Excellent Damping Research Articles

Role of amines in microstructure tuning for synergistic damping and mechanical properties in epoxy resins

A novel epoxy(ER)/(imidazole)MI/caproamine(CA)interpenetrating polymer networks (IPNs) having varying degree of micro phase separation was prepared. The FTIR results demonstrated that there were two main reactions occurring in the curing process of the CA/ER/MI system. The DSC thermograms of the CA/ER/MI exhibited cure regime in the temperature range of 100–130 °C, Ea was obtained from Kissinger method and the toughened epoxy systems fitted well into a first order linear relation with the average apparent activation energy of 50.5 kJ/mol for m-CA/ER/MI and 63 kJ/mol for s-CA/ER/MI system. The cure index of m- CA/ER/MI was found to obey the condition for good cure, whereas the s-CA/ER/MI system showed poor cure index at lower heating rate and at higher heating rate the system transformed into an excellent cure index. It was interesting to notice that the concentration of CA played a vital role in tuning the microstructure of the overall CA/ER/MI system exhibiting nanoscopic phase separation when CA> 20 wt% with higher percentage of phase separation phenomenon. The 30 wt% m-CA/ER/MI system and 40 wt% s-CA/ER/MI system exhibited excellent damping value of 1.02 and 1 respectively. The tensile strength and the respective elongation at break of 40 wt% m-CA/ER/MI and 30 wt%s-CA/ERMI are 31.25 MPa with14.4 % elongation at break and 27.8 MPa with 30.57 % elongation at break respectively thereby suggesting the potential applications in the field of vibration damping to meet the demands of high performance engineering materials.

Dynamic response analysis of story-adding structure with isolation technique subjected to near-fault pulse-like ground motions

The isolation technique is widely studied and applied in structural engineering due to its excellent seismic performance. However, the existing research mostly focuses on the conventional structure under the action of regular ground motions. In this paper, a story-adding seismic structure, a base-isolated structure, and a story-adding isolated structure were simulated by using numerical simulation methods. The dynamic response characteristics of the three structures under near-fault pulse-like ground motions are analysed and compared with the far-fault ground motions. The results showed that using the base isolation can significantly extend the period of the main structure and reduce the seismic response on the upper structure. The inter-story drift ratio, inter-story shear force, and the story acceleration of all three structures under near-field pulse-like ground motions were all larger than that of far-field earthquakes. Both base-isolated structure and story-adding isolated structure showed excellent damping performance. Besides, the damping properties of the base-isolated structure are better than the story-adding isolated structure.

Simple preparation method of asphalt polyurethane foam for various insulating purposes

In this study, Asphalt PUF (asphalt polyurethane foam) was simply prepared from the point of view of industry by in-situ polymerization of a polyoxyalkylene polyol (caster oil) and an organic isocyanate 4,4′diphenyl methane diisocyanate (MDI) into asphalt emulsion media at different NCO/OH index starting from (0.8 to 1.6). The chemical reaction is confirmed by FTIR. Surface morphology is scanned with SEM. Some of selected physical tests were performed for different insulating purposes; such as sound absorption, vibration damping, thermal conductivity, thermal cycling and water absorptivity%. The results approved that the prepared foams have an excellent sound and vibration damping properties. Furthermore, they can easily fit the uneven surface because of their good shape retention. Hence, it seems to be suitable especially for engine compartment as sound and vibration insulator. In addition, the water resistance properties of these foams are important for applications requiring long-term exposure to water, such as sealant, coating and membranes for landfills, tanks and pipes.

Unified Smith predictor‐based loop‐shaping H ∞ damping controller for mitigating inter‐area oscillations in power system

Low-frequency inter-area oscillation is one of the major problems to transfer the bulk power from one area to another area in an interconnected large power system. A wide-area signal-based controller is more effective to improve the damping of the inter-area oscillation than a local area signal-based controller. A wide-area measurement system makes it easier to transmit the wide-area signal through the communication system from the remote location to the controller site. However, the involvement of the unavoidable time delay in the wide-area signal transmission from a remote area to a controller site is to possess a great deal of challenge to design a damping controller. In this study, a unified Smith predictor (USP)-based loop shaping controller is designed to handle the negative effect of the delay using the wide-area signal. The robust stabilization normalised co-prime factor problem is converted into a generalised H ∞ optimisation problem for additional pole placement constraints. The performances of the USP-based loop-shaping H ∞ controller are compared with the USP-based H ∞ controller. From the obtained results, it is verified that the proposed controller gives an excellent damping performance and handles the effect of time delay.

