Metal Cantilever Research Articles

Unshoring Process of a Temporary Pillar, in a Seventeen-Storey Building in Sant Adrià del Besós

In the new construction of a seventeen-storey building, a provisional prop of fourteen-meter height, horizontally braced on two intermediate levels, has been used. Despite the fact that structural logic suggests that it can be cut without having any added safety precautions, the structure of the building, made up of cores and reinforced concrete slabs working spatially, indicates that certain mechanisms be introduced so that, in the event that different and worse behaviors than expected are detected, the process can be stopped and the consequences of the new situation observed can be analyzed. For this purpose, two pairs of four metallic cantilevers were introduced at mid-height with four hydraulic pistons. In addition, the best position of a series of strain gauges as well as transducers were analyzed. At first, a load test was carried out to check that the brackets worked correctly. Once this step was verified, the abutment was cut, and the results were read. The results of stresses and deformations were compared with those expected, always being satisfactory. Finally, four provisional profiles were placed in case after a few days the structure suddenly gave way. The research focuses on obtaining an efficient control system and achieving total security throughout the process, with the comparison of the results strictly necessary for this case. Few resources were used so as not to make the work excessively expensive. We have found important divergences, on the side of security, between calculation and reality. We have also considered that the construction process has an impact on the final results. In the same way, the rigidity of the temporal abutment must be considered before the calculation. All these factors have generated a lower-than-expected deformation in an 8 m cantilever.

Experimental Investigation of Energy Harvesting by Employing Piezoelectric Element and Metallic Cantilever Beam

In this paper, in response to the worldwide energy crisis, a piezoelectric element (0.2*35*50) mounted on a host metallic cantilever beam (0.8*37*220) will be presented as a unique contribution to power generation via the micro-electrical mechanical system. It's made out of aluminium and low carbon steel, both of which have a Young modulus of elasticity of 6.8 and 196 GPa, respectively. In order to take advantage of the engine's vibration as an exciting external force to collect energy in the aforementioned piezoelectric device, the whole rig has been coupled to a diesel engine 5kw 3000 rpm (50 Hz). The average power generated by the aluminium beam was 943 microWatts, while the power generated by the low carbon steel beam was 335 microWatts, an increase of 256%. In addition, for both scenarios, (45) mm from the cantilever beam's fixed point was where the engaged piezoelectric element performed best. The used two metals have different stiffnesses, and this accounts for the obtained difference between the induced powers; increasing the stiffness will result in relatively more power created, and vice versa.

A Developed Jerk Sensor for Seismic Vibration Measurements: Modeling, Simulation and Experimental Verification

Acceleration-based sensors are widely used in indicating the severity of damage caused to structural buildings during dynamic events. The force rate of change is of interest when investigating the effect of seismic waves on structural elements, and hence the calculation of the jerk is necessary. For most sensors, the technique used for measuring the jerk (m/s3) is based on differentiating the time–acceleration signal. However, this technique is prone to errors especially in small amplitude and low frequency signals, and is deemed not suitable when online feedback is required. Here, we show that direct measurement of the jerk can be achieved using a metal cantilever and a gyroscope. In addition, we focus on the development of the jerk sensor for seismic vibrations. The adopted methodology optimized the dimensions of an austenitic stainless steel cantilever and enhanced the performance in terms of sensitivity and the jerk measurable range. We found, after several analytical and FE analyses, that an L-35 cantilever model with dimensions 35 × 20 × 0.5 (mm3) and a natural frequency of 139 (Hz) has a remarkable performance for seismic measurements. Our theoretical and experimental results show that the L-35 jerk sensor has a constant sensitivity value of 0.05 ((deg/s)/(G/s)) with ±2% error in the seismic frequency bandwidth of 0.1~40 (Hz) and for amplitudes in between 0.1 and 2 (G). Furthermore, the theoretical and experimental calibration curves show linear trends with a high correlation factor of 0.99 and 0.98, respectively. These findings demonstrate the enhanced sensitivity of the jerk sensor, which surpasses previously reported sensitivities in the literature.

