Deformation Measurement Research Articles

High-frequency Structure Deformation Measurement Based on an Event Camera

High-frequency Structure Deformation Measurement Based on an Event Camera

GMDIC: a digital image correlation measurement method based on global matching for large deformation displacement fields

The digital image correlation method is a non-contact optical measurement method, which has the advantages of full-field measurement, simple operation, and high measurement accuracy. The traditional DIC method can accurately measure displacement and strain fields, but there are still many limitations. (i) In the measurement of large displacement deformations, the calculation accuracy of the displacement field and strain field needs to be improved due to the unreasonable setting of parameters such as subset size and step size. (ii) It is difficult to avoid under-matching or over-matching when reconstructing smooth displacement or strain fields. (iii) When processing large-scale image data, the computational complexity will be very high, resulting in slow processing speeds. In recent years, deep-learning-based DIC has shown promising capabilities in addressing the aforementioned issues. We propose a new, to the best of our knowledge, DIC method based on deep learning, which is designed for measuring displacement fields of speckle images in complex large deformations. The network combines the multi-head attention Swin-Transformer and the high-efficient channel attention module ECA and adds positional information to the features to enhance feature representation capabilities. To train the model, we constructed a displacement field dataset that conformed to the real situation and contained various types of speckle images and complex deformations. The measurement results indicate that our model achieves consistent displacement prediction accuracy with traditional DIC methods in practical experiments. Moreover, our model outperforms traditional DIC methods in cases of large displacement scenarios.

Method for luminescent digital image correlation deformation measurement in non-illuminated environments

This study presents a luminescent digital image correlation (DIC) method that utilizes long afterglow materials to prepare speckle patterns, overcoming the limitations of classical DIC in achieving high-precision deformation measurements, such as the issues of specular reflections from specimens and insufficient contrast of speckle patterns. While fluorescent DIC has some advantages in overcoming these limitations, it relies on active ultraviolet light sources, making it challenging for luminescent measurements. Long afterglow materials, capable of maintaining brightness for extended periods, serve as a viable alternative. Through sphere reconstruction experiments, the accuracy of this method was validated, demonstrating a relative error of 0.04% under well-illuminated conditions and 0.025% under non-illuminated conditions. Finite element simulations and a comparison with DIC experimental results showcased excellent consistency, suggesting the potential for this method to further replace fluorescent DIC measurements. Furthermore, the study revealed that speckle patterns prepared using this approach ensure measurement validity in both well-illuminated and non-illuminated scenarios. This luminescent DIC method holds promising potential for broader applications in non-illuminated measurement environments.

Strain and Deformation Analysis Using 3D Geological Finite Element Modeling with Comparison to Extensometer and Tiltmeter Observations

This study verifies the practicality of using finite element analysis for strain and deformation analysis in regions with sparse GNSS stations. A digital 3D terrain model is constructed using DEM data, and regional rock mass properties are integrated to simulate geological structures, resulting in the development of a 3D geological finite element model (FEM) using the ANSYS Workbench module. Gravity load and thermal constraints are applied to derive directional strain and deformation solutions, and the model results are compared to actual strain and tilt measurements from the Jiujiang Seismic Station (JSS). The results show that temperature variations significantly affect strain and deformation, particularly due to the elevation difference between the mountain base and summit. Higher temperatures increase thermal strain, causing tensile effects, while lower temperatures reduce thermal strain, leading to compressive effects. Strain and deformation patterns are strongly influenced by geological structures, gravity, and topography, with valleys experiencing tensile strain and ridges undergoing compression. The deformation trend indicates a southwestward movement across the study area. A comparison of FEM results with ten years of strain and tiltmeter data from JSS reveals a strong correlation between the model predictions and actual measurements, with correlation coefficients of 0.6 and 0.75 for strain in the NS and EW directions, and 0.8 and 0.9 for deformation in the NS and EW directions, respectively. These findings confirm that the 3D geological FEM is applicable for regional strain and deformation analysis, providing a feasible alternative in areas with limited GNSS monitoring. This method provides valuable insights into crustal deformation in regions with sparse strain and deformation measurement data.

High-Speed Three-Dimensional-Digital Image Correlation and Schlieren Imaging Integrated With Shock Tube Loading for Investigating Dynamic Response of Human Tympanic Membrane Exposed to Blasts.

