热超声键合换能系统动力学特性的非线性检验

根据实际超声换能系统的振动测试，提出了热超声键合换能系统动力学特性的非线性检验方法，利用基于相空间重构的替代数据法，通过对换能杆末端的实测数据进行正确替代，并用非线性动力学的理论来检验其是否具有非线性.通过实验对超声换能杆末端轴向、俯仰、横向的振动时间序列的关联维数进行了准确的计算，从而清晰地描述了上述三个方向的动力学特性.所提出的方法有利于更好地认识超声键合换能系统，为建立更加合理的非线性动力学模型奠定良好的理论基础，有很好的应用价值. 关键词： 超声键合 时间序列 相位随机化 替代数据     

大负载超声振动磨削系统的设计

设计了一种大负载超声振动磨削系统,超声系统由换能器、圆柱圆锥形变幅杆和轮辐式砂轮组成。首先将轮辐式砂轮等效成轮毂为圆柱杆、辐板与轮缘为中厚板的复合模型,利用各接触面边界连续的条件推导系统的频率方程,完成了超声磨削系统的设计,制作了实验装置并分析验证了其声学振动特性。实验结果表明:利用轮辐式砂轮复合模型求解系统频率方程,在解决大负载超声振动磨削系统设计难题上的有效性。该超声系统结构简单,声学振动特性稳定,可输出均匀的位移振幅,有望在大负载的超声磨削领域获得应用。     

基于超声波飞行时间的温度测量系统实验研究

超声波测量技术具有速度快、成本低、测量范围广等优点,广泛应用于多种工业领域。为满足工业中对温度测量的需求,本文提出了超声波温度测量系统。本系统基于超声波的传播速度与环境温度的关系,以STC12单片机作为系统硬件电路控制核心,采用幅度和相位调制的矩形波作为发射波,实现在恒温箱空气介质中固定距离下的超声波飞行时间的测量,以此确定介质的平均温度。测量数据由单片机传输到上位机进行处理和显示,并与恒温箱热电偶测得的温度对照,验证实验结果。实验结果证明本系统可以准确测量温度,温度范围约在35℃—90℃。     

Effect of ultrasonic vibration on adhesive enhancement of plasma-modified nickel surface

Poor adhesion of nickel surface limits its further application in the aerospace field. In this study, plasma modification was conducted on the surface of the nickel plate pretreated by sandblasting, and then ultrasonic vibration was applied during the adhesively bonding process of the CFRP(Carbon fibre-reinforced polymer)/Ni joints. The bonding strength of the joints was increased by 65%. The adherend surface and the bonding interface were analyzed from microstructure, element distribution and chemical bonding to study the strengthening mechanism. By the sandblasting, irregular pits were formed on the nickel surface, effectively increasing the surface roughness. The plasma modification could introduce active functional groups including hydroxyl, amino and carbonyl on the nickel surface, which improved the surface wettability macroscopically. However, at a microscopic level, the adhesive with high viscosity and poor fluidity did not form a compact interface with the nickel. The ultrasonic application could promote the filling of the adhesive in irregular micro-scale pits on the surface, thereby strengthening the mechanical anchoring effect. Furthermore, the ultrasonic application produced dynamic impingement at the interface, enhancing the contact between the adhesive and the nickel plate. The adhesive molecules could fully collide and react with the active functional groups introduced on the nickel surface to form more chemical bonds, thus effectively improving the bonding strength of the CFRP/Ni joints.     

Optimization design of high power ultrasonic circular ring radiator in coupled vibration

This paper presents a new high power ultrasonic (HPU) radiator, which consists of a transducer, an ultrasonic horn, and a metal circular ring. Both the transducer and horn in longitudinal vibrations are used to drive a metal circular ring in a radial-axial coupled vibration. This coupled vibration cannot only generate ultrasound in both the radial and axial directions, but also focus the ultrasound inside the circular ring. Except for the radial-axial coupled vibration mode, the third longitudinal harmonic vibration mode with relative large vibration amplitude is also detected, which can be used as another operation mode. Overall, the HPU with these two vibration modes should have good potential to be applied in liquid processing, such as sonochemistry, ultrasonic cleaning, and Chinese herbal medicine extraction.     

