Strain Signals Research Articles

Composite biomaterial for mimetic electric skin generated by conductive polymer/anion synergistic effect

A versatile bionic E-skin sensor was fabricated based on an electronic/ionic-conductive hydrogel, which could perceive tiny and large strain signals in a wide sensing range.

Research on Root Strain Response Characteristics of Inner Ring of Planetary Gear Transmission System with Crack Fault

This paper established the system dynamics model for two kinds of tooth cracks of different depths of the sun gear and inner gear ring to study the influence mechanism of crack failure on the tooth root strain of the planetary gear transmission system. Combined with the finite element model of the inner gear ring, the tooth root strain of the ring was solved. Experiments verified the correctness of the solution method. The root strain under the crack fault of the sun gear and the tooth crack fault of the inner gear ring is analyzed, and the following conclusions are drawn: Periodic fault impact occurs in the strain signal of the tooth root of the inner gear ring during the crack fault of the sun gear root. The fault can be extracted by the fast spectral kurtosis method (FSK), and the fault components are used to determine whether the sun gear cracks. The Lempel-Ziv index showed a tendency to increase gradually during the process of solar wheel crack deepening, which could be used as the damage index of crack depth. The results can provide a basis and reference for fault diagnosis.

Prediksi Umur Lelah Lower Suspension Arm Minibus yang Dikemudikan pada Permukaan Jalan Lurus dan Berbelok Berbasis Pendekatan Strain-Life

In the previous studies, prediction of fatigue life at the lower suspension arm is only done based on strain signals obtained on a straight road. Considering the main function of the lower suspension arm is to stabilize the vehicle when turning, the purpose of this study is to predict the fatigue life of the lower suspension arm when the vehicle goes straight and turns clockwise and counterclockwise. The three roads are passed by vehicles with a speed of 30 km/hour. Measurement of strain signals is done by attaching a strain gauge to the lower suspension arm on the left side of the vehicle. Based on the simulation results based on the strain-life approach the lowest fatigue life is given by turning clockwise direction with 2.56E+6 cycles so that it breaks using the Coffin-Manson model. This value is low than the age of fatigue life when the vehicle goes straight and turns counterclockwise, each with 5.85E+6 cycles so it breaks and 5.08E+7 cycles so it breaks. This value is also comparable to that produced by the Morrow and SWT models. When the vehicle turns right, the lower suspension arm on the left side receives a strain that is greater than when the vehicle turns left, which is 5%. Strain received by the lower suspension arm can shorten the fatigue life of the component. Turning roads shorten the fatigue life of lower suspension arm so that 44% compared to straight roads.

Prediksi Umur Lelah Pegas Ulir Suspensi Depan Minibus yang dikemudikan di Atas Permukaan Jalan Datar, Menanjak dan Menurun Berazaskan Pendekatan Strain-Life

This study aims to evaluate the effect of road conditions on the fatigue life of coil springs using the strain life approach. This approach is accomplished by measuring the strain signal in the coil spring at the front of the car with a strain gauge at the component's critical point. Three different types of roads, namely flat roads, uphill roads, and downhill roads were chosen to test the strain signals obtained. After analysis, it was found that the fatigue life of the coil spring on the downhill road had the lowest value of 1.52e+4 cycles before it broke. This value is 54% lower than the fatigue life on flat roads and 96% lower than on uphill roads. This result is due to the braking factor on the way down which puts a higher tension on the coil springs, reducing their fatigue life. This study can contribute to the automotive industry to consider different road conditions in the design and testing of their products, especially in critical components such as coil springs. The strain life approach has also been shown to be effective in evaluating the fatigue life of automobile components, which can help improve vehicle quality and safety.

Prediksi Usia Kelelahan Pegas Ulir dan Lower Suspension Arm Berdasarkan Pendekatan Strain Life Berdasarkan Bentuk Permukaan Jalan

This study aims to determine the effect of road surface contours on fatigue life of coil springs and lower suspension arm. In this study, strain gauge was affixed to the critical point of the minibus front suspension coil springs based on stress distribution. Strain signal obtained was analyzed using the Coffin-Manson, Morrow, and SWT approaches. From the results of the chemical composition test, it was found that the coil springs were made of SAE 5160 and lower suspension arm made of AISI 1513. From the results of this study it can be concluded that when the vehicle drive on the damaged road, coil spring and lower suspension arm received greater stress so that provide shorter fatigue life. Fatigue life of coil spring on rough roads is 16% lower than city roads and 7% lower than flat roads. Whereas fatigue life of lower suspension arm on rough roads is 27% lower than city roads and 0.03% lower than flat roads. So that the coil spring components fail faster than the lower suspension arm. This is because the contour of the road surface provides a vertical load so that it is in accordance with the function of the coil spring which works to reduce the load vertically while the lower suspension arm function holds the load when turning.

