Combined effects of ultrasonic vibration and FeCoNiCrCu coating on interfacial microstructure and mechanical properties of Al/Mg bimetal by compound casting

In this work,a new treatment method combining ultrasonic vibration with FeCoNiCrCu high entropy alloy(HEA)coating was used to prepared Al/Mg bimetal through the lost foam compound casting.The effects of composite treatment involving ultrasonic vibration and HEA coating on interfacial microstructure and mechanical properties of Al/Mg bimetal were studied.Results demonstrate that the interface thickness of the Al/Mg bimetal with composite treatment significantly decreases to only 26.99%of the thickness observed in the untreated Al/Mg bimetal.The HEA coating hinders the diffusion between Al and Mg,resulting the significant reduction in Al/Mg intermetallic compounds in the interface.The Al/Mg bimetal interface with composite treatment is composed of Al_(3)Mg_(2)and Mg_(2)Si/AlxFeCoNiCrCu+FeCoNiCrCu/δ-Mg+Al_(12)Mg_(17)eutectic structures.The interface resulting from the composite treatment has a lower hardness than that without treatment.The acoustic cavitation and acoustic streaming effects generated by ultrasonic vibration promote the diffusion of Al elements within the HEA coating,resulting in a significant improvement in the metallurgical bonding quality on the Mg side.The fracture position shifts from the Mg side of the Al/Mg bimetal only with HEA coating to the Al side with composite treatment.The shear strength of the Al/Mg bimetal increases from 32.16 MPa without treatment to 63.44 MPa with ultrasonic vibration and HEA coating,increasing by 97.26%.

Effect of ultrasonic vibration on Fe-containing intermetallic compounds of hypereutectic Al-Si alloys with high Fe content

The Fe-containing intermetallic compounds with high melting point in hypereutectic Al-Si alloys can improve the heat resistance and wear resistance at elevated temperatures. However, the long needle-like Fe-containing compounds in the alloys produced by conventional casting process are detrimental to the strength of matrix. The effect of ultrasonic vibration （USV） on the morphology change of Fe-containing intermetallic compounds in the hypereutectic Al-17Si-xFe （x=2, 3, 4, 5） alloys was systematically studied. The results show that, the Fe-containing intermetallic compounds are mainly composed of long needle-like β-Al5FeSi phase with a small amount of plate-like δ-Al4FeSi2 phase in Al-17Si-2Fe alloy produced by conventional casting process. With the increase of Fe content from 2% to 5% in the alloys, the amount of plate-like or coarse needle-like δ-Al4FeSi2 phase increases while the amount of long needle-like β-Al5FeSi phases decreases. In Al-17Si-5Fe alloy, the Fe-containing intermetallic compounds exist mainly as coarse needle-like δ-Al4FeSi2 phase. After USV treatment, the Fe-containing compounds in the Al-17Si-xFe alloys are refined and exist mainly as δ-Al4FeSi2 particles, with average grain size ranging from 26 μm to 37 μm, and only a small amount of β-Al5FeSi phases remain. The mechanism of USV on the morphology of Fe-containing intermetallic compounds was also discussed.

Effect of vibration on interfacial microstructure and mechanical properties of Mg/Al bimetal prepared by a novel compound casting

In this work,a vibration was applied in the preparation of the Mg/Al bimetal by a novel compound casting in order to improve the mechanical properties of the Mg/Al bimetal,and the effect of the vibration on the interfacial microstructure and mechanical properties of the Mg/Al bimetal was investigated.The results indicated that the vibration had a significant effect on the interfacial microstructure and mechanical properties of the Mg/Al bimetal,but it did not change the phase compositions of the interface,which was composed of layerⅠ(Al3Mg2+Mg2Si),layerⅡ(Al_(12)Mg_(17)+Mg_(2)Si)and layerⅢ(Al_(12)Mg_(17)/δ-Mg).Without vibration,the Mg_(2)Si phase with a needle-like morphology mainly aggregated in the layerⅡof the interface.After the application of the vibration,the SEM and EBSD analysis results showed that the Mg_(2)Si and Al3Mg2phases in the interface were obviously refined,and the distribution of the Mg_(2)Si became more uniform,due to the strong forced convection of the molten metal resulting from the vibration.The TEM analysis indicated that the interface between the A_(l3)Mg_(2) and Mg_(2)Si phases was non-coherent,suggesting the Mg_(2)Si particles cannot act as a heterogeneous nucleation base during the solidification process of the interface.Compared to the Mg/Al bimetal without vibration,the shear strength of the Mg/Al bimetal with vibration increased by about 50%from 31.7 MPa on average to 47.5 MPa,and the hardness of the layer I of the interface increased,and the hardness of the layerⅢdecreased.The fracture surface transformed from a flat fracture morphology without vibration to an irregular zigzag fracture morphology.

