Cross-section Cantilever Research Articles

Three-Component Accelerometer Based on Distributed Optical Fiber Sensing

The three-component accelerometer array has garnered significant attention in seismic wave detection. In this paper, we designed a three-dimensional optical fiber accelerometer based on a circular cross-section cantilever beam and distributed optical fiber strain interrogator. An externally modulated optical frequency domian reflectometry (OFDR) system with centimeter-level spatial resolution is developed to demodulate the dynamic strain on fiber. An algorithm to reconstruct the three-component acceleration from the strain of the optical fiber was derived, and the factors affecting the errors in reconstruction were also investigated. The developed accelerometer exhibits comparable performance to an electrical accelerometer in the experiment. The correlation coefficient between the reconstructed signal waveforms from the two accelerometers exceeded 0.9, and the angular error was less than 8°. The proposed accelerometer is highly compatible with distributed optical fiber sensing technology, presenting significant potential for long-distance array deployment of three-component seismic wave monitoring.

Flutter Analysis and Morphing Evaluation of Biomimetic Wing Structure

Advanced aircrafts have incorporated bio-inspired morphing structures to adapt to multienvironment and perform multimission. But it will cause serious issues with structural reliability and aeroelastic stability. This paper studies the critical flutter speed of a morphing wing structure and evaluates the deformation strategies. First, a biomimetic wing is considered as a variable cross-section cantilever beam, and the flutter model with Theodorsen unsteady aerodynamics is theoretically derived. The finite element theory is used to discretize the obtained PDEs with variable coefficients. Second, three typical wing models are examined to verify the model’s accuracy against finite element simulation findings for modal frequencies and critical flutter speeds. The results indicate good agreement, with errors of less than 3% for modal frequencies and fewer than 2.1% for critical flutter speeds. Thirdly, the flutter wind speeds are examined to assess the aeroelasticity properties for three different morphing strategies of biomimetic wing structures. The findings show that both forward bending of the elastic axis and greater density concentration near the wing root increase flutter speed. And the density distribution has a smaller effect on flutter speed than elastic axis bending. When it comes to static aeroelasticity, excessive folding ratios cause divergence problems.

Effect of Taper Forms on the Dynamic Response of A Rectangular Cross Section Cantilever Beam

Effect of Taper Forms on the Dynamic Response of A Rectangular Cross Section Cantilever Beam

Semi-analytical study of defective pile-beam systems under transient excitation: Implications for low-strain testing

This paper establishes a theoretical model of defective pile-beam system. The soil around the pile is modeled as a continuous three-dimensional model. The pile is modeled as a Rayleigh-Love rod model that considers its transversal inertia effect. The defect of the pile is simulated by a pile segment with a different radius from the normal pile segment. The impedance function recursion method, along with RSPT and AIFTM, is utilized to derive the impedance of the pile top. The beam is modeled as a Timoshenko beam and the transient excitation is applied at the connection between the pile and the beam. Analytical solution for the dynamic response of the system in the frequency domain is derived, and the discrete Fourier transform is used to obtain a semi-analytical solution for the time-domain response. The velocity at the connection between the pile and beam and the pile body can be measured to assess defects. The semi-analytical solution presented in this paper was validated through comparison with FEM results. Reflection from necked segment is more pronounced at pile-beam connection than at pile body. Both velocity curves at these two points should be measured when beam cross-section height is large to determine pile integrity. The peak value and arrival time of characteristic waves are influenced by burial depth, necking section parameters, beam cross-section height, cantilever length, and soil parameters. These findings can provide guidance for the application of low strain integrity testing in pile-beam systems.

A simplified method to assess the elasto-plastic response of standalone tubular Offshore Wind Turbine supports subjected to ship impact

A simplified method to assess the elasto-plastic response of standalone tubular Offshore Wind Turbine supports subjected to ship impact

AFM probe for measuring ∼10−5 ultra-low friction coefficient: Design and application

Superlubricity provides a novel approach to addressing friction and wear issues in mechanical systems. However, little is known regarding improving the atomic force microscope (AFM) friction coefficient measurement resolution. Accordingly, this study established the theoretical formula for the AFM friction coefficient measurement and deduced the measurement resolution. Then, the formula was applied to the AFM probe with a rectangular cross-section cantilever. The measurement resolution is associated with the dimensional properties of the AFM probe, the mechanical properties of the cantilever material, the properties of the position-sensitive detector (PSD), and probably the anti-vibration performance of the AFM. It is feasible to make the cantilever as short as possible and the tip as high as possible to improve the measurement resolution. An AFM probe for measuring an ultra-low friction coefficient was designed and fabricated. The cantilever’s length, width, and thickness are 50, 35, and 0.6 µm, respectively. The tip height is 23 µm. The measurement resolution can reach 7.1×10−6 under the maximum normal force. Moreover, the AFM probe was applied to measure the superlubricity between graphene layers. The friction coefficient is 0.00139 under 853.08 nN. This work provides a promising method for measuring a ∼10−5 friction coefficient of superlubricity.

