Three-dimensional Deformation Field Research Articles

AM-FEMU: An optimization method for additive manufacturing simulation parameters based on finite element model updating, utilizing three-dimensional deformation and melt pool temperature fields

AM-FEMU: An optimization method for additive manufacturing simulation parameters based on finite element model updating, utilizing three-dimensional deformation and melt pool temperature fields

Three-dimensional deformation monitoring of San Francisco Bay based on GNSS-InSAR data

As a cutting-edge technology in the field of remote sensing, Synthetic Aperture Radar Interferometry (InSAR) plays a significant role in monitoring urban surface deformation. The traditional multi-temporal InSAR technique can only obtain surface deformation in the line-of-sight (LOS) direction, and there are fewer studies on three-dimensional(3D) deformation monitoring in coastal areas. At the same time, there is a lack of research on integrating GNSS-InSAR data to obtain the three-dimensional deformation field in the San Francisco Bay area. Using ascending and descending orbit InSAR images and GNSS data to monitor ground subsidence in the San Francisco Bay area, various schemes of integrating GNSS and InSAR data to invert the three-dimensional deformation field were analyzed and compared. An improved Robust-Helmert estimation method was proposed to calculate the 3D ground deformation velocity. The results showed that the Robust-Helmert estimation method performed best, with Root Mean Square Error (RMSE) values of 3.96 mm, 6.51 mm, and 2.75 mm in the East-West (E), North-South (N), and Up-Down (U) directions, respectively. It also exhibited more stable solution accuracy and good universality.

Three-dimensional interseismic crustal deformation in the northeastern margin of the Tibetan Plateau using GNSS and InSAR

The nature of the crustal deformation of the northeastern margin of the Tibetan Plateau is vital for elucidating the expansion mechanism of the plateau. We installed 21 continuous GNSS stations and obtained a horizontal velocity field with high spatial resolution. We also acquired a line-of-sight(LOS)velocity field with Sentinel-1 images covering the study area from 2014 to 2022. A multi-scale spherical wavelet method was employed to unify the reference frames of GNSS and InSAR data. After unifying the reference frame, the two data types achieve high consistency. Combining GNSS and InSAR velocities yielded the three-dimensional interseismic velocity field in the northeastern margin of the Tibetan Plateau. Furthermore, we analyzed the crustal deformation characteristics based on the three-dimensional deformation field. The crustal deformation exhibits a pronounced northeastward shift relative to the Ordos block, whereas the interior of the Ordos block remains remarkably stationary, behaving as a rigid unit. The Liupanshan fault is primarily characterized by uplift, devoid of any notable horizontal deformation across the fault. The left-lateral strike-slip mainly characterizes the Haiyuan fault.. The maximum east–west deformation velocity on the southern side of the fault is approximately 3.9 mm/yr, decreasing to about 1.0 mm/yr at the eastern end of the fault. The western segment of the West Qinling fault exhibits a minor east–west motion. Our result provides essential data for further study of the crustal deformation patterns.

The Improved SBAS-InSAR Technique Reveals Three-Dimensional Glacier Collapse: A Case Study in the Qinghai–Tibet Plateau

Many debris-covered glaciers are widely distributed on the Qinghai–Tibet Plateau. Glaciers are important freshwater resources and cause disasters such as glacier collapse and landslides. Therefore, it is of great significance to monitor the movement characteristics of large active glaciers and analyze the process of mass migration, which may cause serious threats and damage to roads and people living in surrounding areas. In this study, we chose a glacier with strong activity in Lulang County, Tibet, as the study area. The complete 4-year time series deformation of the glacier was estimated by using an improved small-baseline subset InSAR (SBAS-InSAR) technique based on the ascending and descending Sentinel-1 datasets. Then, the three-dimensional time series deformation field of the glacier was obtained by using the 3D decomposition technique. Furthermore, the three-dimensional movement of the glacier and its material migration process were analyzed. The results showed that the velocities of the Lulang glacier in horizontal and vertical directions were up to 8.0 m/year and 0.45 m/year, and these were basically consistent with the movement rate calculated from the historical optical images. Debris on both sides of the slope accumulated in the channel after slipping, and the material loss of the three provenances reached 6–9 × 103 m3/year, while the volume of the glacier also decreased by about 76 × 103 m3/year due to snow melting and evaporation. The correlation between the precipitation, temperature, and surface velocity suggests that glacier velocity has a clear association with them, and the activity of glaciers is linked to climate change. Therefore, in the context of global warming, the glacier movement speed will gradually increase with the annual increase in temperature, resulting in debris flow disasters in the future summer high-temperature period.