Effect of Compound Energy-Field with Temperature and Ultrasonic Vibration on Mechanical Properties of TC2 Titanium Alloy

To solve the problem of the poor plasticity and to meet the requirements of high temperature for forming titanium alloy,mechanical properties of TC2 titanium alloy under the compound energy-field(CEF)with temperature and ultrasonic vibration were studied.The effects of CEF on tensile force,elongation,microstructure and fractography of the TC2 titanium alloy were compared and analyzed.The results show that,under the same thermal conditions,the deformation resistance of TC2 titanium alloy decreases with the increase of ultrasonic vibration energy.The formability is also improved correspondingly due to the input of ultrasonic vibration energy and its influence on the microstructure of the material.However,when the ultrasonic vibration energy is larger,the fatigue fracture will also appear,which reduces its formability.

Investigation of Self Excited Torsional Vibrations of Different Configurations of Automatic Transmission Systems during Engagement

The vehicle drive line system is subjected to torsional vibration from different sources of the system such as;engine fluctuating torque, Hook’s joint and the final drive. However, the essential source is the friction torque induced in the friction elements, during their engagement. In the automatic transmission system, the planetary gear set includes several friction elements such as;clutch, band brakes, and one way clutch. During the engagement, severe torsional vibration is induced by friction which is noticeable by the passengers in the form of what so called vehicle shunt. In present paper, a torsional vibration model for Drive Line (DL) system includes three different configurations of automatic transmission is constructed. A computer program using MATLAB subroutines is implemented to obtain the system response. Effect of system parameters on the dynamic behavior and stability has been investigated. The system damping and the trend of the friction coefficient have an essential effect on the dynamic behavior and stability of the system. The system response is now predictable with change of the system parameters which opens up the opportunity in future to control the vibration level.

空蚀实验装置的超声振动系统及其变幅杆研制

空蚀是水力机械常见的失效破坏形式,常用超声空蚀实验装置来研究空蚀过程及材料的抗空蚀性能。针对超声空化原理及超声空蚀实验装置的要求,利用变截面的波动方程和传统变幅杆的设计理论设计了圆锥复合变幅杆;通过ANSYS软件对变幅杆进行模态分析和谐响应分析,并对其进行多尺寸结构优化设计,以获得最优尺寸参数;根据优化参数研制了圆锥复合变幅杆,将其与换能器和工具头联接构成装置的超声谐振系统,并进行了阻抗分析和振动性能测试,结果表明变幅杆振动效果良好、满足超声空蚀实验装置的要求。

基于ITD-LE指标的航空发动机中介轴承复合故障识别

为了基于航空发动机整机机匣振动信号实现中介轴承复合故障的有效识别,从信号的复杂性角度出发,利用图谱中的拉普拉斯能量(Laplace Energy, LE)指标对信号的复杂性进行描述,提出了将固有时间尺度分解(Intrinsic Time Scale Decomposition, ITD)与LE指标相结合的故障诊断方法。为实现复合故障的有效分离,基于ITD算法对某型航空发动机整机机匣振动加速度信号进行分解,并对分解后获得的固有旋转分量(Proper Rotation Components, PRCs)基于奇异值差分谱进行降噪。然后利用LE指标对分量信号进行筛选,对筛选后的信号进行重构,最后根据重构信号的平方解调谱,对实际航空发动机中介轴承的复合故障进行识别。结果表明:所提出的方法,可以基于航空发动机的整机机匣振动信号,准确有效地提取出中介轴承复合故障的特征频率,实现中介轴承复合故障类型的有效识别。

