Papers by Author: Qing Song Wei

Abstract: Conventional drip irrigation systems are working under constant working pressure, but the core component emitter is prone to clogging. Round-flow emitter is selected as the research object. Computational fluid dynamics software FLUENT 6.3 is applied to simulate the hydraulic performance of the round-flow emitter under the condition of vibration pressure. Vibration modes are selected as the sine waveform, triangular waveform and rectangle waveform. Three vibration parameters such as basic pressure, vibration period and vibration amplitude are taken as the factors to design the orthogonal experiment. Simulation results show that, water fluctuation and energy dissipation of round-flow emitter in vibration mode are better than that of constant pressure. The combination of basic hydraulic pressure 8m, vibration period 72s, vibration amplitude 6m is the optimal vibration parameters. The research of this paper provides a certain reference for selecting the vibration parameters of the vibration mode.

Abstract: Ti6Al4V component has been formed by hot isostatic pressing (HIPping) using internal graphite mould with Ni isolation layer. The shape of the graphite had no deformation after HIPping. The Ni isolation layer with a thickness of approximately 5μm on graphite before HIPping was diffused into the dense Ti6Al4V component surface and formed a uniform, compact and crack free layer with a thickness of approximately 100μm after HIPping. The Ni diffusion layer is not damaged after removing the graphite mould by unpolluted sandblasting. The interface topography and the elements diffusion have been assessed and it is found that the non-machined surface of Ti6Al4V component was improved by using graphite mould than those used mild steel. The roughness of non-machined surface after removing the graphite mould by sandblasting is Ra=1.6μm, and the roughness of non-machined surface after removing the mild steel by acid pickling is Ra=10.8μm. It is concluded that graphite mould could be used for the HIPping process to produce complex-shaped components.

Abstract: Selective Laser Sintering (SLS) has been successfully and broadly applied in biomedical engineering to fabricated biomedical part. And the porosity and microstructure of part can be controlled by main sintered parameters. This research focused aliphatic Polycarbonate (PC) sintered with SLS. According to the orthogonal experiment, the effect of laser power energy and interaction between main sintered parameters on porosity has been studied. Then the micro structure and mechanical properties of specimens sintered with the best optimal parameters have been analyzed.

Abstract: Near-net-shaping hot isostatic pressing (NNS-HIP) method was used for once-forming complex monolithic Ti6Al4V alloy bladed disks manufacturing. The complex monolithic bladed disks were formed successfully in a near-net-shape manner using the proposed HIP mold scheme in this study. The results showed that there were fine and homogeneous strip α+β phases and no obvious pores or cracks were detected. A "layered" phenomenon was observed in as-built part microstructure. The tensile strength value of specimens from the NNS-HIP bladed disks in the same furnace reached 900MPa, which was higher than the values of parts manufactured using casting and forging processes. The fracture morphology analysis showed that the sample had a ductile fracture. This study provides a reference to the NNS-HIP for the bladed disk parts manufacturing.

Abstract: Although pressure compensating emitters (PCE) have many advantages, they are difficult to develop and very costly. Traditional PCE are composed of emitter structures and compensating diaphragms. Their manufacture is very difficult and time-consuming. In this paper, we invented novel PCE with variable flow channels, which are designed as integrated structures with pressure compensating barriers, and manufactured three of them with different structures based on the rapid prototyping/rapid tooling technology. The pressure-flow test showed their behavior indexes were 0.009, 0.008 and 0.011, respectively, indicating this type of novel PCE have remarkable compensating effect.

Abstract: To investigate the influence of pressure on densification behavior of metal powder under hot isostatic pressing (HIP), the consolidation of Ti6Al4V powder at various applied pressures during HIP processes were investigated by finite element method in this paper. The plasticity and creep phenomenon of the compact under high temperature and pressure were described by the viscoplastic Perzyna model, which integrated with a modified yield criterion for porous metal materials. The thermo-mechanical coupling analysis was carried out by the finite element code MSC.Marc. The calculated results show non-uniform density distributions for the compact, but this phenomenon decreases as increasing the applied pressure. The densification rate is significantly influenced by applied pressure. The consolidation mechanisms for powder compact were also discussed.

Abstract: Selective Laser Sintering could manufacture high complex metal parts in short time but with high porosity and low strength. The components from Cold Isostatic Pressing have excellent performance with uniform organizational structure, high size precision, and high density. It, however, could not form high complex parts because of the difficulties of bag manufacture. So it will be a good method to combine Selective Laser Sintering and Cold Isostatic Pressing to make complicated metal parts. In this paper, the specimens of stainless steel were made by the combined Selective Laser Sintering and Cold Isostatic Pressing forming route. And the simulation of Cold Isostatic Pressing was carried out by finite element method and Drucker-Prager-Cap constitutive model in ABAQUS/Explicit computer program. The property of metal powder was measured by experiments. The effects of bag on Cold Isostatic Pressing have been discussed. It is different from the Cold Isostatic Pressing of metal powder that the bag has little influence on both shape and size of the specimen. The results of simulation show a good agreement between the experimental results and the calculated results. The simulation can give a useful direction to dimension and shape designs of the combined forming of Selective Laser Sintering and Cold Isostatic Pressing.