Good Damping Research Articles

The Physical and Sound Absorption Property of Lightweight Rigid Polyurethane Composite Reinforced Bamboo Fiber for Roof Applications

Rigid polyurethane (RPU) foams as roof insulation have become increasingly popular in Southeast Asian countries and have been extensively used for absorbing sound and reducing noise because of their good sound damping, viscoelasticity, and low density. In this study, the RPU foam composite reinforced bamboo fiber was investigated by physical characterization by SEM, TGA, and FTIR, and the sound absorption was measured by the Impedance Tube Test. The morphology result of the RPU foam composite indicates the size of the diameter pore influenced the sound absorption by adding bamboo fiber as a filler. The thermal degradation of the presence of lignin in the bamboo fiber at the temperature range of 400 °C to 500 °C and the total weight loss is 76 % at 429 °C temperature. FTIR spectrum shows that the peak at 2890 to 2935 cm-1 are indicated –CH stretching vibrations and characteristics for bamboo fiber can be used in polymer composites. The sound absorption of RPU 25 foam composite reinforced bamboo fiber was found 0.74 absorbance at a frequency of 1250 Hz. RPU foam reinforced bamboo fiber as a filler has the highest transmission loss RPU 35 is 21 dB at a frequency range of 1600 Hz. The findings indicate by increasing the content of bamboo fiber as filler, the diameter of the open pore of RPU 25 and RPU 35 foam composite had the potential for sound absorption to absorb at low frequency to achieve greater sound absorption for roof insulation.

Coupled vibration of an annular plate-cylindrical drum structure with material-nonlinearity damping patches considering position-mistuned and stiffness-mistuned connections

Considering position-mistuned and stiffness-mistuned connections, the coupled vibration of an annular plate-cylindrical drum structure with material-nonlinearity damping patches is studied. These two mistuned connections are inevitable, but they are seldom concerned in published works. Moreover, the mistuned connections can cause local excessive vibrations, so vibration suppression is in demand. Spraying hard coatings with material nonlinearity is a good damping method. Their damping-related and stiffness-related parameters will change with strain, which will improve the vibration-reduction ability but bring obstacles to modelling. This paper focuses on the consideration of both mistuned connections and material-nonlinearity damping patches (MDP) and presents a general modeling method of connection-mistuned annular plate-cylindrical drum structures with MDP. Position-mistuned and stiffness-mistuned connections are emulated by developing the spring approach, and dynamic equations are created by combining Sanders’ shell theory, Kirchhoff’s plate theory, and Lagrange equation. Furthermore, the region decomposition approach is developed for considering the material nonlinearity, and an efficient solution is provided to solve the corresponding nonlinear complex equations. The study is adequately validated. Finally, numerical results indicate that mistuned connections cause the local-vibration behavior, frequency separation, and coupled vibration between substructures and modes. Moreover, mistuned connections also seriously affect the response curves and response cloud charts.

Nonlinear vibration control of functionally graded material beam coupled with NiTiNOL–steel wire ropes

This paper proposes a novel damping device, NiTiNOL–steel wire rope, which is a vibration absorber with linear hysteresis damping, nonlinear damping, and nonlinear stiffness. This study is the first to couple the NiTi–ST damping device with the functionally graded material beam model. The Runge–Kutta method and harmonic balance method are adopted to study the resonant response of the system from the numerical and analytical aspects, respectively. It proves that NiTi–ST provides effective vibration reduction for FGM beam structures. In addition, special attention is paid to the appearance of the closed detached response, which significantly affects the resonant peak value of the system. And the CDR phenomenon is eliminated by adjusting the parameters, and a good damping effect is achieved under large external excitation. Results confirm that NiTi–ST is a promising nonlinear damper that serves as a new method for the vibration suppression of continuum structures.

