Papers by Author: Y.C. Dai

Abstract: A silicone mould fabrication technique based on vacuum casting was developed and its reproducibility was demonstrated. Orthogonal DOE method was adopted to analyze the effects of vacuum casting process parameters, and the process parameters that had an influence on the quality of the micro-mould cavities were identified and optimized. Micro-casting experiments were carried out using the optimized process parameters and the replicated micro-gears were obtained, these silicone copies were subjected to thorough analysis for dimensional accuracy against the master pattern. The results showed that the fabricated micro-mould was capable of producing functional micro-parts that were able to replicate micro-features, and micro-gears were successfully transferred from the silicone rubber moulds into PU resin pieces under vacuum conditions.

Abstract: As a new fabrication technique based on rapid prototyping, vacuum casting process can be especially used in the stage of products development. In this paper, a self-designed and made silicone mould was used to study process of vacuum casting panel part. ProCAST software was adopted to analyze the melt flowing behavior and effects of processing parameters. The key vacuum casting parameters, such as mould temperature, melt temperature, degree of vacuum and coefficient of heat transfer, on the effects of the filling rate of polymer melt were emphasized to be numerical studied. The results indicate that mould temperature and coefficient of heat transfer have the most important influence on quality of the formed panel.

Abstract: A silicone rubber mould was designed and fabricated to study the forming performance of micro-gear based on vacuum casting technique. The effects of process parameters, such as mould temperature, resin temperature, vacuum deaerating time and curing temperature etc, on vacuum casting quality of micro-gear were investigated. The results indicated that high precision micro-gear can be made in batches by means of vacuum casting of silicone rubber mould, and the vacuum deaerating time has the most important influence on the physical dimension of micro-components.

Abstract: An appropriate finite element analytical model for laser compound forming (LCF) was established with ABAQUS code, and then some key technical issues in the simulations were studied and solved. Numerical simulation of LCF for V-shape was carried out to study bending deformation, residual stress distribution and micro-profile of AISI-1008 steel plate. After the corresponding experiments of LCF, the bending deformation, forming precision as well as the variation of surface integrities were mainly measured and analyzed. The results indicated that anticipated shape of V-plate could be precisely formed, meanwhile distribution of surface residual stress and surface qualities on plate were under good control.

Abstract: Typical specimens of AZ31B Magnesium alloy were processed by single point and continuous laser shock peening (LSP). The selected laser energy was 25 J, spot diameter was 8 mm, peening spacing was 8 mm and peening times were 2. The obtained value of residual compressive stresses were -144.3 MPa and -230 MPa for single and continuous LSP respectively, and the magnitude of residual stress was in direct proportion to the depth of deformation in definite micro-deformation range. The average surface micro-hardness in the laser spot zone was 92.42 HV, which increased by 26% as compared to 73.2 HV of substrate, the depth of hardened layer was about 0.3 mm, and the maximum micro-hardness was about 109.86 HV beneath surface of 0.05~0.075 mm. Large amount of crystal chunks appeared at the crystal grain boundaries and inside the grains, and the average grain size decreased from the untreated 7 μm to the peened 4 μm. The results show that the nucleation of fatigue crack can be retarded and the mechanical properties of AZ31B magnesium alloy sheet can be improved greatly with LSP process.