Lowest Natural Frequency Research Articles

Dynamic Analysis of a Curved Beam With Tuning of Elastic Modulus and Mass Density in Circumferential Direction

Abstract Deformation and stress fields in a curved beam can be tailored by changing its mechanical properties such as the elastic modulus/mass density, which is typically done using functionally graded materials (FGM). Such functional gradation can be done, for instance, by using particles or fiber-reinforced materials with different volume fractions along the beam length. This article presents in-plane vibrations of functionally graded (FG) cantilevered curved beams. Both semi-analytical and finite element modeling are employed to find natural frequencies and mode shapes of such beams. The natural frequencies obtained from the analytical solution and finite element analysis are in close agreement with an error of 6.2% when the variance of material properties gradation is relatively small. In the analytical approach, the direct method is employed to derive the governing linear differential equations of motion. The natural frequencies and mode shapes are obtained using the Galerkin and the finite element methods. First, three natural frequencies and corresponding mode shapes are analyzed for different elastic modulus/mass density distribution functions. Furthermore, the natural frequencies of FG curved beams with a crack are also investigated. Our results indicate that larger cracks near the clamped side of the beam significantly decrease the first natural frequency. In the second and third vibration modes, cracks located in the area with a maximum moment result in the lowest natural frequency values. However, the second and third natural frequencies of the cracked curved beam are not affected by the presence of a crack, if the crack is located at the nodal points of the curved beam.

How to Exploit the Glass Mass for Damping a Building?

The worlds spectacular skylines host tall and slender buildings to create a maximum of office, residential and commercial space on a minimized footprint. These structures need to cope with increasing wind forces at height and are additionally affected by wind-induced vibration due to their lower natural frequencies. The resulting vibrations make users uncomfortable. Therefore, heavy tuned mass dampers are installed in structures and occupy valuable space especially in the costliest top-floors. As an example, Taipei 101’s steel damper is located between the 87th and 91st floor and weights astonishing 660 metric tons. This raises the need for additional reinforcement which increases cost and carbon footprint.Most buildings in expensive metropolises are cladded with remarkable glass facades. Therefore, we asked the question if it was possible to use the existing mass – more specifically the glass mass in a Double‑Skin Facade – to dampen the building’s movement, create a comfortable space for the user, exploit more floor area for the investor and finally to minimize the amount of building material to reduce carbon footprint for society. The idea was realized in a collaborative research effort of TU Berlin, BTU Cottbus-Senftenberg and Josef Gartner GmbH that resulted in a full-scale mock-up of a Double‑Skin Facade. Its outer skin can move laterally on a guide rail system. As the building starts to move, the facade's inner skin remains fixed to the base structure while the outer skin follows the building’s movement in a delayed manner due to its mass inertia. The fixed inner skin and the moveable outer skin are connected by a spring system that is tuned to the first natural frequency of the base structure. During the motion of the facade’s outer skin, the spring system redirects the relative movement and generates a stabilizing force for the base structure in the opposite direction. Additionally, an electrical machine is placed in between to provide an adjustable damping effect for semi-active and passive control. It also serves the purpose of a generator to study the opportunity to harvest energy. The paper shows the structural design options for the novel facade concept in the context of a project review of Double-Skin and Closed-Cavity Facades. The function of a full-scale mock-up, its fabrication and installation are described to show feasibility and ongoing challenges. First test results reveal a close match between theoretical assumptions and the applied testing. This engineering-driven and experimentally validated design opens a new field of architectural options in sustainable facade design which is focused on tuning physical parameters that affect the damping properties of the global structure.

Spatial compliance modeling and optimization of a translational joint using corrugated flexure units

Compliant mechanisms with corrugated flexure units have been attracting increasing attention due to their large range of motion. However, most research has considered in-plane compliance, whereas the out-of-plane performance, which affects the load-carrying ability, has seldom been studied. In this paper, an analytical model for the spatial compliance of a corrugated flexure translational joint is formulated. The in-plane compliance of the corrugated flexure translational joint is modeled by the Maxwell–Mohr method and compliance matrix method. For the out-of-plane compliance, a modification method is proposed for the closed-form analytical solution based on a finite element analysis with shell elements. The corrugated flexure translational joint is further optimized to achieve a high in-plane and out-of-plane off-axis stiffness ratio, low first-order natural frequency, and large range of motion. Experiments were conducted to verify the effectiveness of the method.

