Effect of ultrasonic and mechanical vibration treatments on evolution of Mn-rich phases and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys

Effects of ultrasonic vibration(UV)and mechanical vibration(MV)on the Mn-rich phase modification and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys were investigated.The results show that the UV and UV+MV treatments can significantly refine and fragmentize the microstructures.In addition,UV treatment can significantly passivate the primary Mn-rich Al15Mn3Si2 intermetallics.The formation mechanisms of refinement and passivation of the grains and non-dendrite particles were discussed.Compared with the gravity die-cast alloys,the UV and UV+MV treated alloys exhibit improved tensile and creep resistance at room and elevated temperatures.These results can be attributed to the refinement of theα(Al)grains and the secondary intermetallics,the increased proportion of refined heat-resistant precipitates,and the formation of nano-sized Si particles.The ultimate tensile strength of the UV treated alloys at 350℃ exceeds that of commercial piston alloys.This indicates the high application potential of the developed piston alloys in density diesel engines.

Asymmetric vibration characteristics of two-cylinder four-stroke single-piston hydraulic free piston engine

The structure and working principle of a two-cylinder four-stroke single-piston hydraulic free piston engine(HFPE) were introduced. The basic vibration equation of free piston assembly(FPA) was established based upon the energy conversion between the injected fuel and the friction together with the load. Both the theoretical and numerical results show that the vibration system of FPA is a nonlinear conservative autonomous system in one cycle. The FPA vibration is symmetric with constant amplitude when FPA is only driven by the compression pressure in the compression accumulator and that in the combustion chamber. When considering the friction and load, FPA could still achieve a stable vibration after a few cycles' adjustment whether the input energy is equal to the consumed energy or not. The vibration characteristics are different when FPA vibrates in the compression stroke and the expansion stroke, which is the unique feature of the single-piston HFPE.

Research on Coupling Transfer Characteristics of Vibration Energy of Free Piston Linear Generator

In order to clarify the mechanism and main influencing factors of the vibration energy coupling transmission with a dual-piston structure,a thermodynamic and dynamic coupling model of the free piston linear generator(FPLG)was established.The system energy conversion,vibration energy coupling transmission,and influencing factors were studied in detail.The coupling transmission paths and the secondary influence mechanism from in-cylinder combustion on vibration energy transmission were obtained.In addition,the influence of the movement characteristics of the dual-piston on the vibration energy transmission was studied,and the typical parameter variation law was obtained,which provides theoretical guidance for the subsequent vibration reduction design of the FPLG.

Research on two-dimensional fluid vibration axial transmission path model of axial piston pump

High speed and high pressure can enhance the vibration of axial piston pump. A fluid vibration transmission law of axial piston pump is studied in this paper. According to harmonic response analysis results, a transmission path analysis is used to establish a two-dimensional fluid vibration transmission path model in the vertical plane, which has characteristics of multi excitation sources, multi-path and multi-receptors. Model parameters are obtained by experimental and numerical analysis. Matlab is used to solve the model, and acceleration vibration response of three shells is got. To reduce the effect of mechanical vibration, the surface acceleration of pump is tested under low speed condition. Results show that the model can accurately reveal transmission law of fluid vibration and the accuracy is more than 90%. The research lays a foundation for exploring vibration transmission law and vibration control.

Study of Fault Diagnosis in Bend Axis Piston Pump

On the basis of theoretical analysis and experimental rerearck, the vibration characteristics of the ZB1-107 bend axis piston pump that is wldely ed in mining machinery is studied in the paper, and the study provides the basis for pump fault diagnesis. The vibration signals of the rault-rree pump and tbe faulty pump have been compared in frequency domaln and it is round that tbere is obvious differeuce in their vibration frequency spectra. The experimentol results demonstrate that the raults, such as port plate wear and tear and the looseness or ball joint or the conuecting rod, can be effectively detected through vibration analysis.

基于ADAMS/Vibration的微型摆式内燃机的振动分析

振动对微型摆式内燃机的正常运转具有很大的危害。将微型摆式内燃机的振动简化为二自由度对称质量—弹簧系统,通过机械系统动力学分析软件ADAMS建立内燃机振动的虚拟样机模型,首先利用ADAMS/Vibration求解系统各阶固有频率和模态主振型,并利用MATLAB软件计算出各工作阶段的压力随时间的变化,赋予模型激励力,利用ADAMS/Vibration对其进行强迫振动仿真分析,并绘制频率响应曲线,以验证其响应是否在所要求的范围之内。

Adaptive sensitive frequency band selection for VMD to identify defective components of an axial piston pump

