Design and Analysis of Fault-Tolerant 1:2 Demultiplexer Using Quantum-Dot Cellular Automata Nano-Technology

Quantum-dot Cellular Automata (QCA) is an innovative paradigm bringing hopeful applications in the perceptually novel computing layout in quantum electronics. The circuits manufactured by QCA technology can provide a notable decrease in size, rapid-switching velocity, and ultra-low power utilization. The demultiplexer is a beneficial component to optimize the whole process in any logical design, and therefore is very important in QCA. Moreover, fault-tolerant circuits can improve the reliability of digital circuits by redundancy. Hence, the present investigation illustrates a novel QCA-based fault-tolerant 1:2 demultiplexer construct that employs a two-input AND gate and inverter. The functionality of the suggested layout was executed and evaluated with the utilization of the QCADesigner 2.0.3 simulator. This paper utilizes cell redundancy on the wire, inverter, and AND gates for designing a fault-tolerant demultiplexer. Four components (i.e., missing cells, dislocation cells, extra cells, and misalignment) were analyzed by the QCADesigner simulator. The simulation results demonstrated that our proposed QCA-based fault-tolerant 1:2 demultiplexer acted more efficiently than prior constructs regarding delay and fault tolerance. The proposed fault-tolerant 1:2 demultiplexer could attain high fault-tolerance when single missing cell or extra cell faults exist in the QCA layout.

Mesoscale Mechanisms in Viscoplastic Deformation of Metals and Their Applications to Constitutive Models

Deformation of metals has attracted great interest for a long time. However, the constitutive models for viscoplastic deformation at high strain rates are still under intensive development, and more physical mechanisms are expected to be involved. In this work, we employ the newly-proposed methodology of mesoscience to identify the mechanisms governing the mesoscale complexity of collective dislocations, and then apply them to improving constitutive models. Through analyzing the competing effects of various processes on the mesoscale behavior, we have recognized two competing mechanisms governing the mesoscale complex behavior of dislocations, i.e., maximization of the rate of plastic work, and minimization of the elastic energy. Relevant understandings have also been discussed. Extremal expressions have been proposed for these two mesoscale mechanisms, respectively, and a stability condition for mesoscale structures has been established through a recently-proposed mathematical technique, considering the compromise between the two competing mechanisms. Such a stability condition, as an additional constraint, has been employed subsequently to close a two-phase model mimicking the practical dislocation cells, and thus to take into account the heterogeneous distributions of dislocations. This scheme has been exemplified in three increasingly complicated constitutive models, and improves the agreements of their results with experimental ones.

A Novel Multiaxial Strain-Based Criterion Considering Additional Cyclic Hardening

The present paper is dedicated to the theoretical evaluation of a loading feature, that may have a significant influence on fatigue phenomenon: non-proportionality. As a matter of fact, considerable interactions between dislocations, leading to the formation of dislocation cells, cause additional cyclic hardening of material. Such a phenomenon is experimentally observed for materials sensitive to non-proportionality. In such a context, the present paper is aimed to propose a novel multiaxial strain-based criterion, the refined equivalent deformation (RED) criterion, which allows to take into account, in fatigue life estimation, both strain amplitude and additional cyclic hardening. The accuracy of the novel criterion is evaluated by considering experimental tests, performed on Ti-6Al-4V specimens, subjected to multiaxial LCF loading.

Large strain hardening of magnesium containing in situ nanoparticles

In this work, in situ magnesium-based composite composed of nanoscale magnesium oxide (MgO), prepared by spark plasma sintering, shows significant plasticity and high strain hardening. During the strain-hardening stage, the incremental work-hardening exponent shows drastic fluctuations due to the pile-up and release of dislocations. The dislocation pile-up at the interface makes it possible to form dislocation cells. Mixed dislocations can be generated within the cells surrounding the MgO particles, which can interact with the stress field and effectively hinder the movement of dislocations, leading to an increase in dislocation density. What is more, grain boundaries have higher elastic modulus and hardness, which may lead to the appearance of microcracks and eventually intergranular fractures. Our results may shed some light on understanding the role of MgO particles in influencing the mechanical properties of Mg alloys and Mg-based composites, especially in work hardening.

