Solid Body Research Articles

Mechanical properties of additively manufactured lattice structures designed by deep learning

Lattice structures, characterized by their repetitive lightweight cellular forms, enable more effective load distribution compared to solid bodies. Designing lattice structures with tailored mechanical properties remains challenging due to the numerous design variables and their complex relationship with mechanical performance. This paper presents a novel approach employing a deep learning-based Generative Adversarial Network (GAN) model to address this engineering challenge. With its potential for creativity and innovation, GAN provides design diversity that cannot be achieved with traditional design methods or other generative design models. Distinct from previous studies, the GAN training data set consists of lattice structures with improved mechanical properties obtained using parametric design and simulated annealing method. This data set enables the GAN model to create lattice structures with high strength-to-weight ratio. These lattice designs were fabricated using a commercial Material Jetting Additive Manufacturing (MJ-AM) machine, allowing for the production of complex structures. The mechanical performance of the 3D-printed unit cell samples was evaluated through Finite Element Analysis (FEA), compression, and impact testing. The results reveal that the lattice structures generated using the GAN model demonstrated improved mechanical strength (i.e. up to 108 % and 150 % improved strength and elongation performance, respectively). This study shows AI's potential to widen lattice structure design space and create tailored parts with improved mechanical properties. The research also paves the way for future exploration of deep learning techniques in revolutionizing the design and fabrication of parts with tailored mechanical properties.

Description of a nationwide structure for monitoring nosocomial outbreaks of (highly resistant) microorganisms in the Netherlands: characteristics of outbreaks in 2012–2021

BackgroundBefore 2012, established national surveillance systems in the Netherlands were not able to provide a timely, comprehensive epidemiological view on nosocomial outbreaks. The Healthcare-associated Infections and AntiMicrobial Resistance Monitoring Group (SO-ZI/AMR) was initiated in 2012 for timely national nosocomial outbreak monitoring and risk assessment. This paper aims to describe the achievements of the SO-ZI/AMR by presenting characteristics of outbreaks reported in 2012–2021.MethodsHospitals and, since 2015, long-term care facilities (LTCF) were requested to report outbreaks when (1) continuity of care was threatened, or (2) transmission continued despite control measures. A multi-disciplinary expert panel (re-)assessed the public health risk of outbreaks during monthly meetings, using 5 severity phases and based on data collected via standardised questionnaires. We descriptively studied the panel’s consensus-based severity classification, distribution of (highly resistant) microorganisms, and duration and size of outbreaks between April 2012 and December 2021.ResultsIn total, 353 hospital outbreaks and 110 LTCF outbreaks were reported. Most outbreaks (hospitals: n = 309 (88%), LTCF: n = 103 (94%)) did not progress beyond phase 1 (no public health implications, outbreak expected to be controlled within two months), one hospital outbreak reached phase 4 (insufficient/ineffective response: possible public health threat, support offered). Highly resistant microorganisms (HRMO) were involved in 269 (76%) hospital and 103 (94%) LTCF outbreaks. Most outbreaks were caused by methicillin-resistant Staphylococcus aureus (MRSA; n = 93 (26%) in hospitals, n = 80 (72%) in LTCF), vancomycin-resistant Enterococcus faecium (VRE; n = 116 (33%) in hospitals, n = 2 (2%) in LTCF) and highly resistant Enterobacterales (n = 41 (12%) in hospitals, n = 20 (18%) in LTCF). Carbapenemase-producing gram-negative bacteria were involved in 32 (9.1%) hospital and five (4.5%) LTCF outbreaks. In hospitals, VRE outbreaks had the longest duration (median 2.3; range 0.0-22.8 months) and widest range of affected patients (median 9; range 2-483).ConclusionsThe SO-ZI/AMR provided national insight into the characteristics of nosocomial outbreaks over the past decade. HRMO outbreaks – mostly caused by MRSA, VRE (in hospitals) and highly resistant Enterobacterales – occurred regularly, but most of them were controlled quickly and did not develop into a public health threat. The SO-ZI/AMR has become a solid monitoring body, essential to assess risks and raise awareness of potential HRMO threats.

