Dynamics of the Rolling Stock and the Choice of Parameters of Vibration Dampers

Modern railway rolling stock should meet requirements regarding comfort (maximum travel speed with minimum vibrations of wagons, noiselessness of movement, etc.).To eliminate the influence of dynamic loads, rolling stock is equipped with vibration dampers. The objective of the work is to select the parameters of the vibration dampers of rolling stock, depending on its characteristics, to ensure the due indicators of comfort and safety of transportation of passengers and goods by rail. To achieve this objective, applied methods of mathematical modelling were based on numerical programming of operation of dynamic systems. The indicators of vibration dampers are evaluated according to the results of studies of the dynamics of the rolling stock (in particular, of vibration protection rates).Assessment of dynamic state of the rolling stock implies application of methods of mathematical and physical modelling, which include the development of a physical and mathematical model, a calculation algorithm, and computer programming. The study of the mathematical model by numerical methods makes it possible to carry out a multifactorial experiment using a large number of input parameters (factors) and to select the characteristics of vibration dampers that are optimal for the conditions under consideration.To solve dynamic problems, the harmonic perturbation model, which is the most widespread, was specified in the form of a sinusoid with a period corresponding to the rail length.A quantitative assessment of the vibration process (frequency, amplitude) makes it possible to identify the main processes occurring in the system under consideration under various types of external load. The introduced assumptions related to rigidity, mobility and geometric immutability of the system allow determining the methods for obtaining a mathematical model and considering the vibrations as flat ones.The equations were solved in MathCad Prime 4.0 package using the Runge–Kutta method with automatic step selection. The subsequent study of the properties of the dynamic system was carried out by changing the resistance parameter of dampers of the first stage of spring suspension, while recording the values of the amplitude of the vibrations of the system and the period.The analysis of the results has shown that the vibration period of the body and bogies under any changes in the resistance parameter of the damper remains unchanged, while rational parameters of resistance of axle box dampers have been revealed for specified indicators. Hydraulic vibration dampers with the revealed parameters used on rolling stock help to reduce wear and damageability of running gears, improve ride comfort and traffic safety, as well as to reduce repair and maintenance costs.

Protection of precision spacecraft equipment from internal sources of vibration

The work is devoted to the protection of a spacecraft from the influence of unacceptable internal vibration sources. The urgency of reducing the vibration activity on board the spacecraft to improve the accuracy of the target equipment is indicated. A particular problem of vibration protection of the spacecraft platform from a vibration source – an electric pump unit of a liquid thermal control system – is being solved. The basic requirements for electric pump unit vibration protection have been determined. Possible ways to reduce the level of vibration excited by the electric pump unit on the surface of the spacecraft fixation are considered. Particular attention is paid to such vibration protection methods as damping and vibration isolation, implemented by installing special vibration protection devices between the source (electric pump unit) and the object (spacecraft) – vibration isolators and vibration dampers. The principles of operation of vibration dampers and vibration isolators, the most common materials for vibration dampers are described. Examples of constructive solutions for linear single-axial vibration isolators are considered, recommendations for the use of promising products are developed. Particularemphasis is placed on the use of metal rubber as a material for vibration isolators. With regard to a specific design of electric pump unit, a diagram of the spatial structure of vibration isolation is proposed. Formulas for calculation are given in detail, a mathematical model of the vibration isolation system is developed. The procedure for calculating the parameters of the system has been formed. Based on the model, the maximum possible level of vibration suppression in the mid-frequency region was determined. Minimum required number of operable pixels was identified for monitoring the water surface with sufficient accuracy and reliability.

Arrangement Method of Vibration Dampers Considering Frequency Response Physical Characteristics and Stiffness of Conductor

In order to study the calculation method of installation distance of vibration dampers with higher precision, so as to maximize its anti-vibration performance on the conductor. The arrangement method of dampers based on the frequency response characteristics of conductors is proposed, the dynamic model of conductor considering stiffness is established. The model is solved by finite difference method, the natural frequency and vibration mode of conductor in case of Aeolian vibration are obtained, and the wavelength of conductor vibration is obtained according to its mode, so as to calculate the installation distance of vibration dampers. The calculation results of the new method are compared with those of the traditional method, which proves the advantage of the new method in calculation accuracy. The new method has a good effect on improving the calculation accuracy of the installation distance of the vibration dampers on the conductors, which is greatly influenced by its stiffness. At the same time, the frequency response of the conductor should be considered as much as possible in the calculation of the installation distance of the damper.

