Deformation Measurement Research Articles

Impact Analysis of Welding Sequence to Reduce Weld Deformation in Aluminum Hulls

Aluminum hulls, which are preferred in the marine industry due to their durability, corrosion resistance, and lightweight properties, face serious challenges due to thermal deformation during welding. This study aims to predict and minimize transverse deformations due to welding sequences for a transverse model in the lower part of an aluminum hull. To predict deformations, heat source dimensions obtained from actual weld beads were used as simulation conditions, and various welding sequence conditions were simulated through the developed finite element method (FEM). The simulation results were compared with actual deformation measurements to verify their reliability, and the optimal welding sequence which minimized deformation was derived. The simulation results show that by changing the welding sequence conditions, the maximum displacement can be reduced from a maximum of 52.1% to a minimum of 39.1%, and the effective plastic strain can be reduced from a maximum of 19.6% to a minimum of 4.8%. These results show that adjusting the welding sequence conditions can significantly improve structural integrity by minimizing deformation. The results of this study suggest that the control of the welding sequence can be used to reduce the deformation of aluminum hulls and promote a more sustainable marine industry with improved quality.

Numerical simulation of rainfall-induced deformations of embankments considering the coupled hydro-mechanical behavior of unsaturated soils

This paper presents numerical simulations of the deformation response of unsaturated embankments subjected to rainfall infiltration using a coupled hydro-mechanical constitutive model for unsaturated soils. The constitutive model accounts for the influence of degree of saturation on the stress–strain behavior and the influence of void ratio on the water retention behavior. The constitutive model was implemented in the finite difference program FLAC, calibrated using triaxial test data, and validated using measurements of wetting-induced deformations of embankment models from centrifuge tests. The validation demonstrates that the constitutive model can capture the coupled hydro-mechanical behavior of unsaturated soils under wetting conditions. Simulations of the hydro-mechanical response of unsaturated embankments subjected to rainfall infiltration indicate that the differential settlement across the top surface of the embankment between the centerline and shoulder increases significantly during rainfall infiltration, which could result in severe damage to overlying transportation infrastructure. As the rainfall infiltration increases, shear strains accumulate and form a potential failure surface at a shallow depth of approximately 2 m from the slope surface. Insights into the hydro-mechanical response of unsaturated embankments subjected to rainfall infiltration gained will be useful for considering climate change effects in design and construction of compacted embankments.

Dynamic deformation measurement with 2-frame phase-shifting speckle interferometry based on speckle statistics and wavefront multiplexing.

Phase-shifting speckle interferometry could achieve full-field deformation measurement of rough surfaces. To meet the dynamic requirement and further improve the accuracy, a two-step synchronous phase-shifting measurement system is established based on the polarization-sensitive phase modulation ability of a liquid crystal spatial light modulator; by multiplexing the reference wavefront, an accurate phase shift is generated between two independent recording channels, and a common-path self-reference vortex interference structure is built for precise spatial registration. Meanwhile, according to the speckle statistical principle, a novel two-frame phase-shifting algorithm as well as a two-step spatial registration strategy is presented to strengthen the robustness of intensity and position differences caused by spatial-multiplexing; thereby, accurate transient deformation can be directly obtained from phase-shifting speckle interferograms recorded before and after deformation. The effectiveness and accuracy of the proposal are validated from the out-of-plane deformation measurement experiment by comparing with the traditional two-step and four-step phase-shifting methods. The dynamic ability is exhibited through reconstructing mechanical and thermal deformations across various application scenarios.

An Evaluation of Backfill Material Applicability through Deformation Measurements of Long-Span Buried Corrugated Steel Structures

Corrugated steel plates are increasingly being applied to various types of structures, such as eco-corridors, noise reduction tunnels, and urban elevated roads. However, applications for spans exceeding 25 m are lacking, as they require clear standards for calculating the elastic moduli of backfill materials and reinforced sections. This study evaluated the appropriateness of mechanical assumptions applied in the design, by measuring displacements at each stage and comparing the finite element analysis results for a concrete-reinforced corrugated steel plate arch underground structure with a width of 27.5 m and length of 467 m. Based on the measurement results, deformations ranging from 19.8% to 63.7% of allowable deflection were observed when applying an elastic modulus of 60 MPa to solidified soil backfill, which is twice the maximum standard value applied to general soil, thereby confirming the suitability for the serviceability of underground structures.

