金属材料塑性本构模型建立研究进展

本构模型反映了流变应力与应变、变形温度和应变速率的对应关系,在设备选型、有限元仿真计算等方面具有重要应用。综述了几种主要的本构模型建立方法,即经验型本构模型、物理型本构模型以及近年来被广泛使用的机器学习型本构模型。经验型本构模型的建立过程简便,但其无法从微观层面解释材料变形的机理。相比之下,物理型本构模型的建立虽然复杂,但由于其包含了微观机制信息,预测精度优于经验型本构模型。机器学习型本构模型相较于前两种建模方法预测精度更高,建模方式更加简便。运用VOSviewer和CiteSpace文献计量软件对金属材料本构模型建模方法进行统计分析,得出相关领域国家、机构研究现况以及之间合作关系,分析表明中国对于金属材料本构模型领域研究最为活跃,采用机器学习进行本构建模的研究是近年来热点。并且随着人工智能技术的飞速发展,运用机器学习建立本构模型将是未来发展方向。

双极膜水解离现象——双极膜的物理构型、离子传递及其水解离压降分析

从阴阳膜层内基本离子即盐正负离子和水离子 (H+,OH-)的传递过程着手 ,建立了几种常见物理构型的双极膜理论电压降模型 ,并对模型进行分析 ,提出了降低双极膜水解离电压的有效途径 .特别是对两性氢氧化物、高分子弱酸碱的水解离催化作用进行了理论解释 ,提出了催化作用是基于“自由溶液中水解离速率常数值增大”的观点 ,并提出了双极膜水解离催化剂的筛选依据 .

FeCrNi合金静动态物理本构模型研究

以金属材料塑性变形的位错动力学为基础,将FeCrNi合金的流动应力分解为非热应力和热激活应力两部分.通过对该合金屈服应力随温度变化特性、屈服应力的应变速率特性、孪晶组织的温度特性及位错组态的应变速率特性进行分析,认为非热应力不只是应变的函数,还与温度和应变速率相关,因此对Johnson-Cook模型方程形式进行修正以描述非热应力.同时认为影响热激活应力的微结构参数主要为位错阻碍间距△l,定义并推导出表征△l演化的g函数的表达式,将其引入Kocks的热激活方程,从而建立FeCrNi合金的物理型本构模型.该模型初步实现了对FeCrNi合金从室温到高温、从准静态到动态塑性变形行为的描述.

论民用飞机构型审核要求和程序

为研究民用飞机构型审核要求和程序,从分析当前国内外航空领域构型审核活动的现状和应用入手,结合当前相关国际标准和我国民用飞机构型管理工作的发展现状,本文阐述了在民用飞机设计研发过程中进行构型审核的目的和必要性,分析了民用飞机构型审核应涵盖的内容以及审核的工作程序,探讨了构型审核在我国民机领域的应用和发展前景。

浅谈民用飞机机载系统构型审核

当前民用飞机研发主要采用主制造商-供应商模式,机载系统通过工作包形式分发给供应商,项目的构型管理带来了巨大挑战,构型审核作为重要技术管理工具,在机载系统的研制中起到了重要作用,本文介绍了构型审核的形式和内容,对机载系统的构型审核提出了建议。

民机试飞过程中构型审核初步研究

结合相关标准和前期飞机构型审核活动的实践,从构型审核活动的目的和必要性出发,阐述了试飞过程中开展构型审核的形式、内容以及相关典型流程,其中包含了审查方介入部分。为后续试飞活动的开展提供了有益的支持。

一种气动式发射装置的设计与分析

面对小型无人机快速部署和发射的实际需求,综合考虑现有各种发射形式和使用工况,以调压阀和作动阀为核心,构建了动力源压强恒定的气动模块,提升了发射稳定性。同时针对气动发射的特点,以R-K气体状态方程为基础,对发射过程进行了物理模型简化和数学方程建模,提高了理论模型的准确度,并以此为基础得到了发射速度和发射时间与气体压强、加速距离等相关参数的函数关系,为整套系统的多领域扩展和详细参数设计提供了基础。