Experimental parametric study on hydroelastic behaviour of a 15000-TEU container ship based on segmented ship model

ABSTRACT Large-scale ships with high elasticity and low natural frequency, behave high dynamic response amplitude under impulsive wave loads (whipping) and short period waves (springing), which could result in serious ultimate loads and fatigue damage. The segmented model test is a more powerful approach for the ship hydroelastic analysis compared with ship seakeeping test. However, the effect of some test parameters on the hydroelastic responses is still not a clear statement. Therefore, the number of segments, propulsion mode and backbone form are chosen for the parametric study on ship hydroelastic behaviour. A three-dimensional (3-D) nonlinear time-domain hydroelastic method is developed, in which the nonlinearity of instantaneous wetted surface and slamming force are considered. Through the analysis of natural frequencies and vertical bending moments (VBM), the impact on hydroelastic behaviour is discussed. Results show that self-propelling models with variable cross-section backbones are more suitable and reliable in studying nonlinear hydroelastic behaviour.

Lateral Vibration Control of Long-Span Small-Radius Curved Steel Box Girder Pedestrian Bridge with Distributed Multiple Tuned Mass Dampers.

Curved pedestrian bridges are important urban infrastructure with the desired adaptability to the landscape constraints and with aesthetic benefits. Pedestrian bridges feature thin cross-sections, which provide sufficient load capacities but lead to low natural frequencies that make the bridges susceptible to vibration under pedestrian excitation. This study investigates the lateral vibration of a curved bridge with a small radius down to 20 m, proposes an approach to mitigate the lateral vibration of bridges with large curvatures using distributed multiple tuned mass dampers (MTMD), and conducts in-situ bridge tests to evaluate the vibration mitigation performance. The lateral vibration was investigated through in-situ tests and finite element analysis as well as the code requirements. The key parameters of the distributed MTMD system were improved by strategically selecting the mass ratio, bandwidth, center frequency ratio, and damper number. The results showed that the curved bridge was subjected to significant lateral vibration due to the coupling of torque and moment, and the recommended design parameters for the studied bridge were derived, i.e., the total mass ratio is 0.02, bandwidth is 0.15, center frequency ratio is 1.0, and damper number is 3. The proposed approach effectively improves the deployment of MTMD for lateral vibration control of the curved bridge. The field tests showed that the vibration was reduced by up to 82% by using the proposed approach.

Free vibration analysis of polymer pin-reinforced foam core sandwich composite panels

This study deals with numerical and experimental free vibration analysis of through-the-thickness cylindrical polymer pin-reinforced foam core sandwich composite panels of two different core thicknesses. Four different pin-reinforcement configurations with varying pin diameters and pin center distances were used. First five non-zero eigenfrequencies were retrieved along with their eigenmodes in the numerical analysis. Experimental modal analysis was done for the validation of the numerical analysis. The results revealed that the pin-configuration with the densest pin allocation and the biggest pin diameter provided the highest natural frequencies, and the non-reinforced composites had the lowest natural frequencies. The increase in the pin diameter had a slightly more pronounced effect on the increase of the eigenfrequencies than the increase in the pin’s densities. This work also demonstrated the impact of the core thickness on the natural frequencies.

Simulation Analysis of Vibration Characteristics of the Submerged-propeller Shaft Coupling System

The vibration characteristics of the submerged-propeller shaft coupling system are studied in this paper. Firstly, Based on the fluid structure interaction theory on acoustics wave equation, the vibration analysis model of the propeller-shaft system under water is established and computed. And the vibration characteristics of coupling system is analysed by comparing the shaft system and the submerged-propeller system. The results show that the natural vibration of the coupling system presents complicated propeller-shaft strong or weak coupling characteristics. Comparing the natural vibration and frequencies of the shaft system and the submerged-propeller system, all of the coupling system modes are corresponding to the shaft system or the submerged-propeller system in low frequency range. And there is strong transverse coupled vibration of coupling system near the propeller’s 1st-order transverse vibration frequency, which appears as propeller’s 1st-order transverse vibration coupling shaft’s 2nd-order transverse vibration. That indicates the strong transverse coupled natural vibration of the coupling system is easy to be excited near the low order natural frequency of propeller. Which may cause propeller’s transverse excitation force to be easily transmitted to the hull through the bearings under non-uniform flow, resulting in the severe vibration of the hull stern.

