FATIGUE DAMAGE MODELING IN LAMINATED COMPOSITES BY USING RX-FEM AND STRENGTH TRACKING METHOD

The durability and residual load carrying capacity of composite materials and structures is of critical importance for increasing their application across the industry. Regularized eXtended Finite Element Method (Rx-FEM) framework for discrete modeling of damage evolution and interaction in laminated composite materials under fatigue loading has been extended to include residual Strength Tracking (ST) method in the Mesh Independent Crack (MIC) insertion constitutive modeling as well as in the initiation phase of the fatigue Cohesive Zone Model (CZM). The ST method was initially proposed for semi empirical analysis of IM7/8852 open-hole specimen test S-N data under spectrum loading and variable R -ratios (R = 0.1, 5, and -1). In the present work, the ST method is implemented as a component of high-fidelity progressive damage analysis framework and is combined with damage variable incremental update technique for the propagation phase within the CZM formulation. 3D validation examples investigating the solution stability under constant amplitude fatigue with respect to the cycle increment size are presented and demonstrate the solution stability within a feasible range of cycles per step.

Linear PWM Techniques of Asymmetrical Six-phase Machine With Optimal Current Ripple Performance

<p>Linear modulation techniques (LMTs) of an asymmetrical six-phase machine (ASPM) with two isolated neutral points synthesize the desired voltage vectors by applying at least five switching states. Different choices of applied voltage vectors, sequences in which they are used, distribution of dwell times among the redundant switching states give rise to a large number of possible LMTs. It is desirable that these LMTs avoid more than two transitions of a particular inverter leg within a carrier period. Only a subset of existing LMTs of ASPM follows this rule. Through an innovative approach, this paper finds a way to account for all possible infinitely many LMTs that follow the rule of at most two transitions per leg. Another important criterion for the selection of an LMT is its current-ripple performance. Therefore, through numerical optimization, the paper finds optimal LMTs among the above infinite possible LMTs for all reference voltage vectors in the linear range and for the whole feasible range of a machine parameter. This parameter is related to the leakage inductance of the machine and impacts the current ripple performance of ASPM. An optimal hybrid strategy is proposed with these optimal techniques, which outperforms all existing techniques in terms of the current ripple. The theoretical analysis is validated through simulation in Matlab and experiments performed up to 3.5 kW on a hardware prototype.</p>

Linear PWM Techniques of Asymmetrical Six-phase Machine With Optimal Current Ripple Performance

<p>Linear modulation techniques (LMTs) of an asymmetrical six-phase machine (ASPM) with two isolated neutral points synthesize the desired voltage vectors by applying at least five switching states. Different choices of applied voltage vectors, sequences in which they are used, distribution of dwell times among the redundant switching states give rise to a large number of possible LMTs. It is desirable that these LMTs avoid more than two transitions of a particular inverter leg within a carrier period. Only a subset of existing LMTs of ASPM follows this rule. Through an innovative approach, this paper finds a way to account for all possible infinitely many LMTs that follow the rule of at most two transitions per leg. Another important criterion for the selection of an LMT is its current-ripple performance. Therefore, through numerical optimization, the paper finds optimal LMTs among the above infinite possible LMTs for all reference voltage vectors in the linear range and for the whole feasible range of a machine parameter. This parameter is related to the leakage inductance of the machine and impacts the current ripple performance of ASPM. An optimal hybrid strategy is proposed with these optimal techniques, which outperforms all existing techniques in terms of the current ripple. The theoretical analysis is validated through simulation in Matlab and experiments performed up to 3.5 kW on a hardware prototype.</p>

Nowcasting transmission and suppression of the Delta variant of SARS-CoV-2 in Australia

As of July 2021, there is a continuing outbreak of the B.1.617.2 (Delta) variant of SARS-CoV-2 in Sydney, Australia. The outbreak is of major concern as the Delta variant is estimated to have twice the reproductive number of previous variants that circulated in Australia in 2020, which is worsened by low levels of acquired immunity in the population. Using a re-calibrated agent-based model, we explored a feasible range of non-pharmaceutical interventions, in terms of both mitigation (case isolation, home quarantine) and suppression (school closures, social distancing). Our nowcasting modelling indicates that the level of social distancing currently attained in Sydney is inadequate for the outbreak control. A counter-factual analysis suggests that if 80% of agents comply with social distancing, then at least a month is needed for the new daily cases to reduce from their peak to below ten. A small reduction in social distancing compliance to 70% lengthens this period to 45 days.

