Damping Elements Research Articles

Mechanical and electrical properties of Cu-Steel bimetallic porous composite with a double-helix entangled structure

Cu-steel bimetallic porous composite structures can be used as lightweight, damping, and electro-conductive elements in critical environments where traditional single materials become ineffective. In the present work, a novel Cu-steel bimetallic porous composite with a double-helix entangled structure was developed. The mechanical properties (static stiffness, loss factor, and tangent modulus) of the as-synthesized composite were characterized by compressive tests, and its electrical sensitivity to compressive force was examined by mechanical–electrical coupling tests. The effect of the copper/steel weight ratio on mechanical and electrical performances was analyzed in detail. It is found that the Cu-steel bimetallic porous composite with a relatively high weight ratio has a larger average loss factor and lower stiffness than that with a low weight ratio. The structural characteristics and complex microstructural changes of the deformed specimen allow the tangent modulus and stiffness to exhibit a non-proportional relationship with the weight ratio over a range of displacement. The resistance-force curves exhibit an obvious nonlinearity and degradation due to the contact between internal bimetallic wires. The resistance-stiffness history reveals that the mitigation of electrical conductivity continued with the enlargement of stiffness and weight ratio.

Properties of a multi-layer multi-span corrugated package

In this article we deal with the problem of cyclic compression of a multilayer multi-span corrugated package by using the finite element method (FEM) and a three-dimensional model (3-D model) of deformation in Ansys. We take into account plastic deformation of the package, as well as the complex law of its propagation and mutual elastic slippage with dry friction over tops of corrugation and in local regions at the tops of corrugation along the package tapes, valid for any geometrical shape of corrugation. This solution can be considered as the second part of the general complex nonlinear problem of cyclic compression of a multilayer multi-span corrugated package with dry friction on contact surfaces. The solution obtained makes it possible to construct any loading processes in the field of elastic-hysteresis package loops. The comparison of elastic-frictional characteristics of the package (EFCs) obtained by calculation and the experimental ones showed their good agreement. The influence of the corrugated package parameters on its EFCs was studied. A number of properties of the package were determined allowing us to draw conclusions and formulate recommendations that make it possible to define the number of package tapes, the required accuracy in the manufacture of corrugations of its tapes, and the choice of the geometric shape of corrugations in almost all cases of practical use of corrugated packages. The solution obtained can be used to determine the effectiveness of a bumper and other protective devices during crash tests of a car for frontal and side impacts and to determine the optimal parameters of these devices by calculating. Certain results and recommendations of this paper can be useful for the calculation of parameters of damping elements of a blisk, hollow wide-chord blades of aircraft GTE fans, ring dampers of rocket engine rotors, as their damping elements are made in the form of multilayer, multi-span corrugated packages.

Validating the Deployment of a Novel Tether Design for Orbital Debris Removal

With the global push to commercialize space, humans are launching objects into orbit faster than natural effects are removing them. Orbital debris is especially dangerous because it is capable of exponential growth due to cascading collisions between orbiting objects. To ensure the long-term accessibility to space, high-risk objects must be actively removed to limit growth of the orbital debris population. One method of active debris removal is with a tethered net to capture and tow an object out of orbit. This work presents the validation of a proposed novel tether configurations deployment dynamics. Tether elements are simulated using two numerical models: a lumped mass node system connected by massless spring–damper elements, and an absolute nodal coordinate formulation model. Their accuracy to predict the deployment motion of a tether is experimentally determined, and a complete capture scenario using the novel tether design is presented for the first time.

Numerical study of acoustic transmission across heavily damped plate using hybrid Ray-Tracing-SEA method

Energy transmission across lightly damped structures has been well studied including the approved success of statistical energy analysis in mid and high frequency bands. For heavily damped elements, the diffuse field theory, which is used in computing coupling loss factors, tends to fail. Energy attenuation with distance becomes more significant for such elements and hence the energy is less likely to be evenly distributed within those elements. A ray tracing algorithm is developed taking account of this phenomenon by tracking the travel history of a great number of discrete rays. The predicted transmitted energy is used in a modified statistical energy analysis model to calculate energy level difference between different subsystems. Numerical validation and comparison on a concrete five-plate system are conducted in both lightly damped and heavily damped cases. Both the classic and the hybrid models show good agreement for lightly damped system and differ for heavily damped system. The difference tends to become larger with increasing frequency and internal damping level. The parameter “effective length ratio” is proposed to describe the phenomena of energy concentration along the edge and as in indicator of whether the application of diffuse field theory is appropriate.

