Supplementary Simulations Research Articles

Effect of laser texturing and thermomechanical joining parameters on bond strength of steel-flax fiber reinforced vitrimer composites

The study examines laser texturing's impact on metal-composite hybrid joint mechanics formed via heat compression. It focuses on sustainable composite fabrication, utilizing flax fibers and a recyclable vitrimer resin known for dynamic covalent bond exchange capabilities, enhancing recyclability, repairability, and reshaping. Simulated heating conditions determined optimal bonding between the composite and laser-textured surfaces, considering the glass transition temperature for minimum temperature and time requirements. Deviations from initial heat pressing conditions (135 °C, 0.6 MPa, 5 min) reduced bonding strength, underscoring parameter sensitivity. Cross-tensional tests under varied laser texturing conditions, supported by microscopic examinations, revealed optimal strength (1680 N) with a 150 μm hatch distance and 9 repetitions, ensuring consistent ablation volume and time. Supplementary ANSYS simulations pinpointed stress concentration regions in cross-tensional joints, guiding adjustments in laser texturing within the region of interest to assess mechanical properties. The hybrid cross-tensional and lap shear joints were also reconnected after each fracture via heat compression, allowing for the evaluation of degradation in bonding strength over each cycle.

Analysis of Single-Event Upsets and Transients in 22 nm Fully Depleted Silicon-On-Insulator Logic

In this work, single-event upset (SEU) and single-event transient (SET) responses of digital logic in a planar 22nm fully-depleted conventional-well silicon-on-insulator (FD-SOI) technology under various test conditions are presented. The D-flip-flop (DFF) shift registers used for the single-event upset experiments are more sensitive to upsets when data is dynamically loaded in during irradiation rather than statically stored beforehand, but the clock rate used to load the data does not affect the upset cross sections in any significant way. The digital pattern loaded also affects the upset cross sections, but which cross section is greater between patterns of all “1s” and all “0s” is observed to be opposite for dynamic and static tests. A key capability of the technology studied in this work is the ability to apply biases to the back gates of transistors to alter threshold voltage. For conventional-well designs, as in this work, reverse body bias can be applied, increasing the threshold voltage and decreasing leakage current. Analyzing the effects of applying a back-gate bias on single-event upset cross section reveals no clear trend for single-event upset cross sections in the D-flip-flop shift registers but applying back-gate bias decreased the single-event transient cross sections measured from an inverter chain by as much as an order of magnitude. Supplementary SPICE-level simulations suggest that the drastic decrease in single-event transient cross section results from attenuation in the inverter chain. The presented experimental and simulation results indicate relatively small single-event cross sections compared to other technologies reported in literature.

On the identification of material hardening for anisotropic sheets via bulge tests

The hydraulic bulge test provides a useful tool to characterize the mechanical behavior of sheet metal under nearly equibiaxial loading, such as the material hardening response. However, the kinematic relationships during bulge tests of anisotropic sheets are still less understood and need further clarification. To this end, extensive numerical simulations of bulge tests are first performed, covering different die geometries and materials that exhibit distinct hardening features and Hill48 anisotropy. Based on the general scaling laws of the kinematic relationships, the numerical results are then used to establish an analytical model that explicitly relates the dome height, apex strain, and radii of curvatures in terms of the die ratio, material hardening parameter, and anisotropy. In addition, the general extraction procedure, which incorporates the analytical model to obtain the hardening responses of anisotropic sheets, is also provided. Finally, the effectiveness of the analytical model is confirmed based on representative results of AA6061 and DP600 sheet experiments and supplementary numerical simulations. The proposed model is expected to help facilitate the application of bulge tests in characterizing the plasticity and forming behavior of anisotropic sheet materials.

