异形方圆接头的钣金建模及展料实现

UG/NX2.0是一款功能强大的CAD/CAM/CAE集成软件。利用其专用的钣金模块,可以使传统的“天圆地方”钣金接头的展料工作,变得异常简单和高效。不仅降低了劳动强度,而且提高了展料准确度。该方法具有快速、准确、变参等特点。

散热器面罩边框零件的逆向设计和曲面展开

以散热器面罩边框零件的逆向设计为例,介绍设计中零件表面数据采集方法,研究了点云的数据处理、曲面划分等前处理的关键技术;提出在CATIA软件的逆向设计模块中有关特征曲线的几种创建方法,介绍曲线曲面的重构方法.以Dynaform为平台,总结出零件展料分析的一般步骤和方法,并对曲面展开的关键技术进行探讨.

CF6-80C/E航空发动机低压涡轮静子封严件工艺优化技术

介绍了航空钣金件加工工艺的优化过程。用CAD/CAM及激光切割技术,对冲压弯曲件进行精确展料,达到冲压弯曲毛料无余量定形、提高材料利用率的目的;用冲压的方法代替激光下料,研究无余量弯曲成形工艺,以取消后续余量加工工序,降低加工费用;通过对冲压工艺和钎焊工艺的技术改进,提高了一次钎焊合格率。

Optimized Allocation Model for Regional Agricultural Fertilizer Resources in Southern Xinjiang from the Perspective of Sustainable Development

[Objective] This study was to establish an optimized model for the allocation of agricultural fertilizer resources in Southern Xinjiang from the perspective of sustainable development.[Method] An optimized model for the allocation of agricultural fertilizer resources was established based on their allocation structure.Combined with the actual agricultural production in Aksu areas of Southern Xinjiang,by establishing a rational evaluation index system,under the premise of considering the planting area constraints,the total water resources constraints and the security constraints of food production,we established the empirical optimal allocation model of the regional agricultural fertilizer resources in Aksu area of Southern Xinjiang.Moreover,we solved the model by using the search algorithm of computer and lingo programming.[Result] The increased economic benefit was near to 1.8 billion Yuan by adopting the optimal allocation methods,with a relative increment of about 34.4%.[Conclusion] Our results provided theoretical basis for achieving the sustainable development of agricultural economy in Southern Xinjiang.

Biodiesel production and its development strategy

Biodiesel, an environmentally friendly biofuel with similar flow and combustion properties as petroleum-based diesel and low emission profile, which is commonly prepared from triglyceride （TG） sources such as vegetable oils, animal fats, and waste greases, holds good promises as an alternative to diesel fuel. Alternate fuels for diesel engines have become increasingly important due to diminishing petroleum reserves and awareness of the increased environmental consequences of emissions from petroleum-fuelled engines, as the world is confronted with an energy crisis. Currently, the production of methyl or ethyl esters from edible oils is much more expensive than that of diesel fuels due to the relatively high costs of vegetable oils （about four times the cost of diesel in China）. Methyl esters produced from such oils can be expected to compete economically with diesel fuels, and there is a need to explore low cost alternate feedstocks for the production of biodiesel. Rapeseed is little sensitive to crop input levels, allowing reduction of tillage, irrigation, and weed control. Significant yield increases will be attained using new hybrids and better crop management. Rapeseed cultures in seasonal set-aside lands such as Dongting Lake surroundings can significantly decreases the amount of subsides spent for agricultural overproduction in China, which leads to an increase in farmer incomes as well as the creation of new employment. This significantly lowers production costs, reduces environmental impact, and increases final energy gains. Our rapeseed oil is good source for biodiesel with respect to high oil content and proper fatty acid composition.

Flexural destructive process of unidirectional carbon/carbon composites reinforced with in situ grown carbon nanofibers

Unidirectional carbon/carbon（C/C） composites modified with in situ grown carbon nanofibers（CNFs） were prepared by catalysis chemical vapor deposition. The effect of in situ grown CNFs on the flexural properties of the C/C composites was investigated by detailed analyses of destructive process. The results show that there is a sharp increase in the flexural load-displacement curve in the axial direction of the CNF-C/C composites, followed by a serrated yielding phenomenon similar to the plastic materials. The failure mode of the C/C composites modified with in situ grown CNFs is changed from the pull-out of single fiber to the breaking of fiber bundles. The existence of interfacial layer composed by middle-textured pyrocarbon, CNFs and high-textured pyrocarbon can block the crack propagation and change the propagation direction of the main crack, which leads to the higher flexural strength and modulus of C/C composites.

Finite Element Analysis on Plane Stress Crack Growth in a Power-Law Hardening Material

Aim To determine numerically the field characteristics in the vied at the tip of a place crack growing steadily in a power-law hardening material. Meteods. Methods on the Euler mode and small-scale yield assumption, the numerical results were given by nonlinear finite element analysis. Results The numerical results of the shape of the active plastic sone, the angular distribution of stresseses and Clack tip opening displacement (CTOD) in the vicinity at the hp of the steadily groWing CraCk are determined. Conclusion The comparison between the numerical results given by the present wort and those given by analytic asymptotic analysis shows that the present work reached a very high accuracy.