纵振驱动球面弯曲振动超声聚焦系统的聚焦特性*

为了将超声聚焦效应应用于工业加工中的冷却技术中,该文提出一种由夹心式换能器纵向振动驱动球面弯曲振动超声聚焦系统。基于基尔霍夫-亥姆霍兹声场理论分析了由换能器中心面纵向振动和球面弯曲振动组成的复合超声振动条件下的声场聚焦特性,并通过实验进行验证。研究结果表明,该聚焦系统具有显著的聚焦特性,球面弯曲振动将声能汇聚在声场焦区;当声场相位相同时,换能器中心面纵向振动和球面弯曲振动产生的声场在焦区发生叠加,可以进一步提高焦区声压;减小换能器中心面半径和球面曲率半径、增加球面开口半径可以增强复合超声振动的聚焦效果。     

超声振动系统频率自动跟踪的模糊控制算法研究

针对大功率超声应用中,工作频带窄、频率跟踪速度要求快的特点,提出将模糊控制智能算法（Fuzzy Control）和数字频率直接合成技术（DDS）相结合的频率自动跟踪方案,依据经验归纳制定模糊控制器来快速跟踪工作频率,将驱动频率调节至谐振频率附近;随后只采用DDS进行频率的微调节,使得电源频率工作在超声换能器的谐振频率点上。最后,通过在MATLAB软件中对控制算法进行验证,表明本文算法具有可行性,能够实现对大功率超声波电源的频率自动跟踪。     

超声振动对于激光烧蚀铝表面温度场仿真分析

针对超声振动对于激光烧蚀铝表面温度场的影响,建立了三维数值模型,利用ANSYS软件对超声振动辅助激光烧蚀金属铝的温度场进行了数值模拟。通过对比不同激光扫描速度、超声振动频率下激光相邻两个光斑温度场随时间的变化,发现相邻光斑的温度、尺寸以及位置均发生改变。数值研究表明,随着激光扫描速度的增加,激光扫描到相同位置的最大温度降低,而且凹坑的深度逐渐变浅;由于超声振动引起的介质分子位移,当超声振动频率为15 kHz时,凹坑温度发生了明显的下降且凹坑位置在振动方向发生了错位,这有利于产生新的激光作用轨迹。     

对超声复合振动系统中“局部共振”现象的一种解释

对超声复合振动系统中的“局部共振”现象,基于熟知的棒或管中声波产生和传播的理论,提出一种机理解释。     

循环温度疲劳作用下粘接界面损伤的非线性超声评价

材料损伤以及性能退化与超声波的非线性效应密切相关.为研究循环温度疲劳作用下粘接界面的损伤情况,本文采用超声波透射法,研究了6061型铝合金/改性丙烯酸酯胶粘接界面的声学非线性系数随高温、低温循环次数的变化情况.结果表明,在高温循环疲劳作用的初始阶段,试件的非线性系数变化不明显,但随着高温循环次数的不断增加,非线性系数随循环次数的变化十分明显;对于低温循环疲劳作用的初始阶段,试件的非线性系数迅速增大,随着循环次数的增加,其值增速减缓.在低温循环疲劳寿命的后期,试件的非线性系数随循环次数的增加而继续增大.进一步的讨论结果表明,胶层三阶弹性常数的变化是造成高温循环疲劳时非线性系数变化的主要原因,而对于低温循环疲劳,粘接界面拉伸刚度的变化是引起非线性系数变化的主要原因.     

超声复合振动系统中局部共振现象的有限元分析

本文用有限元软件对超声复合振动系统中的局部共振现象进行了仿真计算.通过对仿真结果的分析,验证了“局部共振是耦合振动”的观点.在此基础上,用有限元方法进一步研究了截面直径比、工具杆长度等影响局部共振的因素,总结出了产生局部共振的条件.     

Decolorization of azo dye Orange G by aluminum powder enhanced by ultrasonic irradiation

In this work, the decolorization of azo dye Orange G (OG) in aqueous solution by aluminum powder enhanced by ultrasonic irradiation (AlP-UI) was investigated. The effects of various operating operational parameters such as the initial pH, initial OG concentration, AlP dosage, ultrasound power and added hydrogen peroxide (H₂O₂) concentration were studied. The results showed that the decolorization rate was enhanced when the aqueous OG was irradiated simultaneously by ultrasound in the AlP-acid systems. The decolorization rate decreased with the increase of both initial pH values of 2.0–4.0 and OG initial concentrations of 10–80 mg/L, increased with the ultrasound power enhancing from 500 to 900 W. An optimum value was reached at 2.0 g/L of the AlP dosage in the range of 0.5–2.5 g/L. The decolorization rate enhanced significantly by the addition of hydrogen peroxide in the range of 10–100 mM to AlP-UI system reached an optimum value of 0.1491 min⁻¹. The decolorization of OG appears to involve primarily oxidative steps, the cleavage of NN bond, which were verificated by the intermediate products of OG under the optimal tested degradation system, aniline and 1-amino-2-naphthol-6,8-disulfonate detected by the LC–MS.     

