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Digital high-efficiency print forming method and device for multi-material casting molds

Zhongde SHAN, Zhi GUO, Dong DU, Feng LIU, Wenjiang LI

《机械工程前沿（英文）》 2020年 第15卷 第2期   页码 328-337 doi: 10.1007/s11465-019-0574-6

摘要： Sand mold 3D printing technology based on the principle of droplet ejection has undergone rapid development in recent years and has elicited increasing attention from engineers and technicians. However, current sand mold 3D printing technology exhibits several problems, such as single-material printing molds, low manufacturing efficiency, and necessary post-process drying and heating for the manufacture of sand molds. This study proposes a novel high-efficiency print forming method and device for multi-material casting molds. The proposed method is specifically related to the integrated forming of two-way coating and printing and the short-flow manufacture of roller compaction and layered heating. These processes can realize the high-efficiency print forming of high-performance sand molds. Experimental results demonstrate that the efficiency of sand mold fabrication can be increased by 200% using the proposed two-way coating and printing method. The integrated forming method for layered heating and roller compaction presented in this study effectively shortens the manufacturing process for 3D-printed sand molds, increases sand mold strength by 63.8%, and reduces resin usage by approximately 30%. The manufacture of multi-material casting molds is demonstrated on typical wheeled cast-iron parts. This research provides theoretical guidance for the engineering application of sand mold 3D printing.

关键词： multi-material casting mold     3D printing     efficient print forming method    

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Finite element simulations of sheet metal forming under complex strain paths

CHEN Wei, YANG Jichang, WU Xiaofeng, LU Dun, GUO Weigang

《机械工程前沿（英文）》 2007年 第2卷 第4期   页码 399-403 doi: 10.1007/s11465-007-0069-8

摘要： Fracture is a common defect in sheet metal forming and it is essentially caused by tensile instability. This paper analyzes some experiments and theories for building forming limit diagrams of sheet metal and points out the advantages and disadvantages of current experiments and theories. According to this, a method that integrates the finite element simulation and experiment was used to research the forming limit diagrams of the sheet metal under complex strain paths. Taking the rear hanger that undergoes twice stamping as an example, the strain paths of the dangerous point of the rear hanger is investigated. Finally, the forming method of the rear hanger is confirmed. Results indicate that finite element method (FEM) can achieve the complex strain paths and different strain paths will have great impacts on the result of the sheet metal forming.

关键词： dangerous     forming method     different     hanger     forming    

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FEM-based strain analysis study for multilayer sheet forming process

Rongjing ZHANG,Lihui LANG,Rizwan ZAFAR

《机械工程前沿（英文）》 2015年 第10卷 第4期   页码 373-379 doi: 10.1007/s11465-015-0371-9

摘要：

Fiber metal laminates have many advantages over traditional laminates (e.g., any type of fiber and resin material can be placed anywhere between the metallic layers without risk of failure of the composite fabric sheets). Furthermore, the process requirements to strictly control the temperature and punch force in fiber metal laminates are also less stringent than those in traditional laminates. To further explore the novel method, this study conducts a finite element method-based (FEM-based) strain analysis on multilayer blanks by using the 3A method. Different forming modes such as wrinkling and fracture are discussed by using experimental and numerical studies. Hydroforming is used for multilayer forming. The Barlat 2000 yield criteria and DYNAFORM/LS-DYNA are used for the simulations. Optimal process parameters are determined on the basis of fixed die-binder gap and variable cavity pressure. The results of this study will enhance the knowledge on the mechanics of multilayer structures formed by using the 3A method and expand its commercial applications.

关键词： finite element method (FEM)     strain analysis     multilayer sheet forming    

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Application of an efficient stochastic calculation method on the seismic analysis of an isolated structure

Wei GUO, Zhiwu YU

《结构与土木工程前沿（英文）》 2012年 第6卷 第4期   页码 379-384 doi: 10.1007/s11709-012-0180-8

摘要： An isolated structure often possesses distinct non-proportional damping characteristics. However, traditional seismic calculation theory and methods are derived based on the assumption that damping is proportional. Based on this drawback, a new, more efficient stochastic calculation method, an improvement on the pseudo-excitation method, is introduced. This method is then applied to the seismic analysis of an isolated structure. By comparing it with the forced decoupling, matrix inversion and iteration methods, it is shown that the presented method can produce accurate results while increasing the efficiency of the stochastic analysis. Moreover, the calculation process of the seismic response of an isolated structure is convergent. Based on the results of the example presented in this paper, the given method is applicable to the seismic analysis of an isolated structure and can be utilized in practice.