Investigating the dynamic response of human tympanic membranes (TMs) exposed to blasts requires full-field-of-view and three-dimensional (3D) methodologies. Our paper introduces a system that combines high-speed 3D digital image correlation (HS 3D-DIC) and Schlieren imaging (HS-SI) with a custom-designed shock tube for generating blast waves. This integrated system allows us to measure TM surface motions under intense transient loading, capturing full-field-of-view shape deformations exceeding 100 μm with a temporal resolution of 10 μs. System characterization encompasses (i) measuring the shock tube's output levels and repeatability, (ii) assessment of the spatial and temporal resolutions of the imaging techniques, and (iii) identification of overall system limitations. Optimizing these factors is crucial for improving the reliability of our system to ensure the accurate measurement of deformations. To assess our shock tube's reliability in generating repeated blast waves, we instrumented it with high-pressure (HP) and high-frequency (HF) pressure sensors along the blast wave pathway to record overpressure waveforms and compared them with Schlieren imaging visualized blast waves. We validate our HS 3D-DIC measured deformations by comparing them with deformations measured using single-point laser Doppler vibrometry (LDV), establishing a comprehensive assessment of the TM's dynamic response and potential fracture mechanics under blast. Finally, we test our approach with 3D-printed TM-like samples and a real cadaveric human TM. This methodology lays the groundwork for further investigations of blast-related auditory damage and the invention of more effective protective and medical solutions.

Experimental method for internal deformation measurement of 3D solids with embedded cracks based on 3D printing and digital speckle techniques

Quantification of the internal deformation of fractured solids such as rock masses under external loads, especially the deformation around internal fractures, is crucial for understanding and predicting the failure of fractured solids. However, it is very difficult to achieve the goal using conventional experimental methods. In this study, we proposed a novel internal deformation measurement method based on three-dimensional (3D) printing and digital speckle techniques. The 3D printing technology was applied to fabricate a 3D transparent model with an embedded elliptical crack and to set a speckle pattern on the internal section of the transparent model. The digital image correlation (DIC) method was used to determine the internal deformation field of the 3D fractured model. The measured displacements and strains of the internal sections in the fractured model were compared with the numerical simulation results. The comparison indicates that the proposed experimental method can well determine the deformation inside the 3D model. This built-in speckle method can realize real-time observation of the internal deformation of a 3D solid model in a non-contact and non-destructive manner.

Light-tracing based surface deformation measurement strategy for large radio telescopes

Light-tracing based surface deformation measurement strategy for large radio telescopes

Development of a multibody model for go-karts considering frame flexibility

AbstractThis study focuses on the optimization dynamics of racing go-karts, which is heavily influenced by the frame's stiffness. Lacking suspensions and differentials, go-karts rely on the frame stiffness for wheel balancing and skid prevention by lifting the inner rear wheel during turns. Utilizing a rigid-flexible model in MSC Software ADAMS View, validated by frame deformation measurements, this research integrates finite element analysis with multibody techniques. The model, leverages computer aided design files for frame geometry and employs finite element analysis for frame validation. It facilitates evaluating go-kart dynamics through simulations, aiding in maneuver testing and design optimization. This approach provides a comprehensive framework for advancing go-kart designs.

Ultrasensitive Ultrasoft Buckled Crack‐Based Sensor for Respiration Measurement and Enhanced Human–Machine Interface

Wearable strain sensors have transformed the real‐time monitoring of health conditions and human–machine interactions. However, recently developed wearable strain sensors exhibit several limitations. For example, when a sensor is designed with high sensitivity to detect strain, it struggles to accurately measuring the deformation of low‐stiffness materials like skin. Additionally, finding the optimal balance between sensitivity, durability, hysteresis, and strain range in sensor design is challenging. To address these challenges, a Buckled, Ultrasoft, Crack‐based, Large strain, EpiDermal (BUCKLED) sensor is developed. This sensor integrates the benefits of soft structure engineering with high sensitivity of crack‐based sensing mechanisms to ensure optimal skin deformation measurements. The BUCKLED sensor exhibits significant improvements in compliance (18 500 mm N−1), stretchability (100%), hysteresis (2%), durability (10 000 cycles with 100% strain), and force sensitivity () owing to its buckled shape, confirming its ability to detect subtle movements with enhanced accuracy. The sensor's high compliance allows it to accurately measure low‐stiffness objects, ensuring reliable performance. Furthermore, the sensor's tunability is demonstrating its effectiveness in applications such as respiratory monitoring, facial expression recognition, and silent speech interfaces. Consequently, the proposed sensor is versatile and holds great potential for a wide range of sensing applications.