Physics-Based and Data-Enhanced Model for Electric Drive Sizing during System Design of Electrified Powertrains

In multi-drive electrified powertrains, the control strategy strongly influences the component load collectives. Due to this interdependency, the component sizing becomes a difficult task. This paper comprehensively analyses different electric drive system sizing methods for multi-drive systems in the literature. Based on this analysis, a new data-enhanced sizing approach is proposed. While the characteristic is depicted with a physics-based polynomial model, a data-enhanced limiting function ensures the parameter variation stays within a physically feasible range. Its beneficial value is demonstrated by applying the new model to a powertrain system optimization. The new approach enables a detailed investigation of the correlations between the characteristic of electric drive systems and the overall vehicle energy consumption for varying topologies. The application results demonstrate the accuracy and benefit of the proposed model.

Chemi-Informatic approach to investigate putative pharmacoactive agents of plant origin to eradicate COVID-19

Background:: The scientific community has supported from the medicinal flora of ancient as well as modern times in extracting chemicals, which holds therapeutic potential. In many previous studies, it was discovered Amentoflavone as an anti-viral agent and its presence as a bioactive constituent in many plants of different families Selaginellaceae, Euphorbiaceae, and Calophyllaceae etc. Withania somnifera (Ashwagandha) is already considered significant anti-viral agent in traditional medicine, and it is the main source of Somniferine-A, Withanolide-B. Objective:: In this study phytochemicals such as Withanolide-B, Somniferine-A, Stigmasterol, Amentoflavone, and Chavicine were analyzed to screen protein inhibitors out of them; such proteins are involved in SARS-Cov-2's internalization and interaction with human cytological domains. This will help in developing check point for SARS-Cov-2 internalization. Material and methods:: Chemi-informatic tools like basic local alignment search tool (BLAST), AutoDock-vina, SwissADME, MDWeb, Molsoft, ProTox-II, and LigPlot were deployed to examine the action of pharmacoactive agents against SARS-Cov-2. The many tools deployed in the study were based on finest algorithms like Artificial neural networking, Machine Learning, and Artificial intelligence. Results:: On the basis of binding energies less than equal to -8.5 kcal/mol. Amentoflavone, Stigmasterol, and Somniferine-A were found to be most effective against COVID-19 disease as these chemical agents exhibit hydrogen bond interactions and competitively inhibit major proteins (SARS-Cov-2 Spike, Human ACE-2 receptor, Human Furin protease, SARS-Cov-2 RNA binding protein) that are found to involved in its infection and pathogenesis. Simulation analysis provides more validity to the selection of drug candidate Amentoflavone. ADMET properties were found to be in feasible range for putative drug candidates. Conclusion:: Computational analysis was successfully deployed in searching pharmacoactive phytochemicals Like Amentoflavone, Somniferine-A, and Stigmasterol that can bring control over COVID-19 expansion. This new methodology was found to be efficient, as reduces monetary expenditures and time consumption, aftermath molecular wet-lab validations will provide better approval for finalizing our selected drug model for controlling COVID-19 pandemic.

