转子偏心下环模制粒机的振动分析与结构优化

环模制粒机因其高效率、低能耗等优点广泛应用于饲料、生物质能源等领域,而目前的环模制粒机振动剧烈,尤其是有转子偏心时环模会受到强烈的振动冲击,严重减小环模的使用寿命。因此对转子偏心下环模制粒机的振动特性进行了分析并对其主要结构进行优化。基于粉体挤压成型规律以及环模与压辊挤压成型规律,建立了考虑压辊表面正向静摩擦力作用下的环模与压辊之间准确的相互作用力模型,并对压辊与环模有相对位移时其相互作用力的变化规律进行建模和分析。基于多体动力学软件建立了转子偏心下环模制粒机的动力学仿真模型,分析转轴、主轴以及挤压力的振动特性,并对主轴、支撑架以及转轴轴承的结构或位置参数进行分析和优化。研究结果表明：压辊与环模之间相互作用力与相对位移之间近似成线性关系;主轴上转轴支撑段直径应大于直径;主轴直径增大有利于转轴振动幅值减小但是会增大挤压力幅值,将压辊底座通过柔性杆与主轴连接可在减小转轴振动的同时大幅减小挤压力的振动;支撑架的径向刚度应大于1×10^7N/m,弯矩刚度应大于1×10^5N·m/deg;转轴轴承间距存在与轴承刚度相关的最优值,且最优轴承间距会随着轴承刚度增大而减小。

Deformation and densification behavior of discrete media filled thin-walled tubes during forward extrusion

Discrete media filled thin-walled hollow profiles are frequently used as integer structures for special purpose, e.g., in certain materials processing or architectural components. To understand the deformation of such composite structures which is a complicate mechanics process, involving coupled elastic-plastic deformation of dense metal, compaction of particle and interaction between the filler and the wall, the forward extrusion of Al 6061 tubes filled with various particles was studied. The analysis regarding internal volume variation of round tubes during forward extrusion indicates that with the diameter reduction the volume of tubes decreases commonly. The cavity shrinkage brings about triaxial pressure on the filler, resulted in compaction and densification of it. Loose powders filling leads to higher extrusion load. Due to dissimilar migration behaviors of the particles, the load?stroke curves of the tubes filled with fine powders and coarse balls are quite different. Small Lankford value of the tube wall material leads to higher hydrostatic pressure of the filler and then more powders are compacted.

石墨烯增强铝基复合导线制备及其表征

通常铝石墨烯复合材料会生成较多的Al_(4)C_(3),使其电导率相对于纯铝下降较大。为减少Al_(4)C_(3)生成,采用粉体连续挤压法制备Al-Gr(石墨烯)复合材料。研究表明:采用粉体连续挤压法制备Al-Gr复合材料,Al与Gr在界面上生成的Al_(4)C_(3)相极少,抗拉强度提高,随着石墨烯含量的增加而增大,电导率随石墨烯含量增加而降低,但Al-0.5%Gr复合杆材电导率仍保持为62.28%IACS,相比基体纯铝仅下降2.1%,而抗拉强度提高了16.3%。