Damping Capacity Research Articles

Investigating the Performance of Data-Driven Ensemble Machine Learning Models in Preliminary Designing Multi-Stage Friction Pendulum Bearings

Over the last few decades, the field of base isolation systems has demonstrated enormous advancements through the innovation of novel systems, and there has been an enhancement in the performance of structures equipped with isolation under conditions of moderate and severe seismic activity. One of the most important systems is the multi-stage friction pendulum, which offers a spectrum of effective pendulums across different regimes, thereby achieving enhanced capability for energy dissipation. The difficulty in designing these bearings at the preliminary stage comes from the fairly long process of trials and errors in selecting the properties of each sliding surface so that the required effective period, effective damping, and displacement capacities are achieved. This study investigates the performance of various data-driven ensemble machine learning models in directly designing multi-stage friction pendulum bearings. Within the context of the analysis, the most recent generation of friction pendulum that has been introduced to the literature, the quintuple friction pendulum, is used as the investigation employs a case to assess the dependability of the design strategy and the efficacy of a multi-output machine learning techniques. In general, the findings of this study have shown that machine learning models provide an accurate way to directly design quintuple friction pendulum isolators and attain the necessary properties of the isolators. The practicality of this research lies in highlighting how machine learning can be applied to considerably expedite the design and optimization of multi-stage friction pendulum bearings and in defining the most suitable machine learning technique to adopt in such tasks.

Multiple lubricated joints with long and short bearings in multibody mechanical systems - Modeling, simulation, and performance analysis

This study examines the effect of multiple lubricated imperfect long and short bearings on the performance of a multibody mechanical system. Unlike the typical assumption of a single perfect or imperfect lubricated joint due to modeling difficulties, this research considers the practical impacts of clearances in multiple joints. While unlubricated joints generally cause significant performance issues, lubricants reduce these effects, creating more localized peaks. The findings show that as the number of lubricated joints increases, both the magnitude and frequency of these peaks rise. In systems with multiple journal bearings, torque peaks become more noticeable due to the additional degrees of freedom introduced by the clearances. These degrees of freedom amplify acceleration, leading to higher lubricant reaction forces, which in turn require greater motor torque peaks to maintain the system's kinematics. Shorter lubricated joints exhibit more severe peaks than longer ones, mainly due to side leakage causing axial pressure variation and reduced damping capacity. The study highlights the need to replace idealized joints with imperfect ones for more accurate modeling of practical systems.

3D printing of biomimetic liquid crystal elastomers with enhanced energy absorption capacities

Spider dragline silks are noted for their unmatched toughness, which arises from their unique primary structure. However, the underlying mechanisms of this toughness have seldom been verified using synthetic structural materials. Liquid crystal elastomers (LCEs) are polymer networks with mechanical properties bearing high resemblances to those of spider silks, and are ideal material for mimicking the primary structure of spider silk and revealing its toughing mechanisms. This study introduces a LCEs-based energy absorption structure that mimics the primary structure of spider dragline silks via 3D printing method. This LCEs-based biomimetic structure offers superior toughness and energy absorption capabilities with a damping capacity of 90%, significantly surpassing that of both artificial and biological viscoelastic materials. We successfully demonstrated that the biological primary structure provides the highest energy absorption capacity than other structures. This superior energy absorption capability was examined through hysteresis tests and then validated through intuitive ball free-falling tests. The work will illuminate a new pathway in the development of kinetic energy buffering and absorption materials.

Application of pole allocation to optimize passive viscous dampers represented by the Maxwell model