High lift devices using compliant surfaces

Stall delay and lift enhancement play a crucial role in modern aircraft performance. This is commonly achieved by devices such as slats or flaps located at the leading edge or trailing edge of an aircraft's wing. In this paper, we report a feasibility study of using light-weight compliant surfaces for novel high lift devices. The effects of compliant flags with one end fixed or both ends fixed near the leading edge and trailing edge of an airfoil were studied by force, flag deformation, and flow field measurements in a wind tunnel. When a flag is placed near the leading edge, the excitation of the separated shear layer from the leading edge is the main mechanism in increasing the lift at the post-stall angles of attack. In contrast, the trailing-edge flag with an excess length and both ends fixed could increase the effective camber and the circulation around the airfoil in a time-averaged sense. The mechanism is similar to that of the conventional Gurney flap effect, and equally effective at pre-stall and post-stall angles of attack. When used together, the compliant flags can delay stall angle by 8° and increase the maximum lift coefficient by 67% in the parameter range tested presently. Compliant surfaces require no external power as a passive method. If they are to be used as active methods, they are light weight, and can be stored and deployed easily.

Exploring the integration of InSAR data into climate‐driven creep models to assess slow‐moving landslide dynamics

AbstractThe deformation behavior of slow‐moving large landslides is often governed by rainfall characteristics. Based on observational data such as precipitation, deformation measurement, and pore water pressure measurements in the slip zone, in many cases a strong correlation between strong rainfall events, a time‐delayed increase of pore water pressures in the slip zone, and, simultaneously to this, an increase of the deformation rate of the landslide can be found. Based on such detailed data, calculation models, which couples the relation between rainfall characteristics and the development of pore water pressures in the slip zone on one hand and the deformation behavior of the slope on the other, can be developed and be used for a better understanding and a prediction of deformation behavior of such slow‐moving landslides. Climate change issues will lead to a change in rainfall frequency and magnitude and annual temperature distribution characteristics in several regions worldwide, which will also lead to changes in the deformation behavior of such large landslides. In this contribution, satellite‐based interferometric synthetic aperture radar (InSAR) data are discussed to be used as source for deformation measurements as bases for prediction models describing the rainfall‐triggered deformation behavior of slow‐moving landslides.

Gain-Based Feedback for Shape Control of Antenna Reflectors Using Deep Q-Network Algorithm

An intelligent shape control method for antenna reflectors is proposed using gain feedback instead of displacement feedback, considering the limitations of high-precision deformation measurement on orbit. Moreover, the finite element method is used to establish an analysis model of a grid reflector with embedded piezoelectric actuators, and the antenna gain formula is derived. To solve the multidimensional control laws from a single gain dimension, an active shape control model training framework is proposed based on the deep Q-network algorithm, including the state space, action space, and reward function. Numerical simulations, with errors stemming from two typical thermal loads as the initial errors, are conducted to illustrate the effect of the proposed control method. The influence of the voltage step size on the shape control precision is analyzed, and further online training is discussed for implementing control. The results indicate that the proposed method reduces the root-mean-square (RMS) error by more than 50% The control effect of the trained control model on other error conditions does not perform as desired. However, online training can effectively solve this problem, achieving faster convergence and a significant reduction of the RMS error.

A study on normal reference values of the left ventricular strain parameters in young adults

Background: The left ventricular (LV) function is an important prognostic determinant of cardiopulmonary pathologies in adult. Clinical application of cardiac strain by two-dimensional speckle tracking echocardiography to measure LV function requires knowledge of the range of normal values. Reference values and associated variations of the deformation measures need to be “firmly established before routine clinical adoption” of LV strain measurements can be implemented in Indian population. Aims and Objectives: This study aims to establish normal values of LV strain parameters in normal Indian population. Materials and Methods: An observational, cross-sectional, single-center, hospital-based study. The study period October 2021–October 2022 in Nil Ratan Sircir Medical College, Kolkata. Cardiologically healthy adult subjects (sample size 250) both male and female, aged 18–45 years who were healthcare professionals of this medical college and hospital were included in the study. Routine history taking and investigations were done. Echodoppler was done with special emphasis on LV strain parameters. Results: Distribution of mean LV circumferential strain (LVCS) with age in years was statistically not significant (P=0.8068). The mean value in male and female were −18.9574(±0.9049) and −19.0257(±0.8908) respectively. In the current study, LVCS did not vary in statistically significant a way among different age groups too. The mean values in male and female were −22.5887(±1.8065) and −22.3312(±1.9007) respectively. Conclusion: This current study failed to show significant differences in LV strain parameters between age groups or male and female in Eastern India Population.

