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Numerical investigation of the influence of casting techniques on fiber orientation distribution in ECC

Chung Nguyen VAN; Hai TRAN THANH; Thuc Nhu NGUYEN; Jianchun LI

《结构与土木工程前沿（英文）》 2022年第16卷第11期页码 1424-1435 doi: 10.1007/s11709-022-0870-9

摘要： Engineered cementitious composites (ECC), also known as bendable concrete, were developed based on engineering the interactions between fibers and cementitious matrix. The orientation of fibers, in this regard, is one of the major factors influencing the ductile behavior of this material. In this study, fiber orientation distributions in ECC beams influenced by different casting techniques are evaluated via numerical modeling of the casting process. Two casting directions and two casting positions of the funnel outlet with beam specimens are modeled using a particle-based smoothed particle hydrodynamics (SPH) method. In this SPH approach, fresh mortar and fiber are discretized by separated mortar and fiber particles, which smoothly interact in the computational domain of SPH. The movement of fiber particles is monitored during the casting simulation. Then, the fiber orientations at different sections of specimens are determined after the fresh ECC stops flowing in the formwork. The simulation results show a significant impact of the casting direction on fiber orientation distributions along the longitudinal wall of beams, which eventually influence the flexural strength of beams. In addition, casting positions show negligible influences on the orientation distribution of fibers in the short ECC beam, except under the pouring position.

关键词： ECC fiber orientation distribution casting direction casting position

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Crystallographic orientation effect on cutting-based single atomic layer removal

Wenkun XIE, Fengzhou FANG

《机械工程前沿（英文）》 2020年第15卷第4期页码 631-644 doi: 10.1007/s11465-020-0599-x

摘要： The ever-increasing requirements for the scalable manufacturing of atomic-scale devices emphasize the significance of developing atomic-scale manufacturing technology. The mechanism of a single atomic layer removal in cutting is the key basic theoretical foundation for atomic-scale mechanical cutting. Material anisotropy is among the key decisive factors that could not be neglected in cutting at such a scale. In the present study, the crystallographic orientation effect on the cutting-based single atomic layer removal of monocrystalline copper is investigated by molecular dynamics simulation. When undeformed chip thickness is in the atomic scale, two kinds of single atomic layer removal mechanisms exist in cutting-based single atomic layer removal, namely, dislocation motion and extrusion, due to the differing atomic structures on different crystallographic planes. On close-packed crystallographic plane, the material removal is dominated by the shear stress-driven dislocation motion, whereas on non-close packed crystallographic planes, extrusion-dominated material removal dominates. To obtain an atomic, defect-free processed surface, the cutting needs to be conducted on the close-packed crystallographic planes of monocrystalline copper.

关键词： ACSM single atomic layer removal mechanism crystallographic orientation effect mechanical cutting Manufacturing III

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Tomographic diagnosis of defects in hydraulic concrete structure

ZHAO Mingjie, XU Xibin

《结构与土木工程前沿（英文）》 2008年第2卷第3期页码 226-232 doi: 10.1007/s11709-008-0027-5

摘要： The ultrasonic tomographic technology is applied to diagnose the defects in hydraulic concrete structure. In order to improve the precision of diagnoses, the wavelet transformation is used in the processing of ultrasonic signals. The influences of water, scale and orientation of defect, processing methods and theoretical model on image resolution are investigated. The experimental results indicate that the result of the tomographic diagnosis of a single defect is sensitive and the boundary can be clearly determined. However, the image resolution of multiple defects is not satisfactory. The water content and scale of a defect may significantly affect the imaging resolution. Defects with the orientation perpendicular to the direction of the diagnosis may have higher precision in diagnosing. The wavelet transformation technology can elevate the imaging resolution. The applied calculation model plays a very important role in improving the accuracy of detection.

关键词： satisfactory processing orientation tomographic diagnosis orientation perpendicular

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Planar jumping with stable landing through foot orientation design and ankle joint control

Qilong YUAN, I-Ming CHEN

《机械工程前沿（英文）》 2012年第7卷第2期页码 100-108 doi: 10.1007/s11465-012-0318-3

摘要：

This paper introduces a method to generate the planar jumping motion for biped robot. In this work, through determining the upper body posture trajectory in the flight phase, the foot landing posture is made to be flat while landing. Together with properly designing the trajectory for local center of gravity and the foot landing velocity, the soft landing trajectory is generated. A controller on the ankle joint is added to avoid significant impact with the ground and stabilize the robot after landing. Jumping motion with stable landing is achieved in a dynamic simulation environment based on this method.

