Verification Of Computational Models Research Articles

An enhanced deep learning approach for vascular wall fracture analysis

AbstractThis work outlines an efficient deep learning approach for analyzing vascular wall fractures using experimental data with openly accessible source codes (https://doi.org/10.25835/weuhha72) for reproduction. Vascular disease remains the primary cause of death globally to this day. Tissue damage in these vascular disorders is closely tied to how the diseases develop, which requires careful study. Therefore, the scientific community has dedicated significant efforts to capture the properties of vessel wall fractures. The symmetry-constrained compact tension (symconCT) test combined with digital image correlation (DIC) enabled the study of tissue fracture in various aorta specimens under different conditions. Main purpose of the experiments was to investigate the displacement and strain field ahead of the crack tip. These experimental data were to support the development and verification of computational models. The FEM model used the DIC information for the material parameters identification. Traditionally, the analysis of fracture processes in biological tissues involves extensive computational and experimental efforts due to the complex nature of tissue behavior under stress. These high costs have posed significant challenges, demanding efficient solutions to accelerate research progress and reduce embedded costs. Deep learning techniques have shown promise in overcoming these challenges by learning to indicate patterns and relationships between the input and label data. In this study, we integrate deep learning methodologies with the attention residual U-Net architecture to predict fracture responses in porcine aorta specimens, enhanced with a Monte Carlo dropout technique. By training the network on a sufficient amount of data, the model learns to capture the features influencing fracture progression. These parameterized datasets consist of pictures describing the evolution of tissue fracture path along with the DIC measurements. The integration of deep learning should not only enhance the predictive accuracy, but also significantly reduce the computational and experimental burden, thereby enabling a more efficient analysis of fracture response.

MODELING OF THE ELECTRONIC AND ELASTIC PROPERTIES OF THE Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub> CRYSTAL

In this scientific work, we conducted a comprehensive study of yttrium aluminum garnet using computer modeling methods. Our efforts are focused on the precise analysis of elastic properties, the development of equations of state, as well as a detailed study of crystal and band structures. We conducted a detailed study of the mechanical parameters of the material, such as the modulus of elasticity and the Poisson's ratio, using modern computational methods. Virtual modeling methods allow us to study in detail the mechanical characteristics of the material. The main focus is on the creation and verification of computer models that accurately reflect the elastic properties of the crystal. The values obtained using various hybrid functionals were compared with experimental data. Virtual models allowed not only to study in detail the mechanical characteristics of the material, but also provided results that are significantly close to real experimental data. Comparisons were carried out according to the following parameters: cell parameters, band gap energy, effective charges of crystal atoms, equations of state and elastic properties. Also, the error levels relative to the experimental data are determined. We present the results of the analysis of the crystal structure of yttrium aluminum garnet achieved using various exchange-correlation hybrid functionals such as B3PW, B3LYP, HSE06, PBE. This aspect of the study includes the analysis of the crystal lattice parameters, the distribution of atoms in the crystal and the band structure, which is important for a complete understanding of the properties of the material.

Computational model verification and numerical analysis of plate buckling due to combined loading

Thin plates are structures widely used in different industries, due to their mechanical properties. They are often subjected to combined loading, which can cause an undesired phenomenon called buckling. In this sense, the present work analyzes the elasto-plastic buckling behavior of thin steel plates that are simply supported and subjected to in-plane uniaxial or biaxial compression combined with lateral pressure. To obtain the ultimate stress of the plates, a computational model was developed using the finite element method. Initially, the computational model was verified through previous numerical results from the literature. Then, a case study was carried out considering a rectangular plate geometry with an aspect ratio of b/a = 0.5 (where a and b are the length and width of the plate, respectively), under biaxial compression and varying the lateral loading from 0 to 0.152 MPa, aiming to analyze its elasto-plastic buckling behavior. The results indicated that the computational model was adequately verified. From the case study, it was inferred that the load step plays an important role in the numerical prediction accuracy of the elasto-plastic buckling mechanical behavior of plates In addition, the application of initial imperfection for small lateral pressures has little influence on ultimate stress, while for larger lateral pressures it does not generate influence.

