Deformation Method Research Articles

An efficient solid shell material point method for large deformation of thin structures

AbstractThe standard material point method (MPM) encounters severe numerical difficulties in simulating shell structures. In order to overcome the shortcomings of locking effects, the discretization size of background grid should be small enough, usually smaller than 1/5 of the shell thickness, which however will lead to prohibitive computational cost. A novel solid shell material point method (SSMPM) is proposed to efficiently model the large deformation of thin structures. The SSMPM describes the material domain of shell structures by shell particles with hexahedral particle domains. The locking treatments of solid shell element are then introduced in SSMPM, which results in the correction of strain field throughout the shell thickness. Namely, the assumed natural strain (ANS) method is adopted to eliminate the shear locking and trapezoidal locking, while the enhanced assumed strain (EAS) method is employed to eliminate the thickness locking. With the precise description of bending modes, a single layer of particles and a coarse background grid could be used in shell structure simulations with the SSMPM, which dramatically increases the computational efficiency. A local multi‐mesh contact method is presented to naturally couple SSMPM and MPM for the contact situations of shells with other objects. Several numerical examples, including beam vibration, pinched cylinder with free edges and full hemispherical shell, are performed to verify and validate the SSMPM, which shows that the SSMPM considerably outperforms the standard MPM in these situations. A fluid–structure interaction problem and the penetration of a thin plate are investigated based on the contact method and the results are in good agreement with those in the literature.

Analytical method for deformation and stress calculation of bell-and-spigot joints in PVC-U pipes

The stable operation of water supply pipelines relies significantly on the structural safety of pipe joints. A novel analytical pipe joint structural calculation method based on the Novozhilov thin shell theory was proposed to calculate the deformation and stress of bell-and-spigot joints in unplasticized polyvinyl chloride (PVC-U) pipes under internal pressure. An equivalent stress index was established to investigate and evaluate the safety performance of pipe joints. The effects of various factors, including spigot insertion depth, the clearance between the bell and spigot, internal pressure, and different pipe nominal outside diameter (DN) and nominal pressure (PN) series, on the maximum equivalent stress of pipe joints, were thoroughly analyzed. The results indicate that the maximum equivalent stress under nominal pressure is located on the inner surface of the bell and consistently exceeds the design stress. The influence of spigot insertion depth on the maximum equivalent stress is minimal. However, as the clearance value between the bell and spigot decreases and the internal pressure increases, the maximum equivalent stress increases significantly. Pipes with smaller DN and PN series result in a higher maximum equivalent stress at the joint. The analytical method indicates that increasing pipe thickness and reinforcing the bell with continuous carbon fiber filament winding are two potentially effective methods to enhance the mechanical performance of the joint and reduce the maximum equivalent stress. This study's findings offer valuable theoretical support for designing and selecting joints in PVC-U pipelines.

Anisotropic effect of pre-strain on hydrogen embrittlement susceptibility in a stable austenitic stainless steel

Different pre-strain of uniaxial tensile deformation or cold rolling were applied to 0.02C–18Cr–11Ni-0.15 N austenitic stainless steel to investigate the effect of pre-strain stress modes on hydrogen embrittlement (HE). The susceptibility to HE was negligibly affected by tensile pre-strain, but it increased with the degree of pre-strain by cold rolling. This resulted from differences in strain distribution, twinning behavior, and changes in H diffusivity arising from the two deformation methods. Homogeneous strain distribution was observed after uniaxial tensile deformation, whereas the deformation was locally concentrated after cold rolling. This led to localized H adsorption to assist crack propagation. While twinning was the main deformation mechanism in the present steel, only the twins formed during cold rolling were vulnerable to stress localization owing to their crystallographic orientation. These twins acted as initiation sites for H-induced cracking and degraded the HE resistance. Finally, H diffusion was less active in tensile-strained samples, and high HE resistance was effectively maintained despite the increase of strength by pre-straining as a consequence.