Parabolic tapering piezoelectric rotational energy harvester: Numerical analysis with experimental validation

Inadequate host beam design leads to the inefficiency of any piezoelectric vibration energy harvester. This article presents a parabolic tapering width piezoelectric energy harvester under rotational excitation. The Euler-Bernoulli theory, Hamilton's principle, and Galerkin's approach are used for mathematical modeling to investigate the frequency characteristics and open-circuit voltage response. Finally, experiments are conducted for validation. Compared to earlier reported designs, the proposed harvester produced high voltage-per-total mass (43.618 V/Kg) and performance amplification factor (4.18), besides the advantageous low natural frequency. This research’s findings can be used in real-time health monitoring of rotating machine components and fault detection mechanisms.

Modeling and experimental investigation of asymmetric distance with magnetic coupling based on galloping piezoelectric energy harvester

This paper presents an asymmetric magnetic coupling piezoelectric energy harvester (PEH) based on galloping to scavenge low-speed wind. The piezoelectric beam of energy harvester undergoes bending and torsional vibration simultaneously due to the eccentric distance. By analyzing the kinetic energy, potential energy, and virtual work of the energy harvesting system, the mathematical model of harvester is constructed and verified by experiments. The optimal external load resistance is confirmed at different eccentric distances and wind speeds by experiments. Compared with traditional galloping piezoelectric energy harvester (GPEH), the asymmetric with magnetically coupling GPEH has a lower threshold wind speed, i.e. 2 m s−1. And the asymmetric configuration contributes to a lower natural frequency and electromechanical coupling coefficient, which results in a lower power and voltage output. The potential energy of harvesting systems at different distances between two magnets are respectively numerical analyzed in detail. The theoretical results illustrate that the energy harvester operates in monostable and bistable at different magnet distances. And the threshold wind speed of energy harvester increases when the energy harvester works at bistable. According to the above analysis, this work provides a detailed guideline for mathematical modeling and performance improvement of asymmetric PEH based on galloping.

Structural Design and Experiments of a Dynamically Balanced Inverted Four-Bar Linkage as Manipulator Arm for High Acceleration Applications

Industrial robotic manipulators in pick-and-place applications require short settling times to achieve high productivity. The fluctuating reaction forces and moments on the base of a dynamically unbalanced manipulator, however, cause base vibrations, leading to increased settling times. These base vibrations can be eliminated with dynamic balancing, which is achieved, in general, with the addition of counter-masses and counter-inertias. Adding these elements, however, comes at the cost of increased moving mass and inertia, resulting in lower natural frequencies and again higher settling times. For a minimal settling time it is therefore essential that a balanced mechanism has high natural frequencies with an optimal mass distribution. A dynamically balanced inverted four-bar linkage architecture is therefore favoured over architectures which depend on counter-masses and counter-rotating flywheels. The goal of this paper is to present and experimentally verify a structural design of a manipulator arm with high natural frequencies that is based on a dynamically balanced inverted four-bar linkage. The dynamical properties and the robustness to manufacturing tolerances are both verified with simulations and experiments. Experiments for 5.2 G tip accelerations show, when fully balanced, a reduction of 99.3% in reaction forces and 97.8% in reaction moments as compared to the unbalanced mechanism. The manipulator reached 21 G tip accelerations and a first natural frequency of 212 Hz was measured, which is significantly high and more than adequate for implementation in high acceleration applications.

Flow-Induced Vibration of Solitary Wire-Wrapped Cylinders in Axial Flow

Vibration of nuclear power plant components can cause fretting wear and fatigue that can eventually lead to component failure. Flexible, high-aspect-ratio components under flow, such as the wire-wrapped cylindrical fuel elements in a liquid metal-cooled fast reactor core, are particularly susceptible to vibration due to their low natural frequencies. The flow-induced vibrations experienced by such components tend to be random and of low amplitude and frequency; however, at critical flow velocities these components can experience self-excited, fluid-elastic instabilities that can lead to immediate failure. Such failures of critical reactor components, particularly those that act as fission product barriers, can lead to prolonged shutdowns of nuclear power plants and even to their permanent closure. Thus, a better understanding of the vibration response of wire-wrapped cylinders in axial flow is needed. This study details the development of a theoretical model that incorporates the effects of a helical wire wrap along a cylinder to understand its impact on the dynamic response of the cylinder under flow. This theoretical model is compared against experimental vibration data of varying geometries of solitary wire-wrapped cylinders in confined axial flow. The results of this study provide an improved knowledge of how a helical wire wrap can affect the dynamic response of a cylinder under flow.