On the need to evaluate the probabilistic of fatigue life assessment of random strain loading considering load sequence effects

This study presents a probabilistic method of fatigue life assessment for random strain signals that consider the effect of load cycle sequences. The Effective-Strain-Damage (ESD) model was utilised to calculate the fatigue life of coil spring. The probabilistic approach was used to evaluate the reliability properties of the fatigue life data, indicating that the ESD model estimated lower fatigue life than conventional strain-life models as the load sequence effect encouraged rapid crack propagation. Furthermore, a lower mean-cycle-to-failure (McTF) of 4.53 × 104 blocks to failure was estimated from the ESD-based fatigue life, as it was 7.5–8.1% lower than the McTFs computed from the fatigue life predicted by other models. The results indicated that the coil springs had lower fatigue reliability when the load cycle sequence was included. The McTF can be used as a representation of the reasonable service cycle of the coil spring since the uncertainties of the random loading were considered. Finally, this approach suggested a more appropriate assessment of the life cycle of coil springs subjected to random loading conditions with many uncertainties.

Liquid Core Detection and Strand Condition Monitoring in a Continuous Caster Using Optical Fiber

Real-time monitoring of the liquid core position during the continuous casting of steel has been demonstrated using low-cost distributed optical-fiber-based strain sensors. These sensors were installed on the containment roll support structures in the segments of a production continuous caster to detect the position of the solid-liquid interface and monitor the strand condition during the continuous casting. Distributed Fiber Bragg Grating sensors (FBGs) were used in this work to monitor strain at six roll positions in the caster. The sensor performance was first validated by comparing optical strain measurements with conventional strain gauge measurements in the lab. Next, optical strain measurements were performed on an isolated caster segment in a segment maintenance facility using hydraulic jacks to simulate the presence of a liquid core under the roll. Finally, the sensors were evaluated during caster operation. The sensors successfully detected the load increase associated with the presence of a liquid core under each instrumented roll location. Incidents of bulging and roll eccentricity were also detected using frequency analysis of the optical strain signal. The liquid core position measurements were compared using predictions from computer models (digital twins) in use at the production site. The measurements were in good agreement with the model predictions, with a few exceptions. Under certain transient caster operating conditions, such as spraying practice changes and SEN exchanges, the model predictions deviated slightly from the liquid core position determined from strain measurements.

Paper-Based Sensor with Bioinspired Macrogrooves for Dual Pressure and Mechanical Strain Signal Detection

Paper-Based Sensor with Bioinspired Macrogrooves for Dual Pressure and Mechanical Strain Signal Detection

Hybrid Fiber Optic Cable for Strain Profiling and Crack Growth Measurement in Rock, Cement, and Brittle Installation Media.

Brillouin scattering-based distributed fiber optic sensing (DFOS) technologies such as Brillouin optical time domain reflectometry (BOTDR) and Brillouin optical time domain analysis (BOTDA) have broad applicability for the long term and real-time monitoring of large concrete structures, underground mine excavations, pit slopes, and deep subsurface wellbores. When installed in brittle media, however, the meter scale spatial resolution of the BOTDR/A technology prohibits the detection or measurement of highly localized deformations, such as those which form at or along cracks, faults, and other discontinuities. This work presents a novel hybrid fiber optic cable with the ability to self-anchor to any brittle installation media without the need for manual installation along fixed interval points. Laboratory scale testing demonstrates the ability of the hybrid fiber optic cable to measure strains across highly localized deformation zones in both tension and shear. In addition, results show the applicability of the developed technology for strain monitoring in high displacement environments. Linear relationships are proposed for use in estimating the displacement magnitude along discontinuities in brittle media from strain signals collected from the hybrid fiber optic cable. The hybrid fiber optic cable has broad potential applications, such as geomechanical monitoring in underground mines, surface pits, large civil infrastructure projects, and deep subsurface wellbores. The benefits of fiber optic sensing, such as the intrinsic safety of the sensors, the long sensing range, and real time capabilities make this a compelling technique for long term structural health monitoring (SHM) in a wide range of industrial and civil applications.