An elastoplastic damage model for concrete considering the influence of mesostructure on transverse deformation

The deformation of mesostructures such as micropore collapse or microcrack expansion within concrete can hugely influence its macro transverse deformation. This deformation characteristic is not effectively characterized in existing elastoplastic damage constitutive models based on micromechanics. This discrepancy can result in substantial disparities between the calculated results and the actual situation when carrying out the stress and deformation analysis of concrete structures. Through an in-depth examination of how micropore collapse and microcrack shear expansion affect transverse measurable strain, a new calculating method for concrete transverse deformation is established according to its actual evolution characteristics. The reliability of the proposed method is verified based on the triaxial compression test results. Research results indicate that the transverse deformation of concrete increases slightly before the peak deviatoric stress, and significantly in the post-peak stage. If deformation is restricted, changes in transverse deformation can profoundly affect the stress state of concrete. Micropore collapse reduces the macroscopic transverse deformation of concrete, while microcrack expansion has the opposite effect. The strain caused by micropore collapse and microcrack expansion can be deemed as derivative strain of plastic strain, and an influence coefficient can be used to characterize the impact of these two factors on macroscopic transverse deformation. It is proposed that the total transverse strain consists of elastic strain and the product of plastic strain and plastic strain influence coefficients. The development characteristics of concrete transverse deformation can be effectively captured when describing the plastic strain influence coefficient using an arctangent function.

Calculation Method for Traffic Load-Induced Permanent Deformation in Soils under Flexible Pavements

Rutting is one of the most common types of distress in flexible pavement structures. There are two fundamental methods of designing pavement structures: conventional empirical methods and analytical approaches. Many analytical and empirical design procedures assume that rutting is mostly of asphalt origin and can be reduced by limiting the vertical deformation or stress at the top of the subgrade, but they do not quantify the rutting depth itself. Mechanistic–empirical models to predict the permanent deformations of unbound pavement layers have been well investigated and are rather common in North America; however, they are not widely utilized in the rest of the world. To date, there is no generally accepted, widely recognized, and documented procedure for calculating permanent deformations and thus for determining the rutting depth in flexible pavement courses originating from the unbound granular layers. This paper presents a layered calculation method with which the deformation of soil layers (base, subbase, and subgrade courses) under flexible pavements due to repeated traffic load can be determined. In the first step, the cyclic strain amplitude is calculated using a nonlinear material model that is based on particle size distribution parameters (d50 and CU) and dependent on the mean normal stress, relative density, and actual strain level. In the second step, the HCA (High Cycle Accumulation) model is used to calculate the residual settlement of each sublayer as a function of the number of cycles. It is shown that the developed model is suitable for describing different types of subgrades and pavement cross-sections. It is also demonstrated with finite element calculations that the developed model describes both the elastic and plastic strains sufficiently accurately. The developed model can predict the settlement and rutting of pavement structures with sufficient accuracy based on easily available particle size distribution parameters without the need for complex laboratory and finite element tests.

MacJNet: weakly-supervised multimodal image deformable registration using joint learning framework and multi-sampling cascaded MIND

Deformable multimodal image registration plays a key role in medical image analysis. It remains a challenge to find accurate dense correspondences between multimodal images due to the significant intensity distortion and the large deformation. macJNet is proposed to align the multimodal medical images, which is a weakly-supervised multimodal image deformable registration method using a joint learning framework and multi-sampling cascaded modality independent neighborhood descriptor (macMIND). The joint learning framework consists of a multimodal image registration network and two segmentation networks. The proposed macMIND is a modality-independent image structure descriptor to provide dense correspondence for registration, which incorporates multi-orientation and multi-scale sampling patterns to build self-similarity context. It greatly enhances the representation ability of cross-modal features in the registration network. The semi-supervised segmentation networks generate anatomical labels to provide semantics correspondence for registration, and the registration network helps to improve the performance of multimodal image segmentation by providing the consistency of anatomical labels. 3D CT-MR liver image dataset with 118 samples is built for evaluation, and comprehensive experiments have been conducted to demonstrate that macJNet achieves superior performance over state-of-the-art multi-modality medical image registration methods.

