Application of experimental modal analysis technique to structural design of linear vibrating screen

A large model of the screen was mounted in the laboratory for studying its modal performance. The model is suspended with steel ropes. Modal test was carried out with artificially exciting by 500 g impacting hammer and 100 kg exciting force shaker respectively. Synthesis and correction of the modal parameters are obtained from both testing methods. Design faults of vibrating screen were determined based on the analy-sis and dynamic correction of structure approaches about the screen was put forward finally.

MODAL ANALYSIS OF A CHASSIS FRAME OF A HEAVY LECTRA HAUL

The chassis frame of a heavy lectra haul is analysed by both modal experiment method and finite element method (FEM ) . The first ten order modal parameters of the chassis frame have been obtained satisfactorily. These parameters have important reference value in designing the chassis frame properly and provide a necessary basis for the fault diagnostics of the truck.

Firmness evaluation of melon using its vibration characteristic and finite element analysis

The “Huang gua” melons were measured for their physical properties including firmness and static elastic modulus. The vibrational characteristics of fruits and vegetables are governed by their elastic modulus (firmness), mass, and geometry. Therefore, it is possible to evaluate firmness of fruits and vegetables based on their vibrational characteristics. Analysis of the vibration responses of a fruit is suggested for measuring elastic properties (Firmness) non-destructively. The impulse response method is often used to measure firmness of fruits. The fruit was excited using three types of balls (wooden, steel and rubber) and the vibration is detected by an accelerometer. The Instron device was used to measure the static elastic modulus of the inner, middle and outer portions of melon flesh. Finite element (FE) technique was used to determine the optimum excitation location of the chosen measurement sensor and to analyze the mode shape fruits. Four types of mode shapes (torsional or flexural mode shape, first-type, second-type spherical mode and breathing mode shape) were found. Finite element simulation results agreed well with experimental results. Correlation between the firmness and resonant frequency (r2=0.91) and between the resonant frequency and stiffness factor (r2=0.74) existed. The optimum location and suitable direction for excitation and response measurement on the fruit were suggested.

Modal Parameters Identification of A Real Offshore Platform From the Response Excited by Natural Ice Loading

This paper investigates the possibility of utilizing response from natural ice loading for modal parameter identification of real offshore platforms.The test platform is the JZ20-2 MUQ jacket platform located in the Liaodong Bay,China.A field experiment is carried out in winter season,as the platform is excited by floating ices.The feasibility is demonstrated by the acceleration response of two different segments.By the SSI-data method,the modal frequencies and damping ratios of four structural modes can be successfully identified from both segments.The estimated information from both segments is almost identical,which demonstrates that the modal identification is trustworthy.Furthermore,by taking the Jacket platform as a benchmark,the numerical performance of five popular time-domain EMA methods is systematically compared from different viewpoints.The comparisons are categorized as:(1)stochastic methods versus deterministic methods;(2)high-order methods versus low-order methods;(3)data-driven versus covariance-driven stochastic subspace identification methods.

Numerical and Experimental Research on the Influence of the Centrifugal Pumps Rotor Damage on Their Natural Frequency Response

The paper presents process of creating a centrifugal pump rotor model in CAD environment. Modeling of a virtual object was divided into two stages, modeling of the efficient pump and the simulated failure of one of the impeller＇s blades. Comparison of the results of the resonance frequency obtained from the model analysis, with those obtained from measurements on the actual object was shown. Measurements and simulations were conducted on the pump before and after the simulated damaged of the rotor. In order to verify the model the rotor of pump was weighted and compared with the masses of the respective components obtained from the virtual object. In the second stage genuine rotor was subjected to the experimental modal analysis.

