Deformable Bodies Research Articles

An automated algorithm for quantitative morphometry of thoracic and lumbar vertebral bodies in lateral radiographs

Abstract This exploratory study developed and evaluated an AI-based algorithm for quantitative morphometry to assess vertebral body deformities indicative of fractures. To achieve this, 709 radiographs from 355 cases were utilized for algorithm development and performance evaluation. The proposed algorithm integrates a first-stage AI model to identify the positions of thoracic and lumber vertebral bodies in lateral radiographs and a second-stage AI model to annotate six landmarks for calculating vertebral body height ratios (C/A, C/P and A/P). The first-stage AI model achieved a sensitivity of 97.6%, a precision of 95.1%, and an average false-positive ratio of 0.43 per image for vertebral body detection. In the second stage, the algorithm’s performance was evaluated using an independent dataset of vertebrae annotated by two spine surgeons and one radiologist. The average landmark errors ranged from 2.9% to 3.3% on the X-axis and 2.9% to 4.0% on the Y-axis, with errors increasing in more severely collapsed vertebrae, particularly at central landmarks. Spearman’s correlation coefficients were 0.519–0.589 for C/A, 0.558–0.647 for C/P, and 0.735–0.770 for A/P, comparable to correlations observed among human evaluators. Bland–Altman analysis revealed systematic bias in some cases, indicating that the algorithm underestimated anterior and central height collapse in deformed vertebrae. However, the mean differences and limits of agreement between the algorithm and external evaluators were similar to those among the evaluators. Additionally, the algorithm processed each image within 10 seconds. These findings suggest that the algorithm performs comparably to human evaluators, demonstrating sufficient accuracy for clinical use. The proposed approach has the potential to enhance patient care by being widely adopted in clinical settings.

CM carbonaceous chondrite petrofabrics and their implications for understanding the relative chronologies of parent body deformation and aqueous alteration

AbstractCM chondrites have been subjected to numerous alteration processes including brecciation and ductile deformation. Here, we present the results of 2D and 3D petrofabric analysis across a suite of meteorites: Aguas Zarcas, Cold Bokkeveld, Lewis Cliff (LEW) 85311, Murchison, and Winchcombe. We find that chondrule‐defined petrofabrics are commonplace, but not ubiquitous. Where petrofabrics are present, alignment is typically observed in the chondrule long axes defining foliation fabrics. Alongside previous authors we interpolate the shock pressures to generate such fabrics between 27.8 and 41.8 GPa. Impacts capable of generating these shock pressures should ordinarily produce shock microstructures in olivine something not observed in the CMs. Whilst high calculated pre‐compaction porosities may have had a role in attenuating energy transfer during collisions, we suggest the assumption of chondrule sphericity used in these calculations is misplaced and that a non‐spherical pre‐deformation chondrule shape is likely responsible for the dichotomy. We also reveal that the relative timings of aqueous alteration, brecciation, and deformation vary between CMs. Within Aguas Zarcas, we find multiple lithic clasts interpreted as having experienced different degrees of aqueous alteration, with opposing fabrics that formed after water/rock interaction but prior to brecciation. Meanwhile, within Cold Bokkeveld, we find a consistent fabric between clasts suggesting the fabric was imposed after both aqueous alteration and brecciation.

Mechanical behavior and damage evolution of tunnel lining structure under the impact of derailment of high-speed train

In deep-buried long tunnels, train derailment accidents pose a serious threat to the stability of the tunnel lining structures and the safety of personnel along the line. To address the impact damage to the secondary lining caused by high-speed train derailments, a three-dimensional nonlinear dynamic analysis model of the Electric Multiple Unit (EMU) − lining − soil system was established. The advantages of this model include: it fully considers the complex streamlined design of the EMU front end, the nonlinearity of lining materials, and the M−C elastic structural model of the soil, allowing for accurate simulation of the contact and deformation between the EMU and the lining. The results indicate that the first 30 ms of the collision process are extremely intense, primarily involving the first three train vehicles. Among these, the head vehicle experiences the greatest reduction in kinetic energy and plastic dissipated energy, resulting in the most severe plastic deformation of the vehicle body. The impact load exhibits a distinct multi-peak characteristic, mainly composed of lateral impact force components. The area of displacement change in the lining expands continuously along the direction of the train, with peak displacements stabilizing after 30 ms. The lining primarily suffers from tensile failure, with multiple tensile cracks appearing in areas distant from the collision, while compressive damage is mainly concentrated at the point of direct impact. As the collision angle increases, the range of compressive damage along the longitudinal direction becomes narrower. The ratio of tensile damage area to compressive damage area is mainly influenced by the collision angle. In the design of tunnel structures for impact resistance, special attention should be paid to the lateral impact resistance and tensile failure capacity of the tunnel structure.

