Non-contact Measurement Technique Research Articles

Prototype of low melt-point liquid metal performance of Lorentz force particle analyzer

Lorentz force particle analyzer (LFPA) is a non-contact electromagnetic measurement technique for the cleanliness inspection of liquid metal. Based on its principle, an optimized prototype of micro-particle measurement device is designed and built. Inclusion particles of different sizes in millimeter and submillimeter in liquid metal are inspected by this device at room temperature. The characteristics and formation mechanisms of typical inclusion particles pulse signal and laser path signal are compared and discussed. The wavelet decomposition method is used to denoise the original signal, and the desired signal is extracted and sorted out. Results show that LFPA is suitable for the measurement of inclusion particles in liquid metal.

Development of an Optical System for Non-Contact Type Measurement of Heart Rate and Heart Rate Variability

Self-mixing optical coherent detection is a non-contact measurement technique which provides accurate information about the vibration frequency of any test subject. In this research, novel designs of optical homodyne and heterodyne detection techniques are explained. Homodyne and heterodyne setups are used for measuring the frequency of the modulated optical signal. This technique works on the principle of the optical interferometer, which provides a coherent detection of two self-mixing beams. In the optical homodyne technique, one of the two beams receives direct modulation from the vibration frequency of the test subject. In the optical heterodyne detection technique, one of the two optical beams is subjected to modulation by an acousto-optics modulator before becoming further modulated by the vibration frequency of the test subject. These two optical signals form an interference pattern that contains the information of the vibration frequency. The measurement of cardiovascular signals, such as heart rate and heart rate variability, are performed with both homodyne and heterodyne techniques. The optical coherent detection technique provides a high accuracy for the measurement of heart period and heart rate variability. The vibrocardiogram output obtained from both techniques are compared for different heart rate values. Results obtained from both optical homodyne and heterodyne detection techniques are compared and found to be within 1% of deviation value. The results obtained from both the optical techniques have a deviation of less than 1 beat per minute from their corresponding ECG values.

Contact and Non-contact Heart Beat Rate Measurement Techniques: Challenges and Issues

The heart is the most important organ in the human body as it circulates the blood throughout the body through blood vessels. In the human circulatory system, the heart beats according to the body’s physical needs. Therefore, the physical condition of a person can be determined by observing the heartbeat rate (HBR). There are plenty of methods that can be used to measure the HBR. Among the methods, photoplethysmography (PPG), electrocardiogram (ECG) and the oscillometric method are the standard methods utilised in medical institutes for continuous measurement of the HBR of a patient. Out of these three methods, PPG is the only method which has evolved to a non-contact imaging-based method from the conventional contact sensory based method. The incentive for developing the non-contact-based imaging PPG method in measuring the HBR provides the advantage of excluding the direct contact of sensors on specific body parts. This brings huge improvements to remote monitoring of healthcare especially for the purpose of social distancing. Moreover, the rapid progression of technology (particularly the interactive electronic gadgets advancement) also motivates researchers and engineers to create a mobile application using the PPG imaging method, which is feasible in measuring the HBR. Hence, this study seeks to review and present the fundamental concept, the present research and the evolution of the aforementioned methods in measuring the HBR.

Stability and failure analysis of compressed thin-walled composite structures with central cut-out, using three advanced independent damage models