Landslide risk evaluation method of open-pit mine based on numerical simulation of large deformation of landslide

It is of great practical significance to carry out quantitative risk assessment of landslide disaster to protect people’s lives and property safety and maintain the sustainable development of social economy. The delineation of landslide disaster range is the key link of landslide risk evaluation in open-pit mine. This study took the open-pit coal mine coal mine in Block I of Thar coal field in Pakistan as the research background, and constructed a framework for landslide risk evaluation in open-pit mines. Based on the numerical simulation method of large deformation of landslide, the disaster range of landslide in open-pit mine was delineated. The stability of stope slope was analyzed based on rigid body limit equilibrium method. The probability of landslide instability was calculated based on Monte Carlo method. And the comprehensive fuzzy evaluation model was established to calculate the total risk value of landslide. The results showed that: through numerical simulation and empirical formula calculation, the landslide disaster range was accurately delineated, and the comprehensive vulnerability of the disaster bearing body was determined to be medium vulnerability; the annual probability of landslide instability under natural conditions was 0.003, which belongs to moderate risk. The annual probability of landslide instability under rainstorm conditions was 0.024, which was highly dangerous; the annual probability of landslide instability under seismic conditions was 0.018, which was highly dangerous. Under natural conditions, the total risk value of landslide was 114,686.4 rmb, and the annual mortality rate of population was 0.0255 people/year. The total risk value of landslide under rainstorm condition was 11,707,570 rmb, and the annual mortality rate of population was 0.18375 people/year. The total risk value of landslide under earthquake condition was 43,007,400 rmb, and the annual mortality rate of population was 0.135 person/year, which was an unacceptable risk. The economic loss was a small geological disaster risk under natural conditions, and it was a medium-sized geological disaster risk under both rainstorm and earthquake conditions. Therefore, landslide prevention and control and management measures such as slope deformation monitoring were proposed to ensure the safety of personnel and property in open-pit mines.

A meshfree large-deformation analysis method for geotechnical engineering based on the RBF field variable mapping technology

In this paper, a practical meshfree large deformation method (MFLDM) is proposed for numerical analysis in geotechnical engineerings, including: soil foundation, slop, dam, etc. The MFLDM leverages both the flexible nodal distribution in the meshfree method and the high stability in the arbitrary Lagrangian–Eulerian (ALE) framework. In each calculation step, two sets of Gauss points, fixed and moving Gauss points, are generated in the background mesh. In addition, the radial basis function (RBF) is used to map field variables, including stress, stain, and constitutive variables, between the fixed and moving Gauss points to achieve the field variable redistribution during the large-deformation analysis. The proposed MFLDM, which is written in C++ using the object-oriented programming approach, can be completely integrated into the self-development calculating system named GEODYNA and coupled with the finite element method (FEM) at the matrix level, which significantly broadens its practical application. The proposed model is verified by several numerical examples and compared with different constitutive models, including the linear elasticity model, ideal elastic–plastic model, and generalized elastic–plastic model. The comparison results verify the high accuracy, fast convergence, and good robustness of the proposed MFLDM. Finally, the proposed MFLDM is applied to a local large deformation analysis between the cut-off wall and the core wall on a deep overburden.

Numerical optimisation of the active lift turbines using OpenFoam's overset method

This work presents a preliminary study of the numerical optimization of "active lift turbine" using computational fluid dynamics (CFD). This active lift turbine is designed to improve efficiency of vertical axis energy recovery turbines (wind and tidal turbines). It uses a crank rod system to convert normal forces into momentum in order to improve the yield.
 After a validation work of CFD model in two dimensions, the numerical optimization of the tidal turbine system is carried out. In fact, due to the specific characteristics of the active lift turbine, the blades do not follow a circular trajectory (Fig. \ref{fig:combined}). The OpenFoam overset module is therefore chosen because it allows to control the motion of the blades easily \cite{Chalmers}. The Overset method allows a good performance evaluation and limits the risk of numerical divergence that could be caused by mesh deformation methods; Moreover it limits the computation time compared to remeshing methods. However, it is more expensive than a more traditional Arbitrary Mesh Interface method \cite{Openfoam}, which is not suitable for the active lift turbine simulations.
 The impact of several parameters on the performances is studied. The simulations are performed for a range of operating conditions including different inflow velocities, angles of attack and active flow turbine settings (like the amplitude of the radius variation, see Fig \ref{fig:combined}). The results are evaluated in terms of the turbine power output and efficiency.
 The results show the importance of numerical simulation for the development of new types of energy recovery systems. It allows a better understanding of the interactions between the turbine and the fluid, and of the operation of such systems.
 Further studies are required for the active lift turbine: conventional attempts at optimisation are not perfectly suited to this system. Improving the lift/drag ratio makes less sense when the normal forces should also be taken into account to improves the performances. Furthermore, other aspects of operation should be analysed: variation of the turbulence rate, implementation of boundary layer re-attachment systems...