Coseismic deformation and seismogenic structure of the 2024 Hualien Earthquake measured by InSAR and GNSS

On April 3, 2024, an M7.3 earthquake occurred in the offshore area of Hualien County, Taiwan, China. The seismogenic structure at the epicentral location was highly complex, and studying this earthquake is paramount for understanding regional fault activity. In this study, we employed ascending and descending orbit Sentinel-1 Synthetic Aperture Radar (SAR) data and utilized differential interferometry (InSAR) technique to obtain the co-seismic deformation field of this event. The line-of-sight deformation field revealed that the main deformation caused by this earthquake was predominantly uplift, with maximum uplift values of approximately 38.8 ​cm and 46.1 ​cm for the ascending and descending orbits, respectively. By integrating the three-dimensional GNSS co-seismic deformation field, we identified the seismogenic fault located in the offshore thrust zone east of Hualien, trending towards the northwest. The fault geometry parameters, obtained through the inversion of an elastic half-space homogeneous model, indicated an optimal fault strike of 196°, a dip angle of 30.9°, and an average strike-slip of 0.4 ​m and dip-slip of −2.6 ​m. This suggests that the predominant motion along the seismogenic fault is thrusting. The distribution of post-seismic Coulomb stress changes revealed that aftershocks mainly occurred in stress-loaded regions. However, stress loading was observed along the northern segment of the Longitudinal Valley Fault, with fewer aftershocks. This highlights the importance of closely monitoring the seismic hazard associated with this fault segment.

Postoperative facial prediction for mandibular defect based on surface mesh deformation

Objectives: This study aims to introduce a novel predictive model for the post-operative facial contours of patients with mandibular defect, addressing limitations in current methodologies that fail to preserve geometric features and lack interpretability.Methods: Utilizing surface mesh theory and deep learning, our model diverges from traditional point cloud approaches by employing surface triangular mesh grids. We extract latent variables using a Mesh Convolutional Restricted Boltzmann Machines (MCRBM) model to generate a three-dimensional deformation field, aiming to enhance geometric information preservation and interpretability.Results: Experimental evaluations of our model demonstrate a prediction accuracy of 91.2 %, which represents a significant improvement over traditional machine learning-based methods.Conclusions: The proposed model offers a promising new tool for pre-operative planning in oral and maxillofacial surgery. It significantly enhances the accuracy of post-operative facial contour predictions for mandibular defect reconstructions, providing substantial advancements over previous approaches.

Factors influencing the effectiveness of SM-VCE method in solving 3D surface deformation

The recovery of coseismic 3-dimensional (3D) surface deformation field plays a crucial role in studying seismic source characteristics and earthquake hazards. As of now, there are two main types of methods for recovering coseismic 3D surface deformations: the first type is to solve the problem directly by using the least squares method based on observations from three or more viewpoints, and the second type solves the problem by combining ascending and descending InSAR line-of-sight (LOS) observations with constraint models. The former type is mainly applicable to surface rupture earthquakes, because when an earthquake ruptures to the surface, we can usually obtain surface deformation observations from three or more views. The latter type applies to earthquakes that do not cause surface ruptures and have extensive blind faults. Currently, most research focuses on improving the above types of methods. However, some key factors in the coseismic 3D surface deformation inversion are rarely mentioned, such as the influence of window size on the inversion results in the strain model and variance component estimation method (SM-VCE), and whether the outliers in the observational data are considered. So, we developed a new chain of integrating InSAR observation and SM-VCE model to systematically assess the impacts of window size and outliers on coseismic 3D surface deformation inversions. Through simulation experiments, we observed that the selection of window size significantly impacts the accuracy of the results. Specifically, larger window sizes lead to wider residuals ranges in the fault region, resulting in the loss of extreme solution values when using a window of 15 × 15 pixels (i.e., 7.5 km × 7.5 km). Hence, we recommend utilizing windows with 7 × 7 pixels or 9 × 9 pixels for optimal accuracy, as larger window sizes diminish the significance of the outcomes. The elimination of points displaying different deformation directions helps reduce residuals and preserves near-field deformation results. Furthermore, the residuals along the 3D direction can be reduced by 10%–30% when a small set of points is selected using a method based on Euclidean distances. However, when 441 points were selected, the vertical residuals increased by 22% compared to 81 points. Integration of the SM-VCE algorithm with robust estimation techniques effectively minimizes far-field deformation errors in data, thereby marginally enhancing the near-field deformation solution.

