Papers by Author: Hai Peng Li

Abstract: A methodology to design optimal forming process and relative parameters of the automobile front panel reinforcing plate, using the numerical simulation technology of forming sheet metal, is investigated. The digital model of the complex automobile part is established by computer aided design software. Dynaform software is used to simulate its forming process to acquire the feasible process parameters affecting its formability. Forming limit diagram and thickness distribution diagram are used to evaluate the simulation results of different process schemes. The orthogonal experiment method is adopted to design and simulate the process parameters to find out the optimum values for die design. The reasonable process design and optimum values of fillet radius of female die, friction coefficient and blank-holder force are obtained, which can reduce the tendencies of wrinkling, crackling and thickness reduction, and achieve sufficient plastic deformation of blank.

Abstract: The forming process of automobile trunk side panel was investigated, using numerical simulation technology, to acquire the feasible process parameters and improve the formability of the product. With the technology, the manufacturability working procedures and drawing process parameters of the product were analyzed, calculated and simulated to achieve optimum formability characteristics. The method effectively lowers the probability of springback, wrinkling and thickness reduction, and shortens design cycle and cost. Based on the simulation results including forming limit diagram and thickness distribution diagram, the feasible process parameters are determined.

Abstract: This paper presents a methodology to design optimal forming process parameters of the sleeper fixed reinforcing plate based on the use of computer aided engineering (CAE) technology. The methodology uses Unigraphics software to establish the numerical model and DYNAFORM software to simulate its sheet forming process to determine the feasible process parameters affecting its manufacturability, including whether the mould requires the binder, binder force, friction coefficient, and die fillet radius. The forming limit diagram and the thickness distribution diagram are selected to appraise and analyze the forming results. The orthogonal experiment method is adopted to simulate the design parameters to find out the optimum values for mould design.

Abstract: Multi-walled carbon nanotubes (CNTs)/Al in-situ composite powders over Al as catalyst carrier had been synthesized successfully using transition metal Ni by chemical vapor deposition. CNTs were mainly characterized by transmission electron microscopy. It was found that reaction temperature had great influences on the structures of carbon products obtained. Detailed discussions according to the structures of CNTs at different reaction temperatures were given. A deduced model for explaining the growth mechanism of CNTs governed by temperature was developed.

Abstract: Based on the analysis of primal process and structure of gray iron brake pad failing early, hydrodynamic software Flow-3D was used to simulate the defect distribution and temperature fields of different improved technology schemes. According to simulation results, the merits and faults of all schemes were investigated and the feasible casting system was determined. The results showed that uniform temperature distribution could be achieved and potential defects mainly distributed in gate riser or nonworking surface when adopting the casting system with single ingate, which gave brake pad better service performance.

Abstract: Carbon nanotubes (CNTs) over hydroxyapatite (HA) as catalyst carrier were synthesized successfully using transition metal by chemical vapor deposition (CVD). The influences of catalyst types on the synthesis of CNTs were investigated when using Fe, Co and Ni as transition metal catalyst respectively. The results showed that CNTs synthesized by Fe catalyst normally possess more ideal morphology and higher crystallinity than those by the other two. But the yield rates of CNTs synthesized by CVD were in the order of Ni>Fe>Co. On the basis of this, HA matrix composites reinforced by CNTs in-situ were prepared and their mechanical properties were studied preliminarily. This study supplies valuable information for controlling the property of CNTs/HA composite by the selection of catalyst.

Abstract: Thermodynamics and dynamics of Mg3Zn6Y quasicrystals in solidification process were detailedly studied in this paper. The free energy, nucleation rate and nucleation energy were deduced and calculated. It shows that the driving force and nucleation rate gradually increase with the decreased temperature. The further studies show that the nucleation energy increase gradually with the decreased liquidus temperature. And it is apt to quasicrystal nucleation by increasing the cooling rate in a proper temperature range.

Abstract: Using Al powder as thickening agent and CaCO3 powder as foaming agent, Al foams with above 85% porosity, pore sizes between 1mm and 4mm and relatively uniform pore structure have been fabricated by melt foaming method at different foaming temperatures. Meanwhile, the paper researched the effect of foaming temperature on foaming effect and analyzed the defects in Al foams. At last, compression test were taken in order to investigate the mechanical properties of aluminum foams. The results showed that pore structure, pore distribution and compression properties of Al foams fabricated at 720°C were much better than that fabricated at lower temperature.

Abstract: The paper studied various morphologies of the quasicrystal phase in Mg-Zn-Y alloys caused by different cooling rates. The cooling rates were reached through five kinds of cooling media. The cooling curves were monitored by multichannel data acquisition cards. A further heat treatment was made to study quasicrystal growth behavior. The results showed that, with the decrease of cooling rate, the quasicrystal morphology changed and its size became larger. Moreover, a planar quasicrystal morphology evolution schematic diagram during quasicrystal growth process was observed for the first time.

Abstract: During casting process design, CAD/CAE technology can play important role to avoid macroscopic irregularity, internal defect and assure casting performance. Based on the casting process analysis and gating system design, the numerical simulation of gray iron butterfly valve was done by hydrodynamic software Flow-3D to obtain its optimal process scheme. According to the simulation results including flow field, temperature field and defect distribution, the merits and faults of designed schemes were investigated and then the feasible gating system was proposed. The results showed that, compared with top or intermediate casting, when adopting bottom casting, steady flow of molten metal and reasonable temperature distribution could be achieved. And workpiece defects mainly distributed in riser. The predicted results are in good agreement with practical ones.