The White Matter Fiber Tract Deforms Most in the Perpendicular Direction During In Vivo Volunteer Impacts.

White matter (WM) tract-related strains are increasingly used to quantify brain mechanical responses, but their dynamics in live human brains during invivo impact conditions remain largely unknown. Existing research primarily looked into the normal strain along the WM fiber tracts (i.e., tract-oriented normal strain), but it is rarely the case that the fiber tract only endures tract-oriented normal strain during impacts. In this study, we aim to extend the invivo measurement of WM fiber deformation by quantifying the normal strain perpendicular to the fiber tract (i.e., tract-perpendicular normal strain) and the shear strain along and perpendicular to the fiber tract (i.e., tract-oriented shear strain and tract-perpendicular shear strain, respectively). To achieve this, we combine the three-dimensional strain tensor from the tagged magnetic resonance imaging with the diffusion tensor imaging (DTI) from an open-access dataset, including 44 volunteer impacts under two head loading modes, i.e., neck rotations (N = 30) and neck extensions (N = 14). The strain tensor is rotated to the coordinate system with one axis aligned with DTI-revealed fiber orientation, and then four tract-related strain measures are calculated. The results show that tract-perpendicular normal strain peaks are the largest among the four strain types (p < 0.05, Friedman's test). The distribution of tract-related strains is affected by the head loading mode, of which laterally symmetric patterns with respect to the midsagittal plane are noted under neck extensions, but not under neck rotations. Our study presents a comprehensive invivo strain quantification toward a multifaceted understanding of WM dynamics. We find that the WM fiber tract deforms most in the perpendicular direction, illuminating new fundamentals of brain mechanics. The reported strain images can be used to evaluate the fidelity of computational head models, especially those intended to predict fiber deformation under noninjurious conditions.

A measurement system for assessing the completeness and deformation of aluminium ladders: case study

Aluminium ladders are popular tools used in many fields of industry and construction. Their completeness and durability are key to ensure work safety and avoid dangerous scenarios. To provide safety to aluminium ladders, it is necessary to perform completion checks and measurements of ladder deformation are necessary during operation. This article presents a measurement system to assess the completeness of aluminium ladders and describes the use of the GOM Pontos system to measure the deformation of the ladder during operation. The main purpose of the research was to verify whether the system proposed by the authors works successfully and the results obtained allow it to be deployed in the production line. Research results and conclusions can provide a basis for further research and may help improve the production and utilisation processes of aluminium ladders. The research was carried out in a company that is engaged in the production of aluminium ladders. This allowed a thorough examination of the efficiency and effectiveness of the proposed methods under real production conditions, which is crucial for the practical implementation of this technology in the industry.

Untrained single scanning phase retrieval neural network for surface deformation measurement of large-aperture antennas

Research on data-driven Fourier phase retrieval neural networks is well-established. However, in many practical applications, such as phase retrieval-based antenna surface deformation measurements in astronomy, obtaining a sufficient number of ground truth images for training is unlikely. In this paper, we propose a purely physics-driven neural network model for retrieving the aperture-field phase of large antennas. This is accomplished through the integration of the physical model describing the interaction between the aperture-field and the far-field with the neural network. Our simulations and experiments demonstrate accurate reconstruction of the aperture-field phase using only a single far-field intensity image. Furthermore, we present a solution tailored for scenarios with low signal-to-noise ratio.

How to identify earth pressures on in-service tunnel linings: Insights from Bayesian inversion to address non-uniqueness

Identifying earth pressures on in-service transportation tunnel linings is essential for their health monitoring and performance prediction, particularly in structures that exhibit poor performance. Due to the high costs associated with pressure gauges, pressure inversion based on easily observed structural responses, such as deformations, is preferred. A significant challenge lies in the non-uniqueness of inversion results, where various pressures can yield similar structural responses. Existing approaches often overlook detailed discussions on this critical issue. In addressing this gap, this study introduces a Bayesian approach. The proposed statistical framework effectively quantifies the uncertainty induced by non-uniqueness. Further analysis identifies the uniform component in distributed pressures as the primary source of non-uniqueness. Insights into mitigation strategies are provided, including increasing the quantity of deformation data or incorporating an observation of internal normal force within the tunnel lining — the latter proving to be notably more effective. A practical application in a numerical case study demonstrates the effectiveness of this approach. In addition, our investigation recommends maintaining deformation measurement accuracy within the range of [–1, 1] mm to ensure satisfactory outcomes. Finally, deficiencies and potential future extensions of this approach are discussed.

