Deformation Field Research Articles

A Trust‐Region Method for p‐Harmonic Shape Optimization

ABSTRACTThe appropriate scaling of deformation fields has a significant impact on the performance of shape optimization algorithms. We introduce a pointwise gradient constraint to an efficient algorithm for ‐Laplace problems, while the complexity of the algorithm remains polynomial. Using this algorithm, we compute descent directions for shape optimization using ‐harmonic approach that fulfill a trust‐region type constraint. Numerical experiments show the advantages of deformations computed with this approach when compared to deformations that are scaled after computation. This considers, in particular, the approximation of the limit setting and the preservation of mesh quality during an optimization with a fixed step size.

Signal response and energy evolution of separated sandstone

This study aims to establish a precise prediction system for strong rockbursts and mine earthquakes caused by high-hard roof fractures. A three-point bending test was conducted on separated sandstone (SS) to analyze deformation field changes under the influence of digital image correlation (DIC) and acoustic emission (AE) signals during rock fracture. Microscopic fracture modes and energy evolution patterns of SS are investigated using scanning electron microscopy and Particle Flow Code in 2 Dimension, revealing the internal mechanisms linking fracture modes, crack classifications, and energy evolution. The results show that the AE signals and DIC deformation fields are highly correlated. Tensile cracks are the primary indicator of damage to SS during the strong contact phase. Complete failure occurs at peak load, driven by a combination of tensile and shear cracks. Increasing the precast crack length (b) or the upper-to-lower rock layer thickness ratio (U/L) enhances tensile failure sensitivity, whereas simultaneous increases reduce it. Macroscopically, this is reflected in variations of AE peak frequency and the primary fracture's peak frequency. Microscopically, it appears as changes in fracture surface roughness and grain fracture morphology. Energetically, this is evident in changes to the ratios of strain energy and slip energy relative to total energy. Additionally, as b and U/L increase, the primary crack location and AE energy density concentration shift progressively from the lower to the upper rock layers. Meanwhile, total input energy decreases with increasing b or as U/L deviates from 1.

+SSLIP: Automated Radon‐Assisted and Rotation‐Corrected Identification of Complex HCP Slip System Activity Fields from DIC Data

ABSTRACTIdentification of crystallographic slip in metals and alloys is crucial to understand and improve their mechanical behaviour. Recently, a novel slip system identification framework, termed SSLIP (for slip system–based local identification of plasticity), was introduced to leap from conventional trace‐based identification to automated, point‐by‐point identification, exploiting the full deformation kinematics. Using sub‐micron‐scale digital image correlation (DIC) deformation fields aligned to electron backscatter diffraction (EBSD) data, SSLIP matches the measured in‐plane displacement gradient tensor to the kinematics of the optimal combination of multiple slip system activities, at each DIC datapoint. SSLIP was demonstrated to be successful on virtual and experimental case studies of FCC and BCC metals. However, for more challenging HCP crystal structures, the complete identification of all slip systems was found to be more challenging, posing limitations on automation and flexibility. To extend the capabilities of SSLIP, we propose an extended framework, hereinafter referred to as the +SSLIP method, which includes (i) a preselection of slip systems using a Radon transform, (ii) robustness to measured rigid body rotation by simultaneous identification of the local rotation field, (iii) identification of the two best matching slip systems for each data point and (iv) a procedure to determine groups of slip systems with in‐plane displacement gradient tensors that cannot be discriminated. This procedure yields the full (HCP) slip system activity maps for every slip system in each grain. The resulting objective identification method does not rely on the Schmid factor to select which slip system is active at each point. We show how slip systems from multiple slip families are successfully identified on virtual and real experiments on a Zn polycrystalline coating.

