激光近净成形过程中的热力学分析与优化

发布时间：2018-03-18 17:05

本文选题：激光近净成形　切入点：数值分析　出处：《合肥工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：激光近净成形技术是一种以激光为能量源,采用预铺粉或同轴送粉的送料方式,在基体上熔覆材料粉末从而生成立体工件的新型制造技术。该技术能对传统工业难以制造的复杂金属零件进行直接成形,其快热快冷的加工特性可以改进工件的物理性质,因而普遍运用于航空航天、汽车制造、模型开发等领域。但该技术发展尚不充分、很多基础性研究尚待完善,工件成形时常常出现边缘凸起、断裂以及脱离基板等问题,严重影响了成形精度和成形质量。因此本文从激光近净成形技术的基础研究出发,采用数值模拟方法对薄壁工件的温度场、速度场及应力场进行分析。本文基于控制容积法,结合数值传热学、流体力学的相关理论,在Matlab软件中建立了激光近净成形过程的温度-速度场耦合模型。利用模型计算工件在任意时刻的温度分布和熔池形貌,重点分析了多层工件的熔池形貌衍变过程。随后通过计算成形过程中的有效送粉量,预测了薄壁工件的成形高度,并解释了工件边缘凸起产生的原因。最后建立CCD成像系统拍摄熔池形貌,并利用成像实验验证了数值模型的正确性。本文基于有限元法,在ANSYS热力学分析软件中,采用间接耦合的方法建立了薄壁工件的温度-应力场耦合模型。利用生死单元技术模拟了热源的移动和材料的添加过程。文中重点探究了工件的等效应力分布、各应力分量的分布以及关键路径上的应力分布,从而解释了工件断裂以及脱离基板的原因。
[Abstract]:Laser near net forming technology is a kind of laser energy source, the feeding method of pre powder or coaxial powder, a new manufacturing technology on the base of cladding material powder to generate three-dimensional workpieces. The technology of traditional industries is difficult to manufacture complex metal parts for direct forming, can improve the physical properties of the workpiece the processing characteristics of the rapid heating and rapid cooling of the thus widely used in aerospace, automobile manufacturing, model development and other fields. But the technology development is not sufficient, a lot of basic research needs to be improved, workpiece forming often convex edge, and the substrate from the fracture problem, seriously affecting the forming precision and forming quality. Therefore this article embarks from the basic research of near net forming technology of laser, using the method of numerical simulation of temperature field of thin-walled workpiece, analyzes the velocity field and stress. In this paper, the control volume method based on node Number value of heat transfer, the theory of fluid mechanics, in the Matlab software, the coupling model of near net forming process of laser temperature velocity field is established. The temperature distribution and the weld shape calculation of workpiece at any time by using the model, analyzes the weld shape evolution of multilayer workpiece. By calculating the effective amount of powder forming subsequently send process, predict the forming height of thin-walled workpiece, and explains the workpiece edge from the bulge. A CCD imaging system shooting pool morphology and verify the correctness of the numerical model by using the imaging experiment. Based on the finite element method in ANSYS software, the thermodynamic analysis of thin-walled workpiece temperature should be the coupling model of stress field is established using indirect coupling method. The process was simulated by adding a moving heat source and material life and death element technology. This paper focuses on the equivalent stress of the workpiece The distribution of the distribution of the stress components and the stress distribution on the critical path, which explains the reasons for the fracture of the workpiece and the separation of the substrate.

【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN249;O414.1

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