Vibration Damping Materials Research Articles

The problems of designing helicopters with regard to the requirements for cabin noise

High noise levels in helicopter cabins are currently an important problem in solving environmental problems in civil aviation. The published data indicate high noise levels in the cabins of operated helicopters of the order of 93-97.4 dBA, while noise levels of less than 80 dBA are safe for humans. In order to significantly reduce noise levels in helicopter cabins and ensure the required level of acoustic comfort for passengers, an integrated approach is proposed, consisting in the use of sound insulation and vibration damping materials in the on-board structure, as well as sound-absorbing structures configured to work effectively in the problematic frequency range of the helicopter passenger cabin.

Solution of the Problem of Parameters Identification for Vibration Damping Materials

Statement of the problem. For the design of vibration isolation systems of buildings, structures and hardware, it is necessary to have information on the dynamic characteristics of vibration damping materials. These parameters are recommended to be determined on the basis of tests as per GOST 16297-80 or GOST R ISO 10846-1-2010. At the `same time, these methods are limited by the model used in them – a single-mass oscillatory model of the Kelvin-Voigt type and cannot fully assess both the dynamic and rheolo-gical characteristics of materials. Results. The use of a variety of dynamic models of materials allows one to improve the accuracy of describing their properties and predict the behavior of vibration isolation systems over time. Conclusion. The algorithm presented in the article for identifying the parameters of vibration damping materials models allows one to use various models and more accurately describe the properties of materials.

Шумоизолирующий кожух с резонаторными элементами

Constant exposure to industrial noise has a negative impact on the human body. That is why increased attention is paid to the fight against noise, the rationing of industrial noise and vibrations was adopted. One of the effective methods to reduce the noise emitted by the operating equipment is the use of noise-insulating casings. The casing, as a rule, contains an outer skin made of steel sheet, a sound-absorbing lining of the inner skin, a perforated lining of a sound-absorbing coating. A typical octave spectrum of radiation sound pressure levels near the machine has a maximum near the frequency of 500 Hz, and the highest casing efficiency (insertion loss) is achieved in the frequency range of 1000–4000 Hz. The purpose of the study presented in the article is to improve the acoustic properties of the noise-insulating casing in the medium and low-frequency sound spectrum. To accomplish this task, the author proposes integrating resonator elements, in particular, Helmholtz resonators, into the structure of the noise-insulating casing. The natural resonant frequencies of Helmholtz acoustic resonators are determined considering their necessary frequency tuning, which ensures effective suppression of sound radiation at discrete values of the operating dominant frequencies of operating equipment. To reduce the excitation of structural vibrations and sound, as well as additional sound insulation, the frame walls and casing covers are damped on the outside and inside with a layer of vibration-damping material. Significant absorption of sound waves generated by operating equipment is ensured by lining the casing walls with effective sound-absorbing panels made of porous material, lined, in turn, with an external protective sound-transparent layer. The design of a noise-insulating casing with resonator elements presented in the study has high acoustic properties in a wide frequency range. Helmholtz resonators built into the casing structure provide sound absorption in 1/3 octave frequency bands centered at 400 and 500 Hz, characterized by a resonant amplification of the sound emitted by the equipment discussed in the article.