Damping characteristics of integral squeeze film dampers on vibration of deep groove ball bearing with localized defects

Purpose This work aims to demonstrate the vibration suppression of the rotor system with localized defects on bearing using an integral squeeze film damper (ISFD). Design/methodology/approach Experiments were carried out to study the vibration characteristics of the rotor system with ISFD mounted on fault deep groove ball bearings. Three fault bearings including bearing with outer race defect, inner race defect and ball defect have been used in this paper. The results were compared by use of vibration acceleration level, continuous wavelet transform and envelope spectrum. Findings It was found that ISFD shows excellent damping and vibration attenuation characteristics of the rotor system with defective bearing. The fault bearing rotor system with external ISFD considerably reduces the vibration energy and amplitude compared with the system without ISFD. Originality/value There is a dearth of experimental research pertaining to vibration characteristics of rotor system support by defective bearings with ISFD. Besides, the test provides evidence for the application of ISFD in vibration control of the rotor system with incipient defects on bearing. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2020-0144/

Tailoring the damping and mechanical properties of porous NiTi by a phase leaching process

A porous B2-NiTi compound with fine pore size and homogeneous pore distribution has been successfully fabricated by a novel phase leaching top-down process. In this process, NiTi-NiGd duplex pre-alloys were firstly prepared. Then NiGd phase was etched out in nitric acid solution, leaving NiTi to form pore structures. The pore size could be refined by increasing the cooling rate of the pre-alloys. The porosity could be tailored by changing the volume fraction of NiGd, which was related to the compositions of pre-alloys. The pore size can be refined to ∼0.27 μm in the sample with a porosity of 29%. This sample shows the highest damping capacity (0.08 at ambient temperature) and Young’s modulus (6.2 GPa). These excellent damping and mechanical properties should be attributed to the enlargement of stress-strain localization areas of the refined pore structure. However, increasing the porosity to a further extent results in a larger pore size and degrades the damping property. The present homogeneous and fine porous NiTi is considered to be good candidates as damping materials in engineering application.

Dynamic response optimization of structures with viscoelastic material using the equivalent static loads method

Viscoelastic material is widely used in automotive structures due to its outstanding vibration-damping characteristics with appropriate stiffness. Viscoelastic material, which has viscosity and elasticity, shows energy absorption and dissipation. The material properties of viscoelastic material are dependent upon time, temperature, and loading path. Hence, these characteristics have to be considered when performing structural optimization. Studies on the constitutive equations of viscoelastic material are widely carried out, and structural optimization using harmonic excitation in the frequency-domain is often reported. However, structural optimization in the time-domain is rarely performed. One of the reasons is that the cost of sensitivity analysis is quite expensive. The Equivalent Static Loads Method (ESLM) is a linear/nonlinear dynamic response structural optimization method. In this research, a practical structural optimization method to consider the characteristics of viscoelastic material is proposed using ESLM. Equivalent static loads (ESLs) are defined as the static loads that generate the same displacement field as that from dynamic analysis. In ESLM, dynamic analysis and linear static response optimization are alternatively repeated until convergence is achieved. Viscoelastic material reduces the vibration amplitude and the stored energy in a structural system. Thus, excellent damping performance is required for a part with viscoelastic material, while the proper stiffness is maintained. An appropriate design formulation is made for the design of viscoelastic material. In this research, the sum of damping ratios, the sum of weighted damping ratios, and the sum of squared displacements are considered as the objective functions. These three objective functions deal with the peak displacements of damped vibration. Three case studies are defined by optimizations of some typical automotive parts with viscoelastic material. They are a sandwich panel, a rubber bushing, and a seat cushion. The damping performances of the objective functions are compared and discussed.

The Effect of OMMT on the Properties of Vehicle Damping Carbon Black-Natural Rubber Composites.

In this study, the filled natural rubber (NR) was prepared with organic montmorillonite (OMMT) and carbon black (CB). The effects of the amount of OMMT on the properties of CB/NR composites were investigated by measuring the physical and mechanical properties, compression set and compression heat properties, processing properties and damping properties. The formulation was optimized depending on the different conditions of end applications and the damping properties of rubber were maximized without affecting the other properties of the rubber. The results showed that the rubber composite system filled with 2 phr (parts per hundreds of rubber) OMMT had better mechanical properties and excellent damping performance.