Computational Model Verification and Validation of Elastoplastic Buckling Due to Combined Loads of Thin Plates

Thin plates are widely used in various engineering applications. In some cases, these structural components may buckle due to compressive loads, which can be aggravated by lateral loads. Several authors have studied the elastoplastic buckling behavior of thin plates considering parameters such as material and geometric properties, support conditions, and initial out-of-plane imperfections. Some studies have also investigated the effects of notches and holes on the ultimate buckling stress of thin plates. The main goal of the present work is to verify and validate a computational model developed using the Finite Element Method via ANSYS® software, to simulate the mechanical behavior of metallic plates under uniaxial or biaxial compression combined with lateral load. The proposed numerical model was verified and validated by comparing its results with analytical, numerical, and experimental solutions found in the literature, reaching maximum differences and errors of around 5%. In sequence, the verified and validated computational model was used in a simple case study: a simply supported plate with a centered rectangular perforation and subjected to an in-plane compressive biaxial load combined with a lateral load, considering five different metallic materials: AISI 4130 steel, AH-36 steel, spheroidal graphite iron (SGI), compact graphite iron (CGI) and Al 7075-T651 aluminum alloy. The results obtained are consistent and, as expected, prove the applicability of the proposed computational model. From this, the biaxial elastoplastic buckling behavior was evaluated, indicating that among the studied cases the higher ultimate stress and the smallest maximum deflection were achieved, respectively, by the plates made of AISI 4130 steel and AH-36 steel.

Computational Experiments for Complex Social Systems—Part II: The Evaluation of Computational Models

Computational experiments are an important method for carrying out the quantitative analysis of complex systems and play a major role in mapping the real world to the virtual world. However, the flexibility of computational experiments leads to arbitrary modeling processes and unconvincing results, which greatly hinder the large-scale application of this method. In this context, the verification of computational models has become an urgent problem in this field. Currently, model evaluation is still in its infancy and the existing evaluation methods are not mature enough. Thus, we took epidemic models as the research object and proposed a capability maturity evaluation framework for computational models of artificial society. The framework differs from previous assessment methods that focus on the validity of results, but instead provides a comprehensive evaluation from two perspectives: 1) evaluation of the model itself—by comparing the expectation with the final implementation, we can obtain whether the model meets the expectation and 2) comparison between different models—by evaluating the implementation process of each model and comparing the results, we can identify more mature models. The implementation of the model is evaluated from input, process, and output. Further, specific analyses and evaluations are conducted for several representative COVID-19 models to verify the validity of this evaluation framework. The results of the case study show that the proposed evaluation framework can help decision-makers identify more mature and referential models, and point out the directions where modelers can improve their models.

Verification of Finite Element Computational Model for Biaxial Buckling of Stiffened Plates

This study presents the verification of computational models for the analysis of biaxial buckling in plates. The verification was performed by comparing the numerical results obtained in this study with results found in scientific references published by other authors. The computational models were developed in the ANSYS® software, which is based on the Finite Element Method (FEM), and the SHELL 281 element is used. The mesh convergence tests demonstrate the convergent behavior of the simulations performed for the analyzed examples, which are: a square plate under biaxial elastic buckling, and a rectangular plate with stiffeners under biaxial elasto-plastic buckling. From the converged mesh, maximum differences of 0.84% and 3.89% were achieved when compared with references, respectively, for the elastic and elasto-plastic biaxial buckling. These results indicate that the proposed computational models were adequately verified.