Mechanism clarification and mitigation measures of radial deformation induced by girth welding of thin-walled pipes

Girth welding is extensively utilized in connecting pipeline structures. Excessive welding deformation may result in a decrease in ultimate bearing capacity and fatigue life. This research explores the characteristics and underlying mechanics of radial deformation in thin-walled girth welded pipes and proposes mitigation measures. Initially, several 304 stainless steel pipes were joined utilizing four distinct welding procedures. Welding deformation and residual stress distribution were measured using a 3D coordinate measuring machine (CMM) and the Cos α X-ray diffraction (XRD) method, respectively. Subsequently, numerical models were developed to simulate the welding process and verify the accuracy of the fusion zone, residual stress field, and radial deformation in the models. The mechanism of radial deformation was further elucidated based on the inherent strain method. The results show that the direction of radial deformation relies substantially on the hoop plastic strain. Hoop tensile plastic strain corresponds to radial outward deformation, while hoop shrinkage plastic strain corresponds to radial inward deformation. In addition, the influence of axial constraint on the formation process and results of hoop plastic strain, as well as the effect of heating zone width on radial deformation, was studied. Through simulation outcomes, the research suggests employing a regulated heat source method to mitigate radial deformation, which could potentially reduce deformation by 92.8%, offering considerable advantages in deformation mitigation and welding efficiency augmentation.

In-situ observation and quantification of membrane deformation in reverse osmosis, using optical coherence tomography

Deformation of the membrane can seriously hamper the performance of a reverse osmosis process. Currently, the most used approach to obtain detailed information on membrane deformation is by conducting membrane autopsy. However, ex-situ analysis can only observe irreversible deformation. In this study, optical coherence tomography (OCT) was introduced as method for in-situ 3D visualization and quantification of membrane and feed channel deformation during operation with varying transmembrane pressure (0–55 bar). In-situ monitoring of membrane surface geometry in a lab-scale flow-cell revealed the formation of specific patterns with ridges and valleys. The deformation became more pronounced with increasing applied pressure, due to membrane intrusion into the permeate spacer. The asymmetric structure of the permeate spacer causes a clear distinction in spatial distribution of ridges and valleys, depending on which side faces the membrane. Interestingly, membrane surface displacement increased linearly with TMP, with slope depending on spacer orientation (A vs B) and type (BW vs SW). Under pressure, we found the following displacements: Ridge – BW-A 1.7 ± 0.1 μm/bar, BW-B 1.9 ± 0.1 μm/bar, SW-A&B 1.5 ± 0.3 μm/bar; Valley – BW-A 3.2 ± 0.1 μm/bar, BW-B 2.7 ± 0.1 μm/bar, SW-A 1.7 ± 0.2 μm/bar, SW-B 1.8 ± 0.3 μm/bar. Measuring the membrane position under pressure revealed that the displacement involves the whole membrane-permeate spacer structure, i.e., the permeate spacer is also deformed. By alternating high and low feed pressure, we could distinguish between reversible and irreversible deformation. In-situ measurement of membrane deformation can contribute to understanding of pressure related performance and can serve as input for advanced modeling.

Influence of sand layer thickness on the collapse mechanism of tunnels in soil-sand-rock composite strata