Tunnel full-space deformation measurement based on improved downsampling and registration approach by point clouds

To fully leverage the volume measurement advantage of three-dimensional laser scanning technology in tunnel deformation monitoring, a full-space deformation analysis is proposed. A Box Improved Moving Average (BIMA) method featured by the adaptive window size downsampling is proposed which aims to achieve varying levels of downsampling in different densities regions. the combination of Maximal Cliques (MAC) and Iterative Closest Point (ICP) is utilized to achieve accurate registration. Point normal information is utilized to determine the correspondence to calculate deformation which shows an average accuracy of 7 % higher than the ICP by a convergence measurement test. The deformation convergence accuracy can go beyond 76 % when the point cloud reserved rate is approximately 10 %. Comparison between the method proposed in this study and the traditional point cloud cross sectional fitting method shows that the discrepancy between these two methods is approximately within 5 mm, with a minimum value of only 0.15 mm.

Deformation measurement of aero-engine rotating twisted blade based on multi-vision overlapping area feature registration method

Due to the complexity of the spatial surface of the twisted blade of the aero-engine, there are occlusions and shadows between the blades, resulting in visual blind spots. This causes the loss of certain information in the deformation measurement of twisted blade. A deformation measurement method of rotating twisted blades based on multi-vision overlapping area feature registration is proposed. It aims to solve the problem of limited field of view (FOV) in the deformation measurement of twisted blade, and overcome the problems of small measurement range and difficult measurement of traditional contact sensor method in the rotating state of the blade. First, a calibration and image-matching method based on multi-vision digital image correlation method is proposed. Under the premise of ensuring the simultaneous calibration of multi-vision camera stereo calibration, the matching of image detection points on the twisted blade surface is realized. Second, a three-dimensional reconstruction method based on the feature registration of the overlapping area of the FOV is proposed. It is used to solve the problem that the traditional image stitching method is prone to mismatching and to provide complete point cloud information for the deformation field calculation. Finally, the strain of each point is solved by piecewise point-by-point fitting of the local subdomains of the discrete displacement data, which suppresses the amplification of noise and improves the accuracy of blade strain calculation. In this paper, the deformation measurement experiment is carried out for the rotating twisted blade (up to 6000 rpm). The experimental results show that the proposed method can achieve a displacement measurement accuracy of 5 μm and the strain measurement accuracy of 50 με. This method can provide an important guarantee for the accurate evaluation and safe operation of the key performance parameters of the engine.

Fatigue Analysis of BRB Weld under Low Period and Large Deformation based on DIC Technology

This paper conducts an in-depth study on the fatigue performance of buckling-restrained braces (BRBs) under low-cycle large deformation conditions. As a device that utilizes the hysteretic energy dissipation of metal yielding, BRBs have been widely used in the design of new structures and the seismic strengthening of existing structures. Its remarkable advantages include stable performance, convenient fabrication, low cost, and excellent hysteretic performance. Applying DIC technology to the fatigue analysis of BRB welds under low-cycle large deformation can achieve full-field measurement of deformation and stress at the weld, providing strong technical support for in-depth study on the fatigue performance of BRB welds.

Research on bridge spatial deformation monitoring using light poles and displacement-relay theory

The growing traffic on municipal bridges demands effective methods for monitoring spatial deformations to ensure structural safety. Traditional measurement techniques often fall short in terms of efficiency and precision. This study presents an innovative bridge deformation measurement system that employs light poles and displacement-relay theory, integrated with high-resolution optical cameras, sub-pixel image recognition algorithms, and IMU data. Laboratory experiments involved chain camera units and multiple data processing methods, including sub-pixel recognition and wavelet denoising. Results showed that sub-pixel recognition with four-layer wavelet denoising achieved the highest accuracy, aligning closely matching the performance of commercial equipment. Field tests on the Xinwuyi and Dinghuaimen Bridges under varying traffic conditions confirmed the system’s reliability. The study concludes that the system effectively captures dynamic load variations, enhancing the accuracy of spatial deformation measurements. Future work will refine error analysis and data processing methods to further enhance the system’s practical applicability.

