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The reactor is the core device used in guaranteeing the alloy's stable high-level reversible hydrogen storage. This work investigates a rotating reactor as new structure to alleviate stress accumulation using inertial force and counterforce, compared to typical statics reactors. The rotating reactor's strain and response exhibited notable differences in the whole five stages at the 8th absorption/desorption cycle. In the cycle of vertical reactor, plastic deformation began by the 4th cycle, followed by a rapid linear increase in strain values leading swiftly to failure in the 19th cycle. When inverted, plastic deformation began by the 17th cycle and fracture occurred after 29th cycles, and for rotating reactor at 1.39 rpm, the curve of stress accumulation changed gently, sudden fracture occurred after 36th cycles. Particle size distribution of rotating reactor was skewed toward the large size as a herald of more strong anti-pulverization. Meanwhile, the expansion area was located in lower part, and the bulging notably shifted upwards compared to vertical reactor. This was attributed to the fact that the dynamic inertial force and counterforce effect improved the uniformity of alloy filling and prevented the formation of high-density areas at the representative bottom obviously alleviating local stress concentration phenomena. • Rotating reactor creates inertial force and counterforce via hydrogen cycling. • Caused the rearrangement of pulverizable alloy movement through rotation. • Improved anti-pulverization of alloys due to inertial and counterforce. • Reduced residual strain, maximum stress and its accumulation duration. • Service life extended by 1.4 and 1.9 times compared to statics reactors. [ABSTRACT FROM AUTHOR]

When a structure is randomly excited by its installation base, significant vibration stress may be caused within it, thus causing damage to the structure. The authors find in the vibration fatigue test that when the notched slender beam specimen is excited by stationary Gaussian random base movement, the measured acceleration response and strain response of the specimen have obvious nonstationary characteristics. The vibration responses of the specimen under Gaussian and non‐Gaussian random base excitations are calculated by the finite element method and corresponding vibration fatigue tests were completed. The nonstationary characteristics of the responses from calculations and experiments are analyzed. Finally, a method for calculating the fatigue life of the specimen under nonstationary response is given, and the calculated results are compared with the measured data. The results indicate that the method proposed in this article performed excellent calculation fatigue life with measured strain data. [ABSTRACT FROM AUTHOR]

In recent years, lead-free Bi 0.5 Na 0.5 TiO 3 (BNT) based piezoelectric ceramics with excellent strain properties have gained widespread recognition for their application in high-precision displacement actuators. The (1- x)(0.82Bi 0.5 Na 0.5 TiO 3 -0.18K 0.5 Bi 0.5 TiO 3)- x Ba(Fe 0.5 Sb 0.5)O 3 ceramics were fabricated through the die-pressing method in this work. The effect of BFS introduction on the dielectric, ferroelectric and microstructure characteristics of BNKT ceramics was systematically investigated. Among these compositions, the BNKT-0.015BFS ceramics exhibited a piezoelectric strain coefficient (d 33 *) of 658 pm/V at an electric field of 55 kV/cm, while achieving a strain response of 0.51 % at 85 kV/cm. The observed improvement in strain performance can be attributed to the evolution from non-ergodic relaxor state to ergodic relaxor state caused by BFS substitution. Furthermore, transmission electron microscopy (TEM) explicitly confirmed coexistence of rhombohedral and tetragonal phase and revealed the morphology of nanosized domains. This study adds to a deeper comprehension of the characteristics of strain response enhancement in BNT-based ceramics, opening up avenues for designing novel lead-free piezoelectric ceramics with outstanding electromechanical performance. [ABSTRACT FROM AUTHOR]

Damages to various building structures often occur over their service life and can occasionally lead to severe structural failures, threatening the lives of its residents. In recent years, special attention has been paid to investigating various damages in buildings at the early stage to avoid failures and thereby minimize maintenance. Structural health monitoring can be used as a tool for damage quantification using vibration measurements. The application of various sensors for measuring accelerations, velocity and displacement in civil infrastructure monitoring has a long history in vibration-based approaches. These types of sensors reveal dynamic characteristics which are global in nature and ineffective in case of minor damage identification. In a practical application, the available damage detection approaches are not fully capable of quickly sensing and accurately identifying the realistic damage in structures. Research on damage identification from strain data is an interesting topic in recent days. Some work on the cross-correlation approach is now a centre of attraction and strictly confined to bridge or symmetric structures. The present paper uses strain data to validate the cross-correlation approach for detecting damage to building structures. The effectiveness of the methodology has been illustrated firstly on a simply supported beam, then on a 5-storey steel frame and a 6-storey scaled-down reinforced concrete shear building and lastly on a frame structure with moving load as a special case. The results show that this approach has the potential to identify damages in different kinds of civil infrastructure. [ABSTRACT FROM AUTHOR]

Bismuth sodium titanate (BNT) ceramics exhibit outstanding strain responses but are unfavorable for application in high-sensitivity displacement actuators due to the large negative strain resulting from irreversible changes in their phase transition and domain structure. Here, (1−x)Bi0.50Na0.41K0.09TiO3–xNaNbO3 (BNKT−xNN) solid solutions were prepared to improve the strain properties through the strategy of modulating the phase boundary and domain structures. The introduction of sodium niobate could effectively regulate the relative content of the tetragonal (P4bm) and rhombohedral (R3c) phases in the phase boundary region. The ferroelectric-to-relaxor phase transition (TF−R) was reduced, and the ergodic relaxor (ER) state was nurtured at room temperature. Excellent zero-negative strain properties of S = 0.41% and d33* = 742 pm/V were achieved from the reversible transition between the ER and ferroelectric states under an applied electric field (x = 0.04). Additionally, understanding the domain states via piezoelectric force microscopy (PFM) and first-order reversal curve (FORC) revealed that the superior strain responses originated from the reversible inter-transformation of substable macrodomains and polar nanoregions (PNRs) in the phase boundary. This study provides new insight into the interplay between the evolution of phase boundaries and domain structures and the strain properties of BNT-based ceramics.

