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Yuan B.,Tianjin University of Technology and Education | Fang W.,Tianjin University of Technology and Education | Li J.,Tianjin Long March Launch Vehicle Manufacturing Co. | Cai Y.,Tianjin University of Technology and Education | And 2 more authors.
Engineering Analysis with Boundary Elements | Year: 2016

Viscous pressure forming (VPF) is a kind of sheet flexible-die forming process which uses a semisolid, flowable and viscous material as the pressure-transmitting medium. Unlike the conventional rigid die punching or hydroforming process, there are strong nonlinear features between the sheet metal and viscous medium in VPF. In this paper, a numerical analysis method for coupling sheet metal deformation and bulk deformation of viscous medium is presented. A static explicit approach based on the Updated Lagrangian (U.L.) formulation is adopted. The elastoplastic deformation of sheet metal is analyzed with finite element method (FEM), and the visco-elastoplastic bulk deformation of viscous medium is analyzed with the element-free Galerkin method (EFGM), which can eliminate mesh distortion unavoidable during the deformation of viscous medium in FEM. The contact and friction between the sheet metal and viscous medium are treated by the penalty function method. An FEM-EFGM program for coupled deformation between sheet metal and viscous medium is developed, called CDSB-FEM-EFGM for short. Several numerical examples of coupled deformation between viscous mediums with different viscosities and sheet metal are presented to demonstrate the effectiveness of the proposed method. Compared the numerical simulation results with experimental measurements, the validity of the CDSB-FEM-EFGM program is obtained. © 2016 Published by Elsevier Ltd. Source


Fan X.,Harbin Institute of Technology | Wang L.,Harbin Institute of Technology | Du Z.,Tianjin Long March Launch Vehicle Manufacturing Co. | Su Y.,Harbin Institute of Technology | And 6 more authors.
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2015

Ansoft software was used to simulate the electromagnetic force of the cylindrical thin-walled casts under the action of traveling magnetic field, and the influence of excitation currents on mold-filling capacity of different alloys and surface depression of thin-walled casts were investigated. The results show that the magnetic field remarkably influences the mold-filling capacity of alloys and the casting surface depression simultaneously. The mold-filling capacity and the possibility of the surface depression are increased with the square of the excitation current intensity increasing. Under the same excitation current intensity, the excitation current frequency has the optimal value to the mold-filling capacity; the possibility of the casting surface depression decreases along with its decrease below 1000 Hz. © 2015, Science Press. All right reserved. Source


Fan X.-Y.,Harbin Institute of Technology | Wang L.,Harbin Institute of Technology | Du Z.-Q.,Tianjin Long March Launch Vehicle Manufacturing Co. | Zhang J.-B.,China Shoudu Space Machinery Company | And 4 more authors.
China Foundry | Year: 2015

The effect of excitation current intensity on the mechanical properties of ZL205A castings solidified under a traveling magnetic field was studied. The results of the experiment indicate that the excitation current intensity of the traveling magnetic field has a great influence on the mechanical properties of the ZL205A castings. When the excitation current intensity is 15 A, the tensile strength and elongation of ZL205A alloy castings increase 27.2% and 67.7%, respectively, compared with those of the same alloy solidified under gravity. The improvement of mechanical properties is attributed to the decrease of micro-porosity in the alloy. Under the traveling magnetic field, the feeding pressure in the alloy melt before solidification can be enhanced due to the electromagnetic force. Moreover, the melt flow induced by the traveling magnetic field can decrease the temperature gradient. The feeding resistance will be increased because the temperature gradient decrease. So traveling magnetic field has an optimum effect on feeding. © 2015, Foundry Journal Agency. All rights reserved. Source


Qin T.,China Communications Construction Company Ltd. | Ma H.,China Communications Construction Company Ltd. | Chen T.,China Communications Construction Company Ltd. | Tang C.,China Communications Construction Company Ltd. | And 2 more authors.
Jianzhu Cailiao Xuebao/Journal of Building Materials | Year: 2016

To solve the problem that the dry film thickness of the concrete coatings was difficult to be tested nondestructively, ultrasonic coating thickness gauge was adopted to measure the dry film thickness of coating on the surface of concrete in different strength grades. Uncertainty evaluation and quality judgment of the measurement results were conducted. The results show that the degree of reliability of the measurement results could be found by the uncertainty evaluation, which is the important basis for quality judgment whether the measurement result satisfies the requirements or not. The higher the strength grade of concrete is, the smaller the uncertainty of the dry film thickness of concrete coatings is, and vice versa. © 2016, Tongji University. All right reserved. Source


Yuan B.,Tianjin University of Technology and Education | Fang W.,Tianjin University of Technology and Education | Li J.,Tianjin Long March Launch Vehicle Manufacturing Co. | Qu Z.,Tianjin University of Technology and Education | And 2 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2015

The properties of pressure-transmitting medium have a great effect on the formability of sheet metal in sheet flexible-die forming, such as rubber-pad forming and viscous pressure forming (VPF). In this study, viscous pressure bulging (VPB) experiments were used to investigate the effects of viscosity on Al1060 sheet. At the same dome height, the configurations of bulging specimen varied with three different viscosity viscous mediums (1#, 550,000 g/mol; 2#, 700,000 g/mol; and 3#, 900,000 g/mol). The thickness strain distributions of specimen formed by a higher viscosity medium had a relatively uniform distribution. In order to further study the effects of viscosity on VPB, a CDSB-FEM-EFGM program was used to analyze viscous pressure bulging process. The configuration, stress, strain, and wall thickness distributions of bulging specimen were obtained. The numerical analysis results had a good agreement with the experimental ones, which also showed that properties of the viscous medium had a great effect on the formed specimen. The formability of sheet metal can be further improved through increasing the viscosity of viscous medium. © 2015 Springer-Verlag London Source

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