Laser Displacement Meter Research Articles

Experimental and numerical studies on corrosion-resistant aluminium foam sandwich panel subject to low-velocity impact

Aluminium foam sandwich panels (AFSPs) have a high impact resistance and are suitable for a wide range of engineering applications. To improve corrosion resistance, this paper proposes an anti-corrosion sandwich panel with stainless steel as the upper sheet. Drop hammer impact tests were performed on a total of ten AFSPs to investigate their dynamic response and failure patterns. To assess the deformation performance of AFSPs, a laser displacement meter was used to obtain the bottom centre displacement. The effects of the impact energy and the thickness of each component of AFSPs on the peak impact force and deformation performance were studied. Test results showed that the thickness of each component had notable effects on the impactor and bottom displacements. In addition, the effect of the unit mass of the components in AFSPs on decreasing the bottom displacement was discussed. Compared to increasing the aluminium foam and lower sheet thicknesses, increasing the upper sheet thickness was more effective in decreasing the bottom displacement. A finite element model of AFSPs was developed to conduct parameter analysis, indicating that impactors with larger diameters resulted in higher peak forces and reduced deformation of AFSPs.

A novel ultrasonic method for measuring minute sinusoidal displacement by network analyzer.

We developed a method for generating continuous sinusoidal displacements of an object to estimate viscoelastic parameters. However, the amplitude of the displacement caused by the ultrasonic excitation force under safe guidelines was small (a few micrometers), and it was difficult to stably measure the displacement. Therefore, to stably measure the amplitude of sinusoidal displacement as small as the order of micrometers, we proposed a novel method using a network analyzer. Ultrasonic waves were irradiated using an ultrasonic transducer on an object vibrating sinusoidally. The S parameter of the first reflected wave received from the surface of the object was measured using a network analyzer. The S parameter and the inverse Fourier transform were formulated theoretically, and the amplitude of the sinusoidal displacement of the object was estimated from the amplitude characteristics of the inverse Fourier-transformed signal. The proposed method was applied to measure sinusoidal displacements on the order of micrometers from 10 to 300Hz on an object using a water tank experiment. The obtained sinusoidal displacement agreed well with the reference values measured using a laser displacement meter. The proposed method can accurately measure minute sinusoidal displacements that occur on an object.

The effect of carrier locking position on the dynamic characteristics of gapless miniature linear guideway

The analysis of the load position of the miniature linear guideway is very important for the dynamic friction characteristics of the linear motion equipment. In this paper, a miniature guideway dynamic friction coefficient tester will be designed. And the effect of load position, movement speed, and load on the friction force of linear guideway will be investigated according to the gapless. The experimental results show that the friction force will be dependent on the load position, load, and movement speed. Among them, the lowest frictional load position can be obtained at any speed of movement and load condition, which occurs at the central load position. The main reason for this is that the effect of the moment is minimum. On the same load position and movement speed, then load is proportional to friction. In the case of fixed load and load position, the effect of velocity on friction is positively correlated in the longitudinal offset position. The frictional force is aggravated by the unevenly distributed pressure on the inner ball due to the moment generated by the slider. At the same time, by observing the loading and the inclination angle of the carrier in the experiment with the laser displacement meter, it can be found that the inclination angle also tends to increase when the load increases.

Thin Glass Micro Force Plate Supported by Planar Spiral Springs for Measuring Minute Forces.

Microforce plates are indispensable tools for quantitatively evaluating the behavior of small objects such as tiny insects or microdroplets. The two main measurement principles for microforce plates are: the formation of strain gauges on the beam that supports the plate and the measurement of the deformation of the plate using an external displacement meter. The latter method is characterized by its ease of fabrication and durability as strain concentration is not required. To enhance the sensitivity of the latter type of force plates with a planar structure, thinner plates are generally desired. However, brittle material force plates that are both thin and large and can be fabricated easily have not yet been developed. In this study, a force plate consisting of a thin glass plate with a planar spiral spring structure and a laser displacement meter placed under the plate center is proposed. The plate deforms downward when a force is exerted vertically on its surface, resulting in the determination of the applied force using Hooke's law. The force plate structure is easily fabricated by laser processing combined with the microelectromechanical system (MEMS) process. The fabricated force plate has a radius and thickness of 10 mm and 25 µm, respectively, with four supporting spiral beams of sub-millimeter width. A fabricated force plate featuring a sub-N/m spring constant achieves a resolution of approximately 0.01 µN.

