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Displacement Response Reconstruction of Slender Flexible Structures Based on Cubic Spline Fitting Method 预览
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作者 HAN Qing-hua MA Ye-xuan +1 位作者 FENG Xin-xin XU Wan-hai 《中国海洋工程:英文版》 SCIE EI CSCD 2019年第2期226-236,共11页
How to reconstruct a dynamic displacement of slender flexible structures is the key technology to develop smart structures and structural health monitoring (SHM), which are beneficial for controlling the structural vi... How to reconstruct a dynamic displacement of slender flexible structures is the key technology to develop smart structures and structural health monitoring (SHM), which are beneficial for controlling the structural vibration and protecting the structural safety. In this paper, the displacement reconstruction method based on cubic spline fitting is put forward to reconstruct the dynamic displacement of slender flexible structures without the knowledge of modeshapes and applied loading. The obtained strains and displacements are compared with the results calculated by ABAQUS to check the method’s validity. It can be found that the proposed method can accurately identify the strains and displacement of slender flexible structures undergoing linear vibrations, nonlinear vibrations, and parametric vibrations. Under the concentrated force, the strains of slender flexible structures will change suddenly along the axial direction. With locally densified measurement points, the present reconstruction method still works well for the strain concentration problem. 展开更多
关键词 DISPLACEMENT RECONSTRUCTION CUBIC SPLINE FITTING slender flexible structures linear vibrations PARAMETRIC vibrations nonlinear vibrations
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Design of a tunable mass damper for mitigating vibrations in milling of cylindrical parts
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作者 Heng YUAN Min WAN Yun YANG 《中国航空学报:英文版》 SCIE EI CAS CSCD 2019年第3期748-758,共11页
Milling the free-end of cylindrical parts, which are vertically fixed on the machine table,often suffers from large chatter vibrations. This kind of phenomenon is harmful to the cutting process. Therefore, it is of gr... Milling the free-end of cylindrical parts, which are vertically fixed on the machine table,often suffers from large chatter vibrations. This kind of phenomenon is harmful to the cutting process. Therefore, it is of great importance to develop means to suppress these undesirable chatters.This paper proposes a new idea for designing a tunable mass damper(TMD) to reduce vibrations in milling of cylindrical parts. Frequency response function(FRF) of the milling system is derived to comprehensively reveal the influence of both the dynamic response of the machine tools and the TMD. Critical axial depth of cut, which is usually used to characterize the process stability, is formulated by considering the FRFs of both the milling system itself and the TMD. Maximization of critical axial depth of cut is taken