RheoVolution: An N-body simulator for tidally evolving bodies with complex rheological models

We present the open-source software RheoVolution, a computational implementation of the tidal theory based on the Association Principle, which provides a direct link from the adopted rheological model to the body’s deformation matrix in the time domain, thus facilitating the use of more complex rheological models. The code introduced here simulates the motion of N deformable bodies that remain slightly aspherical at all times. Each body can exhibit permanent triaxiality and possess its own rheology, ranging from a simple Maxwell rheology to complex rheologies equivalent to that of multilayered bodies with viscoelastic homogeneous layers. We showcase our program capabilities by reproducing different dynamical phenomena in the Solar System, namely, Earth’s Chandler wobble and true polar wander, Moon’s orbital drift, and Moon’s stabilization in the Cassini state 2.

The Effect of a Fully Asymmetric Discontinuity in the Elastic Layer of a Geometrically Nonlinear Double-Beam Coupled Mechanical System

This paper presents the effect of an antisymmetric discontinuity in a Winkler nonlinear elastic layer and compares it with the case of a double Timoshenko beam system without discontinuities. The effects of geometric nonlinearity are considered, and the obtained results represent a time-domain analysis. A modified p-version finite element method is applied to analyse the vibrations of mechanical systems with discontinuities. The main contribution of this work is a comparative analysis of a double beam system without discontinuities and a double beam system with an antisymmetric discontinuity in the Winkler elastic layer. The study demonstrates significant deviations in the beam response under a concentrated periodic external force when an antisymmetric discontinuity is present. Its qualitative and quantitative characteristics are illustrated through time histories, showing amplitude variations in the steady-state oscillation regime. Forced vibrations in the time domain are analysed using the Newmark direct integration method. The cases of deviations in the antisymmetric model are explained, highlighting their potential applications in technical practice as well as in the field of deformable bodies and structures.

Comparative Analysis of External Gear Machine Performance Considering Deformation and Thermal Effects

The energy efficiency of external gear pumps (EGPs), as in other positive displacement machines for high-pressure applications, is significantly influenced by the power losses occurring in the lubricating interfaces that seal the internal displacement chambers. Therefore, it is crucial to account for these interfaces accurately when developing predictive simulation tools. However, in literature various modeling approaches can be found that consider different assumptions regarding the analysis of these interfaces. This makes it challenging for a designer to determine which physical domains needed to be modelled accurately in order to assess the EGP performance. This paper addresses the above research question by leveraging a comprehensive simulation tool (Multics-HYGESim) developed at the authors’ research team which includes thermal-tribological considerations pertaining to the meshing of the gears, the lubricating films at the tooth tip interfaces, at the journal bearings, and at the lateral interfaces. The tool considers realistic fluid properties, including the effects of cavitation and aeration, mixed lubrication effects, as well as material deformation effects for the gears, lateral bushings and the EGP housing. Additionally, recent advancements to the model, presented for the first time in this work, include coupled thermal analysis of the EGP, including fluid domain, lubricating interface domain and solid domain. The heat transfer evaluation in the solid domain allows predicting the body temperatures along with their thermal deformation. Material deformation effects strongly affect the internal balancing features of an EGP as well as its internal pressurization. All the mutual interaction between the geometrical domain, the body motions and their deformation, the fluid dynamic and the thermal domains make a realistic quantification of these effects difficult in simulation. Using a commercial EGP as a reference, for which experimental results are available concerning volumetric and hydromechanical efficiency, this paper demonstrates how predictions can vary based on different simulation assumptions regarding body and lubricating film behavior. The paper will present simulated predictions starting from a basic rigid body assumption that considers only body motion and analytical formulations of lubricating interfaces, to simulation model cases of progressively increasing in complexity to account for deformations different bodies i.e. the gears, bushings and the housing. The most complex case would include evaluation of thermal behavior along with deformation effects. A detailed distribution of power loss and leakages arising from different sources of hydromechanical and volumetric losses is presented for all cases under consideration. The results will offer valuable insights to EGP designers, enabling them to understand the strengths and limitations of different modeling assumptions on the prediction of EGP behavior, especially regarding the effects of body deformation.