Reduction of Watercrafts Vibroacoustic Activity by Vibration Damping Materials

Introduction. Electric machines, diesel installations, pumping units and fans, as well as working bodies of dredgers (pipelines, scoops, rippers, etc.) are the main sources of noise and vibration on watercrafts. Moreover, the main harmful factors in the operation of floating cranes and dredgers are both the vibration itself and the accompanying phenomena of infrasound and structural noise. One of the most urgent tasks for the introduction of technosphere safety methods on watercrafts is to reduce the harmful effects of vibroacoustic factors on the health of personnel. The research objective is to improve the working conditions of watercrafts drivers by introducing the method of designing vibration protection systems proposed by the authors, taking into account both the external factors (ambient temperature) and the dynamic characteristics of vibration damping materials. The possibility of choosing the most rational vibration damping material based on the engineering calculation of the required vibration insulation is shown. Materials and Methods. A passive method of vibration control has been applied, in which elastic elements and vibration damping material are used in the watercraft design. The sources of noise and vibration have been identified, and their actual exposure levels have been determined. The analysis of dynamic characteristics and properties of vibration damping materials is carried out. The factors influencing the efficiency of vibration damping are revealed. Results. A design scheme of the vibration damping model at the workplace of the watercraft driver has been developed. An analytical database of dynamic characteristics and properties of vibration damping materials has been created. An engineering method for calculating the effectiveness of vibration insulation has been adapted to watercrafts. The calculations of the effectiveness of vibration insulation using various vibration damping materials of different thicknesses have been performed, on the basis of which the advantages of vibration damping flooring made of elastomeric plate VEP20 have been proved. Discussion and Conclusion. The engineering methodology developed in Excel for calculating the effectiveness of vibration insulation is automated and has a user-friendly interface. This allows you to calculate and reasonably select multilayer structures taking into account the ambient temperature, as well as the dynamic characteristics of vibration damping materials depending on the spectrum of noise and vibration. The results obtained can be used in the design of vibration protection systems for watercraft drivers.

Design and Investigation of a Fiber Bragg Grating Tilt Sensor With Vibration Damping

Fiber Bragg grating (FBG) sensors play an increasingly important role in structural health monitoring, and tilt sensors are one of the most commonly used among them. Traditional FBG tilt sensors are easily affected by external vibration, and to overcome such a problem, this work proposes a novel FBG tilt sensor with a vibration damping feature. Based on the classical equal strength beam structure, a vibration-isolating spring is used as the vibration-damping connection between the beam and the mass block, while a damping fluid is filled inside the sensor housing as the vibration-damping material. After elaborating on the details of sensor structural design and measurement theory, five sensors were set up for relevant performance tests, and the controlled experiments were carried out for the FBG sensors with and without the vibration isolation springs. Meanwhile, for sensors with vibration isolation springs, the viscosity of filled damping fluid was also varied in the experiments, to better reveal its influence on the sensor performance. The experimental results show that the proposed sensors have a high sensitivity of 112.743 pm/° within a range of ±15° and also have superior creep resistance as well as good temperature compensation capability. From controlled experiments, it is evident that the proposed sensor with a vibration damping structure offers better vibration stability and monitoring accuracy and can be effectively adapted to safety monitoring tasks in different engineering applications by simply adjusting the viscosity of filled damping fluid.

Anomalous impact and vibration damping by liquid crystal elastomers

Anomalous impact and vibration damping by liquid crystal elastomers Liquid Crystal Elastomers (LCE), invented over 30 years ago, have been considered a highly promising material system for soft actuators and artificial muscles ever since. In this second academic piece for Open Access Government, Professor of Polymer Physics, Eugene M. Terentjev explores the anomalous impact and vibration damping by liquid crystal elastomers. There is considerable interest in developing thin conformal coatings of materials that can efficiently dissipate mechanical energy, thus suppressing vibration and noise and protecting from impacts. Traditionally, to create vibration-damping materials one exploits the loss aspect of the viscoelastic response when the energy dissipates as heat in either free or constrained layer configurations.