Engineering the beat phenomenon of quasi-Rayleigh waves for regions with minimal Surface Acoustic Wave (SAW) amplitude

Surface Acoustic Waves (SAW) are prevalent in a variety of scientific fields. Typically, the ability to manipulate these surface waves has a significant impact on the efficacy of any SAW-based device. In this paper, we present a simple method for designing localized regions that have minimal SAW amplitude. These localized regions have valley-like drops in SAW amplitude and are achieved by using the spatial beat phenomenon of quasi-Rayleigh waves. Controlling the beat phenomenon allows us to manipulate where and how these localized regions appear in the waveguide. In particular, the localized regions can be designed to have variable widths and can be positioned consecutively due to minimal wave scattering. The design methodology and physics are described in detail, and several supplementary simulations are provided to demonstrate the efficacy of the proposed method. Lastly, we briefly discuss how the proposed approach could potentially be exploited to implement a localized high-pass filter and enables SAW wave propagation that avoids surface obstacles.

Mechanism for anisotropic ejection of atoms from fcc (100) metal surface by low-energy argon ion bombardment: Molecular dynamics simulation

In order to thoroughly clarify the formation mechanism of “Wehner spots” during the low-energy sputtering of fcc (100) surface, molecular dynamics (MD) method was employed to investigate the sputtering of Cu (100) surface by 500 eV argon ion bombardment. Simulation program monitored the emission trajectories and velocities of sputtered atoms as well as the forces acting on them. Simulation results revealed that the preferential ejection of sputtered atoms along close-packed directions, which caused the formation of “Wehner spots”, resulted mainly from the regular interaction between sputtered atoms and their neighbor atoms. The formation mechanism of “Wehner spots” is that sputtered atom is first horizontally focused and then undergoes a ski-jump takeoff along close-packed direction. The generality of this mechanism was further verified by supplementary molecular dynamics simulations. Furthermore, this investigation demonstrated that local environment surrounding sputtered atom rather than simple collision processes transferring initial recoil energy to sputtered atom dominated the anisotropic sputtering of fcc (100) surface in low energy regime.

Transition of wake flows past two circular or square cylinders in tandem

This paper presents the dependence of flow transitions and flow regimes on Reynolds number Re (≤ 105) and scaled cylinder center-to-center spacing S* (≤ 10) for two tandem cylinders. Both circular and square cross-sectional geometries are considered, and a comparison of results is made between the two geometries. To do so, data available from the literature are collected, and supplementary numerical simulations are done to complement the literature data so as to provide clear-cut flow maps in the Re–S* domain. We identified the borders of Re- and S*-dependent flows, including steady, unsteady, transition, slender/extended body, alternating reattachment, bistable, and co-shedding flows. The flow interference between two tandem cylinders with S* < S*cr is susceptible to stabilize the flow that requires a higher Re for the onset of vortex shedding than the isolated cylinder counterpart, where S*cr is the critical spacing for the onset of co-shedding flow. Besides, the flow interference generally postpones and advances the onset of secondary vortex shedding associated with the transition from two- to three-dimensional vortex shedding for S* < S*cr and S* > S*cr, respectively. Two flow maps are made for the two geometries, both yielding fundamental contributions toward a better understanding of the flow interference effect on various flow transitions. The flow maps determine the regions of a dearth of knowledge, which future studies may pay attention to. Finally, the drag inversion, hysteresis, and flow patterns in the proximity of the onset of vortex shedding for tandem square cylinders (1.5 ≤ S* ≤ 7) are discussed.

Network-Aware Coordination of Residential Distributed Energy Resources

Rooftop solar and batteries, along with other distributed energy resources (DERs), add a new demand-side flexibility, which, when harnessed, will enable distribution operators to more efficiently manage their constrained networks. This paper presents network-aware coordination (NAC), an approach for coordinating DER within unbalanced distribution network constraints, which utilizes the alternating direction method of multipliers (ADMMs) to solve a distributed receding-horizon OPF. As far as we are aware, this paper is the first to report on the practical implementation and performance of an ADMM-based technique solving a significant network problem in live operations. We present real-world trial results of NAC coordinating 31 residential batteries on a constrained feeder within Tasmania’s 11-kV distribution network. The batteries are coordinated to manage the network’s constraints during periods of high feeder demand, decreasing the need for expensive conventional network management, in this case a diesel generator. We achieve a 34% reduction in diesel over seven peaks with 31 batteries capable of meeting 10% of peak demand. Supplementary simulations indicate the potential for a 74% diesel reduction if battery numbers were increased to 100. We find that compared to uncoordinated battery response, the NAC achieves 13% lower total costs over the trial period.