The lead-free piezoelectric ceramics used in piezoelectric actuators have attracted extensive attention owing to their substantial electric-field-induced strain. In this study, The (1- x)Bi 0.5 (Na 0.41 K 0.09)TiO 3 - x Sr(Hf 0.5 Sb 0.4)O 3 (BNKT- x SHS) piezoelectric ceramics were synthesized using the conventional solid-state reaction method. The impact of SHS substitution on the microstructure and electrical properties was systematically explored. Among them, the BNKT-0.015SHS sample, featuring ergodic relaxor states, demonstrates a high piezoelectric strain coefficient (d 33 *) of 785 p.m./V under a low electric field of 50 kV/cm(Strain = 0.392 %). It exhibits a repeatable strain value of 0.47 % under an 80 kV/cm electric field(d 33 * = 590 p.m./V). Moreover, the strain values remain around 0.4 % between room temperature and 100 °C, with variations within 90 %. The heightened repeatable strain response is considered to be linked to the electric field-induced reversible phase transition occurring within the ergodic relaxor state. The higher strain temperature stability is ascribed to the coexistence of quadrilateral polar nanoregions and rhombic polydomain nanoregions. This study provides an effective example for achieving significant strain responses, presenting a feasible candidate material for applications in piezoelectric actuators. [ABSTRACT FROM AUTHOR]

The weak points in a slope often control its deformation and failure mode. Under the action of earthquakes, the complex influence of seismic waves on slopes with cavities is rarely considered. By studying the strain response of this kind of slope, the triggering mechanism of the slope under a strong earthquake can be further discussed. On the basis of the existing research, a shaking table test of a slope model with a cavity structure is carried out. The following conclusions were made: (1) Under the condition of a strong earthquake, the initial crack of the slope with cavities mainly occurs around the cavities, the top of the slope, and the boundary of the slope. (2) During the vibration process, the peak air pressure in a cavity has a good correlation with the peak strain in the surrounding material. The peak strain appears just after the peak air pressure, indicating that the sudden change in the air pressure in the cavity will lead to significant tensile damage to the cavity wall. Repeated air pressure changes in the cavity cause progressive damage to the slope near the cavity structure, accelerating fracture expansion and leading to the fracture penetrating the slope boundary. (3) The overall failure of the slope is somewhat related to the development of cracks around the cavity structure, but failure does not necessarily occur along the cavity zone. The failure site is closely related to the free surface condition and the upper slope structure. [ABSTRACT FROM AUTHOR]

A 5T semi-open split superconducting magnet has been recently developed at the Advanced Energy Science and Technology Guangdong Laboratory, China, in pursuit of a versatile high magnetic field test facility for measuring the field-dependent and mechanical behaviors of superconductors. It is a better candidate to generate transverse fields in a larger working region (Ø80 mm × H800 mm) and enables non-contact deformation measurements with digital image correlation (DIC). In our previous work, the simulation of the strain and the magnetic field distribution of the coil and support structure had been reported in detail; and the strain measurements for the key points were also carried out using traditional low-temperature strain gauges. However, the distributed strain of the large-scale superconducting magnet is important for exploring the whole stability. And single-point strain gauges often have difficulty measuring global strains for these complex structures. In addition, for resistance-based strain gauges, obtaining accurate strain is even more challenging due to electromagnetic interference. Therefore, in this paper, using the semi-open magnet structure, the distributed strain measurement method based on the Optical Frequency Domain Reflectometry (OFDR) principle under cryogenic and intense field is mainly validated. The global profile of the magnet system strain was monitored throughout the entire operating process, including cool-down, excitation, and warm-up. The distributed fiber strain measurements agree well with traditional single-point resistance measurements. Interesting insights into the global strain characteristics of semi-open split superconducting structures were obtained, such as the catastrophe data and asymmetrical information. The successful application of distributed fiber strain measurements provides a critical distributed detection method in superconducting magnet technology. [ABSTRACT FROM AUTHOR]

Association football, also known as soccer in some regions, is unique in encouraging its participants to intentionally use their head to gain a competitive advantage, including scoring a goal. Repetitive head impacts are now being increasingly linked to an inflated risk of developing long-term neurodegenerative disease. This study investigated the effect of heading passes from different distances, using head acceleration data and finite element modelling to estimate brain injury risk. Seven university-level participants wore a custom-fitted instrumented mouthguard to capture linear and angular acceleration-time data. They performed 10 headers within a laboratory environment, from a combination of short, medium, and long passes. Kinematic data was then used to calculate peak linear acceleration, peak angular velocity, and peak angular acceleration as well as two brain injury metrics: head injury criterion and rotational injury criterion. Six degrees of freedom acceleration-time data were also inputted into a widely accepted finite element brain model to estimate strain-response using mean peak strain and cumulative strain damage measure values. Five headers were considered to have a 25% concussion risk. Mean peak linear acceleration equalled 26 ± 7.9 g, mean peak angular velocity 7.20 ± 2.18 rad/s, mean peak angular acceleration 1730 ± 611 rad/s2, and 95th percentile mean peak strain 0.0962 ± 0.252. Some of these data were similar to brain injury metrics reported from American football, which supports the need for further investigation into soccer heading. [ABSTRACT FROM AUTHOR]