Mechanical, acoustic and vibration performance of intra‐ply Kevlar/PALF epoxy hybrid composites: Effects of different weaving patterns

AbstractThe influence of different weaving patterns on tensile, acoustic, and vibration behavior of intra‐ply Kevlar and pineapple leaf fiber (PALF) hybrid woven fabric reinforced epoxy matrix composites was investigated. Intra‐ply hybrid Kevlar/PALF woven fabrics were analyzed by three weaves: plain, twill, and basket. Also, epoxy matrix, pure Kevlar, and PALF woven fabric composites were analyzed for comparison purposes. Results revealed that the basket‐type hybrid composites exhibited a higher tensile strength of 77 MPa compared to plain (63 MPa) and twill‐type (73 MPa) hybrid composites. Plain and twill weave hybrid composites presented higher sound transmission loss levels of 28.9 and 30.5 dB, respectively, at higher frequency levels. Free vibration analysis showed that the PALF composites had higher damping and a lower natural frequency whereas the pure Kevlar and hybrid composites (KP1, KP2, and KP3) exhibited lower damping and higher natural frequencies.

Donor-Acceptor Pyridinium Salts for Photo-Induced Electron-Transfer-Driven Modification of Tryptophan in Peptides, Proteins, and Proteomes Using Visible Light.

Tryptophan (Trp) plays a variety of critical functional roles in protein biochemistry; however, owing to its low natural frequency and poor nucleophilicity, the design of effective methods for both single protein bioconjugation at Trp as well as for in situ chemoproteomic profiling remains a challenge. Here, we report a method for covalent Trp modification that is suitable for both scenarios by invoking photo-induced electron transfer (PET) as a means of driving efficient reactivity. We have engineered biaryl N-carbamoyl pyridinium salts that possess a donor-acceptor relationship that enables optical triggering with visible light whilst simultaneously attenuating the probe's photo-oxidation potential in order to prevent photodegradation. This probe was assayed against a small bank of eight peptides and proteins, where it was found that micromolar concentrations of the probe and short irradiation times (10-60 min) with violet light enabled efficient reactivity toward surface exposed Trp residues. The carbamate transferring group can be used to transfer useful functional groups to proteins including affinity tags and click handles. DFT calculations and other mechanistic analyses reveal correlations between excited state lifetimes, relative fluorescence quantum yields, and chemical reactivity. Biotinylated and azide-functionalized pyridinium salts were used for Trp profiling in HEK293T lysates and in situ in HEK293T cells using 440 nm LED irradiation. Peptide-level enrichment from live cell labeling experiments identified 290 Trp modifications, with 82% selectivity for Trp modification over other π-amino acids, demonstrating the ability of this method to identify and quantify reactive Trp residues from live cells.

Noise and vibration characteristics of sub-fractional horsepower single-phase BLDC drives

Single-phase brushless DC (BLDC) drives are a cost-effective alternative for three-phase sub-fractional horsepower drives in automotive auxiliary applications. Inherent features of single-phase permanent magnet machines, such as high cogging torque and torque ripple, can, however, make them more audible than their three-phase counterparts. As some of these auxiliary drives are close to the passengers, where even a small amount of noise can be disturbing, the investigation into noise sources is essential to further address this challenge. In this paper, the dominant noise and vibration characteristics of single-phase BLDC machines are investigated for two different stator structures, i.e., salient-pole and claw-pole, and compared. Magnetic force density waves and finite element (FE) analyses are performed to analyze the electromagnetic forces resulting from the open-circuit condition as well as different switching strategies in the load condition. Structural analyses show that due to the mechanical structure’s lower stiffness and natural frequencies in the audible range, the example case machine with the claw-pole stator develops higher structure- and air-borne noise than the machine with the salient-pole stator.