Benefit and Critical Factors for the Performance of the Boundary Layer Ingesting Propulsion

The benefit of the boundary layer ingestion (BLI) is described in the perspective of the propulsion and engine development. A power saving map of the BLI engines is derived based on the correlation of the wake velocity ratio of the ingested boundary layer profile and the propulsive efficiency. The ratio of the mass flow rate between BLI and non-BLI propulsors is introduced to quantify the power saving of the BLI engine relative to a clean inlet flow engine which generates same amount of thrust. The wake recovery factor from the jet flow out of the BLI engine is employed to find an adequate sizing of the BLI engine for the given design requirement. The effects of the fan pressure ratio on the power saving are also investigated to explore the feasible range of the BLI engine design. The derived correlation is validated with CFD analyses. A numerical experiment is carried out by varying the wake velocity ratio through different BLI engines sized with respect to an influencing body. Consequently, the propulsor efficiency is quantified and presented by the saving in the actual shaft power. The efficiency penalty, pressure ratio of the BLI fan stage are correlated with the power saving and the correlation is validated through BLI2DTF and R4 fan stage CFD analyses based on rig test data.

Optimization of Materials Composition and UV-VIS Light Wavelength Towards Curing Time Performance on Development of Tissue Engineering Scaffold

VAT photopolymerization 3D printing is a process that solidified a vat of liquid photopolymer resin solution into desired products in the presence of UV light. Achieving an optimal property with shorter curing time is an ultimate goal when using functional or special resins. In this study, the effect of wavelength with different compositions of UHT resin mixed PEG solution is studied. Different sources of light were identified, which is UV-A with a wavelength of 365 nm and VIS with a wavelength greater than 420 nm. The PEGconcentrations were varied at 40%, 50%, and 60%. While UHT concentration ratio added into solution was 30%, 50%, and 70%. It has been observed that the optimum curing under UV and VIS wavelength were 9.55 minutes and 17.48 minutes respectively. The feasible range to optimize results of curing time, PEG 48%and UHT 41% with the result 8.6 minutes for the UV-A. Meanwhile, for VISwavelength, PEG 49% and UHT 64% with the result 16 minutes. The success of this study will lead to further innovation on UV-VIS light source in 3D printing in terms of energy efficiency, safety, and cost as well as further evaluation of the performance with respect to the mechanical properties of tissue engineering scaffold.

Guardian Map Approach to Feasible Range of Static Stability Margin of Hypersonic Flight Vehicles with Input Saturation

Static stability margin is a critical parameter in flight control design. The feasible range of it must cover the uncertainty through the flight. To reasonably identify the feasible range of static stability margin in advance, an approach based on guardian maps is proposed for flight control of hypersonic flight vehicles with input saturation. First, the model of hypersonic flight vehicle (HFV) is established as a parametric plant. Then, flying quality requirements for the closed-loop system are formulated as inequality constraints using guardian maps. Moreover, by using linear matrix inequality, the saturation of elevators is taken into account in the integrated control of attitude control. The prescribed minimum of static stability margin that ensures the flying quality of hypersonic flight vehicles with input saturation is obtained. Furthermore, from the prospective of integrated control, it is shown that the feasible range of static stability margin can be enlarged by changing aerodynamic characteristics. The effectiveness of the proposed approach is validated by numerical simulation.

Influence of electrode tip diameter on metallurgical and mechanical aspects of spot welded duplex stainless steel

In this article, the influence of electrode tip diameter is investigated for spot welded duplex stainless steel (DSS). Electrode tip diameter and welding current are considered as the major influencing parameters and their values are varied within the feasible range, suitable for 0.8 mm thick sheet, whereas other important parameters such as welding time and electrode force are kept constant. DSS with the chosen thickness range is now becoming a useful material in automotive body-in-white applications and in future it will become one of the key materials replacing the existing materials and hence research outcome of the present work may be beneficial from application view point. In this work, the spot welding quality is inspected through metallurgical aspects (microstructure and microhardness), physical aspects (nugget diameter and electrode indentation), mechanical performance (tensile shear strength [TSS]) and failure mode. The obtained result shows that smaller electrode tip diameter limits nugget diameter due to expulsion phenomena and increases electrode indentation due to higher current intensity. TSS decreases with increase in electrode tip diameter for the same welding current but maximum TSS obtained for particular electrode tip diameter increases with increase in electrode tip diameter up to a specific limit and then it remains constant.