A Study of the Response Surface Methodology and Finite Element Method to Model Aircraft Engine Body Deformations During Hole Drilling.

The aviation industry is still looking for effective manufacturing methods. Currently, the challenge is still the machining of shapes in thin-walled materials. This work focuses on the analysis of the influence of these parameters on deformations during the drilling process of holes in the adapters of aircraft engine body accessories. The drilling process was carried out in the thin-walled superalloy Inconel 718, which is classified as a difficult-to-machine material. During the analyses, experimental studies based on the Response Surface Method (RSM) and finite element method (FEM) calculations were carried out simultaneously. The aim of this work was to analyze the developed mathematical models describing nonlinear relationships between cutting parameters, cutting forces, and deformations of the aircraft engine body characterized by a complex, thin-walled geometric structure. By using the proposed solutions, it is possible to achieve integration between the techniques of conducting research, performing calculations using FEM, and designing the machining. The advantage of this comprehensive approach used in our work is the development of mathematical models that strongly fit the results of the research. The results of analyses and calculations presented in the article and the research methodology used can be applied to industrial conditions.

MATHEMATICAL MODELING OF THE DYNAMICS OF THE AEROELASTIC "PIPELINE – PRESSURE SENSOR" SYSTEM

This paper proposes mathematical models of mechanical systems "pipeline - pressure sensor" designed to control the pressure of the working medium in the combustion chambers of engines. In such systems, to mitigate the impact of vibration accelerations and high temperatures, the sensor is connected to the engine using a pipeline and is located at some distance from it. The movement of the working medium is described by linear models of fluid and gas mechanics. To describe the dynamics of an elastic sensitive element, linear models of the mechanics of a solid deformable body are used. Based on linear differential equations with partial derivatives, mathematical formulations of problems are proposed that correspond to three-dimensional models of pressure measurement systems in gas-liquid media for some pipeline cross-sectional shapes, namely, for a pipeline with a rectangular cross-section, with a section in the form of a sector and in the form of a ring. By introducing integral characteristics, the solution of problems is reduced to studying one-dimensional models. Equations have been obtained that make it possible to determine the pressure of the working medium in the combustion chamber at each moment of time by the value of deformation of the sensitive element of the sensor. Analytical and numerical-analytical methods for solving the corresponding initial-boundary value problems for systems of differential equations are proposed. In the analytical approach, the solution of the problem is reduced to solving a differential equation with a deviating argument. The numerical-analytical study of the problem is based on the application of the Galerkin method. Also, a numerical experiment was carried out and examples of calculating the deformation of the sensitive element of the sensor in the case of rigid fastening when specifying specific values of the mechanical parameters of the system are presented, also during setting the law of change in the excess pressure of the working medium in the engine.

Evaluation of the parameters of contact interaction and wear of parts with cylindrical friction surfaces

The purpose of the presented research work was to evaluate various factors affecting the wear process of parts with cylindrical friction surfaces, which will allow to simulate their contact interaction taking into account the parameters of roughness and physico-mechanical properties of the surface layer.Methods. Modeling of the process of contact interaction of cylindrical surfaces is performed by considering the sliding contact of two cylindrical surfaces, represented as the contact of a smooth elastic sleeve and a shaft with the given (equivalent) values of roughness parameters. The modeling takes into account elastic deformations of conjugate bodies, as well as elastic-plastic deformations of micro-dimensions. When modeling a geometric contact, a certain section of the cylindrical surface is considered, located along the plane forming in the section of the cylinder passing through its axis. This section of the cylindrical surface is considered as an elementary area of the total geometric contact area of cylindrical surfaces and is a section of a cylindrical surface, the width of which is determined by the length of the larger axis of the ellipse at the base of the elliptical paraboloid when modeling a rough surface.Results. Based on the modeling of the contact interaction of cylindrical surfaces, the main factors influencing the process of their wear are established, such as: the actual contact area; the amount of convergence of the contacting surfaces; the actual pressure; the intensity of wear of the mating cylindrical surfaces. A kinetic wear model is proposed that takes into account the parameters of the roughness and physico-mechanical properties of the surface layer.Conclusion. Based on the proposed model of wear of parts with cylindrical friction surfaces, taking into account the parameters of roughness and physico-mechanical properties of the surface layer, it became possible to provide the required intensity of wear of cylindrical friction surfaces.