Magnetohydrodynamics analysis of magnetorheological fluid damper

A key feature of magnetorheological fluid is its variability of rheological properties in which upon exposing this fluid, the viscosity of the fluid changes accordingly. Hence this nature can be implemented in various engineering applications. To understand its influence in a magnetorheological (MR) damper, it is essential to study the flow behaviour using computational and numerical methods. The main objective of this work is to estimate the influence of the external magnetic field on the fluid flow velocity inside the damper using magnetohydrodynamic analysis. Finite element analysis, magnetostatic analysis, and magnetohydrodynamic (MHD) analysis have been carried out to investigate the change in the shape of the velocity profile across the flow gap of the monotube MR damper under the various magnitude of magnetic force using the MHD module of ANSYS fluent software. The simulation is conducted by considering laminar, steady-state, and incompressible fluid flow. In finite element analysis, the magnitude of magnetic flux density (MFD) ‘B’ was evaluated at various direct currents. Later, obtained MFD has been applied perpendicular direction to the flow of MR fluid. The effective length of the fluid exposed to the MFD is taken as 2 mm to 28 mm in an overall flow length of 30 mm. The extracted results have shown that the fluid flow velocity reduces with an increase in the magnetic flux density. It has been observed that 10.42 % reduction in velocity upon increasing the magnetic flux density from 0.25 T to 1 T at 75 kPa pressure. The reason for a reduction in velocity is because of variation in the rheological properties of the fluid under the magnetic field, which is very much essential to produce a good damping effect in the MR damper.

Vibrational loss analysis of a new type of phononic crystal with a tungsten block embedded inside a rubber matrix

Vibration and noise pollution is one of the main pollution in modern society. In order to obtain good vibration damping effect, more effective phononic crystals should be designed. Based on the theory of elastic wave propagation in solids, three types of phononic crystals are designed in this paper using tungsten blocks embedded in a rubber matrix, which are cup-shaped phononic crystal, solid cylindrical phononic crystal, and hollow cylindrical phononic crystal. Firstly, the band gap characteristics and vibration losses of the three phononic crystals are analyzed by using the finite element method. Secondly, the physical mechanism of band gap formation is explored by vibration modes. Finally, the cup-shaped phononic crystal was introduced into the core layer of the sandwich plate to form the cup-shaped phononic crystal sandwich plate, and its vibration damping performance was analyzed. The results show that the three phononic crystals can form three band gaps in the range of 0–800 Hz, and the first low-frequency band gap starts at about 140 Hz and is all wider than 200 Hz. It is noteworthy that the average loss of vibration transmission of the three types of phononic crystals is more than 69 dB, which possesses stronger damping capability and wider low- and middle-frequency band gaps than the flat plate type phononic crystals. The vibration direction of the phononic crystal is at an angle of 90° to the wave vector, which prevents the propagation of elastic waves. The phononic crystal embedded in the sandwich panel plate is more in line with the actual demand of vibration damping and obtains good vibration damping effect. The research in this paper can provide more feasibility for phononic crystal damping.

Theoretical and experimental research on damping performance of suspended multiple mass pendulums damper

Conventional suspended mass pendulum damper (SMPD) include suspended single mass pendulum damper (SSMPD), tandem suspended multiple mass pendulums damper without springs (TSMP), and parallel suspended multiple mass pendulums damper without springs (PSMP), these types of SMPD have the advantages such as clear mechanism, simple construction, and good damping effect, but they have a narrow tuning frequency band and the pendulum length needs to be set too long for low-frequency super tall structures and too short for high-frequency tall structures, limiting their application in practical engineering. Because of this, the paper proposes connecting the spring to the mass pendulum, forming a tandem suspended multiple mass pendulums damper with spring (TSMP-S) and a parallel suspended multiple mass pendulums damper with spring (PSMP-S), and establishing structural system dynamics equations and performing the dynamic characterization of the TSMP-S and PSMP-S, obtain their frequency resolved solutions to explain the damping mechanism. In order to study the vibration-damping performance of these two types of SMPD, through numerical simulations to compare the damping effect of the conventional SMPD, TSMP-S, and PSMP-S on the controlled structures, and a series of shaking table tests on controlled and uncontrolled structures to verify the effectiveness of SSMPD, TSMP, PSMP, TSMP-S and PSMP-S for damping control of controlled structures under conventional earthquake and earthquake at four types of sites. Numerical simulations and shaking table test results in both show that the TSMP-S has the best damping effect, with the advantages of increasing the tuning frequency band, achieving multi-order vibration control, and flexible adjustment of the pendulum length, which is suitable for actual engineering.

