Papers by Author: Guang Chun Wang

Abstract: After modifying the Wahime/Bay friction model, a new friction model suitable for micro-forming process without lubrication is established. In this model, it is shows that the friction coefficient is a function of strain hardening exponent, the normal pressure and the initial yield stress of material. Based on the experimental data, the micro-upsetting process is simulated using the proposed friction model. The simulation results are used to investigate the size effect on the dry friction behavior. It is found that the Coulomb’s friction coefficient is dropping with miniaturization of specimens when the amount of reduction is not too large.

Abstract: The microstructure revolution of a spur gear shaft during hot forging was numerically simulated with FEM using Yada Model. The grain size distribution of the gear shaft after hot forged using initial billets with different dimensions was obtained through microstructure simulation and relative metallographic experiment show a good agreement with the simulation result. Effect laws of different forging parameters including the initial forging temperature and the punch speed, on grain size of the gear shaft after forged were given. A preforming process was proposed and the microstructure simulation shows that the preforming process can significantly improve the grain size refinement and distribution uniformity of the gear shaft by hot forging.

Abstract: Improving the extrusion die wear condition was significant to increase the products dimensional accuracy and die life time. In this paper, the hot extrusion process of spur-gear shaft is analyzed by finite element method, and the die wear distributions of different blank shapes and die structures are calculated using the modified Archard model considering the effect of die temperature. According to the results, using the preformed blank shape and floating die could reduce the die wear obviously.

Abstract: Hot forging processes of a spur gear shaft with three billet sizes are simulated using FEM. The billet with size of φ36*60 has the best formability in hot forging the spur gear shaft. The effects of the initial billet temperature and the friction coefficient on the hot forging formability of the spur gear shaft are obtained respectively through simulation. Hot forging experiments are carried out and experimental results show good agreement with those in simulation. At last, the reasonable hot forging parameters of the spur gear shaft for manufacturing engineering are suggested as follows: billet size of φ36*60, billet initial temperature of 1050°C and friction coefficient of 0.3.

Abstract: In micro-manufacture field, micro-forming is paid much attention due to its efficiency for mass production. However, owing to the particularity of deformation, mass researches for specialized micro-forming processes to direct the industrial production are of great urgency. As a similar process with the micro-forming, the forming property of micro-feature forming in coining process was investigated by the experimental research and numerical analysis. Firstly, utilizing the workpieces with different thicknesses and micro-feature sizes, the coining processes were numerically simulated to study the forming property of micro-feature. The height of micro-feature was selected as the evaluation criteria for the deformation behavior. Then, the pure copper specimens with different thicknesses were coined experimentally, using a die with a micro-hole by the universal testing machine to verify the simulation results. Finally, a modified scheme was successful to be proposed which could improve the manufacturability of the processes. The research results could provide technical references for manufacturing micro-parts and those with micro-features.

Abstract: There are many factors, such as the laser and geometrical parameters, which influence greatly on the laser bending process. So it is of great importance to determine these variables properly. Considering the relationship of material properties and temperature, a 3-D thermal-mechanical finite element analysis model for laser micro-bending of stainless steel foil is developed based on the software MSC.Marc, and the laser micro-bending process of 0.1mm thick stainless steel foil is implemented. The finite element method simulation process is integrated with the optimization software package iSIGHT through secondary development. The objective function is to realize the maximum bending angle after single laser scan, and laser power, beam diameter and scanning velocity are regarded as the design variables. The forming process is optimized by using genetic algorithm. The optimal result shows the bending angle can be got to the maximum 1.0332°when the laser power, beam diameter and scanning velocity are 32W, 0.17mm and 132mm/s respectively. The experiment results are in good agreement with optimal results.