Development of a simulation model for the automatic optimization of tools for multi‐dimensional tube forming

AbstractThe increasing number of vehicle components and the advancing lightweight construction in manufacturing processes increasingly require a more flexible design of the exhaust tube geometry. The use of process supplementary simulations is necessary, in order to meet these increasing requirements in the future.The aim of this study is the development of a software tool for the simulation of multi‐dimensional tube forming processes by tube bending and tube embossing. Therefore, a graphical user interface was developed to build‐up and simulate the tube forming processes. The required material parameters for the numerical modeling were determined by means of tensile tests. The simulation models were successfully validated by comparing the numerical results with the experimental results. The influence of the workpiece and the forming tools were numerically investigated on the basis of the validated simulation models. Batch‐related tolerances could be identified as a serious source of deviations. Furthermore, experimental forming errors could be numerically reproduced and corrected by modifying the parameter settings. The tool variation increased the process knowledge and provided the basis for a subsequent optimization. The embossing structure could be optimized satisfactorily by specifying user‐defined requirements.

Modeling and Dynamic Performance Analysis of Brushless Doubly Fed Induction Machine Considering Iron Loss

Brushless doubly fed induction machine (BDFIM) which is able to operate in both induction mode and synchronous mode, has received increasing attention of researchers, in the last three decades. It could be considered as an emerging competitor for older structures, due to the substantial features such as brushless structure and requiring a fractionally rated frequency converter. The iron loss which constitutes a significant portion of total power losses is higher in BDFIM in contrast with standard induction machine. Even though it is essential to consider the iron loss effect on dynamic behavior of BDFIM, there is still no comprehensive study in the literature. The aim of this paper is to propose a dynamic model of BFIM in general reference frame in which the iron loss is taken into account. This model which is credible for all BDFIM operation modes including synchronous one, facilitates the performance analysis of BDFIM and implementation of the various control techniques. The supplementary simulations and experiments confirm that the proposed model is an appropriate candidate for BDFIM drives. Because of the complex structure of BDFIM, determination of the iron loss isn't straightforward. In this paper, a practical approach is introduced to calculate the iron loss of BDFIM in terms of frequency variations. The experimental data derived from a D132s prototype BDFIM is then compared with the calculated data from the finite element analysis (FEA).

Reduced respiratory motion artefact in constant TR multi-slice MRI of the mouse

PurposeMulti-slice scanning in the abdomen and thorax of small animals is compromised by the effects of respiration unless imaging and respiration are synchronised. To avoid the signal modulations that result from respiration motion and a variable TR, blocks of fully relaxed slices are typically acquired during inter-breath periods, at the cost of scan efficiency. This paper reports a conceptually simple yet effective prospective gating acquisition mode for multi-slice scanning in free breathing small animals at any fixed TR of choice with reduced sensitivity to respiratory motion. MethodsMulti-slice scan modes have been implemented in which each slice has its own specific projection or phase encode loop index counter. When a breath is registered RF pulses continue to be applied but data are not acquired, and the corresponding counters remain fixed so that the data are acquired one TR later, providing it coincides with an inter-breath period. The approach is refined to reacquire the slice data that are acquired immediately before each breath is detected. Only the data with reduced motion artefact are used in image reconstruction. The efficacy of the method is demonstrated in the RARE scan mode which is well known to be particularly useful for tumour visualization. ResultsValidation in mice with RARE demonstrates improved stability with respect to ungated scanning where signal averaging is often used to reduce artefacts. SNR enhancement maps demonstrate the improved efficiency of the proposed method that is equivalent to at least a 2.5 fold reduction in scan time with respect to ungated signal averaging. A steady-state magnetisation transfer contrast prepared gradient echo implementation is observed to highlight tumour structure. Supplementary simulations demonstrate that only small variations in respiration rate are required to enable efficient sampling with the proposed method. ConclusionsThe proposed prospective gating acquisition scheme enables efficient multi-slice scanning in small animals at the optimum TR with reduced sensitivity to respiratory motion. The method is compatible with a wide range of complementary methods including non-Cartesian scan modes, partially parallel imaging, and compressed sensing. In particular, the proposed scheme reduces the need for continual close monitoring to effect operator intervention in response to respiratory rate changes, which is both difficult to maintain and precludes high throughput.