Radial disturbance compensation device of cylindrical cantilever beam using embedded piezoelectric ceramics with bending mode

To eliminate the disturbance in all-radial directions of the circular cross-section cantilever beam, this study proposes an embedded piezo-compensator (EPC). Different from cantilever beams with rectangular cross-sections, cantilever beams with circular cross-sections have isotropic stiffness in all-radial directions. This feature makes cylindrical cantilever beams have been widely used in various mechanical structures. However, the current trend towards more compact and more lightweight design in machinery poses a huge challenge to its anti-disturbance ability. Most of the current studies are based on rectangular cantilevers and eliminate the disturbances in one direction. Research on eliminating the disturbances in whole radial direction is rarely reported. Therefore, based on the characteristics of the circular cross-section and piezoelectric materials, an EPC is proposed. The structure and output model of the proposed device are presented and established. Experimental results show that the proposed device can reduce the disturbance by more than 90% in the frequency range from 0 Hz to 600 Hz. At 1000 Hz, it can still reduce disturbance by 69%. With this method, disturbance compensation device can be deployed on the cylindrical cantilever without significant modifications to the original structure, which expands the application in size-sensitive scenarios.

Design and Research on Variable Cross-section Cantilever Fiber Bragg Grating Pressure Sensor

Design and Research on Variable Cross-section Cantilever Fiber Bragg Grating Pressure Sensor

Vibration analysis of nonlinear tapered functionally graded beams using point collocation method

Free transverse vibration of variable cross-section cantilever FG beams with nonlinear profiles is investigated in this paper. Four thickness functions, namely, linear, parabolic, sinusoidal, and exponential functions are assumed for variation of the cross-section of the beam. Linear and exponential grading rules for axially varying material properties are covered in this paper. The governing differential equation is solved using the weighted residual collocation method with the exact solution shape functions for the uniform beam as the trial functions. This choice for the trial functions showed an increase in the convergence rate. The Gauss–Legendre points are used as the collocation points to reduce the fluctuations in the convergence curve as usually encountered in the point collocation method. The effects of the taper parameter for all kinds of thickness functions on the natural frequencies are studied. The effects of various parameters, including taper parameter, profile, and grading function on the natural frequencies are investigated. Also, a series of finite element simulations are performed for comparison purposes. It is observed that the obtained results are in good agreement with the numerical simulations and available published data with vastly reduced computational cost as a result of using the collocation method.

Theoretical and Experimental Studies on MEMS Variable Cross-Section Cantilever Beam Based Piezoelectric Vibration Energy Harvester.

The piezoelectric vibration energy harvester (PVEH) based on the variable cross-section cantilever beam (VCSCB) structure has the advantages of uniform axial strain distribution and high output power density, so it has become a research hotspot of the PVEH. However, its electromechanical model needs to be further studied. In this paper, the bidirectional coupled distributed parameter electromechanical model of the MEMS VCSCB based PVEH is constructed, analytically solved, and verified, which laid an important theoretical foundation for structural design and optimization, performance improvement, and output prediction of the PVEH. Based on the constructed model, the output performances of five kinds of VCSCB based PVEHs with different cross-sectional shapes were compared and analyzed. The results show that the PVEH with the concave quadratic beam shape has the best output due to the uniform surface stress distribution. Additionally, the influence of the main structural parameters of the MEMS trapezoidal cantilever beam (TCB) based PVEH on the output performance of the device is theoretically analyzed. Finally, a prototype of the Aluminum Nitride (AlN) TCB based PVEH is designed and developed. The peak open-circuit voltage and normalized power density of the device can reach 5.64 V and 742 μW/cm3/g2, which is in good agreement with the theoretical model value. The prototype has wide application prospects in the power supply of the wireless sensor network node such as the structural health monitoring system and the Internet of Things.