Characterizing damage evolution in fiber reinforced composites using in-situ X-ray computed tomography, deep machine learning and digital volume correlation (DVC)

In-situ X-ray computed tomography (CT) techniques enable to examine microstructural evolution of composite materials continuously and nondestructively under loading for better understanding the initiation and propagation of microscopic damages. This study explores the tensile damage behavior of notched woven carbon/epoxy composites under successive loading process. Since the image contrast of different composite material phases is normally low and conventional image segmentation techniques are hard to identify microstructures and defects in different directions distinctively, a U-Net image segmentation model based on deep machine learning algorithms is employed to characterize microstructures and material damages precisely and consistently. Digital volume correlation (DVC) approach is proposed here tocharacterize the three-dimensional (3D) deformation fields of carbon/epoxy composites at different loading steps, and the DVC results are used to predict location of damage initiation and propagation. It is found that the damage modes of notched carbon/epoxy composites mainly include fiber breakage, longitudinal cracks in warp fiber tows, and transverse cracks in weft fiber tows. The individual fiber breakage occurs in warp fiber tows at the intermediate loading level, and longitudinal and transverse cracks appear in further loading levels. Longitudinal cracks and fiber breakage events take place in a region tangent to the notch tip and exhibit a strong interaction. The development of longitudinal cracks promotes the initiation and propagation of transverse cracks. In addition, the strain concentration regions in 3D deformation fields match well with the microscopic cracks segmented by the U-Net deep learning model. This study demonstrated that the integration of X-ray computed tomography, digital volume correlation and image semantic segmentation enables to identify damage initiation, evolution, extent and mechanism.

Coupling effect of impoundment and irrigation on landslide movement in Maoergai Reservoir area revealed by multi-platform InSAR observations

The mountainous areas of Southwest China are crucial regions for hydropower resource development. The unique geological environment and numerous constructed hydropower stations make landslides the primary geological hazard for the region. Therefore, the deformation monitoring and mechanism analysis of reservoir landslides have attracted extensive attention from the academic community. The Maoergai Reservoir (MEGR) is located in the middle reaches of the Heishui River in Sichuan Province, China. Following impoundment, numerous active slopes have arisen in the reservoir area, with the Xierguazi-Mawo landslide complex (XMLC) potentially being the most threatening. In this paper, we first acquired the surface displacement of the MEGR area, before and after impoundment, using time series Synthetic Aperture Radar Interferometry (InSAR) analysis of the ALOS-1/PALSAR-1, ALOS-2/PALSAR-2 and Sentinel-1 datasets. Then, the three-dimensional (3D) deformation field was inverted by combining multi-track InSAR observations and a topography-constrained model. Results show the presence of 47 active landslides within the 675 km2 reservoir area, a significant increase compared to the seven landslides identified prior to impoundment. Based on the derived 3D velocity vectors, we found that the motion of the XMLC exhibits heterogeneity in terms of spatial and temporal patterns. Further, the displacement time series of all detected active landslides suggests that irrigation and water level fluctuations are two major factors influencing the kinematic behaviors of landslides. Irrigation accelerates landslide movement and thus permanently alters the deformation trend, while water level fluctuations cause seasonal oscillations in the displacement time series with a time lag of approximately 100 days. The above results can contribute to landslide management and prevention in the MEGR area and provide a representation for numerous water reservoirs in southwest China.