Combined wave-current induced excess pore-pressure in a sandy seabed: Flume observations and comparisons with theoretical models

Waves are coexisting with currents in coastal zones; nevertheless, previous experimental studies for excess pore-pressure responses in a porous seabed were predominantly limited to the wave-only condition. In this study, the combined wave-current induced excess pore-pressures in a sandy seabed were experimentally simulated with a specially-designed flume, which can concurrently generate periodic waves and a following/opposing co-directional current. The effect of a current on the wave profile is firstly examined. The wave steepness is decreased by a following current, but enhanced by an opposing current. Flume observations indicate that, under combined wave-current loading, the wave-induced pore-pressure is increased for the following-current case, but reduced for the opposing-current case. Such wave-current combination effect becomes more significant for shorter wave periods. The variation trend of the excess pore-pressure distribution in the present flume observations is consistent with that of the existing analytical solutions. Nevertheless, due to the existence of wave and/or current boundary layer and non-lineartiy of wave-current interactions as indicated by the flume observations, certain deviations exist between the flume results for excess pore-pressure and the analytical solutions, which can not be ignored especially for the opposing-current case. The effects of the boundary layer on the combined wave-current induced pore-pressures in the seabed are further highlighted by supplementary numerical simulations. A favorable prediction by the analytical solution would be expected for following-current cases and smaller pore-pressure amplitudes would be obtained for opposing-current cases.

Stability of matter-wave solitons in a density-dependent gauge theory

We consider the linear stability of chiral matter-wave solitons described by a density-dependent gauge theory. By studying the associated Bogoliubov-de Gennes equations both numerically and analytically, we find that the stability problem effectively reduces to that of the standard Gross-Pitaevskii equation, proving that the solitons are stable to linear perturbations. In addition, we formulate the stability problem in the framework of the Vakhitov-Kolokolov criterion and provide supplementary numerical simulations which illustrate the absence of instabilities when the soliton is initially perturbed.

Separation delay through contoured transverse grooves on a 2D boat-tailed bluff body: Effects on drag reduction and wake flow features

Abstract The effectiveness of properly contoured transverse grooves in delaying the flow separation occurring on a two-dimensional boat-tailed bluff body is assessed through numerical simulations. The body has a cross-section with a 3:1 elliptical forebody and a rectangular main part followed by a circular-arc boat tail. Three-dimensional Variational Multiscale Large Eddy Simulations are carried out at R e = D u ∞ ∕ ν = 9 . 6 × 1 0 4 , using a mixed finite-volume/finite-element method. The introduction of one contoured groove on each of the boat-tail lateral surfaces produces a significant delay of flow separation and a consequent increase of the base pressure, with a global drag reduction of the order of 9 . 7 % . The wake dynamical structure remains qualitatively similar to the one typical of blunt-based two-dimensional bodies, with quantitative variations that are consistent with the reduction in wake width caused by boat tailing and by the grooves. The introduction of the grooves leads also to a regularization of the vortex shedding downstream of the body, which is more correlated in the spanwise direction. Finally, a few supplementary simulations show that the effect of the grooves is also robust to the variation of the geometrical parameters defining their location and shape.