as objective function, while kernel dynamic parameters of TMD,which are involved in the derived expression of critical axial depth of cut, are extracted as designable variables. Optimization procedure is carried out to adjust the parameters of TMD by using sequential quadratic programming algorithm. A series of experiments with a designed passive TMD validate that the design has a good performance in reducing vibrations and improving stability of milling process. 展开更多
关键词 Chatter MILLING MITIGATION of vibrations Stability TUNABLE MASS DAMPER (TMD)
不同振动特性参数对杏树振动响应的影响 预览
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作者 杨会民 散鋆龙 +3 位作者 陈毅飞 王学农 牛长河 侯书林 《农业工程学报》 EI CAS CSCD 北大核心 2019年第2期10-16,共7页
为研究振动时间、振动频率和振动激励点振幅等不同振动特性参数对杏树振动的影响,该文利用ANSYS软件对杏树进行了有限元建模分析;通过三因素三水平试验分析不同振动特性参数对杏树振动检测点的影响,利用Design Expert软件进行优化分析,... 为研究振动时间、振动频率和振动激励点振幅等不同振动特性参数对杏树振动的影响,该文利用ANSYS软件对杏树进行了有限元建模分析;通过三因素三水平试验分析不同振动特性参数对杏树振动检测点的影响,利用Design Expert软件进行优化分析,并进行实验室验证试验。杏树自由模态振动响应分析表明最佳杏树振动采收响应频率范围为0~20Hz;谐振动响应分析可知在最佳频率范围内,杏树振动激励点振幅为5、10和15mm时,同一频率下,随着激励振幅的增大,相同位置加速度增大,但振动曲线整体变化规律和趋势一致。试验分析可知,各因素影响检测点1和2加速度的强弱顺序一致:激励点振幅 >振动频率 >振动时间;各因素影响检测点3加速度的强弱顺序为:振动时间 >激励点振幅 >振动频率;建立3个检测点的响应方程,由下至上3个检测点的回归方程决定系数分别为0.9067、0.8793和0.9733;多目标参数优化结果为:振动时间7.207s,振动频率15Hz,激振点振幅10mm,通过验证试验可知由下至上各检测点加速度为10.4g、10.2g和9.3g,与优化值相近。该研究可为杏振动采收机械参数设计提供参考。 展开更多
关键词 振动 收获 机械化 振动响应试验
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Experimental investigation of combined vibrations for a hydrofoil-rod system at low Reynold numbers 预览
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作者 Ren-feng Wang Ke Chen +2 位作者 Francis Nobelesse Yun-xiang You Wei Li 《水动力学研究与进展:英文版》 SCIE EI CSCD 2019年第3期512-521,共10页
A hydrodynamic tunnel experimental investigation and analysis of vibration characteristics for a hydrofoil in a transient regime is considered. Tests are performed for NACA 0017 models with a non-uniform section at an... A hydrodynamic tunnel experimental investigation and analysis of vibration characteristics for a hydrofoil in a transient regime is considered. Tests are performed for NACA 0017 models with a non-uniform section at an angle of attack AOA = 5° and Reynolds numbers up to Re = 7.0 x 106. This study is related to a project design of experiments in a complex facility that involves several parameters. The analysis focuses on the vibrations of a hydrofoil for different values of the bracing stiffness kh, the torsional stiffness ka, and the locations of the elastic axis a and of the center of gravity xa . The structural bracing response is investigated via measurements of the displacement of the free tip section of the hydrofoil using a three-axis acceleration sensor, and the torsional response of the structure is analyzed via measurements of displacements with single-axis acceleration sensors. The hydrofoil is made of reinforced plastics without flexibility, and elastic functions are performed by a spring support mechanism combined with a torsional structure. The study shows that an increase of the velocity results in different behaviors of the bracing and torsional amplitudes. Another notable result of the study is that the emergence of transition occurs simultaneously with additional peaks and changes of vibration amplitudes. 展开更多