A computational approach to heat transfer and ablation in space capsule insulation

In this article, the heat transfers and ablation phenomena of thermal insulations utilized in manned space capsules are investigated. In this regard, by collecting and solving the equations related to ablation insulations, a computer program has been developed that is able to predict the thermal response of these insulations under various operating conditions. This approach considers mass and heat transfer equations in two-dimensional solid bodies. To solve these equations, finite volume method and implicit formulation for time dependence have been used. The reaction equation, written in the form of Arrhenius, is solved using the Runge-Kutta method, and the density and the flux of the gas produced at each step are obtained. Furthermore, a practical model with low computational requirements and execution time and execution time is presented to consider the regression rate based on determining the identifier for destroyed cells, charred cells, and virgin material. The research results demonstrate that increasing the thickness of the layers, the heat of decomposition and ablation, the intensity of the reaction, and reducing the thermal diffusion coefficient, density of char, and temperature of ablation enhance the efficiency of thermal insulation. Validation of the model with experimental results in silica-phenolic insulation reveals a good agreement between simulation and experimental observations. Additionally, it was shown that for a carbon-phenolic insulation with a thickness of 5 mm in the specified space capsule under the given conditions, the maximum recession rate is 1.9 mm at a maximum temperature of 1000 K and 4.9 mm at a maximum temperature of 1300 K.

Flow development region in the boundary layer: two-component molecular viscosity and partial slip

The subject of this study is the flow development region of laminar incompressible fluid flow in the boundary layer. This flow is an example where a direct application of the Navier-Stokes equations of gradient-free laminar incompressible fluid flow, in which the molecular viscosity is assumed to be a constant value independent of spatial coordinates, leads to a redefinition of the mathematical model. It is about the fluid boundary layer in the region of flow establishment in the motion problem of a semi-infinite plane, where the pressure gradient is zero. There is a situation when the number of equations is equal to three (two equations of momentum conservation and the equation of continuity), and the number of unknowns is equal to two - the number of the speed component. As a logical solution to the obtained inconsistency, it is proposed, as was already done for the problem of stationary motion of a plane and the problem of acceleration of a plane, to depart from the false statement about the constancy of molecular viscosity in the gradient-free boundary layer of an incompressible flow and consider molecular viscosity as a function of spatial coordinates. The need to consider the variable nature of molecular viscosity led to the discovery of another flaw in the Navier-Stokes theory. This non-trivial flaw was discovered during the application of the original numerical analytical method for solving the flow development region problem. The Navier-Stokes equations are supplemented by boundary conditions. The most important condition is the condition of fluid non-slipping on the surface of a solid body, which, by the way, does not follow any physical law. As a result, on the surface of a half-plane (or a moving body), the component of the velocity, which coincides with the direction of motion, has a constant value equal to the velocity of the body. It immediately follows from the continuity equation that the normal derivative of the normal component of the velocity must be equal to zero along the surface of the plane (body), since the longitudinal derivative of the velocity becomes zero. However, it is quite obvious that the velocity component normal to the surface of the plane (body) changes across the boundary layer in the region of current development, which indicates the presence of a normal gradient (both components) of the velocity. The conflict or contradiction is overcome by moving away from the generally accepted condition of non-slipping to the condition of partial non-slipping, or essentially the presence of sliding. Even with the sudden braking of any vehicle, the complete stop does not occur instantly, but after some finite time and distance, so in the case of the motion of a body in a stationary fluid, there is not an instant sticking, but a gradual one - from complete sliding, when a particle of liquid has just met a moving plane (body), to complete non-slipping at the end (and further) of the flow development region. Research methods. This work uses purely theoretical methods based on the use of calculus of variations, laws of physics, and ideas from everyday life. Conclusions. An improved model of a viscous Newtonian fluid in the area of flow development in the boundary layer was derived. On the basis of assumptions about the variable nature of the molecular viscosity, which already has two components, and the departure from the non-slipping condition, analytical solutions for both components of the velocity and both components of the molecular viscosity were obtained. A comparison of the obtained results with the results of other studies is presented.