Novel approach for determining the optimal axial preload of a simulating rotary table spindle system

This paper presents a new theoretical model to determine the optimal axial preload of a spindle system, for challenging the traditional method which relies heavily on experience of engineers. The axial preloading stiffness was treated as the sum of the spindle modal stiffness and the framework elastic stiffness, based on a novel concept that magnitude of preloads can be controlled by measuring the resonant frequency of a spindle system. By employing an example of a certain type of aircraft simulating rotary table, the modal stiffness was measured on the Agilent 35670A Dynamic Signal Analyzer by experimental modal analysis. The equivalent elastic stiffness was simulated by both finite element analysis in ANSYS? and a curve fitting in MATLAB?. Results showed that the static preloading stiffness of the spindle was 7.2125×107 N/m, and that the optimal preloading force was 120.0848 N. Practical application proved the feasibility of our method.

Effects of Fiber Volume Fraction on Damping Properties of Three-Dimensional and Five-Directional Braided Composites

The effects of fiber volume fraction on damping properties of carbon fiber three-dimensional and five-directional( 3D-5Dir)braided carbon fiber / epoxyres in composite cantilever beams were studied by experimental modal analysis method. Meanwhile,carbon fiber plain woven laminated / epoxy resin composites with different fiber volume fraction were concerned for comparison. The experimental result of braided specimens shows that the first three orders of natural frequency increase and the first three orders of the damping ratios of specimens decrease, when the fiber volume fraction increases. Furthermore,larger fiber volume fraction will be valuable for the better anti-exiting property of braided composites,and get an opposite effect on dissipation of vibration energy. The fiber volume fraction is an important factor for vibration performance design of braided composites. The comparison between the braided specimens and laminated specimens reveals that 3D braided composites have a wider range of damping properties than laminated composites with the same fiber volume fractions.

Detection of Blade Mistuning in a Low Pressure Turbine Rotor Resulting from Manufacturing Tolerances and Differences in Blade Mounting

For a serious prediction of vibration characteristics of any structure, a detailed knowledge of the modal characteristic is essential. This is especially important for bladed turbine rotors. Mistuning of the blading of a turbine rotor can appear due to manufacturing tolerances or because of the blading process itself due to unequal mounting of the blades into the disk. This paper investigates the mistuning of the individual blades of a low pressure turbine with respect to the effects mentioned above. Two different rotors with different aerodynamic design of the blades were investigated. The blades were mounted to the disk with a so-called hammer head root which is especially prone to mounting irregularities. For detailed investigations, the rotor was excited with a shaker system to detect the forced response behavior of the individual blades. The measurements were done with a laser vibrometer system. As the excitation of rotor structure was held constant during measurement, it was possible to detect the line of nodes and mode shapes as well. It could be shown that the assembly process has an influence on the mistuning. The data were analyzed and compared with numerical results. For this, different contact models and boundary conditions were used. The above described characterization of modal behavior of the rotor is the basis for the upcoming aeroelastic investigations and especially for the blade vibration measurements of the rotor, turning with design and off-design speeds.

Fault Diagnosis of Cylindrical Grinding Machine

Based on experiment modal analysis(EMA) and operation modal analysis(OMA), the dynamic characteristics of cylindrical grinding machine were measured and provided a basis for further failure analysis.The influences of grinding parameters on dynamic characteristics were studied by analyzing the diagnostic signals extracted from racing and grinding experiments.The significant frequency of 38 Hz related to grinding wheel spindle speed of 2 307 r/min showed that the wheel spindle system was in a state of imbalan...

Vibration-based crack prediction on a beam model using hybrid butterfly optimization algorithm with artificial neural network

Vibration-based damage detection methods have become widely used because of their advantages over traditional methods.This paper presents a new approach to identify the crack depth in steel beam structures based on vibration analysis using the Finite Element Method(FEM)and Artificial Neural Network(ANN)combined with Butterfly Optimization Algorithm(BOA).ANN is quite successful in such identification issues,but it has some limitations,such as reduction of error after system training is complete,which means the output does not provide optimal results.This paper improves ANN training after introducing BOA as a hybrid model(BOA-ANN).Natural frequencies are used as input parameters and crack depth as output.The data are collected from improved FEM using simulation tools(ABAQUS)based on different crack depths and locations as the first stage.Next,data are collected from experimental analysis of cracked beams based on different crack depths and locations to test the reliability of the presented technique.The proposed approach,compared to other methods,can predict crack depth with improved accuracy.