In this paper, the phenomenon of stability and failure of axially compressed thin-walled structures with central cut-out, made of composite materials, were investigated. The tested structures were made of carbon-epoxy composite material, using autoclave technique. Within the framework of the studies, experimental tests on actual constructions were carried out, as well as advanced numerical simulations using the finite element method in the ABAQUS® software. The process of axial compression of thin-walled composite structures was carried out in the full range of load, up to total failure. During the experimental tests, post-critical equilibrium paths were recorded, using the universal testing machine - Instron 4485. Additionally, acoustic emission signals were recorded using the AMSY-5 device, and the level of deformation was tested, using the non-contact three-dimensional measurement technique offered by the ARAMIS system. Simultaneously to the experimental tests, numerical calculations were carried out using progressive failure analysis (PFA), based on the damage initiation Hashin's criterion of as well as damage evolution based on the energy criterion. In the numerical analyses, the cohesive zone model (CZM) and the model allowing for the simulation of damage due to material cracking (xFEM) were also used. A significant effect of conducted numerical calculations was the simulation of the failure phenomenon of thin-walled composite structures, in terms of loss of load-carrying capacity, using three independent damage models (model PFA, CZM and xFEM). The above constitutes a novelty, with respect to current papers from the subject literature. The use of the above-mentioned techniques of experimental research and numerical simulations made it possible to conduct a comprehensive analysis of the damage state of the composite material. The obtained results of the numerical tests demonstrated very high agreement with the results of the experimental studies.

Ultra Wideband Radar for Respiratory Monitoring on Sleep Position

Sleep apnea is a sleep disorder that has a relation with respiratory system during sleep. One of the sleep apnea characteristic is suddenly stop breathing during sleep. People have the different of respiratory rate (RR) which is affected by sleep positions and body mass index (BMI).There are four sleep positions affecting the respiratory rate (RR). Polysomnography (PSG) is conventionally used to analysis the sleep apnea. This technique requires body contact that might be uncomfortable for the patient. In this study, the Xethru X4M200 radar sensor is proposed as non-contact tool to detect the RR by implementing the Doppler effect. Furthermore, the relation between RR with the sleep position and the BMI are discused. For that purpose, 20 participants (10 males and 10 females) with dierent BMIs and sleep positions are examined by monitoring their chest movement. This method is able to detect the indication of bradypnoea or tachypnoea. Futher systematic study and more participants are required to confirm our results and provide better non-contact technique for RR measurement.

Two-dimensional fluid viscosity measurement in microchannel flow using fluorescence polarization imaging

This study describes the development of a noncontact and two-dimensional fluid viscosity measurement technique based on fluorescence polarization microscopy. This technique exploits fluorescence depolarization due to rotational Brownian motion of fluorophores and determines fluid viscosity in microchannel flow by measuring steady-state fluorescence polarization. The main advantage of the technique is that planar distributions of fluid viscosity can be visualized by noncontact optical measurement, while commonly-used mechanical viscometers measure the viscosity of bulk liquids. Moreover, steady-state polarization measurements are realized using a simpler experimental setup compared to other noncontact techniques such as time-resolved fluorescence lifetime/polarization measurements. The relationship between the fluid viscosity (μ) and the fluorescence polarization degree (P) was experimentally obtained using casein molecules labeled with fluorescein isothiocyanate as a fluorescent probe. The fluid viscosity was controlled within the range of 0.7–3.0 mPa s, which is the range often encountered in biological materials, by mixing sucrose or glucose with the solution. The fluid temperature was maintained uniform at 30 °C during the measurement. The calibration result showed that 1/P linearly increased with 1/μ which qualitatively agreed well with the theoretical prediction. The measurement uncertainty was 7.5%–9.5% based on the slope of the calibration curve. The viscosity gradient generated by the mass diffusion between the two solutions co-flowing in the Y-shaped microchannel was clearly visualized under uniform temperature conditions by applying the calibration curve. Finally, the influence of the temperature change on P was experimentally evaluated. The results supported the applicability of the present technique for visualization of the viscosity distribution induced by temperature change. These results confirmed the feasibility of the present technique for analyzing microscale viscosity fields associated with mass transport or temperature change.

Non-contact measurement of traveling wave of overhead transmission line

This study proposes a non-contact measurement technique for traveling waves in overhead high-voltage transmission lines. To provide an accurate, efficient, and reliable measurement of the overhead transmission lines, the proposed method utilizes tunnel magnetoresistance sensor arrays that do not require information about the line parameters to evaluate and measure the traveling waves of the overhead transmission line. Further, it diagnoses the operation status of the overhead transmission line by enhancing the system reliability. An experiment is performed to test the feasibility and reliability of the proposed method compared with conventional current transformers. The simulation results demonstrate that the proposed method performs satisfactorily with respect to providing a reliable, cost-effective, and accurate measurement of the traveling waves of overhead transmission lines.

