Dynamic Elastic Characteristics Research Articles

Experimental Evaluation of Under Slab Mats (USMs) Made from End-of-Life Tires for Ballastless Tram Track Applications.

The growing population of urban areas results in the need to deal with the noise pollution from the transportation system. This study presents experimental test results of static and dynamic elastic characteristics of under slab mats (USMs) according to the procedure of DIN 45673-7. Prototype USMs based on recycled elastomeric materials, i.e., SBR granules and fibres produced from waste car tires, are analysed. Vibration isolation mats with different thicknesses (10, 15, 20, 25, 30, and 40 mm), densities (500 and 600 kg/m3), and different degrees of space filling (no holes, medium holes, large holes) are considered. Moreover, a practical application of the laboratory test results of USMs in the design of ballastless track structures of two different types (with a concrete slab and longitudinal beams) is presented. Deflections of the rail and the floating slab system, as well as stresses acting on the mat, are determined according to EN 16432-2. The use of shredded rubber from recycled car tires as a material component of sustainable and environmentally friendly tram track structures may be one of the most effective ways to manage rubber waste within the current trend toward a circular economy, and this study intends to introduce methods for experimental identification and analytical selection of basic static and dynamic parameters of prototype USMs.

Experimental and numerical testing of prototypical under ballast mats (UBMs) produced from deconstructed tires – The effect of mat thickness

In this study, the authors analyse performance of prototypical under ballast mats (UBMs) made of recycled rubber granulate and fibres, produced from end-of-life tires. First, a series of experimental tests is performed, in order to identify static and dynamic elastic characteristics (static bedding modulus, low- and high-frequency dynamic bedding modulus) of four UBMs with the same density and different thicknesses. Additionally, fatigue strength of the mat with a thickness of 20 mm is analysed. Then, the values of static and dynamic bedding moduli are used as an input in the finite element model of the ballasted track structure with UBM. The main aim of the numerical simulations is to compare mechanical behaviour of the reference system and systems with four different mats. It is proved that the thickness of UBMs has a significant effect on the values of static and dynamic bedding moduli, and on the effectiveness of vibration isolation. The insertion loss values vary between 62 % for the thickness 15 mm and 75 % for the thickness 30 mm (at the frequency 31.5 Hz, that is vibration), and between 37 % for the thickness 15 mm and 54 % for the thickness 30 mm (at the frequency 125 Hz, that is structure-borne noise).

АППРОКСИМАЦИОННАЯ МОДЕЛЬ ДИНАМИЧЕСКИХ ЖЕСТКОСТНЫХ ХАРАКТЕРИСТИК ГИДРАВЛИЧЕСКИХ ВИБРОИЗОЛЯТОРОВ

The article discusses the use of hydraulic vibration mounts in the design of vibration isolation systems. A method of using approximating functions for modeling the dynamic elastic characteristics of vibration isolators in the study of mechanical systems with elastic and damping connections is proposed. The results of calculating a single-mass system with hydraulic mounts and a comparison of the results with experimental data are presented.

Study on Possible Application of Rubber Granulate from the Recycled Tires as an Elastic Cover of Prototype Rail Dampers, with a Focus on Their Operational Durability.

This study is an attempt to investigate possible applications of rubber granulate SBR (styrene-butadiene rubber) produced from recycled waste tires as an elastic cover for prototype rail dampers, which are aimed at reducing the level of railway noise emitted in the environment. The authors present laboratory procedures and discuss the results of several experimental tests performed on seven different SBR materials with the following densities: 1100, 1050, 1000, 850, 750, 700 and 650 kg/m3. It is proven that rubber granulate SBR produced from recycled waste tires, can be used as an elastic cover in steel inserts in rail dampers, provided that the material density is not lower than 1000 kg/m3. In the conducted tests, samples of the materials with high densities exhibited good static and dynamic elastic characteristics and had sufficient operational durability.