Forward and inverse analysis of transient responses for a cantilevered rectangular plate under normal and oblique impact loadings

This study investigates the transient responses of a cantilevered rectangular aluminum plate under normal and oblique impact loadings. The transient displacement and strain histories of the aluminum plate are forward calculated as a superposition of the normal modes using first-order shear deformation plate theory and the spectral collocation method considering both in-plane and out-of-plane dominant vibrations. A laser displacement meter and strain gauges are used to measure the displacement and strain histories of the same aluminum plate when subjected to normal and oblique loadings. Subsequently, frequency-dependent damping ratios are obtained from the associated wavelet spectrograms. The measured histories correlate well with those estimated using the theoretical analysis considering the damping ratios. Additionally, the inverse problem of determining the impact force history from the transient response is investigated. First, the transfer function between the impact force and measured response is derived using a theoretical analysis developed in the time domain. Subsequently, a wavelet deconvolution method is applied to reconstruct the impact force using a discrete wavelet transform with different scale and shift components. Thus, the impact force is obtained by reconstructing the wavelet expansion coefficients using these components, thereby demonstrating the validity of the wavelet deconvolution technique utilizing the theoretical transfer function.

The Influence of Chamfered and Rounded Corners on Vortex-Induced Vibration of Super-Tall Buildings

In order to study the influence of chamfered and rounded corners on vortex-induced vibration of super-tall buildings, a series of multi-degree-of-freedom (MDOF, in short) aeroelastic models were made, including chamfered-corner models with chamfer ratios of 0%, 2.5%, 5.0%, 7.5%, and 12.5%, and rounded-corner models with rounded ratios of 0%, 12.5%, 15%, and 17.5%. The crosswind displacement response of each aeroelastic model was measured by a laser displacement meter in a wind tunnel. The test results indicate that the crosswind displacement response is significantly reduced when the chamfer ratio increases to 5% or the rounded ratio increases to 12.5%; in particular, the vortex-induced vibration (VIV, in short) response can be reduced by more than 60%, which indicates that the chamfered corner and rounded corner play a good role in restraining the VIV of super high-rise buildings. When the reduced wind speed is small, the reduction of the crosswind response of chamfered and rounded models is mainly caused by the reduction of wind load; when the reduced wind speed approaches the VIV wind speed, the negative aerodynamic damping phenomenon of the model with a proper chamfer ratio and rounded ratio disappears, which shows that the VIV is suppressed not only because the cut corner reduces the wind load but also because the cut corner weakens the aeroelastic effect. Generally speaking, a chamfer ratio of about 7.5% and rounded ratio of about 15% can achieve a good reduction effect on the VIV of super high-rise buildings.

Transfer and inkjet printing of gold thin film and graphene oxide nanoparticles for micro-oscillators

This study presents the results of micro-oscillator fabrication using the transfer printing (TP) of gold (Au) thin films and inkjet printing of graphene oxide (GO) nanoparticles. The Au thin films are formed into a double-supported microbeam to function as a micro-oscillator on a polymer substrate. The Au microbeams have a thickness of 300 nm and a length of 250 or 300 μm. To improve adhesion strength between the substrate and the Au thin film, the Au thin film is transferred and printed onto a substrate pre-coated with a 30-nm-thick Au surface via atomic diffusion bonding. Furthermore, GO nanoparticles are deposited on the transfer-printed Au thin film and the convex part of the stamp using inkjet printing to enhance the mechanical properties of the micro-oscillator. The former deposition forms a double-layered beam of Au and GO. The Au/GO/Au-layered microbeam is fabricated on a pre-structured substrate by TP after another Au thin film is then deposited on this GO/Au surface. These micro-oscillators can be driven by electrostatic force at less than 10 kHz with 90–210 V of applied voltage, while the deflection of the micro-oscillator is measured by a laser displacement meter. The Au micro-oscillators have a damping ratio of 0.166, and a resonance frequency of 0.28 kHz. This resonance frequency is smaller than that estimated by finite element method analysis. This difference in resonance frequency is attributed to the Young's modulus of the Au thin film and structural defects due to van der Waal bonding. The modulus of the laminated thin film of Au and GO nanoparticles is higher than that of the Au thin film.

