超声波流量计的全数字式准确计时方法

本文详细讨论了超声波流量计的测量与计时原理,采用两组高频脉冲序列计数以提高计时电路的分辨率,并通过电路实验测定了两组脉冲频率分别为2.1MHz和1.93MHz时,计时电路分辨率的大小。实验结果与理论计算完全相符。最后提出了一种新型的功能性强的超声波流量计实施方案。     

超声波喷嘴试验研究

对超声波喷嘴的工作原理及工作特性进行了理论分析和试验研究,利用计算机图象处理技术重点研究了压电器件材料物性参数d33、激励电压A、喷射压力p、喷孔直径d0、喷嘴腔纵向尺寸δ及激励频率f对射流液滴形成的影响。研究表明：较低的射流压力和较小的喷孔直径以及较大的d33压电器件都有利于液滴的形成和工作稳定性,而激励频率f和喷嘴腔纵向距离δ都存在着最佳值。这些结论可以指导喷印机超声波喷嘴的设计。     

Thermomechanical coupling effect on characteristics of oxide film during ultrasonic vibration-assisted ELID grinding ZTA ceramics

Ultrasonic vibration-assisted ELID (UVA-ELID) grinding is utilized as a novel and highly efficient processing method for hard and brittle materials such as ceramics. In this study, the UVA-ELID grinding ZTA ceramics is employed to investigate the influence of thermomechanical loading on the characteristics of oxide film. Based on the fracture mechanics of material, the model of internal stress for oxide film damage is proposed. The thermomechanical loading is composed of mechanical force and the thermal stress generating from grinding temperature. The theoretical model is established for the mechanical force, thermal stress and internal stress respectively. Then the finite element analysis method is used to simulate the theoretical model. The mechanical force and grinding temperature is measured during the actual grinding test. During the grinding process, the effect of grinding wheel speed and grinding depth on the thermomechanical force and the characteristics of oxide film is analyzed. Compared with the conventional ELID (C-ELID) grinding, the mechanical force decreased by 25.6% and 22.4% with the increase of grinding wheel speed and grinding depth respectively, and the grinding temperature declined by 10.7% and 12.8% during the UVA-ELID grinding. The thermal stress in the latter decreased by 16.3% and 20.8% respectively, and internal stress reduced by 12.3% and 15.6%. It was experimentally found that the topographies of oxide layer on the surface of the wheel and the machined surface in the latter was better than that in the former. The results indicate that the action of ultrasonic vibration establish a significant effect on the processing. Subsequently, it should be well considered for future reference when processing the ZTA ceramics.     

Effect of ultrasonic vibration on finished quality in ultrasonic vibration assisted micromilling of Inconel718

Inconel718 was machined with the traditional micromilling (TMM) and ultrasonic vibration assisted micromilling (UVAMM) with the different technology parameters, whose surface quality and burrs formation were studied. The results show that TMM often forms pits, bumps and gullies in the size effect range. UVAMM effectively improves the surface quality compared with TMM. The surface defects are significantly reduced with the increase of feed per tooth (ƒ_z). When ƒ_z exceeds 4 μm, the effect of ultrasonic vibration on the surface quality is no longer obvious. The minimum burr size on the down milling side and the up milling side are 50.23 μm and 36.57 μm, respectively. The feasibility of vibration cutting in improving surface quality and suppressing burr size was verified. UVAMM effectively suppresses the formation of built-up edge, which can significantly improve the micromilling process. The cutting force is obtained through simulation and experiment. They are agreement in the change trend. The finite element simulation can be used to predict the cutting force. Compared with TMM, feeding force (F_x), radial force (F_y) and axial force (F_z) of UVAMM decrease by 7.6%, 11.5% and 1.3%, respectively.     

不分离型超声复合铣削系统稳定性研究

为研究不分离型超声复合铣削系统的稳定性,讨论了超声复合铣削运动特性,建立了不分离型超声复合铣削稳定性模型。利用半离散法对超声复合铣削稳定性进行研究,应用MATLAB软件进行数值分析并得出了超声铣削稳定性叶瓣图。研究表明,不分离型超声复合铣削能提高普通铣削系统的稳定性,最大极限切削深度提高约13.8%。利用钛合金材料进行超声复合铣削的试验验证,试验结果验证了理论模型与稳定性叶瓣图的正确性,同时也验证了利用半离散法分析超声复合铣削系统稳定性的可行性。     

复合材料超声辅助螺旋铣削试验研究

采用螺旋铣削与超声振动复合加工工艺针对碳纤维树脂基复合材料进行制孔加工试验.分析了超声辅助螺旋铣削制孔加工原理;以相同加工效率开展了制孔试验,分析了制孔过程中的切削力及孔的加工质量;阐述了加工参数对切削力、切屑形式和制孔质量的影响.研究结果表明:超声辅助螺旋铣削复合加工方法可以用于碳纤维复合材料加工,且增加超声振动幅值、降低刀具每齿材料去除量可有效减少孔出口处的毛刺、撕裂等加工缺陷.     

采用超声波电机的空间飞网自适应收口机构设计

介绍了一种采用超声波电机作为驱动源的空间飞网自适应收口机构（质量块）的设计及实现方法。通过分析捕获过程中质量块运动情况,研究超声波电机电流与负载的关系,确定以加速度信号和电流信号作为电机启动和停止的触发信号,在此基础上设计并实现了质量块的驱动控制系统。通过在电机输出轴与卷筒间加入差动轮系构成双卷筒机构,力学分析证实了该机构在负载不均衡情况下的自适应性。分析证明该机构使飞网的捕获操作对捕获平台的精度要求降低,有容错能力。同时使收口机构在部分质量块故障时也能完成捕获任务。     

用超声波检测铝—铜复合板材

介绍铝－铜复合薄板材的超声波检测方法。论述了采用界面回波相位判断法和幅度Ｃ扫描检测法确定该种复合板中脱接缺陷的要点,并对各种方法的检测结果进行了分析。     

纤维增强铝复合丝弹性模量的测试与分析

通过自行改进的装置对束丝纤维复合丝的弹性模量进行了测试,并对复合丝拉伸过程中的切线弹性模量随应变化的规律进行了分析讨论,发现该复合材料切线弹性模量在基体屈服应变附近有明显的转折点,通过准确测定两个阶段的弹性模量可以获得评价复合丝复合质量的有关参数。