Influence of creep–slip fracture length on the local deformation field and fracture characteristics of rock-like models

Influence of creep–slip fracture length on the local deformation field and fracture characteristics of rock-like models

Influence of heat input and heat exchange coefficient on temperature and stress field of a X80 steel pipeline repair-weld root pass of a type-B sleeve

Abstract The formation of the type-B sleeve repaisring root pass seriously affects the quality of in-service repair of B-type sleeve. Therefore, it is necessary to systematically study the temperature field, stress field, and deformation field of type-B sleeve repairing root pass. In this paper, a double ellipsoid heat source model is developed to investigate the weld temperature, residual stress, and deformation field characteristics in the type-B sleeve repairing root pass. The results show that the heat exchange coefficient of the inner wall of the pipeline has a relatively small impact on the penetration depth, residual stress, and deformation of type-B sleeve repairing root pass, and the weld heat input has a significant impact on the penetration depth, residual stress, and deformation of type-B sleeve repairing root pass. In a whole, when the heat input of the repairing root pass is around 0.9 KJ mm−1, a well-formed repairing root pass with moderate residual stress and minimal deformation can be obtained.

BabyFM: Towards accurate 3D baby facial models using spectral decomposition and asymmetry swapping.

In this paper, we present the first publicly available 3D statistical facial shape model of babies, the Baby Face Model (BabyFM). Constructing a model of the facial geometry of babies entails specific challenges, such as occlusions, extreme and uncontrollable expressions, and data shortage. We address these challenges by proposing (1) a non-template dependent method that jointly estimates a 3D facial baby-specific template and the point-to-point correspondences; (2) a novel method to establish correspondences based on the spectral decomposition of the Laplace Beltrami Operator, which provides a more robust theoretical foundation than state-of-the-art methods; and (3) an asymmetry-swapping strategy to alleviate the shortage of large scale datasets by decoupling the identity-related and the asymmetry-related shape deformation fields. The latter leads to a data augmentation technique that we integrate within the Gaussian Process Morphable Model framework, providing a simple way of combining synthetic or sample covariance functions. We exhaustively evaluate each stage of our method and demonstrate that (1) when aiming at the 3D facial geometry of a baby, a specific model of babies is needed, since the pre-built publicly available models constructed with adults or older children are not able to accurately represent the facial shape of babies; (2) our spectral approach improves correspondences accuracy with respect to state-of-the-art-methods; and (3) the proposed data augmentation technique enhances the robustness of the BabyFM.

Influence of Bubble Size on Hydrodynamics in Shear–thinning Liquids

Introduction: Bubble rising behavior in shear-thinning liquids was simulated using a volume of fluid (VOF) method. Method: The authors conducted a detailed analysis of the effects of bubble diameter D, inelastic relaxation time (λ), and rheological index (n) on bubble deformation and flow fields. objective: It can be seen from the above review that the overwhelming majority of the present investigations on the rising behaviour of bubbles in the shear-thinning liquids focus on the effect of liquid-phase rheological parameters such as the flow index and the inelastic time constant on the bubble hydrodynamics. As a matter of fact, the bubble size is a very important parameter for the bubbly system, which determines the residence time of bubbles and the void fraction in a bubbly system. Therefore, it is essential to investigate the dependence of hydrodynamics on the bubble size in the shear-thinning liquids. In this paper, the authors investigated the rising behavior of the bubbles with different diameter in the shear-thinning liquids in detail. Result: The results indicated that bubble diameter significantly affects bubble dynamics. Bubble terminal velocity tends to stabilize within a certain diameter range rather than continuously increasing with an increase in bubble diameter, and this trend is particularly noticeable when the shearthinning effect of liquid is strong— with an increase in λ, the region and degree of a decrease in apparent viscosity increase, causing bubble deformation and terminal velocity to increase. A reduction in n leads to an increase in bubble terminal velocity and deformation degree. Conclusion: These findings have potential implications for patent applications in industrial fields involving shear-thinning liquids containing bubbles.

Deformation Field Fusion for Medical Image Registration

Deformation Field Fusion for Medical Image Registration

Deep Learning‐Based Optical Flow in Fine‐Scale Deformation Mapping of Sea Ice Dynamics

AbstractOptical methods deployed for studying motion and deformation of objects often struggle to distinguish small displacements hidden behind observational noise. In geophysical applications, this has limited analysis to lower spatial and temporal resolutions, while reliable extraction of high‐resolution data is required for understanding material deformation and failure. In this work, we propose a novel method for determining deformation for noisy observational data using deep learning‐based optical flow. To enable higher estimate accuracy, we introduce a novel initialization technique considering contextual information. This allows an unprecedentedly high‐resolution description of motion in radar imagery. We use the proposed technique on verification cases to compare with the currently used methodologies and on ship radar observations on sea ice deformation. The outcome of our work is an open‐source end‐to‐end tool for determining full‐field Lagrangian deformation fields for data sets with small pixel displacements and high observational noise.