关键词： biped jumping stable landing control jumping motion generation

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Build orientation determination of multi-feature mechanical parts in selective laser melting via multi-objective

《机械工程前沿（英文）》 2023年第18卷第2期 doi: 10.1007/s11465-022-0737-8

摘要： Selective laser melting (SLM) is a unique additive manufacturing (AM) category that can be used to manufacture mechanical parts. It has been widely used in aerospace and automotive using metal or alloy powder. The build orientation is crucial in AM because it affects the as-built part, including its part accuracy, surface roughness, support structure, and build time and cost. A mechanical part is usually composed of multiple surface features. The surface features carry the production and design knowledge, which can be utilized in SLM fabrication. This study proposes a method to determine the build orientation of multi-feature mechanical parts (MFMPs) in SLM. First, the surface features of an MFMP are recognized and grouped for formulating the particular optimization objectives. Second, the estimation models of involved optimization objectives are established, and a set of alternative build orientations (ABOs) is further obtained by many-objective optimization. Lastly, a multi-objective decision making method integrated by the technique for order of preference by similarity to the ideal solution and cosine similarity measure is presented to select an optimal build orientation from those ABOs. The weights of the feature groups and considered objectives are achieved by a fuzzy analytical hierarchy process. Two case studies are reported to validate the proposed method with numerical results, and the effectiveness comparison is presented. Physical manufacturing is conducted to prove the performance of the proposed method. The measured average sampling surface roughness of the most crucial feature of the bracket in the original orientation and the orientations obtained by the weighted sum model and the proposed method are 15.82, 10.84, and 10.62 μm, respectively. The numerical and physical validation results demonstrate that the proposed method is desirable to determine the build orientations of MFMPs with competitive results in SLM.

关键词： selective laser melting (SLM) build orientation determination multi-feature mechanical part (MFMP) fuzzy analytical hierarchy process multi-objective decision making (MODM)

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the mechanical performance and damage failure characteristics of laminated composites based on fiber orientation

《结构与土木工程前沿（英文）》页码 1357-1369 doi: 10.1007/s11709-023-0996-4

摘要： In this study, the effect of fiber angle on the tensile load-bearing performance and damage failure characteristics of glass composite laminates was investigated experimentally, analytically, and numerically. The glass fabric in the laminate was perfectly aligned along the load direction (i.e., at 0°), offset at angles of 30° and 45°, or mixed in different directions (i.e., 0°/30° or 0°/45°). The composite laminates were fabricated using vacuum-assisted resin molding. The influence of fiber orientation angle on the mechanical properties and stiffness degradation of the laminates was studied via cyclic tensile strength tests. Furthermore, simulations have been conducted using finite element analysis and analytical approaches to evaluate the influence of fiber orientation on the mechanical performance of glass laminates. Experimental testing revealed that, although the composite laminates laid along the 0° direction exhibited the highest stiffness and strength, their structural performance deteriorated rapidly. We also determined that increasing the fiber offset angle (i.e., 30°) could optimize the mechanical properties and damage failure characteristics of glass laminates. The results of the numerical and analytical approaches demonstrated their ability to capture the mechanical behavior and damage failure modes of composite laminates with different fiber orientations, which may be used to prevent the catastrophic failures that occur in composite laminates.

关键词： fiber orientation composite laminates stiffness degradation analytical approaches finite element analysis

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一种静电纺具有超高分子链取向纳米纤维的通用策略 Article

文显, 熊健, 孙朝阳, 王黎明, 俞建勇, 覃小红

《工程（英文）》 2023年第29卷第10期页码 179-187 doi: 10.1016/j.eng.2022.09.008

摘要：

聚合物分子链取向度是决定纤维机械性质和物理性能的关键结构参数。然而，理解和大幅调控纤维大分子链取向仍面临巨大挑战。本文提出一种新型的静电纺丝方法，通过控制纺丝过程中的电场来有效调节分子链取向。与典型的静电纺丝相比，新型静电纺丝通过将电场施加在圆环上而非针头上来分离控制电场。得益于这一变化，实现了一种新的电场分布，从而产生非单调变化的牵伸作用力。结果表明，聚环氧乙烷（PEO）纳米纤维的大分子链取向得到显著改善，实现了超高红外二向色性比。与此同时，PEO射流细度可有效降低80%左右，纳米纤维直径从约298 nm降低至约114 nm。并且，与普通材料中高取向导致的高结晶度不同，该方法在提高纤维分子链取向度的同时使结晶度从74.9%显著降低至31.7%。这项工作为制备具有优化取向-结晶度特性的先进电纺纳米纤维提供了新的认识。

