超声导波电磁声换能器的研究进展

超声导波具有检测范围大、检测效率高等优点,广泛应用于板、管等典型波导结构的缺陷检测.作为超声导波换能器类型之一,电磁声换能器(electromagnetic acoustic transducer,EMAT)得到广泛关注和快速发展.综述了近20年来超声导波电磁声换能器的研究进展.主要包括:针对板和管结构超声导波检测的单模态EMAT结构设计;用于提高激励导波的能量和模态单一性的EMAT线圈与磁体结构参数的优化,针对非金属材料检测的新型贴片式EMAT的结构设计;阵列技术在EMAT性能优化上的应用和在缺陷定位和成像上的应用.     

超声振动辅助微小孔高速钻削技术研究

结合高速钻削和超声振动钻削优点,自行研制出超声振动辅助高速钻削机床。利用该机床,通过实验对比超声振动辅助高速钻削和普通钻削条件下加工工件的孔扩量、表面粗糙度和出孔、入孔毛刺等参数,研究评价超声振动辅助高速钻削性能。实验结果表明,相对于普通钻削,超声振动辅助高速钻削可实现φ0.1mm、深径比大于10的微细深孔加工,实验结果证明了理论与实验分析的正确性。     

Effect of electromagnetic and ultrasonic cast rolling on microstructure and properties of 1050 aluminum substrate for presensitized plate

The 1050 aluminum alloy strip was prepared by means of electromagnetic and ultrasonic cast rolling on the modified asymmetric twin roll caster, and then the aluminum substrate for presensitized plate was prepared through cold rolling and annealing.The effects of electromagnetic and ultrasonic cast rolling on microstructure, mechanical properties, surface roughness and electrolytic corrosion properties of 1050 aluminum substrate were studied. The results show that electromagnetic and ultrasonic cast rolling can decrease the average crystallite size of aluminum substrate by 5 μm, increase the crystal boundaries with uniform distribution, and make the second-phase particles with smaller size distributed dispersively in the substrate, meanwhile, it can increase the tensile strength, elongation and micro-hardness by 4.58%, 9.85% and HV 2, respectively, reduce the surface roughness, make the surface appearance more even, electrolytic corrosion polarization curve of aluminum substrate more smooth and the surface corrosion pits with regular shape more dispersive.     

超声波协同氯化钙对油炸猪肉片嫩度和感官品质的影响

探讨不同超声波强度协同不同浓度Ca Cl2溶液对油炸猪肉片的嫩度和感官品质的影响。以质构、剪切力、水分含量、感官评定为测定指标,肉片经预处理、挂糊、油炸、冷却、复炸后测定肉制品的各个指标。结果表明:单独使用超声波或氯化钙对肉片的嫩度、水分含量、感官影响都不明显,超声强度180w/m2协同Ca Cl210%对肉片质构影响最大,硬度下降了34%,粘度增加40%;超声强度180w/m2协同Ca Cl210%实验组的肉片剪切力比对照组下降了10.61N;超声强度180w/m2协同Ca Cl210%的肉片水分含量增加23.31%;超声强度200w/m2协同Ca Cl25%感官评定的总分最高为62分。     

超声珩磨装置振动子系统的振动特性研究

为进一步研究超声珩磨装置的挠性杆-油石座振动子系统的"局部共振"现象,把挠性杆和油石座视为动力学意义下的独立环节,将超声珩磨装置的挠性杆-油石座振动子系统简化为由挠性杆和油石座环节串联组成的振动系统。以等截面直杆的振动理论为基础,建立了此振动子系统的自然频率和振动位移的计算公式。结果表明:理论计算与试验结果比较接近,能够方便地解释超声珩磨装置振动子系统的"局部共振"现象,为合理设计挠性杆-油石座振动子系统的参数提供了理论依据。     

Application of Piezoelectric Materials in a Novel Linear Ultrasonic Motor based on Shear-induced Vibration Mode

