combine first-principles calculations with an optimization procedure to calculate the phase stability as a function of temperature for Ti2AlC, Ti3AlC2 and Ti4AlC3 MAX phases with respect to their most competing phases in the Ti-Al-C phase diagram, in a temperature interval from 0 to 2000 K. To model nonzero temperatures, we include effects from the electronic and vibrational free energies to the Gibbs free energy for all relevant competing phases. We show that, due to a mutual cancellation of the temperature dependent energy terms, the results of neither the harmonic nor the quasiharmonic calculations differ significantly from the calculated 0 K formation energies. We thus provide a plausible explanation for the success of previous 0 K predictions, an explanation which also serves as evidence for the hypothesis that the phase stability in many materials systems is primarily governed by the 0 K energy terms. (C) 2014 Elsevier B.V. All rights reserved.

We have used first-principles calculations and Heisenberg Monte Carlo simulations to search for the magnetic ground state of Mn2GaC, a recently synthesized magnetic nanolaminate. We have, independe ...