负载口独立控制系统非线性滤波振动抑制方法

针对负载口独立控制系统在作业过程中时常因控制信号突变而造成执行器速度振荡及液压缸两腔压力波动,从而导致操作舒适性和机器可靠性降低甚至引发安全事故的问题,首先,分析了负载口独立控制系统压力流量复合控制策略以及传统阻尼补偿方法抑振的局限性,阐明了引发速度振荡与压力波动的原因;然后,基于该控制系统,提出了采用非线性滤波器修改突变控制信号的抑振方法,并给出了非线性滤波器的边界选取原则;最后,设计了负载口独立控制系统的进出口阀控制器,通过修改参考流量信号,降低了不同突变信号对执行器速度带来的影响。基于20 t挖掘机负载口独立控制系统开展数值仿真,结果表明:相较于传统阻尼补偿方法,采用所提方法能够有效降低阶跃、斜坡信号引起的执行器速度振荡与压力波动,且在动臂液压缸全伸、全缩典型工况下压力波动较小,并使速度振荡降低了32.5%~64.7%,从而有效改善了系统的动态特性。

超微粉碎辅助酶解法制备海参冻干粉的生物活性分析

以超微粉碎辅助酶解法制备的海参(Cucumaria frondosa)冻干粉为研究对象,通过DPPH自由基清除率、羟基自由基清除率和还原力、HeLa细胞增殖抑制率、小鼠转棒实验及血乳酸(lactic acid,LA)含量和环磷酰胺(cyclo-phosphamide,CY)诱导的免疫缺陷小鼠实验及免疫球蛋白G(immunoglobulin G,IgG)含量,分别研究海参冻干粉的抗氧化能力、抗肿瘤、抗疲劳和提高免疫力的能力。结果表明,DPPH自由基清除率的IC50为12.46 mg/mL,羟基自由基清除率的IC50为15.22 mg/mL,还原力为0.35,表明海参冻干粉具有抗氧化能力。海参冻干粉对HeLa细胞增殖抑制率的IC50为556.2μg/mL,表现出抗肿瘤能力。通过灌胃海参冻干粉,小鼠转棒运动时间随着剂量升高而延长,运动后高剂量组的LA含量(19.15 mmol/L)较低,说明小鼠运动耐力提高,且CY诱导的免疫缺陷小鼠降低了体质量的下降速率,高剂量组IgG含量恢复到11.98 mg/mL。综上,海参冻干粉具有抗氧化、抗肿瘤抗疲劳和提高免疫力的多功能活性潜力。

振动量级和胶料硬度对T形橡胶减振器振动特性的影响

对随机振动激励下橡胶减振器的减振机理进行研究,推导出橡胶减振系统的均方根(RMS)加速度响应计算公式,并研究了振动量级和胶料硬度对T形橡胶减振器(简称橡胶减振器)振动特性的影响。结果表明:橡胶减振器的传递率峰值随振动量级和胶料硬度的增大而减小;橡胶减振器的减振效率随振动量级的增大而增大,随胶料硬度的增大而减小;橡胶减振系统的RMS加速度响应理论值与试验值的误差绝对值较大,通过线性拟合并对理论值进行修正后,可以将误差控制在+5%以内。

基于仿真动力学模型的缺陷轴承动态特性分析

滚动轴承是数控机床主轴传动系统中重要的支撑部件,轴承组件出现缺陷会影响整个数控机床传动系统的使用性能和工作效率。为了探究缺陷状态下轴承内部动态特性的差异,以7002C角接触球轴承为研究对象,进行了缺陷轴承动态特性研究。首先,利用有限元仿真软件,构建了轴承组件存在凹坑缺陷的仿真动力学模型;随后,对轴承不同转速下的滚珠公转速度仿真结果和理论计算结果进行了比较,验证了所建立动力学仿真模型的准确性;最后,综合分析了轴承外圈缺陷、滚珠缺陷及两者复合缺陷时的动态特性。研究结果表明:复合缺陷相对于单一缺陷有更高的剪切应力,且呈现波动剧烈的趋势;不同故障状态展现出振动信号的差异,滚珠缺陷表现出较小波动,外圈缺陷较稳定,而复合缺陷最不稳定,振动幅度最大;滚珠的公转速度表现出不规则和不一致的变化,滚珠缺陷、外圈缺陷和复合缺陷在速度曲线上表现出相似但略有不同的周期性和峰谷延迟。所构建的有限元模型可用于研究不同故障状态下滚动轴承的动态特性,为轴承优化设计提供参考。