关键词：分子链取向静电纺丝纳米纤维电场聚环氧乙烷

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Management and Practice of Large-Scale Modern Coal Enterprises

An Wang

《工程管理前沿（英文）》 2014年第1卷第1期页码 13-17 doi: 10.15302/J-FEM-2014004

摘要： As the coal-dominated energy structure will remain unchanged in the short term, the sustainable development of the coal industry is still serving as one of the foundations for the sound development of the national economy. The construction of modernized mines based on "four orientations", that is, orientations of scale production, modern technology and equipment, informationized management and professional working team, has been rapidly enhancing its development in the recent decade. However, in the next decade or an even longer period, the industry, with the energy centre shifting to the West of China, will be exposed to new options and development in the layout, structure, model, technology, etc.

关键词： coal industry sustainable development the four-orientation model

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A Further Discussion on Trends in the Development of Advanced Manufacturing Technology

YANG Shu-zi, WU Bo, LI Bin

《机械工程前沿（英文）》 2006年第1卷第1期页码 1-5 doi: 10.1007/s11465-005-0002-y

摘要：

This paper is a supplement to Trends in the Development of Advanced Manufacturing Technology (Yang and Wu in Chin. J. Mech. Eng., 39: 73, 2003) but delves deeper into it. It first points out the strategic status of manufacturing industry in state development. Then, a detailed analysis is given on the features and trends in the development of advanced manufacturing technology in a total of 12 points from three aspects: precision, extreme, and culture from the aspect of the product itself; green, rapidness, saving, and efficiency during the manufacturing process; and digit, auto, integration, networking, and intelligence in view of the manufacturing method. In addition, it emphasizes that all the above aspects should be based on two base points: manufacture and machinery. Finally, it puts forth the guiding ideologies for the development of advanced manufacturing technology and the aspects China should give priority to in development, while stressing on the principles of independence, innovation and human orientation.

关键词： Development development integration networking orientation

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A comprehensive review of greenhouse shapes and its applications

Ravinder Kumar SAHDEV,Ashwani Kumar DHINGRA,Mahesh KUMAR

《能源前沿（英文）》 2019年第13卷第3期页码 427-438 doi: 10.1007/s11708-017-0464-8

摘要： Greenhouse technology is a practical option for the production and drying of agricultural products in controlled environment. For the successful design of a greenhouse, the selection of a suitable shape and orientation is of great importance. Of various shapes of greenhouses, the even-span roof and the Quonset shape greenhouses are the most commonly used for crop cultivation and drying. The orientation of greenhouses is kept east–west for maximum utilization of solar radiations. Hybrid and modified greenhouse dryers have been proposed for drying of products. The agricultural products dried in greenhouses are found to be better in quality as compared to open sun drying because they are protected from dust, rain, insects, birds and animals. Moreover, various greenhouses shapes along with their applications have been reviewed.

关键词： greenhouse shapes drying solar energy agriculture products orientation

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模块化射孔工艺技术

郭景学,姜晓燕,王文昌

《中国工程科学》 2012年第14卷第4期页码 26-30

摘要：

介绍了一种新型射孔完井技术——模块化电缆射孔工艺技术。它采用单芯电缆传输方式，首先将射孔器支撑装置锚定到预定深度，然后将射孔所需全部模块化射孔器分次下入井内，最后引爆射孔弹，从而达到多支射孔器分次下井、一次点火完成的目的。在此基础上，通过特殊的导向装置设计，实现电缆定方位射孔。它的优点是充分发挥了电缆传输方式动用设备少、作业方便、施工时间短等优势，又实现了部分油管输送射孔的功能，如全井负压射孔、防喷等。另外，在高压油气井射孔时，模块化射孔器可自动丢到井底，油气井直接生产，对高压油气不会产生截流。如果想起出

关键词：射孔模块化定方位

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Research on constraint-based virtual assembly technologies

YANG Rundang, WU Dianliang, FAN Xiumin, YAN Juanqi

《机械工程前沿（英文）》 2007年第2卷第2期页码 243-249 doi: 10.1007/s11465-007-0043-5

摘要： To realize a constraint-based virtual assembly operation, the unified representations of the assembly constraint, the equivalent relation between the constraint and the degree of freedom (DOF), and the movement DOF reduction in a virtual environment are proposed. Several algorithms about the constraint treatment are submitted. First, the automatic recognition algorithm based on the assembly relation is used to determine the position and orientation relation between two geometry elements of constraint whether they meet the given errors. Second, to satisfy the new constraint, according to the positing solving algorithm, the position and orientation of an active part are modified with minimal adjustment after the part has satisfied the affirmed constraints. Finally, the algorithm of movement navigation based on the generalized coordinate system is put forward, and the part movement is guided. These algorithms have been applied to the integrated virtual assembly environment (IVAE) system. Experiments have indicated that these algorithms have well supported constraint treatments in the IVAE and realized the closer combination of the virtual and the real assembly processes.

