Real-time Deformation Research Articles

Development of laser-based displacement monitoring system and its application to large-scale spatial structures

Proper deformation process is essential for forming the shape of cable net structures during construction. This highlights the importance of identifying uneven and excessive deformation when building large-scale cable net structures. As such, the deformation of large-scale cable net structures should be accurately monitored in a real-time manner during the construction process. This study is to develop a laser-based displacement monitoring system for tracing the real-time deformation of large-scale spatial structures. The developed displacement monitoring system combines wireless sensor networks (WSN) and laser ranging technology. The laser-based displacement monitoring system is implemented on the National Speed Skating Oval (NSSO), which is a large-scale cable net structure, to obtain the relative displacement change between the cable net structure and the supporting system. On the other hand, the finite element (FE) model of the NSSO is established to simulate the deformation process. Then, the measured displacement results are compared with the FE model-derived counterparts. It is shown that the simulated and measured results have a good agreement, which indicates the effectiveness of the laser-based displacement monitoring system.

An Improved Inertial Matching Algorithm for Hull Deformation With Large Misalignment Angle

Inertial matching measurement method has been widely used to measure hull deformation in real time to establish a unified attitude reference for ships in previous decades, but most current methods were based on linear error model which adopted small angle approximation. Therefore, the large misalignment angle in the hull deformation will bring great challenges to the accuracy of inertial matching measurement methods. In order to solve this problem, we divided the hull deformation with large misalignment angle into two parts: large angle based on coarse registration and small angle of the residual part. Three improvements were made as the following: (1) The quaternion optimization method (Q) was utilized to get the coarse registration result; (2) Based on the result, we derived a brand-new residual small-angle measurement algorithm. (3) We introduced neural network Karman filter (NNKF) to calculate the hull deformation in real time to further reduce the nonlinear error of the system. The experiment results illustrated that the proposed method, namely, Q-NNKF, can accurately measure the hull deformation in real time and effectively suppressed the nonlinear error caused by large misalignment angle.

Joint time–frequency mask and convolutional neural network for real-time separation of multipath in GNSS deformation monitoring

As one of the leading technologies of real-time dynamic deformation monitoring, global navigation satellite system (GNSS) has been widely used in deformation monitoring. Multipath error is the primary error source that limits the application of GNSS high-precision deformation monitoring, which cannot be eliminated by the double-differenced technique. It is a problem to separate and mitigate multipath in the GNSS deformation monitoring series in real-time. Therefore, we propose an approach to solve this problem, named time–frequency mask and convolutional neural network (TFM–CNN). The specific processes are as follows: (1) TFM–CNN network construction. We add a full-band deformation to the multipath and obtain the spectrogram of the signal by the short-time Fourier transform (STFT); meanwhile, the ideal ratio mask (IRM) is used to obtain the corresponding time–frequency mask matrix based on the spectrogram; furthermore, one-dimensional CNN mines the mapping relationship between the spectrogram and the time–frequency mask matrix. (2) Multipath separation. We obtain the spectrogram of the GNSS real-time deformation monitoring series by STFT. Then, we estimate its time–frequency mask matrix by the network. The matrix is multiplied by the spectrogram of the monitoring series to obtain the spectrogram of the multipath. Finally, we perform the inverse STFT to obtain the multipath in the GNSS monitoring series. The experimental results show that by training GNSS data in only a specific direction (such as the north direction), the mapping relationship between the spectrogram of multipath and the time–frequency mask matrix can be obtained, which can effectively separate multipath of the GNSS monitoring series in different observation environment in real-time. TFM-CNN significantly improves the monitoring accuracy and achieves millimeter level dynamic deformation monitoring.