Collapse is a severe event during metro tunnel construction, particularly in soil-sand-rock composite strata. Variations in the thickness of sand layers, owing to their high compressibility, flowability, and thixotropic properties, significantly impact the mechanical response and deformation of strata, which also directly determine the stability of tunnel excavation processes. Regarding the complexity of the engineering response of the soil-sand-rock composite strata, a series of model tests were conducted to reveal the collapse mechanism of the metro tunnel in the soil-sand-rock composite strata subjected to varying sand layer thickness in this paper. Meanwhile, the influence of sand thickness on the evolution of collapse form, the response of strata stress, and the variation of the displacement and strain fields were systematically discussed by the monitoring data from the miniature earth pressure cells and a two-dimensional full-field deformation measurement system. Moreover, the collapse evolution process was recorded by the industrial camera. The test results indicated that the horizontal displacement of the tunnel shoulders was more affected by the increase in sand layer thickness than the horizontal displacement of the haunches before the tunnel collapse. The high compressibility of the sand layer resisted the transmission of surcharge load to the rock layer. Once the overlying rock layer above the tunnel vault lost its bearing capacity, the thixotropy and flowability properties of the sand layer caused the collapse face to expand funnel-shaped to both sides. The collapse width of the sand-soil interface was proportional to the sand layer thickness. The greater the sand layer thickness, the weaker the ability to provide stable support for the foot of the temporary stratigraphic arch, further reducing the stability of the temporary stratigraphic arch and leading to a faster collapse rate of the composite strata. In general, the results of this research offer valuable guidance for preventing and controlling tunnel collapse in soil-sand-rock composite strata.

Evaluation of changes in cardiac longitudinal strain rate in patients with systemic sclerosis undergoing iloprost treatment: an observational study.

Systemic Sclerosis (SSc) is characterized by widespread microangiopathy and fibrosis of skin and visceral organs. Left ventricle involvement is usually subclinical, characterized by systolic and/or diastolic dysfunction. The global longitudinal strain (GLS), a validated and reliable technique for the measurement of ventricular longitudinal deformation by means of echocardiography, may detect subclinical systolic dysfunction of SSc myocardium. The improvement of myocardial perfusion by means of intravenous Iloprost administration could ameliorate the contractility of SSc heart. Therefore, we aimed to evaluate GLS in a series of SSc patients prior and after Iloprost infusion. Fifteen consecutive SSc patients (age: 54 ± 11 years; 12 females) treated with Iloprost because of the presence/history of digital ulcers underwent echocardiography, including GLS technique. This evaluation was conducted immediately before Iloprost administration and at the end of the 6-h infusion session. Significant improvement in the mean GLS was observed after Iloprost administration (from -13.5 ± 2.5 to -15 ± 3.3; p= 0.011). The echocardiographic data obtained from the four-chamber view showed the best quality for GLS analysis and showed a highly significant improvement of the strain after Iloprost administration (from -13.4 ± 2.2 to -15.6 ± 3; p= 0.001). The degree of GLS improvement did not correlate with any SSc parameters. Iloprost administration improved GLS, suggesting that the increase of myocardial perfusion allowed, at least in part, a correction of left ventricular systolic dysfunction. Further studies are needed to confirm these findings, further exploring the mid/long-term effects of Iloprost on myocardial contraction.

Poisson function and volume ratio of soft anisotropic materials under large deformations

Accurate transverse deformation measurements are required for the estimation of the Poisson function and volume ratio. In this study, pure silicone and soft composite specimens were subjected to uniaxial tension, and the digital image correlation method was used to measure longitudinal and in- and out-of-plane transverse stretches. To minimize the effects of measurement errors on parameter estimation, the measured transverse stretches were defined in terms of the longitudinal stretch using a new formulation based on Poisson's ratios and two stretch-dependent parameters. From this formulation, Poisson functions and volume ratio for soft materials under large deformations were obtained. The results showed that pure silicone can be considered isotropic and nearly incompressible under large deformations, as expected. In contrast, Poisson's ratio of silicone reinforced with extensible fabric can exceed classical bounds, including negative value (auxetic behavior). The incompressibility assumption can be employed for describing the stress-stretch curve of pure silicone, while volume ratios are required for soft composites. Data of human skin, aortic wall, and annulus fibrosus from the literature were selected and analyzed. Except for the aortic wall, which can be considered nearly incompressible, the studied soft tissues must be regarded as compressible. All tissues presented anisotropic behavior.

Full-field, frequency-domain comparison of simulated and measured human brain deformation.