A review of armour's use of composite materials

Composites with a laminated structure come from stacking ceramic and metal in a particular order. Because of their high strength and hardness, low density of ceramics, and extraordinary flexibility, metals can be used as bulletproof armour. The bullet anti-penetration system includes a ceramic screen that slows down the projectile and splits it up and a metal backplate that plastically deforms to absorb the projectile's kinetic energy. Laminates have several downsides, including weak interface bonding, a tendency for tip cracks due to increased internal stress, and a jarring difference between the metal and ceramic properties. Crack migration and propagation can cause abrupt changes in material characteristics at the ceramic–metal contact. A drop between the ceramic panel and metal backplate can be easily triggered when a ceramic panel is impacted, as cracks form in the interlayer. In this area, the interface bonding strength is still inadequate. In this review, we looked at the meshless smoothed-particle hydrodynamic method for high-velocity impact and massive deformation, the finite-element simulations of interface impact resistance and the first-principles predictions of interface strength. The paper concludes with numerous suggestions for future improvement: Further study is required on ceramic toughening to increase the compatibility of ceramic panels and metal backplates, the performance transition between ceramic and metal, and the reliability of ceramic–metal laminated materials. It is critical to study ways to strengthen metals. More multiscale research using methods like the phase-field method, finite element analysis, and first-principles computations, focusing on how to mix these techniques naturally and successfully, is needed to reinforce metals by introducing nano-phases into metal matrix composites while still retaining the metal's ductility. The latest study that emphasises the potential advantages of hybrid materials, specifically the combination of aramid and kenaf fibres, highlights a notable progression in the domain of armour technology.

Characteristics of changes in microstructure and mechanical characteristics under high energy load

Purpose. Verification of the hypothesis about the possibility of obtaining a fine-grained structure of a metal as a result of processing with high-density energies. The methods. The research was carried out on cylindrical samples with a diameter of 50 mm and a length of 300 mm, which were made of structural steel 45 in a normalized state. The thickness of the inner coaxial layer BP1 with a detonation speed D=7.5 km/s was 3 mm, the thickness of the outer layer BP2 with a detonation speed D=3.5 km/s was 40 mm. The two-layer BP charge used in the experiment increases the duration of the shock wave and at the same time protects the samples from destruction. Findings. The mechanism of nanostructuring, in general terms, consists in the accumulation of the degree of deformation without destruction, which leads to the defragmentation of the structure with a significant increase in the density of dislocations. One of the methods that allows you to achieve a high density of dislocations, comparable to IPD, is treatment with shock waves. The change in the grain structure in the places of the pores indicates extremely high degrees of inhomogeneous deformation in these areas. During the passage of the shock wave in the middle of the sample, at the boundaries of the interface of phases with different densities, diffraction wave effects occur, which lead to the occurrence of shear deformations. It can be assumed that in the area of pores and microcracks, the deformation conditions are similar to those realized by some methods of intensive plastic deformation. This leads to a sharp grinding of the grain structure and a corresponding change in mechanical properties. The originality. The paper found that the processing of steel parts with the help of high-density energy leads to a sharp grinding of the grain to the nanostructure size and, as a result, to an increase in mechanical properties. The revealed regularities make it possible to obtain optimal parameters of high-energy processing, which lead to an increase in hardness, a redistribution of internal stresses and a decrease in surface roughness. Practical implementation. Obtaining grains with nanostructural characteristics in the structure of the material will allow to create fundamentally new devices and materials. Such materials will have properties significantly exceeding their achieved level – which is important for many fields of engineering, medicine, biotechnology, environmental protection, defense, etc.