Temperature-dependent Raman studies and thermal conductivity of direct CVD grown non-van der Waals layered Bi2O2Se

Layered materials with the van der Waals gap have been extensively studied due to their fascinating properties. However, non-van der Waals type layered Bi2O2Se exhibiting remarkable properties is challenging to grow due to the weak electrostatic interaction among layers. Herein, we present chemical vapor deposition (CVD) growth of an air-stable ultrathin Bi2O2Se semiconductor with high structural and chemical uniformity. By tuning the growth temperature, we obtained ultra-smooth single crystals of few-layer Bi2O2Se (LBOS) on mica and quartz substrates, as confirmed from x-ray diffraction, micro-Raman, and high-resolution TEM analyses. Furthermore, a low-temperature Raman study has been conducted to better realize phonon dispersion in the as-grown LBOS in the temperature range 78–293 K. It is observed that the A1g phonon mode frequency of LBOS varies linearly with the temperature with a first-order temperature coefficient (α) of −0.017 87 ± 0.0011 cm−1 K−1. The broadening of the Raman spectral linewidth with temperature has been explained based on the phonon decay, and a phonon lifetime of 2.08 ps is found for LBOS at absolute zero temperature. Finally, the in-plane thermal conductivity of LBOS is estimated by a non-contact measurement technique in a relatively straightforward way. Taking advantage of the excitation power dependency of the A1g mode and using the first-order temperature coefficient, the in-plane thermal conductivity of LBOS is estimated to be ∼1.6 W/mK. Our results pave the way for large-area CVD growth of LBOS on arbitrary substrates and developing insights into electron–phonon and phonon–phonon interactions in non-van der Waals 2D materials.

Measuring the surface temperature of light-emitting diodes by thermoreflectance

As the latest applications of LEDs require more harsh operating conditions, understanding the device thermal properties becomes more essential for further improving the device efficiencies. In applications where heat dissipation can be a critical issue, thermoreflectance (TR) can be utilized as a useful noncontact measurement technique for analyzing the thermal properties. In this paper, we investigate the TR method of measuring the surface temperature, using a lateral-type blue LED chip under high-power operation. The TR we employ measures the change in reflectivity from the Au metal electrode. By comparing with surface/junction temperatures measured by other methods based on the thermocouple and the forward voltage, we find that the TR method can provide accurate and reliable results of measuring the surface temperature of modern LEDs. A useful insight can also be obtained from the temperature distribution on the LED chip surface.

Experiments on a Thin Panel Excited by Turbulent Flow and Shock/Boundary-Layer Interactions

An experimental methodology was designed to study the effects of turbulent flow and shock/boundary-layer interaction (SBLI) on the postflutter response of a thin, buckled panel. The approach combines a systematic testing strategy with state-of-the-art full-field, noncontact measurement techniques, including pressure-sensitive paint, three-dimensional digital image correlation (DIC), and schlieren imaging. These measurements, combined with traditional sensors, were used to characterize the loading conditions and the structural response. The thermally buckled panel experienced bistable, cross-well oscillations with cavity pressure modulation for turbulent flow conditions. This response was characterized as chaotic using several conventional criteria. As the temperature differential between the frame and panel decreased, the panel response transitioned to periodic. For the first time, shock-induced limit cycle oscillations (LCOs) were also measured using DIC. In the presence of an attached SBLI, the dynamic response was centered about the three-quarter chord. As the strength of the SBLI increased, the LCO initially subsided and then reappeared near the midchord for the strongest shock considered.