关键词 Vibrations LIFTING BODIES transition LAMINAR separation BUBBLES
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Wind-induced instabilities and monitoring of wind turbine 预览
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作者 Isaac Wait Zhaohui (Joey) Yang +1 位作者 Gang Chen Benjamin Still 《地震工程与工程振动:英文版》 SCIE EI CSCD 2019年第2期475-485,共11页
This paper presents real-time monitoring data and analysis results of the non-stationary vibrations of an operational wind turbine. The advanced time-frequency spectrum analysis reveals varied non-stationary vibration... This paper presents real-time monitoring data and analysis results of the non-stationary vibrations of an operational wind turbine. The advanced time-frequency spectrum analysis reveals varied non-stationary vibrations with timevarying frequencies, which are correlated with certain system natural modes characterized by finite element analysis. Under the effects of strong wind load, the wind turbine system exhibits certain resonances due to blade passing excitations. The system also exhibits certain instabilities due to the coupling of the tower bending modes and blade flapwise mode with blade passing excitations under the variation of wind speed. An analytical model is used to elaborate the non-stationary and instability phenomena observed in experimental results. The properties of the nonlinear instabilities are evaluated by using Lyapunov exponent estimation. 展开更多
关键词 wind turbine condition MONITORING NON-STATIONARY vibrations INSTABILITIES whirl MODES WARM PERMAFROST
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Nonlinear Dynamical Responses of Rotary Cylindrical Shells with Internal Resonance
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作者 Yufei Zhang Jintang Liu Bangchun Wen 《固体力学学报:英文版》 SCIE EI CSCD 2019年第2期186-200,共15页
The nonlinear forced vibration response of a thin, elastic, rotary cylindrical shell to a harmonic excitation is investigated in this study. Nonlinearities due to the large-amplitude shell motion are considered by usi... The nonlinear forced vibration response of a thin, elastic, rotary cylindrical shell to a harmonic excitation is investigated in this study. Nonlinearities due to the large-amplitude shell motion are considered by using Donnelfs nonlinear shallow-shell theory, with consideration of the effect of viscous structural damping. Different from the conventional DonnclFs nonlinear shallow-shell equations, an improved nonlinear model without employing the Airy stress function is utilized to study the nonlinear dynamics of thin shells. The system is discretized using the Galerkin method, while a model involving two degrees of freedom and allowing for the traveling wave response of the shell is adopted. The method of harmonic balance is applied to study the nonlinear dynamic responses of the t wo-degree-of-freedom system. In addition, the st ability of steady-state solutions is analyzed in detail. Finally, results are given for exploring the effects of different parameters on the nonlinear dynamic response with internal resonance. 展开更多