An innovative quasi-bond approach to bridge continuity, anisotropic damage and macroscopic fracture of solids and structures

Spontaneous formation and evolution of discontinuities in solid media still poses one of the significant challenges in solid mechanics and computational mechanics. To facilitate numerical modeling, a new model called herein ‘quasi-bond’ model is proposed, which redefines the form of local interaction between material particles. Unlike traditional discrete methods that require direct connections between material particles, in this quasi-bond method, only one end of each bond is actually connected to a material particle, rendering great flexibility in describing bond distribution and anisotropic damage by bond breakage. Homogenization of solid body can be performed by an integral over quasi-bonds, while the process of crack nucleation, propagation and coalescence to form fracture is simulated through bond breakage. Especially, the relationship between material elastic constants and bond stiffness parameter is established in both two- and three-dimensional contexts. Furthermore, a smoothed strain-based fracture description is proposed with the ability of eliminating particle density/distribution dependence problems. Finally, several benchmark tests are conducted to demonstrate the efficiency and accuracy of the proposed approach in solving elasticity and fracture problems.

Матрична алгебра В як евклідовий простір

Representation of information by means of hypercomplex numerical systems is used in various problems of science and technology: in classical mechanics, solid body mechanics, electrodynamics, radio electronics, computer animation, and others [1]. Often a hypercomplex system (that is, a system whose elements are considered to be hypercomplex numbers) is understood as any finite-dimensional algebra over a field. An important place among such algebraic structures is occupied by matrix algebras. The impossibility of constructing algebras with division does not at all mean the impossibility of constructing algebras without division, but their properties are close to the first ones (use of defined division). Since each algebra of finite rank can be monomorphically immersed in some complete matrix algebra, this caused, so to speak, an inverse approach to the construction of new algebras. A certain subalgebra stands out from a complete matrix algebra, which is a matrix representation of an algebra of finite rank. It is the implementation of such an approach that makes it possible to endow elements of algebra of finite rank with matrix characteristics, in particular, a canonical representation of algebra elements is constructed through the spectral representation of a matrix, and the algebra itself is endowed with a topological structure through one of the matrix norms. At the same time, an additional condition is often imposed, that it be an algebra over the field of real or complex numbers. The article constructs a real algebra of finite rank, the elements of which are matrices of the second order with the same sum of rows and columns. We endowed it with a norm and a scalar product, demonstrating that it is a Euclidean space. This algebra is a matrix representation of the algebra of hypercomplex numbers, which we called binary in our research [4].

Анализ технологий заканчивания скважин с установкой скользящих муфт на фильтр

Mechanical cleaning filters are used to purify water, aqueous solutions, liquid and gaseous substances, hy-drocarbons, air from solid suspended particles of various sizes. Filters used in the field are steel cylindrical apparatuses with a solid and detachable body, inside which slotted or mesh filter partitions are installed, contributing to the purification of water. The principle of operation of mechanical cleaning filters is that when the filtrated medium passes through the filter element, solid particles will be retained. The main feature of such filters is the frequency of action due to the need to clean the filter element manually or automatically using a reverse flow of clean water. With a decrease in productivity, namely, with an increase in the pressure drop between the inlet and outlet, as well as in the lower part of the device, manual or automatic cleaning of the filter element from accumulated contaminants will occur. The article highlights the principle of sliding couplings for filters for water purification, as well as their use in construction. The stages of cleaning and the materials from which sliding filters are made to prevent leakage are considered. Recommendations are given for careful monitoring and following proper procedures to prevent leaks and pressure losses, to ensure the structural integrity and stability of the well, as well as to exclude contamination of the surrounding groundwater. The use of a mechanical filter is proposed, the body of which is designed for heating or fixing thermal insulation and which can be used with small flows of viscous media for cleaning from impurities.