A Robust Finite Element-based Filter for Digital Image and Volume Correlation Displacement Data

Digital Image and Volume Correlation (DIC and DVC) are non-contact measurement techniques that are used during mechanical testing for quantitative mapping of full-field displacements. The relatively high noise floor of DIC and DVC, which is exasperated when differentiated to obtain strain fields, often requires some form of filtering. Techniques such as median filters or least-squares fitting perform poorly over high displacement gradients, such as the strain localisation near a crack tip, discontinuities across crack flanks or large pores. As such, filtering does not always effectively remove outliers in the displacement field. This work proposes a robust finite element-based filter that detects and replaces outliers in the displacement data using a finite element method-based approximation. A method is formulated for surface (2D and Stereo DIC) and volumetric (DVC) measurements. Its validity is demonstrated using analytical and experimental displacement data around cracks, obtained from surface and full volume measurements. It is shown that the displacement data can be filtered in such a way that outliers are identified and replaced. Moreover, data can be smoothed whilst maintaining the nature of the underlying displacement field such as steep displacement gradients or discontinuities. The method can be used as a post-processing tool for DIC and DVC data and will support the use of the finite element method as an experimental–numerical technique.

Reference equations for tidal breathing parameters using structured light plethysmography.

Tidal breathing measurements can be used to identify changes in respiratory status. Structured light plethysmography (SLP) is a non-contact tidal breathing measurement technique. Lack of reference equations for SLP parameters makes clinical decision-making difficult. We have developed a set of growth-adjusted reference equations for seven clinically pertinent parameters of respiratory rate (fR), inspiratory time (tI), expiratory time (tE), duty cycle (tI/total breath time), phase (thoraco-abdominal asynchrony (TAA)), relative thoracic contribution (RTC) and tidal inspiratory/expiratory flow at 50% volume (IE50).Reference equations were developed based on a cohort of 198 seated healthy subjects (age 2–75 years, height 82–194 cm, 108 males). We adopted the same methodological approach as the Global Lung Function Initiative (GLI) report on spirometric reference equations. 5 min of tidal breathing was recorded per subject. Parameters were summarised with their medians. The supplementary material provided is an integral part of this work and a reference range calculator is provided therein.We found predicted fR to decrease with age and height rapidly in the first 20 years and slowly thereafter. Expected tI, tE and RTC followed the opposite trend. RTC was 6.7% higher in females. Duty cycle increased with age, peaked at 13 years and decreased thereafter. TAA was high and variable in early life and declined rapidly with age. Predicted IE50 was constant, as it did not correlate with growth.These reference ranges for seven key measures ensure that clinicians and researchers can identify tidal breathing patterns in disease and better understand and interpret SLP and tidal breathing data.

Computer vision‐based real‐time cable tension estimation in Dubrovnik cable‐stayed bridge using moving handheld video camera

Cables are essential components of the cable-stayed bridges as they serve as the main load-bearing component. Hence, continuous monitoring of such cables becomes necessary as they are vulnerable to the fatigue damage induced by dynamic loads. Sensors are attached to the cables to examine the health of the cables; however, these contact-based sensors can malfunction in harsh weather condition, which makes impossible to estimate the cable health in such unfavorable condition. Therefore, in this paper, we propose a completely noncontact video-based stay-cable tension measurement technique where the video is recorded using a moving handheld camera at a significant distance from the structure itself. Here, the cable tension is determined from vibration-based measurement, but the vibration of the cable recorded in the video includes the true vibration of the cable along with the camera motion. Hence, we amalgamated a series of image processing techniques to nullify the camera movement. First, we detect the camera movement based on the movement of the bridge deck and pylon, which are fixed objects, using Kanade–Lucas–Tomasi (KLT) feature tracking algorithm. Then we nullify the camera movement by using the affine transformation matrix obtained by random sample consensus (RANSAC) algorithm. Subsequently from the steady video, the cable motions are estimated using the phase-based motion estimation technique. From the time history of the cable vibration, real-time frequency variations are estimated using Short-Time Fourier Transform (STFT). Finally, the real-time tension is determined from this dominant frequency variation history using the taut-string theory. This paper shows the significant potential of camera-based sensing techniques in structural health monitoring as the mean estimated tension and the design cable tension are found to be comparable.