Energy-Based Cooperative Control for Landing Fixed-Wing UAVs on Mobile Platforms Under Communication Delays

The landing of a fixed-wing UAV on top of a mobile landing platform requires a cooperative control strategy, which is based on relative motion estimates. These estimates typically suffer from communication or processing time delays, which can render an otherwise stable control system unstable. Such effects must therefore be considered during the design process of the cooperative landing controller. In this letter the application of a model-free passivity-based stabilizing controller is proposed, which is based on the monitoring of energy flows in the system, and actively dissipating any given active energy by means of adaptive damping elements. In doing so, overall system passivity and consequently stability is enforced in a straightforward and easy to implement way. The proposed control system is validated in numerical simulations for round trip delays of up to 4 seconds.

Material Damping in Dynamic Analysis of Structures (With LIRA-SAPR Program)

Abstract The purpose of this paper is to justify that it is necessary to take account of physical and mechanical properties of soil and different materials of erected structure for damping vibrations in dynamic loads; to suggest tools for modelling the damping effect (natural or engineering induced) between foundation and soil. Certain technique is suggested for modelling behaviour of structure in time history analysis with account of material damping. In the software, the damping effect is modelled in two variants: Rayleigh damping (for structure) and finite element of viscous damping. When solving this problem, the following results were obtained: physical meaning of material damping is described; Rayleigh damping coefficients were computed through modal damping coefficients. Numerical analysis is carried out for the structure together with soil in earthquake load using developed FE of viscous damping. Time history analysis was carried out for the problem. Peak values of displacement, speed and acceleration at the floor levels were compared. Analysis results are compared (with and without account of material damping). Significant influence of damping on the stress-strain state of the structure is confirmed. Scientific novelty of the paper is in the following: the damping effect is proved to happen regardless of the presence of installed structural damping equipment; technique for account of damping with Rayleigh damping coefficients is developed; new damping element is developed – FE of viscous damping (FE 62), its behaviour is described as linear mathematical model. Practical implications of the paper: developed technique and new FE enables the user to carry out numerical analysis properly and work out a set of measures on seismic safety for buildings and structures.

Parameter identification of the dynamic Winkler soil–structure interaction model using a hybrid unscented Kalman filter–multi-objective harmony search algorithm

Soil–structure interaction is a key aspect to take into account when simulating the response of civil engineering structures subjected to dynamic actions. To this end, and due to its simplicity and ease of implementation, the dynamic Winkler model has been widely used in practical engineering applications. In this model, soil–structure interaction is simulated by means of spring–damper elements. A crucial point to guarantee the adequate performance of the approach is to accurately estimate the constitutive parameters of these elements. To this aim, this article proposes the application of a recently developed parameter identification method to address such problem. In essence, the parameter identification problem is transformed into an optimization problem, so that the parameters of the dynamic Winkler model are estimated by minimizing the relative differences between the numerical and experimental modal properties of the overall soil–structure system. A recent and efficient hybrid algorithm, based on the combination of the unscented Kalman filter and multi-objective harmony search algorithms, is satisfactorily implemented to solve the optimization problem. The performance of this proposal is then validated via its implementation in a real case-study involving an integral footbridge.

Prediction of acoustic transmission in heavily damped system using hybrid Ray-Tracing-SEA method

Classic statistical energy analysis mainly deals with the energy transmission of system with relatively low damping. With the application of passive damping treat- ments, one of the fundamental assumptions in SEA, i.e., a diffused field, tends to fail. The energy attenuation along transmission path becomes so significant that there may exist large energy level difference within one structural component. In light of this, this study proposes to use a hybrid ray-tracing-SEA method to predict the acoustic transmission in heavily damped system. Heavily damped structural compo- nents are treated as â–œcoupling elementsâ–? instead of normal â–œsubsystems.â–? The en- ergy transmission from one structural element to a connected structural element through the edge can be represented by using certain number of point sources and assuming each point source radiates certain number of acoustic rays. By tracing the travelling history of each ray, the energy attenuation along the travelling path can be achieved. With the information of energy input and energy attenuation, the equivalent coupling loss factors can be computed. By rebuilding a hybrid ray- tracing-SEA model, the energy level differences between different subsystems can be determined. Numerical validation of the ray tracing algorithm is conducted by comparing the calculated coupling loss factor with normal SEA method. Numerical study of a one-room system is given. The room is assumed to consist of six homoge- neous concrete plates and the analysis assumes no coupling between in-plan and out- plane waves. Comparisons between classic and hybrid method show that when a small number of the structural components are heavily damped, classic SEA gives similar results with the hybrid method because the prediction errors tend to cancel with each other and the transmission is dominated by paths that are not damped. With the increasing number of damped elements, SEA tends to underestimate the energy level difference.