PREDICTION OF WELD-ABILITY CHARACTERISTICS OF DUAL-PHASE STEEL HCT600X BY NUMERICAL SIMULATION

Dual-phase (DP) steel plates are characterized by very good absorption capacity, so they are used in the automotive industry for body deformation zone parts. They are attached to the frame of the car-body by welding. Laser welding of dual-phase steels is gaining increasing importance in the automotive industry. In the present paper, the possibility of predicting the strength and deformation characteristics of laser-welded HCT600X steel sheets was analyzed based on experiments and numerical simulations. Butt joints were formed by YLS-5000 laser in two variants, which differ by laser power input and welding speed. The HCT600X- HCT600X with welded joint was analyzed based on microstructure and mechanical tests. The tensile strength and hardness of the welded joints were greater than those of the base material (BM). The microstructure of the weld metal (fusion zone) consisted of martensite, austenite and bainite, in the heat-affected zone it consisted of a mixture of martensite, bainite, ferrite and residual austenite. In numerical simulation, the finite-element mesh was created by linear volume elements refined in the weld region, and the Gauss model of the surface heat source was applied when modelling laser welding. The results of numerical simulation of the microstructure and selected mechanical properties were correlated with the experimental results.

Development of the reinforced concrete resistance theory in the zone about reinforcement

The actual problem of resistance of near-reinforcement zone of concrete is solved as a problem of volumetric stress-strain state with "closure" of output integral parameters of this zone on the rod scheme of the whole reinforced concrete element synthesizing hypotheses and dependencies of various disciplines of mechanics of solid deformation body, including fracture mechanics. The calculation model of the reinforced concrete element takes into account the effect of reinforced concrete of prof. Vl.I. Kolchunov describing the mechanism of formation and development of transverse and longitudinal cracks. In this case, generalized hypotheses of linear and angular deformations for warping and gradients of jumps of relative mutual displacements of reinforcement and concrete are adopted. New functionals of reinforced concrete are constructed, which are consistent with the ideas about resistance of crosssections of rod elements in near-reinforcement zones. Physical equations for a concrete matrix modeled between transverse cracks are written. The displacement components for the near-reinforcement area are found in relation to the crack opening width at the boundary of the "concrete-reinforcement" contact in transverse, longitudinal and radial cracks, respectively. The use of the accepted assumptions and multi-level calculation scheme for the near-reinforcement region significantly brings the calculation model closer to a real assessment of physical phenomena.

On elastic deformations of cylindrical bodies under the influence of the gravitational field

Background Elastic deformations of gravitating cylindrical bodies are relevant for state-of-the-art photonic experiments, as they affect the physical properties of materials under consideration, impacting wave propagation. This is of key importance for a recently planned experiment to explore the influence of the gravitational field on entangled photons propagating in waveguides. The purpose of this work is to determine these elastic deformations as functions of temperature, pressure, and of the gravitational field. We thus determine the deformations of the body due to changes of the gravitational field, and obtain stringent bounds on the control of temperature and pressure so that the effects of the associated elastic deformations on the photons propagating in a waveguide are smaller than the phase shifts associated with the change of the gravitational field. Methods We use the methods of linear elasticity, including thermoelasticity, to determine the stresses and strains of the medium. For this, the symmetry of the cylinder allows us to solve the problem by using Mitchell’s solutions of the equations satisfied by the Airy functions. The boundary conditions are implemented by an approximation of the Hertz contact method. Results We calculate the displacements, the stresses and strains for several classes of boundary conditions, and give explicit solutions for a number of physically motivated configurations. The influence of the resulting deformations on the planned GRAVITES experiment is determined. Conclusions The results are relevant for fiber interferometry experiments sensitive to the effects of the gravitational field on photon propagation. Our calculations give stringent bounds on the environmental variables, which need to be controlled in such experiments.