Research Progress of Biomass Fuel Composite Molding Technology

At present, the technology of biomass fuel composite molding technique is relatively lagging in China, which brings several negative influences, such as high energy consumption, short service life of the equipment. The current situation of the biomass pellet fuel molding technology at home and abroad was introduced, and the development direction in China was put forward, which was of great significance for enhancing the level of pellet fuel molding technology in China.

Recent Developments in Functional Crystals in China

Functional crystals are the basic materials for the development of modern science and technology and are playing key roles in the modern information era. In this paper, we review functional crystals in China, including research history, significant achievements, and important applications by highlighting the most recent progress in research. Challenges for the development of functional materials are discussed and possible directions for development are proposed by focusing on potential strengths of these materials.

Elastoplastic analysis of knee bracing frame

The knee bracing steel frame (KBF) is a new kind of energy dissipating frame, which combines excellent ductility and lateral stiffness. As the structural fuse of the frame, the knee element will yield first during a severe earthquake so that no damage occurs to the major structural members and the rehabilitation is easy and economical. To help fully understand the relations be- tween its seismic performance and the structural parameters, systematic elastoplastic analysis of the KBF structure with finite element method was conducted in this work. Finally, general design recommendations were made according to the results of the analysis.

A new patch antenna with metamaterial cover

A metamaterial was introduced into the cover of a patch antenna and its band structure was analyzed. The metama- terial cover with correct selection of the working frequency increases by 9.14 dB the patch antenna’s directivity. The mechanism of metamaterial cover is completely different from that of a photonic bandgap cover. The mechanism of the metamaterial cover, the number of the cover’s layers, and the distance between the layers, were analyzed in detail. The results showed that the metamaterial cover, which works like a lens, could effectively improve the patch antenna’s directivity. The physical reasons for the improvement are also given.

Nanocellulose Composites—Properties and Applications

Nanocellulose composites combine the advantages of nanocellulose and composites. Recently, nanocellulose composites have been received more attentions due to their improved properties and promising broad applications. In the past, rapid progress has been made in the synthesis, properties, and mechanism of nanocellulose composites and potential applications were reported. There are a few reports on the increasing applications of nanocellulose composites with focus on the biomedical field, environmental field, electrode and sensor applications. In this article, the recent development of nanocellulose composites was reviewed via some typical examples. In addition to the synthesis methods, improved properties and potential applications were discussed. The problems and future applications of nanocellulose composites were also suggested.

Review on the nanoparticle fluidization science and technology

Gas fluidization has an ability to turn static particles to fluid-like dense flow, which allows greatly improved heat transfer among porous powders and highly efficient solid processing to become reality. As the rising star of current scientific research, some nanoparticles can also be fluidized in the form of agglomerates, with sizes ranging from tens to hundreds of microns. Herein, we have reviewed the recent progress on nanomaterial agglomeration and their fluidization behavior, the assisted techniques to enhance the fluidization of nanomaterials,including some mechanical measures, external fields and improved gas injections, as well as their effects on solid fluidization and mixing behaviors. Most of these techniques are effective in breaking large agglomerates and promoting particulate fluidization, meanwhile, the solid mixing is intensified under assisted fluidization. The applications of nanofluidization in nanostructured material production and sustainable chemical industry are further presented. In summary, the fluidization science of multidimensional, multicomponent and multifunctional particles, their multi-phase characterization, and the guideline of fluidized bed coupled process are prerequisites for the sustainable development of fluidized bed based materials, energy and chemical industry.

The asymptotic field of mode Ⅰ quasi-static crack growth on the interface between a rigid and a pressure-sensitive material

A mechanical model of the quasi-static interface of a mode I crack between a rigid and a pressure-sensitive viscoelastic material was established to investigate the mechanical characteristic of ship-building engineering hi-materials. In the stable growth stage, stress and strain have the same singularity, ie （σ, ε） ∝ r^-1/（n-1）. The variable-separable asymptotic solutions of stress and strain at the crack tip were obtained by adopting Airy＇s stress function and the numerical results of stress and strain in the crack-tip field were obtained by the shooting method. The results showed that the near-tip fields are mainly governed by the power-hardening exponent n and the Poisson ratio v of the pressure-sensitive material. The fracture criterion of mode I quasi-static crack growth in pressure-sensitive materials, according to the asymptotic analyses of the crack-tip field, can be viewed from the perspective of strain.

Towards fully automatic modelling of the fracture process in quasi-brittle and ductile materials:a unified crack growth criterion

Fully automatic finite element(FE) modelling of the fracture process in quasi-brittle materials such as concrete and rocks and ductile materials such as metals and alloys,is of great significance in assessing structural integrity and presents tre-mendous challenges to the engineering community. One challenge lies in the adoption of an objective and effective crack propagation criterion. This paper proposes a crack propagation criterion based on the principle of energy conservation and the cohesive zone model(CZM) . The virtual crack extension technique is used to calculate the differential terms in the criterion. A fully-automatic discrete crack modelling methodology,integrating the developed criterion,the CZM to model the crack,a simple remeshing procedure to accommodate crack propagation,the J2 flow theory implemented within the incremental plasticity framework to model the ductile materials,and a local arc-length solver to the nonlinear equation system,is developed and im-plemented in an in-house program. Three examples,i.e.,a plain concrete beam with a single shear crack,a reinforced concrete(RC) beam with multiple cracks and a compact-tension steel specimen,are simulated. Good agreement between numerical predictions and experimental data is found,which demonstrates the applicability of the criterion to both quasi-brittle and ductile materials.