Experimental and analytical studies on the behavior of connections between high-rise braced steel storage racks and the spine bracing

The primary lateral load resisting system of the high-rise braced steel storage racks is the spine bracing located at a short distance away from the rear rack frames. The connections between the rack frames and spine bracing, which transmit the horizontal stabilizing forces, dictate the effectiveness of the spine bracing and the global performance of the entire high-rise racking system. The first part of this paper experimentally establishes the behavior of the connections between the racks and the spine bracing under lateral loads, utilizing four groups of three nominally identical test specimens. A digital image correlation (DIC) measurement system is employed to generate comprehensive data associated with the behavior of individual components of such connections. The behavior of the connection components is quantified and discussed based on the three-dimensional deformation field recorded by the DIC system. The second part of this paper develops a component-based elastic analytical model for the connections between the racks and the spine bracing under consideration. The endplate spatial flexural bending mechanism, as well as the upright cross-section distortional behavior, are explicitly considered by the analytical model. The contributions of each individual component towards the total deformation of the connections are quantified. The paper concludes with design and construction recommendations for the enhancement of the connections between the racks and the spine bracing, while recognizing the limitations of this research.

Analysis of the fault slip, creep, and coupling characteristics of the Maomaoshan-Laohushan-Haiyuan Fault using InSAR and GNSS measurements

Line-of-sight Interferometric Synthetic Aperture Radar (InSAR) observations are affected by long-wavelength errors and the inaccurate estimation of vertical deformation, thereby restricting horizontal slip rate estimations for strike-slip faults, such as the Maomaoshan-Laohushan-Haiyuan Fault (MMS-LHS-HY). To overcome this limitation, herein, InSAR (2016–2022) and Global Navigation Satellite System (GNSS) observations were combined and the Least Squares Variance Component Estimation (LS-VCE) method was used to obtain the Three-Dimensional (3-D) deformation field of the Haiyuan fault zone; subsequently, the slip-rate and coupling distributions were inverted. The results showed that: (1) Compared with the GNSS and leveling deformation velocities, the residuals of the 3-D deformation field obtained using the LS-VCE method combined with the GNSS and InSAR observations reached an RMS of 1 mm/a, significantly better than the deformation field obtained without GNSS data. (2) Vertical deformation from InSAR observations led to over- or under-estimation of the fault strike-slip rate, with the maximum influence on the shallow creep rate of 2.1 mm/a. (3) Based on the 3-D deformation field, fault slip rate, locking depth, and fault creep characteristics obtained from the elastic dislocation and elastic block models were consistent with each other. (4) The strike-slip rate of the MMS-LHS-HY fault gradually decreased from west to east, whereas the thrust rate gradually increased in the same direction. (5) Based on the 3-D deformation field, the creep range of the LHS fault was ∼40 km, with the mean shallow creep rate reaching 2.5 ± 0.1 mm/a, notably larger than the creep rate obtained by ascending InSAR observation alone.

Displacement field reconstruction in landslide physical modeling by using a terrain laser scanner – Part 1: Methodology, error analysis and validation

Laser scanning technology has been widely used in landslide aspects. However, the existing deformation analysis based on terrain laser scanners can only provide limited information, which is insufficient for understanding landslide kinematics and failure mechanisms. To overcome this limitation, this paper proposes an automated method for processing point clouds collected in landslide physical modeling. This method allows the acquisition of quantitative three-dimensional (3D) deformation field information. The results show the organized and spatially related point cloud segmentation in terms of spherical targets. The segmented point clouds can be fitted to determine the locations of all preset targets and their corresponding location changes. The proposed method has been validated based on theoretical analysis and numerical and physical tests, which indicates that it can batch-process massive data sets with high computational efficiency and good noise resistance. Compared to existing methods, this method shows a significant potential for understanding landslide kinematics and failure mechanisms and advancing the application of 3D laser scanning in geotechnical modeling.