The Maxwell model is used to understand the realistic effectiveness of vibration reduction in the building structures. The model consists of a dashpot and spring in series. The dashpot and spring represent a viscous damper and joint between the damper and the structural frame, respectively. However, few studies have investigated the optimal damper capacity and the corresponding spring stiffness in the practical parameter ranges. Additionally, the optimal damper derived using the fixed-point theory has no relationships with that derived via pole allocation. Therefore, in this study, to examine the effects of the joint spring, the pole allocation method was used to design a structural system wherein the Maxwell model was incorporated into a single-degree-of-freedom damped model. We introduced a closed-form expression, which explicitly described the relationships between the target structural damping ratio, damper capacity, and joint spring. The Maxwell model constrained the control effectiveness using damper parameters and simultaneously suggested an optimal and realistic joint spring for the damper. Pole allocation was also applied to a multi-degree-of-freedom (M-DOF) damped structural system employing multiple Maxwell models. The newly proposed optimized joint spring could easily control the additional damping effect on the M-DOF system. The Maxwell model can be optimized almost manually. The scheme is more useful in the preliminary design stage than the previous numerical optimizations. This study extended the mathematical equation governing the building vibrations to the Maxwell model. The extended equation served as a unified description for considering structural passive control.

Synergistic effect of thermomigration and electric current stressing on damping capacity of Sn58Bi solder

In order to evaluate the vibration resistance of Sn58Bi solder in serving electronic devices, the damping capacities of Sn58Bi solders after thermomigration (TM) test at a temperature gradient of 2000 °C/cm for different time (0, 120, 360, 720, and 1440 h) were characterized under electric current stressing (0, 4.0, and 8.0 A). The results indicate that the phase segregation of TM-tested Sn58Bi solders determines the damping performance of solders. The Bi-rich layer thickens with prolonged TM time and migrates in the direction from high temperature to low temperature. Both the critical strains (the values of dislocation getting rid of pining points) of strain-amplitude-related damping capacity curves increases with prolonged TM time, while decreases with increasing electric current. Moreover, both strain-amplitude-related and temperature-related damping capacity shows a general decreasing trend with prolonged TM time, while increases exponentially with increasing electric current. In addition, the damping mechanism changes from dislocation motion to phase boundary sliding with increasing temperature, and the transition temperature decreases with increasing current but generally increases with TM time.

Study on mechanical properties and vibration reduction effect of a novel mesh-type elastic cushion plate with orifice: Theory, simulation and test

Elastic cushion plates in fastener systems play a critical role in controlling vibrations and noise, yet enhancing their damping capacity while maintaining cost-efficiency remains a persistent challenge. This paper presents a Novel Mesh-Type Elastic Cushion Plate with Orifices (NMTECPO), featuring innovative structural modifications that leverage air-damping mechanisms to achieve superior performance. Unlike conventional elastic cushions, NMTECPO incorporates a unique mesh structure with variable orifices and chamber volumes, significantly boosting its damping properties. Key structural parameters influencing the stiffness and damping characteristics of the NMTECPO such as orifice aperture, chamber volume, loading frequency, and loading amplitude, are identified through theoretical derivation and validated by extensive comparative tests. A fluid–structure interaction finite element model further demonstrates enhanced damping performance by optimizing the orifice aperture and chamber volume. Dynamic simulations also reveal that NMTECPO exhibits superior vibration attenuation compared to traditional cushion plates. The proposed NMTECPO offers a novel approach by effectively integrating structural innovations and parameter optimization to improve vibration damping, providing a cost-efficient solution with potential for future engineering applications and structural refinement.

Uplift derailment for near-fault high speed train-track-hybrid control cable-stayed bridge system

Seismic uplift of a high-speed rail (HSR) cable-stayed bridge’s bearing affects train safety. Existing technique lacks improved seismic isolation in the vertical direction due to the bearing’s vertical stiffness. Based on the on-site dynamic test and train derailment table experiments and different software, the train running safety of the semi-floating system of the cable-stayed bridge-rail-train system was analyzed using different damping and isolation control strategies. The larger vertical seismic component increases the danger of flange climb derailment when subjected to near-fault earthquakes. After installing lateral/or viscous fluid dampers (VFDs) and magnetorheological (MR) bearing (A = 3.0), the bridge has an obvious bearing uplift response. Still, it is not enough to threaten the structure, and the seismic damping capacity of the bridge structure is improved, making the train ride safe. This research presents discoveries on the impact of bearing uplift on train operational safety. Specifically, it reveals that the lifting of the end bearings on both sides of the main girder is not synchronized. This investigation presents a technical reference for comparable initiatives.