A systematic investigation of the temperature dependent strain property in 0.5Bi(Mg 1/2 Ti 1/2)O 3 -0.2 Pb(Mg 1/3 Nb 2/3)O 3 -0.3PbTiO 3 (0.5BMT-0.2PMN-0.3 PT) ceramic was performed in this work. Generally, the temperature dependent strain evolution was found to be seriously related to the electric field (E), i.e., with increasing temperature, a monotonic increase in the strain was observed in the low field range (E ≤ 2 kV/mm), a first increase and then decrease in the strain was observed in the middle field range (2< E ≤ 4 kV/mm), and temperature insensitive strain was obtained in the high field range (E > 4 kV/mm). The temperature and electric field dependent evolution of the phase structure was investigated by in-situ synchrotron X-ray diffraction. Overall, the different strain behaviors observed at different temperatures and electric fields are believed to be related to the stability of different phase structures at varying temperatures and electric fields. [ABSTRACT FROM AUTHOR]

Temperature load is one of the most common and vital environmental loads for bridge in-service. However, the significant variability of temperature and the time-lag effect severely affects the damage identification and structure evaluation based on temperature response. The time-lag effect refers to the phenomenon that the temperature-induced response lags behind the temperature itself. Through a large amount of measured data mining, this paper summarizes the typical characteristics and general laws of the time-lag effect. Besides, the numerical simulation of the time-lag effect is realized via the finite element method. Furthermore, the spatial and temporal mechanism of the time-lag effect is explored. The extensive numerical simulation results and measured data verification revealed that the temperature change rate is the root cause of the time-lag effect. And the time delay of temperature-induced strain is just the appearance. Finally, based on the mechanism of the time-lag effect, an elimination method is proposed, which adopts the temperature change rate and temperature amplitude as key indexes. With this method, the stable slope of temperature-induced strain can be gained. This provides a solid basis for further structural evaluation based on the temperature effect. The exploration of the time-lag effect mechanism deepens the understanding of the temperature response and provides a new perspective for the structural early warning and assessment based on temperature load. [ABSTRACT FROM AUTHOR]

Deflection measurements are usually used as a key index in civil engineering for performing structural assessments of bridge safety. However, owing to technical or cost issues, it may be difficult to implement long-term monitoring of bridge deflection, especially for short- or medium-span bridges. Therefore, this study presents a novel method for measuring the deflection of simply supported girder bridges. In the proposed method, the strain measurement was implemented under traffic loading at only one position, such as middle span, and then the strain distribution along the girder was reconstructed to calculate the girder deflection with basic structural mechanical theory. To implement the method, the theory was constructed based on the displacement reciprocal theorem at first to assess the strain distribution along the girder from the strain measurement at some position during traffic loads passing across the bridge. Second, a strain measurement method, namely long-gauge fibre Bragg grating (FBG) sensing technology, was introduced to take strain measurements for a concrete bridge. Third, various finite element (FE) bridge models were developed to validate the proposed method's accuracy, the results from which indicated that the method accurately implemented deflection measurement with an approximately 5% calculation error. In addition, the influence of some key parameters, such as vehicle type, vehicle speed, and structural damage, was investigated. The simulation results revealed that damage to the hinge joint in the middle location could significantly influence the proposed method's accuracy such that the error may exceed 10%. Finally, on-site experiments were conducted on a simply supported girder bridge to further validate the proposed method's accuracy, and an approximately 8% deflection assessment error was found. Considering the additional advantages of FBG sensing technology, the proposed method can also be effective for long-term deflection measurements of short- or medium-span bridges. [ABSTRACT FROM AUTHOR]

Lead-free (Bi 0.5 Na 0.5)TiO 3 (BNT)-based piezoelectric materials, have a great potential for high-precision actuators' applications. In this work, the high-quality (0.94- x %)(Bi 0.5 Na 0.5)TiO 3 -0.06BaTiO 3 - x %NaNbO 3 (x = 2–10, BNT-6BT- x NN) thin films have been successfully deposited on Pt/TiO 2 /SiO 2 /Si substrates by sol-gel method. An ultra-high poling strain S pol value of 1.7% with a unipolar strain S uni value of 1.47% was reported in the BNT-6BT-6NN thin films. The coexistence of the ferroelectric phase and relaxor state was observed in the compositions of x = 2–8. Furthermore, the BNT-6BT-6NN thin films show more active domain switching compared to other compositions. It is demonstrated that the optimized strain responses in the BNT-6BT-6NN are attributed to a synergistic reaction of active domain switching and reversible electric-field-induced phase transition between the ferroelectric phase and relaxor state. Our systematic study demonstrates that the BNT-6BT- x NN thin films with an improved strain response are promising candidates for the applications of miniaturized actuators. [ABSTRACT FROM AUTHOR]

