【作者】 王艳丽；

【导师】 刘建华；

【作者基本信息】 长安大学 ， 机械工程（专业学位）， 2017， 硕士

【摘要】 随着科技发展及生产需求的日益渐增,挤压材朝着大型整体化、尺寸高精度化、复杂多样化等方向发展,生产加工和应用的范围也逐渐扩大,已延伸到了航空航天、装备制造及军事等多个领域。但挤压能耗过大、材料利用率及生产效率都相对较低等成为了目前制约挤压技术发展及应用的内因所在。将摩擦搅拌原理与挤压加工技术相结合而提出的一种新的复合成形技术——摩擦搅拌反挤压工艺,利用摩擦生热原理,不需加热完成挤压加工,必然是一种免加热的新型的节能、环保工艺。因此,本文以摩擦搅拌反挤压制备筒形件为研究对象,采用有限元法对摩擦搅拌反挤压制备筒形件的成形机理进行了系统研究。以ABAQUS软件为平台,结合摩擦搅拌反挤压筒形件的成形特点,建立了既符合实际又兼顾计算精度和效率的摩擦搅拌反挤压筒形件的三维有限元模型。基于所建立的有限元模型,对其成形进行热力耦合数值模拟分析,获得了摩擦搅拌反挤压筒形件成形过程中温度场、应力场、应变场发展、演化的特征。结果表明:摩擦搅拌反挤压与传统反挤压相比,坯料的成形温度大幅度提高,有利于降低坯料的变形抗力,塑性加工变得容易;凸模的轴向载荷明显降低;摩擦搅拌反挤压的等效应变显著增大,因此能获得更大的塑性变形效果;通过金属流动图可以发现,摩擦搅拌反挤压能获得螺旋状的纤维组织,降低筒形件的轴向与周向的性能差异。然后,采用有限元分析法,探讨了成形工艺参数(凸模挤压速度、摩擦系数、凸模转速)对筒形件成形质量的影响,研究发现凸模的挤压速度和转速对其结果影响比较大。在此基础上采用正交实验法,基于多评价指标下的单一指标进行极差分析,确定工艺参数对其成形质量的影响顺序,然后在多评价指标下进行成形质量综合分析,最终获得合理的最优匹配工艺参数。本文对摩擦搅拌反挤压制备筒形件进行分析研究,其成果可丰富挤压成形的工艺理论,提高筒形件产品成形质量及其加工效率,对实际的生产加工具有指导意义。因此,为研发挤压成形新工艺、新技术提供新思路,具有重要科学意义和明确的应用前景。更多还原

【Abstract】 With the ever-increasing technology development and production requirements,extruded profiles are headed in the direction of large scale integration,high precision sizes,complex and diversity.The fields of manufacture and application are developed,and already extended to the fields of aerospace,equip higher manufacturing and military industry.But currently,some problems such as extrusion energy,relative lower material utilization and efficiency become the internal causes that constraint the extrusion technology improvement.Friction air backward extrusion is a novel process to combine friction stir welding technology with extrusion process technology,which is complete extrusion process without heating.Friction stir backward extrusion,therefore,which has characteristics of saving energy,environmental protection,and no heating process.In this paper,based on the Bucket-shape Part by friction stir backward extrusion for the study,its deformation mechanism produced by this process makes theoretical analysis.And then to ABAQUS software as a platform,with forming FEM model for the characteristics of Bucket-shape Part by FSBE,a 3D elastic-plastic FEM model was established using the temp-disp,explicit module of the FEM software ABAQUS.And then,based on the model which had been built,the thermal-mechanical coupling numerical simulation of the forming process was carried out by finite element method,and the basic characteristic of temperature,stress,strain and metal flow pattern during the FSBE process of the Bucket-shape Part.The results show as the follows: The forming temperature of the billet is greatly improved,which is favorable for reducing the deformation resistance of the billet so that it is a facility for the extrusion deformation.Comparing with the traditional extrusion,the extrusion force during FSBE is obviously reduced.The equivalent strain is significantly increasing during FSBE,so this process can obtain larger effect of plastic deformation.Through the metal flow diagram,Spiral fibrous tissue got by FSBE can reduce the performance difference of the Bucket-shape Part in axial and circumferential direction.Then,the finite element method is used to explore the influence of the parameters of forming process(axial speed of the punch,friction coefficient,rotating speed of the punch)on the forming quality of Bucket-shape Part.It is found that the influence of extrusion speed and rotating speed of the punch on the result are relatively significant.On the basis of this,the orthogonal experiment is used to analyze the influence of the process parameters on the forming quality based on the single index under the multi-evaluation index.Then,the comprehensive analysis of the forming quality under the multi-evaluation index is carried out,and finally obtains the reasonably optimal matching process parameters.This paper analysed bucket-shape part prepared by friction stir backward extrusion.The results enrich the theory of extrusion forming technology,improve product quality and machining efficiency.It has guiding significance for actual production and processing.This paper provides a new idea for research and development of extrusion technology,and has important scientific significance and good prospect in application.更多还原