Identification of crack location in metallic biomaterial cantilever beam subjected to moving load base on central difference approximation

Abstract If not detected early, the cracks in structural components may ultimately result in the failure of the structure. This issue becomes even more critical when the component under investigation is a prosthesis placed in the human body. This study presents a crack location identification method based on the time domain in a cantilever beam of metallic biomaterials (CBMB). The absolute difference between the central difference approximation of the root mean square (RMS) of displacement of points on the cracked and uncracked beams was applied as a cracked location indicator. Captured time-domain data (displacement) at each node of the cracked and uncracked beams were processed into a central difference approximation of the RMS of displacement. Then, the crack could be detected by a sudden change of the cracked location indicator. The feasibility and effectiveness of the proposed method were validated by numerical simulations. The finite-element simulation of a CBMB with a transverse notch was analyzed in the numerical study. The notch or crack was detected along the beam under a moving load at various locations. A set of simulation experiments and numerical calculations was performed to determine whether the proposed identification method would accurately detect the location of a crack in a cantilever beam under a moving load compared to the location found by an exact solution method. The results showed that the proposed method was not only as able as the analytical method but also robust against noise: it was able to detect a crack precisely under 5% noise.

Self-excited MEMS Oscillator using an Electrostatic Cantilever

In this paper, we propose a new use of an electrostatic MEMS cantilever structure as a voltage-controlled oscillator (VCO). A cantilever made of plated gold is accompanied with a drive electrode to turn on the contact switch upon voltage application. The electrical interconnection is arranged to discharge the cantilever when it is brought into contact with the switch, thereby promptly losing the electrostatic force and opening the contact switch again. As a result, the electrostatic cantilever spontaneously repeats the electrostatic pull-in and release at a frequency determined by the DC level of the applied voltage. A metallic cantilever of 500 μm long, 8 μm wide, and 12 μm thick is experimentally confirmed to work as an VCO in the frequency range between 8.4 kHz and 10.7 kHz controlled by the DC voltage between 160V and 180V.

Detection of Mechanical Deformation Induced by Ultrafast Laser Irradiation Upon a Metallic Cantilever

In this work, we systematically investigated the ultrafast optical properties of aluminum (Al) thin films on silicon cantilevers using a microscopic femtosecond optical pump-probe technique to explore the effect of light irradiation upon cantilevers while considering radiation pressure and photothermal effects. The ultrafast laser pulses used for the study were less than 30 fs in pulse duration and 830 nm in wavelength, and the photon energy (1.49 eV) of the light pulses is close to the interband transition threshold (ITT) of Al. Therefore, the change in ITT due to the strain of the cantilevers induced by the light irradiation is detected through the change in the transient reflectivity, which is dominated by the thermalized (Th) electron signal. We uncovered the position dependency of the transient reflectivity change and the Th electronic signal amplitude of the 100 nm-thick Al films on 160 $\mu$m, 200 $\mu$m and 240 $\mu$m-length cantilevers, and these results are in excellent agreement with two temperature model-based curve fits. Furthermore, to understand the effect of light irradiation, we derived equations for the position-dependent radiation pressure effect and the photothermal effect, and demonstrated that thermal expansion-induced changes in ITT dominate the position dependence of the signal intensity. Our findings offer avenues for exploring strain effects on ultrafast properties and applications for ultrafast scanning probe microscopy.

Acoustic emission applied to mode I fatigue damage monitoring of adhesively bonded joints

The use of adhesively bonded joints has increased considerably due to their lightweight, relevant strength-weight ratio and possibility to join multi-materials. Nevertheless, there are still some challenges in the application of this kind of joints in primary structures, such as guaranteeing their reliability during the components’ useful life. Structural health monitoring methods are suggested to ensure in-service safety and reliability of adhesive joints. The acoustic emission appears promising because it can detect the elastic waves produced within the material when it is under damage or straining. This research focuses on mode I fatigue damage monitoring metallic double cantilever beam adhesively bonded joints using the acoustic emission method. Digital image correlation and visual evaluation were applied during fatigue interruptions to track the crack-tip position within the adhesive and correlate them with the acoustic emission outcomes. The acoustic emission method is susceptible and different kinds of waves (background, friction and damage) can be easily assessed during the tests, producing an immense amount of data. So, unsupervised artificial neural networks for patterning recognition were proposed. Self-organising maps and k-means algorithms were used for data clustering and then classified regarding their sources. Finally, the acoustic emission results, digital image correlation and visual evaluations were compared.