Influence of Thermal History on the Hot Ductility of a Continuously Cast Low Alloyed Cr-Mo Steel

The hot ductility of a low alloyed Cr-Mo steel has been investigated to evaluate the surface cracking sensitivity within the straightening or unbending regime during the continuous casting process. Tensile samples were subjected to various thermal treatments, including melting and solidification, and were tested at deforming temperatures ranging between 600 and 1100 °C using a strain rate of 10−3 s−1. Hot ductility was evaluated based on reduction in area measurement and metallographic investigations. The investigated steel exhibits a drop in ductility at around 800 °C due to intergranular cracking. Microstructural examinations and supplementary thermokinetic computer simulations were carried out to describe the evolution of the microstructure during solidification and cooling.

Separation control and drag reduction for boat-tailed axisymmetric bodies through contoured transverse grooves

We describe the results of a numerical and experimental investigation aimed at assessing the performance of a control method to delay boundary layer separation consisting of the introduction on the surface of contoured transverse grooves, i.e. of small cavities with an appropriate shape orientated transverse to the incoming flow. The shape of the grooves and their depth – which must be significantly smaller than the thickness of the incoming boundary layer – are chosen so that the flow recirculations present within the grooves are steady and stable. This passive control strategy is applied to an axisymmetric bluff body with various rear boat tails, which are characterized by different degrees of flow separation. Variational multiscale large eddy simulations and wind tunnel tests are carried out. The Reynolds number, for both experiments and simulations, is $Re=u_{\infty }D/\unicode[STIX]{x1D708}=9.6\times 10^{4}$; due to the different incoming flow turbulence level, the boundary layer conditions before the boat tails are fully developed turbulent in the experiments and transitional in the simulations. In all cases, the introduction of one single axisymmetric groove in the lateral surface of the boat tails produces significant delay of the boundary layer separation, with consequent reduction of the pressure drag. Nonetheless, the wake dynamical structure remains qualitatively similar to the one typical of a blunt-based axisymmetric body, with quantitative variations that are consistent with the reduction in wake width caused by boat tailing and by the grooves. A few supplementary simulations show that the effect of the grooves is also robust to the variation of the geometrical parameters defining their shape. All the obtained data support the interpretation that the relaxation of the no-slip boundary condition for the flow surrounding the recirculation regions, with an appreciable velocity along their borders, is the physical mechanism responsible for the effectiveness of the present separation-control method.

Equivalent Circuit Modeling for Reflectarrays Using Floquet Modal Expansion

The starting point in the design of reflectarray antennas is the derivation of the so-called S-curve, which maps changes in unit cell design parameters to the phase of the scattered field from the cell. In general, full-wave simulations are used to derive this curve, though recently a number of analytical techniques have emerged based on equivalent circuit models (ECMs). However, most ECMs are cumbersome to employ, either because they are too specialized or they depend on extraction of component values from supplementary simulations. This paper presents a fully analytical method for predicting the S-curve from dipole-like reflectarray elements based on an ECM derived from a Floquet modal expansion of a planar dipole. The model does not need supplementary simulations that can be used to predict the co-polarized reflection coefficient from a variety of fixed and reconfigurable reflectarray elements. The model is validated against full-wave simulations for several reflectarray element types, including fixed patches, varactor-loaded patches, and patches on tunable substrates, and is shown to be accurate. As such, it could become a highly useful design tool for quickly deriving the S-curve of reflectarray elements during the initial design stages of reflectarrays.

Influence of Thermal History on the Hot Ductility of Ti-Nb Microalloyed Steels

The hot ductility of Ti-Nb microalloyed steel has been investigated to evaluate the sensitivity to surface crack formation during the continuous casting process. Tensile samples were subjected to different thermal treatments and were tested at deformation temperatures ranging from 650°C to 1000°C using a strain rate of 10-3s-1. It has been found, that the investigated steel evinced poor ductility over almost the whole testing temperature range characterized by marked grain boundary cracking, irrespective of which thermal cycle has been utilized or whether the samples have been melted or only reheated. Microstructural examinations and supplementary thermo-kinetic computer simulations revealed distinct Ti-Nb precipitation throughout the microstructure being responsible for the deteriorated materials hot ductility.