Assessing the behavior of highly damped multilayered structures with controllable patches using condensation models

This study presents the finite element modeling of an adaptive sandwich structure that can be configured to exhibit various behaviors depending on the arrangement of the temperature fields in its core, which is made of a shape memory polymer with outstanding damping capacity. The sandwich structure is divided into patches corresponding to homogeneous temperature fields. Each patch is modeled as an equivalent thin plate using a condensation model and the effective properties are determined by preserving the real part of bending, shear (transverse) and extension (quasi-longitudinal) wavenumbers. The damping loss factor is estimated independently using the forced response from an analytical discrete model of the sandwich structure and the Power Input Method. Two different configurations of the sandwich structure are presented: in the first, the modal behavior of the sandwich structure is slightly affected; In the second, vibrations are reduced throughout the frequency range. The use of a suitable condensation model can be particularly interesting for solving optimization problems and determining optimal configurations. The behavior of the sandwich structure can be evaluated with reduced computational cost whenever an update of the temperature fields is required.

Orientation engineering of magnesium alloy: A review

Mg and its alloys have garnered significant attention due to their exceptional properties, including low density, good damping capacity, biocompatibility, recyclability, and high hydrogen storage capacity. These attributes position them as promising materials for applications in aerospace, transportation, electronics, and biomedical. The wrought Mg alloys, particularly in sheet form, are important materials for manufacturing lightweight structural components. However, their application is often constrained by relatively low room temperature formability. Preferred orientation, also known as texture, plays a crucial role in determining the plasticity and formability of Mg alloys. In this paper, we propose the concept of “orientation engineering”, which involves controlling the crystallographic orientation, thereby enhancing the plasticity and formability of Mg alloys. This review addresses two main aspects: firstly, it systematically explores how preferred orientation influences the plasticity and formability of Mg alloys, providing a foundation for orientation engineering. Secondly, it comprehensively introduces the development of methods to control grain orientation distribution, including alloying, pre-deformation, and asymmetric processing. This review might enhance the scientific understanding of orientation modification in Mg alloys and offer valuable guidance for future research on high-formability Mg alloys.

Enhanced mechanical and damping properties of Cu-Modified Al-Ni eutectic alloys: Solid-solution and precipitation hardening effects

The study aimed to analyze the mechanical properties, precipitation strengthening, and microstructure of Al-Ni-Cu alloys to understand their enhanced characteristics. Additionally, the damping behavior was examined using a dynamic mechanical analyzer across a continuous heating temperature range with frequencies from 0.5 to 15 Hz. The experimental results indicate that the Al-Ni eutectic alloy, which exhibits an ultrafine Al3Ni intermetallic fiber-reinforced Al matrix, transitions to a dendritic-ultrafine eutectic composite structure. The Cu-containing alloys exhibit two distinct primary phases: α-Al and Al-Ni-Cu ternary intermetallic compounds. The eutectic matrix transforms from Al-Al3Ni to Al-Al7Cu4Ni, and subsequently to Al-Al2Cu. These microstructural evolutions result in an enhancement of the tensile yield strength from 170 MPa to 440 MPa, with additional hardening achieved through aging-induced precipitation. Moreover, the damping capacity improves with the addition of Cu at elevated temperatures, and there is an increase in frequency dependence. This paper will discuss the microstructural features, mechanical properties, deformation behaviors, and damping properties in detail.

A Comprehensive Review on the Viscoelastic Parameters Used for Engineering Materials, Including Soft Materials, and the Relationships between Different Damping Parameters.

Although the physical properties of a structure, such as stiffness, can be determined using some statical tests, the identification of damping parameters requires a dynamic test. In general, both theoretical prediction and experimental identification of damping are quite difficult. There are many different techniques available for damping identification, and each method gives a different damping parameter. The dynamic indentation method, rheometry, atomic force microscopy, and resonant vibration tests are commonly used to identify the damping of materials, including soft materials. While the viscous damping ratio, loss factor, complex modulus, and viscosity are quite common to describe the damping of materials, there are also other parameters, such as the specific damping capacity, loss angle, half-power bandwidth, and logarithmic decrement, to describe the damping of various materials. Often, one of these parameters is measured, and the measured parameter needs to be converted into another damping parameter for comparison purposes. In this review, the theoretical derivations of different parameters for the description and quantification of damping and their relationships are presented. The expressions for both high damping and low damping are included and evaluated. This study is considered as the first comprehensive review article presenting the theoretical derivations of a large number of damping parameters and the relationships among many damping parameters, with a quantitative evaluation of accurate and approximate formulas. This paper could be a primary resource for damping research and teaching.