Optimum design of electromechanical vibration isolators

Conventional vibration isolators have been used for a long time to isolate a receiver from a source of disturbance. Probably, the most popular example of vibration isolators can be found in automotive suspensions. In vehicles, the spring and damper elements are used to damp road vibration and also to maintain drive handling stability. In this process, the mechanical energy is converted into heat and dissipated in the damper element. The idea of recovering part of the energy has become an attractive topic among researchers over the last three decades. In this context, this study investigates the possibility of replacing the damper element with an electrical circuit coupled to the mechanic system using a permanent magnet/coil transducer. Different electrical circuit configurations are analyzed to study the influence of damping on the mechanical system. Expressions to obtain critical damping and optimum damping to reduce the maximum peak in the frequency response are developed and presented in tabular form for ease of reference. The methodology is then applied to a two-degree-of-freedom system representing a quarter-vehicle suspension model. The results show that coupled electrical circuits can be used to replace fluid dampers in the design of vibration isolators without performance loss.

Influence of contact points of helicopter skid landing gears on ground resonance stability

Soft-in-plane rotor systems are susceptible to a self-induced vibration phenomenon called ground resonance. This dynamic instability results from lag motions of the rotor blades coupling with airframe degrees of freedom, while the helicopter is in ground contact. As an addition to slope landing studies in the past and investigations of non-linear landing gear effects, this work focuses on a systematic study of partial skid contact. A ground resonance test environment was created. It encompasses 3D helicopter models with flexible landing gear models using direct finite-element models and applying modal reduction to embed CAD-derived landing gear models. Both approaches are used in a multibody dynamics simulation. The models showed acceptable results for the simulation of non-linear dynamic behaviour including typical non-linear effects like limit cycles. Special focus is given to different methods of contact simulation, using 3D spring–damper elements and polygonal contact elements for multi-directional contacts. The simulations showed two counteracting effects for partial ground contact and time-variant contact conditions. On one hand, the reduction of restoring forces in partial ground contact should lead to more unstable conditions. On the other hand, energy dissipation shows a larger influence on the system stability behaviour after a sudden disturbance. This effect is of high interest for soft, partial landing conditions.

Modern Applications of Aluminium Foams

The implementation of aluminium alloy foam has more and more attention. Application of closed cell aluminium foam has made an impact in automobile and aerospace applications where crash energy absorption, vibration and weight reduction are obligatory [1,2,3]. The aluminium alloy foam is an advanced lightweight material providing high strength and stiffness at relatively low density. The technological use of aluminium alloy foam is difficult with the currently available technologies. In the case of open cell aluminium foams, the most common research areas for application are heat exchanger components, filters and sound damping elements [3]. The manuscript focuses on the manufacturing techniques of the aluminium alloy foams according to the application areas. First step is the investigation of the requirements for the application: what are the loads and the circumstances and why can we use aluminium foams. Second step is the knowledge of the producing methods of the foam or the component. And the last step is the investigation of the possible testing methods.

Modern Applications of Aluminium Foams

The implementation of aluminium alloy foam has more and more attention. Application of closed cell aluminium foam has made an impact in automobile and aerospace applications where crash energy absorption, vibration and weight reduction are obligatory [1,2,3]. The aluminium alloy foam is an advanced lightweight material providing high strength and stiffness at relatively low density. The technological use of aluminium alloy foam is difficult with the currently available technologies. In the case of open cell aluminium foams, the most common research areas for application are heat exchanger components, filters and sound damping elements [3]. The manuscript focuses on the manufacturing techniques of the aluminium alloy foams according to the application areas. First step is the investigation of the requirements for the application: what are the loads and the circumstances and why can we use aluminium foams. Second step is the knowledge of the producing methods of the foam or the component. And the last step is the investigation of the possible testing methods.