Intelligent Early Warning System for Construction Safety of Excavations Adjacent to Existing Metro Tunnels

With the increasing exploitation and utilization of underground spaces, the excavation of deep foundation pits adjacent to existing metro tunnels is becoming increasingly common. These excavations have the potential to cause safety problems for the operation of the nearby metro. Therefore, to prevent metro tunnel accidents from occurring during the construction process and to ensure the safety of lives and property, it is necessary to establish a risk‐based early warning system. During the excavation process, the main methods for preventing accidents in excavations adjacent to existing metro tunnels are manual analyses based on on‐site monitoring data. However, these methods make it difficult to enact effective control measures in a timely manner owing to the lag of information processing. However, the trial application of artificial neural networks (ANNs) and building information modelling (BIM) for engineering projects provides a new method for solving such problems. This study uses a backpropagation neural network to predict the real‐time deformation of the tunnel based on monitoring data from the adjacent construction site. A safety risk assessment model is then established based on the relevant specifications. Through the establishment of an intelligent warning system, the safety risk to the metro tunnel during the construction process can be displayed in a three‐dimensional (3D) form using the BIM. The operation results of the ANN–BIM system show that it can effectively present the safety risk to existing metro tunnels in a 3D manner, which can provide managers with rapid and convenient visual information to inform their decision‐making.

Deformation Prediction of Unstable Slopes Based on Real-Time Monitoring and DeepAR Model.

With increased urbanization, accidents related to slope instability are frequently encountered in construction sites. The deformation and failure mechanism of a landslide is a complex dynamic process, which seriously threatens people’s lives and property. Currently, prediction and early warning of a landslide can be effectively performed by using Internet of Things (IoT) technology to monitor the landslide deformation in real time and an artificial intelligence algorithm to predict the deformation trend. However, if a slope failure occurs during the construction period, the builders and decision-makers find it challenging to effectively apply IoT technology to monitor the emergency and assist in proposing treatment measures. Moreover, for projects during operation (e.g., a motorway in a mountainous area), no recognized artificial intelligence algorithm exists that can forecast the deformation of steep slopes using the huge data obtained from monitoring devices. In this context, this paper introduces a real-time wireless monitoring system with multiple sensors for retrieving high-frequency overall data that can describe the deformation feature of steep slopes. The system was installed in the Qili connecting line of a motorway in Zhejiang Province, China, to provide a technical support for the design and implementation of safety solutions for the steep slopes. Most of the devices were retained to monitor the slopes even after construction. The machine learning Probabilistic Forecasting with Autoregressive Recurrent Networks (DeepAR) model based on time series and probabilistic forecasting was introduced into the project to predict the slope displacement. The predictive accuracy of the DeepAR model was verified by the mean absolute error, the root mean square error and the goodness of fit. This study demonstrates that the presented monitoring system and the introduced predictive model had good safety control ability during construction and good prediction accuracy during operation. The proposed approach will be helpful to assess the safety of excavated slopes before constructing new infrastructures.

Controllable Cell Deformation Using Acoustic Streaming for Membrane Permeability Modulation.

Hydrodynamic force loading platforms for controllable cell mechanical deformation play an essential role in modern cell technologies. Current systems require assistance from specific microstructures thus limiting the controllability and flexibility in cell shape modulation, and studies on real‐time 3D cell morphology analysis are still absent. This article presents a novel platform based on acoustic streaming generated from a gigahertz device for cell shape control and real‐time cell deformation analysis. Details in cell deformation and the restoration process are thoroughly studied on the platform, and cell behavior control at the microscale is successfully achieved by tuning the treating time, intensity, and wave form of the streaming. The application of this platform in cell membrane permeability modulation and analysis is also exploited. Based on the membrane reorganization during cell deformation, the effects of deformation extent and deformation patterns on membrane permeability to micro‐ and macromolecules are revealed. This technology has shown its unique superiorities in cell mechanical manipulation such as high flexibility, high accuracy, and pure fluid force operation, indicating its promising prospect as a reliable tool for cell property study and drug therapy development.