We propose a robust framework for quantitatively comparing model-predicted and experimentally measured strain fields in the human brain during harmonic skull motion. Traumatic brain injuries (TBIs) are typically caused by skull impact or acceleration, but how skull motion leads to brain deformation and consequent neural injury remains unclear and comparison of model predictions to experimental data remains limited. Magnetic resonance elastography (MRE) provides high-resolution, full-field measurements of dynamic brain deformation induced by harmonic skull motion. In the proposed framework, full-field strain measurements from human brain MRE in vivo are compared to simulated strain fields from models with similar harmonic loading. To enable comparison, the model geometry and subject anatomy, and subsequently, the predicted and measured strain fields are nonlinearly registered to the same standard brain atlas. Strain field correlations , both global (over the brain volume) and local (over smaller sub-volumes), are then computed from the inner product of the complex-valued strain tensors from model and experiment at each voxel. To demonstrate our approach, we compare strain fields from MRE in six human subjects to predictions from two previously developed models. Notably, global values are higher when comparing strain fields from different subjects ( ) than when comparing strain fields from either of the two models to strain fields in any subject. The proposed framework provides a quantitative method to assess similarity (and to identify discrepancies) between model predictions and experimental measurements of brain deformation, and thus can aid in the development and evaluation of improved models of brain biomechanics.

Measurement and calculation of neutron flux deformation during rod drop transient at the VR-1 reactor

The rod drop experiment was performed at the VR-1 reactor to test the detection system and collect data that describe the development of neutron flux during rod drop. This experiment was calculated in Serpent code by its dynamic part. During this experiment, an additional control rod for drop was placed in the reactor with a channel directly attached to the rod guide tube containing the detection system. The detection system developed for this experiment is based on diamond detectors and allows measurement of neutron flux development during the rod drop in almost point vise location. The results of both experiment and calculation showed a delay in the count rate drop influenced by the position of the rod during the drop. The obtained experience is also used in the design process of a new experimental device dedicated to rod drop measurements that will allow the direct rod position measurement during the drop.

Spatio-Temporal Compressive Behaviors of River Pebble Concrete and Sea Pebble Concrete in Island Offshore Engineering

Obtaining river or sea pebbles from local resources for concrete production is considered an economical and eco-friendly alternative, particularly in marine and island-offshore engineering. However, the resulting changes in the mechanical properties of these concrete have attracted attention. This study investigates the compressive behavior of concretes where river or sea pebbles partially (i.e., 33% and 67%) or fully (i.e., 100%) replace traditional gravel as coarse aggregate, using a noncontact full-field deformation measurement system based on digital image correlation (DIC). Compared to the traditional gravel concrete (GC), compressive strengths of the river pebble concrete (RPC) at constitution rates of 33%, 67%, and 100% decreased by 6.5%, 29.8%, and 38.9% while those values of the sea pebble concrete (SPC) decreased by 13.1%, 32.7%, and 44.3%, respectively. Meanwhile, SPC exhibited slightly lower compressive strength than RPC. The peak strains of both SPC and RPC decreased at lower substitution rates, although their stress-strain curves resembled those of GC. In contrast, RPC and SPC at higher substitution rates exhibited a noticeable stage of load hardening. Full-field deformation data and interfacial characteristics indicated that the compressive failure modes of both RPC and SPC showed significant interfacial slipping between pebbles and mortar with increasing coarse aggregate substitution rates. In comparison, fractures in coarse aggregate and mortar were observed in damaged GC. The study demonstrated that the spatio-temporal compressive deformation response and failure modes of SPC and RPC were distinct due to the introduction of pebbles, providing insights for engineering applications of river/sea pebble concrete in practical offshore or island construction projects.

Dextractor:Deformation Extractor Framework for Monitoring-Based Ground Radar

The radio frequency (RF) data generated from a single-chip millimeter-wave (mmWave) ground-based multi-input multi-output (GB-MIMO) radar can provide a highly robust, precise measurement for deformation in harsh environments, overcoming challenges such as different lighting and weather conditions. Monitoring deformation is significant for safety factors in different applications, such as detecting and monitoring the ground stability of underground mines. However, radar images can experience different types of clutter and artifacts besides the spreading effects caused by the side lobes, resulting in the foremost challenge of suppressing clutter and monitoring deformation.In the state of the art, the introduced frameworks usually include many filters proposed for different types of noise, with commercial systems typically using an amplitude threshold. This paper proposes a framework for monitoring the deformation, where the essential process is to apply a data-driven threshold to the amplitude heatmap, detect the deformation, and eliminate noise. The proposed threshold is an iterative approach based on radar imagery statistics, and it performs well for the collected dataset. The principal advantage of our proposed framework is simplicity, reducing the burden of using different filters. We can consider the dynamic threshold based on data statistics as a data-driven machine learning tool. The results show promising performance for our method in monitoring the deformation and removing clutter compared to the benchmark method.