Study on the influence of 3D modification on dynamic characteristics of a herringbone gear transmission system

The 3D modification is an advanced technology that comprehensively considers tooth profile modification and axial modification to reduce vibration and noise. Therefore, this paper combines 3D modification technology with contact characteristics and dynamic properties to study the influence of 3D modification on the dynamic performance of a herringbone gear system. This paper employs a parabolic tooth profile instead of the cutter's straight tooth profile to achieve 3D-modified tooth surface and deduces the tooth surface equation. Then, tooth contact analysis (TCA) and loaded tooth contact analysis (LTCA) are used to simulate the meshing process of teeth. And the dynamic model of the herringbone gear system under three internal excitations is established. Finally, 3D modification, TCA, LTCA technology, and gear dynamic characteristics are combined to study the influence of 3D modification on the system's dynamic behavior. The results show that, compared with tooth profile modification and axial modification, the 3D modification can effectively compensate for the influence of errors on the gear system and have a very good damping effect. The relative vibration displacements on the left and right meshing lines of the gear pair are reduced by 47.60% and 51.20%, and the root mean square values are decreased by 30.50% and 36.10% before and after modification, respectively.

Solidification microstructure evolution and its correlations with mechanical properties and damping capacities of Mg-Al-based alloy fabricated using wire and arc additive manufacturing

Magnesium (Mg) alloys, as the lightest metal structural material with good damping capacities, have important application prospects in realizing structural lightweight and vibration reduction. However, their engineering application is greatly limited by poor plastic formability. Wire and arc additive manufacturing (WAAM) provides a potential approach for fabricating large-scale Mg alloy components with high manufacturing flexibility. In this study, the evolution of the solidification microstructure of a WAAM-processed Mg-Al-based alloy was quantitatively analyzed based on the analytical models; then, the correlations between the solidification microstructure and mechanical properties/damping capacities were investigated. The results revealed that the WAAM-processed Mg-Al-based alloy with an equiaxed-grain-dominated microstructure displayed a simultaneous enhancement in mechanical properties and damping capacities compared to those of the cast Mg-Al-based alloy. The good combination of mechanical properties and damping capacities are mainly attributed to the weakened basal texture with a relatively high Schmid factor for basal <a> slip, the twinning-induced plasticity (TWIP) effect associated with the profuse {10-12} tensile twinning, and the relatively high dislocation density caused by the thermal stress during the WAAM process.

Investigation of Impact Performance of STF Impragnated Composites

It is important to achieve high strength, high modulus of elasticity, good energy damping for lightweight armor materials. For this purpose, two or more similar or different materials are combined at the macro level. In this way, a new structure emerges that we call composite material. A composite is a new structure in which the good properties of the components in its structure become evident in the material. Research on the production and mechanical properties of composites that meet the needs of the developing technology continues. Military personnel, armored vehicles and many security elements are tested in the field with a lot of threats (such as mines, armor piercing ammunition, explosives etc.). Therefore, the armor used by security elements should be strengthened without compromising features such as lightness, cost and long-term use. This study covers the development of Kevlar's ballistic properties by impregnating Shear Thickening Fluid (STF). STF is composed of silica (AEROSIL 200) and polyethylene glycol (PEG 400). STF-impregnated Kevlar fibers have been subjected to impact testing at low and high speeds. Low-speed tests were carried out with a drop tower. High-speed tests were carried out according to NIJ 0101.06 Level II standards. The mass fraction of silica in the STF was determined as the research parameter. The change in the behavior of the materials with the change of silica ratio was investigated; Although improvements were observed in energy dissipation in low-speed impacts, it was noted that ballistic behavior improved up to a certain point, and then the improvement in behavior decreased.

Design of novel two-dimensional single-phase chiral phononic crystal assembly structures and study of bandgap mechanism

In this paper, novel two-dimensional single-phase three-ligament, four-ligament and six-ligament chiral structure models are proposed. The advantage is that it is easy to manufacture with few components, has good sound insulation and vibration damping performance, and is more practical. The dispersion information of the structure is calculated by combining Bloch's theorem and the finite element method. By varying the geometric parameters of the new structural single-cell and simulating the vibration transmission of the finite period structure to check the vibration suppression capability of the optimized structure. Three combined structures were constructed to compare their energy band properties with the base structure. The wave propagation characteristics within the combined structure are also analyzed by comprehensive means. It is shown that the optimized structure has a significantly lower bandgap down to below 1 kHz and a significantly wider bandgap width up to 3.6 kHz. The combined structure can open up a wider omnidirectional bandgap for multi-frequency and broadband vibration attenuation. The flexibility of the structure combination gives it a large potential for use, providing a new solution for broadband and multi-frequency vibration and noise reduction, while plane wave analysis provides theoretical support for structural optimization.