关键词 CYLINDRICAL SHELLS ROTARY Nonlinear vibrations Internal RESONANCE DYNAMICAL response
细长偏心舱体振动试验夹具设计分析与验证 预览
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作者 杭超 燕群 张昕 《机械科学与技术》 CSCD 北大核心 2019年第2期322-328,共7页
振动试验是考核航空航天产品可靠性与环境适应性的重要手段。针对某大型细长偏心舱体的振动试验,介绍了振动试验的二自由度系统理论模型,然后采用配重法设计了其振动试验夹具,并通过有限元软件ABAQUS分析了夹具在自由状态和连接试验件... 振动试验是考核航空航天产品可靠性与环境适应性的重要手段。针对某大型细长偏心舱体的振动试验,介绍了振动试验的二自由度系统理论模型,然后采用配重法设计了其振动试验夹具,并通过有限元软件ABAQUS分析了夹具在自由状态和连接试验件状态的模态参数和随机振动响应。结果表明,该夹具自由状态的1阶固有频率为198.6Hz,连接试验件状态的1阶固有频率为202.1 Hz,最大放大因子为1.6,连接点加速度的最大偏差为31.4%,上述指标均符合振动试验夹具设计要求。最后用该夹具对细长偏心舱体进行了随机振动试验,试验控制平稳,偏差在容差范围内,验证了夹具设计的合理性。 展开更多
关键词 振动试验 夹具设计 模态分析 固有频率 随机响应分析
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Coupled Bending-Bending-Axial-Torsional Vibrations of Rotating Blades
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作者 Feng Liang Zhen Li +2 位作者 Xiao-Dong Yang Wei Zhang Tian-Zhi Yang 《固体力学学报:英文版》 SCIE EI CSCD 2019年第3期326-338,共13页
In this paper, the coupled bending-bending-axial-torsional free vibrations of rotating blades are investigated based on the Euler-Bernoulli beam model. The coupled partial differential equations governing flapwisc, ed... In this paper, the coupled bending-bending-axial-torsional free vibrations of rotating blades are investigated based on the Euler-Bernoulli beam model. The coupled partial differential equations governing flapwisc, edgewise, axial and torsional motions are derived by the Hamilton's principle, wherein three types of velocity-dependent terms, namely static centrifugal terms, dynamic centrifugal terms and gyroscopic coupling terms, are focused. The ordinary di& ferential equations are acquired by the Galerkin truncation, and the natural frequencies in all directions and complex mode shapes of the rotating blades are analyzed in detail. It is revealed that the three types of velocity-dependent terms have different effects on the natural frequencies. The natural frequencies are noticeably dependent on the rotating speed and preset angle, except for the axial vibration, which is almost immune to the preset angle. The complex modal motions are displayed by a series of positions of the central line and free-end cross section for different time instants, showing the coupled vibrations among different directions. 展开更多
关键词 Rotating BLADES COUPLED vibrations Gyroscopic coupling Complex MODES PRESET angle
指夹式玉米免耕精密播种机振动特性及对排种性能的影响 预览
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作者 王奇 朱龙图 +3 位作者 李名伟 黄东岩 贾洪雷 庄健 《农业工程学报》 EI CAS CSCD 北大核心 2019年第9期9-18,共10页
为研究2BMZ-2型指夹式玉米免耕精密播种机在免耕地表作业时的振动特性及振动对排种器排种性能的影响规律,建立了整机振动特性模型,求解其稳态振动响应;测试播种机在免耕地表作业时排种器振动特性。搭建振动排种试验台模拟田间作业振动环... 为研究2BMZ-2型指夹式玉米免耕精密播种机在免耕地表作业时的振动特性及振动对排种器排种性能的影响规律,建立了整机振动特性模型,求解其稳态振动响应;测试播种机在免耕地表作业时排种器振动特性。搭建振动排种试验台模拟田间作业振动环境,测试机械振动对排种器性能的影响规律,并运用高速摄像和与图像目标追踪技术研究籽粒落种运动规律。结果表明,播种机的振动特性主要决定于作业速度、地表及土壤情况和播种机的结构特性。播种机前进速度在 5~9 km/h 范围内,播种机振动能量的频率分布主要集中在低频段的 3~11 Hz;前进速度越大,振动加速度越大,但不影响振动能量的频率分布。机械振动对排种器充种性能无显著性影响,对播种性能具有显著性影响的试验指标为播种合格率、粒距纵向变异系数和粒距横向变异系数(P<0.05);试验因素对排种均匀稳定性影响的主次顺序为排种轴转速、振动加速度、振动频率;各试验因素的增大均使籽粒下落轨迹及落点更加离散、落种范围增大,且增大排种轴转速使落种点位置逐渐远离投种初始位置。该研究为免耕播种机指夹式排种器排种性能的提高提供了参考。 展开更多