On One Method for Calculating Nonstationary Heat Transfer between a Gas Flow and a Solid Body

A method for calculating the nonstationary thermal interaction between a viscous gas flow and a solid body is presented. The method consists in direct joint integration over time of the equations of gas dynamics of a multicomponent mixture and the heat equation in a solid on multi-block unstructured meshes. To calculate one time step, the system of governing equations is split into hyperbolic and parabolic subsystems. The numerical method provides approximation of the matching condition (continuity of temperature and the normal component of the heat flux) at the interface between gas and solid and is efficient for nonstationary calculations. The comparison with the analytical solution of the model problem of the interaction of a high-speed flow and a heated plate confirm the efficiency of the method.

Cross-linking gradient model in disperse systems

The article presents the research results of the disperse systems cross-linking process containing solid and liquid phase bases on the continuum mechanics apparatus use within the incompressible fluid model framework. The system formation schemes of interfacial layers in fine clearances between solid particles with wall-adjacent zones formation, in which conditions of liquid and solid phase interphase contact are provided, and the cores with constant interphase pressure are considered. The authors have obtained expressions for the values of wedging pressure depending on the thickness of the interfacial layers overlapping area, which determine the interfacial contacts strengthening degree. The dependences given in the paper are a theoretical basis for a new approach to modelling surface phenomena from the position of continuum mechanics equilibrium. The facilitating mechanism of the wedging pressure long-range action outside the interfacial layers system area is given. The authors present the modelling results of a single liquid-solid interphase layer bounded, on the one side, by a solid surface and, on the other side, by a volume liquid phase and the results of modelling the effects of structuring disperse systems based on the liquid interphase layer study formed in the clearance between solid surfaces. Under certain conditions in such systems the effect of structuring, leading to a sharp increase in the strength properties of disperse-filled composite materials, which is the basis of modern nanotechnology concepts, is manifested. The dualism of the liquid phase, consisting in the ability to exhibit the properties of both liquid and solid body, is shown. It is proved that the main disperse systems structure formation factor is the formation of interphase stresses powerful gradients at the thickness of interphase layers.

Аспекты численного моделирования процессов разрушения упруго-хрупких тел

Understanding the nucleation and evolution of microdefects in solid bodies is important to ensure the reliability and safety of critical structures and to identify their strength and deformation resources. In numerical modeling, failure zones can be represented as areas with significantly underestimated rigid characteristics by analogy with the method of variable elastic parameters used in solving the boundary-value problems of the theory of plasticity. However, the formal application of numerical algorithms of plasticity does not always lead to an adequate description of failure processes especially in elastic-brittle bodies. This paper considers some aspects of the numerical simulation of failure processes, such as the calculation of a stress-strain state after reducing the rigidity of finite elements under constant boundary conditions by organizing an appropriate iteration procedure, and the selection of the maximum number of finite elements fractured per iteration, the value of a loading step, and the discretization degree of the computational domain. The influence of the above aspects on the results of failure simulation is illustrated by comparing the numerical solutions to the problem of deformation of the strip made of elastic-brittle material with the edge stress concentrator, which were obtained by different algorithms. The loading diagrams were plotted, and the implementation of the post-critical stage at the macro level was demonstrated. Failure kinetics was analyzed for different variants of implementation of the iterative procedure and at a variable number of elements fractured per iteration. It has been found that, in order to get an accurate description of deformation and failure processes, the automatic selection of a loading step seems to be more reasonable. Analysis has indicated that the discretization degree of the computational domain has a strong impact on the modeling results. This suggests that the finite element size should correspond to a certain strength constant of a material having the dimensions of length.

