【作者】 李敏；

【导师】 薛平；

【作者基本信息】 北京化工大学 ， 机械工程， 2020， 硕士

【摘要】 含能材料是国防工业以及航空航天技术不可或缺的重要材料,对其加工方式的研究也一直是各国研究的热点。螺压成型工艺是含能材料成型加工的重要方式,包括物料混同、驱水、压延塑化造粒与螺压成型等几个过程。随着对含能材料的深入研究,高能含能材料已得到较快的发展,而传统螺压机的结构和工艺无法适应含能材料发展的更高要求,在此背景下开展含能材料的螺压安全加工过程模拟仿真研究,以理论指导螺压机结构的正确设计,同时对螺压机内物料温度、成型压力以及物料剪切等关键参数严格控制,以实现药柱的连续稳定生产,具有重要的理论意义和工业应用价值。本论文首先基于沟槽单螺杆挤出塑料成型的理论,建立了含能材料全沟槽单螺杆成型过程的物理模型和数学模型。基于真实改性双基推进剂的物性参数,首次使用Virtual Extrusion Laboratory软件(简称VEL)对单螺杆压伸过程的全螺杆工作段和模具成型进行模拟,得到各项参数沿挤出方向的变化情况,从而为安全压伸工艺过程提供参考。并使用POLYFLOW软件对螺杆均化段和成型模具段进行模拟分析,从整体分布趋势及具体数值上对VEL的结果进行验证和进一步补充。主要研究工作如下:(1)建立含能材料全程直沟槽单螺杆成型过程的三段式理论模型,确定正位移输送的边界条件为固体塞在固体输送段中不被剪断,为沟槽机筒和螺杆的设计优化提供理论支持;(2)利用VEL的挤出机模块和POLYFLOW软件分析真实双基药的单螺杆压伸成型过程的全螺杆工作段,结果显示:螺压过程中压力峰值出现在压缩段末端的螺棱推进侧,而螺棱拖曳侧流道中部的温度最大,主要由剪切生热引起,因此压伸过程中需关注剪切情况以避免过热;(3)使用VEL软件探究加工工艺和螺杆结构对螺压过程的影响,结果表明:螺杆温度、螺杆转速和螺杆压缩比对安全压伸过程有着较大的影响。料温随螺杆温度升高而增大,而压力下降。螺杆转速增大会引起较大的温升,易造成危险,故不宜提高螺杆转速。压缩比增大对建压过程有利且不易引起温升,故可在安全压力范围内适当增大压缩比;(4)使用3D-FEM模块和POLYFLOW软件对料条模具成型流道模拟分析,结果表明成型压力自模具入口处逐渐降低,而剪切热引起的温升较小。并通过3D-FEM模块模拟分析了模具温度和模具收缩角对成型过程的影响,结果表明模具温度和收缩角增大均会使压力降低,不利于物料的压实和黏合,因此模具温度应尽可能低些,收缩角也不宜过大。更多还原

【Abstract】 Energetic materials are indispensable materials for the national defense industry and aerospace technology.And research on their processing methods has always been a hot spot in many countries.The screw extrusion molding process is an important method for the processing of energetic materials,including several processes such as material mixing,water removal,calendering plasticization,granulation and screw extrusion.With the in-depth study of energetic materials,high-energy energetic materials have been developed rapidly,and the structure and process of using traditional extruder cannot meet the higher requirements for the development of energetic materials.In this context,it has important theoretical significance and industrial application value for carrying out simulation research on the screw extrusion processing of energetic materials,using relevant theory to guide the design of the screw extruder and controlling the key parameters such as forming pressure,temperature and shearing of material to achieve the continuous and stable production of the columnar products.In this thesis,the physical model and mathematical model for the full groove single screw extrusion process of energetic materials were established firstly,basing on the theory of grooved single screw extrusion plastic molding.Based on the material properties of the modified double-base propellant,Virtual Extrusion Laboratory software(VEL)was used for the first time to simulate the entire screw working section and mold of the single-screw extrusion process to obtain changes of various parameters along the extrusion direction,which help to provide a reference for the safe extrusion process.Then the POLYFLOW software was used to simulate and analyze the homogenized section of the screw and the mold section.And the results of VEL were verified and further supplemented in terms of the overall distribution trend and specific values.The main research work is as follows:(1)A three-stage theoretical model of the whole straight groove single screw extrusion process of energetic material was established.It was determined that the boundary condition of positive displacement conveying is that the solid plug is not destroyed by shear force in the solid conveying section,which will provide theoretical support for the design and optimization of the barrel and screw.(2)POLYFLOW and the extruder module of VEL were used to analyze the whole screw working section of the single-screw extrusion process of the modified double-base propellant.The results showed that the peak pressure appeared on the front side of the screw arris at the end of the compression section.The temperature in the middle of the channel on the backside of the screw arris is the largest,mainly caused by shear heat generation.Therefore,it is necessary to pay attention to the shearing to avoid overheating during the extrusion process.(3)The influence of processing technology and screw structure on the screw extrusion process was studied by using VEL software.The results showed that screw temperature,screw speed and compression ratio of the screw had a greater influence on the safety extrusion process.The material temperature increased with the increase of screw temperature,while the pressure decreased.Increasing the rotation speed of the screw will cause a large temperature rise,which is likely to cause danger.So it is not appropriate to increase the rotation speed of the screw.The compression ratio of screw can be appropriately increased within the safe pressure range since it is beneficial to the pressure building process and does not cause too much temperature rise for increasing the compression ratio.(4)The 3D-FEM module and POLYFLOW were used to simulate and analyze the mold forming flow path for cylindrical products of the modified double-base propellant.It was found that the forming pressure decreased gradually from the entrance of the mold and the temperature rise caused by shear heating was small.And 3D-FEM module was used to study the influence of the temperature and shrinkage angle of mold on the mold forming process.The simulation results showed that the increase of the temperature and shrinkage angle of mold will reduce the pressure,which is not conducive to the compaction and bonding of materials.Therefore,the mold temperature should be as low as possible,and the shrinkage angle of mold should not be too large.更多还原