A Polyimide Film-Based Simple Force Plate for Measuring the Body Mass of Tiny Insects

Insects exhibit excellent maneuvers such as running and flying despite their small bodies; therefore, their locomotion mechanism is expected to provide a design guideline for micromachines. Numerical simulations have been performed to elucidate this mechanism, whereby it is important to develop a model that is physically identical to the target insect's parts to reproduce kinematic dynamics. In particular, in flight, the shape and mass of wings, which flap at high frequencies, are significant parameters. However, small insects such as fruit flies have small, thin, and light wings; thus, their mass cannot be easily measured. In this study, we proposed a high-resolution and simple force plate to measure the mass of each part of a tiny insect. The device consists of a circular plate supported by flat spiral springs made of polyimide film, and a laser displacement meter that detects the displacement of the center of the plate. The simple plate fabrication process requires only a couple of minutes. A fabricated force plate with a sub-N/m spring constant achieved a resolution of less than 2 µg. As a demonstration, the wing mass of the fruit flies was measured. The experimental results suggest that the wings accounted for approximately 0.4% of the body mass.

Configuration and Performance Test of GNSS-IMU Sensor Fusion Module for Structural Displacement Measurement

Detecting the displacement of a structure by external forces in advance is very important in monitoring the health of the structure. In this study, a kind of sensor fusion technique that combines low-cost GNSS and IMU for structural displacement measurement was established. In addition, a data acquisition program that can secure the synchronous measurement between sensors was created. In order to evaluate the performance of this measurement module, a model experiment gauging the true value by the laser displacement meter was performed, and the results of GNSS single positioning, VRS positioning, precision single positioning (PPP), and sensor merging positioning were compared and analyzed. As a result, it was found that the PPP positioning did not capture the vibration of the structure at all regardless of the waiting time within the excitation condition of the model structure. On the other hand, GNSS single positioning was able to obtain similar results to true values and VRS positioning by pre-processing with an appropriate high-pass filter and the sensor fusion technique.

Measurement method of a microspring-supported force plate with an external laser displacement meter

Ground reaction force (GRF) is a significant factor for the evaluation of animal locomotion. Recently, micro force plates have been implemented as a GRF measurement method for tiny insects. Previous micro force plates were highly sensitive, but fragile and laborious to fabricate, because of the use of strain-sensing elements. Here, we applied high-resolution 3D printing and a noncontact displacement meter to a micro force plate for a fruit fly. 3D printing is suitable for easier, reproducible, and complex three-dimensional fabrication so that a force plate structure, which consists of a plate and four supporting 3D microsprings, is developed as an integrated unit. By detecting the displacement of the plate centre externally, when a fruit fly lands on the plate surface, the vertical GRF of the whole device is calculated via the spring constant. The force plate is sufficiently tough due to the supporting 3D microsprings. The spring constant of the microspring is designed to be approximately 5.98 N m−1, which enables a high-resolution external laser displacement meter to realize a force resolution of less than 1/50 of the body weight of a fruit fly. Providing that the four springs have the same spring constant and the displacement meter aligns at the plate centre, in principle, there is no positional error when converting from displacement to force. However, fabrication error does lead to spring constant differences. Here, we theoretically and experimentally determined the measurement point of the displacement sensor where the positional error caused by the difference in the spring constant of the four microsprings is compensated for. It was confirmed in the experiment that the calibration process improved the position error to be within ±1.5%. Finally, we demonstrated the GRF measurement of a fruit fly. The average GRF was 6.5 μN, which was equal to the weight of a fruit fly. Our proposed device can help evaluate the biomechanics of tiny insects.

Method of estimating the lateral vibration of an elevator rope from the vertical vibration of a compensating sheave

ABSTRACT Observing the vibration of the elevator ropes in an elevator shaft is a difficult task. Although several methods of observing the displacement using image processing or laser displacement meters and then estimating the vibration through an observer or a Kalman filter have been developed, it is difficult to install sensors because of the movement of the elevator car and the thinness of the rope as an observation target. Therefore, in this study, we focus on a pulley called a compensating sheave that does not change its lateral position as the car and ropes move. The horizontal vibration of the ropes causes the compensating sheave to vibrate in the vertical direction. A method of estimating the horizontal vibration from this vertical vibration using arc length calculations and a short-time fast Fourier transform is proposed. First, the vertical vibration of the compensating sheave is distributed to the various mode responses based on the predominant frequency of the vertical vibration. The mode-decomposed vertical vibration is then converted into a horizontal mode response using an arc length relational expression. Analysis of seismic response data confirms that the proposed method can estimate the 1st, 2nd, and 3rd horizontal mode responses from the vertical vibration.