Influence of Elastomer Layers in the Quality of Aluminum Parts on Finishing Operations

In finishing processes, the quality of aluminum parts is mostly influenced by static and dynamic phenomena. Different solutions have been studied toward a stable milling process attainment. However, the improvements obtained with the tuning of process parameters are limited by the system stiffness and external dampers devices interfere with the machining process. To deal with this challenge, this work analyzes the suitability of elastomer layers as passive damping elements directly located under the part to be machined. Thus, exploiting the sealing properties of nitrile butadiene rubber (NBR), a suitable flexible vacuum fixture is developed, enabling a proper implementation in the manufacturing process. Two different compounds are characterized under axial compression and under finishing operations. The compression tests present the effect of the feed rate and the strain accumulative effect in the fixture compressive behavior. Despite the higher strain variability of the softer rubber, different milling process parameters, such as the tool feed rate, can lead to a similar compressive behavior of the fixture regardless the elastomer hardness. On the other hand, the characterization of these flexible fixtures is completed over AA2024 floor milling of rigid parts and compared with the use of a rigid part clamping. These results show that, as the cutting speed and the feed rate increases, due to the strain evolution of the rubber, the part quality obtained tend to equalize between the flexible and the rigid clamping of the workpiece. Due to the versatility of the NBR for clamping different part geometries without new fixture redesigns, this leads to a competitive advantage of these flexible solutions against the classic rigid vacuum fixtures. Finally, a model to predict the grooving forces with a bull-nose end mill regardless of the stiffness of the part support is proposed and validated for the working range.

Effects of Spring and Damper Elements in Aircraft Landing Gear Dynamics

In this study a typical Aircraft Landing Gear with shock absorber was modeled a Mass-Spring-Damper System. Basic components of the system were explained. The equations of the model was presented. Aircraft Landing Gear was also modeled in Matlab/Simulink for a given set of aircraft parameters. A case study for an Aircraft Landing Gear was solved and results were presented. Results included the variation of spring (k1 and k2) and damping coefficient (b) in a given interval to show their effects on the impact force and displacement of landing gear as main outputs to consider. Effect of damping coefficient (b) on impact force was found to be highest (3.76%), spring coefficient (k1) effect is moderate (2.29%), and spring coefficient (k2) is lower (0.97%), for a change of ±10% of coefficients.

Use of Dynamic FEA for Design Modification and Energy Analysis of a Variable Stiffness Prosthetic Foot

Different tasks and conditions in gait call for different stiffness of prosthetic foot devices. The following work presents a case study on design modifications of a prosthetic foot, aimed at variable stiffness of the device. The objective is a proof-of-concept, achieved by simulating the modifications using finite element modeling. Design changes include the addition of a controlled damping element, connected both in parallel and series to a system of springs. The aim is to change the stiffness of the device under dynamic loading, by applying a high damping constant, approaching force coupling for the given boundary conditions. The dynamic modelling simulates mechanical test methods used to measure load response in full roll-over of prosthetic feet. Activation of the element during loading of the foot justifies the damped effect. As damping is in contrast to the main design objectives of energy return in prosthetic feet, it is considered important to quantify the dissipated energy in such an element. Our design case shows that the introduction of a damping element, with a high damping constant, can increase the overall rotational stiffness of the device by 50%. Given a large enough damping coefficient, the energy dissipation in the active element is about 20% of maximum strain energy.

Modal analysis of FIAT Bogie of LHB railway coach

The Free vibration response of the Railway Bogie is an important area in the design of the Rail coach and to improve the ride comfort of the passengers. In this study, the railway Bogie considered is Fabric Italina de Automobil Torino, Switzerland (FIAT) Bogie of Linke Hofmann Busch (LHB) AC 3 Tier coach. This paper aims at the study of the vibration response of a FIAT Bogie of coach subjected to free vibration and to find the Natural frequencies of vibration and mode shapes. The geometric model FIAT Bogie and other related components is modelled using Solid works 2016 package and analyzed using numerical simulation package ANSYS 19.1 Workbench. The Primary and Secondary suspension systems and various dampers used in FE analysis are modelled as spring and damper elements respectively. In this work, free vibration analysis or modal analysis of the FIAT railway bogie is carried out to extract the first few modes of vibration. The Natural frequencies obtained along with the corresponding mode shapes of the bogie show that they are within the permissible range specified by the standards of railway department also for better ride comfort of the passenger.