ИСПОЛЬЗОВАНИЕ РИФЛЕНЫХ ПОВЕРХНОСТЕЙ ДЛЯ УЛУЧШЕНИЯ ГИДРОДИНАМИЧЕСКИХ, КАВИТАЦИОННЫХ И АКУСТИЧЕСКИХ ХАРАКТЕРИСТИК КРЫЛЬЕВ И ЛОПАСТНЫХ СИСТЕМ ДВИЖИТЕЛЕЙ (ОБЗОР)

The paper reviews the use of grooved surfaces and sawtooth (chevron) edges to control the flow parameters of the wings, propeller blades and elements of vane propulsion systems operating in both gaseous and liquid media. Particular attention is paid to the physical mechanisms of improving the hydrodynamic, cavitation and acoustic characteristics under the influence of a grooved surface. These mechanisms are associated with a change in the flow structure in the region of the laminar-turbulent transition, the peculiarities of the occurrence of cavitation and acoustic radiation in the region of the outgoing edges. The results of the verification of computational models describing the behavior of the flow taking into account the laminar-turbulent transition, the use of which is necessary for studying flows near a grooved surface, are presented.

РАСЧЕТНО-ЭКСПЕРИМЕНТАЛЬНЫЙ МЕТОД ИССЛЕДОВАНИЯ ШИРОКОХОРДНОГО ВЕНТИЛЯТОРА АВИАЦИОННОГО ДВИГАТЕЛЯ НА ОТСУТСТВИЕ АВТОКОЛЕБАНИЙ

The main gas-dynamic parameters are considered for studying of the absence of flutter wide-chord fan of aircraft engine. The experimental-rated method is proposed to confirm the absence of flutter on the fan in the entire operating range of the aircraft engine. The method is based on experience in the design and development of aircraft engine fans. The method proposes the limitations of the study area of operation of a wide-chord of the aircraft engine fan. The method shows the boundaries of the possible operation of a wide-chord of the aircraft engine fan, taking into account the limitations of the studied range for the research and development of the testing. The aircraft flight parameters were processed with the control of the absence of flutter using pressure pulsation gauges. The results of processing the studied flight parameters are generalized and systematized. A technique for graphically depicting of the main controlled parameters of the method in a two-dimensional and three-dimensional setting is shown, indicating the boundaries of the possible range of operation, the wide-chord fan of the aircraft engine under study, taking into account the reserves of pressure and temperature. To verify the method, the test points of the fan are graphically showed in a thermal vacuum chamber of a similar sized fan of an aircraft engine, which, as the figures show, lie near the boundaries proposed in the method. It is proposed to use the studied points with a proven absence of flutter for verification of computational models using software systems and methods, for calculating the absence of flutter, taking into account the limits of possible operation defined in the method. The proposed boundaries of the studied ranges will significantly reduce the list of tests at the flying laboratory and the number of design points, which will allow us to make the best option for checking the absence of self-oscillations of the aircraft engine fan by the experimental-rated method in Ukraine without using a thermal pressure vacuum chamber and flying in hot and cold conditions.

Creation and verification of computational models for analysis of the mechanical behaviour of jet engines composite components under high-velocity impact: main problems and basic recommendations

Currently, modern CAE programs like ANSYS, LS-DYNA, ABAQUS, Simcenter 3D etc. are widely used to develop each engineering product. CAE reduces development costs and speeds up product launches. Computer modelling allows eliminating unsuccessful design options at early design stages and minimising or eliminating critical design changes at the prototype testing stage. Computer simulations are especially needed for the development of high-performance perfection designs like jet engines. The use of composites in the engines requires the availability of appropriate design tools to assess the mechanical behaviour of structural elements made of such materials under operational loads and in an emergency. Predictive modelling of the deformation and fracture of the composite fan blades and fan case subjected to dynamic loading cause considerable interest of engineers. As in the case of simulation of shock loading of metals, a model of a composite material must be verified. However, the problem is that the fibrous composite material itself is already a structure and can be modelled in various ways: without considering the layered structure (homogeneous approach) taking the mesostructure into account (at the ply-level or at the yarn-level) taking the microstructure into account (at the filament level). The requirements for the initial data, the number of parameters determined during the verification process, the complexity of creating geometric models will differ in each case. This paper briefly describes the main approaches to the numerical simulation of composite elements under high-velocity impact loading. The main advantages and disadvantages of these approaches are also considered. On the example of the meso-scale approach, the main parameters of the computational models that affect the results of calculations are shown. Based on the obtained data, the main recommendations were formulated on the validation of meso-scale models of composites.