关键词： isolated structure     stochastic response     non-proportional damping     efficient     accurate     pseudo-excitation method    

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New method for efficient control of hydrogen sulfide and methane in gravity sewers: Combination of NaOH

《环境科学与工程前沿（英文）》 2022年 第16卷 第6期 doi: 10.1007/s11783-021-1509-0

摘要：

• The combination of NaOH and nitrite was used to control harmful gas in sewers.

关键词： Sewer corrosion     Sulfide control     Combination treatment     NaOH     Nitrite    

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An efficient method for the dynamic interaction of open structure-foundation systems

LIU Jingbo, GU Yin, LI Bin, WANG Yan

《结构与土木工程前沿（英文）》 2007年 第1卷 第3期   页码 340-345 doi: 10.1007/s11709-007-0045-8

摘要： The structure-foundation system is transformed from an original open system into an approximately hermetic system through a viscous-spring artificial boundary. In addition, the seismic wave scattering problem is changed to a wave source problem by employing an equivalent seismic wave input method. Subsequently, the modal superposition method is adopted to solve the approximated hermetic system. This procedure is highly efficient in analyzing dynamic structure-foundation interaction problems in the time domain. Two numerical examples are presented to illustrate the characteristics of the proposed method: one is a wave source problem in 2-dimensions (2-D) elastic semi-infinite space, and the other is a dynamic structure-foundation interaction problem under seismic excitations. Compared with the traditional direct step-by-step integration method, the proposed method, with a sufficient number of modes included, can significantly reduce the computational time with almost the same precision. The results also indicate that the proposed method is more advantageous for solving large structure-foundation systems of many degrees of freedom.

关键词： structure-foundation interaction     superposition     interaction problem     freedom     efficient    

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An efficient two-stage approach for structural damage detection using meta-heuristic algorithms and groupmethod of data handling surrogate model

Hamed FATHNEJAT, Behrouz AHMADI-NEDUSHAN

《结构与土木工程前沿（英文）》 2020年 第14卷 第4期   页码 907-929 doi: 10.1007/s11709-020-0628-1

摘要： In this study, the performance of an efficient two-stage methodology which is applied in a damage detection system using a surrogate model of the structure has been investigated. In the first stage, in order to locate the damage accurately, the performance of the modal strain energy based index for using different numbers of natural mode shapes has been evaluated using the confusion matrix. In the second stage, to estimate the damage extent, the sensitivity of most used modal properties due to damage, such as natural frequency and flexibility matrix is compared with the mean normalized modal strain energy (MNMSE) of suspected damaged elements. Moreover, a modal property change vector is evaluated using the group method of data handling (GMDH) network as a surrogate model during damage extent estimation by optimization algorithm; in this part of methodology, the performance of the three popular optimization algorithms including particle swarm optimization (PSO), bat algorithm (BA), and colliding bodies optimization (CBO) is examined and in this regard, root mean square deviation ( ) based on the modal property change vector has been proposed as an objective function. Furthermore, the effect of noise in the measurement of structural responses by the sensors has also been studied. Finally, in order to achieve the most generalized neural network as a surrogate model, GMDH performance is compared with a properly trained cascade feed-forward neural network (CFNN) with log-sigmoid hidden layer transfer function. The results indicate that the accuracy of damage extent estimation is acceptable in the case of integration of PSO and MNMSE. Moreover, the GMDH model is also more efficient and mimics the behavior of the structure slightly better than CFNN model.

关键词： two-stage method     modal strain energy     surrogate model     GMDH     optimization damage detection    

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Formation mechanism and modeling of surface waviness in incremental sheet forming

《机械工程前沿（英文）》 2022年 第17卷 第2期 doi: 10.1007/s11465-022-0679-1

摘要： Improving and controlling surface quality has always been a challenge for incremental sheet forming (ISF), whereas the generation mechanism of waviness surface is still unknown, which impedes the widely application of ISF in the industrial field. In this paper, the formation mechanism and the prediction of waviness are both investigated through experiments, numerical simulation, and theoretical analysis. Based on a verified finite element model, the waviness topography is predicted numerically for the first time, and its generation is attributed to the residual bending deformation through deformation history analysis. For more efficient engineering application, a theoretical model for waviness height is proposed based on the generation mechanism, using a modified strain function considering deformation modes. This work is favorable for the perfection of formation mechanism and control of surface quality in ISF.