The Combination of X-ray Ct and Multi-particle Finite Element Method for Powder Compaction

Abstract The macroscopic mechanical properties of granular materials are closely related to their microscopic properties, and studying the compression problem of powder is helpful for establishing a constitutive law of powder compaction process. This study utilized X-ray CT technology to investigate the 3D numerical analysis model of loose particle stacking and compaction based on MPFEM, and investigated the mechanical behavior of powder under compression. The results of MPFEM were experimentally verified through powder uniaxial compression experiments, and the results showed that the calculated results of MPFEM were in good agreement with the experimental results. The method of X-ray CT can effectively capture the geometric characteristics of powder particles, and the MPFEM can obtain the true characteristics of plastic deformation of powder bodies, which is an important means of developing powder compaction constitutive models.

Mathematical models of system of measure of pressure variation in combustion chambers of engines

In this paper the mathematical modelling of a mechanical system designed to control changes in the pressure of the working medium in aircraft engines and consisting of a pipeline and a pressure sensor is carried out. The pipeline is necessary to take the sensor to some distance from the engine in order to mitigate the impact of high temperatures and vibration accelerations on the sensitive element of the sensor, which is an elastic plate. The system takes into account the aerohydrodynamic and thermal effects of the working medium on the plate. Asymptotic equations of aerohydrodynamics in the models of compressible and incompressible medium are used to describe the working medium motion in the pipeline. Both linear and nonlinear models of a deformable solid body are proposed to describe the plate dynamics. When using the compressible medium model, the solution of the problem is reduced to the study of an equation with a deviating argument. To solve the problem using the incompressible medium model, Fourier and Galerkin methods are applied. As a result, for both models the solution of the problem is reduced to the study of ordinary differential equations relating the magnitude of pressure in the motor with the magnitude of deformation of the sensing element, which can be used to control the mode of operation of the motor. The solution of these equations is found with the developed software program using standard functions of Mathematica 12.0. The paper was presented at PhysCon2024.

Analysis of elastic and rheological properties of tunnel anchorage support structure under the action of seepage flow

The large deformation and strong rheological characteristics of the underground rock body under complex geological conditions have led to the failure of the support system and even the instability of tunnels from time to time. Based on the theory of groundwater seepage, the elastic solution of the mechanical model of the tunnel anchorage support system under seepage is solved, which reveals the influence of seepage on the peripheral rock and the support parameters of the anchorage support system; the viscoelastic solution is solved according to the corresponding principle of elasticity—viscoelasticity, which analyses the influence of seepage on the rheological process of the anchorage support system; and the model is simulated with the help of finite element software, which analyses the agreement and discrepancy of the numerical solution and the theoretical solution. The results show that the analytical and numerical solutions are basically consistent. This study can provide important guidance for controlling long-term stability of water-rich tunnel rocks.

Validity of a virtual reality-based straight coloanal anastomosis simulator.

Current training methods for surgical trainees are inadequate because they are costly, low-fidelity, or have a low skill ceiling. This work aims to expand available virtual reality training options by developing a VR trainer for straight coloanal anastomosis (SCA), one of the Colorectal Objective Structured Assessment of Technical Skills (COSATS) tasks. We developed a VR-based SCA simulator to evaluate trainees based on their performance. To increase the immersiveness, alongside the VR headset, we used haptics as the primary method of interaction with the simulation. We also implemented objective performance metrics to evaluate trainee performance throughout the simulation. We presented our performance metrics to 27 participants for an Expert Consensus Survey (5-point Likert scale) and created weights for our metrics. The weighted average scores for the 24 task-specific metrics ranged from 3.5 to 5. Additionally, for the general metrics, the scores spanned from 3.3 to 4.6. In the second phase of our study, we conducted a study with 16 participants (novice n = 9, expert n = 7). Based on the performance, experts outperformed novices by 8.56% when referring to the total score (p = 0.0041). Three of the measurable metrics, purse suture (p = 0.0797), retracting the anvil (p = 0.0738), and inserting the colonoscope (p = 0.0738) showed a significant difference between experts and novices. Experts were smoother with their hand motions by 3.67% per second and took 70.77% longer paths to complete the same tasks. We created a high-fidelity coloanal anastomosis VR simulator. The simulator runs in real-time while allowing high immersion with a VR headset, deformable bodies, and a haptic device while providing objective feedback through performance metrics. Experts obtained higher scores throughout the simulation, including the quiz to demonstrate procedural knowledge, the metrics to demonstrate experience in steps/procedure, and control of their basic surgical skills and hand movements.