The vibration study of a sandwich conical shell with a saturated FGP core

This paper is provided to analyze the free vibration of a sandwich truncated conical shell with a saturated functionally graded porous (FGP) core and two same homogenous isotropic face sheets. The mechanical behavior of the saturated FGP is assumed based on Biot’s theory, the shell is modeled via the first-order shear deformation theory (FSDT), and the governing equations and boundary conditions are derived utilizing Hamilton’s principle. Three different porosity distribution patterns are studied including one homogenous uniform distribution pattern and two non-homogenous symmetric ones. The porosity parameters in mentioned distribution patterns are regulated to make them the same in the shell’s mass. The equations of motion are solved exactly in the circumferential direction via proper sinusoidal and cosinusoidal functions, and a numerical solution is provided in the meridional direction utilizing the differential quadrature method (DQM). The precision of the model is approved and the influences of several parameters such as circumferential wave number, the thickness of the FGP core, porosity parameter, porosity distribution pattern, the compressibility of the pore fluid, and boundary conditions on the shell’s natural frequencies are investigated. It is shown that the highest natural frequencies usually can be achieved when the larger pores are located close to the shell’s middle surface and in each vibrational mode, there is a special value of the porosity parameter which leads to the lowest natural frequencies. It is deduced that in most cases, natural frequencies decrease by increasing the thickness of the FGP core. In addition, reducing the compressibility of the porefluid a small growth in the natural frequencies can be seen.

Spatial Assessment of Heterogeneous Tissue Natural Frequency Using Micro-Force Optical Coherence Elastography.

Analysis of corneal tissue natural frequency was recently proposed as a biomarker for corneal biomechanics and has been performed using high-resolution optical coherence tomography (OCT)-based elastography (OCE). However, it remains unknown whether natural frequency analysis can resolve local variations in tissue structure. We measured heterogeneous samples to evaluate the correspondence between natural frequency distributions and regional structural variations. Sub-micrometer sample oscillations were induced point-wise by microliter air pulses (60–85 Pa, 3 ms) and detected correspondingly at each point using a 1,300 nm spectral domain common path OCT system with 0.44 nm phase detection sensitivity. The resulting oscillation frequency features were analyzed via fast Fourier transform and natural frequency was characterized using a single degree of freedom (SDOF) model. Oscillation features at each measurement point showed a complex frequency response with multiple frequency components that corresponded with global structural features; while the variation of frequency magnitude at each location reflected the local sample features. Silicone blocks (255.1 ± 11.0 Hz and 249.0 ± 4.6 Hz) embedded in an agar base (355.6 ± 0.8 Hz and 361.3 ± 5.5 Hz) were clearly distinguishable by natural frequency. In a beef shank sample, central fat and connective tissues had lower natural frequencies (91.7 ± 58.2 Hz) than muscle tissue (left side: 252.6 ± 52.3 Hz; right side: 161.5 ± 35.8 Hz). As a first step, we have shown the possibility of natural frequency OCE methods to characterize global and local features of heterogeneous samples. This method can provide additional information on corneal properties, complementary to current clinical biomechanical assessments, and could become a useful tool for clinical detection of ocular disease and evaluation of medical or surgical treatment outcomes.

A Study on Parameters Influencing Blast-Induced Frequency Content and Dominant Frequency Attenuation

Adverse effects of the blasting vibration on surrounding structures intensify importance of investigation on the blast frequency content while it has not been fully considered in blasting design. In this study, blast-induced frequency content and dominant frequency attenuation are investigated. The results of this study and its comparison with the previous studies demonstrate that investigation of different parameters influencing blast-induced frequency content including peak blast load pressure, rise time, and falling time by the experimental pressure-time history with its Fast Fourier Transform (FFT) analysis leads to the similar results of study by the velocity-time recorded data of an infield blasting. The outcomes of this study on dominant frequency attenuation for different types of explosives but in the same material show approximately the same dominant vibration frequency in far-field for different explosives, whereas a rapid drop of dominant frequency to half of the initial value in near distance to the blasthole can be observed. Investigation on dominant frequency attenuation versus distance for the materials with different natural ground frequencies demonstrates that the geomaterial tends to pass the vibration frequency closer to its natural frequency. If the earth has a lower natural frequency, it will pass the waves with lower dominant frequencies, but it will attenuate the waves with higher dominant frequency.