Unprecedented combination of strength and ductility in laser welded NiCoCr medium entropy alloy joints

Abstract CrMnFeCoNi high entropy alloys holding several principle elements have displayed exceptional strength, ductility and damage tolerance, and these properties are even better at cryogenic temperature. Among CrMnFeCoNi and its derivatives, NiCoCr, called medium entropy alloy (MEA), has shown the best mechanical properties. Yet, research on the welding of NiCoCr is still in its infancy, which, to certain extent, renders the application of such advanced alloys in engineering structures. Here, for the first time, laser welding is employed to join NiCoCr MEA to achieve butt-type joints; microstructure and mechanical properties at 300 K and 77 K are then examined by experiments and molecular dynamic (MD) simulation. It is found that the ultimate tensile strength (UTS) and ductility of the weld at 300 K are 525 ± 36 MPa and 85 ± 15%, respectively. At 77 K, the UTS is enhanced to 828 ± 99 MPa but the ductility is reduced by 10%. The combination of UTS and ductility at both tested temperatures is the best among the joints of CrMnFeCoNi and its derivatives. The reason for this unprecedented combination is explored by EBSD and atomistic simulation. Slip bands and low-density deformation twins are found in the deformed microstructure of the weld fractured at 300 K as evidenced from EBSD observation. High-density twins besides the slip bands are seen in the weld deformed at 77 K. Real-time atomistic deformation is revealed from MD simulation, including dislocation nucleation and its motion, the formation of twin boundaries, and the interaction between the dislocation and twin boundaries. The unprecedented combination of strength and ductility in laser welded NiCoCr joints provides significant promise of NiCoCr MEA for application in engineering structures, especially at cryogenic circumstances.

Generalized Model of Real-Time Deformation Measurements and its Experimental Verification

Generalized Model of Real-Time Deformation Measurements and its Experimental Verification

Integration of coseismic deformation into WebGIS for near real-time disaster evaluation and emergency response

Earthquakes are one of the destructive natural disasters. Immediate emergency response in the first few hours is important for life rescue. The near real-time ground deformation maps generated after earthquakes are crucial for hazard assessments, which normally take a couple of hours or longer to be generated using conventional ways. In this study, we propose a near real-time coseismic ground deformation map generation system with the aim of assisting rapid seismic hazard evaluations and emergency responses. This framework adopts the source parameters published by seismological agencies and uses the empirical equations to generate the near real-time coseismic ground deformation maps. The source parameters of an earthquake, such as the focal mechanism, are programmatically accessed from the United States Geological Survey National Earthquake Information Center (USGS-NEIC) in a nearly real-time manner. The ground deformation estimated using empirical equations is integrated as self-adapting spatial data fusion and visualized on an interactive WebGIS platform. We develop the WebGIS platform, namely QuickDeform at https://www.insar.com.cn , and successfully applied the system to several recent large magnitude earthquakes. We find that the proposed framework functions robustly and proficiently to automatically generate the seismic deformation map within several minutes after the occurrence of an earthquake. The generated deformation map shows good agreement when compared to the data from real earthquakes. QuickDeform can be used as a volunteered geographic information platform for crowdsourcing disaster data for rescue and model validation.

In-situ monitoring of substrate deformation in directed energy deposition process using the coherent gradient sensing method

Abstract In recent years, additive manufacturing (AM) has become one of the most promising manufacturing technologies. To enhance quality, in-situ monitoring for AM processes has drawn considerable attention from researchers. Although progress has been made for in-situ monitoring of the directed energy deposition (DED) process, there are still challenges that must be addressed to improve the manufacturing quality. To solve the problem of achieving both high resolution and step-wise evolution of full-field deformation during in-situ monitoring of AM, we propose the coherent gradient sensing (CGS) method for in-situ monitoring of the DED process in this study. A CGS system was designed to perform in-situ monitoring during the DED process. The real-time full-field deformation of a thick substrate was measured for the first time in the cladding process of a disc-shaped specimen, in which the deformation distribution characteristics at different locations were analyzed. During the first layer cladding process, the deformation evolution of the substrate can be divided into three bending stages: U-type, S-type, and transitional. Our results show a significant relationship between the boundary R of deformation distribution in the y-axis at different stages and the radius r of the disc-shaped specimen: R = 3/5 r, with R being the boundary of deformation distribution and r being the radius of the disc-shaped specimen. The experimental results reveal that the relationship between the in-situ deformation evolution of the substrate and the deposition track at different stages can be effectively monitored using a CGS system. Furthermore, the obtained results can offer useful reference for improving the quality of components that are repaired or remanufactured using DED technology.