A novel linear ultrasonic motor based on d15 effect of piezoelectric materials was presented. The design idea aimed at the direct utilization of the shear-induced vibration modes of piezoelectric material. Firstly, the inherent electromechanical coupling mechanism of piezoelectric material was investigated, and shear vibration modes of a piezoelectric shear block was specially designed. A driving point's elliptical trajectory induced by shear vibration modes was discussed. Then a dynamic model for the piezoelectric shear stator was established with finite element(FE) method to conduct the parametric optimal design. Finally, a prototype based on d15 converse piezoelectric effect is manufactured, and the modal experiment of piezoelectric stator was conducted with laser doppler vibrometer. The experimental results show that the calculated shear-induced vibration modes can be excited completely, and the new linear ultrasonic motor reaches a speed 118 mm/s at noload, and maximal thrust 12.8 N.     

超声提取贯叶连翘中总黄酮和金丝桃素的工艺研究

研究了从贯叶连翘中同时提取总黄酮和金丝桃素的最佳工艺条件,探讨了采用超声波辅助乙醇提取的方法来考查乙醇浓度、料液比、提取温度、提取时间、提取次数等因素对总黄酮和金丝桃素得率的影响,并结合正交试验确定最佳工艺.实验结果表明,最佳工艺参数为乙醇浓度70%、料液比1∶25、提取温度50℃、提取时间60min、提取2次,总黄酮和金丝桃素的得率分别为7.02%和0.178%,采用此工艺提取快速、简便,为贯叶连翘资源的开发利用奠定了基础.     

超声场对亚临界CO2萃取葵花籽油的影响

以葵花籽为原料,研究了超声场对亚临界CO2萃取葵花籽油的影响。实验结果表明,超声场能够明显提高亚临界CO2萃取葵花籽油萃取率,在压力为25 MPa、温度为30 ℃、流速为 3 L/h时,萃取240 min后超声作用（100 W/L、4 s/ 6s）和未加超声的萃取率分别为94.81%和74.82%;超声功率密度和频率对萃取率具有较大影响,随着超声功率密度的增大,萃取率增加,而20 kHz与38 kHz超声相比,20 kHz超声对萃取更为有利;采用4 s/6 s的超声辐射方式比较合理;超声作用起始时间对葵花籽油萃取率也有一定的影响。GC/MS结果显示超声作用没有改变葵花籽油组成成分以及各成分的结构。提出了超声强化的可能机理是超声波动效应和热效应。     

微-纳米复合陶瓷超声振动磨削的塑性-脆性 转变特征研究

基于工件超声振动磨削的单磨粒运动模型,建立超声振动磨削单磨粒最大切削厚度agm ax公式;基于压痕断裂力学,给出硬脆材料超声振动磨削塑性-脆性转变临界条件,进行超声振动磨削与普通磨削对比试验,应用SEM和AFM分析陶瓷磨削表面微观形貌特征,重点研究磨削参数对其塑性-脆性转变特征的影响。研究结果表明,砂轮平均磨粒尺寸是影响塑性-脆性转变最为主要的因素,砂轮速度对其影响次之,磨削深度对塑性-脆性转变的影响最小;得出只有当agm ax小于临界切削深度agc时,才能实现硬脆材料塑性域磨削的重要结论。     

直缝焊管焊缝质量电磁超声检测方法研究

为实现直缝焊管焊缝内缺陷检测,采用周向电磁超声SH0导波检测技术,研究了基于磁致伸缩效应激励周向SH0模态导波,确定了周向SH0导波激励频率,设计了一款一发双收差分接收的直缝焊管焊缝缺陷检测探头。结果表明:该系统能够激发单一模态周向SH0导波,实际波速与模型分析结果吻合;针对直径116 mm、壁厚3.5 mm的激光直缝焊管焊缝的Φ0.6 mm盲孔和Φ1.0 mm通孔,通过差分探头的信号处理,能够实现焊缝处Φ1.0 mm通孔和Φ0.6 mm盲孔缺陷的检测。