Nonlinear Dynamic Modeling for Joint Interfaces by Combining Equivalent Linear Mechanics with Multi-objective Optimization

The nonlinear dynamic modeling by combining the equivalent linear mechanics with the multi-objective optimization algorithm is proposed to describe the nonlinear behaviors of the joint interfaces. The joint interfaces are simplified as the equivalent virtual material or linear spring–damper element. The genetic algorithm for multi-objective optimization is then used to identify the mechanical properties of the equivalent joint by minimizing the error between the simulated dynamic characteristics and the experimental results, including the modal frequencies of the bolted joint beam and the frequency response functions (FRFs) of the rubber isolation system. The FRFs are divided into several subsections with frequency-varied dynamic properties of the joint to consider the nonlinear dynamic behaviors, and the effects of subsection number and excitation amplitudes on the FRFs are also investigated. The results show that the simulated dynamic characteristics of modal frequencies and FRFs agree well with the experimental results. With the increase in the subsection number, the simulated FRFs agree better with the experimental results, indicating a good performance of modeling the nonlinear dynamic behaviors of the joint interfaces forced by different excitation amplitudes. Larger excitation amplitudes will decrease the joint stiffness.

Analysis of vibration high-frequency dynamic characteristics of wheelless rail vehicle system based on fuzzy logic control

Track irregularity is the main source of vibration excitation of vehicle-track weighing system, which has an important impact on the safety, stability and comfort of train operation, and it is also the main factor limiting the speed of train operation. Higher requirements are put forward for track smoothness with the rapid development of China’s railways. Therefore, it has a great theoretical and practical significance to study the relationship between track irregularity and random vibration of vehicle-track cooker-in system and the evaluation method of track smoothness. In this paper, a model construction method is proposed based on machine learning fuzzy logic control and neural network algorithm to analyze the high frequency dynamic characteristics of ballastless track wheel-rail vehicle system. Firstly, a numerical analysis model of high frequency dynamic characteristics of ballastless track wheel-rail vehicle system is established by using linear discrete elastic-yellow damper element connection model; Secondly, the Rough Set Block Neural Network is introduced to optimize the dynamic characteristic analysis model, and the intelligent model of model optimization analysis is established. Finally, the validity of the proposed algorithm is verified by simulation experiments of practical examples.

Seismic Design of the Box for the Gas Flow-Rate Metering Unit

To study seismic resistance of the box for the metering unit of gas flow-rate required to ignite the flare system we used the calculation methods developed on the basis of the method of finite elements and the software designed to define the mode of deformation and the dynamics of structures for the three-dimensional statement. To construct the simulation model, we took into account all the elements that affect the strength and the efficiency of the real structure during possible earthquakes. Structure elements were simulated using the sets of arbitrary oriented rods and lumped masses with inertia moments and those rods were connected absolutely rigidly with each other and using also elastically damped elements. The rod elements with distributed parameters took into consideration all the types of deformations that occur during the vibrations. The plate components of the structure were simulated using the grids made of the rods taking into consideration the ductility and inertia properties of its elements. Lumped masses in the rod connections were used to take into account the masses of installed equipment, pipelines, etc. The seismic loading was simulated using alternating inertia forces transferred from the ground. The soil ductility was taken into account by the Winkler model. Computations were done for the sand and rock stone ground and for the fine-grained sand. Consideration was given to the seismic forces of a different intensity that are represented by three-component accelerograms. Synthesized and real accelerograms were analyzed. The obtained computation data showed that the structure of the box of the metering unit of gas flow rate is quakeproof and it won’t be destroyed during its operation.

Dynamic Tensile Stress-Compressive Stress Behavior of Thermoplastic Matrix Composite Materials Reinforced with Continuous Fiber for Automotive Damping and Anti-Vibration Structural Elements.

Continuous Fibers-Reinforced Thermoplastic Composites (CFRTP) are presented as light materials, capable of offering a short production time with the possibility of being recycled. These properties make them ideal for automotive applications, aiming to reduce the consumption and emission of polluting gases. This article analyzed the dynamic tensile stress-compressive stress behavior of CFRTP in structural elements of the car with anti-vibration and damping functions. The data available in the literature on the reliable and usual compliance of the properties required for CFRTP, to be applied in the automotive structural elements, is scarce and insufficient. In order to analyze whether CFRTP feeds the demanding requirements of car manufacturers and if they provide advantages over the metal materials currently used, this article developed a method of reliable verification of their dynamic tensile and compression behavior. The methodology developed could be used as a guide to characterizing any combination of vulcanized rubber adhesive joints with CFRTP, regardless of the materials and additives used. The results obtained showed that there exists CFRTP that fits the requirements of the car manufacturers for this type of component and also offers dynamic advantages over the materials currently used as anti-vibration elements.