Large-scale complex physical modeling and precisionanalysis

Large-scale 3D physical models of complex structures can be used to simulate hydrocarbon exploration areas. The high-fidelity simulation of actual structures poses challenges to model building and quality control. Such models can be used to collect wideazimuth, multi-azimuth, and full-azimuth seismic data that can be used to verify various 3D processing and interpretation methods. Faced with nonideal imaging problems owing to the extensive complex surface conditions and subsurface structures in the oil-rich foreland basins of western China, we designed and built the KS physical model based on the complex subsurface structure. This is the largest and most complex 3D physical model built to date. The physical modeling technology advancements mainly involve 1） the model design method, 2） the model casting flow, and 3） data acquisition. A 3D velocity model of the physical model was obtained for the first time, and the model building precision was quantitatively analyzed. The absolute error was less than 3 mm, which satisfies the experimental requirements. The 3D velocity model obtained from 3D measurements of the model layers is the basis for testing various imaging methods. Furthermore, the model is considered a standard in seismic physical modeling technology.

Gray correction method of X-ray fusion image

The conventional X-ray gray weighted image fusion method based on variable energy cannot characterize the phys- ical properties of complicated objects correctly, therefore, the gray correction method of X-ray fusion image based on neural network is proposed. The conventional method acquires 12 bit images on variable energy, and then fuses the images in a tra- ditional way. While the new method takes the fusion image as the input of neural network simulation system and takes the acquired 16 bit image as the output of neural network. The X-ray image physical characteristic model based on neural net- work is obtained through training. And then it takes steel ladder block as the test object to verify the feasibility of the mod- el. In the end, the gray curve of output image is compared with the gray curve of 16 bit real image. The experiment results show that this method can fit the nonlinear relationship between the fusion image and the real image, and also can expand the scope of application of low dynamic image acquisition equipment.

CFD Simulation of Film Flow and Gas/Liquid Countercurrent Flow on Structured Packing

A mathematic model of two-phase flow and a physical model of two-dimensional (2D) vertical section for the plate-type structured packing Mellapak 250.Y were set up and verified. The models were used to study the influence of packing’s surface microstructure on the continuity of liquid film and the amount of liquid holdup. Simulation results show that the round corner shape and micro wavy structure are favorable in remaining the continuity of liquid film and increasing the amount of liquid holdup. The appropriate liquid flow rate was determined by investigating different liquid loadings to obtain an unbroken liquid film on the packing surface. The pressure difference between inlet and outlet for gas phase allowed gas and liquid to flow countercurrently in a 2D computational domain. The direction change of gas flow occurred near the phase interface area.

Classification of VxOy^q Clusters by △=2y＋q-5x

Vanadium oxide clusters VxOy^q（x≤8, q=0, ±1） are classified according to the oxidation index （△=2y＋q-5x） of each cluster. Density functional calculations indicate that clusters with the same oxidation index tend to have similar bonding characters, electronic structures, and reactivities. This general rule leads to the findings of new possible ground state struc- tures for V206 and V3O6＋ clusters. This successful application of the classification method on vanadium oxide clusters proves that this method is very effective in studying the bonding properties of early transition metal oxide clusters.

TENSILE TEST AND PHYSICAL MODEL OF NiTi SHAPE MEMORY ALLOY

The tensile stress-strain curves of NiTi wires are obtained by tensile experiments under different heat treatments. A phenomenological physical model based on hysteresis element method is developed to describe the experimentally determined stress-strain curves of shape memory alloy (SMA) wires. Numerical simulations are made. Simulation results show that：(1) a series of unusual changes on physical and mechanical properties of SMA wires occur when martensitic, especially R (rhombohedral) phase transformation emerge. The stress-strain relation of SMA wires is highly non-linear; (2) there are no notable yielding phenomena before NiTi wires are broken; (3) numerical results obtained by the physical model are in good agreement with experimental data.