Toughening static and dynamic damping characteristics of ultra-high performance concrete via interfacial modulation approaches

The damping capacity is one of major concerns for structures under dynamic loads, which significantly affects the safety and service life. Ultra-high performance concrete (UHPC) is a new generation of cementitious material characterized by superior mechanical strength and durability, exhibiting enormous potential in application to innovative structures. However, the weak steel fiber-matrix interface within UHPC leads to insufficient damping performance and poses threats to UHPC structures under extreme dynamic loading conditions. In this paper, various interfacial modulation approaches were investigated to improve static and dynamic damping properties of UHPC, including physical shape and chemical modification of steel fibers, macrofibers and microfibers hybridization. Results show that the interfacial modulation can significantly enhance damping ratio, loss factor and energy dissipation ratio of UHPC, where the chemical modification of steel fibers endows the highest damping ratio. The loss factor and energy dissipation ratio of UHPC reach 0.579 and 0.091 after interfacial modulation, which improved by more than 110% and 100%, respectively. The working mechanisms behind variations of damping performance are attributed to the toughening in interfacial bond and load transfer, leading to improvement in energy dissipating ability of interface. Furthermore, a comprehensive comparison between UHPC and existing vibration damping materials was conducted through multi-criteria analysis from the perspectives of damping performance, mechanical strength, processability and economic benefit, and UHPC with chemical modification of steel fibers exhibits the best overall performance. The findings contribute to inspiring a novel structural vibration control strategy through UHPC with enhanced static and dynamic damping properties for resisting extreme loads.

Sustainable Applications of Tyre-Derived Aggregates for Railway Transportation Infrastructure

Scrap tyres are used to produce tyre-derived aggregates (TDA), which can be used as fill material, backfill material, drainage layers, and vibration-damping material, among other uses. This study presents a comprehensive review of TDA applications in civil engineering with a specific focus on railway projects. A review of the existing literature reveals the lack of sufficient knowledge on the use of TDA in slab tracks. This article also analyses the adequacy of different constitutive models to properly simulate the performance of TDA while highlighting the importance of adopting the most suitable constitutive model. The variations in shear stresses and displacements with depth below ballasted and slab tracks in the presence and absence of TDA are discussed. It is shown that TDA effectively reduces the shear stresses for the subgrade layer of both track types. Moreover, the impact of TDA on stress transfer in the vertical and lateral track directions is assessed. The findings from the present analysis reveal that TDA helps in reducing the vertical and lateral stresses near its placement position in ballasted and slab tracks.

The Relationship of the Polymer Molecular Structure and the Dynamic Mechanical Property Under High Pressure

The dynamic mechanical properties of the viscoelastic polymer materials are usually considered to be the key parameters for the vibration damping or acoustic materials. The relationship between the molecular structures of the random copolymer butadiene styrene rubber (SBR) obtained through the anionic polymerization method and their dynamic mechanical parameters under high pressure is studied to explore the energy loss mechanism of the polymer materials applied in the special conditions such as high pressure. The dynamic mechanical parameters were tested though experimental methods with pressure chambers, which can supply high pressure to the polymer samples. The results show that the most important effect factor of the molecular structure is the ratio of the content of the stiffer segments composed of styrene in the SSBR molecular chain to the softer ones composed of 1, 4-butadiene. This can be attributed to the stiffer segments supplying bigger free volumes for the molecular motion and higher modulus to resist to the high pressure, and the softer segments endue the effective energy loss ability to the polymer chains. However, the mass ratio of the stiffer and softer segments should be in an appropriate range, which the content of the styrene must be less than 40%.

Processing of primary sludge of pulp industry as microfillers for polystyrene-based composite foams