Data-driven identification of structural damage under unknown seismic excitations using the energy integrals of strain signals transformed from transmissibility functions

In recent years, the methodology based on the energy variations of structural dynamic strain responses has been developed. Although it is an efficient data-driven structural damage identification approach, it can only be used for structures under impulse or known excitations. To overcome this limitation, an improved method is proposed in this paper for the rapid damage identification of beam-like structures using structural dynamic strain responses under unknown seismic excitations. The influence of different excitations to an intact and damaged structure, in which the intact structure is under ambient excitations and structural damage is caused by unknown seismic excitations, is eliminated via the transmissibility functions (TFs) of measured structural strain responses. Contrary to the previous TFs of structural acceleration or displacement responses, TFs of structural strains is more sensitive to local damage in beam-like structures. Moreover, power spectral density transmissibility functions (PSDTFs) are used instead of the traditional Fourier transform TFs. Then, through the inverse Fourier transformation in the frequency domain, the PSDTFs are returned to the time-domain signals to avoid the problem of selecting the proper frequency band in previous studies on identifying structural damage based on TFs in the frequency domain. Finally, structural damage can be identified based on the energy variations of the time-domain strain signals from the intact and damaged structures. Numerical examples of structural damage identification of a seven-storey planar frame and a cable-stayed bridge girder under unknown seismic excitations are provided to demonstrate the effectiveness and robustness of the improved method. Moreover, structural damage identification of a laboratory cable-stayed bridge tower model subjected to shaking table tests is performed to validate the good performance of the proposed method.

Outside Front Cover: Volume 3 Issue 4

Outside front cover image: A customizable and multi-functional electronic conductive organogel is proposed by combining conductive carbon nanotube clusters and flexible adhesive organogels. Based on customizable conductive networks and entropy-driven organogel actuation, the conductive organogels can sense various strain and stress signals and imitate natural organisms with muscle actuation and neurofeedback. This strategy for preparing electronic conductors can enhance the rational design of soft robotics and flexible sensors, facilitating further progress of artificial intelligent systems. (DOI: https://doi.org/10.1002/smm2.1108)

Optical Fiber Serpentine Arrangements for Vibration Analysis Using Distributed Acoustic Sensing

Distributed acoustic sensors (DASs) are able to monitor in real-time acoustic excitation and mechanical vibration of the external environment for many kilometers along the length of the optical fiber. In the oil industry, the technology allows the monitoring of well structural health, identifying flow profile, acquiring seismic data, updating reservoir information, and feeding geological models. The spatial resolution of DAS is a limiting factor on the quality of information gathered. In this article, we propose and analyze a novel method of measuring local dynamic strain of structures using DAS. The method uses serpentine configurations to measure the frequency spectrum of the in-phase strain signals at discrete regions of the structure, enabling DAS to determine, among other vibration parameters, the strain frequency response function (SFRF). An experimental study of the sensor application with different arrangements in a small structure has been performed. The structure in the experiment consists of a free–free aluminum beam of approximately 2.7 m. Experiment results show agreement with numerical results developed by the finite element method (FEM) and using reference sensors, demonstrating a significant improvement of the DAS SFRF accuracy using the serpentine configuration and up to 12.9 dB increase in peak-to-noise ratio (PNR) for low excitation forces. The recovered response enabled the reconstruction of mode shapes.

Stress–strain-based crack damage detection of composite structures using selective kernel convolutional networks and continuous wavelet transform

Composite structures are widely used due to their excellent performance. To improve their safety and reliability, non-destructive testing (NDT) methods are implemented to achieve efficient damage detection. In this paper, a novel stress–strain-based damage detection approach is proposed for composite structures by using continuous wavelet transform (CWT) and selective kernel convolutional network (SKNet), which exhibit good robustness when dealing with the stress–strain signals collected from different positions of composite structures. First, a stress–strain-based measuring scheme is designed for vibration response monitoring of the composite structures. Second, the collected stress–strain signals are converted into two-dimensional time–frequency images by the CWT. Then, the SKNet is constructed to classify these images for damage detection. Finally, an experimental test is conducted on a composite capsule, data from which is employed to evaluate the proposed method. The comparison results of our proposed method and other state-of-the-art approaches demonstrate its superiority.