Analytical determination of static and dynamic elastic characteristics of pneumohydraulic suspension systems

When developing new suspensions for tracked and wheeled vehicles, as well as in the so-called reverse engineering of existing structures (including in the educational process of training personnel), it is necessary to solve the problem of finding the elastic characteristics of the suspension. In the first case, it is necessary to ensure the fulfillment of the specified tactical and technical requirements, in the second - to restore the form of characteristics according to a known design. Both of these tasks are greatly complicated in the absence of precise and universal analytical dependencies suitable for determining the characteristics of elastic suspension elements of various design implementations. The experience of interaction with some factories shows that designers, not being able to qualitatively calculate the elastic characteristics, use the method of selection and analogy, when for a new vehicle they use the suspension as on the old one, scaling it in size in order to approximately keep the values of working pressures. The numerous bench tests are carried out, which results are used for selecting required charging volume and pressure. Suspensions with backpressure cause particular difficulty, since not only the final characteristic, but also the performance of the entire unit depends on the combination of volumes and pressures of the two chambers, which work in antiphase: when one is loaded, the other is unloaded, and vice versa. Using analytical dependencies will reduce the time spent on design, to parameterize, to a certain extent, the suspension kinematics, to obtain the values of the equivalent suspension stiffness, and also to be able to develop the characteristics of the model range of pneumohydraulic springs for vehicles of various weight categories.
 This article presents a technique for the analytical determination of the characteristics of pneumohydraulic springs of various designs. The options include both actually used in modern and historical technology (in particular, on BMD-1, 2, 3, 4; GM-352; Ural Typhoon; Object 775, etc.), and obtained by combining various structural elements, which implementation can be useful in the educational process in training personnel. The dependences presented in the article make it possible to obtain static and dynamic elastic characteristics at various polytropic indices and are suitable for the design of suspensions for wheeled and tracked vehicles for various purposes.

Dynamics stand tests and numerical research of multi-leaf springs with regard to clearances and friction

The article deals with investigations of a prototype single and double multi-leaf spring composed of a four-leaf main spring and a double-leaf supporting spring subjected to the cyclic loads. A methodology of a measurement conducted during experimental tests and a set of research instruments used in the stand research allow evaluation of the effects of friction and the accompanying heat stress of the leaf spring in the quasi real operating conditions. The role of clearances and friction in operation of this type of construction as well as analytical, numerical, and bench testing methods used in the research on the effect of energy dissipation due to friction on operation of the leaf spring are discussed. Dynamic elastic characteristics with hysteresis loops and identification of leaf cooperation areas are presented for the single and double multi-leaf springs tested under different conditions.

An Experimental Investigation of the Elastic Dynamic Characteristics of a Model of an Ampoule for the Space Transportation of Radioactive Wastes at High Temperatures

The dynamic elastic characteristics of an experimental physical model of an ampoule for the space transportation of radioactive wastes in the self-delivery mode, i.e., when the wastes are the primary energy source, are described. An experimental system is designed to investigate the characteristics of the model of the ampoule, and a procedure for investigating both the cold and heat-stressed state of the ampoule is developed. The amplitude-frequency characteristics of the ampoule model are obtained for different temperature situations.

Analysis of errors in investigating the complex modulus of viscoelastic materials by the coated beam method

The coated beam method has long been used extensively for investigating the dynamic elastic characteristics of vibration damping materials. With this method, the beam is coated with the damping material on one side, or on both sides, and the resonances of bending vibration of the metal and coated beam are investigated for the determination of the dynamic characteristics. It is known from the experiments that in the case of a relatively thin, or soft, coating the error in the result of the investigation may be very large. However, the technical literature to date has not been concerned at all with the mathematical analysis of the error for a beam coated on one side, and the error analysis published for a beam coated on two sides cannot be considered complete. Therefore, a complete error analysis for both beams is discussed in this paper. Relationships and diagrams are given by which the error in the dynamic characteristics can be calculated. Moreover, a few measurement results are discussed that can be well explained on the basis of the error analysis performed.

The elastic anisotropy of polycaproamide film

Published information about the mechanical anisotropy of oriented polymers is scant [I]. Film is the most convenient material for investigating the physicomechanlcal properties of polymers at various angles to the axis of orientation. In this article the results are reported of a study of the anisotropy of the elasticity and tensile strength of monoaxially oriented polycaproamide (PCA) films produced on experimental apparatus. The specimens were stretched to a varied draw ratio at a temperature of 170°C and a stretching speed of 46 m/ min. The dynamic elastic characteristics (Young's modulus and the modulus of shear) were determined by the acoustic method from the propagation rate of longitudinal and transverse ultrasonic waves [2]. The measurements were carried out by the pulse method at a frequency of 50 kHz with a measurement error of less than 1%. The ultimate tensile strength and relative elongation of the specimens were determined on an RM-30 tensile testing machine (clamped length i0 mm, rate of load application 200 mm~min). All experiments were carried out at a temperature of 23 ± 2°C and a relative humidity of the air of 65 ± 2%.