Deformation behavior and constitutive model for dual-phase Mg-Li alloy at elevated temperatures

In order to study the deformation behavior and evaluate the workability of the dual-phase Mg-9Li-3Al-2Sr alloy, isothermal hot compression tests were conducted using the Gleeble-3500 thermal-mechanical simulator, in ranges of elevated temperatures （423-573 K） and strain rates （0.001-1 s^-1）. Plastic instability is evident during the deformation which is in the form of serrated flow; serrated yielding is attributed to the locking of mobile dislocations by the Mg and Li atoms which diffuse during the deformation. The relationships between flow stress, strain rate and deformation temperature were analyzed and the deformation activation energy and some basic material factors at different strains were calculated using the Arrhenius equation. The effects of temperature and strain rate on deformation behavior were represented using the Zener–Hollomon parameter in an exponent-type equation. To verify the validity of the constitutive model, the predicted values and experimental flow curves under different deformation conditions were compared, the correlation coefficient （0.9970） and average absolute relative error （AARE=4.41%） were calculated. The results indicate that the constitutive model can be used to accurately predict the flow behavior of dual-phase Mg-9Li-3Al-2Sr alloy during high temperature deformation.

Vehicle Dynamic State Estimation： State of the Art Schemes and Perspectives

Next-generation vehicle control and future autonomous driving require further advances in vehicle dynamic state estimation. This article provides a concise review, along with the perspectives, of the recent developments in the estimation of vehicle dynamic states. The definitions used in vehicle dynamic state estimation are first introduced, and alternative estimation structures are presented. Then, the sensor configuration schemes used to estimate vehicle velocity, sideslip angle, yaw rate and roll angle are presented. The vehicle models used for vehicle dynamic state estimation are further summarized, and representative estimation approaches are discussed. Future concerns and perspectives for vehicle dynamic state estimation are also discussed.

Thrust characteristics of nano-carbon/Al/oxygenated salt nanothermites for micro-energetic applications

Combustion within small motors is key in the application-specific development of nanothermite-based micro-energetic systems. This study evaluates the performance of nanothermite mixtures in a converging-diverging nozzle and an open tube. Mixtures were prepared using nano-aluminum(n-Al),potassium perchlorate(KClO_(4)), and different carbon nanomaterials(CNMs) including graphene-oxide(GO), reduced GO, carbon nanotubes(CNTs) and nanofibers(CNFs). The mixtures were packed at different densities and ignited by laser beam. Performance was measured using thrust measurement,high-speed imaging, and computational fluid dynamics modeling, respectively. Thrust, specific impulse(ISP), volumetric impulse(ISV), as well as normalized energy were found to increase notably with CNM content. Two distinctive reaction regimes(fast and slow) were observed in combustion of low and high packing densities(20% and 55%TMD), respectively. Total impulse(IFT) and ISPwere maximized in the 5%GO/Al/KClO_4 mixture, producing 7.95 m N·s and 135.20 s respectively at 20%TMD, an improvement of 57%compared to a GO-free sample(5.05 m N·s and 85.88 s). CFD analysis of the motors over predicts the thrust generated but trends in nozzle layout and packing density agree with those observed experimentally;peak force was maximized by reducing packing density and using an open tube. The numerical force profiles fit better for the nozzle cases than the open tube scenarios due to the rapid nature of combustion. This study reveals the potential of GO in improving oxygenated salt-based nanothermites,and further demonstrates their applicability for micro-propulsion and micro-energetic applications.

Analysis of the hot deformation of ZK60 magnesium alloy

Hot deformation of cast-homogenized and extruded(in both the extrusion and transverse directions)ZK60 magnesium alloy was conducted using the Gleeble®3500 thermal-mechanical simulation testing system.A new approach to model the high temperature constitutive behavior of the alloy was done using two well-known equations(i.e.hyperbolic sine and Ludwig equations).For this approach,the deformation conditions were divided into regimes of low and high temperature and strain rate(four regimes).Constitutive model development was conducted in each regime and the material parameters(P)were evaluated as strain,strain rate and temperature-dependent variables;P(ε,ε,T).Using this approach,the flow curves were predicted with high accuracy relative to the experimental measurements.Moreover,detailed information on the evolution of hot deformation activation energy was obtained using the modified hyperbolic sine model.Using the modified Ludwig equation,details of strain hardening and strain rate sensitivity of the ZK60 material during hot deformation were obtained.

FISS GAN:A Generative Adversarial Network for Foggy Image Semantic Segmentation

Because pixel values of foggy images are irregularly higher than those of images captured in normal weather(clear images),it is difficult to extract and express their texture.No method has previously been developed to directly explore the relationship between foggy images and semantic segmentation images.We investigated this relationship and propose a generative adversarial network(GAN)for foggy image semantic segmentation(FISS GAN),which contains two parts:an edge GAN and a semantic segmentation GAN.The edge GAN is designed to generate edge information from foggy images to provide auxiliary information to the semantic segmentation GAN.The semantic segmentation GAN is designed to extract and express the texture of foggy images and generate semantic segmentation images.Experiments on foggy cityscapes datasets and foggy driving datasets indicated that FISS GAN achieved state-of-the-art performance.