Primary sludge as main byproduct wastes in a pulping industry still contain some biomass and potentially affects the environment when was not handled properly. The pulp industry primary sludge (PIPS) can be processed as microfiller for polystyrene-based foam composites for various engineering applications, such as sound and vibration damping materials. The PIPS has been dried, milled and shieved to 100-400 mesh particle sizes. Physical and chemical properties of the PIPS have been tested using: particle size analysis (PSA), FTIR spectroscopy, then its thermal properties using differential scanning calorymetry (DSC). Incorporation of the PIPS microfiller in maleic anhydride-modified polystyrene (MA-m-PS) matrices for composite foam was carried out in a reflux reactor in xylene solution using Tween 80 as surfactant under stirring. The composite foam was characterized, firstly based on their densities compared to that of fresh PS resin, then using electron microscopy (SEM) for morphology properties. It was found that mean particle size of the dried and milled PIPS powder was 14.84 μm and its biomass content was 10.5%. Result of FTIR spectroscopy showed that many of the selected characteristic bands of lignocelluloses overlap, specifically, the selected band 1366 cm-1 for cellulose is very close to the 1368 cm-1 selected for hemicellulose. Whereas result of and its decomposition temperature 549.86°C with heat of combustion 16.34 cal/g, which indicating suitability of the PIPS powder as filler for polymeric foam microcomposites. The result of morphology analysis of the PIPS-filled microcomposites foam based on MA-m-PS (optimum weight ratio of MA-m-PS/PIPS: 80/20, density 0.88 g/cm3), using SEM showed that PIPS microfillers were well distributed within the MA-m-PS matrices.

Prediction and Improvement of Aircraft Cabin Acoustics using Statistical Energy Analysis and Sound Quality Evaluation

Aircraft interior acoustic design is a key influencer for cabin comfort. An essential part of the design is optimization of acoustic insulation systems under weight restrictions to create a pleasant environment for human ear. Considering the complexity of aircraft geometry, noise sources, and transfer paths, computational prediction techniques become invaluable tools for increasing the accuracy in material selection while reducing design time and costs. In this study, a procedure that integrates sound quality evaluation with Statistical Energy Analysis (SEA) to design aircraft acoustic insulation systems is described. SEA is employed to predict the cabin sound pressure levels of a narrow body aircraft insulated with sound absorption and vibration damping materials. Aircraft cabin including under-floor sections is modelled based on 3D airframe and VIP style interior design and the model is validated with flight test data. Transfer functions obtained from SEA model for selected transfer paths are utilized to filter the noise signal recorded with a binaural recording system during flight. Sound quality metrics are computed in order to map perceptive response. An iterative process is introduced to improve acoustic design by investigating the effects of different sound insulation systems and room absorption values on noise levels and sound quality metrics.

Preparation of modified polyvinyl formal vibration-damping material and its application in strawberry.

Mechanical damage and microbial infestation were critical issues during strawberry transportation. This study prepared a modified polyvinyl formal (PVFM) vibration-damping material and investigated its application in strawberry transportation. This modified PVFM was primarily composed of polyvinyl alcohol, starch, formaldehyde, and allyl isothiocyanate. Our results showed that the modified PVFM had good vibration-damping and antifungal properties with 0.137g/m3 of density, a water absorption ratio value of 6.24, 278Pa of tensile strength, 3.86Pa of elastic modulus, a buffer coefficient of 0.318, and antifungal rates of 68.8% and 80.6% against Bacillus anthracis and Botrytis cinerea, respectively. Moreover, this modified PVFM could enhance the storage life of strawberry by improving PAL activity from 376 to 3,125U/g, inhibiting POD activity with a maximum value of 3.1U/g, and decreasing CAT activity from 324 to 35U/g. The modified PVFM presented a good vibration-damping capacity and the potential to extend strawberry shelf life. PRACTICAL APPLICATIONS: Berry fruits were vulnerable to mechanical damage caused by vibration during transportation, resulting in quality deterioration, rot, and aging. In this study, modified polyvinyl formal (PVFM) was prepared and was of low density and displayed good mechanical, vibration-damping, and antifungal properties. The modified PVFM could improve the storage life of strawberry. Thus, the modified PVFM could have potential application in berry fruits transportation.

