铁粉浆料气动喷射增材制造仿真与实验研究
发布时间：2019-01-28 12:53
【摘要】：金属零件增材制造是制造业领域取得的突破性进展,为工业装备中难加工金属构件的制造提供一条快速、柔性、高性能、短周期的技术新途径。结合粉末浆料喷射增材制造的国内外研究现状,及气动喷射沉积的理论和粉末冶金技术成形经验,本文开展了铁粉浆料气动喷射增材制造相关研究。该方法具有设备成本低、材料适用广泛、无需保护气氛、无需高能量束等优点,拓宽了金属增材制造可用材料的范围,在金属增材制造领域具有广泛的应用前景。本研究选用甲基丙烯酰胺凝胶体系,通过优化单体与交联剂的组分比、分散剂质量分数、球磨时间等因素,制备均一、稳定、适用于气动喷射增材制造的铁粉浆料体系。通过浆料流变特性实验可知,铁粉浆料为剪切变稀非牛顿流体,在恒剪切速率下浆料粘度随球磨时间、分散剂WinSperse 4060质量分数以及固相体积分数的增加而增大,在低剪切速率下变化更显著。基于Bird-Carreau模型、Power-Law模型和H-B模型,结合逐步线化法和最小二乘法进行参数拟合,对三种模型拟合结果对比分析,建立铁粉浆料本构方程。通过对喷嘴内部铁粉浆料的流动状态进行合理性假设简化,建立铁粉浆料运动控制方程。基于有限元分析理论,利用POLYFLOW软件对喷嘴内浆料流动状态进行数值仿真分析,得到不同喷射压力、喷嘴结构参数下流体流场分布和喷嘴出口流速。采用网格重构技术划分自由段流体,分析不同喷嘴结构下浆料的挤出胀大效应。搭建了稳定可控的铁粉浆料气动喷射增材制造系统。建立了三种沉积线宽模型,研究喷射压力、平台速度、喷嘴结构参数对成形线宽的影响规律以及线宽模型的选择依据。研究层厚、延时时间、累积层数对增材制造样件成形质量的影响。对喷射成形坯体坍塌、断裂、孔隙等缺陷问题的形成原因进行分析并提出改进方案。通过材料测试和实验结果分析,制定合理的干燥、脱脂、烧结制度,完成坯体强化成形过程,观察不同阶段下坯体微观形貌变化情况,并对增材制造样件烧失比、收缩率以及致密度进行测量分析,最终实现金属铁粉浆料气动喷射增材制造过程。
[Abstract]:Metal parts manufacturing is a breakthrough in the field of manufacturing, which provides a rapid, flexible, high performance and short cycle technology for the manufacturing of metal components in industrial equipment. Based on the research status at home and abroad, the theory of pneumatic jet deposition and the forming experience of powder metallurgy technology, the research on the manufacture of iron powder slurry by pneumatic injection is carried out in this paper. This method has the advantages of low cost of equipment, wide application of materials, no need of protective atmosphere and no high energy beam, etc., which widens the scope of available materials for metal augmentation manufacturing, and has a wide application prospect in the field of metal augmentation manufacturing. In this study, the methacrylamide gel system was used to optimize the composition ratio of monomer to crosslinking agent, the mass fraction of dispersant, the milling time and other factors to prepare homogeneous and stable iron powder slurry system. The rheological properties of the slurry show that the slurry is a shear-thinning non-Newtonian fluid, and the viscosity of the slurry increases with the increase of ball milling time, the mass fraction of dispersant WinSperse 4060 and the volume fraction of solid phase at constant shear rate. The change is more obvious at low shear rate. Based on Bird-Carreau model, Power-Law model and H-B model, combined with stepwise linearization method and least square method, the fitting results of the three models were compared and analyzed, and the constitutive equation of iron powder slurry was established. By simplifying the flow state of iron powder slurry in nozzle, the governing equation of iron powder slurry movement is established. Based on the theory of finite element analysis, the flow state of slurry in nozzle was simulated by POLYFLOW software, and the flow field distribution and nozzle outlet velocity were obtained under different jet pressure and nozzle structure parameters. The mesh reconstruction technique is used to divide the free section fluid, and the extrusion swell effect of the slurry with different nozzle structure is analyzed. A stable and controllable manufacturing system for pneumatic injection of iron powder slurry was set up. Three kinds of deposition linewidth models were established to study the influence of jet pressure, platform velocity and nozzle structure parameters on the forming linewidth and the selection basis of the linewidth model. The effects of layer thickness, delay time and cumulative number of layers on the forming quality of the sample were studied. The causes of defects such as collapse, fracture and porosity of spray forming billet are analyzed and the improvement scheme is put forward. Through material test and experimental result analysis, the reasonable drying, degreasing and sintering system were worked out, the process of strengthening and forming of the billet was completed, the changes of the microstructure of the billet in different stages were observed, and the burning loss ratio of the sample made by adding material was also observed. The shrinkage rate and density were measured and analyzed to realize the process of aero-injection of metal iron powder slurry.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH16
[Abstract]:Metal parts manufacturing is a breakthrough in the field of manufacturing, which provides a rapid, flexible, high performance and short cycle technology for the manufacturing of metal components in industrial equipment. Based on the research status at home and abroad, the theory of pneumatic jet deposition and the forming experience of powder metallurgy technology, the research on the manufacture of iron powder slurry by pneumatic injection is carried out in this paper. This method has the advantages of low cost of equipment, wide application of materials, no need of protective atmosphere and no high energy beam, etc., which widens the scope of available materials for metal augmentation manufacturing, and has a wide application prospect in the field of metal augmentation manufacturing. In this study, the methacrylamide gel system was used to optimize the composition ratio of monomer to crosslinking agent, the mass fraction of dispersant, the milling time and other factors to prepare homogeneous and stable iron powder slurry system. The rheological properties of the slurry show that the slurry is a shear-thinning non-Newtonian fluid, and the viscosity of the slurry increases with the increase of ball milling time, the mass fraction of dispersant WinSperse 4060 and the volume fraction of solid phase at constant shear rate. The change is more obvious at low shear rate. Based on Bird-Carreau model, Power-Law model and H-B model, combined with stepwise linearization method and least square method, the fitting results of the three models were compared and analyzed, and the constitutive equation of iron powder slurry was established. By simplifying the flow state of iron powder slurry in nozzle, the governing equation of iron powder slurry movement is established. Based on the theory of finite element analysis, the flow state of slurry in nozzle was simulated by POLYFLOW software, and the flow field distribution and nozzle outlet velocity were obtained under different jet pressure and nozzle structure parameters. The mesh reconstruction technique is used to divide the free section fluid, and the extrusion swell effect of the slurry with different nozzle structure is analyzed. A stable and controllable manufacturing system for pneumatic injection of iron powder slurry was set up. Three kinds of deposition linewidth models were established to study the influence of jet pressure, platform velocity and nozzle structure parameters on the forming linewidth and the selection basis of the linewidth model. The effects of layer thickness, delay time and cumulative number of layers on the forming quality of the sample were studied. The causes of defects such as collapse, fracture and porosity of spray forming billet are analyzed and the improvement scheme is put forward. Through material test and experimental result analysis, the reasonable drying, degreasing and sintering system were worked out, the process of strengthening and forming of the billet was completed, the changes of the microstructure of the billet in different stages were observed, and the burning loss ratio of the sample made by adding material was also observed. The shrinkage rate and density were measured and analyzed to realize the process of aero-injection of metal iron powder slurry.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH16
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