High‐performance piezoelectric materials are essential in many piezoelectric devices. However, the composition of piezoelectric materials usually has a great influence on their performance. In this work, xBi(Mg1/2Ti1/2)O3–yPbZrO3–zPbTiO3 (xBMT–yPZ–zPT; 0.2 ≤ x ≤ 0.4, 0.25 ≤ y ≤ 0.4, and 0.35 ≤ z ≤ 0.4) ternary ceramics with different compositions were synthesized and it was found that the strain response was not sensitive to the composition. The crystal structure, strain response, ferroelectric properties, and temperature stability of xBMT–yPZ–zPT ceramics were investigated in detail. X‐ray diffraction patterns show that all the as‐prepared xBMT–yPZ–zPT ceramics with x = 0.2, 0.3, 0.4, and 0.5 possess a perovskite structure. Under an external electric field of 6 kV mm−1, the strain values of xBMT–yPZ–zPT ternary ceramics with x = 0.2, 0.3, 0.4, and 0.5 were 0.30%, 0.31%, 0.30%, and 0.27%, respectively. In addition, the strain hysteresis of these ternary ceramics is also almost the same and low. These merits make xBMT–yPZ–zPT piezoelectric ceramics have broad application prospects in the field of commercial actuators. [ABSTRACT FROM AUTHOR]

Deepsea mining risers, which transport mineral resources from the seafloor to surface facilities, are critical components of deepsea mining systems. This article presents a novel cointegration-based method for localizing structural damage in risers subjected to random excitations from waves, currents, and moving floating facilities. Although the dynamic responses of a riser (usually consisting of multiple segments) are often nonstationary, those within an individual pipe segment often have synchronous fluctuations with a common trend, allowing the application of a multivariate time series analysis. Cointegration can thus be performed for a pipe segment by treating the internal responses as the endogenous variables and those of the other pipe segments as the exogenous variables. Consequently, a stationary cointegrating residual for the dynamic responses purged of the influence of nonstationary excitations can be obtained. The cointegrating residual in conjunction with a statistical hypothesis test scheme is used to create an output-only damage indicator. The effectiveness of the proposed damage localization method is demonstrated with a numerical and experimental multi-segment riser. The results indicate that the strain responses of both risers exhibit nonstationary fluctuations due to the changeable environmental excitations. As the proposed method is robust to the external loading, it can accurately identify the damage location. [ABSTRACT FROM AUTHOR]

To establish a restoring force model for recycled aggregate concrete‐filled steel tube (RACFST) frames, the quasistatic tests on two frames comprising two RACFST columns and a reinforced recycled aggregate concrete (RRAC) beam each was carried out. The recycled coarse aggregate replacement ratio was 100%. The failure mechanism, hysteretic curves, and strain response of the specimens were discussed. By analyzing the degradation of the load bearing capacity with increasing displacement amplitude and combining the hysteretic curves and stiffness degradation relationships, a restoring force model of load versus displacement adopting a trilinear approximation was proposed. The characteristic points of the model were the relative yield point, relative peak point, and relative failure point. Results showed that bending‐shear or bending failure occurred at the ends of specimen beams and plastic hinges formed there earlier than at the column ends. The hysteretic curves of load versus displacement were essentially symmetric in a full shuttle shape. The proposed restoring force model adopting trilinear approximation agreed well with the experimental hysteretic curves under low‐cycle loading and can thus be recommended to perform the elastoplastic analysis of seismic response for this new type of composite structures. [ABSTRACT FROM AUTHOR]

Abstract The load spectrum is a crucial factor for assessing the fatigue reliability of in-service rolling element bearings in transmission systems. For a bearing in a high-speed train gearbox, a measurement technique based on strain detection of bearing outer ring was used to instrument the bearing and determine the time histories of the distributed load in the bearing under different gear meshing conditions. Accordingly, the load spectrum of the total radial load carried by the bearing was compiled. The mean value and class interval of the obtained load spectrum were found to vary non-monotonously with the speed and torque of gear meshing, which was considered to be caused by the vibration of the shaft and the bearing cage. As the realistic service load input of bearing life assessment, the measured load spectrum under different gear meshing conditions can be used to predict gearbox bearing life realistically based on the damage-equivalent principle and actual operating conditions.

Strain sensor play an irreplaceable role in monitoring the structural response of asphalt pavements. The effective synergistic deformation of sensor and pavement structure is a key foundation to ensure accurate sensor measurements. The differences between sensor and pavement material lead to complex synergistic deformation between them. Therefore, this study intends to investigate the factors that influence the synergistic deformation of the sensor and the asphalt mixture under different operating conditions. The aim is to reveal the working mechanism of sensor and asphalt mixture synergistic deformation and improve the application value of the measured sensor data. Firstly, by using digital image correlation (DIC) technology and direct tensile beam test, a new test method was designed for the synergistic deformation evaluation of sensor and asphalt mixture. Then, the strain response test was carried out on the asphalt mixture specimens with built-in strain sensor under different stress modes such as multi-stress tension axial compression, tension-compression alternation and sinusoidal cycle. Finally, the numerical value monitored by DIC technology was used as strain reference value to calculate the measurement error of the sensor, and then to analyze the evolution of the synergistic deformation of strain sensor and asphalt mixture. The results show that loading mode and magnitude, temperature and sensor position deviation are the key factors that affect the deformation compatibility between the sensor and the asphalt mixture. The loading frequency has less influence on deformation compatibility. The average absolute error E̅a of the sensor measurement increases as the load increases. The measured strain response shows the opposite measurement deviations under multi-stress tension and axial compression. The strain response accuracy of the sensor drops sharply at high temperatures of 30 °C∼50 °C. At this time, the average absolute error of measurement E̅a and the relative error E̅r can be increased by 3.49–11.79 times and 2.01–2.91 times, respectively. The working environment temperature of the high modulus strain sensor in collaboration with the asphalt pavement should be below 30 °C. Deflection of the position of the embedded sensor will cause the measured value to be smaller. When the deflection angle is 12°, the measurement error of the sensor can be increased by 2.43–5.46 times under the same load. The results provide an important reference for solving the technical problems of incompatibility between built-in strain sensor and asphalt pavement, and promoting the sensor technology to deeply enable traditional asphalt pavement structures.