3D deformation and strain fields in drying kaolinite obtained from tracking internal bubbles using X-ray CT and ANN

AbstractDrying fine-grained sediments experience shrinkage and desiccation cracking that may dramatically alter their mechanical and hydraulic properties. This study adopts X-ray computed tomography (CT) to monitor the three-dimensional (3D) internal deformation and strain fields, and their relationships with desiccation crack formation, for drying kaolinite samples contained in plastic containers. Two kaolinite samples, one dried at room temperature and the other oven-dried at 60 °C, were CT scanned at several intervals during the drying process. From sequential CT scans for the same sample, entrained gas bubbles were extracted and used as tracking markers for deformation and strain field measurements. Since the bubble morphology continuously changed during the drying process, an artificial neural network (ANN) model was developed to link bubbles in sequential scans for the same sample. The tracking algorithm was trained with manually linked bubbles and optimised by comparing different combinations of bubble information, e.g. bubble location, size and shape. The drying samples experienced primarily vertical displacement before the air-entry value, while horizontal displacement occurred during vertical crack formation. Internal vertical and horizontal strains were generally uniform, indicating a limited impact of non-uniform sample drying and substrate constraint.

Present-Day Three-Dimensional Deformation across the Ordos Block, China, Derived from InSAR, GPS, and Leveling Observations

The Ordos Block in China experiences tectonic activity and frequent earthquakes due to compression from the Tibetan Plateau and extension from the North China Block. This has prompted the construction of a high-resolution three-dimensional (3D) deformation field to better understand the region’s crustal movement. Considering the limitations of the existing geodetic observations, we used InSAR, GPS, and leveling observations to create a high-precision 3D deformation field for the Ordos Block. Spherical wavelet decomposition was used to separate tectonic and non-tectonic deformation signals. Short-wavelength non-tectonic deformation fields revealed complex surface deformation patterns caused by groundwater, oil, gas extraction, and coal mining. Long-wavelength tectonic deformation fields showed subsidence in the southern margin of the block, while the interior and northeastern margins were uplifted. By combining imaging results from the seismic velocity structure and magnetotellurics, we infer that the upwelling of deep materials beneath the northeastern margin leads to surface uplift with tensile strain rates. The crustal uplift in the area south of 38°N matches the thickening of the lower crust. The weak subsidence and eastward horizontal movement disappearing near 108°E at the southern margin support the existence of asthenosphere flow beneath the Qinling orogenic belt.

The Crustal Dynamics and Its Geological Explanation of the Three-Dimensional Co-Seismic Deformation Field for the 2021 Maduo MS7.4 Earthquake Based on GNSS and InSAR.

Three-dimensional deformation is an important input to explore seismic mechanisms and geodynamics. The GNSS and InSAR technologies are commonly used to obtain the co-seismic three-dimensional deformation field. This paper focused on the effect of calculation accuracy caused by the deformation correlation between the reference point and the points involved in the solution, to build a high-accuracy three-dimensional deformation field for a detailed geological explanation. Based on the variance component estimation (VCE) method, the InSAR LOS, azimuthal deformation, and the GNSS horizontal and vertical deformation were integrated to solve the three-dimensional displacement of the study area in combination with the elasticity theory. The accuracy of the three-dimensional co-seismic deformation field of the 2021 Maduo MS7.4 earthquake obtained by the method proposed in this paper, was compared with that obtained from the only InSAR measurements obtained using a multi-satellite and multi-technology approach. The results showed the difference in root-mean-square errors (RMSE) of the integration and GNSS displacement was 0.98 cm, 5.64 cm, and 1.37 cm in the east-west, north-south and vertical direction respectively, which was better than the RMSE of the method using only InSAR and GNSS displacement, which was 5.2 cm and 12.2 cm in the east-west, north-south, and no vertical direction. With the geological field survey and aftershocks relocation, the results showed good agreement with the strike and the position of the surface rupture. The maximum slip displacement was about 4 m, which was consistent with the result of the empirical statistical formula. It was firstly found that the pre-existing fault controlled the vertical deformation on the south side of the west end of the main surface rupture caused by the Maduo MS7.4 earthquake, which provided the direct evidence for the theoretical hypothesis that large earthquakes could not only produce surface rupture on seismogenic faults, but also trigger pre-existing faults or new faults to produce surface rupture or weak deformation in areas far from seismogenic faults. An adaptive method was proposed in GNSS and InSAR integration, which could take into account the correlation distance and the efficiency of homogeneous point selection. Meanwhile, deformation information of the decoherent region could be recovered without interpolation of the GNSS displacement. This series of findings formed an essential supplement to the field surface rupture survey and provided a novel idea for the combination of the various spatial measurement technologies to improve the seismic deformation monitoring.