关键词 振动 模型 机械化 玉米种植 免耕播种机 排种器 试验
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应用多参量和高斯过程分类的故障诊断方法 预览
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作者 王斌 崔宝珍 《机械科学与技术》 CSCD 北大核心 2019年第9期1380-1385,共6页
由于齿轮箱振动信号的非平稳非线性等问题加大了故障诊断的难度,本文提出了一种基于互补集合经验模态分解(CEEMD)和多尺度排列熵(MPE)、样本熵(SE)相结合的故障特征提取方法。首先对齿轮箱振动信号进行互补集合经验模态分解,并根据相关... 由于齿轮箱振动信号的非平稳非线性等问题加大了故障诊断的难度,本文提出了一种基于互补集合经验模态分解(CEEMD)和多尺度排列熵(MPE)、样本熵(SE)相结合的故障特征提取方法。首先对齿轮箱振动信号进行互补集合经验模态分解,并根据相关系数原则对各模态分量进行筛选和重构,再利用多尺度排列熵对筛选出的模态分量进行特征提取,同时对重构后的信号提取其样本熵作为特征值;最后将提取出的多种故障特征融合输入到高斯过程分类器中进行实验验证,实验结果表明该方法提取齿轮箱振动信号的故障特征是有效的,高斯过程分类能快速准确地分辨出故障结果。 展开更多
关键词 齿轮箱 互补集合经验模态分解 多尺度排列熵 高斯过程分类 故障诊断
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Effect of ultrasonic vibration-assisted laser surface melting and texturing of Ti-6Al-4V ELI alloy on surface properties
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作者 Sourabh Biswas S. Habib Alavi +2 位作者 Bhishma Sedai Frank D. Blum Sandip P. Harimkar 《材料科学技术学报:英文版》 SCIE EI CAS CSCD 2019年第2期295-302,共8页
Ultrasonic vibration-assisted laser surface processing that involves application of vertical ultrasonic vibrations to the Ti-6 Al-4 V alloy substrates while being irradiated with a CO2 laser was performed for the deve... Ultrasonic vibration-assisted laser surface processing that involves application of vertical ultrasonic vibrations to the Ti-6 Al-4 V alloy substrates while being irradiated with a CO2 laser was performed for the development of laser melted and textured surfaces with potential applications in biomedical implants.The laser processing resulted in very consistent repeating undulating grooved surfaces, and the undulations were significantly more pronounced in the samples processed with higher ultrasonic power outputs.The phase evolution, studied by x-ray diffraction, confirmed that the laser processing triggered transformation of globular α→ acicular α and martensitic α’ as well as increased amounts of retained α phases,which were also reflected in the microscopic analysis. The surface texture developed by laser processing resulted in increased surface wettability with increasing ultrasonic power output. The textured surfaces exhibited marked decrease in coefficients of friction during sliding wear testing performed under simulated body fluid due to lubricant entrainment within the textured grooves. The texturing also resulted in significant reduction in surface contact area during the wear process, which considerably reduced the overall wear rates due to abrasive wear. 展开更多
关键词 LASER TEXTURING LASER MELTING ULTRASONIC vibrations WEAR
Free vibration analysis of a spinning piezoelectric beam with geometric nonlinearities 预览
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作者 Wei Li Xiao-Dong Yang +2 位作者 Wei Zhang Yuan Ren Tian-Zhi Yang 《力学学报:英文版》 SCIE EI CAS CSCD 2019年第4期879-893,共15页
