蔬菜纸面膜成型机滚切装置机架模态分析

目的研究滚切成型装置机架的动态特性,为分析和评价蔬菜纸面膜成型机的工作性能提供理论依据。方法通过Unigraphics NX建立滚切成型装置机架的实体模型,然后导入Ansys Workbench进行模态分析,提取并分析前6阶固有频率与振型变化。结果滚切装置机架的最小固有频率为334.74 Hz,机架最大变形发生在第4阶振型右支撑板前梁的中间部分。结论滚切成型装置机架的激振频率远小于最小固有频率,不会产生共振与严重噪声。     

倒装键合机支撑板模态参数提取与实验验证

采用ANSYS有限元仿真计算与LMS Test.Lab锤击实验相结合的方法研究支撑板的模态特性。仿真分析得到支撑板的前6阶固有频率和振型,并通过实验验证仿真结果的准确性。将理论计算与试验的结果进行对比分析,得出支撑板的一阶固有频率为400Hz,高于支撑板上安装的伺服电机的工作频率以及周围环境的激振频率,因此不会产生共振现象,为防止共振、改善整机质量性能及结构优化提供参考依据。     

基于Ansys Workbench对卸料装置的动态性能分析与优化

目的研究振动电机的激励对卸料装置在满载工况下卸料时产生的影响,并对卸料装置振动特性进行优化。方法采用Solid Works对卸料装置建模,运用Ansys Workbench软件分析其前8阶固有频率和模态振型,找到其结构薄弱区,对比分析外部激振频率与卸料装置固有频率是否共振,以卸料装置薄弱区为参考,来优化振动电机的安装位置。结果由模态分析得,卸料装置第7阶固有频率在共振区内,可能会导致卸料装置共振;结合谐响应分析确定了卸料装置第1,4,5阶固有频率附近的振幅位移最大,同时得出振动电机在E,F,G处安装位置下,卸料装置响应构件的最大振幅位移分别为1.8,1.86,1.9 mm。结论通过综合分析得出,在卸料装置上施加外界激振频率时应避开16 Hz和33 Hz,同时可知振动源安装在F处最优,为卸料装置在实际设计和制造过程中提供必要的依据。     

空调管路系统的有限元分析及优化设计

针对设计好的空调管路系统振动较大问题,运用Hyper Mesh软件将设计好的空调管路模型划分成高质量的六面体网格。再将划分好的网格模型导入Ansys中进行模态分析,分析计算出前10阶的固有频率和振型。发现1阶固有频率在工作频率附近,分析该阶固有频率的振型并据此提出管路改进的设计方案,使空调管路系统固有频率远离工作频率,避免产生共振。最后对改进前后的结构进行实验对比,得到改进后的结构振幅减小90%的结果。实践表明在空调减振过程中应用Ansys等有限元技术辅助分析很好地提高了效率和准确性。     

大功率船用齿轮箱试验模态分析*

由于大功率船用齿轮箱的特殊使用工况,其性能要求远远高于其他齿轮箱。论文对某大功率船用齿轮箱结构和传动原理进行分析,根据试验模态分析的基本原理和方法,利用最小二乘法对频响函数进行优化,并利用单模态识别法对大功率船用齿轮箱进行模态参数识别,得出系统的前20阶固有频率和阻尼,结果表明该船用齿轮箱系统的转频、啮合频率远离固有频率,系统不存在共振现象。但考虑齿轮箱实际工作的复杂性,在系统转速变化达到临界转速时存在较为剧烈的共振现象。试验结果可为进一步系统研究动态特性提供分析依据。     

预应力作用下的薄壁二极铁真空室模态分析

真空室受到外界激励时会产生振动,当外界激励频率接近真空室的固有频率时就会产生共振。真空室作为束流运行的场所,如果发生共振不但会影响真空系统的气密性还可能会引起结构的损伤破坏。本文结合薄壁二极铁真空室的实际使用工况,采用有限元软件分析了二极铁真空室的自由振动模态及预应力作用下的模态,得出了在自由振动情况下结构的前6阶模态固有频率基本为0,属于刚体模态,在预应力作用下结构前6阶模态固有频率在400-720 Hz范围内,并且第1和第2阶模态为整体模态,其模态特征主要集中在结构中间的薄壁和加强筋上,第3-6阶模态为局部模态,其模态特征主要集中在结构侧面的加强筋上。     

扫描频率激振下可控震源振动器模态分析

准确掌握扫频频率激振下可控震源振动器的模态特性,可为可控震源的激发信号质量改善提供依据。根据弹性半空间理论,建立并验证振动器-大地耦合振动模型,分析结构的模态,掌握结构的固有频率和振型。研究表明,在扫描频率下,仅存在两次共振。1阶共振时的振型是重锤和平板同向共振,结构的响应以重锤为主;2阶共振时的振型是重锤与平板反向共振,平板的响应占据主导地位。在勘探时应尽量避免扫描频率与固有频率重叠,防止振动器共振,从而有效降低共振导致的源致干扰。     

液压挖掘机工作装置的动力特性修改研究

为提高液压挖掘机工作装置动态性能的优化效率，在对该结构进行试验模态研究的基础上，用双模态空间动力修改方法进行了动力特性修改研究，研究结果表明：质量修改对该结构的1阶、2阶固有频率和阻尼比有显著影响，对其他阶结构动态特性的影响很小；刚度修改对该结构1阶至5阶的固有频率和阻尼比均有明显影响，高阶的固有频率和阻尼比对刚度的变化敏感。所得到的结论揭示了模态参数调整对液压挖掘机工作装置动力特性的影响规律，为提高机械产品的总体质量奠定了基础。     