Characterization of yield stress surface and strain-rate potential for tubular materials using multiaxial tube expansion test method

A combined experimental and computational method was developed to characterize the yield stress surface and the conjugate plastic strain-rate potential of the AA7075-O extruded tube under biaxial tension and biaxial tension-compression stress states based on the plastic work equivalency assumption. In all the previous experimental investigations, the focus was on developing tube bulging experimental setup with PID capability to control pressure and axial feed to generate real-time proportional deformation in the stress space. In this paper, a more practical method is introduced in which the PID control is implemented into a finite element model with the von Mises yield function to generate the necessary pressure and axial feed that result in any desired proportional strain path in the mid-section of the tube in the tube bulging simulation. As expected, the application of FEM + PID generated boundary conditions in the tube bulging experiments resulted in slightly different deformation paths. However, the plastic work equivalency assumption was used to construct the yield stress surface and the plastic strain-rate potential for the tube at different plastic work levels. Finally, the parameters of the Yld2004–18p yield function were calibrated for AA7075-O aluminum tube with the measured principal stress and plastic strain rate ratios for three levels of accumulated plastic work, and it was shown that this tubular material displays nearly isotropic plasticity under tension-compression, and anisotropic plasticity under tension-tension stress states.

Dynamic Mechanical Response and Damage Mechanism of HTPB Propellant under Impact Loading.

The dynamic mechanical behaviors of Hydroxyl-terminated polybutadiene (HTPB) propellant was studied by a split Hopkinson pressure bar apparatus (SHPB) at strain rates ranging from 103 to 104 s−1. The obtained stress–strain curves indicated that the mechanical features, such as ultimate stress and strain energy, were strongly dependent on the strain rate. The real time deformation and fracture evolution of HTPB propellant were captured by a high-speed digital camera accompanied with an SHPB setup. Furthermore, microscopic observation for the post-test specimen was conducted to explore the different damage mechanisms under various conditions of impact loading. The dominated damage characteristics of HTPB propellant were changed from debonding and matrix tearing to multiple cracking modes of ammonium perchlorate (AP) particles, along with the increase of the strain rate. For the first time, the influence of AP particle density on the dynamic response of HTPB propellant was studied by analyzing the strain-rate sensitivity (SRS) index of HTPB propellant with two different filler content (80 wt.% and 85 wt.%), which deduced from a power function of ultimate stress and strain energy density. The result of this study is of significance for evaluating the structural integrity and security of HTPB propellant.

On the real-time atomistic deformation of nano twinned CrCoFeNi high entropy alloy

High entropy alloys (HEAs) holding several principal elements in high concentration have unprecedented combination properties. The design of strong and highly ductile HEAs has attracted extensive attention from researchers in the last decade, such as in mechanisms for inducing different types of phase and nano-sized precipitates. Since some HEAs have low stacking fault energy, nanotwins can form during the plastic deformation process or magnetron sputtering, resulting in enhanced mechanical properties due to the existence of twin boundaries. The addition of twin boundaries is implied to be a promising method in engineering HEAs. Understanding how these twin boundaries affect the mechanical properties of nanotwinned HEAs is the key to designing strong and ductile examples. In this study, we performed a large-scale molecular dynamic simulation to investigate the mechanical properties of HEAs with different twin boundary spacings at various temperatures. The results show that the strength of HEAs at all tested temperatures increases with decreasing twin boundary spacing until a lower critical value of 1.83 nm is reached, which is close to the experimental value (2 nm). The strength of the HEAs at all tested temperatures decreases as the twin boundary spacing is decreased further. The dislocation motion transitions at the critical twin boundary spacing. In the sample with a twin boundary spacing bigger than 1.83 nm, Shockley dislocations tend to intersect the twin boundaries and glide in the hardening modes; on the other hand, Shockley dislocations travel along the direction parallel to the twin boundaries in samples with a twin boundary spacing smaller than 1.83 nm, leading to detwinning and softening in the HEAs. The dislocation motion and entanglement at 1 K are respectively slower and stronger than those at 300 K; the grain boundary activity is more obvious at a higher temperature. A mechanistic theoretical model together with a Hall–Petch relationship is then proposed to consider the coupled twin boundary and temperature effect on the deformation of nanotwinned HEAs.