Green self -vulcanizable rubbers with recyclable, self-healable capabilities and excellent damping performance

The vulcanization of rubbers is a prerequisite for their practicality. Currently adopted vulcanization methods for rubbers are suffering from some persistent problems, such as the utilization of harmful vulcanizing additives, the generating of volatile organic compounds, and the difficulties in the recycling of end-of-life rubbers. To meet the need of sustainable development, a facile and green self-vulcanization method is used to prepare self-healable and recyclable damping rubbers. Hydrogenated carboxylated nitrile rubber (HXNBR) and epoxidized nature rubber (ENR) can efficiently self-vulcanize by forming β-hydroxyl ester crosslinks without adding vulcanizing agent. Zinc oxide and epoxidized soybean oil are added as additives to adjust the self-vulcanization of HXNBR/ENR compound. Phenolic resin can make HXNBR/ENR composite to become a good damping material, and significantly improve the self-healing capacity of the composite. Additionally, the end-of-life self-vulcanized HXNBR/ENR composites can be recycled and reprocessed by selectively cleaving the ester bonds in the crosslinked structure, resulting in a very high recovery of mechanical performance of the recycled composites, which proves that this is a facile and efficient rubber recycling method.

High strength, recyclable and shape memory polyhydroxyurethanes with intrinsic fluorescent properties

AbstractPolyhydroxyurethanes (PHUs), which are synthesized through the aminolysis of cyclic carbonates, avoid the use of toxic isocyanates compared with traditional polyurethanes (PUs) and have aroused great interest. The large number of hydroxyl groups in the network endows PHUs with unique features, such as recyclable properties and fluorescent properties. To establish the high performance and multifunctionality of PHUs, we designed a molecular structure to fabricate PHUs with mechanical robustness, shape memory properties, fluorescent properties, and recyclable properties. The yielded PHU crosslinked by the quaternary thiol and weak but dense hydrogen bonds (H‐bonds) shows unprecedented high mechanical properties with a tensile Young's modulus of 3.13 GPa, comparable to that of polyimide, a tensile strength of 59.2 MPa at room temperature and an excellent toughness of 27.9 MJ/m3 at 50°C, and good damping properties (tanδ ≥ 0.3, temperature range of 35.2°C). Interestingly, fluorescence caused by the aggregation of carbamate within PHUs allows it to be applied for damage self‐reporting to visualize tiny cracks or magnify fractures. Furthermore, both the thermosetting PHUs and recycled thermosetting PHUs presented excellent shape memory performance. This study provides certain inspiration for the design and development of highly rigid multifunctional polymers.

Dynamic Energy Dissipation Performance of Nonlinear Large-Deformation Viscoelastic Joint Damper under Strong Dynamic Load

Large-displacement corner deformation often occurs at the joints of towering structures and long-span space structures subjected to strong earthquake. In order to improve the energy dissipation capacity of structural joints, the Nitrile Butadiene Rubber/High Abrasion Furnace Black (NBR/HAF) high damping composite was fabricated by formulation optimization in this paper, where a nonlinear large-deformation viscoelastic joint damper was proposed. The damper consists of five layers of restrained steel plates and four layers of shear energy dissipating material, which can reach 60[Formula: see text]mm shear displacement. In this paper, dynamic mechanical performance tests and static mechanical tests were firstly conducted on the core energy dissipating media of the damper. The loss factor of NBR/HAF composite reached a peak of 1.51 at about 8.2°C, while its wide damping temperature range was 27°C. Second, the accuracy of the simulation method was verified by comparing the simulated and experimental hysteresis curves. Then, the refined numerical simulation of this damper was carried out using ABAQUS finite element software with the high damping material as its core energy dissipating media. Finally, the magnitude and type of energy dissipation of each part of the viscoelastic joint damper under different loads were investigated. It was found that the large-deformation viscoelastic joint damper based on the composite had good damping capacity. Its dynamic characteristics were affected by the displacement amplitude and excitation frequency, which exhibited hardening nonlinear characteristics. As the frequency and load amplitude increased, the peak displacement in the loading direction gradually decreased, whereas the total energy input to the damper and the energy dissipated by the viscoelastic material increased monotonically. The input energy was only dissipated by the viscoelastic material, and no plastic loss occurred in the steel plate during the entire loading stage. Under high frequency and large loads, the damper can also have good energy dissipation characteristics. Because of the negative strain energy caused by plastic dilatancy, the energy dissipated by the material was gradually greater than the input energy with the load increasing.