不同浸没深度下锥型喷嘴结构固有振动特性研究

锥形喷嘴结构工作环境复杂,其浸没深度会随着工况的不同经常改变,研究不同浸没深度下锥形喷嘴结构的固有振动特性具有重要意义。利用声固耦合有限元法,得到锥型喷嘴结构的前6阶固有频率与模态振型。利用压电陶瓷作为传感器和作动器搭建模态分析实验平台,采用正弦扫频的方法,测得锥型喷嘴结构的前6阶固有频率,验证数值方法的准确性。最后利用数值方法研究不同浸没深度下锥形喷嘴结构的耦合振动特性。     

某纯电动汽车减速器模态分析

减速器是纯电动汽车的关键部件。在提高车辆最高速度,缩短车辆加速时间的同时,对纯电动汽车的振动噪声特性有着十分直观的影响。以某纯电动汽车的减速器为研究对象,对其减速器箱体及传动装置的模态特性进行分析。首先,根据该纯电动汽车减速器工程图,建立减速器的三维实体模型。然后,通过软件导入已建立的模型,选择减速器箱体及传动系统材质。对箱体及传动装置进行网格划分。最后,通过有限元分析,选取分块兰索斯法(Block Lanczos),输出前6阶模态固有频率和振型。发现减速器传动装置及箱体的固有频率远离传动系统特征频率,不会产生共振。研究结果可为后续优化研究提供参数依据。     

Analysis of a Premature Failure of a Hub from a Diesel Generator of a High-Speed Motor Ship

Failure analysis is carried out on a fractured hub obtained from a diesel generator of a high-speed motor ship. Macrofractography, microfractography, standard optical metallography, material characterization techniques, and numerical modeling were used to verify the findings of the current investigation. Cracking initiation is attributed to fretting fatigue caused by a modification performed in the vicinity of the fractured hub. Operational vibrations contributed to the propagation of the cracks as typical fatigue cracks until final fracture.     

Resistance of a sphere in a slow flow of a viscoelastic fluid

The authors have obtained an approximate solution of the problem of the resistance of a rigid sphere in a slow flow of a Maxwell viscoelastic fluid that is in good agreement with experimental data [1] for Weissenberg numbers We ≤ 0.7. It is shown that the effect of a decrease in the coefficient of resistance of a sphere in the interval 0.1 ≤ We ≤ 0.7 established experimentally is determined in full measure by the linear viscoelastic properties of the Maxwell fluid. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 6, pp. 1138–1140, November–December, 1998.     

Dispersion of a solute in a Poiseuille flow of a viscoelastic fluid

Gill and Sankarasubramanian's analysis of the dispersion of Newtonian fluids in laminar flow between two parallel walls is extended to the flow of non-Newtonian viscoelastic fluids (known as Phan-Thein-Tanner (PTT)). Using a generalized dispersion model which is valid for all times after the solute injection, the diffusion coefficient K_i(t) is obtained exactly and numerically for linearized and exponential forms of the PTT fluids, respectively. The analysis leads to the novel result for K₁ and K₂(t) (which is a measure of the longitudinal dispersion coefficient of the solute). It is found that the value of K₂(t) depends on the value of Deborah number (De=a measure of the level of elasticity in the fluid) whereas the value of K₁ is constant in both cases. Finally, the effect of the Deborah number on the axial distribution of the mean concentration θ_m is investigated in detail.     

聚醚砜四元制膜液体系的相图计算

以Ｆｌｏｒｙ－Ｈｕｇｇｉｎｓ理论为基础，对ＰＥＳ－ＰＧ－ＮＭＰ＿Ｈ２Ｏ＿）聚醚砜丙二醇－Ｎ－甲基－２－哟咯烷酮水）四元制液体系的相图进行了计算，利用三元相图考察Ｈ２Ｏ和ＰＧ对液－液相分离的影响，在三元的理论的基础上提出了低分子量添加剂的卤元改性Ｆｌｏｒｙ－Ｈｕｇｇｉｎｓ理论，并提出了一种获得四元相图的方法，利用四元相图能较争地描述四元体系，利用改性的四元理论，能了地理解该种体系的液－液相分离行为。     

Flow of a thin film of a viscous liquid in a gas jet

An approximate formulation is considered for the steady-state wave flow of a thin film of viscous liquid subject to tangential frictional stresses at the boundary. Measurements have been made on the stability limit for droplet detachment, and it has been found that the detachment rate and fractional composition of the droplets are dependent on the boundary conditions.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 4, pp. 622–630, April, 1981.     

Drag of a plate in a uniform flow of a weak polymer solution

The problem of the drag of a plate moving in a weak polymer solution is solved on the basis of a three-layer schematization of the velocity distribution in the turbulent boundary layer.Translated from Inzhenerno-Fizicheskii Zhurnal, Vo. 41, No. 5, pp. 819–826, November, 1981.     

Heat exchange of a swirled stream of a gas suspension in a pipe

The results of an experimental investigation of heat exchange during turbulent flow of a gas containing suspended particles of a solid material in a horizontal pipe are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 2, pp. 198–202, August, 1986.     

Heat Transfer of a Sphere in a Constrained Flow of a Viscous Fluid

Results of an experimental investigation of the average heat transfer of a sphere in the region of Reynolds numbers 0.1–40 are given. The increase in the Nusselt number with increase in the constraint parameter of flow is established. Based on the fractal theory, the influence of the degree of constraint on the heat transfer is physically explained and a quantitative correction is introduced.     

Calculation of a transient in a two-pole network with a thermistor

An analytical expression is derived which describes the variation of the thermistor temperature during a relay-effect transient process following an instantaneous change in the supply voltage in an R — R_T two-pole network.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 38, No. 3, pp. 465–472, March, 1980.