Optimal design of FBG flexible sensor for high-precision monitoring of three-dimensional deformation of power transmission line tower foundation

During the operation of the power transmission line tower foundation, uneven settlement and horizontal sliding were formed due to the damage of the local environment or external force. It is the most direct and effective way to realize the transformation from “passive response” to “active prevention and control” by real-time and long-term monitoring of the tower foundation and providing automatic early warning. In this paper, based on FBG (fiber Bragg grating) sensing technology, a FBG flexible sensor with temperature self-compensation characteristic was developed, which can be used for real-time monitoring of three-dimensional deformation field of tower foundation. Based on the strain information measured by the sensor, a coordinate transformation fitting algorithm was applied to reconstruct the deformation field of the tower foundation. To improve the displacement sensing precision of the flexible sensor, the influence of the length of the cemented layer and the groove radius on the strain transfer coefficient was analyzed, and the orthogonal curvature obtained by the sensing point was corrected by cubic spline interpolation. In the displacement sensing experiment, the mean absolute errors along the x-axis direction after interpolation correction were 1.84 mm (Type 1), 1.52 mm (Type 2) and 1.96 mm (Type 3), respectively; the mean absolute errors along the y-axis direction were 1.64 mm (Type 1), 2.34 mm (Type 2) and 1.21 mm (Type 3), respectively. After interpolation correction, the maximum absolute error percentages of the measuring points along the x-axis were 9.62% (Type 1), 9.01% (Type2) and 10.23% (Type 3); the maximum absolute error percentages along the y-axis were 10.44% (Type 1), 9.53% (Type2) and 9.43% (Type 3). Therefore, the designed FBG flexible sensor can be competent for the task of monitoring the three-dimensional deformation field of the tower foundation, which has important significance and application promotion value.

Three-dimensional displacement field of the 2010 Mw 8.8 Maule earthquake from GPS and InSAR data with the improved ESISTEM-VCE method

The 2010 Mw 8.8 Maule earthquake occurred offshore central Chile and ruptured ∼500 km along the megathrust fault resulting from the oceanic Nazca plate subducting beneath the continental South American plate. The Maule earthquake produced remnant crustal displacements captured by a vast set of geodetic observations. However, given the nature of the observational techniques, it is challenging to extract its accurate three-dimensional coseismic deformation field with high spatial resolution. In this study, we modified the extended simultaneous and integrated strain tensor estimation from geodetic and satellite deformation measurements (ESISTEM) method with variance component estimation algorithm (ESISTEM-VCE) to retrieve the three-dimensional surface displacement field of this event by integrating the interferometric synthetic aperture radar (InSAR) and global positioning system (GPS) measurements. The ESISTEM-VCE method accounts for the spatial correlation of surface displacement among the adjacent points and determine the accurate weight ratios for different data sets, but also uses the uncertainties of GPS data and considers the different spatial scales from the different datasets. In the simulation experiments, the RMSEs of the ESISTEM-VCE method are smaller than those of the ESISTEM and ESISTEM-VCE (same d0) methods, and the improvements of 97.1%, 3.9%, and 84% are achieved in the east-west, north-south, and vertical components, respectively. Then, we apply the proposed methodology to the 2010 Mw 8.8 Maule earthquake, to obtain a three-dimensional displacement field that could provide fine deformation information. In the east-west component, the significant deformation is in the north of the epicenter, closed to the Constitución, with a maximum westward displacement of 495.5 cm. The displacement in the north-south component is relatively small compared to that in the east-west component. The maximum uplift reaches 211.8 cm, located at the southwest of the Concepción. Finally, the derived vertical displacements are also compared with field investigations, indicating that the ESISTEM-VCE method can obtain more accurate weight of different datasets and perform better than the ESISTEM method. The results highlight that the earthquake ruptured along the NE-SW direction, with a dominant thrust and a relatively small component of right-lateral strike-slip, coinciding with the characteristics of subduction and right-lateral shear. The experiments with the simulated and real data suggest that the improved ESISTEM-VCE method in this study is feasible and effective.