关键词： surface waviness     incremental sheet forming     numerical simulation     formation mechanism     deformation history    

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Meshless numerical method based on tensor product

SUN Haitao, WANG Yuanhan, MIAO Yu

《结构与土木工程前沿（英文）》 2008年 第2卷 第2期   页码 166-171 doi: 10.1007/s11709-008-0021-y

摘要： A normalized space constructed by tensor product is used in field function approach to give a special case of moving least squares (MLS) interpolation scheme. In the regular domain, the field function which meets homogenous boundary conditions is constructed by spanning base space to make the MLS interpolation scheme simpler and more efficient. Owing to expanded basis functions selection, some drawbacks in general MLS method, for example repeated inversion, low calculation efficiency, and complex criterions, can be avoided completely. Numerical examples illustrate that the proposed method is characterized by simple mathematical concept, convenient repeat calculations with high accuracy, good continuity, less computation and rapid convergence.

关键词： mathematical     continuity     inversion     selection     efficient    

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Hybrid forming mechanism of patternless casting and laser cladding

Zhongde SHAN, Fuzhen SUN, Yang LIU

《机械工程前沿（英文）》 2019年 第14卷 第4期   页码 393-401 doi: 10.1007/s11465-019-0550-1

摘要： In accordance with the requirement of manufacturing dies quickly and economically, a hybrid forming method of stamping dies for automobile panels is proposed. The method combines digital patternless casting and high-power laser cladding. An experimental study is conducted on the hybrid forming process and its trial production and application in the manufacturing of stamping dies for typical panels. Results prove that the laser cladding layer exceeds HRC60 (Rockwell hardness) and thus meets the production efficiency requirement of automobile dies. The rate of defects is well controlled. Compared with traditional technology, this technology has remarkable advantages and advancement.

关键词： patternless casting     laser cladding     hybrid forming     rapid tooling    

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Highlight yield forming and innovative technologies in tropical crops

Wenquan WANG

《农业科学与工程前沿（英文）》 2016年 第3卷 第4期   页码 283-284 doi: 10.15302/J-FASE-2016128

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Properties and effect of forming sewage sludge into lightweight ceramics

Min YUE, Qinyan YUE, Yuanfeng QI, Baoyu GAO, Hui YU

《环境科学与工程前沿（英文）》 2012年 第6卷 第1期   页码 117-124 doi: 10.1007/s11783-010-0220-3

摘要： In this work we investigated the chemical, thermal and toxic properties of dried sewage sludge (DSS), the preparation and properties of lightweight sludge ceramic (LSC) and the mechanisms of action of the organic and inorganic foaming agents (OFAs and IFAs). The chemical components and thermal properties of the raw materials were studied by Energy Dispersive X-ray Detection (EDX) and Thermogravimetric Analysis and Differential Scanning Calorimetry (DSC/TGA). The mineral phases of the raw materials and the formed ceramics were determined by X-ray Diffraction (XRD). The leaching characteristics of heavy metals were investigated with Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Different ratios of DSS and clay were mixed and pressed into raw pellets. After drying and preheating treatment, the raw pellets were sintered at 1150°C for 10 min. The physical properties of LSC (50 wt% DSS added) were tested. The results showed that when the addition of DSS was above 50 wt%, LSC began to shrink, and a maximum density occurred. The environmental safety of LSC was satisfactory. XRD showed that some new mineral phases formed in the LSC. Observation of the microstructure by Scanning Electron Microscope (SEM) indicated that the body of LSC was porous.

关键词： sludge     foaming agents     ceramics     preheating process    

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Transient performance comparison of grid-forming converters with different FRT control strategies

《能源前沿（英文）》 2023年 第17卷 第2期   页码 239-250 doi: 10.1007/s11708-022-0856-2

摘要： Grid-forming converters (GFMs) are faced with the threat of transient inrush current and synchronization instability issues when subjected to grid faults. Instead of disconnecting from the grid unintentionally, GFMs are required to have fault ride through (FRT) capability to maintain safe and stable operation in grid-connected mode during grid fault periods. In recent studies, different FRT control strategies with distinguishing features and that are feasible for different operation conditions have been proposed for GFMs. To determine their application scope, an intuitive comparison of the transient performance of different FRT control strategies is presented in this paper. First, three typical FRT control strategies (virtual impedance, current limiters, and mode-switching control) are introduced and transient mathematical models are established. A detailed comparison analysis on transient inrush current and transient synchronization stability is then presented. The results will be useful for guiding the selection and design of FRT control strategies. Finally, simulation results based on PSCAD/EMTDC are considered to verify the correctness of the theoretical analysis.