Investigation on corrosion behaviour of metal oxide nanoparticles reinforced magnesium composites by salt spray and immersion corrosion test methods

ABSTRACT This study explores the increasing utilisation of lightweight materials, particularly magnesium (Mg) alloy, in sectors such as automobile, aerospace, and marine due to its notable advantages such as high strength-to-weight ratio, good castability, and excellent damping capacity. Despite these merits, Mg alloy faces challenges, notably in wear and corrosion resistance. The research focuses on enhancing the corrosion resistance of Mg alloy by incorporating Zinc Oxide (ZnO), Manganese Oxide (MnO), and Titanium Oxide (TiO2) nanoparticles. The alloy AZ91D and three nanocomposites, namely AZ91D + 1% ZnO, AZ91D + 1% MnO, and AZ91D + 1% TiO2, were manufactured using a stir squeeze casting technique combined with an ultrasonication process. To confirm the even distribution of reinforcement particles, Optical Microscope (OM), Scanning Electron Microscope (SEM) and High-Resolution Scanning Electron Microscope (HR-SEM) were employed. X-ray Diffraction (XRD) analysis revealed the presence of matrix and reinforcement material with intermetallic precipitates around the grain boundaries. Corrosion properties were assessed following ASTM standards and utilising a 3.5% NaCl concentration. The study found that AZ91D + 1% TiO2 nanocomposites exhibited superior corrosion resistance compared to the AZ91D alloy, showing a remarkable 77.78% and 69.89% improvement in corrosion behaviour under salt spray and immersion environments, respectively, after 48 hours.

Damping capacity in cast FeMn binary alloys

There were few works on cast FeMn binary damping alloys, although many studies have been conducted on deformation-processed counterparts. The cast Fe(15–21)Mn alloys were prepared to investigate their damping capacity in this work. The optimal Mn contents for damping capacity in both the as-cast FeMn binary alloys and solution-treated ones was ∼ 19 %, 2 % higher than that in the deformation-processed counterparts. The solution treatment obviously improved the damping capacity in the as-cast Fe15Mn alloys but remarkably deteriorated the damping capacity in the as-cast FeMn alloys with the Mn content above 17 %. An inverse dependence on the amount of α′-martensite existed in both the as-cast Fe(15–19)Mn alloys and solution-treated ones, but the dependence was weak in the latter. The dual role played by the α′-martensite could explain the different effects of it on the damping capacity.

Excellent mechanical and damping properties simultaneously achieved in partially recrystallized Fe-Mn-Nb alloy

We propose a novel approach to tackle the intrinsic trade-off between the mechanical and damping properties of a cold-rolled Fe-17Mn-Nb alloy by tailoring the fraction, size and spatial distribution of recrystallized (Rexed) grains, the latter results from the initial micro-segregation of Mn during solidification because higher Mn content in the interdendritic region can promote more NbC particles dissolved for stronger retardation on Rex. An unprecedented combination of mechanical and damping properties, including ultimate tensile strength (UTS) of 920 MPa and the logarithmic decrement of vibration amplitude (δ) of 0.082 (measured at the 0.1 % strain with 1 Hz), is achieved by forming the partially Rexed microstructure consisting of retained austenite (RA) grains and ε-martensite. The austenite grains that had been reverted from the high-Mn-content region could not Rex during the annealing at 700 °C and transformed to the coarse ε blocks with the dense dislocations during cooling, contributing to the strengthening; whilst those reverted from the low-Mn-content region Rexed and then transformed to the fine ε lamellas; contributing to the damping capacity. Therefore, the different UTS-δ synergies can be realized by controlling the fraction and size of Rexed grains during the annealing to meet the specific engineering requirement.