Geometry and shape optimization of piezoelectric cantilever energy harvester using COMSOL multiphysics software

AbstractIn embedded systems that necessarily require a steady source of power and (or) attaches to a sensor(s), there are opportunities to mix small batteries to supply such power. The aim of this research is to optimize the geometry and shape of piezoelectric cantilevers to harvest more power. Several piezoelectric cantilever geometries with various shapes (rectangular, triangular, circular, and trapezoidal cross section) are tested in COMSOL multiphysics simulator to find the best geometry that provides the highest accomplishable power. The most efficient geometry was found to be conferred by the trapezoidal, cross section cantilever. Next, another improvement method was applied to maximize the harvested power of the cantilever by modifying the shape of the trapezoidal cantilever structure through increasing the number of its faces. The results demonstrated that the highest output power (36 mW) was produced by the four faces, trapezoidal cross section design of cantilever.

Nonlinear Dynamics and Fragmentation Mechanism of Coastal Rocks Impacted by Ocean Waves

Wang, T.; Li, X.-H., and Zhu, Z.-W., 2020. Nonlinear dynamics and fragmentation mechanism of coastal rocks impacted by ocean waves. In: Wan, Z. (ed.), Coordinated Sustainable Development in Coastal Areas: Environment and Economy. Journal of Coastal Research, Special Issue No. 109, pp. 185–190. Coconut Creek (Florida), ISSN 0749-0208.A variable cross-section cantilever beam is established to describe coastal rocks. A new differential term is developed to interpret the rock's stress-strain curves. Ocean waves are treated as stochastic incentives. The dynamic model of the beam is built up, and its nonlinear dynamic characteristics is obtained. The results show that the large periodic vibrations will cause fragmentation of coastal rocks. These results will be available for the fragmentation mechanism of coastal rocks impacted by ocean waves.

Rheological Effects in the Bridges Constructed with Cantilever Method

Abstract A characteristic feature of bridges made using cantilever concreting technology is their excessive deflections, which are a result of rheological processes in concrete and prestressing steel. These deflections can be caused by the destruction of the material, e.g. concrete cracking, as well as the changing of the static scheme of the bridge structure, such as the subsidence of supports. The final result of a structure’s operation is changes in its grade line, which in this paper are considered as the deflection line of a bridge’s span. The purpose of the paper is to determine the participation of a structure’s rotation over supports in the deformation of the span with the largest length. The authors proposed an algorithm for determining the deflection function and rotation angles, which were obtained on the basis of changes in the curvature of the beam. It is characterised by an accurate mapping of the rheological processes that occur in the bridge, which is calculated on the basis of the changes of the grade line obtained from geodetic measurements on site. The paper proposes a general geometric indicator of the box cross-section cantilever, which is calculated for the construction phase, and a different indicator for the operation phase. They can be used for comparative analyses of various bridges. The analysis of deflections in cantilever bridges during the operation phase of their longest spans indicates that there is a significant influence of the angles of rotation over the supports. In the paper, such a group of bridges is qualified as unstable, in which the static scheme changes from a determinate cantilever state (the construction phase) into a multi-span system with different span lengths (the operation phase).

DYNAMIC ANALYSIS OF UNIFORM AND NON-UNIFORM CROSS-SECTION CANTILEVER SANDWICH BEAMS

In this study, an analytical solution for dynamic analysis of uniform and non-uniform cross-section cantilever sandwich beam is presented. The sandwich beam was assumed to be an Euler-Bernoulli beam and formed with a thin core and two thin skin layers. So the shear deformations and rotational effects were neglected. The equivalent flexural rigidity was obtained for the entire sandwich structure. Some implementations for the solution method are given and the results are compared with numerical solutions. The usability of the Euler-Bernoulli Beam Theory for thin layered uniform or non-uniform sandwich beams is investigated. The solutions obtained from analytical and numerical solutions are in good agreement.

Performance comparison of Rayleigh and STW modes on quartz crystal for strain sensor application

In this study, we compare two kinds of strain sensors based on Rayleigh wave and surface transverse wave (STW) modes, respectively. First, we perform a strain-and-stress analysis using the finite element method, and we consider the contribution to a surface acoustic wave (SAW) velocity shift. Prior to fabrication, we use a coupling-of-modes model to simulate and optimize two-port SAW resonators for both modes. We use a network analyzer to measure and characterize the two devices. Further, we perform an experiment using a strain-testing system with a tapered cross-section cantilever beam. The experimental results show that the ratio of the frequency shift to the strain for the Rayleigh wave mode is −1.124 ppm/με in the parallel direction and 0.109 ppm/με in the perpendicular direction, while the corresponding values for the STW mode are 0.680 ppm/με and 0.189 ppm/με, respectively.

