气辅成型过程气体穿透行为的MPI三维模拟及实验

采用MPI/GAS-3D模块分析了不同延迟时间和气体压力条件下的气体穿透效果,并与该工艺条件下实验测定的高密度聚乙烯(HDPE)气体辅助注射成型(GAIM)制品的气体穿透长度(GPL)及残余壁厚(RWT)进行比较,探讨了气辅成型中延迟时间和气体压力等关键工艺参数对制品气体穿透长度和残余壁厚的影响,利用实验数据分析了气体穿透长度与残余壁厚之间的定性关系。     

Cavitation during tensile drawing of annealed high density polyethylene

Annealing of semicrystalline polymers usually leads to refinement and thickening of crystals. It appears that also cavitation is affected during tensile drawing. In the uniaxially drawn high density polyethylene massive cavitation was detected by X-ray scattering in the samples previously annealed at 125 °C. The number of voids depends on the annealing time, while their size and orientation depends on the local strain. Cavitation resulted in 30% increase in volume for the annealed samples, strained to 4-5. Cavitation and volume increase were not observed for small and intermediate strains if polyethylene samples were not annealed. The decrease in the drawing rate results in the reduction of cavitation and void stability - at the low strain rate voids were detected during tensile drawing, though they disappeared after unloading the sample.     

Automatic layout design of plastic injection mould cooling system

This research extends our previous investigation of the automation of the preliminary design stage to the layout design stage of the cooling system design process. While the functional aspects of the cooling system are considered during the preliminary design stage, the layout design stage addresses both the functionality and manufacturability of the design. A graph structure is devised to capture a given preliminary design and a graph traversal algorithm is developed to generate candidate cooling circuits from the graph structure. Heuristic search is employed to develop the cooling circuits into the layout designs by generation of tentative manufacturing plans. A framework for fuzzy evaluation of the layout designs is developed to rate the various design alternatives generated. An experimental system is implemented to verify the feasibility of the approach, and examples generated from the system are presented to illustrate the major steps of the automatic design process.     

悬臂型塑料卡扣的设计

针对悬臂型塑料卡扣在使用过程中易出现的卡入困难、脱扣、变形、断裂等结构问题,结合笔者多年的设计和加工经验,给出了卡扣弹性、拆装力度、强度等结构要素的设计和加工注意事项。     

聚丙烯塑料造粒色差原因和改进

从原材料、设备、加工工艺、环境等因素,兼顾树脂和着色剂加工的性能,分析和探讨了聚丙烯塑料造粒色差产生的原因,并提出改进措施.     

Particle impact theory including surface asperity deformation and recovery

A new particle impact theory was proposed, which incorporated plastic deformation and elastic recovery of surface asperities into the overall energy balance of the impact process. Asperity heights were assumed to follow a truncated Gaussian distribution. The energy transfer associated with the deformation and recovery of asperities was derived based on the previous theoretical treatments of thermal contact resistance. It was found that even nanometer level roughness had significant effects on the rebound of micron size particles. The energy loss thus caused could explain the mysterious strong power–law dependence on particle size of critical velocity. Measurements of Wall et al. were compared with the theory. Good agreement had been reached between the theory and experiments for both coefficients of restitution and particle size dependence of critical velocity.     

高分子材料嵌铸成型工艺研究

高分子材料的嵌铸成型是一种较独特的成型工艺方法,被较多使用的是用透明塑料包封各种动植物标本及纪念品等,可用于制作人工琥珀。本文全面介绍了嵌铸工艺的原理及实施方法。     

堆石体灌水法密度试验薄膜探讨

目前,我国堆石坝技术已较为成熟,堆石体是筑坝和围堰结构的重要组成部分,而碾压方式下堆石体的干密度是影响坝体变形的主要因素,也是大坝填筑质量的主要控制指标之一。现场常采用挖坑灌水法来测定其填筑的密实度,挖坑灌水法原理简单,操作简便,但要测定准确却非常困难,且薄膜厚度对测定结果也存在一定影响,现介绍某工程采用挖坑灌水法测定堆石体填筑密度过程中,采用两种厚度薄膜进行试验比对的工程经验。     

密度和地膜覆盖对烟田冠层生理特性和土壤水分利用效率的影响

采用田间试验研究了种植密度和地膜覆盖对烟田冠层生理特性和土壤水分利用效率的影响。结果表明,随种植密度的增加,烤烟叶面积系数、烟田相对湿度、叶片气孔导度增大,蒸腾速率增强,胞间CO2浓度升高,而光合有效辐射量减小,叶片温度降低,净光合速率下降,烟田水分蒸散量增加,0～60cm土壤的贮水量下降,水分亏缺严重。在烟株生长前期地膜覆盖具有明显的蓄水保墒效果,但到中、后期这种作用很小。从不同处理烟叶经济性状和烟田水分利用效率综合分析,烤烟适宜的种植密度为16500～19500株/hm2。     

Pyrolysis–gasification of post-consumer municipal solid plastic waste for hydrogen production

Post-consumer plastic waste derived from municipal solid waste was investigated using a two-stage, catalytic steam pyrolysis–gasification process for the production of hydrogen. The three important process parameters of catalyst:plastic ratio, gasification temperature and water injection rate were investigated. Temperature-programmed oxidation (TPO) and scanning electron microscopy (SEM) methods were used to analyse the reacted catalysts. The results showed that there was little influence of catalyst:plastic ratio between the range 0.5 and 2.0 (g/g) on the mass balance and gas composition for the pyrolysis–gasification of waste plastics; this might be due to the effective catalytic activity of the Ni–Mg–Al catalyst. However, increasing the gasification temperature and the water injection rate resulted in an increase of total gas yield and hydrogen production. The coke formation on the catalyst was reduced with increasing use of catalyst; however, a maximum coke formation (9.6 wt.%) was obtained at the gasification temperature of 700 °C when the influence of gasification temperature was investigated. The maximum coke formation was obtained at the water injection rate of 4.74 g h⁻¹, and a more reactive form of coke seemed to be formed on the catalyst with an increase of the water injection rate, according to the TPO experiments.