Cyclic contraction-expansion extrusion (CCEE): An innovate severe plastic deformation method for tailoring the microstructure and mechanical properties of magnesium AZ91 alloy

In this study, the Cyclic Contraction-Expansion Extrusion (CCEE) process, a novel severe plastic deformation (SPD) technique, is applied to the AZ91 magnesium alloy to enhance its mechanical properties through microstructural refinement. The CCEE method combines cyclic expansion extrusion (CEE) and cyclic extrusion compression (CEC), integrating their advantages while overcoming drawbacks. The CCEE process is capable of inducing substantial plastic strain (3.38) within a single processing cycle, eliminating the need for secondary punches or a synchronized backpressure system. The process is conducted at a temperature of 300 °C, resulting in a bimodal microstructure through the dynamic recrystallization (DRX) mechanism. This microstructure consists of refined equiaxed α-Mg grains with an average size of 2.8 μm, surrounded by a network of newly nucleated α-Mg grains and Mg17Al12 particles with an average size of 500 nm in the two-pass processed sample. Results obtained from the tensile test technique indicate a significant enhancement in the ultimate tensile strength (UTS) of the AZ91 alloy, increasing from 139 MPa to 276 MPa and 290 MPa, and a notable improvement in elongation, increasing from 4% to 8% and 12% after two passes of the CCEE process. Macro-texture X-Ray diffraction (XRD) measurements reveal the formation of a pyramidal deformation texture in the one-pass sample, contributing to the UTS improvement. This texture weakens during the second pass, leading to an increase in elongation. Furthermore, microhardness measurements show an increase from HV 62 to HV 85 after the first pass of the CCEE and HV 73 after the second pass.

Study on the Analysis of Pile Foundation Deformation and Control Methods during the Excavation of Deep and Thick Sludge Pits

This study aims to apply performance-based safety-assessment methods to the monitoring and numerical simulation of excavation engineering projects in order to comprehensively enhance engineering risk management and decision support. In this paper, a deep excavation project in Hefei with thick silty clay layers was studied. The analysis included the surface settlement, the deformation of support structures, the vertical and horizontal displacements of pile tops, axial forces in steel braces, settlement, and the horizontal displacement of a gravity retaining wall on the south side of the excavation using field-monitoring data. A refined three-dimensional finite element model was established to further analyze the distribution of uplift displacement at the bottom of the excavation, horizontal displacement, and bending moments of piles based on simulation results. The research findings indicate that phased excavation can reduce the spatial extent of disturbance to the surrounding soil caused by excavation. Additionally, the closer the location to the excavation and the thicker the underlying silty clay layer, the faster the rate of settlement change and the greater the surface settlement. The spatial structure formed by steel braces and pile foundations effectively reduced the horizontal displacement of the engineering piles. The study’s use of field monitoring and finite element simulation provided valuable insights into the deformation of support structures and the response of the surrounding soil to excavation, confirming the rationality and applicability of the support structure in this paper. The proposed method can serve as a reference for similar complex stratum excavation design and construction. The performance-based safety assessment is introduced, and the monitoring data, numerical simulation results, and performance targets are comprehensively analyzed to provide a reliable scientific basis for engineering decision making.

Current situation and development trend of design methods for subgrade structure of high speed railways

PurposeThis method will become a new development trend in subgrade structure design for high speed railways.Design/methodology/approachThis paper summarizes the structural types and design methods of subgrade bed for high speed railways in China, Japan, France, Germany, the United States and other countries based on the study and analysis of existing literature and combined with the research results and practices of high speed railway subgrade engineering at home and abroad.FindingsIt is found that in foreign countries, the layered reinforced structure is generally adopted for the subgrade bed of high speed railways, and the unified double-layer or multi-layer structure is adopted for the surface layer of subgrade bed, while the simple structure is adopted in China; in foreign countries, different inspection parameters are adopted to evaluate the compaction state of fillers according to their respective understanding and practice, while in China, compaction coefficient, subsoil coefficient and dynamic deformation modulus are adopted for such evaluation; in foreign countries, the subgrade top deformation control method, the subgrade bottom deformation control method, the subsurface fill strength control method are mainly adopted in subgrade bed structure design of high speed railways, while in China, dynamic deformation control of subgrade surface and dynamic strain control of subgrade bed bottom layer is adopted in the design. However, the cumulative deformation of subgrade caused by train cyclic vibration load is not considered in the existing design methods.Originality/valueThis paper introduces a new subgrade structure design method based on whole-process dynamics analysis that meets subgrade functional requirements and is established on the basis of the existing research at home and abroad on prediction methods for cumulative deformation of subgrade soil.