On One Method for Calculating Nonstationary Heat Transfer between a Gas Flow and a Solid Body

On One Method for Calculating Nonstationary Heat Transfer between a Gas Flow and a Solid Body

Melting interfaces in induction heated bodies

A numerical study of the solution of the mathematical problem corresponding to the melting of a solid metallic body, heated by the action of an exterior electromagnetic field, is presented. The extended finite element method is used for the numerical analysis. The melting interface is geometrically modeled by a level set function whose evolution is obtained by applying a discontinuous Galerkin method to the Hamilton-Jacobi equations.

Amplitude–Frequency Characteristics and Stability Regions of a Two-Layer Liquid under the Angular Vibrations of a Solid Body

Amplitude–Frequency Characteristics and Stability Regions of a Two-Layer Liquid under the Angular Vibrations of a Solid Body

Vibrational Movement of a Solid Body along an Inclined Surface

Vibrational Movement of a Solid Body along an Inclined Surface

A combined volume penalization/selective frequency damping approach for immersed boundary methods: Application to moving geometries

High-order numerical techniques and immersed boundary methods (IBMs) are gaining popularity to avoid constructing body-fitted meshes while accurately resolving complex flows on Cartesian grids. Recently, we have presented a new treatment for the immersed boundary method based on the combination of volume penalization and selective frequency damping (SFD) [J. Kou and E. Ferrer, “A combined volume penalization/selective frequency damping approach for immersed boundary methods applied to high-order schemes,” J. Comput. Phys. 472, 111678 (2023).], that offers improved accuracy for nonmoving geometries. The objective of SFD is to remove nonphysical, high-frequency oscillations inside the solid body and by doing so enhance the accuracy in the fluid region. The present paper extends the new immersed boundary treatment to moving geometries. The convergence of this approach is first validated by the method of manufactured solutions, where we design a one-dimensional advection–diffusion case, with a moving interface, to validate the numerical accuracy. Second, we simulate an unsteady flow past a plunging circular cylinder (Navier–Stokes solver). In this case, we show that the combination of volume penalization and SFD provides improved accuracy for moving geometries.

PLASTIC DEFORMATION WITH OPEN STITCHING. FORMULATION OF THE PROBLEM

A new method for the analytical solution of complex variational problems in the mechanics of a deformable solid body is proposed. Its effectiveness will be demonstrated in a series of articles on firmware. The first article systematizes the regularities of this process and performs a theoretical analysis of the billet upsetting stage.

Jumping Platonic Solids on a Vibrating Plate

AbstractThe mechanical excitation of solid bodies by a vibrating plate is not only an interesting fundamental problem, but also has relevance in many mechanical systems, for example, in the preparation of granular gases in microgravity. Herein, the energy input by an oscillating plate is numerically investigated as a function of the excitation parameters for selected Platonic solids and their behavior compared to that of a jumping sphere. The most important additional features, not relevant for spheres, are the excitation of body rotations and a permanent energy exchange between the rotational and translational degrees of freedom during the collisions with the plate. The distribution of kinetic energies is analyzed by a numerical simulation of the dynamics, using structures which emulate the mechanical behavior of regular polyhedra.

Numerical simulation of the diesel engine starting considering air pre-heating in the intake system