Energy research of three-adjacent structures connected by Kelvin-type dampers based on power flow

The control effect of a three-adjacent structural system connected by Kelvin-type dampers and its energy transfer and distribution under uncertain and deterministic excitations are investigated in this study. A simplified model of multi-degree-of-freedom mechanics is used for establishing structural equations; the power flow equations of this structural system are derived based on the power flow theory. The influence law of a structural parameter changes on the input power flow when the damper that is not connected is investigated; the damper parameters are optimized using the NSGA-II (Non-dominated Sorting Genetic Algorithm-Ⅱ) algorithm after connecting the dampers, and the damping control effect is evaluated. Next, the variation law of the input power flow of the structure and damper is analyzed with the structure and damper parameters as study variables. These results indicate that an increase in structural stiffness has a positive excitation effect on the seismic performance improvement of the structure; the influence of the structural damping ratio on the input power flow is sufficiently small. The influence of change in damper parameters on the input power flow is closely related to the structural parameter setting. The three-adjacent damping structure system connected to optimal parameter dampers exhibits a good damping performance when the structural parameters are determined.

High vinyl polybutadiene rubber/polypropylene thermoplastic elastomer blends: Optimization of internal mixing process parameters and screening of processing methods

AbstractThermoplastic vulcanizates (TPV) composed of high vinyl polybutadiene rubber (HVPB) and polypropylene (PP) have good thermal stability and damping properties. This work aims to apply a design of experiments (Taguchi L9 orthogonal array) to optimize the mixing parameters (rotor speed, temperature, and time) for the HVPB/PP TPV. The effects of these mixing parameters on its physical and mechanical properties of HVPB/PP TPV follow the order: rotor speed &gt; temperature and time. In the case of the master batch process, the optimum mixing parameters are 60 rpm, 180°C and 8 min. Subsequently, four processes (master batch, static vulcanization, rubber‐plastic premixing, and two‐step processing) are compared using the same optimum mixing parameters. The master batch process turns out to be the best in terms of physical and mechanical properties.

Analytical Model of Structural Damping in Friction Module of Shell Shock Absorber Connected to Spring

Vibration processes play a significant role in the modern industry. In most cases, vibration reduces strength, reliability, and durability of industrial machines, mechanisms, and structures, as well as adversely affects the health of support staff. This study presents a new dry friction shell shock absorber design. The shock absorber contains two spring sections and a friction module with an open shell and an elastic filler; at the same time, the spring sections and the friction module work in parallel. The proposed device demonstrates good damping characteristics, capable of operating under high operating loads, and at the same time has compact transverse dimensions. With a nonmonotonic loading of such a shock absorber, due to the contact interaction of the filler with an open shell, part of the energy that is supplied to the system will be dissipated. In other words, in response to the action of an external nonmonotonic loading, the phenomenon of structural hysteresis occurs in the friction module of the shock absorber. To describe the deformation of the shock absorber, a mechanical and mathematical model of a shell with a cut along the generatrix, which is the main bearing link, has been developed. By means of the technique of quasistatic analysis of structural damping in nonmobile nonconservative shell systems with a deformable filler, the hysteresis loops of the presented shock absorber are analytically described. Using them, according to the known loading history, it is possible to predict the behavior of the considered nonconservative system at any time after the start of the loading process. At each stage of the cyclic loading, the distribution of stresses and relationships between the external loading and the piston displacement was studied. Inequalities are obtained for permissible loads under which the operation of the shock absorber is safe. Such shell shock absorbers are projected to be used in the mining, oil and gas, and construction industries.