Correlation of design parameters of lattice structure for highly tunable passive vibration isolator

The purpose of this study is to correlate the influence of multiple size-based design parameters of lattice structure, namely, the unit cell (UC) and strut diameter (SD) through the static and dynamics analyses for passive vibration isolation application. The lattice structures were prepared by utilizing the fused deposition modeling (FDM) additive manufacturing (AM). The samples were designed to retain lattice structure’s unique advantages while also conserving material consumption to fulfill the energy and cost demand. Through the static test, the crush behavior, failure mechanism, and mechanical properties were determined. The stiffness of lattice structure exhibited an increasing relationship with the unit cell and strut diameter where smaller unit cell and bigger strut diameter produced higher strength, and with that, higher load can be sustained. Through the dynamic vibration transmissibility test, it was found that the dynamic vibration results follow closely the trend in the static analysis. Lattice structure with larger unit cell and smaller strut diameter showed larger effective isolation region due to lower natural frequency value. The trade-off limit between stiffness for a lower natural frequency of the proposed design parameters was determined from the two parts analyses. The results suggest that most lattice isolators from the pool of design parameter combinations in this study have sufficient strength to withstand the predefined mass load and provide the most region for vibration isolation. The two proposed design parameters can later be used for a major or minor tuning of lattice isolators for other specific applications.

Vision sensor based residual vibration suppression strategy of non-deformable object for robot-assisted assembly operation with gripper flexibility

PurposeIndustrial robots are extensively deployed to perform repetitive and simple tasks at high speed to reduce production time and improve productivity. In most cases, a compliant gripper is used for assembly tasks such as peg-in-hole assembly. A compliant mechanism in the gripper introduces flexibility that may cause oscillation in the grasped object. Such a flexible gripper–object system can be considered as an under-actuated object held by the gripper and the oscillations can be attributed to transient disturbance of the robot itself. The commercially available robots do not have a control mechanism to reduce such induced vibration. Thus, this paper aims to propose a contactless vision-based approach for vibration suppression which uses a predictive vibrational amplitude error-based second-stage controller.Design/methodology/approachThe proposed predictive vibrational amplitude error-based second-stage controller is a real-time vibration control strategy that uses predicted error to estimate the second-stage controller output. Based on controller output, input trajectories were estimated for the internal controller of the robot. The control strategy efficiently handles the system delay to execute the control input trajectories when the oscillating object is at an extreme position.FindingsThe present controller works along with the internal controller of the robot without any interruption to suppress the residual vibration of the object. To demonstrate the robustness of the proposed controller, experimental implementation on Asea Brown Boveri make industrial robot (IRB) 1410 robot with a low frame rate camera has been carried out. In this experiment, two objects have been considered that have a low (<2.38 Hz) and high (>2.38 Hz) natural frequency. The proposed controller can suppress 95% of vibration amplitude in less than 3 s and reduce the stability time by 90% for a peg-in-hole assembly task.Originality/valueThe present vibration control strategy uses a camera with a low frame rate (25 fps) and the delays are handled intelligently to favour suppression of high-frequency vibration. The mathematical model and the second-stage controller implemented suppress vibration without modifying the robot dynamical model and the internal controller.

Boosted microwave absorption properties of CoFe2O4 with extraordinary 3D morphologies

Due to their strong magnetic dissipation and low cost, ferrites were one of the first generations of microwave absorbers. However, ferrites also have some drawbacks, such as a low natural resonance frequency (fr), a lack of dielectric loss, and high density. In order to overcome these drawbacks and improve the microwave dissipation features of ferrites, we successfully prepared CoFe2O4 samples with flower-like and crochet ball-like morphologies (named as M1 and M2 samples, respectively). Structural and optical properties were studied by XRD, FTIR, and UV–Vis light absorption. The microwave performance of CoFe2O4 was significantly improved with the reflection loss (RL) of M2 of −40 dB. Furthermore, M1 and M2 samples achieved an ultra-wide effective absorption bandwidth (EAB) of 13 and 12.5 GHz, respectively. It is worth noticing that the EAB of M1 was one of the largest EABs for CoFe2O4 that has been reported so far. The excellent microwave dissipation of M1 and M2 samples in the 2–18 GHz frequency range was due to the enhancement of ferrite fr to the high-frequency range and the introduction of dielectric loss to achieve impedance matching. The flower-like and crochet ball-like morphologies with many pores of M1 and M2 also resolved the high-density issue of CoFe2O4. With the relatively good values of RL and EAB combined with low filler loading, thin thickness, and low density, M1 and M2 samples could be expected to be promising microwave absorbers for practical applications.