Impacts of Secondary Aerosols on a Persistent Fog Event in Northern China

The chemistry version of the Weather Re- search and Forecasting model （WRF/Chem） was coupled with the anthropogenic emission inventory of David Streets to investigate the impacts of secondary aerosols on a persistent fog event from 25 to 26 October 2007, in Northem China. The spatial distribution of the simulated fog is consistent with satellite observations, and the time-height distributions of the simulated boundary layer where the fog formed are also in good agreement with these observations. The sensitivity studies show that the secondary aerosols of SO4, NO3, and NH4 formed from gaseous precursors of SO2, NOx, and NH3 had substantial impacts on the formation processes and microphysical structure of the fog event. The decrease of the secondary aerosols obviously reduced the liquid water path and column droplet number concentration of the fog below the 1-km layer, and the corresponding area-averaged liquid water path and droplet number concentration of the fog decreased by 43% and 79%, respectively. The concentra- tions of NOx and NO3 were found to be extremely high in this case. The concentration of interstitial aerosol NO3 was much higher than the SO4 and NH4, but the concentration of SO4 was highest in the cloud-borne aerosols. The average activation ratios for SO4, NO3, and NH4 were 34%, 31%, and 30%, respectively, and the maximum ra- tios reached 62%, 86%, and 55% during the fog episode.

Band Structure： A Solid-State Physics Model with Cosmological Implications

This work is aimed at showing that the ＂band structure＂ of the energy distribution in solids which is a well-known model for electronic engineers and solid-state physics scientists is an efficacious description also for phenomena not tied to energy neither related to microcosm. In particular, it is displayed that how the elements of the consolidated physical theories, arranged together using the ＂band structure＂, lead to a model for the distribution of speed in the universe that is essentially analogous to the distribution of energy in solids. The description is accompanied by references to the experimental data that sustain it, together with an overview of the possible development opportunities.

Service-Oriented Network Virtualization Architecture for Internet of Things

As a key technology to realize smart services of Internet of Things（IoT）, network virtualization technology can support the network diversification and ubiquity, and improve the utilization rate of network resources. This paper studies the service-ori- ented network virtualization architecture for loT services. Firstly the semantic description method for loT services is proposed, then the resource representation model and resource management model in the environment of network virtualization are presented. Based on the above models, the service-oriented virtual network architecture for loT is established. Finally, a smart campus system is designed and deployed based on the service-oriented virtual network architecture. Moreover, the proposed architecture and models are verified in experiments.

Experimental study on large wood filtration performance by herringbone water-sediment separation structure

A herringbone water-sediment separation structure(hereinafter referred to as "herringbone structure") has been shown to be effective in separating coarse inorganic debris; however, less is known regarding the large wood(LW) filtration effect in this structure. This paper presents preliminary research on the wood filtration effect of the herringbone structure based on physical model tests.The results show that the herringbone structure exhibited effective performance in large wood size segregation, with a 100% component filtration rate for LW that diameter(D) larger than ribbed beam opening width(a). The total filtration rate also exceeded 80% when the Fraud number(Fr) is larger than 2.64 and increased with the increase of Fr. After exceeding Frmax, total filtration rate would be decreased due to overflow. Beside flow condition,structure parameters influence significantly on LW filtration rate. We attempt to explain the filtration process via particle contact trajectory and particle movement trajectory. The inclined angle of ribbed beam(γ) contributed the most variation to the filtration rate via influencing the coincidence with particle contact trajectory and particle movement trajectory. The high sensitivity coefficient of ribbed beam(θ) under relatively low Fr conditions implies remarkable influences on LW filtration effects by causing clogging problem. The ribbed beam opening width(a) together with LW diameter(D) influenced the size segregation performance.

Redundant Hydraulic Secondary Flight Control Systems Behavior in Failure Conditions