The Research on the Damping of Prestressed Membrane Structure Subjected to the Impact Load

The damping ratio plays a main role in the vibration of membrane structures. In order to study the damping force of air application to membrane structures, this present paper investigated the vibration response of a membrane structure subjected to impact loads. Eight experiments with the application of different tension forces to a tension membrane structure were conducted, and the impact load was simulated using a rigid bullet with a certain velocity. The displacement data were obtained using a laser displacement meter. FEM was used to simulate the vibration, and the results had good agreement. The results show that the effect of air applied to a prestressed membrane was equivalent to viscous damping, and the damping force was determined using the air. The damping ratio was proportional to the density of the air over the density of the membrane. The parameter of the coefficient could be determined using the geometry of the structure.

High-speed multi-camera 3D DIC measurement of the deformation of cassette structure with large shaking table

Vision-based deformation measurement methods have been proposed to overcome the disadvantages of laborious, time-consuming measurement data that are difficult to accurately obtain using contact sensors in three directions. However, such methods remain a challenge for large-scale applications owing to difficulties in full-field imaging, stereo calibration, and measurement resolution, among other factors. To the best of our knowledge, there are no reports on the three-dimensional (3D) full-field measurement of a large shaking table structure with multiple cameras. In this paper, a multi-camera 3D DIC method using four high-speed cameras to measure the multi-layer structure model in a shaking table is proposed. To calibrate the stereo cameras with a large field of view, a speckle-based calibration method and a coordinate system unification method are proposed. The implementation of the proposed method is illustrated with a shaking table test for a 1/8 scaled 15-story high-rise cassette concrete structure with several different intensity levels of ground motions. The results of displacement, velocity, and acceleration of the structure measured using the proposed method correspond well with those of a laser displacement meter and accelerometer. The experiment results show that this method can guarantee full-field measurements in the range of tens of square meters and realize a sub-millimeter displacement measurement accuracy. They also indicate that the proposed multi-camera 3D DIC method has high potential for understanding the failure mechanism of structures and improving the structural design.

Possibility of the existence of a topological defect in dynamic deformation of the free-standing ultrathin silicon wafer during MeV ion irradiation

We study the ion-irradiation-induced deformation of free-standing ultrathin Si wafers with a thickness of 8 μm. The time-response spectrum of the deformation was measured using a laser displacement meter with a time resolution of 1 ms. The results showed that the deformation appeared during irradiation and disappeared after irradiation. The deformation was composed of a fast deformation with a millisecond time constant and a slow deformation with a second time constant. We performed a model calculation to identify the deformation mechanisms. We found that the fast deformation originated from expansion or shrinkage of crystal lattice caused by beam heating and deduced that the slow deformation resulted from the topological defect formation in Si crystals. The relaxation time of the slow deformation is related to the coordination number of disappeared topological defects. In this experiment, we conclude that the deformation of Si crystals maintains reversible behavior in the formation of topological defects up to the coordination number 5.

Structural components with sensing capability of three-dimensional temperature distribution for thermal deformation prediction

Approximately 70% of the errors in machining processes are attributed to thermal deformation. In this regard, the compensation scheme is effective in canceling out thermal deformation and maintaining good machining quality, but it requires a fine measurement of the temperature distribution of the machine structure. Thus, in this study, a structural component for machine tools with a large-scale array of temperature sensors interconnected in series (LATSIS) is proposed. The three-dimensional temperature distribution is obtained by the embedded LATSIS, which potentially realizes thermal error compensation with excellent accuracy. The main purpose of this research is to evaluate the potential superiority of the proposed composite material compared to conventional materials, such as damping properties, weight, and thermal compensation capability. Moreover, a block-shaped structural component made of polymer concrete (PC) embedded in a steel shell was designed. The LATSIS was also embedded in the PC. For comparison, another structure was designed with cast iron to have a similar rigidity and fit in a design space similar to that of the proposed component. Intermittent heating experiments were conducted using components fixed as a cantilever. The temperature and displacement changes at the edges of each cantilever were collected using LATSIS and laser displacement meters, respectively. By interpolating the temperature data and obtaining the temperature distributions, the thermal deformations using thermal finite element method analysis were predicted. The results indicated that the thermal deformation could be predicted more accurately in the structure made with the proposed composite material compared to that made of cast iron.