Effect of compound field on horizontal continuous casting of Al-1wt.%Si alloy

A travel ing magnetic field, a power ultrasonic field, and a compound field were used separately during the horizontal continuous casting process of Al-1wt.%Si al oy. The samples obtained were characterized using an optical microscope, a scanning electron microscope, a tensile testing machine, and an electron probe microscopic analyzer to test the microstructures, properties, and element distribution of the samples. The results show that the application of a single ifeld can enhance the mechanical properties and reduce the segregation of Si element in Al-1wt.%Si alloy to some extent. The application of a compound field can obtain the best reifnement and homogeneity of the Si element in the al oy, leading to the highest increase of tensile strength and elongation among the three applied ifelds. The mechanism of the action of external ifelds on the reifnement of microstructures and homogeneity of the Si element is discussed and the compound ifeld is considered to be an effective method to achieve high quality Al alloys.

Research on Planar Double Compound Pendulum Based on RK-8 Algorithm

Establishing the Lagrangian equation of double complex pendulum system and obtaining the dynamic differential equation,we can analyze the motion law of double compound pendulum with application of the numerical simulation of RK-8 algorithm.When the double compound pendulum swings at a small angle,the Lagrangian equation can be simplified and the normal solution of the system can be solved.And we can walk further on the relationship between normal frequency and swing frequency of double pendulum.When the external force of normal frequency is applied to the double compound pendulum,the forced vibration of the double compound pendulum will show the characteristics of beats.

桥臂电抗器的振动噪声分析与控制

桥臂电抗器受到交变电磁力作用而处于振动状态,产生的噪声引起了不可忽视的环境干扰问题。针对该问题,根据关键参数计算结果建立了桥臂电抗器的电磁-振动-声多场耦合模型,分析了桥臂电抗器主要振动频率特性和噪声辐射方向效应,研究了交直流复合工况和边界吸声系数对噪声的影响规律。结果表明:噪声分布的方向性主要由固有频率振型决定,直流与交流分量的相互作用将影响噪声分布的主要方向;提升周围边界吸声系数可以降低声压级水平。进一步获得了加隔音装置后电抗器的声场仿真结果,利用正交试验和方差分析研究了隔音装置参数对声压级水平和材料用量的影响程度,构建了基于Kriging代理模型的隔音装置多目标优化模型。优化后结构的降噪效果显著,其中声压级水平下降15.2%,隔音装置材料用量减少8.9%。

含故障受油器机组转子-转轮系统振动特性分析

灯泡贯流式机组实际运行中,转子-转轮系统受各外激励影响易形成旋转部件与固定部件间的碰摩故障,极大影响机组的安全稳定运行。针对含故障受油器部件的灯泡贯流式机组轴系碰摩问题,构建转子处复合偏心影响下不平衡磁拉力模型,建立了多振源激励下含故障受油器灯泡贯流式机组受油器-转子-转轮耦合振动模型,对比分析了有无故障受油器系统弯扭耦合状态下振动特性的差异,对系统在励磁电流、转子质量偏心及转轮质量偏心变化时各自的非线性振动特性进行了讨论。结果表明:故障受油器的出现加大了转子、转轮非稳态运动范围,使系统产生不利振动进而引发故障;同运行工况及参数状态下的转子相较转轮表现出更大振幅强度,需引起重视。扭转自由度的加入加剧了转子振幅,增加了碰摩故障发生概率。此外,当转轮质量偏心发展到一定程度后,叶片处存在的不确定随机水力将使系统发生失稳现象。研究结果可为灯泡贯流式机组安全运行及稳定性分析提供有益借鉴。