Detection of Abnormal Vibration Dampers on Transmission Lines in UAV Remote Sensing Images with PMA-YOLO

The accurate detection and timely replacement of abnormal vibration dampers on transmission lines are critical for the safe and stable operation of power systems. Recently, unmanned aerial vehicles (UAVs) have become widely used to inspect transmission lines. In this paper, we constructed a data set of abnormal vibration dampers (DAVDs) on transmission lines in images obtained by UAVs. There are four types of vibration dampers in this data set, and each vibration damper may be rusty, defective, or normal. The challenges in the detection of abnormal vibration dampers on transmission lines in the images captured by UAVs were as following: the images had a high resolution as well as the objects of vibration dampers were relatively small and sparsely distributed, and the backgrounds of cross stage partial networks of the images were complex due to the fact that the transmission lines were erected in a variety of outdoor environments. Existing methods of ground-based object detection significantly reduced the accuracy when dealing with complex backgrounds and small objects of abnormal vibration dampers detection. To address these issues, we proposed an end-to-end parallel mixed attention You Only Look Once (PMA-YOLO) network to improve the detection performance for abnormal vibration dampers. The parallel mixed attention (PMA) module was introduced and integrated into the YOLOv4 network. This module combines a channel attention block and a spatial attention block, and the convolution results of the input feature maps in parallel, allowing the network to pay more attention to critical regions of abnormal vibration dampers in complex background images. Meanwhile, in view of the problem that abnormal vibration dampers are prone to missing detections, we analyzed the scale and ratio of the ground truth boxes and used the K-means algorithm to re-cluster new anchors for abnormal vibration dampers in images. In addition, we introduced a multi-stage transfer learning strategy to improve the efficiency of the original training method and prevent overfitting by the network. The experimental results showed that the for PMA-YOLO in the detection of abnormal vibration dampers reached 93.8% on the test set of DAVD, 3.5% higher than that of YOLOv4. When the multi-stage transfer learning strategy was used, the was improved by a further 0.2%.

Compression Rubber Damper Assessment Through Simulation

Rubber torsional vibration dampers are often used on mid-range engines. Usually, the geometry of a rubber torsional vibration damper is such that the rubber element in it undergoes shear. However, in the work presented, a compression rubber damper is being proposed, in which the rubber element undergoes compression rather than shear. The proposed compression rubber damper, just like the shear rubber damper, is a tuned damper. An analytical tool is being used to evaluate the stiffness of compression rubber design and thus evaluate its performance. The rubber geometry, material and plate design are selected through simulations. The analytical tool demonstrates the functionality of the compression rubber damper paper and focuses on simulation-based product development using ANSYS for FEA and an in-house tool for torsional vibration analysis.

Choosing Damping Parameters for the Inertial Orientation System

The article discusses criteria for selecting the vibration protection for the spacecraft inertial orientation system. The considered vibration protection system allows providing acceptable amplitude acceleration for the gyroscopic device sensitive elements under vibration impact on the device body during the spacecraft launching and high angular stability of the position of the sensitive elements relative to the inertial coordinate system during a long period of operation (15 years) in orbit. The proposed vibration protection system consists of shock absorbers (springs) with stable high elastic characteristics under all factors of operation in the outer space and dynamic vibration dampers. The article presents a method for determining the parameters of dynamic vibration dampers taking into account the characteristics of the shock absorber, critical for the damping system of an inertial device. The proposed method for adjusting dynamic vibration dampers consists in suppressing vibrations at the natural frequency f1 of the shock absorption system and providing acceptable values of the gain coefficients of the structure resonant vibration amplitudes near the natural frequency f1. Certain characteristics of the damping system allow realizing the permissible vibration amplification coefficients at resonance, without significantly affecting the level of vibration suppression in the natural frequency zone of the vibration protection object

ANALISIS PENGARUH TEBAL PLAT TERHADAP KARAKTERISTIK MEKANIK PEGAS DAUN PADA PROTOTIPE MOBIL FISH CAR UNEJ (FCU) MUDSKIP

Fish Car Unej (FCU) Mudskip is a car designed with a rural terrain system, especially for fishing transportation. FCU Mudskip uses leaf spring suspension at the rear to support the weight of the vehicle, that is leaning towards the rear. The load of the vehicle is inclined to the rear due to the car carrying system in the form of fish and water. This conveying system can cause leaf spring failure. Therefore, this study aims to determine the value of stress, strain and cycle on leaf springs. Ansys 18.1 software was used to obtain stress, strain, and leaf spring cycle values with a thickness of 7 mm, 10 mm, and 13 mm. The value of stress on leaf springs with thickness 7 is 124,31 x 106 N/m2; thickness 10 mm is 74,92 x 106 N/m2; thickness 13 mm is 48,08 x 106N/m2; the value of strain on leaf springs with a thickness of 7 mm is 0,00075; a thickness of 10 mm is 0,00045; a thickness of 13 mm is 0,00029; Acceptable cycles of leaf springs are 7 mm thick is 69206 cycles, 10 mm is 77833 cycles, and 13 mm thick is 93054 cycles. Leaf springs with a thickness of 13 mm are the most optimal leaf springs because they can receive the most cycles of 93054 cycles, according to the function of leaf springs as vibration dampers.