The underlying study investigates single valued neutrosophic entropy based adaptive sensitive frequency band selection for variational mode decomposition(VMD)for the purpose of identifying defective components in an axial pump.The proposed methodology is applied in the following steps.First,VMD is applied for decomposing vibration signals into various frequency bands,called as modes.After computing energy of each VMD,the lower(minimum)and upper(maximum)bounds from these energy readings are extracted for defect conditions,such as outer race,inner race,worn piston,faulty cylinder and valve plate,and blocked hole of the piston.Thereafter,energy interval ranges are obtained and further converted into the form of single valued neutrosophic sets(SVNSs).Then,the proposed neutrosophic entropy measure is deployed for quantifying the non-linear connection between each bearing defect conditions and various frequency bands.The mode having maximum neutrosophic entropy value is designated to the“most sensitive”frequency band.Thereafter,envelope demodulation is applied to the most sensitive selected frequency band for finding defective components.The proposed neutrosophic entropy and VMD based methodology is effective in providing a better insight for selecting suitable frequency band for carrying out envelope demodulation in comparison to existing methods.

A new closed-form method for inertia force and moment calculation in reciprocating piston engine design

The piston crank mechanism is an important component of a reciprocating piston engine. It is an inherent vibration system, and as such, the calculation of unbalance quantity is a critical procedure in balancing mechanism design, which is adopted to balance inertia loading. The traditional method usually applies a Taylor series expansion with the crank-conrod ratio, then a Fourier transform with the crank angle. The Taylor expansion generally ignores the influence on calculations resulting from the high order terms. However, the high order terms of the Taylor expansion will also contribute to the low order terms in the Fourier series. This will induce poor precision in the inertia loading calculation, especially in a high crank-conrod ratio engine. Thus, this paper proposes a new closed-form method, which only adopts a Fourier transformation for the calculation. The coefficients of the Fourier transformation terms contain the contributions of all order terms of the crank-conrod ratio. Therefore, we named it as a closed-form method. Compared with the traditional method, the closed-form method improves the numerical accuracy of the secondary reciprocating inertia force by 1.5%–4%, when the crank-conrod ratio varies from 0.25 to 0.4. Using this new closedform method to design a balancing mechanism, the primary and secondary reciprocating inertia forces can be completely balanced. For an engine, where the primary and secondary inertia forces are balanced, the ratio of the residual inertia force to the total inertia force using the traditional method is 1.5%, while the ratio decreases to 0.5% using the closed-form method. The closed-form method is independent of engine configurations, including centric and eccentric engines, and single and multicylinder engines. Examples of applications using the proposed method are provided.

活塞压缩机整机振动分析与试验研究

为验证新设计的活塞压缩机整机运转的可靠性,对压缩机进行有限元模态仿真分析和临界振动响应测试。首先建立活塞压缩机的三维模型,并对其进行合理优化,设置工作边界条件后,完成有限元模态仿真分析,获得压缩机在此条件下的整机临界振动响应频率理论分析结果。然后对压缩机整机进行临界振动响应测试,获得压缩机前六阶的实时工作模态。试验结果与有限元模态分析结果对比分析表明,二者存在一些误差,但规律一致,整机不会发生破坏性临界共振现象。

机体振动信号时频特性与燃烧压力相关性分析

为了探明机体振动信号与缸内燃烧状态间的相关性,本文通过改变转速、转矩、润滑油温度及配缸间隙形成不同的燃烧状态,利用连续小波变换算法得到了振动信号时频域特性,并与燃烧压力峰值进行对比分析。结果表明:随转速增加,燃烧压力峰值出现波动,8 kHz以上成分的能量总体呈增加的趋势;随转矩增加,燃烧压力峰值及振动信号的能量均增加;随润滑油温度升高,20 kHz以上主要频率成分的能量增加;随配缸间隙增加,10kHz以上频率成分的能量总体呈增加的趋势。

Numerical modeling techniques for noise emission of free railway wheels

In this article,we consider the numerical prediction of the noise emission from a wheelset in laboratory conditions.We focus on the fluid-structure interaction leading to sound emission in the fluid domain by analyzing three different methods to account for acoustic sources.These are a discretized baffled piston using the discrete calculation method(DCM),a closed cylindrical volume using the boundary element method(BEM)and radiating elastic disks in a cubic enclosure solved with the finite element method(FEM).We provide the validation of the baffled piston and the BEM using measurements of the noise emission of a railway wheel by considering ground reflections in the numerical models.Selected space-resolved waveforms are compared with experimental results as well as with a fluid-structure interaction finite element model.The computational advantage of a discretized disk mounted on a baffle and BEM compared to FEM is highlighted,and the baffled pistons limitations caused by a lack of edge radiation effects are investigated.