Experimental research and simulation of vibration isolation elements mounted within transport boxes

Military vehicles, destined either for transportation of goods and personnel, or for battle missions, move in most situations on unpaved roads. Average movement speed is limited by suspension performances, which have to ensure a constant contact between vehicle’s wheels and rolling track. Other factors with influence on minimum movement speed on heavy terrains (imposed by specific standards: STANAG - Standardization NATO Agreement) are represented by driver’s physical resistance and behaviour of goods when submitted to shocks and vibrations. For the driver’s comfort there can be used independent suspensions for chairs, but in case of transported goods is more difficult, especially when the cargo is fragile and expensive (communication equipment, radars, IT etc.). Therefore, it is very important to study means to reduce vibrations and shocks, using vibration damping materials. Experimental research conducted within present study aimed to analyse vibration isolation elements made of rubber, which have been mounted inside transport boxes. This solution is important to be interoperable and ensure a simplified version of logistics, with the use of containers or standardized transport boxes. Experimental tests aimed to determine material properties, which have not been provided by the manufacturer, and the results have subsequently been used for modelling-simulation of vibration isolation elements behaviour. Virtual model was validated by experimental research consisting in applying composed axial stresses to the analysed materials.

Development of vibration damping materials based on butyl rubber: A study of the phase equilibrium, rheological, and dynamic properties of compositions

AbstractA detailed study of butyl rubber‐based vibration damping formulations linking their composition, morphology, phase structure, viscosity, mechanical loss factor, and other characteristics is presented for the first time. High performance of the compositions including aromatic petroleum oil is explained by limited solubility of the plasticizer that leads to the formation of a highly‐viscous emulsion (η20°C ≈ 1000 Pa·s) consisting of a swollen butyl rubber matrix and dispersed oil droplets in the broad composition range. Chalk is found to be the best inorganic filler as its spherical particles provide strong adhesion to the reinforcing layer of aluminum foil. Aiming to eliminate ecologically unfriendly aromatic compounds, a new low‐cost binding agent formulation based on butyl rubber mixed with polyisobutylene and highly refined mineral oil is suggested. Being environmentally safe, it possesses high viscosity of 1000–3000 Pa·s, cohesion strength of 3.5–5.0 N/cm, penetration of 4.5–6.0 mm, and mechanical loss factor up to 0.34 at room temperature, which are as good as, or even better than, the properties of currently produced vibration damping materials containing aromatic compounds. New materials can be used in car and aircraft parts for effective vibration isolation.

REDUCING OF EXTERNAL NOISE ARMED VEHICLE “DOZOR-B” APPLICATIONS TO DUMPING COATING

There has been a war in Ukraine for 6 years. In this regard, the production of military equipment has increased significantly, including. armored vehicles. Serious requirements are imposed on any military equipment. This paper focuses on the reduction of the external noise of the Dozor-B armored vehicle both in terms of ecology and in terms of camouflage. The technical characteristics of the mentioned armored car and its main sources of noise are briefly discussed. It is concluded that the body emits a significant level of noise, and therefore it is important to reduce the total external noise of the armored car by reducing the noise emitted by the body of the latter. The dissertation work of Krutolapov V.Ye. was analyzed. "A method of improving the vibroacoustic characteristics of the car body using vibration damping materials." The dissertation deals with the method of measuring the amplitude-frequency characteristic of a plate with a damping coating, called "obst". We have pointed out the disadvantages developed by Krutolapov V.Ye. bituminous coated plates and suggested their solution. A method of reducing the level of external noise of armored vehicles by coating their housings with a multilayer damping coating is proposed. The algorithm of calculation of the mentioned covering is developed. The choice of the necessary materials is made on the basis of their acoustic properties, heat resistance and cost. The number of coating layers is calculated based on the required acoustic effect, cost and weight of the structure. The acoustic efficiency of the developed three-layer damping coating was calculated, as well as the estimation of the external noise reduction of the Dozor-B armored car for a number of speeds of the latter on the main cycle on the road due to the application of this coating. Keywords: transport, armored car, armed forces, fire support machine, military equipment, engine, power unit, noise, camouflage, ecology, noise source, housing, acoustic efficiency, wave impedance, sound penetration coefficient, multi-layer vibration damping material.