Numerical simulation of an entangled wire-silicone rubber continuous interpenetration structure based on domain meshing superposition method

The entangled metal wire/silicone rubber continuous interpenetrated phase composite (EMW-SRC) is a high-performance damping material with silicone rubber as matrix and metal wire turns as the reinforcement skeleton. EMW-SRC has good damping characteristics and significant load-bearing stiffness. This work first characterizes the fine interface morphology and macroscopic mechanical characteristics of the EMW-SRC and adopts a computer-aided preparation technology to accurately reconstruct the complex structure of the spatially random distribution of the entangled metal wire material. It develops a finite element model of the EMW-SRC with high-quality structured mesh based on the domain mesh superposition method cohesive cells to share and embed the surface nodes at the interface. Moreover, the composite interface bonding performance between metal wire and silicone rubber is investigated, the interfacial bonding parameters are determined, and the reliability of the mesh model is assessed by comparing the results of a single wire pull-out test and simulation analysis. Based on this, quasi-static compression test and simulation of the material are further performed, with the simulation results matching well with the experimental ones. The mesoscale simulation results show that the metal wire inside the EMW-SRC can overcome the silicone rubber restriction on micro-slip during the load-bearing process. The metal wire micro-element is subjected to torsional load. Under a compression displacement of 0.7 mm, the composite interface bonding remains intact without damage. In conclusion, the developed model can provide a prior guidance on the preparation and use conditions of the proposed material and offers an effective way to investigate the fine-mechanics of such materials with high damping and high load-bearing characteristics.

Design and Parameter Optimization of the Reduction-Isolation Control System for Building Structures Based on Negative Stiffness

In order to improve the damping capacity of building isolation system, this paper studies the damping isolation control system of the building structure based on negative stiffness. In this paper, the dynamic equation of the damping isolation control system is derived and its parameters are optimized by H2 norm theory and Monte Carlo pattern search method. Taking the 5-story building structure as an example, this paper analyzes and evaluates the damping performance of the damping isolation control system of the building structure under the actual earthquake. The results show that negative stiffness can improve the damping capacity of traditional isolation system. Additionally, the negative stiffness ratio under the condition of stability, the smaller the negative stiffness ratio, the stronger the vibration reduction ability of the negative stiffness. The damping isolation control system of building structure based on negative stiffness shows good damping effect under the actual earthquake.

Improved Data-Driven Model-Free Adaptive Damping Controller Design for Interconnected Power Systems With Stochastic Communication Delays

The original model-based wide-area damping control (WADC) is difficult to obtain good damping performance due to the complex structure of interconnected power systems. In this paper, an improved data-driven model-free adaptive control (ID-MFAC) algorithm is proposed to design WADC for interconnected power systems with stochastic communication delays. First, the multiple-input multiple-output power system can be decoupled as multiple single-input single-output subsystems by considering controller interactions and system disturbances. Second, a step-size vector is designed to adjust the pseudo-partial derivative and make the algorithm more flexible by considering both input and output data adequately. Furthermore, an adaptive delay compensator is designed to compensate stochastic communication delays. Last, simulations are conducted to verify that the ID-MFAC algorithm can efficiently suppress multiple inter-area oscillations modes under various stochastic communication delays.

Grain boundary plasticity at intermediate temperatures in fine-grained Mg-Mn ternary alloys

The effect of micro-alloying with different elements (X) on grain boundary sliding behavior at intermediate temperatures (up to 473 K) is examined by two types of testing methods, i.e., damping and tensile tests, using fine-grained Mg-0.3 at%Mn-0.1 at%X alloys. The micro-alloying of X was selected to be Al, Li, Sn, Y and Zn, with focusing on common elements. In the damping tests, the micro-alloying element affects the damping capacity. Mg-Mn-Al, Mg-Mn-Li and Mg-Mn-Sn alloys have a high value of tanδ not only at room temperature but also at intermediate temperatures; however, the Mg-Mn-Y alloy does not indicate such a characteristic. It is interesting to notice that the tensile response to the micro-alloying elements shows a similar trend to that obtained in the damping tests. This resulted from the different magnitude of grain boundary sliding contribution to deformation. Observations of tensile deformed surface features indicates a partial contribution, approximately 30%, of this deformation mechanism in the alloys having good damping capacity and ductility. This is the major reason that experimental results clearly deviate from the values calculated by constitutive equation for general superplastic alloys. Nevertheless, the unique grain boundary sliding that occurs at intermediate temperatures is well consistent with previously reported results for tensile tests on fine-grained Mg and its alloys conducted at ambient temperature.