超声空化引起界面湍动促进的传质机理

本文分析了超声空化引起界面湍动对传质过程的影响,提出了相界面上超声空化气泡析出增强边界层液体湍动并促进传质的机理,在传质理论和流体动力学原理的基础上,建立了超声空化引起界面湍动促进的传质机理模型,获得了超声空化引起界面湍动促进的传质系数表达式。实验结果验证了模型的合理性。该模型既证实了超声对传质有强化效应,又对传质过程有很好的预测功能,为工业化提供了理论依据。     

Enhanced electron field emission characteristics of single-walled carbon nanotube films by ultrasonic bonding

A novel ultrasonic bonding process was used to fabricate the electron field emission cathode of single-walled nanotube film, which was deposited on an Al plate substrate by electrophoretic deposition. Electron field emission properties were improved remarkably after the cathode carbon nanotubes nanobonded with the Al substrate. Turn-on voltage showed a significant decrease and the emission current was much stabilized. This can be attributed to the reduction of the contact resistance in bonding area and easily moving electrons for field emission after ultrasonic bonding. In addition, the field emission performances of SWCNTs films formed at different bonding conditions were also studied. With a simple nano-bonding apparatus, this technique has low cost, and can be utilized for extensively roboticized fabrication of high performance field emission cathodes with short process time.     

Effects of high power ultrasonic vibration on temperature distribution of workpiece in dry creep feed up grinding

Temperature history and distribution of steel workpiece (X20Cr13) was measured by a high tech infrared camera under ultrasonic assisted dry creep feed up grinding. For this purpose, a special experimental setup was designed and fabricated to vibrate only workpiece along two directions by a high power ultrasonic transducer. In this study, ultrasonic effects with respect to grinding parameters including depth of cut (a_e), feed speed (v_w), and cutting speed (v_s) has been investigated. The results indicate that the ultrasonic vibration has considerable effect on reduction of temperature, depth of thermal damage of workpiece and width of temperature contours. Maximum temperature reduction of 25.91% was reported at condition of v_s = 15 m/s, v_w = 500 mm/min, a_e = 0.4 mm in the presence of ultrasonic vibration.     

新型柱孔式模式转换型纵-扭复合模态超声振动系统*

为了改善基于螺旋槽结构和斜槽结构的模式转换型纵-扭复合模态超声振动系统存在的结构复杂、扭转分量较小等问题,论文提出了基于新型柱孔式复合变幅杆的模式转换型纵-扭复合模态超声振动系统,并利用有限元法和数据分析对其进行了仿真分析,结果表明,引入新型柱孔式复合变幅杆的系统的输出端面的剪切应力、旋转角度得到了大幅提升,能够有效地提高纵、扭振动的转换效率。     

人体血管壁超声传输衰减特性的研究

本文利用超声脉冲反射法，对人体血管壁声衰减特性进行了离体测量，给出了人体血管壁声能量衰减参数的测量值。这对超声在医学领域的应用以及超声连体非介入血栓消溶有着十分重要的意义。     

Alternate stresses and temperature variation as factors of influence of ultrasonic vibration on mechanical and functional properties of shape memory alloys

It is known that the main factors in a variation in the shape memory alloy properties under insonation are heating of the material and alternate stresses action. In the present work the experimental study of the mechanical behaviour and functional properties of shape memory alloy under the action of alternate stresses and varying temperature was carried out. The data obtained had demonstrated that an increase in temperature of the sample resulted in a decrease or increase in deformation stress depending on the structural state of the TiNi sample. It was shown that in the case of the alloy in the martensitic state, a decrease in stress was observed, and on the other hand, in the austenitic state an increase in stress took place. It was found that action of alternate stresses led to appearance of strain jumps on the strain–temperature curves during cooling and heating the sample through the temperature range of martensitic transformation under the constant stress. The value of the strain jumps depended on the amplitude of alternate stresses and the completeness of martensitic transformation. It was shown that the heat action of ultrasonic vibration to the mechanical behaviour of shape memory alloys was due to the non-monotonic dependence of yield stress on the temperature. The force action of ultrasonic vibration to the functional properties was caused by formation of additional oriented martensite.     

一种测量功率超声振动系统振速比的简单方法

本文提出了一种测量功率超声振动系统中振动速度比的简单方法。与传统的测量方法相比,本方法将力学量转变为电学量的测量,将绝对测量变成了相对测量,降低了对实验设备的要求,有利于提高测试精度。     

超声波信号渡越时间参数法测量空气中温度分布

超声波已成功在医疗、化工和无损探伤等领域得到广泛的应用。根据超声波在空气中的传播速度会随着温度改变而改变这一特点,本文把空气中的温度场作为研究对象,利用超声波信号在空气中的渡越时间参数TOF(Time of Flight)来对空气中的温度分布情况进行超声波CT画像的重建。