Highly stretchable strain sensors based on polypyrrole-silicone rubber composites for human motion detection

Flexible strain sensors attained significant attraction due to their numerous applications, such as personal healthcare, robotics, human entertainment technology and sports performance monitoring. However, there still exist challenges to find out a strain sensing mechanism with a facile and cost-effective method. Polypyrrole (PPy)/SR composites were prepared by a simple, low-cost solution casting method. Carbonaceous fillers, graphene nano platelets (GNP), and carbon black (CB) were introduced along with PPy and the sensor performances including stretchability, flexibility, gauge factor (GF), linearity and durability were studied. PPy/SR composites showed a GF between 1.2 and 1.7 and exhibited reversible and stable electromechanical characteristics with an average response time of 150 milliseconds. The conductive mechanism, which causes piezoresistivity and the temperature-dependent resistance characteristics and mechanical properties, were studied. The excellent composite properties, such as super-stretchability, flexibility, biocompatibility, durability along with facile production and environmental stability, make them an ideal candidate for the fabrication of large strain wearable sensors which can be integrated to clothes or directly attached to the human body for real-time human body deformation measurements.

Measurement of Zircaloy-4 cladding tube deformation using a three-dimensional digital image correlation system with internal transient heating and pressurization

In this study, multi-dimensional (Multi-D) deformation of a Zircaloy-4 cladding tube under internal transient heating and pressurization conditions was measured by experimental setup named ‘Experimental setup to investigate high temperature deformation of cladding tube under internal pressurizing and heating (EIGEN)’ and three-dimensional digital image correlation (3D DIC) system. The ‘EIGEN’ experimental setup was designed to investigate high temperature deformation of the cladding tube under inert gas atmosphere. The 3D DIC system based on stereovision was further developed to be applied to high temperature by using high temperature resistant speckle pattern and bandpass filter. To evaluate measurement accuracy of the 3D DIC system, validation works of 3D DIC calibration were performed with proposed methodology. Additionally, a 3D finite element model (FEM) of the ‘EIGEN’ experiment was developed to evaluate the results of the 3D DIC. Finally, ‘EIGEN’ experiment was conducted under several fill pressure conditions such as 30, 50, 60, 70 bars. As a result, the established 3D DIC system could successfully measure in-situ and real-time large deformation such as ballooning and rupture as well as full-field multi-D deformation of the cladding tube at the high temperature under the inert atmosphere. Multi-D strains from the 3D DIC showed good agreement with calculated ones of the 3D FEM, and they were also compared with 3D laser scanning results for validation.

A Real-Time Method to Detect the Deformation Behavior during Laser Solid Forming of Thin-Wall Structure

Laser solid forming (LSF) is a promising additive manufacturing technology. In the LSF process, deformation behaviors dictate the accuracy of the produced parts. In this study, by using a laser displacement detector based on laser triangulation principle, an accurate and effective real-time detection method was established to monitor the real-time deformation behavior of the key position during the LSF of a thin-wall structure. The results confirmed that increasing thin-wall length results in increasing final deformation of the edge. The displacement fluctuation range and value in the middle of thin wall are both smaller than that of the positions near the end, while the entire displacement changing direction in the middle is opposite to that of the end positions. When the deposition process is paused, the deformation of the thin wall during the cooling stage will deviate the position of the deposited thin wall, resulting in the dislocation between the subsequent deposited part and that before the pause, which affect the dimensional accuracy of the thin wall structure. This non-contact real-time detection method also confirmed the ability to monitor the initiation of cracking during the LSF process, and a potential to be used for the on-line feedback control of deformation of detected key position of deposited structure.