Analysis of LVE behaviour and fatigue damage evolution of asphalt pavements with different interface conditions in an accelerated full-scale experiment

ABSTRACT For better optimization of pavement design and management, accelerated full-scale pavement tests (APT) represent very efficient tools to study pavement behaviour from initial to damaged condition. This paper presents an experimental study where three asphalt pavements with different interface conditions between the asphalt layers were tested in an APT experiment. Asphalt layer strains, FWD deflections, and surface cracking were monitored during the experiment. First, strain signals and pavement surface deflections measured at the beginning of the experiment, were used to characterize the viscoelastic properties of the asphalt layers. Then the measurements were used to analyze the fatigue behaviour of the experimental pavements, and the evolution of their level of damage to traffic. The analysis showed that in such asphalt pavements, asphalt strains, which varied significantly with the increase of load cycles, were not suitable for estimating an ‘average’ asphalt layer damage. In order to monitor the general pavement behaviour, a new damage ratio was introduced, based on FWD back-calculated moduli of the asphalt layers, that allowed to observe a stiffness increase of the asphalt layers at the beginning of the loading due to aging and post-compaction, and then fatigue damage evolution which had a very good correspondence with surface cracking.

VIBRATION AND STRAIN SIGNAL ACQUISITION FOR NUMERICAL SIMULATION OF A COFFEE HARVESTER

Coffee harvesters utilize vibration systems to dislodge coffee beans. The vibration system is usually coupled to the end of an axis (rod cylinder). This cylinder can fail in the field, which usually occurs by means of cracks close to its flange in the region that promotes vibration. Numerical simulations are typically used to predict strains and stresses based on vibration signals in machines in general. This work acquired the vibration and strain signals of a coffee harvester rod cylinder prototype and compared the results using finite element analysis. To this end, a rod cylinder system was prototyped on a reduced scale (1:3) to recreate frequency and strain data, which were used for numerical simulation comparisons. The results showed that the predicted von Mises stress in the analyzed zone was 16.47 MPa (below the material yield strength, 250 MPa) based on a frequency of 14.2 Hz applied to the rod cylinder. This confirmed that cracks found in rod cylinders in the field are not generated by high stresses, as reported in the literature. The results demonstrated the potential of finite element analysis for strain and stress prediction when applied to agricultural machine components.

Model-based analysis of myocardial strains in left bundle branch block

IntroductionAlthough observational studies of patients with left bundle branch block (LBBB) have shown a relation between strain morphologies and responses to cardiac resynchronization therapy (CRT), the evaluation of left ventricle (LV) dyssynchrony from echocardiography remains difficult. The objective of this article is to propose a patient-specific model-based approach to improve the analysis and interpretation of myocardial strain signals.MethodsA system-level model of the cardiovascular system is proposed, integrating: (i) the cardiac electrical system, (ii) right and left atria, (iii) a multi-segment representation of the RVs and LVs, and (iv) the systemic and pulmonary circulations. After a sensitivity analysis step, model parameters were identified specifically for each patient. The proposed approach was evaluated on data obtained from 10 healthy subjects and 20 patients with LBBB with underlying ischemic (n = 10) and non-ischemic (n = 10) cardiomyopathies.ResultsA close match was observed between estimated and observed strain signals, with mean RMSE respectively equal to 5.04 ± 1.02% and 3.90 ± 1.40% in healthy and LBBB cases. The analysis of patient-specific identified parameters, based on bull's-eye representation, shows that strain morphologies are related to both electrical conduction delay, and heterogeneity of contractile levels within the myocardium.DiscussionThe model-based approach improve the interpretability echocardiography data by bringing additional information on the regional electrical and mechanical function of the LV. The analysis of model parameters show that septal motion and global strain morphologies are not only explained by electrical conduction delay but also by the heterogeneity of contractile levels within the myocardium. The proposed approach represents a step forward in the development of personalized LV models for the evaluation of LV dyssynchrony in the field of CRT.

A replication-deficient H9N2 influenza virus carrying H5 hemagglutinin conferred protection against H9N2 and H5N1 influenza viruses in mice