The linear and non-linear free vibrations of a spinning piezoelectric beam are studied by considering geometric nonlinearities and electromechanical coupling effect. The non-linear differential equations of the spinni... The linear and non-linear free vibrations of a spinning piezoelectric beam are studied by considering geometric nonlinearities and electromechanical coupling effect. The non-linear differential equations of the spinning piezoelectric beam governing two transverse vibrations are derived by using two Euler angles transformation and extended Hamilton principle, wherein an additional piezoelectric coupling term and different linear terms are present in contrast to the traditional shaft model. Linear frequencies are obtained by solving the standard eigenvalues of the linearized system directly, and the non-linear frequencies and non-linear complex modes are achieved by using the method of multiple scales. For free vibrations analysis of a spinning piezoelectric beam, the non-linear modal motions are investigated as forward and backward precession with different spinning speeds. The responses to the initial conditions for such a gyroscopic system are studied,and a beat phenomenon is found, which are then validated by numerical simulation. The influences of some parameters such as electrical resistance, rotary inertia and spinning speeds to the non-linear dynamics of a spinning piezoelectric beam are investigated. 展开更多
关键词 SPINNING PIEZOELECTRIC BEAM Free vibrations NON-LINEAR frequencies Complex MODES
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A Novel Wake Oscillator Model for Vortex-Induced Vibrations Prediction of A Cylinder Considering the Influence of Reynolds Number 预览
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作者 GAO Xi-feng XIE Wu-de +2 位作者 XU Wan-hai BAI Yu-chuan ZHU Hai-tao 《中国海洋工程:英文版》 SCIE EI CSCD 2018年第2期132-143,共12页
It is well known that the Reynolds number has a significant effect on the vortex-induced vibrations(VIV)of cylinders.In this paper,a novel in-line(IL)and cross-flow(CF)coupling VIV prediction model for circular cylind... It is well known that the Reynolds number has a significant effect on the vortex-induced vibrations(VIV)of cylinders.In this paper,a novel in-line(IL)and cross-flow(CF)coupling VIV prediction model for circular cylinders has been proposed,in which the influence of the Reynolds number was comprehensively considered.The Strouhal number linked with the vortex shedding frequency was calculated through a function of the Reynolds number.The coefficient of the mean drag force was fitted as a new piecewise function of the Reynolds number,and its amplification resulted from the CF VIV was also taken into account.The oscillating drag and lift forces were modelled with classical van der Pol wake oscillators and their empirical parameters were determined based on the lock-in boundaries and the peak-amplitude formulas.A new peak-amplitude formula for the IL VIV was developed under the