Bismuth sodium titanate (Bi0.5Na0.5)TiO3 (BNT)–based thin films have attracted large attention for the production of modern precise micro–devices due to their outstanding strain responses. However, obtaining good electrical properties and low leakage current in BNT-based thin films is still a great challenge. In this work, 0.945(Bi0.5Na0.5)TiO3–0.055BaZrO3 (BNT–5.5BZ) thin films were deposited by the chemical solution deposition (CSD) method and annealed under two different conditions. This work describes a careful research study on the influence of the annealing conditions on the crystalline structure, morphology, and electrical performance of the BNT–5.5BZ thin films. The films exhibited a dense structure and excellent electrical properties following an optimized thermal treatment process. An ultra–high strain response of 1.5% with a low dielectric loss of ~0.03 was obtained in the BNT–5.5BZ thin films after post-annealing in an O2 atmosphere. The results of this work show that the enhanced strain response was mainly due to a reversible field-induced phase transition between the ferroelectric phase and the relaxation state. The post-annealing treatment is an effective method to optimize the electrical properties of BNT–based films, providing many opportunities for the application of ferroelectric devices. [ABSTRACT FROM AUTHOR]

Developing polymorphic phase coexistence near room temperature in potassium sodium niobate-based piezoceramics is a widespread way to improve strain performance. Herein, 0.97(K 0.48 Na 0.52) 1-3 x La x NbO 3 -0.03SrTiO 3 piezoceramics were studied by analyzing their grain images, crystal structures, dielectric properties, Raman spectra, ferroelectric properties, strain responses, and piezoelectric properties. A high strain of 0.43% was achieved at x = 0.0050 presenting a diffuse phase transition state, due to various intrinsic factors, including large electrostriction, small piezoelectric effects, and extrinsic microdomain wall reorientation. The large electrostriction was the chief contribution to the strain due to the considerable electrostrictive coefficient (Q 33) of 0.039 m4/C2. Furthermore, the considerable Q 33 was due to B-site shifting by distorting the slightly compressed NbO 6 octahedron arising from La3+ doping. The compressed of the NbO 6 octahedra was proven by XRD results and generated distortion according to the obtained Raman spectra. [ABSTRACT FROM AUTHOR]

This paper presents the development of a large-scale tunnel model using an innovative loading device, which is then subjected to longitudinal seismic response analysis through a shaking table test. The loading device, designed to support the tunnel with springs, applies seismic loads from the shaking table and simulates the soil-structure interaction. Initially, the rationality and accuracy of the loading device were validated through numerical and analytical methods. Experimental results reveal that, under various seismic excitations, the acceleration response is significantly lower at the tunnel ends compared to the middle. The tensile strain response at the arch waist exhibits a U-shaped deformation along the longitudinal axis, while the compressive strain response exhibits a bending deformation with multiple inflection points. Furthermore, both tensile and compressive strain responses at the arch bottom show more pronounced bending deformations along the longitudinal direction. The findings indicate that the peak value of the input seismic excitation does not alter the deformation pattern of the tunnel. Within the longitudinal length L of the tunnel, the tensile zone reaches a maximum strain value ε max , whereas the compressive zone reaches a minimum strain value ε min. These experimental insights offer valuable references for the seismic design of tunnels. • An innovative loading device was designed and developed based on shaking table. • The large-scale model can more accurately capture the seismic response of the tunnel. • The test results reveal the deformation patterns of a large-scale tunnel model. • The loading device and experimental method can be applied to underground structures. [ABSTRACT FROM AUTHOR]

Dynamic load identification is crucial for structural design and health monitoring. Traditional methods for distributed dynamic loads (DDLs) typically involve establishing a transfer matrix, which often leads to ill-posed problems. In this paper, a novel method based on the inverse Finite Element Method (iFEM) and radial basis function (RBF) fitting was proposed to identify DDLs from measured strain responses. The method begins with the reconstruction of the displacement field from discrete strain data using iFEM, followed by applying RBF fitting to obtain a continuous displacement field. To enhance the performance of the RBF fitting, a constrained matrix for force boundary conditions is introduced, along with a selection rule for the RBF shape parameter. The identified loads are subsequently determined by incorporating the well-fitted RBFs into the motion equations of thin plates. This approach eliminates the need for a transfer matrix, thereby avoiding ill-posedness, and enables the simultaneous identification of the spatial distribution and time history of the loads. Three numerical examples for the identification of concentrated loads, uniformly distributed loads, and globally distributed loads demonstrate the method's effectiveness, accuracy, and noise resistance, with additional validation provided through a comparison with the classic time-domain method. • The iFEM provides a new solution for identifying loads utilizing strain signals. • RBF fitting is enhanced by a constrained matrix and shape parameter selection rule. • Motion equation prevents load decoupling and ill-posed matrix issues. • Spatial and temporal noise simulate material heterogeneity and measurement errors. • Effects of shape parameter, element count, noise, and load diffusion are detailed. [ABSTRACT FROM AUTHOR]