A novel and cost-effective optical detection of high magnitude current and magnetic pulses through a metallic cantilever

We report a novel optical technique to measure short duration high magnitude current and magnetic pulses based on deflection of a macroscopic ferromagnetic cantilever. Deflection of the cantilever as a transducer takes place due to the attraction by an electromagnet. The reflected laser beam from a small thin mirror at tip of the cantilever is scanned over two spatially distinct photodetectors. Different high magnitude magnetic pulses are produced by discharging a capacitor bank through an inductive coil with a ferrite core. The response of the sensor is observed at different charging limits of the capacitor bank and spatial intervals between cantilever and inductive coil. A repeatable and linear response is detected by the devised sensors in the range 158.53–380.47 A current and 0.19–0.48 T magnetic field with sensitivity of 39.15 A kV−1 and 50.98 mT kV−1 for current and magnetic field amplitudes respectively in response to 2.5–6.0 kV charging of the capacitor bank. The proposed technique is remote, nondestructive, cost-effective and has a large dynamic range.

Bulk metallic glass cantilever beams: Outstanding at large-deflection deformation and their application in complaint mechanisms

Excellent combination of mechanical properties of bulk metallic glasses (BMGs) are a class of relatively young and promising candidate materials for compliant mechanisms (CMs), which are usually associated with the nonlinear large-deflection deformation. In this study, an effective design strategy was proposed to enhance the flexibility of BMG cantilever beam quantitatively, which by means of increasing the ratio of loading distance to beam thickness. Moreover, the accuracy of modulus of elasticity in bending, Eb, which measured by cantilever bending test was affected seriously by the support compliance of the fixed end, and the accurate Eb value of BMG beam can be attained after eliminating this influencing factor. The critical boundary condition of cantilever beams within the scope of small-deflection deformation was identified, which situates at non-dimensional deflection parameter, δy/L, is 0.2. Correspondingly, the critical loading distance-to-thickness ratios, (L/t)c, of cantilever beams within small-deflection deformation were derived for BMGs and conventional crystalline metals, which provide a criterion to predict the potential to achieving large-deflection deformation. It is noticed that by plotting the flexural stress-δy/L relations for BMG and several conventional crystalline metals used in CMs, the unique advantages of BMG cantilever beam in the aspect of achieving large-deflection deformation and enduring higher flexural stress can be reflected more intuitively. These advantages of BMG cantilever beam are well suitable for CMs which designed to have a small footprint and requirement of large-deflection motions, such as in the fields of microelectromechanical systems (MEMS) and biomedicines.

Sound Wave Propagation from Underdamped Free Oscillation of Metallic Cantilever Beams

We describe here a low-cost experiment for introductory physics students where they compare the physical properties of aluminum and steel by means of cantilever oscillations. This, in turn, allows the students to improve their physical intuition about these materials. Further, the students can apply their physics and mathematics knowledge and skills to create an experiment-based physical model.

Opto-mechanical magnetometer based on laser speckle correlation

Magnetic field sensing plays vital role in vast range of areas such as navigation, military, and biomedical sciences. In recent times, optical sensors have made great advances, resulting in the development of magnetic field sensors based on optical principles due to their non-susceptibility to electromagnetic interference. Here, a simple and inexpensive approach for sensing magnetic field, that converts the magnetic field into a mechanical translation (of the sensing element) and then change into optical signals is presented. These optical signals are speckle patterns generated using a laser beam reflected off an optically rough metal cantilever which is exposed to the magnetic field. Magnetic field is quantified by measuring the changes in the speckle pattern using the intensity correlation technique. The approach can measure the static and time varying magnetic fields. The proposed system has a resolution of 2.2 μT and can measure magnetic fields with less than a 2% error.