Analysis and design of a novel and compact X-structured vibration isolation mount (X-Mount) with wider quasi-zero-stiffness range

Passive vibration isolation is always preferable in most engineering practices. To this aim, a novel, compact and passive vibration isolation mount is studied in this paper, which is designed by using the X-shaped structure with a much smaller size. The novel mount is adjustable to different payloads due to a special oblique and tunable spring mechanism, and of high vibration isolation performance with a wider quasi-zero-stiffness range due to the deliberate employment of negative stiffness of the X-shaped structure. The X-shaped structure has been well studied recently due to its excellent nonlinear stiffness and damping properties. In this study, it is for the first time to explore the utilization of the negative stiffness property within the X-shaped structure such that the resulting design, the X-structured mount (X-mount), can have an obviously larger vibration displacement range which maintains the quasi-zero-stiffness property. A special oblique spring is thus introduced such that the overall equivalent stiffness of the X-mount can be much easily adjusted according to different payloads. Systematic parametric study is conducted to reveal the critical design parameters and their relationship with vibration isolation performance. A prototype and experimental validations are implemented to validate the theoretical results. It is believed that the X-mount would provide an innovative technical upgrade to many existing vibration isolation mounts in various engineering practices and it could also be the first prototyped mount which can offer adjustable quasi-zero stiffness and adjustable loading capacity conveniently.

Energy Dissipation Characteristics and Parameter Identification of Symmetrically Coated Damping Structure of Pipelines under Different Temperature Environment

In this paper, a symmetrically coated damping structure for entangled metallic wire materials (EMWM) of pipelines was designed to reduce the vibration of high temperature (300 °C) pipeline. A series of energy dissipation tests were carried out on the symmetrically coated damping structure at 20–300 °C. Based on the energy dissipation test results, the hysteresis loop was drawn. The effects of temperature, vibration amplitude, frequency, and density of EMWM on the energy dissipation characteristics of coated damping structures were investigated. A nonlinear energy dissipation model of the symmetrically coated damping structure with temperature parameters was established through the accurate decomposition of the hysteresis loop. The parameters of the nonlinear model were identified by the least square method. The energy dissipation test results show that the symmetrically coated damping structure for EMWM of pipelines had excellent and stable damping properties, and the established model could well describe the changing law of the restoring force and displacement of the symmetrically coated damping structure with amplitude, frequency, density, and ambient temperature. It is possible to reduce the vibration of pipelines in a wider temperature range by replacing different metal wires.

Influence of core and matrix modifications on the mechanical characteristics of sandwich composites

Sandwich composites are increasingly being used for a variety of applications owing to excellent properties like high bending strength and stiffness, low strength-to-weight ratio and excellent damping and acoustic properties. However, there are certain issues faced while using sandwich structures for structural applications which includes debonding of face sheets from core, matrix cracking and core shear failure. In the current work, an effort is made to enhance the mechanical characteristics of sandwich composites by altering poly vinyl chloride (PVC) foam core and adding multi-walled carbon nanotubes (MWCNT) to epoxy resin used as the matrix. Four different configurations of sandwich laminates were fabricated using vacuum bagging process: (1) plain core and neat epoxy resin (2) core with blind holes and neat epoxy resin (3) core with blind holes and epoxy resin with MWCNT (4) core with through holes and epoxy resin with MWCNT. Flexural and compression tests were carried out on these sandwich specimens according to American Society for Testing Materials (ASTM) standards. Sandwich specimens with through holes in the core and resin mixed with MWCNT exhibited better mechanical characteristics compared to the other sandwich laminates. Type 4 sandwich specimens were able to withstand 12% and 16% more flexural and compressive loads respectively compared to conventional sandwich specimens.

Development of tuned particle impact damper for reduction of transient railway vibrations

Herein, a tuned particle impact damper to reduce rail rolling noise is proposed, and its vibration reduction capability is investigated experimentally. The proposed damper was designed for easy attachment to a rail and possessed the combined characteristics of a tuned dynamic absorber and an impact damper. The vibration behaviour of the damper-attached rail was investigated using an actual UIC60 rail specimen. The measured vibration reduction performance was verified by simulation of the collision behaviours. The proposed damper exhibited excellent vibration reduction capability at a specific frequency band with additional damping in the broadband frequency range owing to partially inelastic particle impacts. A modal analysis of the tuned particle impact damper illustrated the mechanism of vibration reduction via the modal response of the proposed damper on the rail specimen. The interaction of the rail transverse vibration with the attached damper was analysed. The vibration reduction performances were investigated based on the damping coefficient predicted from both the least-squares and Prony’s methods. The damping capability was identified to investigate the effects of excitation force, coefficient of restitution, mass ratio, clearance, and clamping force. Based on applying impact damping on railway tracks, the proposed tuned particle impact damper showed excellent damping capability in reducing transient vibrations, which is essential for minimising rolling noise from passing trains.