Wideband and 2D vibration energy harvester using multiple magnetoelectric transducers

This paper investigates a magnetoelectric (ME) vibration energy harvester that can scavenge energy in arbitrary directions in a plane as well as wide working bandwidth. In this harvester, a circular cross-section cantilever rod is adopted to extract the external vibration energy due to the capability of it\'s free end oscillating in arbitrary in-plane directions. And permanent magnets are fixed to the free end of the cantilever rod, causing it to experience a non-linear force as it moves with respect to stationary ME transducers and magnets. The magnetically coupled cantilever rod exhibits a nonlinear and two-mode motion, and responds to vibration over a much broader frequency range than a standard cantilever. The effects of the magnetic field distribution and the magnetic force on the harvester\'s voltage response are investigated with the aim to obtain the optimal vibration energy harvesting performances. A prototype harvester was fabricated and experimentally tested, and the experimental results verified that the harvester can extract energy from arbitrary in-plane directions, and had maximum bandwidth of 5.5 Hz, and output power of 0.13 mW at an acceleration of 0.6 g (with g=9.8 ms-2).

A Novel V-Shaped Cross Section Cantilever Sensor for Monitoring Concentrated Masses With Improved Detecting Sensitivity and Measuring Accuracy

Mass detection sensitivity and measuring accuracy of resonant mass sensors are mainly dependent on the analyte position, the resonant frequency, and the effective mass of the cantilever. For measuring concentrated masses or particles, a novel mass sensor incorporating V-shaped cross section cantilever was proposed by locating the analyte at predefined positions for both improving the mass detecting sensitivity and reducing the measuring deviation. The theoretical model for analyzing the mass detection sensitivity was established. With the same geometric dimension, the proposed sensor's sensitivities obtained theoretically and experimentally are 6.75×104 and 6.34×104 Hz/g, which are nearly 2.20 times as great as that of the custom made cantilever with a rectangular cross section. Thus, the feasibility of the proposed sensitivity improving method was adequately validated.

Worm Shaving Cutter Tooth Stress and Deformation Analysis

This paper discusses a new type of worm gear shaver shaving cutter tooth contact point during deformation force, and the establishment of the shaving force model, through the instantaneous cutting force to analyze the force deformation cutter shaving cutter tooth and precision of impact. And making use of a simplified model for variable cross-section cantilever, analyzing of tooth stiffness at any cross section, find the maximum amount of deformation of worm gear shaving cutters do theoretical foundation structure optimization.

Vibration-Based Damage Detection in Beams by Cooperative Coevolutionary Genetic Algorithm

Vibration-based damage detection, a nondestructive method, is based on the fact that vibration characteristics such as natural frequencies and mode shapes of structures are changed when the damage happens. This paper presents cooperative coevolutionary genetic algorithm (CCGA), which is capable for an optimization problem with a large number of decision variables, as the optimizer for the vibration-based damage detection in beams. In the CCGA, a minimized objective function is a numerical indicator of differences between vibration characteristics of the actual damage and those of the anticipated damage. The damage detection in a uniform cross-section cantilever beam, a uniform strength cantilever beam, and a uniform cross-section simply supported beam is used as the test problems. Random noise in the vibration characteristics is also considered in the damage detection. In the simulation analysis, the CCGA provides the superior solutions to those that use standard genetic algorithms presented in previous works, although it uses less numbers of the generated solutions in solution search. The simulation results reveal that the CCGA can efficiently identify the occurred damage in beams for all test problems including the damage detection in a beam with a large number of divided elements such as 300 elements.

A two-dimensional broadband vibration energy harvester using magnetoelectric transducer

In this study, a magnetoelectric vibration energy harvester was demonstrated, which aims at addressing the limitations of the existing approaches in single dimensional operation with narrow working bandwidth. A circular cross-section cantilever rod, not a conventional thin cantilever beam, was adopted to extract vibration energy in arbitrary in-plane motion directions. The magnetic interaction not only resulted in a nonlinear motion of the rod with increased frequency bandwidth, but also contributed to a multi-mode motion to exhibit double power peaks. In energy harvesting with in-plane directions, it showed a maximum bandwidth of 4.4 Hz and power of 0.59 mW, with acceleration of 0.6 g (with g = 9.8 m s−2).