Evaluation of Angle-of-Incidence Characteristics of Plasmonic Photodetector Based on Strain Measurement of Metal Cantilever

This paper reports a measurement system for angle-of-incidence characteristics of a plasmonic photodetector using a strain gauge on a metal cantilever. The photodetector is installed on the metal cantilever equipped with the strain gauge at the root of the cantilever. By deforming the cantilever, the angle of incidence of the photodetector was scanned. This angle of incidence was calculated by measuring the strain on the metal cantilever. The photocurrent signal from the photodetector and the strain signal from the strain gauge were simultaneously measured using an oscilloscope while the cantilever was being deformed. The simultaneous measurement of the two signals produced similar result to the one obtained by a conventional measurement using a rotating stage, indicating that the proposed structure is capable of simultaneous measurement of photocurrent and angle of incidence.

Modeling and approximate analytical solution of nonlinear behaviors for a self-excited electrostatic actuator

Analytical modeling and solution of nonlinear vibration behaviors are vitally important for the optimization of vibratory actuators. In this paper, the nonlinear vibration characteristics of a self-excited electrostatic actuator are investigated. The actuator consists of two plate electrodes and a metal cantilever, which is fixed on an isolated insulating base and placed in the middle of the electrodes. When a DC voltage is applied to the electrodes, the cantilever is excited into reciprocating vibration autonomously and collides with the electrodes with strongly nonlinear features. During modeling, the collision is considered as a transient process and only the velocities of the cantilever before and after the collisions are concerned. By using the phase plane method, the limit cycle and boundary conditions of the self-excited oscillation of the cantilever are obtained and the strongly nonlinear problem of the entire system is converted into a weakly nonlinear problem of the cantilever moving between the electrodes. The nonlinear equations are then solved by using the averaging method, and the approximate analytical results demonstrate good consistency with the numerical and experimental results. Besides, the approximate analytical results are also adopted in the optimization of the actuator for enhanced power density and efficiency. The modeling and solution methods provide a framework for further optimization of the electrostatic actuator in the application field of centimeter-scale robotics.

Bulk Metallic Glass Cantilever Beams: Outstanding at Large-Deflection Deformation and Their Application in Complaint Mechanisms

Bulk Metallic Glass Cantilever Beams: Outstanding at Large-Deflection Deformation and Their Application in Complaint Mechanisms

Direct Measurement of Contraction Force in Cardiac Tissue Construct in 2D-Plane Using Dual Axis Cantilever Sensor

In this work, we present a technique for a dual axis contraction force measurement of human cell based cardiac tissue constructs. The cardiac tissue constructs consist of a vascular-like network and induced pluripotent stem cell derived cardiomyocytes. Before the force measurements, the cardiac tissue constructs were detached from the culture substrate to allow less restricted contraction. The in-house prepared force sensors are composed of piezoelectric sensing elements and a metallic cantilever for contacting the cardiac tissue constructs. A dedicated measurement platform with embedded signal processing software is used for data acquisition from the sensors. Dual axis force sensor results are compared with our previously developed single axis force sensor technique. Additionally, the proposed dual axis force measurement system can measure two-dimensional displacement trajectories of the cantilever probe tip. We propose a pattern matching method for classification of the captured cardiac contraction cycle patterns and for extracting anomalies in the measured cycles. We demonstrate both single and dual axis peak cardiac construct contraction force measurement results in the ranges of 3.4 - $6.7~\mu \text{N}$ and 9.4 - $10.6~\mu \text{N}$ , respectively. The relative standard deviation of the peak contraction force results varied between 1.0 and 4.1% in eight captured 60 second measurement sequences.

A structural impedance measurement method by using polyvinylidene fluoride as actuator and sensor.