基于齿轮微观修形的行星减速器减振降噪研究

为改善某工厂的全自动攻丝机用行星齿轮减速器的振动噪声问题,并提升攻丝机的攻丝精度和使用寿命,对全自动攻丝机用减速器进行传动接触斑点试验,并利用Romax软件对减速器进行仿真,试验与仿真分析结果显示啮合齿轮副存在明显偏载问题。针对上述分析,提出基于遗传算法的齿向修形、渐开线修形及齿廓修形等复合齿轮微观修形优化方案;对修形优化后减速器重新建模仿真,并搭建行星齿轮减速器振动、噪声检测试验台,对修形前后减速器样机进行试验测试。结果表明:修形后减速器啮合时的偏载问题得到明显改善,齿面峰值载荷降低11.75%,最大接触应力降低29.62%,传动误差降低35.71%,减速器整体的振动噪声显著降低。

基于复合梁结构的压电-电磁能量收集器研究

能量收集器是解决复杂环境下为无线传感器网络节点供能问题的有效方法之一。针对传统收集器的共振频率高、频带窄等缺陷,设计了一种基于复合梁结构的压电-电磁式能量收集器,并进行了动力学分析与实验研究。首先对该结构进行理论模型建模,建立动力学方程,验证了其结构合理性。之后将该结构与其他传统压电结构进行对比研究,分析了收集器的动力学特性以及发电性能,优化结构参数,并进行了实验验证。研究发现通过复合梁与电磁单元的引入,收集器的工作频带得到了拓宽,改善了其发电性能,有效地使得该结构的一阶与二阶共振频率靠近。实验结果表明:负载电阻为10 kΩ、磁铁线圈间距为7 mm时,该复合梁压电电磁结构收集器具有最优的输出特性,其最大输出功率为20.17 mW,有效工作带宽约为13.40 Hz。

超声椭圆振动切削技术及装置应用研究现状及进展

首先,阐述了超声椭圆振动切削技术、原理及其装置特点,着重论述了装置各构成部分的特点及其主要应用类型与材料。其次,分析了国内外学者在双激励、单激励方式下实现纵弯、纵扭、双弯曲和弯扭等复合超声振动装置结构设计及其优化方面的研究成果与进展,并且比较了超声椭圆振动切削与传统加工在加工性能、工件表面质量和加工精度等方面的加工优势与适用范围,以及不同超声振动装置在各切削加工中所能获得的加工效果。最后,对超声椭圆振动切削装置的发展趋势进行了总结和展望,指出该装置发展将朝着结合能场的方向发展。

钛合金超声椭圆—低频扭转复合振动攻丝实验研究

为提高TC4钛合金小螺纹孔的攻丝效率,通过研制双弯复合超声椭圆振动换能器并进行超声椭圆—低频扭转复合振动攻丝实验,探讨了超声椭圆振动攻丝的特点以及低频扭转振动参数对复合振动攻丝的影响。实验结果表明,与低频扭转振动攻丝相比,复合振动攻丝在所选参数范围内能够降低约16%的攻丝扭矩,且在保持攻丝扭矩基本不变的前提下加工效率提高约1倍;低频扭转振动的净切削量越小,回退量越大,主轴转速越低,复合振动攻丝中超声椭圆振动发挥的作用越明显。

三轴转动惯量的振复摆与扭摆法协同测量比例法

空间飞行体在进行三轴转动惯量测量时需要分别沿3个正交方位做圆周摆动,为减少方位调整次数,提出基于振复摆与扭摆法的协同测量比例法。描述了该方法的测量机构,推导了比例法全因计算公式和近似计算公式;对该方法进行了误差分析,并与扭摆法进行了对比;采用模拟件作为测量对象,对提出的测量方法进行了实验研究。实验结果表明:J_(z)/J_(y)小于1.02时,协同比例法的全因计算和近似计算精度基本相同且与扭摆法基本相当;J_(z)/J_(y)大于1.02时,只能采用协同比例法全因计算公式,同时该方法解决了带翼飞行体三轴转动惯量测量的难题;协同比例法与前期提出的协同差值法组成了完整的测量体系,可以满足一定类型的回转体和带翼异形体三轴转动惯量测量需求。