Deflection measurements are usually used as a key index in civil engineering for performing structural assessments of bridge safety. However, owing to technical or cost issues, it may be difficult to implement long-term monitoring of bridge deflection, especially for short- or medium-span bridges. Therefore, this study presents a novel method for measuring the deflection of simply supported girder bridges. In the proposed method, the strain measurement was implemented under traffic loading at only one position, such as middle span, and then the strain distribution along the girder was reconstructed to calculate the girder deflection with basic structural mechanical theory. To implement the method, the theory was constructed based on the displacement reciprocal theorem at first to assess the strain distribution along the girder from the strain measurement at some position during traffic loads passing across the bridge. Second, a strain measurement method, namely long-gauge fibre Bragg grating (FBG) sensing technology, was introduced to take strain measurements for a concrete bridge. Third, various finite element (FE) bridge models were developed to validate the proposed method’s accuracy, the results from which indicated that the method accurately implemented deflection measurement with an approximately 5% calculation error. In addition, the influence of some key parameters, such as vehicle type, vehicle speed, and structural damage, was investigated. The simulation results revealed that damage to the hinge joint in the middle location could significantly influence the proposed method’s accuracy such that the error may exceed 10%. Finally, on-site experiments were conducted on a simply supported girder bridge to further validate the proposed method’s accuracy, and an approximately 8% deflection assessment error was found. Considering the additional advantages of FBG sensing technology, the proposed method can also be effective for long-term deflection measurements of short- or medium-span bridges.

In order to explore the influences of effective stress change on gas adsorption–desorption behaviors, primary undeformed coal (PUC) and tectonically deformed coal (TDC) from the same coal seam were used for adsorption–desorption experiments under different effective stress conditions. Experimental results showed that gas adsorption and desorption behaviors were controlled by the coal core structure and the pore-fissure connectivity under effective stress. The coal matrixes and fissures were compressed together under effective stress to reduce connectivity, and it was difficult for gas to absorb and desorb as the stress increased in primary undeformed coal. The loose structure of tectonically deformed coal cores can help gas to fully contact with the coal matrix, resulting in higher adsorption gas volumes. The support of coal particles in tectonically deformed coal cores weakens the compression of intergranular pores when effective stress increases, which in this study manifested in the fact that while the volumetric strain of the coal matrix change rapidly under low effective stress, but the adsorbed gas volume did not decrease significantly. The reduction in effective stress induced the rapid elastic recovery of the coal matrix and the expansion of cracks, and increased desorption gas volumes. The stress reduction significantly increased the initial gas volume of the tectonically deformed coal, while promoting slow and continuous gas desorption in primary undeformed coal. Therefore, the promotion effect of the reservoir pressure reduction on gas desorption and coal connectivity enhancement can help to improve coalbed methane recovery in primary undeformed coal and tectonically deformed coal reservoirs. [ABSTRACT FROM AUTHOR]

This study aims to reveal the buckling behavior of filament-wound composite cylindrical shells subjected to external pressure. The boundary conditions of the cylindrical shells were one end fixed and the other free. The carbon fiber stacking sequences were [±90]2/([±20]/[±90]/[±40]/[±90]/[±60]/[±90])2/[±90]. Finite element software ANSYS 16.2 was used for the numerical simulation to predict the critical buckling pressure and buckling behavior of composite cylindrical shell. External hydrostatic pressure tests were conducted, where the buckling behavior and strain response were observed. Numerical simulation accurately predicted the critical buckling pressure of carbon fiber/epoxy filament composite cylindrical shells under external pressure with 3.5% deviation from the experimental results. The buckling modes simulated by the finite element method agreed well with the deformed shape observed in the experiment, which was characterized by the uniform distribution of the three hoop waves. Comparing the axial compressive strain and hoop compressive strain of the composite shell, it was found that the circumferential stiffness of the shell was weaker than the axial stiffness. In addition, a comparative study of the strains of the fixed-end and free-end metal control sleeves was carried out. The results show that the boundary conditions have a significant influence on the strain response of control sleeves. [ABSTRACT FROM AUTHOR]

The occurrence of a buried submarine pipeline crossing a channel becoming damaged by the impact of a falling anchor is becoming more common. It is important to analyze the dynamic response of pipelines exposed to such impact and develop effective protection methods to ensure the safe operation of the pipelines exposed to the impact of falling anchors. In this study, different protection methods, including pure rock, concrete mattress + rock, concrete mattress + rock + rubber pad, and compound flexible pad + rock, are physically tested. The strains at the impacting point and along the pipeline were measured with the fiber Bragg grating (FBG) sensors. The effectiveness of the protection methods is analyzed based on the maximum strain and its affected length on the pipeline. Then, a theoretical model is established to analyze the deformation and strain of a pipeline. Through curve-fitting the experimental results, the bearing capacity coefficients for different protection methods are determined. The protection method of compound flexible pad + rock has the best performance to protect the pipeline from the impact of a falling anchor. [ABSTRACT FROM AUTHOR]

Bismuth sodium titanate (Bi0.5Na0.5)TiO3 (BNT)–based thin films have attracted large attention for the production of modern precise micro–devices due to their outstanding strain responses. However, obtaining good electrical properties and low leakage current in BNT-based thin films is still a great challenge. In this work, 0.945(Bi0.5Na0.5)TiO3–0.055BaZrO3 (BNT–5.5BZ) thin films were deposited by the chemical solution deposition (CSD) method and annealed under two different conditions. This work describes a careful research study on the influence of the annealing conditions on the crystalline structure, morphology, and electrical performance of the BNT–5.5BZ thin films. The films exhibited a dense structure and excellent electrical properties following an optimized thermal treatment process. An ultra–high strain response of 1.5% with a low dielectric loss of ~0.03 was obtained in the BNT–5.5BZ thin films after post-annealing in an O2 atmosphere. The results of this work show that the enhanced strain response was mainly due to a reversible field-induced phase transition between the ferroelectric phase and the relaxation state. The post-annealing treatment is an effective method to optimize the electrical properties of BNT–based films, providing many opportunities for the application of ferroelectric devices.