Polyvinylidene fluoride (PVDF) patches have extremely small Young's modulus and piezoelectric coefficients. They are usually chosen as sensors in the structural impedance measurement for health monitoring. In this paper, a novel method is demonstrated for structural impedance measurement using PVDF patches as actuators and sensors. The impedance of the host structure is decoupled from the capacitance impedance of the piezoelectric transducer by using one of the patches as the actuator and the other as the sensor. Phase sensitive detection is then adopted to recover weak impedance signals in the experimental studies. This technique enables measurement of the resonant frequencies and further identification of the health condition of the host structure. The superiority of this method is illustrated theoretically comparing to the conventional impedance-base method. A prototype consisting of a metal cantilever with two PVDF patches is fabricated and tested. Experimental results demonstrate the effectiveness of the proposed method in the detection of the resonance of the substrate precisely with respect to FEM simulation and the results under base-movement excitations. Moreover, mass change induced impedance shifting can be obtained.

Multiple-Scale Analysis of a Tunable Bi-Stable Piezoelectric Energy Harvester

Abstract This paper presents the theoretical modeling and multiple-scale analysis of a novel piezoelectric energy harvester composed of a metal cantilever beam, piezoelectric films, and an axial preload spring at the moveable end. The harvester experiences mono- and bi-stable regimes as the stiffness of preload spring increases. The governing equations are derived with two high-order coupling terms induced by the axial motion. The literature shows that these high-order coupling terms lead to tedious calculations in the stability analysis of solutions. This work introduces an analytical strategy and the implementation of the multiple-scale method for the harvester in either the mono- or bi-stable status. Numerical simulations are performed to verify the analytical solutions. The influence of the electrical resistance, excitation level, and the spring pre-deformation on the voltage outputs and dynamics are investigated. The spring pre-deformation has a slight influence on the energy harvesting performance of the mono-stable system, but a large effect on that of the bi-stable system.

Experimental Study on Determining the Elastic Modulus of Metal Materials by Deflection Method

This paper studies the method of measuring the elastic modulus of metal materials by the deflection method. The relationship between the deflection and the load and the elastic modulus of the metal cantilever beam is established, so that the elastic modulus of the cantilever beam is indirectly measured. The experiment requires that the deformation of the material is within the elastic range. Furthermore, the deflection method is adopted. Not only the method is simple and does not require expensive equipment, but also the average value of multiple sets of experimental results is used as the modulus of elasticity of the material during measurement, which ensures a certain accuracy.

Design of a snake-like swimming mechanism based on wave propagation in a vibrating cantilever beam

In this study a locomotion mechanism which is similar to snake and fish swimming has been developed by using the natural vibration behavior of a simple cantilever beam (thin metal film). The swimming locomotion of the mechanism that is driven by wave propagation motion of the metal film has been confirmed by experiments. A metal cantilever beam (metal film), which is forced to vibrate at natural frequency by using a simple micro vibration motor, generates a propelling force, such as a fish fin that fluctuates in the liquid. And in this way, the swimming locomotion is provided in the specified directions depending on the orientation of the beam. In this way, it is aimed to develop an innovative and low energy consumption locomotion mechanism. The effects of design variables such as beam length and width, which effect the beam's natural frequency and locomotion performance, have been experimentally investigated on various test prototypes. The direction control and maneuverability of the robot can be improved by adding a second cantilever beam. Analytical calculations and experimental results showed the applicability of the proposed approach and the design. The locomotion mechanism introduced in the study has the potential to be used in micro robotic applications with its maneuverability and low energy consumption features.

Investigation of the size effect on the resonant behavior of mesoscale cantilever beams

A vibrational resonant cantilever beam device is a type of tactile vision substitution device for the visually impaired that has the potential to achieve a high resolution in a small space. In order to realize a device of this type, it is necessary to accurately model the resonant behavior of the mesoscale (0.1–1.0 mm) metal cantilever beams of which the device is composed. Specifically, the natural frequencies and damping ratios of these beams must be analytically modeled in order to design beam dimensions for the device. In this paper, the resonant frequencies and damping ratios of a set of A2 tool-steel mesoscale cantilever beams are obtained using three different methods: calculation based on a mass–spring–damper model of the beams; a forced response experiment; and a free response experiment. The results are compared, and the size effect on stiffness and elastic modulus is investigated. Based on the modified couple stress theory, the length scale parameter is calculated. The damping ratio difference depending on the dimension of material in the mesoscale is also investigated.