SSBAS-InSAR: A Spatially Constrained Small Baseline Subset InSAR Technique for Refined Time-Series Deformation Monitoring

SBAS-InSAR technology is effective in obtaining surface deformation information and is widely used in monitoring landslides and mining subsidence. However, SBAS-InSAR technology is susceptible to various errors, including atmospheric, orbital, and phase unwrapping errors. These multiple errors pose significant challenges to precise deformation monitoring over large areas. This paper examines the spatial characteristics of these errors and introduces a spatially constrained SBAS-InSAR method, termed SSBAS-InSAR, which enhances the accuracy of wide-area surface deformation monitoring. The method employs multiple stable ground points to create a control network that limits the propagation of multiple types of errors in the interferometric unwrapped data, thereby reducing the impact of long-wavelength signals on local deformation measurements. The proposed method was applied to Sentinel-1 data from parts of Jining, China. The results indicate that, compared to the traditional SBAS-InSAR method, the SSBAS-InSAR method significantly reduced phase closure errors, deformation rate standard deviations, and phase residues, improved temporal coherence, and provided a clearer representation of deformation in time-series curves. This is crucial for studying surface deformation trends and patterns and for preventing related disasters.

High strain rate tensile deformation of similar and dissimilar AA6082 and AA7075 friction-stir-welded blanks

Friction-stir-welding process has become an established solid-state technique for joining of dissimilar lightweight materials over the past decade by overcoming fundamental welding challenges such as solidification cracking, phase segregation and surface oxidation. Despite these unique capabilities, the resulting microstructure feature in the weld zone consisting of fine grains with a high dislocation density, challenges further heat treatment and forming processes. Hence, a high solution annealing temperature results in degradation of the adjusted microstructure and in a lower to reduced mechanical properties in case of dissimilar joints of precipitation-hardenable aluminum alloys. Subsequent hot forming therefore involves a great effort and requires further heat treatment steps. Thus, the present study investigates the effect of a recently introduced novel thermo-mechanical forming process on local deformation behavior of similar as well as dissimilar joints processed by friction-stir-welding technique of thin-walled AA6082 and AA7075 blanks. To avoid the complete elimination of the adjusted microstructure, the welding process is performed after a thermo-mechanical process consisting of solution annealing, die cooling and peak aging. Uniaxial tensile tests are then carried out at high strain rates ranging from ε˙ = 40 s-1 to ε˙ = 400 s-1. The results show an increase in yield and ultimate tensile strength as well as in total elongation after failure with increasing strain rates. As the strain rate increases, the flow stress of similar weld of AA7075 is higher than those of AA6082 and the dissimilar weld of AA6082 and AA7075. Local deformation measurements reveal higher strain localization in the welded zone for similar welds, which leads to micro-crack initiation and failure due to strain accumulation. Microstructure analysis shows very fine equiaxed grain structure in the nugget zone and homogenous distribution of precipitates after friction stir welding process, which explain the plastic deformation behavior.

Fetal and neonatal echocardiographic analysis of biomechanical alterations for the systemic right ventricle heart

Background The perinatal transition’s impact on systemic right ventricle (SRV) cardiac hemodynamics is not fully understood. Standard clinical image analysis tools fall short of capturing comprehensive diastolic and systolic measures of these hemodynamics. Objectives Compare standard and novel hemodynamic echocardiogram (echo) parameters to quantify perinatal changes in SRV and healthy controls. Methods We performed a retrospective study of 10 SRV patients with echocardiograms at 33-weeks gestation and at day of birth and 12 age-matched controls. We used in-house developed analysis algorithms to quantify ventricular biomechanics from four-chamber B-mode and color Doppler scans. Cardiac morphology, hemodynamics, tissue motion, deformation, and flow parameters were measured. Results Tissue motion, deformation, and index measurements did not reliably capture biomechanical changes. Stroke volume and cardiac output were nearly twice as large for the SRV compared to the control RV and left ventricle (LV) due to RV enlargement. The enlarged RV exhibited disordered flow with higher energy loss (EL) compared to prenatal control LV and postnatal control RV and LV. Furthermore, the enlarged RV demonstrated elevated vortex strength (VS) and kinetic energy (KE) compared to both the control RV and LV, prenatally and postnatally. The SRV showed reduced relaxation with increased early filling velocity (E) compared prenatally to the LV and postnatally to the control RV and LV. Furthermore, increased recovery pressure (ΔP) was observed between the SRV and control RV and LV, prenatally and postnatally. Conclusions The novel hydrodynamic parameters more reliably capture the SRV alterations than traditional parameters.