A novel prediction model construction and result interpretation method for slope deformation of deep excavated expansive soil canals

Several giant water diversion projects go through large expansive soil areas in China. It is challenging to ensure the slope stability of the deep excavated expansive soil canal segments due to its undesirable geologic, and physical and mechanical properties. This study develops a novel deformation prediction method for deep excavated expansive soil canal slopes based on the eXtreme Gradient Boosting (XGBoost) algorithm, and provides a result interpretation using SHAP (SHapley Additive exPlanations). Firstly, the main factors influencing the slope deformation of deep excavated expansive soil canal segments are discussed. Subsequently, the integrated XGBoost-SHAP method is proposed for the prediction model construction of slope deformation and its result interpretation, the related the methodologies including the variational mode decomposition (VMD), XGBoost, and SHAP are also presented. The ten-fold cross-validation is employed to find the hyperparameter combination for the deformation prediction models, and the model performances are compared with common validation measurements. The effectiveness of the explanatory deformation prediction method is verified through one typical deep excavated expansive canal segment of the mid-route of the South-to-North Water Diversion Project in China. The case study shows that the VMD algorithm can well decompose the trend, periodic and fluctuating displacements. Compared with random forest and least squares-support vector machines, the XGBoost-algorithm based model achieves the better prediction performance. SHAP provides prediction result interpretations at both global and local levels. Time dependent effect and groundwater have a significant impact on the slope deformation of deep excavated expansive soil canal segments. The integrated SHAP-XGBoost method can provide a reference for predicting slope deformation of the similar projects. It can also quantify the contribution and mechanism of influencing factors on slope deformation at both global and local levels, which is conducive to implement reinforcement measures.

Numerical simulation study of the fluid-structure coupling effects of Kármán vortex street on airfoil motion with varying thickness

This paper examines the fluid-structure interaction of rigid and passive motion of airfoils with different thicknesses in the Kármán vortex street at low Reynolds numbers through numerical simulations. Five NACA airfoils with varying thicknesses (8%, 12%, 16%, 20%, and 24%) were investigated regarding their fluid-structure interaction in the Kármán vortex street. These airfoils were positioned downstream along the centerline of a D-shaped cylinder. Employing a six-degree-of-freedom method, their passive motion was simulated, and the motion grid was generated using the elastic deformation method and local grid reconstruction technique. The analysis included examing alterations in the flow field and forces acting upon airfoils of varying thicknesses in both fixed and released states. The outcomes demonstrate that an increase in airfoil thickness amplified the traction force exerted on the airfoil within the Kármán vortex street, consequently yielding higher lateral force and torque. In the released state, the airfoil exhibited forward motion towards the D-shaped cylinder and deviated from the suction region of the Kármán vortex street due to the influence of lateral force. The study unveils that airfoils of suitable with appropriate thickness, such as NACA0012, achieved an improved equilibrium between forward speed and lateral displacement, thereby covering a more extensive forward distance. These findings provide valuable insights for the designing robotic fish that utilize vortex streets under low-flow conditions.

Краниологическое исследование черепов из двух гуннских погребений из Крыма (Усть-Альминский некрополь, IV–V вв. н. э.)