Experimental study on failure characteristics of rock-fiber concrete composite under compression load

To study the failure characteristics of the rock-fiber concrete composite structure under compressive load, the experimental research was conducted with the aid of the 3D-DIC full-field strain test experimental system. The three-dimensional space deformation field information of the composite layer was obtained. The deformation characteristics, damage characteristics and failure modes of the composite layer were analyzed. (1) The local strain field and the overall strain field of the composite layer will increase to different degrees when subjected to compressive load. When the failure is approaching, the local strain field in the crack initiation area will increase rapidly. (2) The changes in the three-dimensional displacement field and strain field of the composite layer will retain the characteristics of brittle materials. The horizontal strain field and the vertical strain field show different distribution patterns, respectively. (3) The damage change of the specimen undergoes four stages: micro damage, damage accumulation, damage manifestation and complete damage. (4) The test results show that the binding site of the composite can play a certain effect of crack arrest.

The Study of Tooth Erosion Tested by the Color Digital Holography (CDH) Detection System

This study presents a color digital holography (CDH) detection system that includes the optical path and a numerical calculation program to detect tooth erosion under different acid-etching conditions. Etched cattle enamel samples were pressurized within the elastic interval, and the CDH detection system was used to rebuild the three-dimensional deformation field of these samples. Young’s modulus of these samples was employed to evaluate the mechanical properties of enamels by statistical methods. The results show that Young’s modulus of enamel decreases with the increase in etching time, while it decreases slightly with the increase in the etching temperature, and the etching temperature has no effect on the non-etched enamels. Moreover, the detection process proves the CDH detection system has the advantages of high precision, full-field detection, and being non-destructive, fast, and stable. It is expected to have broad application potential for CDH detection systems in the detection of tooth erosion.

Overall subshear but locally supershear rupture of the 2021 Mw 7.4 Maduo earthquake from high-rate GNSS waveforms and three-dimensional InSAR deformation

An Mw 7.4 left-lateral earthquake hit Maduo County in Qinghai province, China, on 21 May 2021. In this paper, we combined the 1-Hz global navigation satellite system (GNSS) displacement waveforms, GNSS static offsets and the three-dimensional (3D) co-seismic deformation field from the interferometric synthetic radar (InSAR) measurements to estimate the source kinematics of this event. Our results reveal that there was about 160 km of surface ruptures with varying strike angles, and the earthquake propagated bilaterally, with the bulk of the slip formed to the southeast of the epicenter. Substantial slip occurred to a depth of ~6 km, and the estimated maximum slip was ~5 m. The source time function presents a ~ 35-s total duration with two peaks, and the total geodetic seismic moment is 1.61 × 1020 Nm (equivalent to Mw 7.4). The near-field high-rate GNSS waveforms inversion results indicate that this earthquake is an overall subshear but locally supershear rupture event. The preferred average rupture velocity is 2.8 km/s while the velocities to the southeast and northwest of epicenter are 3.8 and 2.2 km/s, respectively. Supershear enhanced ground motion and simulation using the 3D curvilinear grid finite-difference method shows the acceleration caused by the earthquake exceeded the building code limits for bridges that collapsed due to strong ground shaking. Furthermore, this earthquake increased the stress level of the Maqin–Maqu segment of the East Kunlun Fault, and was also responsible for an off-fault aftershock sequence at the northwest end of the earthquake rupture.