Nondestructive Evaluation of Mechanical Properties of Femur Bone

In a human body, the femur is one of the strongest and longest bones and commonly fractured bone shown in the last decades, especially in elderly humans. Common femur fractures are caused due to violent trauma and severe accidents. The complex structure and response of the bone under dynamic loading conditions will provide extensive information about the mechanical properties of the bone. In this work, we use a non-contact measurement technique using a Position sensing detector (PSD) to measure the natural frequencies and their corresponding mode shapes. The bone sample excited by the impact hammer, and its response is measured using PSD. Sequential measurements are taken on the sample and base; we take the transfer function of the sample with respect to base to measure the natural frequency of bone. Mechanical property such as elastic modulus of the bone is evaluated using measured natural frequencies, and compared with numerical results. The Modulus of elasticity of the bone is found to be 14.8 GPa. Modal analysis was carried to evaluate the natural frequencies and corresponding mode shapes. Numerical results are found to be within 9% of the experimentally measured results. Random vibration analysis was done to emulate the real-time testing for the bone sample. The measured spectrum follows the numerical data. This experimental technique will aid in the nondestructive evaluation of the mechanical properties of the bone sample. Further,this nondestructive technique can be extended for various biological specimens for calculating the mechanical response.

Blade Crack Detection using Blade Tip Timing

The harsh working environment of compressor threats the integrality of bladed disk. Crack is one of the most fatal faults of rotating blades. Detecting the crack of blades at early stage could ensure the safe operation of gas turbine and save economic costs. Blade tip timing (BTT) is a noncontact blade vibration measurement technique, which is widely used in recent years. In this article, a procedure of crack detection using BTT data is proposed. First, some typical parameters are taken into consideration, including resonance frequency, amplitude change of natural frequency, amplitude of blade tip, phase, and interblade spacing. It has been found that the frequency of the blade will decrease with the increment of crack length and reduction of crack height. In addition, the resonance frequency of the bladed disk will split when the blade cracks. The amplitude of different orders of resonance frequency varies with cracks. The amplitude of the first order changes very slightly, whereas the second and third orders are relatively obvious. The blade tip vibration amplitude and phase change with cracks without obvious regularity. The interblade distance will change due to the appearance of cracks. According to the above rules, the frequency and the interblade distance are adopted as crack diagnosis indicators. First, we use the Lomb-Scargle periodogram to quickly determine whether the crack appears and then use the blade frequency and interblade distance to locate the number of the blade having crack. In the experimental test, BTT data measured on a titanium bladed disk is used to verify the effectiveness of our method.

A FRAMEWORK TO DEVELOP INTELLIGENT SYSTEM FOR CAPTURING PRODUCT FEATURES USING OPEN CV TECHNIQUE

This research aims to propose an innovative framework using ISO14649 standard to detect defects in manufactured shaped objects or geometric surfaces of non-linear products of the CNC machine. The significant importance in order to recognize the potential to improve industry product quality inspection and encourage the waste of timing machines and product rejection. Open Computer Vision (Open CV) offers a smart, non-contact measurement and cost-effective technique to fulfil the requirements. The framework depends on the new technique of Open CV, which includes two parts: an intelligent selection of work-piece capturing the image for a particular inspection of the planar interfaces such as the hole, rectangular, pocket one, and the symmetric lighting model comparison approach for measurement of defects in the matched images. The contribution of this study is to build a structure in the computer vision method with a convolution neural network that predicts the classification of the feature for better accuracy and emphasizes the significant characteristics of the image processing technique coupled with experimental data on demanding image datasets and quality inspection measures.