4D printed electro-induced continuous carbon fiber reinforced shape memory polymer composites with excellent bending resistance

Four-dimensional (4D) printing technology of continuous carbon fiber reinforced shape memory polymer composites is a potential manufacturing process for lightweight and high-strength intelligent composite structures. In this study, a 3D printer with dual feed channels based on the fused deposition modeling (FDM) was designed to fabricate continuous carbon fiber reinforced shape memory poly(lactic acid)-based composites (CFRSMPC). The impact of various printing parameters on the bending strength and flexural modulus of 4D printed CFRSMPC was evaluated by the three-point bending test. Meanwhile, mathematical prediction models of bending strength and modulus based on the existing experimental data were established. The electro-induced shape memory effect of 4D printed CFRSMPC was investigated by the electric heating shape recovery test. The shape recovery rate of the specimens was more than 95%, indicating that the resistance heating method is stable and feasible. The quantitative effect of bending angle and temperature on the resistance of CFRSMPC during the programming and recovery process was further investigated. The results demonstrated that the real-time deformation of the CFRSMPC could be monitored by the resistance measurement method. It can be concluded that the CFRSMPC fabricated using the 4D printing method can serve as potential building blocks for electrically activated and deployable structures.

Digital image correlation with improved efficiency by pixel selection

With the increase in digital image correlation (DIC) applications, the computational efficiency of DIC is becoming increasingly important. In previous studies, real-time DIC was realized with a relatively small subset. However, a small subset does not always include sufficient gray gradient information. In this paper, a pixel selection strategy is proposed to improve the computational efficiency of DIC further, allowing a real-time deformation measurement with a large subset. Within the subset, zero weight is assigned to unreliable pixels as a way of pursuing maximum efficiency. The modulus of the local intensity gradient vector of each pixel in the reference image is used as the criterion for reliability. Numerical and real experiments conducted to validate the feasibility and effectiveness of the strategy showed that the computational speed of DIC could be improved about 2 times.

Программно-ориентированный подход к анализу перемещений в контактно-стесненных оболочечных конструкциях

In transversely separable shell structures, a thin metal shell is surrounded by a rigid medium. The proposed approach to solving delamination problems in such constructions is based on three points: the introduction of technological deviations (corresponding to permissible defects in actual structures) to the computation scheme of the structure; the determination of the volumetric general stress-strain state of the structure; real-time structure deformation accounting. The approach is implemented in the LS-DYNA software package in a dynamic formulation using finite elements TSHELL and SOLID, taking into account the geometric and physical nonlinearity of the structure and the shell — medium contact surface with unilateral constraint along normal line, without tangent interactions. According to the proposed approach, the result of calculations is the assessment of the loads on the initial two-layer structure, under which a metal shell with low bending stiffness can lose stability in the local area in the form of internal wrinkles. An example of the calculation of a cylindrical metal-composite high-pressure vessel under loading by a cooled external composite shell is given. The time intervals of the onset of delamination and growth of wrinkles on the surface of the inner metal shell (liner) are established. The solutions are presented in the form of images of the deformed surface of the liner and graphs of time-dependent changes in stresses, strains and displacements; their correspondences to each other are shown. The proposed approach allows one by visual demonstration and accurately to assess the possibility of delamination in contact-constrained shell structures already at the design stage.

Real-Time Diagnosis of Island Landslides Based on GB-RAR

Landslides are one of the most frequent and serious geological disasters that threaten people’s lives and property safety. In recent years, with the rapid development of the coastal economy and the increasingly strained spatial resources, the island development activities have become extremely rapid, resulting in the frequent occurrence of landslides on the island. We selected Beichangshan Island in the north of China as the research area. By using high-precision ground-based real aperture radar (GB-RAR) measurement technology, the displacement changes of potential landslides are monitored continuously and dynamically to realize the real-time diagnosis and early warning of island landslides. At the same time, the data interpretation method and key processing flow are described in detail. The results show that during the whole monitoring process, an area of obvious change is found, which is mainly located in the middle of the landslide mass. The mean velocity rate shows a nonlinear deformation trend. The maximum deformation of the landslide in the five selected points reaches 4.5 mm, which indicates that the area is in an unstable stage. The deformation monitoring ability of GB-RAR technology to identify the sub-millimeter level is demonstrated, and the monitoring method is verified. The validity and reliability of the method can be applied to real-time dynamic fine deformation diagnosis of island landslides. Its accuracy can meet the needs of dynamic change monitoring of island landslides, and it can become an important tool and means for early warning and treatment of landslides. The research is conducive to further enriching and improving the monitoring method system of island geological disasters in China, provides a scientific basis and technical support for early warning and disaster prevention and mitigation of island landslides, and can be popularized and applied in the monitoring of island landslides.