The flight control systems, designed in order to assure the necessary safety level even in failure conditions, are generally characterized by a proper redundant layout. The redundancies must be designed in order to assure an adequate system behavior when some failures are present; in fact an incorrect layout may cause serious shortcomings concerning the response when some component is not operational. Therefore the usual correct design activities request the complete analysis of the system behavior in failure condition. The work analyses the response of a redundant secondary flight control hydraulic servo-mechanism equipped with some proper equalization devices, when some of the most probable and representative failures are present. It must be noted that the redundancy layout, designed in order to assure the necessary safety level even in failure conditions, may behave improperly during normal operations, if the system architecture is unsuitable, when manufacturing defects are present. The improper behavior, generally consisting of force fighting or speed fighting caused by different offsets or asymmetries between the two sections of the system, may be usually overcome by means of a suitable equalization device. Therefore, the system behavior during and following the failure transient greatly depends on both its redundancy architecture and related equalization device. The above mentioned problems have been studied by means of an appropriate physical-mathematical model of a typical electro-hydraulic servo-mechanism prepared to the purpose, performing a certain number of simulations of representative actuations in which different types of failures are accurately modeled. In the opinion of the authors, this paper concerns a topic quite neglected but important in the technical literature. At the best of the authors＇ knowledge, no specific scientific work in this field is available, excepting some industrial technical reports.

Coordination configurations of cupric tartrate in electronic industry wastewater

The coordination structure of cupric tartrate(Cu−TA)complex was investigated by ultraviolet−visible(UV-Vis)and liquid chromatography/mass spectrometer(LC-MS)firstly;furthermore,effective coordination configurations and electronic properties of Cu−TA in aqueous solution were systematically revealed by density functional theory(DFT)calculations.Consistently,Job plots show the possible existence of[Cu(TA)]and[Cu(TA)_(2)]^(2-)at 230 and 255 nm based on UV-Vis results.LC-MS results confirm the existence of the single and high coordination complexes[Cu_(2)(TA)_(2)]^(+),[Cu(TA)_(2)]^(+)and[Cu_(2)(TA)_(3)(H_(2)O)_(2)(OH)_(2)]^(2+).DFT calculation results show that carboxylic oxygen and hydroxyl oxygen of tartaric acid(TA)are preferred sites for Cu(Ⅱ)coordination.[Cu(TA)](1H,3H sites O of TA coordinated with Cu(Ⅱ)),[Cu(TA)_(2)]^(2-)(two 1^(C),2^(H) sites O of TA coordinated with Cu(Ⅱ)),and[Cu(TA)_(3)]^(4-)(three 2H,3H sites O of TA coordinated with Cu(Ⅱ))should be dominant coordination configurations of Cu−TA.The corresponding Gibbs reaction energies are-170.1,-136.2,and-90.2 kJ/mol,respectively.

Mobility in Driven Frenkel-Kontorova Model

The transport properties in a kind of simple system are studied within the framework of a generalized Frenkel Kontorova model where the chain is composed of two kinds of atoms. Its studied mobility includes two aspects: the velocity mobility B v and the momentum mobility B m . The effective system temperatures for the two subchains, T e 1 and T e 2 are defined, respectively. For the underdamped case, the regime of nonlinear response becomes wider and more "steps" occur when the value of m increases. For m = 1, T e 1(F) = T e 2(F) . For m >1, T e 1(F) > T e 2(F) and the difference increases with the increase of m . The momentum transportation shows very different behavior from that of the velocity transportation. Within a prescribed intermediate "steps" of B v(F) or B m(F) , both of them decrease with the increase of F and B m(F) decreases more quickly. For the case of overdamping and nonzero temperature, the hysteresis interval becomes thinner and the transitions become smoother. The increase of m makes the hysteresis thinner and the transitions smoother. When T is high, all the transitions are smeared out, and the diatomic effects become unimportant. We expect these results contribute to the understanding of the atomic processes occurring at the interface of two materials when they are brought together and moved with respect to one another.

A Space Propulsion Principle Brought about by Locally-Expanded Space

As is well known in cosmology, inflationary universe which shows rapid expansion of space is based on the phase transition of the vacuum exhibited by the Weinberg-Salam model of the electroweak interaction. The vacuum has the property of a phase transition, just like water may become ice and vice versa. This shows that a vacuum possesses a substantial physical structure. The expansion rule of the universe is governed by the Friedmann equations and the Robertson-Walker metric. We explored another possibility of a space propulsion principle where the locally rapid expanding space generates the thrust, using the cosmology. In this paper, space propulsion principle is introduced from another angle （cosmology）, that is, the pressure of the field induced by local expansion of space is completely considered in the propulsion principle.