Bridge Load Testing: State-of-the-Practice

Bridge load testing can answer a variety of questions about bridge behavior that cannot be answered otherwise. The current governing codes and guidelines for bridge load testing in the United States are the 1998 NCHRP Manual for Bridge Rating through Load Testing and Chapter 8 of the AASHTO Manual for Bridge Evaluation. Over the last two decades, the practice of load testing has evolved, and its intersections with other fields have expanded. The outcomes of load tests have been used to keep bridges open cost-effectively without unnecessarily restricting legal loads, when theoretical analyses cannot yield insights representative of in-service performance. Load testing data can be further used to develop field-verified finite-element models of tested bridges to understand these structures better. In addition, structural reliability concepts can be used to estimate the probability of failure based on the results of load tests, and noncontact measurement techniques capturing large surfaces of bridges allow for better monitoring of structural responses. Given these developments, a new Transportation Research Board (TRB) Circular, Primer on Bridge Load Testing, has been developed. This document contains new proposals for interpreting the results of diagnostic load tests, loading protocols, and the determination of bridge load ratings based on the results of proof load tests. In addition, included provisions provide an estimation of the resulting reliability index and the remaining service life of a bridge based on load testing results. The benefit of load testing is illustrated based on a cost-benefit analysis. The current state-of-The-practice has demonstrated that load testing is an effective means for answering many important questions regarding bridge behavior that are critical to decisions on bridge maintenance or replacement. Load testing has evolved over its history, and the newly developed TRB Circular reflects this evolution in a practical way.

Age and gender related differences in load-strain response in C57Bl/6 mice.

We examined the changes in mechanical strain response of male and female mouse tibia and ulna, using axial compression tests, to assess age-related changes in tibiae and ulnae by a non-contact strain measurement technique called the digital image correlation (DIC) and the standard strain gage. A unique aspect of the study was to compare bones from the same animal to study variations in behavior with aging. This study was conducted using male and female C57Bl/6 mice at 6, 12 and 22 months of age (N=6-7 per age and sex) using three load levels. The DIC technique was able to detect a greater number of statistically significant differences in comparison to the strain gaging method. Male ulna showed significantly higher DIC strains compared to strains captured from strain gage at all three levels of load at 6 months and in the lowest load at 12 months. DIC measurements revealed that the ulna becomes stiffer with aging for both males and females, which resulted in 0.4 to 0.8 times reduced strains in the 22-month group compared to the 6 month group. Male tibia showed three-fold increased strains in the 22 months group at 11.5 N load compared to 6 months group (p<.05).

Deep draw induced wrinkling of engineering fabrics

Deep-draw experiments are performed on both glass and carbon fabric both to better understand the origin of wrinkle growth during complex forming experiments and to assess the accuracy, robustness and computational cost of forming simulations of engineering fabrics. During experiments, the shape of the deformed blanks is digitised using two different non-contact measurement techniques (Structured Light Scanning and Photogrammetry). The resulting digital point clouds permit detailed analysis of wrinkle growth and shows that the simulations perform well in predicting the very different forming behaviours of the two fabrics. The sensitivity of wrinkle formation to initial conditions is demonstrated in both experiments and simulations and the direction of wrinkle growth during the forming process is shown to influence wrinkle draw-in; an observation that could potentially be used to mitigate wrinkle draw-in during actual forming processes.

High-Accuracy 3D Optical Profilometry for Analysis of Surface Condition of Modern Circulated Coins.

The article shows that noncontact measurement techniques can be an important support to X-ray-based methods when examining the surface condition of modern circulated coins. The forms and degrees of wear of such coins, affecting their utility values, qualifying them as a legal tender in a given country, can be measured and analyzed, among other things, using advanced high-accuracy optical profilometry methods. The authors presented four analyses carried out for reverses and obverses of round coins (1 zloty, 1 franc, 50 bani, 5 pens) characterized by different degrees of surface wear. All of the coins were measured using 3D optical profilometers (Talysurf CLI 2000 and S neox) representing two generations of these types of systems. The obtained results confirm the validity of the applied high-accuracy measurement systems in conjunction with dedicated software in the presented applications. Examples of the analyses carried out can be a significant source of information on the condition of coins in the context of maintaining their functional properties (selection of appropriate wear–resistant alloys and correctness of the production process).