Fatigue crack growth mechanism in cast hybrid metal matrix composite reinforced with SiC particles and Al_2O_3 whiskers

The fatigue crack growth(FCG) mechanism of a cast hybrid metal matrix composite(MMC) reinforced with SiC particles and Al2O3 whiskers was investigated. For comparison, the FCG mechanisms of a cast MMC with Al2O3 whiskers and a cast Al alloy were also investigated. The results show that the FCG mechanism is observed in the near-threshold and stable-crack-growth regions.The hybrid MMC shows a higher threshold stress intensity factor range, ?Kth, than the MMC with Al2O3 and Al alloy, indicating better resistance to crack growth in a lower stress intensity factor range, ?K. In the near-threshold region with decreasing ?K, the two composite materials exhibit similar FCG mechanism that is dominated by debonding of the reinforcement–matrix interface, and followed by void nucleation and coalescence in the Al matrix. At higher ?K in the stable- or mid-crack-growth region, in addition to the debonding of the particle–matrix and whisker–matrix interface caused by cycle-by-cycle crack growth at the interface, the FCG is affected predominantly by striation formation in the Al matrix. Moreover, void nucleation and coalescence in the Al matrix and transgranular fracture of SiC particles and Al2O3 whiskers at high ?K are also observed as the local unstable fracture mechanisms.However, the FCG of the monolithic Al alloy is dominated by void nucleation and coalescence at lower ?K, whereas the FCG at higher ?K is controlled mainly by striation formation in the Al grains, and followed by void nucleation and coalescence in the Si clusters.

Lightweight Concrete Using Local Industrial By-product

Construction is one of the largest users of energy, material resources and water and it is a formidable polluter. One of the major materials used in construction is concrete and ordinary concrete contains about 12% cement which is a major producer of greenhouse gas in the world. The use of waste materials as partial replacement of cement in concrete reduces greenhouse gases, frees up land fill space, and reduces raw materials consumption. This contributes towards sustainable development, as in a sustainable society, nature is not subject to systematically increasing concentrations of substances extracted from the earth＇s crust. This research work explores the possibility of replacing some percentage of cement in concrete with marble sludge powder to produce lightweight concrete. This was achieved by determining the compressive strength and some hardened properties of concrete like sorptivity and carbonation with marble sludge. The results so far have been able to prove that lightweight concrete can be produced when some percentage of cement is replaced with this waste.

Advances in Hard Tissue Engineering Materials——Nanocellulose-based Composites

Nanocellulose(NC) has attracted much interest in the tissue engineering(TE) field because of its properties including biocompatibility,renewability, non-toxicity, functionality, and excellent mechanical performance. This review mainly focused on the advanced applications of NC-based composites in hard TE including cartilage TE, bone TE, and dental TE, illustrated the processing methods for synthesizing scaffolds including electrospinning, freeze-drying, and 3 D printing, reviewed the current status of hard TE, and presented perspective on the future of TE technology.

Marine Renewable Energy Seascape

Energy production based on fossil fuel reserves is largely responsible for carbon emissions, and hence global warming. The planet needs concerted action to reduce fossil fuel usage and to implement carbon mitigation measures. Ocean energy has huge potential, but there are major interdisciplinary problems to be overcome regarding technology, cost reduction, investment, environmental impact, governance, and so forth. This article briefly reviews ocean energy production from offshore wind, tidal stream, ocean current, tidal range, wave, thermal, salinity gradients, and biomass sources. Future areas of research and development are outlined that could make exploitation of the marine renewable energy （MRE） seascape a viable proposition; these areas include energy storage, advanced materials, robotics, and informatics. The article concludes with a sustainability perspective on the MRE seascape encompassing ethics, leg- islation, the regulatory environment, governance and consenting, economic, social, and environmental constraints. A new generation of engineers is needed with the ingenuity and spirit of adventure to meet the global challenge posed by MRE.

Analyzing the Share Composition of C02 Emissions in Asian Countries

This paper is concerned with the fossil fuel composition of carbon emissions in 10 selected Asian countries. It assesses how economic development may affect this composition through various channels. This paper contributes to the debate on the EKC （environmental Kuznets curve） puzzle, which hypothesizes an inverted U-shaped relationship between per capita income and pollution. The paper examines the EKC hypothesis in an empirical analysis of channels that may allow for this effect. In particular, a specific subset of this general paradigm is investigated using a fractional multinomial logit model to assess how indicators associated with economic development and energy prices affect carbon emissions from coal relative to those of natural gas and oil.