15kHz超声铸造振动系统设计及其试验研究

【作者】 邓丽娜；

【导师】 李晓谦；

【作者基本信息】 中南大学 ， 机械设计及理论， 2010， 硕士

【摘要】 功率超声产生的空化、声流、机械等非线性效应可以使物质的一些物理、化学、生物特性或状态发生改变。金属凝固过程中施加功率超声可以有效地改善铸锭凝固组织,提高材料特性和机械性能。铝合金铸造过程中引入超声场是当前研究的热点及未来铸造技术的一个新发展方向。本文主要以7050铝合金超声铸造为切入点,主要从以下几方面进行了研究：1.结合铝合金铸造的特点,确定了换能器和变幅杆的类型和材质。根据任意变截面的波动方程及振动系统的设计原理,建立了换能器和变幅杆结构的物理和数学模型。在此基础上对15kHz的超声振动系统的主要结构换能器、前后端盖、变幅杆和工具杆进行了设计。2.在ANSYS有限元分析软件中建立了15kHz超声振动系统有限元模型,并通过模态分析计算得出该系统的主要动态性能。应用多普勒测振仪测量了该超声波振动系统的纵向谐振频率、位移振幅等主要性能参数。实验结果与仿真结果一致,说明了设计和有限元模型建立的合理性。3.应用恒流量热法,分别测量了15kHz和20kHz超声振动系统的实际输出功率及其在液体中能量的规律。应用不同超声振动系统分别进行水模拟实验和7050铝合金超声铸造试验。试验结果表明：15kHz超声振动系统在液体中作用效果比20kHz强烈；在铝熔体中导入功率超声对铝合金凝固组织有较好的细化效果,晶粒组织均有粗大的枝状晶变成均匀的等轴晶。在相同的条件下,15kHz对铝合金的细化作用效果较20kHz的更明显,晶粒更均匀和细化。且随着超声功率的增加,晶粒细化效果越明显。更多还原

【Abstract】 Power ultrasonic has special acoustic characteristics which can greatly change the properties of physics、chemistry、biology of substances, or expedite such changes. Treating aluminum melt with power ultrasonic can improve solidification structure and mechanical properties of metals obviously. It is the international research hotspot nowadays and a new developing direction of technology of aluminum alloy casting. Taking the 7050 aluminum alloy ultrasonic casting as research object, the main study of the paper was done as follows:1.Combined with the characteristic of the casting, the longitudinal oscillation equation of ultrasonic horn with random variable cross-section was discussed. The physical and mathematical models were established. Based on the above, by choosing appropriate material and size, the main structures of ultrasonic vibration system of 15 kHz were designed.2.The computer simulation of the new designed ultrasonic vibration system was performed by employing the FEM software ANSYS, through which the resonance frequency, vibration displacement modes and distribution of amplitude were acquired. The new designed ultrasonic vibration system was tested through the laser Doppler vibrometer, which proves the resemblance with the theory and FEM.3.The output power of ultrasonic vibration system was obtained by experiment. The rule of the effect of ultrasonic vibration in liquid was studied by water simulation experiments.7050 aluminum was treated with ultrasonic vibrations of 15 kHz and 20 kHz respectively by dipping the acoustic radiator into melt. Experimental results show that the microstructure with fine uniform non-dendrite grain was achieved with ultrasonic vibration of both systems. By compared with the experiment result, the effect of 15 kHz is better than that of 20 kHz under the same condition.更多还原