Effect of pre-strain on the flux dynamics of current-carrying superconductors containing defects

This article presents a study that combines the electrostatic potential equation with the time-dependent Ginzburg–Landau equation, incorporating volume strain and utilizing Maxwell-type and current-carrying boundary conditions. Through the finite difference method, the research investigates the magnetic flux dynamics and energy variations in a type II superconductor with an artificial defect at the center, considering pre-strain, external magnetic field, and external current. The findings indicate that linear deformation and external electric field have a significant impact on the electrical properties, distribution of magnetic flux vortices, vortex dynamics, order parameter value, and overall total energy in superconductors with defects. These results contribute to a better understanding of the magnetic flux dynamics in superconductors under complex conditions.

Automated Volumetric Milling Area Planning for Acoustic Neuroma Surgery via Evolutionary Multi-Objective Optimization.

Mastoidectomy is critical in acoustic neuroma surgery, where precise planning of the bone milling area is essential for surgical navigation. The complexity of representing the irregular volumetric area and the presence of high-risk structures (e.g., blood vessels and nerves) complicate this task. In order to determine the bone area to mill using preoperative CT images automatically, we propose an automated planning method using evolutionary multi-objective optimization for safer and more efficient milling plans. High-resolution segmentation of the adjacent risk structures is performed on preoperative CT images with a template-based approach. The maximum milling area is defined based on constraints from the risk structures and tool dimensions. Deformation fields are used to simplify the volumetric area into limited continuous parameters suitable for optimization. Finally, a multi-objective optimization algorithm is used to achieve a Pareto-optimal design. Compared with manual planning on six volumes, our method reduced the potential damage to the scala vestibuli by 29.8%, improved the milling boundary smoothness by 78.3%, and increased target accessibility by 26.4%. Assessment by surgeons confirmed the clinical feasibility of the generated plans. In summary, this study presents a parameterization approach to irregular volumetric regions, enabling automated milling area planning through optimization techniques that ensure safety and feasibility. This method is also adaptable to various volumetric planning scenarios.

Energy Dissipation during Crack Growth in Rubbers with Mullins Softening

The modulus and toughness of rubbers can be improved by incorporating fillers into the rubber matrix. Filled rubbers exhibit a strain‐induced softening phenomenon known as the Mullins effect. Upon deformation, filled rubbers can dissipate strain energy, which results in enhanced resistance to crack growth. An in‐depth understanding of the energy dissipation accompanying crack growth is important for the predictive modeling of rubber fracture. Herein, an experimental study on the fracture toughness of filled and unfilled rubbers with a focus on characterizing the energy dissipation caused by the Mullins effect during crack growth is presented. A particle tracking method is used to measure the nonlinear deformation fields in notched rubber specimens when subjected to monotonic tensile loading. Using the measured deformation fields and an independently calibrated constitutive model, the evolution of stress fields during crack growth is quantitatively evaluated, based on which the energy dissipation and intrinsic toughness are determined with the assumption of steady‐state crack growth. It is found that the filled rubber exhibits more energy dissipation during crack growth than the unfilled rubber. More importantly, the intrinsic toughness of the filled rubber (5000–8000 J m−2) is also much higher than that of the unfilled rubber (150–300 J m−2).

Study of the boundary migration of recrystallized grains under inhomogeneous deformation field by crystal plasticity – phase field simulation

ABSTRACT In this study, a grain boundary (GB) migration model based on crystal plasticity (CP) and phase field (PF) was constructed for recrystallization of magnesium alloys. The model introduced the stored energy field obtained by CP into the PF simulations, aiming to analyze the effect of the inhomogeneous stored energy generated under the plastic deformation on the GB migration. It was found that the curvature plays a more significant role in the inhomogeneous stored energy field than in the uniform deformation field. Although grains with hard orientation have a lower deformation storage energy, they are still partially swallowed due to mutual influence between GBs near the triple junction. The high energies in the original GBs increase the migration rate at the triple junctions locally for a short period of time, but it is not enough to make a significant difference over extended periods at mesoscopic scales. The simulation results in this study are helpful in explaining the previous experimental observations.