Gas-liquid phase-detection and liquid film thickness measurement on a sprayed surface with a two-fluid jet using a fiber-optic probe and laser displacement sensor

The two-fluid jet method, which impacted droplets accelerated by a high-speed air stream, is widely used in cleaning the semiconductor manufacturing process. A wafer must always be covered with a liquid film during the cleaning process because local drying may cause some defects. However, the liquid film thickness formed by the high-speed airflow and droplets and whether a liquid film exists on the impingement surface have not been investigated. In this study, we tried to measure the liquid film thickness using an optical fiber probe and a laser displacement meter. We discuss the return light signal from the optical fiber probe installed on the surface irradiating the two-fluid jet.

Two-wave laser displacement meter

A two-wave laser displacement meter based on Michelson interferometer has been developed for measurements at an unknown temperature profile at the measurement trace. The requirements for meteorological parameters support during displacement measurements using the offered laser interferometer are less strict compared to using an one-wave interferometer. The article describes the optical schematic of the device. The results for the measurements of the developed laser interferometer for realization of the displacement unit within the limits of 60 m are presented. The weather condition influence on measurements was estimated. The application of pseudorandom displacement of the interferometer’s reference arm with accumulation made possible the reflector position resolution down to 0.01 μm the stoped-displacement mode, and down to 0.05 μm at the displacement mode. It was shown that such resolution allows to measure displacements at trace up to 60 m with inaccuracies less than 10 μm at the temperature profile amplitude up to 1 °C.

Dynamic Response Measurement of Elastic Structures Through Smart Digital Image Correlation Method and Calculation

Based on the proper improvement and development of the basic principle of digital image correlation method, a 3D-DIC measurement system is built. Its measurement principle and application process can be divided into four steps: camera calibration, image acquisition, image matching and three-dimensional reconstruction. The measurement system can realize non-contact and full-field measurement and has the advantages of not being affected by the test environment, not imposing additional mass on the test model, and high signal-to-noise ratio of the measured data. Taking the elastic plate model as an example, the accuracy and reliability of the measurement system in the measurement of static and dynamic displacement response are verified by using the measurement results of laser displacement meter as a reference. In addition, the tensile strain of the projectile aluminum alloy tail model and the ground mode of the elastic plate are tested to further verify the practicability of the test system.

Compliance method to measure crack length and crack closure for automated fatigue crack propagation test of nanocrystalline nickel film

Experimental techniques for measuring the crack length and crack closure behavior of single edge crack tension [SE(T)] specimens with fixed ends were developed with compliance method employing a high-resolution laser displacement meter together with data processing for noise elimination. Then, an automatic force-shedding fatigue crack propagation test system was developed. Using this system, we measured the crack length and crack closure behavior of thin films with a thickness of 5 or 10 µm and width of 10 mm, with which the accuracy of crack length measurement was better than 0.46 mm. The crack closure behavior could also be identified by the compliance method. The relationship between the crack propagation rate da/dN and the stress intensity factor range ΔK for nanocrystalline (NC) and ultrafine-grained (UFG) thin film was independent of the force ratio, and the relationship for the 10 µm-thick film was almost identical to that for the 5 µm thick film. No crack closure was observed in the UFG and NC thin films, whereas it occurred in the medium-size-grained (MG) thin film. The da/dN–ΔKeff relationships for thin films were independent of the force ratio and film thickness. In the Paris law region, da/dN for the MG film was higher than that for an MG plate at comparable ΔKeff, showing that crack closure could not account for the thickness effect. However, no difference in ΔKeff,th was observed for both the MG film and the MG plate. In the Paris law region (Region B), no effect of grain size on the da/dN–ΔK relationship was observed for the 10-µm-thick film; however, the crack propagation rate was higher for a film with smaller grain size and thickness from 100 to 180 µm. For NC and UFG films, the crack propagation rate of the 100-µm-thick film was higher than that of the 10-µm-thick film, but it was almost identical for MG films; however, the rate for a thin film was higher than that for a bulk plate. The threshold stress intensity factor range was always lower for a film with smaller grain size.

Application of laser displacement measurement system in thermal test of aircraft

At present, there is no research on nanosecond displacement measurement technology for spacecraft thermal test in China. Firstly, the principle of laser displacement sensor measurement is introduced. A system of hardware and software design and implementation was designed. Finally, a set of test system is built to verify the application of laser displacement meter in the spacecraft vacuum thermal test displacement measurement system. The experimental results and data analysis show that the laser displacement meter can meet the nanosecond displacement measurement requirements of spacecraft in vacuum and low temperature environment.