ВИБРОАКТИВНОСТЬ МАЛОШУМНЫХ ВЕНТИЛЯТОРОВ

Low-noise fans are widely used in the sphere of human life for sanitary and technological purposes. Creation of low-noise fans is currently an advanced scientific and technical area. In some fields of their application, reduced vibrations and noises are of paramount importance not only in terms of sanitation and health, but also from a scientific point of view. This work presents a comparison of the quality of low-noise fan development depending on the selected resistance type. The efficiency of the damping of mechanical system (a low-noise fan) vibrations according to the type of resistance moment used is confirmed analytically and practically. Nowadays, a number of fan types implemented in hundreds of designs have been developed and are in service. In this work, the whole variety of the produced nomenclature of low-noise fans is reduced to two basic types – axial and radial. The paper reports that to ensure minimum noise in the operating mode of the low-noise fans presented in the work, a wideband vibration damper is needed as a required functional unit, and the walls of the fan housing should be sandwich-like with layers made of sound absorbing, sound insulating, and vibration damping materials.

METHODS OF NOISE REDUCTION OF BRIDGE CRANE RAILS

Bridge cranes of various lifting capacities are intensively used in various industries and construction industries. Bridge cranes are a combination of diverse noise sources, such as electric motors and gearboxes for lifting and moving carriages, wheelsets and rails. One of the intensive sources of radiation of sound energy creating excess over sanitary standards are the rails. It should be noted that it is possible to reduce the noise levels of this particular source by installing vibration-damping materials, which actually provide not only a reduction in vibration levels, and, therefore, noise in the sources themselves, i.e. in an active way, but at the same time perform the function of sound insulation.

Effectiveness of Vibration-Damping Coatings

The effectiveness of vibration-damping coatings is assessed by simulation. The experimental characteristics of the coatings are presented. An algorithm is proposed for assessment of the expected dynamic parameters of structures as a function of their shape and the characteristics of the vibration-damping materials.

Temperature and Frequency Dependences of Dissipative Properties of Rigid Vibration-Damping Coatings

Abstract—A study of the temperature and frequency dependences of the mechanical loss factors and elastic moduli of polymeric materials allows one to calculate the efficiency of vibration-damping coatings on substrates of metals and rigid composites under specified operating conditions. The calculated and experimental data for different compositions of vibration-damping materials are compared. The studies are performed using polymer compositions on the basis of modified epoxy resins and reinforcing fillers.

Preparation of Sound Absorption Material Based on Interpenetrating Polymer Network (PU/PMMA IPN)

Background: Polymer composites with interpenetrated polymer network (IPN) structure are widely used as sound and vibration damping materials due to their high viscoelastic properties within the glass transition temperature range. In this study, polyurethane (PU)/poly (methyl methacrylate) (PMMA)-based interpenetrating polymer network with different ratios of PU to PMMA (i.e. 85:15, 75:25, and 65:35) were prepared by in situ polymerization. Methods: The properties of as-prepared IPN and its components were evaluated by different scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and sound absorption. Tensile properties were also determined. As indicators of effective damping capability, viscoelastic parameters including loss factor (tan δ), glass transition temperature (Tg), and effective damping interval (tan δ > 0.3) were also determined. In order to determine the sound absorption coefficient in the prepared IPNs, a two-microphone impedance tube at the frequency of one octave was used. Results: The comparison of pure polymers (i.e. polyurethane and polymethyl methacrylate) and prepared IPNs indicated that the semi interpenetrated polymer network morphology was created through a broader range of tan δ in different IPNs. Incorporation of PMMA into polyurethane in the form of interpenetrating polymer networks enhanced the damping acoustic properties of the semi-IPNs due to the permeability of the two polymers. In the temperature range of -50 to 11 ˚C, both IPNs components showed high damping characteristics (tan δ ≥ 0.3). Conclusions: Evaluation of the results indicated that the blends are capable of exerting viscoelastic effects for damping and sound attenuation.