Efficient and robust deformation measurement based on unsupervised learning

Digital image correlation (DIC) as a non-contact deformation measurement technique is widely used in various engineering fields. Recently, satisfactory results have been achieved by deep learning-based DIC methods, which rely on synthetic datasets for supervised training due to the difficulty in obtaining the ground truth of deformation fields. However, generalization to real scenes remains challenging due to the inherent differences between synthetic and real images and the limited variability of synthetic datasets. To solve this problem, this paper proposes an unsupervised learning DIC method, referred as UnDIC-Net. UnDIC-Net proposes a Patch-based Zero-Normalized Sum of Squared Differences (Patch-ZNSSD) similarity measure as the loss function for unsupervised training, thereby eliminating the dependency on hard-to-obtain labeled data. Meanwhile, we also collected speckle image from real scenes and built an unlabeled dataset to train UnDIC-Net. For network structure, UnDIC-Net adopts an incremental deformation estimation strategy to compute the deformation field, and interestingly, this network can be applied to large deformation measurements. Adequate experiments show that UnDIC-Net performs well in small deformation measurements, and for larger deformation measurements (>100 pixels), some traditional methods fail while UnDIC-Net still performs well. The code and data of this paper is released at: https://github.com/LianpoWang/UnDICnet-master.

СОВРЕМЕННЫЕ ВЕРТИКАЛЬНЫЕ ДВИЖЕНИЯ ЗЕМНОЙ ПОВЕРХНОСТИ ЮГА О. САХАЛИН ПО ДАННЫМ GNSS НАБЛЮДЕНИЙ

In the regional structural-neotectonic aspect, the south of Sakhalin Island consists of three submeridional uplifts and two troughs separating them. The geodynamic GNSS (Global Navigation Satellite System) network installed in the south of the island made it possible to estimate secular vertical movements of the earth's surface based on interseismic velocities in the International Terrestrial Reference Frame. The interseismic vertical movements of neotectonic structures were determined from the data of 29 GNSS observation points where 3 to 6 periodic measurement cycles were completed from 1999 to 2012. A characteristic feature of interseismic movements of the earth's surface is the uplift of the entire Yuzhno-Sakhalinsk neotectonic region at an average rate of 1.1 mm/yr, which is in the agreement with the geological and geomorphological studies of the neotectonic evolution of Sakhalin. The highest velocities (1.0–1.6 mm /yr) are confined to uplifts, relatively lower velocities (0.6–0.7 mm/yr) occur in troughs. The revealed inhomogeneities of vertical velocities in the troughs are reflected in the regional field of horizontal deformations and kinematics of faults bounding the troughs. The obtained estimates of the secular neotectonic rates do not agree with the Map of recent vertical movements of the earth's crust of the Sakhalin Island (hereinafter referred to as the RVMEC Map) compiled in the late 1970s. Its geodetic justification was based on the lines of repeated high-precision leveling and the data of sea level observation posts. According to the RVMEC Map, the Yuzhno-Sakhalinsk neotectonic region, as a whole, was characterized by the subsidence of the earth's surface at rates up to 7–8 mm/yr both within the neotectonic uplifts and the troughs and were interpreted as secular tectonic movements. Strong seismic events that occurred during the period of repeated leveling (1959–1977) distorted the RVMEC Map as a map of secular tectonic movements in southern Sakhalin.

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

Phase field modeling of anisotropic silicon crystalline cracking in 3D thin-walled photovoltaic laminates

A novel computational framework integrating the phase field approach with the solid shell formulation at finite deformation is proposed to model the anisotropic fracture of silicon solar cells in the thin-walled photovoltaic laminates. To alleviate the locking effects, both the enhanced assumed strain and assumed natural strain methods are incorporated in the solid shell element formulation. Aiming at tackling the poor convergence performance of standard Newton schemes, the efficient and robust quasi-Newton scheme is adopted for the solution of phase field modeling with enhanced shell formulation in a monolithic manner. Due to fracture anisotropy of the brittle silicon solar cells, the second-order structural tensor that is defined by the normal of preferential crack plane is introduced into the crack energy density function in the phase field modeling. On the other hand, to efficiently predict the crack growth of silicon solar cells, a global–local approach in the 3D setting proposed in the previous work is adopted here for the fracture modeling. In this approach, both mechanical deformation and phase field fracture are accounted for at the local model, while only mechanical deformation is addressed at the global level. At each time step, the solution of the global model is used to drive the local model, which corresponds to the one-way coupling in line with experimental evidence that the silicon cell cracking has negligible influence on the stiffness of photovoltaic modules. The capability of the modeling framework is demonstrated through numerical simulation of silicon solar cell cracking in the photovoltaic modules when subjected to different loading cases.

