Papers by Author: Jian Lan

Abstract: A new device to measure the material parameters of Baushinger effect from cyclic bending tests, along with its associated test procedure is presented. This new apparatus is designed to get a large range of stains obtained from part geometry directly. The parameter identification is defined by an optimization algorithm with multiple objective iteration function for variance method. The experiment method, design procedure is documented, along with experimental procedure supporting our conclusions.

Abstract: Bipolar plate is the key component of proton exchange membrane (PEM) fuel cell and represents a significant part of the overall cost and the total weight in a fuel cell stack. Many research have been done on the manufacturing methods of bipolar plate, among which stamping is very popular. With the increasing of the channel number and complexity, its dimensional error caused by sprinkback will change a lot, even under the same forming process. And the risk of crack is also different. These all impact the quality of bipolar plate. In order to predict deformation of channels and the plate’s quality, the displacement along X-axis, the strain and stress state, and the displacement along Z-axis are measured. The results show that 1) the risk of crack increases with the increasing of channel number; 2) the springbacks increase with the increasing of channel number; 3) the most dangerous point locates on the right internal fillet of the plate’s last section.

Abstract: Nowadays the immature of the precise synchronizer gear ring processing method have greatly impeded the development of the vehicle business in China. The extrusion process is a very important procedure in making precise synchronizer gear ring, but there is not any introductive and effective research yet to the issue of the optimal processing parameter in precise synchronizer gear ring procession. This research provides several processing parameters in precise synchronizer gear ring procession by means of simulating the processing in DEFORM-2D software and trying it in reality. The result shows that the whole three processing procedures have influence in the result of the gear ring. The second procedure is the most influential, followed by the fist procedure. Adjustment can be effectively conducted on the product of the first procedure by changing the fillet radius of the top die and the bottom die, R1, R2; adjustment can be effectively conducted on the product of the second procedure by changing the fillet radius of the top die and the bottom die and the angle of the upper inclination of the top die,α2. The result of this paper gives an instruction in precise synchronizer gear ring procession.

Abstract: As a key component of proton exchange membrane fuel cell (PEMFC), the bipolar plate’s performance will directly affect the power output and battery life of the fuel cell. The conventional metallic bipolar plate is prone to warp, and has large flatness error with residual stress induced by forming process. This will result in contacting incompletely with membrane electrode assemblies (MEA) and lower fuel cell efficiency. A cylindrical structure of the PEMFC metallic polar plate is proposed to improve its stiffness and to reduce assembling error of the fuel cell. The polar plate features, which were originally designed on a flat surface, are projected onto the cylindrical surface with a certain curvature. Two cylindrical polar plates are welded together to become a bipolar plate. The finite element method is applied to compare the stiffness of the conventional and cylindrical polar & bipolar plates. The cylindrical bipolar plate has better stiffness and anti-warping than the conventional bipolar plate. The feasibility of the cylindrical structure is verified by experiment and provides a new idea for the improvement of the bipolar plate and fuel cell stack.

Abstract: To remove casting porosity and obtain smaller crystal grains, many large forgings need ingots to be upset axially with large ratio of height to diameter (H/D) greater than 3. But the ingots with large H/D are prone to buckling during upsetting process, and have non-uniform internal stress and strain distribution, cracks at barreling and other defects. A new axial upsetting process was proposed to handle these problems. Firstly, the research described deformation inhomogeneity and cracking tendency, and analyzed the causes of defects in the flat anvil upsetting process. Secondly, three two-stage upsetting processes were tried to improve the uneven deformation in the flat anvil upsetting, which applied symmetrical spherical convex die, conical convex die and multi-line sweeping concave die respectively in the first stage, and used flat anvils in the second stage. The effect of the die surfaces on constraining those defects was analyzed. Finally, three three-stage upsetting processes were suggested to take advantages of different die surfaces to stabilize the process. It was observed that the upsetting had better result from using conical convex die and multi-line sweeping concave die in the first stage, conical convex die and flat anvil in the second stage, two flat anvils in the third stage. The new axial upsetting process could improve the quality of the large forgings with more uniform deformation and less barreling.

Abstract: Co-based WC powder and self-fluxing alloy powder Ni60A were sprayed on hot work die steel H13 substrate via high velocity oxygen fuel (HVOF) spray processing, and microstructure and mechanical properties of two types of coatings were investigated. For WC-12Co coating, some pores were observed, while microcracks were only observed in Ni60A coating, which leads to the lower microhardness and abrasion-resistance at either room temperature or high temperature. At the junction of H13 substrate and WC-12Co coating, metallurgical combination was observed. Under the test condition of load 250g and rotating speed 448r/min, the average friction coefficients obtained at 10 are 0.33 and 0.35 respectively; when the test temperature was 500 , the value of two types of coatings increase to 0.56 and 0.63 respectively. Compared with Ni60A coating, The WC-12Co coating had an excellent abrasion-resistance at high temperature; the weight loss was only one-fifth of the Ni60A coating.

Abstract: The Conical Ring with Inner Steps (CRIS) is a typical profile ring, which is hard to be formed by ring rolling. Less-profile-filling and shrinking-drawing are the two main defects formed in the rolling process. Through the study of the rolling formability of CRIS with different ratio of height to diameter with the combination of FEM simulation method and experimental method, the main factors that affect the CRIS rolling formability are determined. The CRIS forging is designed. And the FEM simulation and experimental results show that the design method is reasonable.

Abstract: An effective method was proposed to simulate and control the motion track of guide roller during radial-axial ring rolling in FE simulation. The 3-D finite element model was constructed according to the principle and feature of rolling technology. The rolling process was simulated and analyzed by using dynamic explicit finite element technology. The different rolling processes with different technology parameter were simulated. The width spreads and rolling forces under different parameters are compared and analyzed. The results indicated that high quality ring product could be obtained when rational parameters in radial and axial were assigned.