Introduction. The invasion of the Huns in Europe, which became the cause of the Great Migration of peoples, could not but leave a significant archaeological trace. However, only a small number of Hun burials are currently known, most of which were discovered accidentally in the middle of the 20th century, which makes each newly discovered burial unique, and their comprehensive study and publication of individual data is important for subsequent research. Materials and methods. During the excavations in 2021–2022, two Hun burials were discovered in the Ust-Alma necropolis. One of them belonged to a young man, the second to an elderly woman. The good preservation of both skeletons, in particular their skulls, allowed for a complete craniological examination. In addition, a children's Hun skull from the Belyaus settlement was examined, which is in permanent storage at the D. N. Anuchin Research Institute and Museum of Anthropology. Results. As a result of the work carried out, it was found that both individuals from Ust-Alma have the same type of skull deformation – high annular (according to the classification of E.V. Zhirov). However, the deformation methods were probably different. The deformation of the skull of a child from Belyaus is defined as occipital with right-sided asymmetry of the occiput. Craniophenetic data do not indicate the relationship of individuals buried in the Ust-Alminsky burial ground. Craniometric data indicate a mixed origin of the crimean Huns. Conclusion. Due to the small number of Hun burials from Ust-Alma, as well as individual data on Hun skulls in the scientific literature, it is difficult to conduct a statistical analysis based on craniological data. Within the typological approach, for a number of features, the male skull was characterized as Caucasoid, and the female as Mongoloid. Thus, new craniological data on rare Hunnic skulls introduced into scientific circulation will increase the comparative base for further research. @ 2023. This work is licensed under a CC BY 4.0 license

Nonlinear cloth simulation with isogeometric analysis

AbstractPhysically based cloth simulation with nonlinear behaviors is studied in this article by employing isogeometric analysis (IGA) for the surface deformation in 3D space. State‐of‐the‐art simulation techniques, which primarily rely on the triangular mesh to calculate physical points on the cloth directly, require a large number of degrees of freedom. An effective method for the cloth deformation that employs high‐order continuous B‐spline surfaces dependent on control points is proposed. This method leads to the merit of fewer degrees of freedom and superior smoothness. The deformation gradient on the high‐order IGA element is then represented by the gradient of the B‐spline function. An iterative method for solving the nonlinear optimization transferred from the implicit integration and a direct implicit–explicit method are derived on the basis of elastic force calculation to improve efficiency. The knots of the representation are effectively utilized in collision detection and response to reduce the computational burden. Experiments of nonlinear cloth simulation demonstrate the superiority of the proposed method considering performance and efficiency, achieving accurate, efficient, and stable deformation.

Fabrication of ultrafine-grained Cu-Mn alloy with uniform microstructure and high mechanical properties

Homogenization, random orientation, and high strength are the research goals of target materials. In this study, the bulk ultrafine-grained (UFG) Cu-5Mn alloy target materials were prepared by two typical severe plastic deformation methods, equal channel angular pressing (ECAP) and auxiliary-cooling multi-pass friction stir processing (MPFSP), and their structure-property relationships were comparatively investigated. Compared to the ECAP sample with extremely heterogeneous microstructure, the MPFSP sample exhibited finer and more uniform equiaxed microstructure with weaker texture and higher tensile strength of 614 MPa, which was consistent with the requirements of an ideal target material. This study provides a new perspective on the optimization of target materials.

An optimized optical-flow-based method for quantitative tracking of ultrasound-guided right diaphragm deformation

ObjectivesTo develop a quantitative analysis method for right diaphragm deformation. This method is based on optical flow and applied to diaphragm ultrasound imaging.MethodsThis study enrolls six healthy subjects and eight patients under mechanical ventilation. Dynamic images with 3–5 breathing cycles were acquired from three directions of right diaphragm by a portable ultrasound system. Filtering and density clustering algorithms are used for denoising Digital Imaging and Communications in Medicine (DICOM) data. An optical flow based method is applied to track movements of the right diaphragm. An improved drift correction algorithm is used to optimize the results. The method can automatically analyze the respiratory cycle, inter-frame/cumulative vertical and horizontal displacements, and strain of the input right diaphragm ultrasound image.ResultsThe optical-flow-based diaphragm ultrasound image motion tracking algorithm can accurately track the right diaphragm during respiratory motion. There are significant differences in horizontal and vertical displacements in each section (p-values < 0.05 for all). Significant differences are found between healthy subjects and mechanical ventilation patients for both horizontal and vertical displacements in Section III (p-values < 0.05 for both). There is no significant difference in global strain in each section between healthy subjects and mechanical ventilation patients (p-values > 0.05 for all).ConclusionsThe developed method can quantitatively evaluate the inter-frame/cumulative displacement of the diaphragm in both horizontal and vertical directions, as well as the global strain in three different imaging planes. The above indicators can be used to evaluate diaphragmatic dynamics.