Quantifying the grain boundary resistance against slip transfer by experimental combination of geometric and stress approach using stage-I-fatigue cracks

In recent studies, many groups have investigated the interaction of dislocations and grain boundaries by bi-crystals and micro-specimen experiments. Partially, these experiments were combined with supplementary simulations by discrete dislocation dynamics, but quantitative data for the grain boundary resistance against slip transfer is still missing. In this feasibility study with first results, we use stage-I-fatigue cracks as highly localised sources for dislocations with well-known Burgers vectors to study the interaction between dislocations in the plastic zone in front of the crack tip and selected grain boundaries. The stress concentration at the grain boundary is calculated with the dislocation-free zone model of fracture using the dislocation density distribution in the plastic zone from slip trace height profile measurements by atomic force microscopy. The grain boundary resistance values calculated from common geometric models are compared to the local stress distribution at the grain boundaries. Hence, it is possible to quantify the grain boundary resistance and to combine geometric and stress approach for grain boundary resistance against slip transfer to a self-contained concept. As a result, the prediction of the grain boundary resistance effect based on a critical stress concept is possible with knowledge of the geometric parameters of the grain boundary only, namely the orientations of both participating grains and the orientation of the grain boundary plane.

Methane Oxidation over Palladium: On the Mechanism in Fuel-Rich Mixtures at High Temperatures

A kinetic modeling study on methane oxidation over reduced Pd for various fuel-rich conditions around the stoichiometric point of the partial oxidation at high temperatures (900–1100 K) is presented. A thermodynamically consistent detailed surface reaction mechanism is developed within the mean field approximation. The proposed kinetic model consists of 54 elementary-step based reactions including seven gas-phase species and 15 surface intermediates. Three different methane activation paths are implemented, comprising pyrolytic C–H bond dissociation steps, oxygen-assisted and dual-oxygen-assisted CH4 activation. In situ experimental measurements in a quasi-autothermally operated flow reactor, using the capillary sampling technique, are performed for model evaluation. The provided experimental data includes spatially resolved temperature and concentration profiles within a single catalytic channel of a Pd/Al2O3-coated monolith. Supplementary numerical simulations based on literature data for fuel-lean and fuel-rich conditions at high temperatures extend the model’s capability to predict a wide range of different experimental conditions.

CFD modeling the hydrodynamics of binary particle mixture in pseudo-2D bubbling fluidized bed: Effect of model parameters

The hydrodynamics of binary coal-sand mixture in a pseudo-2D rectangular bubbling fluidized bed (0.385m×0.005m×0.128m) was simulated using the multi-fluid Eulerian model incorporating the kinetic theory of granular flow. Parametric studies of the boundary wall condition, particle-particle restitution coefficient, friction packing limit, as well as transport equation for granular temperature were performed to investigate their influences on the predicted mixing/segregation behavior. The CFD simulation results demonstrated that the predicted mixing behavior was closely related to the expression for granular temperature transport equation and specularity coefficient. When the full transport equation for granular temperature was adopted, the predicted mixing degree decreased with the increase of specularity coefficient. And the best agreement between simulation results and experimental data was achieved when specularity coefficient was equal to 1.0. Nevertheless, when the algebraic transport equation for granular temperature was adopted, the system was always predicted in well-mixing rather than segregation state. Under the full transport equation for granular temperature and the no slip boundary wall condition, the predicted mixing degree decreased with the increase of the particle-particle restitution coefficient and frictional packing limit. The supplementary simulations indicated that for the considered gas-solid system there exist a critical bed thickness larger than which the system was in well-mixing state and the simulation results were independent from the investigated parameters. The hydrodynamic analysis indicated that the reduction of bubble size and the solid axial movement could be the mechanism responsible for the occurrence of axial segregation.