Prediction Of Vibration Characteristics Research Articles

Mobile Interface CMS Method for Vibration Characteristics Prediction of Mistuned Bladed Disk with Different Coupling Degrees

The prediction of vibration characteristics was studied in the mistuned bladed disk by the mobile interface prestressed component mode synthesis (CMS) superelement method. When the strongly, generally, and weakly coupling in the mistuned bladed disk, according to the results of the direct FEM method, the prediction accuracy of this method was verified and compared with the fixed-interface CMS method by using the relative error of dynamic frequency, vibration mode matching function, and dimensionless root mean square error of vibration amplitudes. It is pointed that for mistuned bladed disk in the strong coupling, the prediction accuracy of dynamic frequency and vibration amplitudes are higher by the mobile interface CMS method and the vibration modes are matched with the direct method. In weak coupling, the results of dynamic frequency and vibration modes predicted by the mobile interface CMS method and the fixed-interface CMS method are consistent with the direct method, but the vibration amplitudes’ prediction error of the mobile interface CMS method is lower than that of the fixed-interface CMS method. In general coupling, the mobile interface CMS method has higher dynamic frequency prediction accuracy at low order, and the two methods have comparable dynamic frequency prediction accuracy at high order. The vibration modes predicted by the two methods are matched with the direct FEM method, and the prediction accuracy of vibration amplitude by the mobile interface CMS method is better than that of the fixed-interface CMS method. The results indicate that the mobile interface CMS method could more accurately predict vibration characteristics of the mistuned bladed disk with different coupling degrees and could be an effective measurement for studying the vibration characteristics of the mistuned bladed disk system.

Finite element analysis for predicting the vibration characteristics of natural fiber reinforced epoxy composites

Modal analysis is a tool to predict the vibration characteristics such as natural frequencies, mode shapes and viscous damping coefficients of the structures. These characteristics play an important role in engineering design and analysis. In this paper, the prediction of vibration characteristics or modal-modal of cantilever beam made of neat epoxy and various natural fiber composites carried out by using finite element analysis software ANSYS 20.0. In this study, the natural fibers such as jute, banana, coconut coir, hemp and kenaf fibers are used as reinforcement in the epoxy matrix. The size of beam is 160 mm × 20 mm × 3 mm. The volume fraction of fiber is 33.33% taken for all natural fiber composite materials. The natural frequencies, damping factor and frequency response function bode plot are obtained with the help of ANSYS software. The damping factor is found out using half power bandwidth method from frequency response function bode plot. The natural frequency and damping factors of different natural fiber composites are compared with epoxy material. It is found from this analytical study that the damping factor values for each natural fiber composite material have higher values corresponding to each mode than that of epoxy material. Hence, it is concluded that the natural fiber composites have better damping properties than epoxy material. Hemp and kenaf fiber composite materials have similar values of natural frequencies for lower modes (1st mode and 2nd mode) and at higher modes (5th mode and 6th mode) respectively.

Prediction of vibration characteristics in beam structure using sub-scale modeling with experimental validation

Geometric or sub-scale modeling techniques are used for the evaluation of large and complex dynamic structures to ensure accurate reproduction of load path and thus leading to true dynamic characteristics of such structures. The sub-scale modeling technique is very effective in the prediction of vibration characteristics of original large structure when the experimental testing is not feasible due to the absence of a large testing facility. Previous researches were more focused on free and harmonic vibration case with little or no consideration for readily encountered random vibration. A sub-scale modeling technique is proposed for estimating the vibration characteristics of any large scale structure such as Launch vehicles, Mega structures, etc., under various vibration load cases by utilizing precise scaled-down model of that dynamic structure. In order to establish an analytical correlation between the original structure and its scaled models, different scale models of isotropic cantilever beam are selected and analyzed under various vibration conditions( i.e. free, harmonic and random) using finite element package ANSYS. The developed correlations are also validated through experimental testing. The prediction made from the vibratory response of the scaled-down beam through the established sets of correlation are found similar to the response measured from the testing of original beam structure. The established correlations are equally applicable in the prediction of dynamic characteristics of any complex structure through its scaled-down models. This paper presents modified sub-scale modeling technique that enables accurate prediction of vibration characteristics of large and complex structure under not only sinusoidal but also for random vibrations.

Vibration Characteristics of Disks-Spindle System in Hard Disk Drives#

The purpose of this paper is to develop both numerical and experimental methods that can be used for easy prediction of vibration characteristics of disk-spindle systems in hard disk drives (HDDs). First, the effective numerical method, i.e., Finite element method (FEM), for the modeling of the whole disks and spindle system under real product constraint conditions has been discussed. So the dynamics properties of the disk-spindle system during the system design can be are analyzed conveniently. Finally, these analytical predictions by FEM are verified through the proposed modal testing setup. The dynamic characteristics of the whole assembly have been measured through externally induced excitations. Results obtained using numerical and experimental methods agree very well. As demonstrated, the numerical methodology, i.e., FEM can provide much detailed information on the design of the disk-spindle system before it is built and tested to confirm the system design.

218 ガラス短繊維強化 6 ナイロンの振動特性を用いた機械的性質の同定 : 第 2 報 : ガラス短繊維の配向分布を考慮した振動特性の予測

218 ガラス短繊維強化 6 ナイロンの振動特性を用いた機械的性質の同定 : 第 2 報 : ガラス短繊維の配向分布を考慮した振動特性の予測