Guoqun Zhao

Numerical Simulation of Extrusion Process and Die Structure Optimization for a Complex Aluminum Multicavity Wallboard of High-Speed Train

The extrusion die plays a crucial role in the quality control of aluminum alloy profile production. In practice, the extrusion die design mainly depends on the experience and intuition of the die designers. The designed and manufactured dies are usually tested and modified many times before putting into practical extrusion production, and difficult to be guaranteed as optimal ones. In this paper a method of die design based on numerical simulation was proposed in order to optimize the die structure and enhance the level of die design. Firstly, the extrusion process of a large wallboard of high-speed train was simulated by means of HyperXtrude software. It was found that a severe non-uniform velocity distribution emerged in the cross-section of the extrudate and twist deformation occurred, therefore the initial die was not an acceptable one. Then, three times of modifications to the die structure were made to optimize the die structure and improve the product quality. Finally, an optimal die structure with uniform material flow velocity in the cross-section of the die exit was obtained. A sound wallboard extrudate of high-speed train was produced. The die design methods for complex extrusion profiles were summarized and proposed, including the design methods of porthole area of multi-cavity dies, the baffle plate, and the sunken port bridge structure.

Investigation of the Vibration Characteristics of Radial Tires Using Experimental and Numerical Techniques

A 3D finite element model of modal analysis has been established based on MSC.MARC software according to the practical structure of 195/60R14 radial tire. The rebar model is employed to simulate complex multilayer rubber-cord composites. The model considers the geometric non-linearity and the non-linear boundary conditions from tire-rim contact and tire-road contact. The modal test systems are developed for the free suspension tire and the grounding tire. The vibration characteristics of the radial tire are studied numerically and experimentally. Mode shapes (lobes) of the radial vibration are in a strong regularity with the change of the mode order. The first mode shape has two lobes, the second mode shape has three lobes, and so on. Changes of the inflation pressure do not affect the mode shape, but the natural frequency of higher mode shape is sensitive to the change of the inflation pressure. The mode shapes of the grounding tire become asymmetric due to the effect of the vertical load, and the frequency of each mode has a mutation when the vertical load is larger than 3000u2009N. It is in good agreement between the FEA and experimental results of the free suspension tire.

Optimisation design of aluminium radiator extrusion die using response surface method

Abstract The most important way to improve the quality of aluminium extrudates and enhance the life‐time of extrusion dies is to ensure that the material flows through the die land exit with the same velocity. In this paper, an optimisation strategy was developed for an aluminium radiator extrusion die design. A computer aided optimisation model was built based on the Box‐Behnken experimental design, response surface method and particle swarm algorithm. The parameters, such as depth, location of the die aperture, etc. were selected as the design variables. Through a series of simulations and optimisations, an optimal aluminium radiator extrusion die with uniform velocity distribution was obtained. Compared to the original die, the velocity difference across the cross‐section of the extrudate was reduced from 16·5 to 4·4u2005mmu2005s−1. The extrudate was not bent and met the practical requirements.

The Effects of Forming Parameters on Conical Ring Rolling Process

The plastic penetration condition and biting-in condition of a radial conical ring rolling process with a closed die structure on the top and bottom of driven roll, simplified as RCRRCDS, were established. The reasonable value range of mandrel feed rate in rolling process was deduced. A coupled thermomechanical 3D FE model of RCRRCDS process was established. The changing laws of equivalent plastic strain (PEEQ) and temperature distributions with rolling time were investigated. The effects of rings outer radius growth rate and rolls sizes on the uniformities of PEEQ and temperature distributions, average rolling force, and average rolling moment were studied. The results indicate that the PEEQ at the inner layer and outer layer of rolled ring are larger than that at the middle layer of ring; the temperatures at the “obtuse angle zone” of rings cross-section are higher than those at “acute angle zone”; the temperature at the central part of ring is higher than that at the middle part of rings outer surfaces. As the rings outer radius growth rate increases at its reasonable value ranges, the uniformities of PEEQ and temperature distributions increase. Finally, the optimal values of the rings outer radius growth rate and rolls sizes were obtained.

Study on Deflection Performance of Radial Tire by Finite Element Method

In order to improve vehicle safety, the accurate determination of the tires loading behaviour is necessary in the domain of vehicle dynamics. The interaction between the tire and the surface of the road must be understood thoroughly. A 3D finite element model of the tire-road has been built by using MARC software according to the actual construction of the 195/60R14 radial tire. The rebar model of the radial tire is employed to simulate the complex multilayer cord-rubber composites and directly define the cord directions varying with their positions. The geometric nonlinearity due to large deformation, material nonlinearity and the nonlinear boundary conditions from tire–rim contact and tire–road contact are also considered. The relationships between load and the tire deflection, the tire deformation, the contact stress distribution and the distribution of the contact friction force are discussed.

Numerical Simulation and Experimental Study on Parameter Optimization of Cold Flanging Process of Pipe Tee

Keywords: Pipe tee, Prefabricated holes, Cold flanging, Parameter optimization. Abstract. Tee flange molding is a very complex process of change. The affect of the preformed holes is very large in the molding process , so we should calculate according to the parameters and Simulation by Dynaform in order to find the place of torn or wrinkled during the molding process . Then we can not only guarantee that the branch pipes is not wrinkled and torn but also can improve the smoothness and height of the branch pipes by optimizing of the shape of the prefabricated holes.

A Mandrel Feeding Strategy in Conical Ring Rolling Process

A mathematical model for radial conical ring rolling with a closed die structure on the top and bottom of driven roll, simplified as RCRRCDS, was established. The plastic penetration and biting-in conditions in RCRRCDS process were determined. A mandrel feeding strategy for RCRRCDS process was proposed. The mandrel feed rate and its reasonable value range were deduced. The coupled thermal-mechanical FE model of RCRRCDS process was established. The reasonable value range of the mandrel feed rate was verified by using numerical simulation method. The results indicate that the reasonable value range of the mandrel feed rate is feasible, the proposed mandrel feeding strategy can realize a steady RCRRCDS process, and the forming quality of conical ring rolled by using the proposed feeding strategy is better than that of conical ring rolled by using a constant mandrel feed rate.

A Comparative Study of Different Necking Criteria for Numerical and Experimental Prediction of FLCs (vol 20, pg 1036, 2011)

Cunsheng Zhang and Guoqun Zhao, Key Laboratory for LiquidSolid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, 73 Jingshi Road, Jinan 250061, Shandong Province, People s Republic of China; and Lionel Leotoing, Dominique Guines, and Eric Ragneau, Université Européenne de Bretagne, INSA-LGCGM—EA 3913, 20, Avenue des Buttes de Coësmes, 35043 Rennes Cédex, France. Contact e-mails: zhangcs@ sdu.edu.cn and zhaogq@sdu.edu.cn. JMEPEG (2012) 21:120 ASM International DOI: 10.1007/s11665-010-9784-

Characteristic of rapid heating cycle moulding and warpage analysis of products

Abstract Rapid heating cycle moulding (RHCM) injection method can be used to solve many defects on the surface of the products produced by conventional injection method, such as weld mark, flow mark and so on. In this paper, the process of RHCM technology was presented. By comparing the new technology with the conventional injection method and the products produced by them, the advantages of RHCM technology were demonstrated. However, large warpage of the products was considered as the main defects of this technology. The reasons that caused the warpage of the products were analysed. Through finite element simulation and engineering experiment, the layout of the cold runners in the RHCM mould was optimised in order to decrease the warpage of the part. The results of the experiments and the finite element simulation were very close, proving that the simulation carried out in the paper was right.