斜轴式柱塞马达振动和噪声特性试验分析

为获得不同工况下斜轴式柱塞马达内部的激振源和噪声源,搭建其振动与噪声试验平台,在半消声室外通过数据采集系统对马达的振动和噪声信号进行采集和分析。试验结果表明:斜轴式柱塞马达的振动烈度与噪声等级随马达的转速与压力的增加而增大,且不同工况下马达内部的主要激振源和噪声源不同。在同一压力下,当转速从500 r/min增加到1200 r/min时,马达外壳表面的最大振幅位置从壳体转移到后端盖;在同一转速下,当压力从5 MPa增加到15 MPa时,马达内部的主要噪声源从主轴的偏心与不平衡转变为由配流冲击与流量脉动引起的压力脉动。

冲击回转钻孔过程振动响应时频特征与岩石力学性质相关性研究

冲击回转钻孔过程中产生的振动信号往往蕴含着丰富的岩石力学信息,通过振动信号判别岩石力学性质缺少定量研究。通过工程实例采集了冲击回转钻孔过程的三向振动信号,利用钻杆位移曲线提取纯钻进过程信号,通过小波变换消除噪声,分析了钻孔过程振动响应时域、频域和时频域特征,引入取决于概率密度函数形状的幅值域参数,找出了具有代表性的特征值和特征频率,通过岩石力学试验结果分析了钻孔过程振动时频特征与岩石力学性质的相关性。结果表明:三向振动信号中反映振动强度平均水平的均值、标准差、有效值随岩石单轴抗压强度的增加而增加,波峰因子、冲击因子和裕度因子这些反映冲击信号占比的指标随着岩石单轴抗压强度的增加而减小;钻杆轴向的振动信号均值、标准差、有效值、波峰因子、冲击因子和裕度因子均与岩石单轴抗压强度表现出良好的线性关系,通过这些时域特征值预测岩石强度是可行的;钻杆轴向特征频率和钻头冲击频率相当,垂直于钻杆方向的特征频率表现出较大差异,在均一地层条件下,时频域分析结果表明特征频率在钻孔过程中基本保持不变;垂直于钻杆方向的特征频率与岩石单轴抗压强度表现出非线性关系,可结合钻进速度确定岩石的强度。

一种基于优化VMD-CWT-CNN的柱塞泵配流盘磨损状态识别方法

为解决一维振动信号难以充分挖掘表达状态特征信息以及柱塞泵配流盘磨损早期识别问题,基于卷积神经网络(Convolutional neural networks,CNN)优秀的图像处理能力,提出了一个优化VMD-CWT-CNN模型。首先,采用连续小波变换(Continuous wavelet transform,CWT)对信号进行预处理,得到信号的二维时频图,作为CNN模型的一路输入,将状态识别问题转化为CNN图像识别问题。其次,基于相关系数对变分模态分解(Variational mode decomposition,VMD)参数优化后,利用优化VMD对振动信号进行预处理,再以相关系数和峭度值最大为优选原则,甄选出三组蕴含故障特征的本征模态函数(Intrinsic mode function,IMF),将其重组为三通道一维信号,作为CNN模型的另一路输入。最后,在CNN模型中将两路信息汇聚并得到柱塞泵配流盘磨损状态识别分类结果。实验中,此方法分别采用优化VMD和CWT对振动信号预处理,再结合CNN对磨损状态进行分类。实验结果表明,该方法对于配流盘磨损的三种状态的识别效果显著优于单路输入的CNN模型以及典型的深度学习方法和机器学习分类器。因此,优化的VMD-CWT-CNN方法可以更准确地实现柱塞泵配流盘磨损状态识别。

机体表面振动信号影响因素关联性分析

为了研究机体表面振动信号各影响因素的影响规律,在不同转速、转矩、润滑油温度及配缸间隙下,对比分析振动信号的峰值、方差、标准差及均方根等4个时域参数以及小波包分解得到的各频段能量的变化趋势。结果表明:随着转速的升高,燃烧压力峰值出现波动,在活塞惯性力的主导作用下,振动信号时域特征参数及频段5以上频率成分的能量呈增加的趋势;燃烧压力峰值随着转矩的增加而增大,振动信号时域特征参数及各频段能量均呈增加的趋势;随着润滑油温度的升高,在润滑油阻尼及燃烧压力的双重作用下,振动信号时域特征参数幅值整体呈降低的趋势,频段12以上频率成分的能量呈增加的趋势;随着配缸间隙的增加,密封性降低导致燃烧压力峰值减小,但由于活塞二次运动加剧,导致振动信号时域特征参数及频段5以上频率成分的能量呈现增加的趋势。