Influence of Silicon on Solidification Behavior, Microstructure and Oxidation Resistance of Gray Iron for Cookware Applications

Gray iron, a widely used engineering material, is favored for its desirable properties such as good damping capacity, thermal conductivity, and corrosion resistance. However, when exposed to elevated temperatures over time, issues like oxidation and graphite depletion can impact its durability. High-silicon gray iron, with elevated silicon content exceeding 3.0%, is known for its ability to withstand heat and oxidation, making it suitable for many applications, including cookware. This study investigates the impact of varying silicon levels (2.00-4.56%Si) on the solidification behavior, microstructure, and oxidation resistance of gray iron. Three heats with different silicon concentrations were produced and analyzed. Results indicated that higher silicon content increases the eutectoid temperature, stabilizes the ferritic structure, and introduces Type-D graphite in the microstructure. Graphite depletion was observed only in samples with 2.00%Si. The oxidation resistance improved with higher silicon content, as evidenced by a decrease in weight gain after exposure to 800 °C for 4 hours. This suggests the potential of using lower silicon levels in gray iron for cookware applications, balancing material cost with good impact resistance.

Preparation and research on the structure and properties of high damping Mn-Cu alloy

With the widespread application of Mn-Cu alloys with high damping capacity in industry, higher requirements of mechanical were properties proposed. In this work, the microstructure, damping properties, and mechanical properties of Mn-Cu alloys prepared by three different heat treatment processes were investigated. The results showed that the Mn-Cu alloy had good comprehensive properties after forging, rolling, solid solution at 850 °C for 2.5 h, and aging for 8 h. The yield strength, tensile strength and specific damping capacity were 336 MPa, 620 MPa, and 44 %, respectively. It was found that after aging treatment, the Mn-Cu alloy occurred spinodal decomposition and martensitic transformation, resulting in Mn-rich regions and lattice distortion that prevented dislocation movement and improved mechanical properties. At the same time, martensitic transformation promoted the formation of high-density twins and improved damping capacity. This work could provide experimental guidance for the production of Mn-Cu alloys with good comprehensive properties.

Correlation of austenite grain size with ε-/α′-martensitic transformation and mechanical properties in a high-manganese damping steel

One of the core studies on low stacking fault energy (SFE) high-manganese steel is to maintain excellent damping capacity while achieving high strength and toughness. The austenite grain size (AGS) in high-Mn steel affects its SFE and even the strength-plasticity and damping capacity of the steel, but the detailed mechanism related to martensitic transformation has not been clarified. In this study, Fe-17Mn high-Mn damping steel is used as the material to obtain austenite grains of different sizes by controlling the cold rolling and annealing processes. By using in-situ tensile testing, damping capacity testing, and various microscopic analytical techniques, the influence of AGS on the thermal/deformation induced martensitic transformation, work hardening behavior, mechanical properties and damping capacity of the steel is mainly studied. The results indicate that the refinement of austenite grain increases the SFE of high-Mn damping steel and reduces the amount of thermal induced ε-martensite (εth) and stacking faults (SFs). The deformation induced martensitic transformations (DIMTs) in high-Mn damping steel during tensile deformation include γ→εD, εth→α′ and εD→α′ transformation. The deformation induced ε-martensitic transformation is more helpful to improve the work hardening rate than deformation induced α′-martensitic transformation. Due to the concentration of strain partitioning at grain boundaries, twin boundaries and phase boundaries, refinement of austenite grain can promote deformation induced ε-martensitic transformation and improve the steel strength. However, excessively small austenite grains can suppress deformation induced α′-martensitic transformation leading to a significant decrease in elongation. Under the synergetic effects of grain refinement strengthening and multiple martensitic transformations, when the average AGS is about 4.0 μm, the steel has high strength and high plasticity, with a tensile strength of 919 MPa, a yield strength of 518 MPa and an elongation of 46.4 %. The product of tensile strength and elongation is up to 42.6 GPa·%. At low or high strain amplitudes, the damping capacity of this steel shows an opposite trend with the refinement of AGS. The damping capacity of the steel gradually increases with grain refinement at low strain amplitudes of 0.01 %–0.065 %, mainly due to the reduction of the content of weak pinning points. At high strain amplitudes of 0.065 %–0.1 %, the damping capacity of the steel gradually decreases for the reduction of damping sources with the refinement of grain size.

