【作者】 朱海；

【导师】 郭艳玲；

【作者基本信息】 东北林业大学 ， 机械设计及理论， 2013， 博士

【摘要】 摩擦焊作为一种优质、高效、节能和无污染的先进焊接方法,已被众多发达国家作为一项技术政策而大力推广应用,因此,国内外对这项技术都开展了广泛的基础研究和应用研究。本文在总结国内外摩擦焊数值模拟研究成果的基础上,以直升机起落架机轮轴材料为研究对象,利用有限元理论和数值模拟技术建立该材料的连续驱动摩擦焊有限元数值模拟计算模型,实现连续驱动摩擦焊过程的数值模拟,开展工艺参数对决定焊接质量的各物理参量场影响规律的研究,利用计算机数值模拟的方法代替大量的实际焊接工艺试验,得到合适的焊接工艺参数范围,再结合少量的焊接工艺实验,得到优化的焊接工艺。本文首先根据摩擦焊是一个伴随有摩擦加热,高温形变及连续冷却的热力循环过程的特征,在分析传热学和塑性力学有关理论的基础上,建立连续驱动摩擦焊接过程的温度场和应力应变场的数学模型,结合金属材料塑性成形过程的刚-粘塑性理论,综合考虑工件的尺寸形状、变热物性参数、摩擦系数等因素的影响,采用刚-粘塑性有限元法和ABAQUS有限元软件建立了高强合金钢摩擦焊接过程的二维轴对称、热力耦合有限元计算模型。利用该模型计算了35Ni4Cr2MoA高强钢连续驱动摩擦焊接过程的温度场、应力应变场和轴向缩短量,并针对三个焊接阶段对计算结果进行了分析,通过相关实验验证了模型的实用性；利用有限元模型进行了焊接接头塑性区的形成、扩展和金属流动规律的数值模拟研究,发现,对于空心轴件高温塑性区首先在外径处产生,随后在内径处产生,最后才在摩擦面的中间处产生,而且内外径处的高温塑性区宽度大于中间区域。计算和分析了影响摩擦焊接质量的关键工艺参数转速、摩擦压力对焊接接头温度场、摩擦扭矩和变形速度的影响规律,得到了35Ni4Cr2MoA高强钢连续驱动摩擦焊的合适的转速范围和稳定摩擦扭矩的合适区间,得出了合适的摩擦变形速度区间与合适的摩擦扭矩区间是重合的结论；计算和分析了各焊接工艺参数对轴向缩短量的影响规律,计算了不同摩擦压力和摩擦时间下的接头形状,并进行了对比分析；计算和分析了摩擦压力和时间对接头温度场的影响规律；为开展摩擦焊基础研究和工艺研究提供了依据。最后根据焊接工艺参数对摩擦焊接过程的影响规律的研究结果,制定了35Ni4Cr2MoA高强钢的摩擦焊接正交实验计划,并进行了焊接实验；对焊后接头进行了金相组织,力学性能检验,通过极差分析,得出了摩擦压力和顶锻压力对冲击韧性影响显著；采用回归正交优化法建立了轴向缩短量与摩擦焊工艺参数的数学模型,可以实现参数的预测和控制。通过综合分析,得出了优化的连续驱动摩擦焊工艺参数。更多还原

【Abstract】 Friction welding technology, which is a kind of methods of pollution-free advanced welding with high quality, and high efficiency, has been applied and developed in many countries as a vigorously promoted technology. Therefore, the basic research and applied research of the technology are widely carried out at home and abroad. This article summarizes many researches on friction welding numerical simulation at home and abroad. The gear machine shaft of helicopter landing was as the research material. The finite element numerical simulation model of friction welding was established using the finite element theory and numerical simulation technology. The numerical simulation was carried out by continuously driving friction welding process. The effects of technological parameter on various physical parameters were studied for determining the quality of welding field. We got the appropriate welding process parameters when the method of numerical simulation by computer was used to be instead of a large number of actual welding process tests. The optimal welding process was got, combined with a small amount of welding technology experiment.The friction welding is a thermal cycle process, which has a characteristic of friction heat, deformation at high temperature and the continuous cooling. Based on the analysis of heat conduction and plastic mechanics and the related theory, the mathematical models of temperature field and stress strain field were established with a continuously driving friction welding process.At metal plastic forming process, the factors of the size of the workpiece shape, variable thermal physical parameters and friction coefficients were considered, combined with large deformation-thermal viscoplastic theory. The element calculation models of thermodynamic coupling finite and two-dimensional axisymmetric were established at the friction welding process of high strength alloy steel, using the rigid-plastic finite element method and finite element software ABAQUS.By using the model, the temperature field with stress and strain and the axial shortening amount was to calculate at the high strength steel of35Ni4Cr2MoA in the process of continuously driving friction welding. The calculation results in view of the three stages of welding are analyzed, through the relevant experiment to verify the practicability of the model. The numerical simulation of flow law of metal and expansion and formation of plastic zone of welding joint are studied by using the finite element models. We found that the ring high temperature zone is first in outer diameter, and then at the inner diameter, finally on the friction surface. The width of the plastic zone of high temperature at outside diameter is larger than that at the middle area. The effects of the key technical parameters of the friction welding quality (rotate speed and friction pressure) were calculated and analyzed on Influence law of the friction torque and speed of deformation and weld temperature field. Suitable range of stable friction torque and speed range of drive friction welding are fit for35Ni4Cr2MoA. It is conclusion that the appropriate range of friction and deformation velocity was coincided with the range of appropriate friction torque.The effects of the welding process parameters on amount of the axial shortening were calculated and analyzed. The wilding Joint shapes were calculated and compared under different friction pressure and time. We analyzed the effects of the friction pressure and time on coupling temperature field for providing basic research of the friction welding.According to the influence law of welding process parameters on friction welding process, the orthogonal experimental program for high strength steel of35Ni4Cr2MoA was made for welding test. The welding joint was analyzed through joint microstructure and mechanical properties test. There is obviously influence of friction pressure and upset pressure on impact toughness. Through comprehensive analysis, it is concluded that friction welding technology parameters were derived the optimization continuously.更多还原