H5N1 and H9N2 influenza viruses have been reported to cause human infections and are believed to have pandemic potential. The vaccine is an effective tool to prevent influenza virus infection. However, inactivated influenza vaccines sometimes result in low antigenicity as result leads to generating of incomplete immune protection in the form of low cellular and humoral immunity. While the low temperature adapted, traditional live attenuated influenza vaccine (LAIV) is associated with the potential risk to revert to a virulent phenotype, there appears an essential need for an alternative potent methodology to design and develop influenza vaccines with substantial safety and efficacy which may confer solid protection against H9N2 or H5N1 influenza virus infections. In the present study, a replication-deficient recombinant influenza virus, WM01ma-HA(H5), expressing hemagglutinin (HA) of both H9N2 and H5N1 subtypes was developed. The chimeric gene segment expressing HA(H5), was designed using the sequence of an open reading frame (ORF) of HA adopted from A/wild duck/Hunan/021/2005(H5N1)(HN021ma) which was flanked by the NA packaging signals of mouse-adapted strain A/Mink/Shandong/WM01/2014(H9N2)(WM01ma). Due to the absence of ORF of structural protein NA, the replication of this engineered H9N2 influenza viruses WM01ma-HA(H5) was hampered in vitro and in vivo but was well competent in MDCK cells stably expressing the NA protein of WM01ma. Intranasal vaccination of mice with WM01ma-HA(H5) stimulated robust immune response without any clinical signs and conferred complete protection from infection by H5N1 or H9N2 subtype influenza viruses.

Real-Time Virtual Sensing for Dynamic Vibration of Flexible Structure via Fiber Bragg Grating Sensors

Real-time monitoring of the dynamic vibrations of beam-type structures indicates important implications in aerospace engineering applications, in which the additional sensing information about vibration parameters, including displacements, rotational angles, angular rates, as well as accelerations, facilitates the improvement of the system’s safety. This article proposed a virtual sensing method with the usage of fiber Bragg grating (FBG) strain sensors to directly estimate the vibration parameters from the measured strains. The algebraic relationships of displacement–strain and rotation–strain on the sensor’s installing points as well as the boundary points are obtained based on the Birkhoff interpolation method, and meanwhile, the explicit expressions on angular rates and accelerations are derived. Furthermore, a tracking differentiator is used to recover the strain signals and their first- and second-order derivatives from the noisy measurements in order to real-time estimate the angular rates and accelerations of the vibrating beam. Differing from the classical modal-based method, complex modal decomposition is not required in the proposed method. The comparison of numerical simulation results reveals that the proposed method has advantages over the modal-based method in accuracy and efficiency. Furthermore, the laboratory experiments indicate that the proposed method is effective for real-time estimating vibration parameters from the noisy measured strains.

Study on Macro-Meso Deformation Law and Acoustic Emission Characteristics of Granular Gangue under Different Loading Rates

Bulk gangue is a common backfill material in solid backfill mining. After backfilling into the goaf, bulk gangue serves as the main body to bear the load of overlying strata, and its deformation resistance is the key factor affecting the backfill quality. In this study, the laterally confined compression test of broken gangue was designed, the compaction deformation characteristics of gangue specimens under different loading rates were studied, the acoustic emission (AE) energy characteristics of gangue specimens under compression were analyzed, and the relationship model between macroscopic deformation of broken gangue under compression and AE energy was established. The particle flow numerical software PFC2D was used to stimulate the particle breakage in the gangue compaction process, and the coal gangue particle model was established through particle cluster units. The particle force chain distribution and fracture evolution characteristics of gangue specimens in the compression process were studied, and the macroscopic deformation mechanism was revealed from the mesoscopic perspective. The results showed that: the porosity variation of the gangue specimen increases with the increase of loading rate; the porosity increases with the decrease in the strain, the porosity decreases with the increase in the stress, and the relationship between porosity and stress is monotonously decreasing. With the increase of loading rate, the AE signals produced by particle breakage become stronger, while the influence of the loading rate on the maximum strain, fragmentation and AE signal of the specimen is gradually weakened. Under different loading rates, the “instability-optimization” of the skeleton force chain structure of the gangue model and the crushing-recombination of cracks are the main reasons for the compaction deformation of gangue specimens at the early stage of loading. The research results are of great significance to reveal the deformation mechanism of coal gangue as backfill materials under compression.

Biomechanical analysis of a lacunar-canalicular system under different cyclic displacement loading

The objective of this study is to use the finite element (FE) method to predict the mechanical signals (interstitial fluid velocity, strain, pore pressure, and pore fluid velocity) produced by osteocyte during physiological activities. The model predicts that the amplitude and distribution of the mechanical signals are mainly affected by the loading rate. The magnitude of mechanical signals in the lacunar-canalicular system increases as the amplitude, frequency and amount of direction of load increase. Collagen hillocks can effectively amplify strain signals at the process. The established model can be used for studying the mechanism of bone mechanotransduction at the micro-level.