Sustainable thermoplastic elastomers based on thermoplastic polyurethane and ground tire rubber

AbstractIn this research, blends are prepared of thermoplastic polyurethane (TPU), ground tire rubber (GTR) and its devulcanized version (dGTR). The primary objective is to produce thermoplastic elastomers wherein TPU is partially substituted by GTR or dGTR obtained from used tires, thereby forming a blend with a favorable cost/value ratio and a smaller environmental footprint. Throughout the experiment, the rubber content of the blends is varied between 0 and 50 wt% and the effect on mechanical properties is investigated. The blends are compounded with a twin‐screw extruder, after which sheet samples are produced by injection molding. With a view to a possible future industrial application, it is important that both the compounding and the injection molding of the specimens are easy to perform, even with a 50 wt% filler content. Increasing the amount of rubber phase reduce the tensile strength and elongation at break of the blends. Unfortunately, devulcanization did not significantly improve the properties of the blends. Overall, even at a (d)GTR content of 50 wt%, an elongation at break of 300% is achieved, which allows the use of the blends as thermoplastic elastomers. In addition, dynamic tests show that the rubber phase increases the damping capacity of the samples.

Field study on vibration characteristics of geocell-reinforced aeolian sand subgrades

Constructing highways in deserts is expensive due to the difficulty of acquiring materials; utilizing aeolian sand effectively has become a problem, especially in the Xinjiang region, where the desert widely occurs. This paper aims to investigate the vibration response of a geocell-reinforced aeolian sand subgrade under traffic loading based on field tests of highways in deserts. The vibration acceleration response of geocell-reinforced aeolian sand and gravelly soil upper roadbed structures is tested. The field test results illustrate the effects of dynamic loading on geocell-reinforced aeolian sand roadbeds, and the thickness substitution ratio between geocell-reinforced aeolian sand roadbeds and conventional gravelly soil roadbeds is determined and verified based on the vibration acceleration monitoring values. The results show that the vibration response induced by the test vehicle is concentrated within the 30 Hz frequency band, and the higher the vibration frequency, the faster the vertical decay in the road. The vibration damping capacity of the reinforced aeolian sand roadbed is better than that of the gravelly soil roadbed; when replacing the gravelly soil roadbed with the reinforced aeolian sand roadbed, the substitution ratio is 0.31–0.42. It is verified that half thickness of gravel soil on roadbeds can be replaced by geocell-reinforced aeolian sand under different working conditions. The results of this study can provide reference data for the design of highway subgrades in deserts.

Rail pad damping characteristics in track vibration reduction evaluated through hammer tests and theoretical analysis

Although the majority of existing research addresses the stiffness characteristics of rail pads, the considerable impact of damping on vibration reduction underscores its significant research importance. In this study, the hammer test and theoretical calculation are both employed to assess the damping capacity across three rail pad types: prismatic (PRP), grooved (GRP), and mesh-type high-damping (MTHDRP). Through the hammer test, the MTHDRP notably surpassed GRP and PRP, achieving higher damping ratios by 51.40 % and 49.71 %, respectively, leading to significant vibration reductions in the track bed and rail. Comparison tests between three types of rail pads highlighted the enhanced performance of the MTHDRP, as it not only reduced vibration amplitudes and enhanced decay rates but also decreased vibration levels by 2−5 dB. Moreover, we established a refined finite element model of the fastener system and integrated it with the Logarithmic Decay Rate (LDR) method. Our findings demonstrate that this combination facilitates the calculation of the damping ratio of the rail pad. Furthermore, we conducted a comparative analysis between the LDR method and the envelope method, confirming its superior efficiency and reliability. Finally, the LDR method is used to predict the damping ratio of the rail pad with varying stiffness, showing that the softer the rail pad, the higher the corresponding damping ratio. Overall, our insights bridge the gap in theoretical calculations and experimental studies on rail pad damping characteristics, offering crucial guidance for rail pad selection in track vibration mitigation.