resonance condition with respect to the mass-damping ratio and the Reynolds number.When compared with the results from the experiments and some other prediction models,the present model could give good estimations on the vibration amplitudes and frequencies of the VIV both for elastically-mounted rigid and long flexible cylinders.The present model considering the influence of the Reynolds number could generally provide better results than that neglecting the effect of the Reynolds number. 展开更多
关键词 vortex-induced vibrations REYNOLDS number WAKE OSCILLATOR MODEL CYLINDER
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振动方式和频率对杏树振动采收响应的影响 预览 被引量:2
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作者 散鋆龙 杨会民 +3 位作者 王学农 牛长河 郭文松 侯书林 《农业工程学报》 CSCD 北大核心 2018年第8期10-17,共8页
为了研究受到不同振动激励后杏树的响应状态以及杏树最佳振动采收频率,该文建立了单偏心式和对称双偏心式振动激励下杏树响应模型以及杏树-采收机动力学模型;分析杏树受振动激励后,不同位置的振动响应状态。理论分析与试验表明,杏树受... 为了研究受到不同振动激励后杏树的响应状态以及杏树最佳振动采收频率,该文建立了单偏心式和对称双偏心式振动激励下杏树响应模型以及杏树-采收机动力学模型;分析杏树受振动激励后,不同位置的振动响应状态。理论分析与试验表明,杏树受单偏心式振动激励时,主要表现为扭转振动,夹持位置运动轨迹为圆形;受对称双偏心式振动激励时,主要表现为弯曲振动,夹持位置在水平方向上做往复运动,运动轨迹为直线。利用LabView振动测试软件,通过沿杏树主干安装的加速度传感器,检测杏树不同位置振动加速度变化。分析表明,振动由夹持位置沿树干向上传递,同时获得不同位置的加速度振动响应曲线;通过MATLAB对达到振动稳态后0.1s内数据进行傅里叶拟合分析表明,各级枝干检测点均做周期性简谐运动,得到不同位置加速度拟合曲线及振动响应函数;通过对0~50Hz加速度频谱分析表明,杏树在11.56Hz振动激励时,各检测点加速度值最大。该研究可为林果振动收获机械设计与优化提供参考。 展开更多
关键词 振动 模型 收获 果树 动态响应
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荔枝树枝能量传递特性与去梗式振动采摘作业参数 预览
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作者 李斌 陆华忠 +4 位作者 吕恩利 李君 丘广俊 尹鸿超 马亚坤 《农业工程学报》 CSCD 北大核心 2018年第8期18-25,共8页
为评价荔枝去梗式振动采摘效果,开展了树枝能量传递特性研究,利用一种动-定梳排组合式采摘机构进行了荔枝采摘试验与品质对比分析。研究结果表明,激振点在靠近外侧树冠位置的分支时,传递到末端枝条的振动能量衰减少,动-定梳排组合采摘... 为评价荔枝去梗式振动采摘效果,开展了树枝能量传递特性研究,利用一种动-定梳排组合式采摘机构进行了荔枝采摘试验与品质对比分析。研究结果表明,激振点在靠近外侧树冠位置的分支时,传递到末端枝条的振动能量衰减少,动-定梳排组合采摘方式通过激励相对固定的挂果枝条可有效利用振动能量。综合加权评分法确定的采摘机构的最佳作业参数条件:梳排振动频率为26.67Hz,定梳排间距为20mm,动梳排摆动角度为40.,试验测定的生产率为4.1kg/min,破损率为5.05%。振动采摘和人工采摘2种采摘方式的荔枝色差值、可溶性固形物含量和可滴定酸含量在8d的贮藏期内无显著性差异,即振动采摘未对荔枝果实品质产生不良影响。该研究可为荔枝采收机械的设计与优化提供参考。 展开更多
关键词 振动 收获 机械化 荔枝 能量传递特性 去梗式采摘 采后品质
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秸秆捡拾打捆机振动去土作业参数优化 预览 被引量:3
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作者 付乾坤 付君 +2 位作者 陈志 程超 任露泉 《农业工程学报》 CSCD 北大核心 2018年第8期26-33,共8页
为解决秸秆捡拾打捆后含土率高的问题,该文提出通过振动方式去除粘附和夹杂在黄贮秸秆中的土壤,以提高秸秆的后续利用价值。通过试验台设计和高速摄像分析,发现了秸秆振动去土规律;以土壤去除率和秸秆损失率为指标,以摘穗后整株铺放和... 为解决秸秆捡拾打捆后含土率高的问题,该文提出通过振动方式去除粘附和夹杂在黄贮秸秆中的土壤,以提高秸秆的后续利用价值。通过试验台设计和高速摄像分析,发现了秸秆振动去土规律;以土壤去除率和秸秆损失率为指标,以摘穗后整株铺放和切碎铺放的秸秆为研究对象,对各参数进行了单因素试验,建立了振动去土试验边界条件;通过三元正交多项式回归试验,在振动频率、振幅和振动时长三因素下,分析了2种秸秆物料的土壤去除率和秸秆损失率的变化规律。获得了黄贮秸秆振动去土的最优组合为:整株铺放秸秆振幅15mm、振动频率4.5Hz、振动时长14s,切碎铺放秸秆振幅20mm、振动频率4Hz、振动时长12s,并通过台架试验进一步验证了最优组合,试验结果与预测值误差较小,参数模型可靠。该研究为改进黄贮秸秆捡拾打捆机的作业机理、优化关键零部件设计、提高综合作业质量,提供了理论基础和试验参考。 展开更多
关键词 农业机械 振动 优化 秸秆 捡拾打捆 去土 试验
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振动深松机多组振动深松铲自平衡性能及仿真分析 预览 被引量:2
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作者 孙亚朋 董向前 +3 位作者 宋建农 王继承 刘彩玲 徐光浩 《农业工程学报》 CSCD 北大核心 2018年第4期92-99,共8页