Cantilever structure, which needs high-frequency rotating motion, is widely used in the field of chip manufacturing. The motion stability of high-frequency rotation motion of cantilever structure directly affects the production efficiency. The traditional dynamic analysis method is no longer applicable to analyze the vibration of cantilever structure under high-frequency rotating motion. It is also urgent to control the high-frequency rotation motion of cantilever mechanism. In this paper, experiments are designed to collect strain signals of chip sorter's cantilever under high-frequency operation, and modal parameters are extracted from time domain signals by symbolic regression algorithm. The results of modal parameter identification at high-frequency are selected as the samples, and the Gaussian process regression model of machine learning algorithm is used to train the samples. The prediction results can be used as the basis of structural stability research and vibration suppression. [ABSTRACT FROM AUTHOR]

• Highly <001> oriented BMT-PMN-PT textured ceramics were fabricated by template grain growth. • The crystal structure, microstructure, and dielectric, ferroelectric and strain properties of textured ceramics were systematically studied. • A large strain of 0.42 % at 4 kV/mm was obtained in 0.25BMT-0.45PMN-0.3PT textured ceramics. • The strain of BMT-PMN-PT textured ceramics have a relatively high thermal stability. <001> oriented x Bi(Mg 1/2 Ti 1/2)O 3 -(0.7- x)Pb(Mg 1/3 Nb 2/3)O 3 -0.3PbTiO 3 (BMT-PMN-PT) textured ceramics are successfully fabricated by the template grain growth method using BaTiO 3 platelets as template. BMT-PMN-PT textured ceramics with different BMT contents are studied in terms of crystal structure, microstructures, dielectric and ferroelectric properties, and electric field induced strain. The as-fabricated BMT-PMN-PT textured ceramics were found to have a strong orientation along <001> direction. The frequency dispersion of dielectric constant of BMT-PMN-PT textured ceramics increases gradually and its relaxability becomes stronger with increasing BMT content. A large electric-field induced strain (0.42 % at 4 kV/mm) is obtained in 0.25BMT-0.45PMN-0.3PT textured ceramics with Lotgering factor 0.94, which is about 83 % enhancement than that of the randomly oriented ceramics (0.23 % at 4 kV/mm). The strain of 0.25BMT-0.45PMN-0.3PT textured ceramics have a relatively high thermal stability, with a slight decrease from 0.42 % to 0.28 % in the temperature range of 20−100 °C. Our research suggests that 0.25BMT-0.45PMN-0.3PT textured ceramics have a greatly potential for actuator devices applications owing to its advantages of large electric field induced strain response. [ABSTRACT FROM AUTHOR]

• The novel application of FRP-OFBG bars for structural monitoring of maglev guideway PC girders is demonstrated. • The effectiveness of FRP-OFBG bars was verified by static load test to reflect the elasticity and damage stages of PC girders. • The reliability of FRP-OFBG bars was established by comparing and analyzing the strain response of multiple sensors. The prestressed concrete (PC) girder serves as the main load-bearing and force-transmitting structure of the medium–low-speed maglev line and plays a key role in ensuring the safe and reliable operation of maglev trains. This research demonstrates the novel application of Fiber Reinforced Polymer-Optical Fiber Bragg Grating (FRP-OFBG) bars in the structural monitoring of the PC girder and also expands the forms and fields of self-sensing concrete application. Embedded within the PC girder, FRP-OFBG bars were validated to effectively track the structural changes of the PC girder through static load tests complemented by finite element simulations. The reliability of FRP-OFBG bars was further illustrated by comparative analysis with the strain response of concrete strain gauges and surface strain gauges. In the future, FRP-OFBG bars are expected to become a vital supplementary tool for the structural health monitoring of maglev guideway PC girders during actual operation. [ABSTRACT FROM AUTHOR]

In order to explore the influences of effective stress change on gas adsorption–desorption behaviors, primary undeformed coal (PUC) and tectonically deformed coal (TDC) from the same coal seam were used for adsorption–desorption experiments under different effective stress conditions. Experimental results showed that gas adsorption and desorption behaviors were controlled by the coal core structure and the pore-fissure connectivity under effective stress. The coal matrixes and fissures were compressed together under effective stress to reduce connectivity, and it was difficult for gas to absorb and desorb as the stress increased in primary undeformed coal. The loose structure of tectonically deformed coal cores can help gas to fully contact with the coal matrix, resulting in higher adsorption gas volumes. The support of coal particles in tectonically deformed coal cores weakens the compression of intergranular pores when effective stress increases, which in this study manifested in the fact that while the volumetric strain of the coal matrix change rapidly under low effective stress, but the adsorbed gas volume did not decrease significantly. The reduction in effective stress induced the rapid elastic recovery of the coal matrix and the expansion of cracks, and increased desorption gas volumes. The stress reduction significantly increased the initial gas volume of the tectonically deformed coal, while promoting slow and continuous gas desorption in primary undeformed coal. Therefore, the promotion effect of the reservoir pressure reduction on gas desorption and coal connectivity enhancement can help to improve coalbed methane recovery in primary undeformed coal and tectonically deformed coal reservoirs.

