共查询到18条相似文献,搜索用时 62 毫秒
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对射频等离子体球化中钼粉颗粒的加热过程进行研究可以为优化等离子体制备球形钼粉的工艺过程提供参考。采用了数值模拟的方法研究了线圈电流频率、粉枪位置及送粉速率等参数对钼粉颗粒在射频等离子体中的运动轨迹及加热过程的影响效应。结果表明:线圈电流频率较低时,等离子体炬轴线附近的温度更高,钼粉颗粒在等离子体中运动时能够达到的温度也更高;改变粉枪位置仅对粒径较小颗粒的运动和加热有较大的影响;降低送粉速率可以提高颗粒从等离子体中获得的能量,从而在一定程度上提升钼粉的球化率。 相似文献
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等离子喷涂过程中液态颗粒平化过程数值模拟 总被引:1,自引:0,他引:1
利用有限元方法研究了等离子喷涂过程中液态熔滴冲击到基体表面的变形,扩展平化过程,采用Lagrangian方法跟踪平化过程熔滴自由表面的位置。为了避免有限元网格的严格变形及保证计算精度,在计算过程中采用了自动重画网格技术,通过在熔滴-基体界面处引入摩擦力边界条件,描述了基体粗糙度对熔滴平化过程的影响。 相似文献
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等离子喷涂的热源温度高,涂层成形区域温度梯度大、热量累积快,涂层中常存在较大的残余应力。研究通过数值模拟并辅以必要的试验测试研究了等离子喷涂过程基体表面热量累积行为:建立了二维静态喷枪加热模型,研究了在不同喷涂距离时基体表面温度场分布规律;建立了移动热源加热模型,研究了在不同喷枪移动速度和扫描遍数时基体热量累积规律。结果表明:在静态喷枪加热作用下,基体温度场呈中间高两端低的对称分布状态;随着喷涂距离减小,基体表面最高温度与平均温度显著升高,温度梯度变化明显,高温区域半径显著增大。在动态喷枪加热过程中,基体左右边界热量累积现象明显,且喷枪移动速度越快,基体表面热量累积越少,温度分布梯度越小;随着喷枪扫描遍数的增加,基体中心区域温度呈波浪式上升,温度增长幅度逐渐变小。 相似文献
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理解冷喷涂中的颗粒变形和沉积行为一直是科学工作的焦点。由于颗粒撞击基底后的瞬时变形行为难以通过实验观测,因此多数研究工作聚焦于数值模拟。总结了一些颗粒撞击基底的建模方法,在前人研究的基础上,针对每个模型的原理及优缺点,分析了每个方法的适用场景,给出了改善模型的方法。综述了颗粒特性、入射角度、气体预热温度等对颗粒变形行为的影响,其中粒径大小、颗粒形状等是影响颗粒变形行为的主导因素,因此重点探讨了颗粒特性的影响。颗粒的撞击变形是影响冷喷涂涂层残余应力分布的重要因素,对涂层残余应力的相关数值模拟研究进行了综述,分析了颗粒变形与颗粒残余应力的关系。最后就目前冷喷涂残余应力建模较单一的形势,探讨了如何建立一种新模型以分析涂层残余应力。 相似文献
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运用ANSYS1O.O有限元分析软件对等离子喷涂典型双层热障涂层沉积过程的温度和应力变化过程进行了数值模拟.结果表明,喷涂过程中,基体背面温度呈台阶状上升,涂层颗粒的温度大幅度周期波动,涂层颗粒的应力随之大幅度周期波动;喷涂结束后,涂层内的残余应力趋于稳定,x方向的最大拉应力存在于陶瓷层与粘结层结合面的边缘;最大y方向拉应力和层间应力都存在于陶瓷层和粘结层的结合面上.涂层的结合面边缘是应力集中部位,结合面的中部应力分布均匀.陶瓷层表面x方向的最大拉应力为423.7MPa.Abstract: Nmnerical simulation was performed by finite element analysis (FEA) to investigate the temperature and stress in a typical duplex thermal barrier coating. During the spraying process, the temperature of the back surface of substrate increases step by step, both the temperature and the stress of the coating fluctuate periodically within a wide range. After the deposition, the specimen was cooled to the room temperature slowly. The stresses become constant values, and the maximum radial tensile stress exists at the interface between the ceramic layer and the bonding layer, and the maximum axial and shear stresses exist at the interface, where is the concentrated stress area. The stresses of the middle interfaces are uniform. The maximum tensile stress on the ceramic layer surface is 423.7 MPa. 相似文献
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面向等离子熔射成形技术的粉末飞行特性数值分析 总被引:1,自引:0,他引:1
粉末在射流场中飞行特性是影响熔射成形件质量的重要因素。通过所建立的粉末与射流相互作用的动量和能量传递方程,应用有限差分法,模拟计算和分析了粉末速度与温度分布规律及其对成形件质量的影响。结果表明:①粒径及密度越小,加(减)速度越快,而到达原模时的速度则不同;②热传导性越差,粒径越大,极值温度则越小,且逐渐向原模方向偏移;③粉末的力学行为和加热特性的匹配,可进一步提高熔射成形件质量。模拟结果为实现熔射成形质量控制及参数优化,提供了理论依据。 相似文献
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Numerical Study of Combination Parameters for Particle Impact Velocity and Temperature in Cold Spray
Numerical simulations of gas/particle flows of cold spray are performed for N2 and He, respectively, to investigate the usefulness of the two material-independent combination parameters derived from the
equations of particle motion and temperature. The first combination parameter is the particle-diameter multiplied by the material
density, which governs the particle velocity. The second one is the squared particle-diameter multiplied by the material density
and specific heat, which affects the particle temperature. In the numerical simulation, the materials of the spray particle
selected are WC-12Co, Cu and Ti. The numerical results show that the maximum impact velocity of particle is obtained, when
the first combination parameter takes specific value regardless of the material type. Furthermore, it is shown that the particle
diameter and its temperature corresponding to the maximum impact velocity can be graphically estimated by using the two combination
parameters for any powder-materials normally used for the thermal spray.
This article is an invited paper selected from presentations at the 2007 International Thermal Spray Conference and has been
expanded from the original presentation. It is simultaneously published in Global Coating Solutions, Proceedings of the 2007 International Thermal Spray Conference, Beijing, China, May 14-16, 2007, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain
Montavon, Ed., ASM International, Materials Park, OH, 2007. 相似文献
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Three Dimensional Modeling of the Plasma Spray Process 总被引:2,自引:0,他引:2
Results of simulations of three-dimensional (3D) temperature and flow fields inside and outside of a DC arc plasma torch in
steady state are presented with transverse particle and carrier gas injection into the plasma jet. The results show that an
increase of the gas flow rate at constant current moves the anode arc root further downstream leading to higher enthalpy and
velocity at the exit of the torch anode, and stronger mixing effects in the jet region. An increase of the arc current with
constant gas flow rate shortens the arc, but increases the enthalpy and velocity at the exit of the torch nozzle, and leads
to longer jets. 3D features of the plasma jet due to the 3D starting conditions at the torch exit and, in particular, due
to the transverse carrier gas and particle injection, as well as 3D trajectories and heating histories of sprayed particles
are also discussed. 相似文献
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