关键词： movement DOF recognition algorithm assembly orientation combination

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Reassessment of fenestration characteristics for residential buildings in hot climates: energy and economic analysis

Ali ALAJMI, Hosny ABOU-ZIYAN, Hamad H. Al-MUTAIRI

《能源前沿（英文）》 2022年第16卷第4期页码 629-650 doi: 10.1007/s11708-021-0799-z

摘要： This paper attempts to resolve the reported contradiction in the literature about the characteristics of high-performance/cost-effective fenestration of residential buildings, particularly in hot climates. The considered issues are the window glazing property (ten commercial glazing types), facade orientation (four main orientations), window-to-wall ratio (WWR) (0.2–0.8), and solar shading overhangs and side-fins (nine shading conditions). The results of the simulated runs reveal that the glazing quality has a superior effect over the other fenestration parameters and controls their effect on the energy consumption of residential buildings. Thus, using low-performance windows on buildings yields larger effects of WWR, facade orientation, and solar shading than high-performance windows. As the WWR increases from 0.2 to 0.8, the building energy consumption using the low-performance window increases 6.46 times than that using the high-performance window. The best facade orientation is changed from north to south according to the glazing properties. In addition, the solar shading need is correlated as a function of a window-glazing property and WWR. The cost analysis shows that the high-performance windows without solar shading are cost-effective as they have the largest net present cost compared to low-performance windows with or without solar shading. Accordingly, replacing low-performance windows with high-performance ones, in an existing residential building, saves about 12.7 MWh of electricity and 11.05 tons of CO₂ annually.

关键词： parametric analysis high-performance window window-to-wall ratio (WWR) facade orientation solar shading cost analysis

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Dynamic modeling of flexible-links planar parallel robots

DU Zhaocai, YU Yueqing, ZHANG Xuping, DU Zhaocai

《机械工程前沿（英文）》 2008年第3卷第2期页码 232-237 doi: 10.1007/s11465-008-0032-3

摘要： This paper presents a finite element-based method for dynamic modeling of parallel robots with flexible links and rigid moving platform. The elastic displacements of flexible links are investigated while considering the coupling effects between links due to the structural flexibility. The kinematic constraint conditions and dynamic constraint conditions for elastic displacements are presented. Considering the effects of distributed mass, lumped mass, shearing deformation, bending deformation, tensile deformation and lateral displacements, the Kineto-Elasto dynamics (KED) theory and Lagrange formula are used to derive the dynamic equations of planar flexible-links parallel robots. The dynamic behavior of the flexible-links planar parallel robot is well illustrated through numerical simulation of a planar 3-RR parallel robot. Compared with the results of finite element software SAMCEF, the numerical simulation results show good coherence of the proposed method. The flexibility of links is demonstrated to have a significant impact on the position error and orientation error of the flexible-links planar parallel robot.

关键词： 3-RR parallel KED coupling software SAMCEF orientation

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Spontaneous polarization enhanced bismuth ferrate photoelectrode: fabrication and boosted photoelectrochemical water splitting property

《能源前沿（英文）》 2021年第15卷第3期页码 781-790 doi: 10.1007/s11708-021-0782-8

摘要： In this paper, the fabrication of a highly orientated Bi₂Fe₄O₉ (BFO) photoelectrode in the presence of two-dimensional (2D) graphene oxide (GO) was reported. It was found that the GO can be used as a template for controlling the growth of BFO, and the nanoplate composites of BFO/reduced graphene oxide (RGO) with a high orientation can be fabricated. The thickness of the nanoplates became thinner as the ratio of GO increased. As a result, the ferroelectric spontaneous polarization unit arranges itself in the space in a periodic manner, leading to the formation of a polarization field along a special direction. Therefore, the created built-in electric field of the nanoplate composites of BFO/RGO is improved upon the increase of the amount of RGO. As expected, carrier separation is enhanced by the built-in electric field, therefore substantially enhancing the photoelectrochemical (PEC) activity of water splitting compared to pure BFO under the irradiation of visible-light.

关键词： bismuth ferrate ferroelectric polarisation photoelectrochemical (PEC) water splitting graphene oxide (GO) high orientation