Development of a novel Mg–Y–Zn–Al–Li alloy with high elastic modulus and damping capacity

The novel cast Mg-1.3Y-0.8Zn-6.4Al-16.7Li (at. %) alloy showed excellent comprehensive properties including high elastic modulus of 52.9 GPa, ultra-high specific modulus (E/ρ) of 33.1 GPa cm3/g and superior damping capacity. The high elastic modulus was attributed to Li in solid solute and the formation of high modulus Al–Li compounds and Al2Y particles, and the simultaneous decrease in density due to Li addition results in the ultra-high specific modulus. At room temperature, the excellent damping capacity in the alloy was due to the presence of a large number of movable parallel dislocations. Moreover, the alloy could be classified as the high damping metal (Q−1>0.01) in the strain amplitude region. With the increasing temperature, the superior damping capacity of the alloy could be explained by dislocations movement and grain boundary gliding.

Performance Analysis of a Novel Magnetorheological Damper with Displacement Self-Sensing and Energy Harvesting Capability

External sensors are vulnerable to the external magnetic field, temperature, noise, and other factors in the semi-active control system based on magnetorheological (MR) damper, which not only reduces the reliability and stability but also increases the complexity, installation space, and system cost. Meanwhile, mechanical energy is generally dissipated as heat due to the friction between the cylinder and damper piston of the MR damper. To further broaden the applications of MR damper, it is essential to maintain excellent functions when the power supply is cut off in various emergencies. Based on this, a novel MR damper with displacement self-sensing and energy harvesting capability is proposed to solve the problems such as large structural size, high system cost, and vibration energy dissipation. Firstly, the structures of the MR damping, displacement self-sensing, and vibration energy harvesting are designed and integrated into the proposed MR damper. Then, the distribution of the magnetic flux density, displacement self-sensing voltage, and energy harvesting efficiency with a single induction coil and double induction coil is obtained using the finite element method. The experimental test system is set up and the performance of MR damping, displacement self-sensing voltage, and energy harvesting efficiency is experimentally tested. The experimental results show that the damping force reaches 513 N at the applied current of 0.25 A. At the same time, the amplitude of self-sensing voltage increases linearly with the increase of the amplitude of sinusoidal displacement excitation, and the displacement sensitivity comes up to 54.37 mV/mm. Moreover, the self-sensing voltage of the vibration energy harvesting component with a double induction coil is 2.512 V, and the energy harvesting efficiency is about twice than that with a single induction coil. It is found that the proposed MR damper, with a relatively compact structure and lower cost compared with traditional MR damper, not only promisingly achieves excellent dynamic damping performance but also simultaneously possesses displacement self-sensing ability and energy harvesting capability.

Energy-Dissipating Polymeric Silicone Surfactants.

Materials that are able to withstand impact loadings by dissipating energy are crucial for a broad range of different applications, including personal protective applications. Shear-thickening fluids (STFs) are often used for this purpose, but their preparation is still limited, in part, to high production costs. It is demonstrated that polymeric surfactants comprised of linear telechelic sugar-modified silicones-with neither additives nor particles-generate transient polymer networks (TPNs) that represent a promising alternative to STFs. The reported polymers have distinct viscoelastic properties and can turn from a liquid into a rubbery network when force is applied. Saccharide-modified silicones with short chains (degree of polymerization (DP) ≈ 34, 68) are solids, but become energy-absorbing viscoelastic fluids when diluted in low-viscosity silicone oils; longer silicones (DP ≈ 338, 675) with low saccharide contents are viscoelastic fluids at room temperature. Excellent damping properties are found for the reported silicone surfactants, even those containing only 0.1% saccharides. The degree of energy absorption can be tailored simply by controlling the sugar/silicone ratio.