This study aims to reveal the buckling behavior of filament-wound composite cylindrical shells subjected to external pressure. The boundary conditions of the cylindrical shells were one end fixed and the other free. The carbon fiber stacking sequences were [±90]2/([±20]/[±90]/[±40]/[±90]/[±60]/[±90])2/[±90]. Finite element software ANSYS 16.2 was used for the numerical simulation to predict the critical buckling pressure and buckling behavior of composite cylindrical shell. External hydrostatic pressure tests were conducted, where the buckling behavior and strain response were observed. Numerical simulation accurately predicted the critical buckling pressure of carbon fiber/epoxy filament composite cylindrical shells under external pressure with 3.5% deviation from the experimental results. The buckling modes simulated by the finite element method agreed well with the deformed shape observed in the experiment, which was characterized by the uniform distribution of the three hoop waves. Comparing the axial compressive strain and hoop compressive strain of the composite shell, it was found that the circumferential stiffness of the shell was weaker than the axial stiffness. In addition, a comparative study of the strains of the fixed-end and free-end metal control sleeves was carried out. The results show that the boundary conditions have a significant influence on the strain response of control sleeves.

The occurrence of a buried submarine pipeline crossing a channel becoming damaged by the impact of a falling anchor is becoming more common. It is important to analyze the dynamic response of pipelines exposed to such impact and develop effective protection methods to ensure the safe operation of the pipelines exposed to the impact of falling anchors. In this study, different protection methods, including pure rock, concrete mattress + rock, concrete mattress + rock + rubber pad, and compound flexible pad + rock, are physically tested. The strains at the impacting point and along the pipeline were measured with the fiber Bragg grating (FBG) sensors. The effectiveness of the protection methods is analyzed based on the maximum strain and its affected length on the pipeline. Then, a theoretical model is established to analyze the deformation and strain of a pipeline. Through curve-fitting the experimental results, the bearing capacity coefficients for different protection methods are determined. The protection method of compound flexible pad + rock has the best performance to protect the pipeline from the impact of a falling anchor.

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Summary: Research on structural health monitoring (SHM) is nowadays evolving from SHM‐based diagnosis towards SHM‐based prognosis. The structural strain response, as a localized response, has gained growing attention for application to structural condition assessment and prognosis in that continuous strain measurement can offer information about the stress experienced by an in‐service structure and is better suited to characterize local deficiency and damage of the structure than global responses. As such, accurate forecasting of the structural strain response in real time is essential for both structural condition diagnosis and prognosis. In this paper, a Bayesian modeling approach embedding model class selection is proposed for dynamic forecasting purpose, which enables the probabilistic forecasting of structural strain response and bears a strong capability of modeling the underlying non‐stationary dynamic process. As opposed to the classical time series models, the proposed Bayesian dynamic linear model (BDLM) accommodates both stationary and non‐stationary time series data and delineates the time‐dependent structural strain response through invoking different hidden components, such as overall trend, seasonal (cyclical), and regressive components. It in turn paves an effective way for incorporating the newly observed time‐variant data into the model framework for structural response prediction. By embedding a novel model class selection paradigm into the BDLM, the proposed algorithm enables simultaneous model class selection and probabilistic forecasting of strain responses in a real‐time manner. The utility of the proposed approach and its forecasting accuracy are examined by using the real‐world monitoring data successively collected from a three‐tower cable‐stayed bridge. [ABSTRACT FROM AUTHOR]

Although the cage slip of cylindrical roller bearings has been measured and studied experimentally, it is difficult to use current experimental measurement to detect the cage slip of the bearing in actual service or engineering environment. The problem is attributed to the limit on the space for current test instruments that can be installed arbitrarily in laboratory, but not in actual environment. A novel measurement based on strain detection is presented. This measurement can be used to obtain the cage slip of the bearing in service or large bench test. The technique is demonstrated and validated in principle by an experimental system. The system is developed to obtain the strain signal of the outer ring in loaded zone as well as the speed signal of the cage and the inner ring at the same time. Under given test load–speed conditions, the cage slip based on strain detection was compared with the cage slip based on speed detection. Experimental results showed that cage slip ratio curves based on strain responses agreed very well with those based on speed signals. In this way, it is revealed that frequency characteristics of strain signals can be used to obtain internal cage slip of cylindrical roller bearings. [ABSTRACT FROM AUTHOR]

• Mechanical properties of superconducting magnet insulation materials after reheat. • Strain responses during second Vacuum Pressure Impregnation process. • Monitoring by Fiber Bragg Grating sensors embedded in the insulation layers. • Additional strain introduced by the new added epoxy resin. In large-scale, high-field superconducting magnets used for magnetic confinement fusion, high energy accelerators, and magnetic resonance imaging, the insulating system made from glass fiber reinforced resin-based composites is the key component, which mainly plays the role of mechanical support, fixing and protecting superconducting conductors, as well as electrical insulation. Vacuum Pressure Impregnation (VPI) approach is widely used in the manufacturing of the insulation system. The second curing cycle is generally required after the first VPI and curing process. For example, after the superconducting coil is cured in the mold, the de-molding process requires the superconducting coil to be reheated according the curing temperature. Moreover, for large-scale superconducting magnets, the superconducting coil needs to undergo a second VPI process after the first VPI process to fix the coil in the coil case. In this work, the tensile and shear properties of pure epoxy resin and the glass fiber reinforced resin-based composite, were investigated at both room and cryogenic temperatures and the effect of the second curing cycle on the mechanical properties was analyzed. Additionally, the strain evolution of the Nb-Ti superconducting coil during the second curing cycle was measured using the Fiber Bragg Grating (FBG) sensors embedded in the composite. The results indicate that the second curing cycle will not introduce additional strain to the previously cured resin matrix, but the defective or weak parts of the resin matrix may be affected by the new added epoxy resin and a little extra strain has been observed. [ABSTRACT FROM AUTHOR]