振动深松具有减阻的优势,但振动对拖拉机及驾驶员的不利影响制约其推广,该文对振动深松机多组振动深松铲进行自平衡性能分析。在优化试验中,多组深松铲振动作业时的剧烈振动易造成试验设备损坏,仿真试验可避免危险工作环境下的实车试验... 振动深松具有减阻的优势,但振动对拖拉机及驾驶员的不利影响制约其推广,该文对振动深松机多组振动深松铲进行自平衡性能分析。在优化试验中,多组深松铲振动作业时的剧烈振动易造成试验设备损坏,仿真试验可避免危险工作环境下的实车试验。对拖拉机-振动深松机系统进行受力分析,并基于ADAMS建立其仿真模型,建模过程包括导入三维模型、定义轮胎与地面之间接触力和摩擦力等。理论与仿真分析相互验证,得到拖拉机后轮所受支持力均值分别为27.8、26.4 kN,误差为1.4 kN,并且二者主振动曲线变化趋势一致。采用加权加速度均方根值评价振动对驾驶员的影响。通过MATLAB编程,利用功率谱密度函数,计算得到驾驶座质心总加权加速度均方根值。利用Design-Expert软件设计试验并优化得到6组振动影响较小的四组振动松土铲作业初始相位角组合,减振比率超过90%,实现了振动深松机作业时的自平衡。 展开更多
关键词 农业机械 振动 计算机仿真 深松 自平衡 ADAMS
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振动与波浪二级分离马铃薯收获机改进 预览 被引量:2
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作者 魏忠彩 李洪文 +4 位作者 孙传祝 李学强 刘文政 苏国粱 王法明 《农业工程学报》 CSCD 北大核心 2018年第12期42-52,共11页
针对当前马铃薯机械化收获环节存在的破皮率和伤薯率较高等问题,通过设置振动分离段和波浪分离段、基于振动与波浪二级分离改进了一种马铃薯收获机,并分析了振动与波浪二级分离条件下的分离筛及薯块运动特征。单因素试验表明,收获速度为... 针对当前马铃薯机械化收获环节存在的破皮率和伤薯率较高等问题,通过设置振动分离段和波浪分离段、基于振动与波浪二级分离改进了一种马铃薯收获机,并分析了振动与波浪二级分离条件下的分离筛及薯块运动特征。单因素试验表明,收获速度为0.726 m/s时,单位时间内挖掘的薯土混合物较少,易导致薯块疲劳累积损伤,当收获速度为1.167m/s时分离筛的分离负担加大,土壤和杂质分离效率降低,导致明薯率下降;分离筛运行速度从1.52提高至2.80 m/s时,破皮率和伤薯率呈先降低后增大的趋势,但明薯率自99.8%下降至96.4%;振动强度由无振动增加到强烈振动时,明薯率提高3.3%,但破皮率和伤薯率均有较大幅度的增加;峰谷高差自40-40 mm增大到200-200 mm时,明薯率由97.2%升高至99.8%,但其破皮率和伤薯率均有所升高。正交试验表明:破皮率和伤薯率受收获速度和振动强度的影响规律基本一致;收获速度和振动强度对破皮率和伤薯率的影响较显著(P〈0.05),振动强度和峰谷高差对明薯率的影响较显著(P〈0.05)。该文为马铃薯收获机的研发优化以及薯土分离效率和收获品质的综合控制提供了技术参考。 展开更多
关键词 振动 机械化 收获 马铃薯 混合分离 破皮率 伤薯率 运动特征
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玉米起茬机构的强度及振动特性分析与试验 预览
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作者 张佳喜 杨程 +2 位作者 张丽 蒋永新 王春耀 《农业工程学报》 CSCD 北大核心 2018年第12期72-78,共7页
玉米地膜污染治理中,玉米根茬较大、根系中大量气生根与地膜穿插在一起,致使玉米地膜回收较为困难,该文设计采用圆盘式起茬机构将玉米根茬起出,进行地膜回收,可有效解决玉米大根茬影响地膜回收的问题。但在双圆盘起茬过程中,田间地面不... 玉米地膜污染治理中,玉米根茬较大、根系中大量气生根与地膜穿插在一起,致使玉米地膜回收较为困难,该文设计采用圆盘式起茬机构将玉米根茬起出,进行地膜回收,可有效解决玉米大根茬影响地膜回收的问题。但在双圆盘起茬过程中,田间地面不平引起的随机激励和圆盘刀等激励产生的振动频率接近起茬机构固有频率时,将引起共振加速,影响整机结构动态特性与可靠性。采用振动测试与模态分析方法,分析起茬机构田间振动特性,避免机构的共振影响起茬工作。首先,进行模态分析,提取机构固有频率与振型;其次,通过整机田间动态信号测试,进行动态数据采集分析,每个测点的振动响应进行快速傅里叶变换的频谱分析,测点位置的主要振动频率为19.53 Hz,与模态分析的一阶固有频率38.176 Hz相差较大,不在同一频率范围内,机构不会产生共振现象发生。根据胡克定律在一定的比例极限范围内应力与应变成线性比例关系,对田间动态数据进行计算得到机构的受力情况,计算受力最大处的测点4应力为227.94 MPa,小于普通炭钢的屈服强度为235 MPa,满足强度要求。该研究可避免起茬装置的共振发生,可为农机装备的振动特性分析与强度设计提供参考。 展开更多
关键词 农业机械 振动 有限元方法 大根茬 残膜回收 圆盘 模态分析
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拖拉机行星齿轮箱故障响应特性动力学仿真及验证 预览
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作者 史丽晨 李坤 +1 位作者 王海涛 刘洋 《农业工程学报》 CSCD 北大核心 2018年第7期66-74,共9页
针对目前农业机械设备少有从振动机理方面研究行星减速轮系的故障特性,且缺乏对不同故障程度下系统故障特性的研究等问题,该文以拖拉机传动系统中的行星齿轮减速箱为研究对象,建立了行星轮系动力学模型,考虑了其在运行时振动传递路... 针对目前农业机械设备少有从振动机理方面研究行星减速轮系的故障特性,且缺乏对不同故障程度下系统故障特性的研究等问题,该文以拖拉机传动系统中的行星齿轮减速箱为研究对象,建立了行星轮系动力学模型,考虑了其在运行时振动传递路径时变效应对振动信号的影响;推导了行星轮故障下的啮合刚度变化表达式,并引入故障因子,得到了不同故障程度下的啮合刚度;采用变步长的Runge-Kutta方法求解行星轮系动力学模型,分析得到了行星轮分别出现裂纹及断齿故障时系统响应的频谱特性。模型分析结果表明,由于振动传递路径时变效应对响应信号的调制作用,行星轮系频谱中的啮合频率及其倍频附近出现了以行星架转频为调制频率的边频带;当行星轮出现裂纹或断齿故障时,啮合频率及其倍频附近不仅出现了以行星架转频为调制频率的边频带,同时还会出现以行星轮故障频率为调制频率的边频,且断齿故障状态下的边带幅值较裂纹故障下更加明显。最后将试验信号与模型信号进行对比分析,分析发现,试验与模型响应信号对应频率的最大相对误差分别为4.65%和2.32%,决定系数R2分别为0.9996和0.9998,所得试验结果与模型结果基本一致,验证了所建立模型的准确性。该文可为农机设备中行星轮系的故障机理及系统健康监测研究提供参考。 展开更多
关键词 拖拉机 齿轮 振动 故障特性 动力学模型 啮合刚度
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