BACKGROUND: Low temperature of the intake air is one of the reasons of difficult starting of a cold diesel engine in conditions of negative outside temperatures. For a reliable staring of a cold diesel engine, it is necessary to have the temperature at the end of the compression stroke higher than the fuel self-ignition temperature. As the temperature at the end of the compression stroke is defined, first, by the temperature at the end of the intake stroke, the mentioned condition can be satisfied with preliminary warming of the air entering in a cylinder. AIMS: The article is devoted to solving the task related to development of a mathematical model of a diesel engine taking into account air pre-heating in the intake system and ensuring simulation of the pre-starting mode, starting and operation of a diesel engine in conditions of low negative outside temperature. METHODS: The enhanced mathematical model of a diesel engine basing on heat mechanics (thermodynamics of opened systems) which reflects main features of an internal combustion engine (ICE) as the system transforming energy in time domain is proposed in the article. The mathematical model’s equation system is based on laws of conservation of energy and mass, solid bodies’ motion equation and includes differential equations of changing of temperature and density of the working body in a cylinder, in the intake system and in the ICE’s crankcase, the ideal gas state equation as well as differential equations of changing of rotation velocity and rotation angle of an engine’s crankshaft. RESULTS: The mathematical model was tried out on the example of the 1Ch9.5/8.0 multi-purposed air-cooled diesel engine. The results of simulation of the pre-starting mode, starting and operation of the diesel engine taking into account air pre-heating in the intake system are presented in the article. CONCLUSIONS: Implementation of air pre-heating at the intake in the design of diesel engines is the most effective way of ensure starting of the engines at low negative outside temperature. The obtained results help to develop recommendations of choosing power and operation modes of pre-heating devices for ensuring starting and operation of diesel engines in conditions of low negative outside temperatures.

Range of motion after 1, 2, and 3 level cervical disc arthroplasty

BackgroundMotion of a solid body involves translation and rotation. Few investigations examine the isolated translational and rotational components associated with disc arthroplasty devices. This study investigates single- and multi-level cervical disc arthroplasty with respect to index and adjacent level range of motion. The investigators hypothesized that single- and multilevel cervical disc replacement will lead to comparable or improved motion at implanted and adjacent levels. MethodsSeven human cervical spines from C2 to C7 were subjected to displacement-controlled loading in flexion, extension, and lateral bending under intact, 1-Level (C5–C6), 2-Level (C5–C6, C6–C7) and 3-Level (C5–C6, C6–C7, C4–C5) conditions. 3D motions sensors were mounted at C4, C5, and C6. Motion data for translations and rotations at each level for each surgical condition and loading mode were compared to intact conditions. Results1-Level: The index surgery resulted in statistically increased translations in extension and lateral bending at all levels with statistically increased translation observed in flexion in the superior and inferior levels. In rotation, the index surgeries decreased rotation under flexion, with remaining levels not statistically different to intact conditions. 2-LevelA device placed inferiorly resulted in statistically increased translations at all levels in extension with statistically increased translations superior and inferior to the index level in flexion. Lateral bending resulted in increased nonsignificant translations. Rotations were elevated or comparable to the intact level for all loading. 3-LevelTranslations were statistically increased for all levels in all loading modes while rotations were elevated or were comparable to the intact level for all loading modes and levels. ConclusionsMicromotion sensors permitted monitoring and recording of small magnitude angulations and translations using a loading mechanism that did not over constrain cervical segmental motion. Multilevel cervical disc arthroplasty yielded comparable or increased overall motion at the index and adjacent levels compared to intact conditions.

Геоходная технология строительства подземных выработок: необходимость создания

The article discusses the need to create geokhod-based technologies for construction of underground workings. It reviews the main drawbacks of the current tunneling technologies. A new approach is emphasized to driving underground workings and shaping of underground space, where tunneling is initially considered as the movement process of a solid body, i.e. the tunneling machine, through the surrounding rocks (the geologic environment). The main structural elements of the technological mode to shape, i.e. to develop, the underground space are considered based on the priority development of new approaches to construction geotechnology and geotechnics. In the process of shaping one of the structural elements of the technological mode, i.e. the design and technological tools, the first priority is to create a range of technologies to drive underground workings for various purposes and location within the subsurface space and for different geological environments. The authors have formed the concept of Geokhod tunneling technologies and defined their application areas. The need for the development of new design and technological solutions related to rock support with the perimeter support and, especially, to the challenges of driving tunnels of variable cross-section is identified.