轴向柱塞泵非定常空化流激振动特性

针对轴向柱塞泵吸排油过程发生空化带来流体激振力大,甚至造成严重的局部气蚀破坏问题,使用用户自定义函数和动网格法对柱塞泵的动态运动过程进行模拟。通过柱塞泵空化流激振动特性实验,对比分析柱塞泵空化流激振动响应特征,获取轴向柱塞泵空化流动及其诱导振动的作用机理。结果表明:柱塞腔内气体体积分数随缸体转角变化呈周期性振荡,空化现象主要集中在泵的吸油区;当缸体转角处于吸排油交替区时,柱塞腔内压力场出现负压现象,气泡在流体射流的方向上扩散,形成明显的局部空化云;柱塞泵空化流激振动频谱与流体脉动载荷频谱重合,直接影响柱塞泵壳体振动的幅值,成为柱塞泵壳体振动响应的主要诱因。

液压柱塞马达的约束阻尼层降噪研究

液压柱塞马达在工作状态下振动噪声剧烈,针对削弱内部声振源和外部壳体结构优化的传统减振降噪方案设计难度大、优化成本高的问题,提出了在液压柱塞马达壳体敷设约束阻尼层的减振降噪方法。进行液压柱塞马达的动力学模型和液压模型耦合仿真,得到液压柱塞马达内部对壳体的振动激励。以振动激励作为载荷,结合强迫响应分析和基于模态声传递向量法的声压仿真,得到马达壳体的模态参与因子和声学板块贡献量,从而精确阻尼层敷设区域。通过对约束阻尼层进行有限元建模分析,研究阻尼层材料参数对振动抑制的影响,选择合适的阻尼层材料。在半消声室内对敷设约束阻尼层前后的液压柱塞马达进行多工况下平均声压级测试。结果表明:在峰值噪声频率下,约束阻尼层能将液压柱塞马达的噪声至少降低2 dB。

基于泵送频率的往复泵活塞故障诊断方法

为了确保往复式钻井泵的高质量运行,实施在线故障监测至关重要。从BW-250型钻井泵液力端的易损件入手,设计了试验探究钻井泵的振动信号的成分;通过对频率成分的分析,揭示了泵送频率幅值与活塞刺漏故障之间的关系,并依据机理提出了以泵送频率幅值作为诊断指标的钻井泵活塞故障检测方法,进一步结合最大相关峭度解卷积滤波及包络谱分析等方法从泵送频率处能量变化的角度,对活塞刺漏这一故障进行了诊断;结合实验室以及钻井现场采集的数据对该方法进行了验证,并将诊断结果同其他振动指标做了对比。结果表明,该方法对于往复泵活塞故障诊断的准确率为91.1%,相较于均方根诊断准确率提升了3.6%、相较于脉冲因子、裕度因子和峭度3种统计指标诊断准确率提升了9%以上。该方法取得了良好的结果,为往复泵活塞组件的故障诊断提出了一种较好的解决思路。

泵控马达液压系统压力拍振成因及其动态分析

针对液压系统中泵和马达的压力脉动频率相近时影响输出稳定性和负载工作可靠性的问题,采用AMESim多学科仿真软件对多能域耦合闭式液压系统进行物理建模,研究不同柱塞副间隙下拍振现象的规律特性。通过计算泵控马达液压系统的阻尼比及分析蓄能器模固有频率,提出利用蓄能器对压力拍振现象进行测试和分析。最后,通过搭建机电液一体化实验平台对仿真分析进行验证。理论分析和实验结果均表明:压力拍振对于压力信号和柱塞磨损等液压系统常见故障的故障特征有明显放大作用,蓄能器对于液压系统压力拍振幅值有明显的缓冲作用。

基于AMESim的多液缸合流式压裂泵流量脉动特性研究

传统的机械式压裂泵存在冲次高、冲程短、曲轴易于失效等问题,为此,提出了一种多液缸合流式液压驱动压裂泵,并对其产生流量脉动的机理进行了研究。首先,详细阐述了多液缸合流式压裂泵的工作原理,基于液压流体力学等理论,建立了多液缸合流式压裂泵的数学模型,并进行了理论分析;其次,采用AMESim仿真软件搭建了多液缸合流式压裂泵工作仿真模型,选择了合理的仿真参数设置,进行了变负载压力下的仿真研究;最后,对液压动力传递链中的活塞-柱塞运动特性、泵腔流量特性、输出流量和压力脉动特性进行了研究,并对仿真结果进行了分析。研究结果表明:在25 MPa工况下,多液缸合流式压裂泵的输出压力和流量脉动率分别为36.8%和20.61%,冲次只有42次/min,符合实际工况;多液缸合流式压裂泵输出流量脉动的主要原因是各组液缸的频繁换向、泵送行程和吸入行程的切换,导致活塞-柱塞做减速停止运动和加速启动运动。