Damping vibration analysis of a dual-axis precision force sensor based on passive eddy current

High precision force sensors usually include flexible structures, which are prone to cause unnecessary mechanical vibrations, due to their low stiffness and high sensitivity. Aimed at the adverse problem, this paper proposes a novel two-degree-of-freedom passive damping system dedicated to the vibration suppression of a dual-axis precision force sensor. The damping system consists of two identical eddy current dampers (ECDs), each of which utilizes a double-layer Halbach-array permanent magnet structure and a middle-layer copper plate to generate a large damping force. Analytical models are established to predict the damping characteristic and dynamic behavior of the sensor system, with further verification through finite element simulation. Experiments are implemented to demonstrate the effectiveness of the damping design to suppress the sensor vibration in comparison with three different configurations (without ECD, with a single ECD, and dual ECDs). The results indicate the excellent damping characteristics of the developed ECD. This feature can be also extended to the vibration suppression of the planar XY positioning stages.

Experimental and Theoretical Study of High-Energy Dissipation-Viscoelastic Dampers Based on Acrylate-Rubber Matrix

Acrylate rubber molecules contain sterically hindered and highly polar ester groups, which can generate a large amount of internal friction energy under external alternating stress and exhibit high internal friction for energy dissipation. Based on previous studies on the formulation of acrylate viscoelastic materials, the optimal formulation was prepared and made into acrylate viscoelastic dampers and the mechanical properties of the corresponding damper specimens were tested. The acrylate viscoelastic dampers at different ambient temperatures, excitation frequencies, and displacement amplitudes were systematically investigated. The experimental results indicate an excellent damping capacity of the acrylate viscoelastic dampers, where the dynamic properties are affected by the ambient temperature and excitation frequency, and the single-loop energy dissipation capacity is significantly affected by the displacement amplitude. To accurately represent the effects of the temperature, frequency, and amplitude on the dynamic properties of the damper, a modified fractional-derivative equivalent model is introduced, where the internal variable theory and temperature-frequency equivalent principle are introduced to reflect the amplitude effect and temperature effect, respectively. Finally, the results calculated by the proposed model were compared with the experimental data, which verified the correctness of the mathematical model.

Significant impact of cold-rolling deformation and annealing on damping capacity of Fe–Mn–Cr alloy

The influences of cold-rolling deformation and annealing on the damping capacity of Fe–19Mn–8Cr alloy were investigated. It was observed that the cold-rolled Fe–19Mn–8Cr alloy with a reduction of 10% showed the relatively excellent damping capacity because of the relatively more e-martensite and lower dislocation density, and the reduction of slopes of different damping curves increased along with increasing the cold-rolling reduction. Besides, the subsequent annealing process can further enhance the damping capacity. After 70% cold-rolling deformation, the austenite grain would grow up with the increase in the annealing temperature, which resulted in a significant change in the content and morphology of e-martensite influencing the damping capacity of the experimental steel. The damping capacity was optimum when annealed at 800 °C for 30 min, displaying that the size of e-martensite has a vital influence on the damping capacity of the experimental alloy. This study may enrich the fundamental knowledge about how to ameliorate the damping capacity of Fe–Mn–Cr damping steels.

Ultrahigh damping capacity achieved by modulating R phase in Ti49.2Ni50.8 shape memory alloy wires

An ultrahigh damping capacity with internal friction close to 0.35 was detected over a large temperature range of 75 °C (from -40 to 35 °C) in Ti49.2Ni50.8 shape memory wires by adjusting the B2→R phase transformation through a low-temperature aging treatment. Microstructural analysis showed that the excellent damping performance is attributed to high-density nanodomains in the R phase, which are induced by short-range Ni segregation. These results are expected to further expand capacity for designing damping microstructure.

Bio-based self-healing Eucommia ulmoides ester elastomer with damping and oil resistance

Eucommia ulmoides gum (EUG) is an essential bio-based material with a similar chemical structure to natural rubber, but it is rigid plastic at room temperature due to crystallization, which limits its wide application. Herein, we report a new method for synthesis of functional Eucommia ulmoides ester (EUET) elastomer by chemical modification of EUG. First, EUG was epoxidized by performic acid formed from hydrogen peroxide and formic acid in situ in toluene solution and then subjected to ring-opening reaction with acetic acid. It was found that EUET contained both α-hydroxyl ester and β-hydroxyl ester in the molecular chain. Unlike EUG, EUET was no longer crystallized due to the reduction of regularity, and it has been successfully converted into elastomer, which was confirmed by the elastic strain recovery experiment. Furthermore, because of the presence of polar groups and the hydrogen bond between them, EUET could self-heal under the condition of 50 °C, and their vulcanizates possessed excellent mechanical properties, resilience, oil resistance and damping properties. This study may promote the application of EUG in the field of bio-based functional elastomers.