Mesh adaptation and dynamic positioning for the efficient simulation of lifting hydrofoil flows

Accurate simulations of the flow around lifting hydrofoils are challenging, since they need to capture the flow near the foil surface precisely, represent the free surface, and take into account body motion and deformation. Therefore, these simulations are often computationally expensive.This paper studies numerical methods to limit the costs of hydrofoil simulation. Mesh adaptation is used to efficiently capture the free-surface flow, to resolve flow details around the foil surface, and to ensure the accuracy of mesh motion techniques, like overset meshing. For maximum precision of the boundary-layer flow, adaptation is started from dedicated body-aligned meshes.Hydrofoil flexibility is taken into account through a linear eigenmode-based reduced-order model of the structural response. This approach removes the need to couple directly the fluid and structure solvers and reduces the computational overhead for fluid–structure simulation. Equilibrium positions for flexible and rigid motion are determined with a fixed-point iteration based on quasi-Newton and approximate models for the forces respectively, which eliminate the need for costly time-accurate simulation.Test cases demonstrate that these methods work together, providing accurate simulations of realistic hydrofoils with reasonable computational costs. Mesh adaptation allows to target a specific numerical uncertainty through the refinement threshold parameter. Together with the body-aligned ‘sock’ meshes, adaptive refinement produces the same accuracy as non-adapted meshes for up to 10 times less CPU hours. Both fluid–structure interaction methods lead to computations which have the same convergence speeds as for non-moving bodies. Thus, foil flexibility can be simulated for a computational overhead below 40% and it leads to significantly better agreement with experiments.

Deformation Modeling and Prediction of Concrete Dam Using Observed Air Temperature and Enhanced CatBoost Algorithm

Accurate prediction of concrete dam deformation is essential for ensuring structural safety and operational efficiency. This study presents a novel approach for monitoring and predicting concrete dam deformation using observed air temperature data, intelligent optimization, and machine learning techniques. To address the limitations of traditional statistical models in simulating the thermal effects on dam body deformation, this study proposes an improved hydraulic–air temperature–time (HTairT) deformation monitoring model. This model leverages long-term air temperature data and its lagged terms as critical input variables, enabling a more comprehensive understanding of thermal impacts on dam deformation. To capture the complex, nonlinear relationships between environmental factors and dam deformation behavior, we introduce the high-performance CatBoost gradient-boosting algorithm as a regressor. An enhanced Particle Swarm Optimization (PSO) algorithm is utilized for optimizing CatBoost’s parameters, enhancing the model’s predictive accuracy. A high concrete dam, currently in service, is selected as the case study, where two representative deformation monitoring points are used for validation. This research fills a gap by combining CatBoost with an optimized PSO in a deformation monitoring model, providing a novel approach that improves predictive reliability in long-term dam safety monitoring. Experimental results show that the enhanced PSO-optimized CatBoost algorithm achieves higher R2 and lower MSE and MAE values in multiple monitoring points. compared with other benchmark methods Moreover, the importance of factors affecting deformation can be identified using the proposed method, and experimental results indicate that water level and average air temperature of 1–2 days, 3–7 days, and 30–60 days are key factors affecting the deformation of high concrete arch dams.

Rigid and deformable bodies in nematic liquid crystals

Rigid and deformable bodies in nematic liquid crystals

Continuum Mechanics Applied to the Biomechanics of Motion.

Continuum mechanics is the discipline that studies the motion and deformation of material bodies and is at the basis of both solid mechanics and fluid mechanics. This work aims at highlighting how a basic education in modern continuum mechanics can be of fundamental importance not only in the biomechanics of tissue but also in the biomechanics of movement. The latter is largely based on rigid body mechanics, which can be considered as a simple particular case of the general theory of continuum mechanics. As an example, a straightforward methodology for the extraction of the angular velocity from motion analysis data is illustrated. The method is based on a quantity that is more primitive than the angular velocity: the spin tensor.