关键词： grid-forming converters (GFMs)     fault ride through (FRT)     transient stability     transient inrush current     transient modeling    

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An efficient stochastic dynamic analysis of soil media using radial basis function artificial neural

P. ZAKIAN

《结构与土木工程前沿（英文）》 2017年 第11卷 第4期   页码 470-479 doi: 10.1007/s11709-017-0440-8

摘要： Since a lot of engineering problems are along with uncertain parameters, stochastic methods are of great importance for incorporating random nature of a system property or random nature of a system input. In this study, the stochastic dynamic analysis of soil mass is performed by finite element method in the frequency domain. Two methods are used for stochastic analysis of soil media which are spectral decomposition and Monte Carlo methods. Shear modulus of soil is considered as a random field and the seismic excitation is also imposed as a random process. In this research, artificial neural network is proposed and added to Monte Carlo method for sake of reducing computational effort of the random analysis. Then, the effects of the proposed artificial neural network are illustrated on decreasing computational time of Monte Carlo simulations in comparison with standard Monte Carlo and spectral decomposition methods. Numerical verifications are provided to indicate capabilities, accuracy and efficiency of the proposed strategy compared to the other techniques.

关键词： stochastic analysis     random seismic excitation     finite element method     artificial neural network     frequency domain analysis     Monte Carlo simulation    

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A new method for the synthesis of molybdovanadophosphoric heteropoly acids and their catalytic activities

ZHANG Fumin, GUO Maiping, GE Hanqing, WANG Jun

《化学科学与工程前沿（英文）》 2007年 第1卷 第3期   页码 296-299 doi: 10.1007/s11705-007-0054-0

摘要： An environmentally benign method for the synthesis of heteropoly acids HPMoVO·HO (PMoV, = 1−3) was developed by the reaction of an aqueous slurry which contained stoichiometric amounts of MoO, VO and HPO. Characterization of the as-synthesized catalysts with inductively coupled plasma (ICP) elemental analysis, thermogravimetry (TG), X-ray diffraction (XRD) and infrared (IR) spectroscopy indicated that V ions substituted for Mo ions in Keggin-type phosphomolybdic acid. The as-synthesized samples were found to be an efficient catalyst for the hydroxylation of benzene which was carried out in a mixed solvent of acetonitrile and acetic acid with aqueous hydrogen peroxide as oxidant. PMoV exhibi ted the highest benzene conversion of 34.5% with phenol selectivity of 100%.

关键词： conversion     heteropoly     Characterization     efficient catalyst     Keggin-type phosphomolybdic    

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标题 作者 时间 类型 操作

Digital high-efficiency print forming method and device for multi-material casting molds

Zhongde SHAN, Zhi GUO, Dong DU, Feng LIU, Wenjiang LI

期刊论文

Finite element simulations of sheet metal forming under complex strain paths

CHEN Wei, YANG Jichang, WU Xiaofeng, LU Dun, GUO Weigang

期刊论文

FEM-based strain analysis study for multilayer sheet forming process

Rongjing ZHANG,Lihui LANG,Rizwan ZAFAR

期刊论文

Application of an efficient stochastic calculation method on the seismic analysis of an isolated structure

Wei GUO, Zhiwu YU

期刊论文

New method for efficient control of hydrogen sulfide and methane in gravity sewers: Combination of NaOH

期刊论文

An efficient method for the dynamic interaction of open structure-foundation systems

LIU Jingbo, GU Yin, LI Bin, WANG Yan

期刊论文

An efficient two-stage approach for structural damage detection using meta-heuristic algorithms and groupmethod of data handling surrogate model

Hamed FATHNEJAT, Behrouz AHMADI-NEDUSHAN

期刊论文

Formation mechanism and modeling of surface waviness in incremental sheet forming

期刊论文

Meshless numerical method based on tensor product

SUN Haitao, WANG Yuanhan, MIAO Yu

期刊论文

Hybrid forming mechanism of patternless casting and laser cladding

Zhongde SHAN, Fuzhen SUN, Yang LIU

期刊论文

Highlight yield forming and innovative technologies in tropical crops

Wenquan WANG

期刊论文

Properties and effect of forming sewage sludge into lightweight ceramics

Min YUE, Qinyan YUE, Yuanfeng QI, Baoyu GAO, Hui YU

期刊论文

Transient performance comparison of grid-forming converters with different FRT control strategies

期刊论文

An efficient stochastic dynamic analysis of soil media using radial basis function artificial neural

P. ZAKIAN

期刊论文

A new method for the synthesis of molybdovanadophosphoric heteropoly acids and their catalytic activities

ZHANG Fumin, GUO Maiping, GE Hanqing, WANG Jun

期刊论文