Effectiveness Spatiotemporal of Pressure Unloading and Gas Extraction in Remote Upper Protected Seam Mining.

Severe gas hazards are increasing in deep mining areas, and there exists an enormous traditional challenge for protected seam mining. In this work, we conducted a multifaceted investigation into the spatiotemporal effectiveness exerted by pressure unloading from a distant safeguarded stratum in concert with the application of gas extraction methodologies. The stress and displacement evolution in the protected coal seam (PCS) are analyzed by applying Flac3D, and then positives are verified by the measurement of coal seam deformation and investigation of the unloading boundary. The results show that diminution coefficient of 0.62, and record an expansive deformation rate of 5.83%. The opportune temporal window for effective gas drainage is discerned, with its time window spans from 58 to 67 days as the expanse between 350 and 400 m progresses at the working face. Continuous and effective gas extraction occurs when transverse cracks in the PCS reach an optimal state of pressure relief. The final cumulative gas extraction was 320,300 m3 with an extraction efficiency of 34.3%. A residual gas volume of 3.68 m3/t and a residual gas pressure of 0.5 MPa reflect the efficient gas extraction.

Identifying Lower Extremity Deformities in the Coronal Plane: Lessons From Remote Learning During the COVID-19 Pandemic.

Introduction During the COVID-19 pandemic, the AO Foundation, an orthopedic education organization, had to transition its live education programs to an online format. Skills that were previously evaluated and corrected in person by educators were now assessed through online lectures and discussion groups. Our goal was to evaluate an online course designed to teach the skill of "leg length and coronal deformity measurement" and to assess participants' ability to demonstrate this skill using online software. Methods An IRB-approved study was conducted during an online osteotomy course. A total of 176 participants were instructed on how to measure length and angulation through the course lectures and planning tutorials. The Bonesetter App (Detroit Bonesetter, Detroit, Michigan, USA) was used as the digital planning tool. Participants analyzed four cases of coronal deformity using long-leg standing radiographs. They were required to identify any deformities present, specify the type of deformity, and determine whether it affected the femur, tibia, or joint. Additionally, participants needed to calculate the deformity as part of the osteotomy planning process. Their measurements and drawings were saved and subsequently evaluated by two independent observers. Results Out of 176 online participants, 76% (315 out of 417) correctly completed the four exercises. The most frequent errors occurred in measuring total deformity and joint deformity. The average standard deviation of length measurements was ±0.29 cm (based on 244 measurements), while for angular measurements, it was ±0.71 degrees (based on 688 measurements). The intraclass correlation coefficient was greater than 0.96. Conclusions The online course effectively taught coronal deformity measurement, although participants struggled most with measuring joint angles and total deformity. Future courses should provide more detailed explanations for these measurements.

A simple computational model for scleral stiffness assessments via air-puff deformation OCT.

Introduction: The mechanical properties of the sclera are related to its structural function, and changes to these properties are believed to contribute to pathologies such as myopia. Air-puff deformation imaging is a tool that uses an imaging system coupled with an air-puff excitation source to induce and measure deformation in a tissue in vivo. Typically used for the study of the cornea's mechanical properties and IOP, this tool has been proposed as a method to evaluate scleral stiffness. Methods: In this work, we present a computational model of the rabbit eye to assess scleral deformation under air-puff. Parametric studies were conducted to evaluate the effects of material properties, intraocular pressure, and other parameters on the deformation response. Output from the model was also compared to experimental measurements of air-puff deformation in rabbit eyes under varying IOP. Results: Central deformation response was found to be most influenced by material properties of the sclera (at site of air-puff and posterior), thickness, and IOP, whereas deformation profile was most influenced by material properties. Experimental and simulated IOP dependence were found to be similar (RMSE = 0.13mm). Discussion: Scleral APDI could be a useful tool for quick in vivo assessment of scleral stiffness.