Grain Refinement Assisted by Deformation Enhanced Precipitates through Thermomechanical Treatment of AA7055 Al Alloy

Fine-grained sheets of AA7055 Al alloy were produced by an improved double-stage rolling thermomechanical treatment (DRTMT) assisted by deformation-enhanced precipitates (DEPs). The DRTMT composed of a low temperature pre-deformation, an intermediate annealing, and a final hot rolling exhibited significantly superior tensile ductility to the conventional rolling thermomechanical treated alloy (CRTMT). Numerous fine spherical DEPs appeared after the pre-deformation. Those DEPs could exert a strong drag force on the migration of boundaries and dislocations. Dislocation cells were formed due to the drag force and dynamic recovery. These dislocation cells become polygon sub-grains by static recovery during the subsequent intermediate annealing. After the final hot deformation, with further deformation and rising temperature, low angle grain boundaries gradually stabilized and transferred to high angle grain boundaries. Due to the transformation, fine equiaxed grains were formed after DRTMT. The DRTMT alloys display superior elongation to the CRTMT alloy while maintaining high strength for grain refinement. Thus, DRTMT would be a good alternative to manufacture different heat-treatable Al alloys with fine grains efficiently.

Dislocation damage and adiabatic shear mechanisms of 7055 aluminum alloy during cutting process

This paper is intended to examine the dislocation and adiabatic shear mechanisms of 7055 aluminum alloy during cutting process with different cutting speeds. The result indicates that, at low cutting speeds, isometric dislocation cells appear, the dislocation cells are interconnected into dislocation cell blocks, and the dislocation movement is controlled by thermal activation; at high cutting speeds, dislocations mostly come in the form of elongated or not fully closed dislocation cells, and the dislocation movement is controlled by phonon drag; the width of an adiabatic shear band increases with the cutting speed, and low cutting speeds are more likely to result in microcracks. The precipitation-free zones on the grain boundary display a discontinuity under all cutting speeds; distribution and grain size of the precipitates also vary significantly.

Effect of Surface Nanocrystallization on Corrosion Resistance of the Conformed Cu-0.4%Mg Alloy in NaCl Solution

Surface nano-crystallization (SNC) of a conform-extruded Cu-0.4 wt.% Mg alloy was successfully conducted by high-speed rotating wire-brushing to obtain the deformed zone with dislocation cells and nanocrystallines. SNC promotes the anodic dissolution and corrosion rate of the Cu-Mg alloy in the initial stage of immersion corrosion in 0.1 M NaCl solution. The weakened corrosion resistance is mainly attributed to the higher corrosion activity of SNC-treated alloy. With extending the immersion time, the SNC-treated alloy slows the corrosion rate dramatically and exhibits uniform dissolution of the surface. The formation of the dense corrosion products leads to the improvement of overall corrosion performance. It indicates that the SNC-treated Cu-Mg alloy can function reliably for a longer duration in a corrosive environment.

Fully Coupled Two-Phase Composite Model for Microstructure Evolution during Non-Proportional Severe Plastic Deformation

A fully coupled micro-macro interaction model is proposed for the grain refinement caused by severe plastic deformation of cell-forming metallic materials. The model is a generalization of a previously proposed two-phase composite model suggested for the evolution of dislocation populations corresponding to the interior of the dislocation cells and dislocation cell walls. Just as within the original framework, the evolution of the material microstructure depends on the applied hydrostatic pressure, strain rate, and the loading path. Backstresses are used to define a measure of the strain path change. Thereby, the model can describe the experimentally observed dissolution of dislocation cells and the reduction of dislocation densities occurring shortly after load path changes. The large strain kinematics is accounted for in a geometrically exact manner using the nested split of the deformation gradient tensor, proposed by Lion. Within the extended model, the macroscopic strength of the material depends on the microstructural parameters. In that sense, the new model is fully coupled. It is thermodynamically consistent, objective, and w-invariant under isochoric changes of the reference configuration. A physical interpretation is provided for the nested multiplicative split in terms of the two-phase microstructure composite model.

Hot Deformation Behavior of AA-FGH720Li Superalloy

The hot deformation behavior of FGH720Li superalloy was investigated by hot compressive tests on Gleeble-1500D thermal simulation test machine in different temperatures and strain rates. The true stress-strain curves were obtained, and based on the deformation data, the constitutive equation of FGH720Li superalloy was built. The Deformation Active Energy of FGH720Li was determined to be Q=787.6KJ/mol. The main deformation modes were dislocation glide and twinning. At the beginning of the deformation, a large number of dislocations generated, glided and scrambled in the alloy, then entwisted to form dislocation cells, which were the recrystallization nucleus. At the later period of the deformation, the dislocation would rotate to easy glide direction through twinning, inducing that the deformation of the alloy ensued. At the same time, the deformation had significant effect on grain refinement and the crushed of the primary particle boundary.