Role of heat balance on the microstructure evolution of cold spray coated AZ31B with AA7075

A promising solid-state coating mechanism based on the cold spray technique provides highly advantageous conditions on thermal-sensitive magnesium alloys.To study the effect of heat balance in cold spray coating on microstructure,experiments were designed to successfully coat AA7075 on AZ31B with two different heat balance conditions to yield a coated sample with tensile residual stress and a sample with compressive residual stress in both coating and substrate.The effects of coating temperature on the microstructure of magnesium alloy and the interfaces of coated samples were then analyzed by SEM,EBSD,TEM in high-and low-heat input coating conditions.The interface of the AA7075 coating and magnesium alloy substrate under both conditions consists of a narrow-band layer with very fine grains,followed by columnar grains of magnesium that have grown perpendicular to the interface.At higher temperatures,this layer became wider.No intermetallic phase was detected at the interface under either condition.It is shown that the microstructure of the substrate was affected by coating temperature,leading to stress relief,dynamic recrystallization and even dynamic grain growth of magnesium under high temperature.Reducing the heat input and increasing the heat transfer decreased microstructural changes in the substrate.

Parallel Distance: A New Paradigm of Measurement for Parallel Driving

In this paper, a new paradigm named parallel distance is presented to measure the data information in parallel driving system. As an example, the core variables in the parallel driving system are measured and evaluated in the parallel distance framework. First, the parallel driving 3.0 system included control and management platform, intelligent vehicle platform and remote-control platform is introduced. Then,Markov chain(MC) is utilized to model the transition probability matrix of control commands in these systems. Furthermore, to distinguish the control variables in artificial and physical driving conditions, different distance calculation methods are enumerated to specify the differences between the virtual and real signals. By doing this, the real system can be guided and the virtual system can be im-proved. Finally, simulation results exhibit the merits and multiple applications of the proposed parallel distance framework.

A Novel Indirect Parabolic Solar Cooker

The continuous increase in global demand and cost of electricity are some of the reasons that solar cooking has received much attention recently. Another factor which has also contributed to the acceptance of solar cookers is global campaigns against actions that contribute to climate change. Various types of solar cookers are currently in existence, these are box, panel and parabolic cookers. Some solar cookers only function when the cooking section is placed under direct sunshine, while others have been modified to cook without directly exposing their cooking section to the sun. Most solar cookers face similar challenges, and these include, exposure of users to sun, inability to function at night or when there is no sunshine, low utilization efficiency and technical complexities. This report presents an indirect parabolic cooker that eliminates the identified solar cooker challenges. The cooker uses a parabolic reflector to focus the sun rays to a frustum shaped receiver that was placed at its focus. The cooker has an insulated cooking/heat storage tank which was separated from the dish and cavity receiver system. The heat transfer fluid was distributed through the system with the aid of high temperature flexible hoses. Several cooking tests including water boiling and pancake baking were done, an extensive analysis of cooking based on the international testing procedures for solar cookers was also carried out. This solar cooker had a utilization efficiency of 39%, an overall calculated exergy efficiency of 0.05% and an average characteristic boiling time of approximately 13 minutes/kg. The manufactured solar cooker in this study was used for family cooking.

Effect of erosion on corrosion of API X120 steel in relation to erodent particle size

The nature of the solid erodent particles present in corrosive petroleum fluid can cause transporting pipeline to experience severe erosion and corrosion damages. The effect of erosion on corrosion behavior of API X120 steel was investigated using aluminum oxide and silicon carbide particles with different sizes as erodent and 3.5wt.% NaCl aqueous solution saturated with carbon dioxide as a corrosive medium. The effect of the erodent particle size on the corrosion behavior of the steel material at different particle speeds and impact angles was investigated using weight loss, potentiodynamic polarization and surface analysis techniques. The erosion results confirmed that the material damage increased with increasing particle speed. It was observed that in carbon dioxide-saturated saline solution, deposition of protective iron carbonate film occurred on the steel surface. It was found that the corrosion film can provide better protection at lower particle speed than at higher speed. The ratio of total erosion-corrosion (S)/effect of erosion on corrosion (T) analysis confirmed that at higher S/T ratio, the particle speed and material removal rate are low and vice versa at lower S/T ratio. Lower S/T values for the combined erosion and corrosion tests performed with erodent silicon carbide particle compared to erodent aluminum oxide particle showed that erosion enhancement of corrosion is more evident in the test performed using aluminum oxide particle than using silicon carbide particle. The result also suggests that when subjected to larger size erodent particle, the damage to pipeline due to effect of erosion on corrosion process can be more significant compared to smaller size erodent particle.

Additively manufactured metallic biomaterials

Metal additive manufacturing(AM)has led to an evolution in the design and fabrication of hard tissue substitutes,enabling personalized implants to address each patient’s specific needs.In addition,internal pore architectures integrated within additively manufactured scaffolds,have provided an opportunity to further develop and engineer functional implants for better tissue integration,and long-term durability.In this review,the latest advances in different aspects of the design and manufacturing of additively manufactured metallic biomaterials are highlighted.After introducing metal AM processes,biocompatible metals adapted for integration with AM machines are presented.Then,we elaborate on the tools and approaches undertaken for the design of porous scaffold with engineered internal architecture including,topology optimization techniques,as well as unit cell patterns based on lattice networks,and triply periodic minimal surface.Here,the new possibilities brought by the functionally gradient porous structures to meet the conflicting scaffold design requirements are thoroughly discussed.Subsequently,the design constraints and physical characteristics of the additively manufactured constructs are reviewed in terms of input parameters such as design features and AM processing parameters.We assess the proposed applications of additively manufactured implants for regeneration of different tissue types and the efforts made towards their clinical translation.Finally,we conclude the review with the emerging directions and perspectives for further development of AM in the medical industry.

Correction to: Effect of erosion on corrosion of API X120 steel in relation to erodent particle size

The article Effect of erosion on corrosion of API X120 steel in relation to erodent particle size written by Paul C.Okonkwo et al.was originally published electronically on the publisher s internet portal(currently SpringerLink)on 27 December 2019 with open access.With the author(s)'decision to step back from Open Choice,the copyright of the article changed in April 2020 to@China Iron and Steel Research Institute Group 2020,and the article is forthwith distributed under the terms of copyright.