A research framework for seismic slip distribution inversion considering atmospheric effects and deformation field downsampling

ABSTRACT Traditional Interferometric Synthetic Aperture Radar (InSAR) methods have difficulties in capturing deformation information of small and medium-sized earthquakes due to small surface deformation and atmospheric interference. This study proposes a research framework for seismic slip distribution inversion considering atmospheric effects and deformation field downsampling. The research framework begins by generating multiple interferometric pairs, using the coherence thresholding method to select stable points as reference during phase unwrapping. This step includes averaging the unwrapped pairs post-phase superposition to mitigate atmospheric turbulence effects in the interferograms and effectively extract the faint coseismic deformation field. Additionally, the framework employs a saliency-based quadtree downsampling algorithm to differentiate between major and minor deformation zones, thereby streamlining the data associated with the deformation field. The Bayesian method is then used to determine the geometric parameters of the earthquake fault, with the steepest descent method (SDM) applied to invert the fault slip distribution. The methodology was tested using the March 20, 2020, Ms5.9 earthquake in Dingri County, Tibet, China as a case study. Results demonstrate that this approach reduces atmospheric influences in the deformation field and enhances the accuracy of fault slip inversion, showing high consistency with existing studies and validating the reliability of the proposed method.

Cracking performance characterisation of aramid fiber-reinforced asphalt mixtures using digital image correlation

ABSTRACT Conventional index-based testing of asphalt mixtures cannot accurately capture local deformation in a sample, limiting the usage of standard test measurements. The non-contact-based measurements proved effective to capture local deformation fields. This study aimed to capture the fatigue and thermal cracking behaviour of fiber-reinforced asphalt mixture (FRAM) by utilising digital image correlation (DIC). One binder (PG76-22), a diabase aggregate and three fibers (polyolefin/ aramid fibers (PFA) at 0.05% dosage and Sasobit-coated aramid fibers at 0.01% and 0.02% dosage) were used to prepare a total of four mixtures (one control and three FRAM). All these mixtures were produced at a local batch plant following manufacturer-recommended mixing methods. DIC analysis was performed for three-point bending beam (3PB) and disk shape compact tension (DCT) tests at intermediate temperature (25°C) and low temperatures of −12°C and −18°C. Based on index values from DCT and 3PB, the thermal and fatigue cracking performance enhancement was not significant. However, DIC analysis showed that, regardless of testing temperature, the crack propagated in a random pattern for FRAM, whereas the crack followed a relatively straight path for the control mix. Finally, based on DIC strain contours, FRAM mixtures exhibit distributed strain over a larger area compared to the control mix.

Локальное изменение напряженного состояния в образцах горных пород перед разрушением по данным коэффициента Лоде–Надаи

In this paper, the relationship of the Lode–Nadai coefficient, which determines the shape of the stress ellipsoid, with the nature of brittle fracture in sandstone, pyrophyllite and dolomite samples for a rigid loading machine is investigated. The measurement of the inhomogeneous deformation field in the samples and the observation of the internal fracture process were performed using strain gauges and acoustic sensors. It is shown that the formation of the main crack is preceded by the evolution of local deformations in the sample, recorded by the strain gauge method. Special processing of strain gauge data, taking into account the free lateral surface of the samples, made it possible to calculate the principle deformations and three invariants of the strain tensor: maximum shear deformation, volume change deformation and the Lode–Nadai coefficient. It has been established that at the final stage of deformation, when a main crack is formed in local sections of the sample, the axes of the principal deformations are reindexed, which is expressed in the achievement of the maximum values of +1 and -1 by the Lode–Nadai coefficient. A comparison with field observations was made.