THERMODYNAMIC ANALYSIS AND SIMULATION OF STEAM TURBINE POWER PLANT HYBRID WITH PARABOLIC TROUGH COLLECTORS; A STUDY IN IRAQ

Fossil fuel thermal power plants are major investments for electricity production despite of their environmental drawbacks. Using solar energy in a hybrid manner with these power plants a sensible and an economical choice for advanced power generation. In this study, thermodynamic analysis and simulation of a steam turbine power plant hybrid with parabolic trough solar collector field is done. Design process includes selection of heat transfer fluid (HTF), determination of the required solar power, orientation and sizing of the solar field, preliminary design of the solar heat exchanger (HEX) and thermodynamic analysis of the hybrid plant. After verification of computational model, simulations of steam power plant and hybrid power plant are done and results for increasing output electricity and saving fuel oil are studied considering the efficiency improvement and the environmental effects. Important solar field parameters like HTF, glass and absorber temperatures, heat loss coefficients and output power of the collector field are simulated and discussed. Finally, a simple economic analysis is done using levelized cost of energy method (LCOE) which showed that hybridization is economically sound. The study also suggests that, hybridization is a sensible choice for increasing efficiency and output power, decreasing use of fossil fuels, thus environment problems. The orientation of the hybrid connection plays an important role on these parameters.

Phase Fraction and Evolution of Additively Manufactured (AM) 15-5 Stainless Steel and Inconel 625 AM-Bench Artifacts.

A proper understanding of the structure and microstructure of additively manufactured (AM) alloys is essential not only to the prediction and assessment of their material properties, but also to the validation and verification of computer models needed to advance AM technologies. To accelerate AM development, as part of the AM-Bench effort, we conducted rigorous synchrotron-based X-ray scattering and diffraction experiments on two types of AM alloys (AM 15-5 stainless steel and AM Inconel 625). Taking advantage of the high penetration of synchrotron hard X-rays, we determined the phases present in these alloys under different build conditions and their statistically meaningful phase fractions using high-resolution X-ray diffraction. Using in situ multi-scale X-ray scattering and diffraction, we quantitatively analyzed the phase evolution and development of major precipitates in these alloys as a function of time during stress relief heat treatments. These results serve to validate AM microstructure models and provide input to higher-level AM processing and property models to predict the material properties and performances.

Suspended monorail emergency braking trolley computational model verification based on bench tests

This article presents a test bench for the conducting of emergency braking tests. The test bench can be found at the laboratory of the Central Mining Institute. The second part of the article describes a computational model of a braking trolley and of the aforementioned test bench, developed at the KOMAG Institute of Mining Technology. It then proceeds to compare the bench test results with the numerical calculation results obtained at KOMAG. The braking trolley computational model was developed for the purposes of project INESI, in order to conduct analyses of the influence of a suspended monorail’s speed increase on the track load during emergency braking.

Vortex shedding from a circular cylinder in shear-thinning Carreau fluids

Results from numerical simulations of two-dimensional, shear-thinning Carreau fluid flow over an unconfined circular cylinder are presented in this paper. Parametric sweeps are performed over the various Carreau model parameters, and trends of the time-averaged force coefficients and vortex characteristics are reported. In general, increased shear-thinning results in lower viscous forces on the body but greater pressure forces, resulting in a complex non-monotonic drag response. Lift forces generally increased with shear-thinning due to the dominant pressure contribution. The decrease in fluid viscosity also led to shorter vortex formation lengths and the consequent rise in the Strouhal frequency of vortex shedding. It is expected that these results will be useful for verification of computational models of unsteady non-Newtonian flows.

Wheat leaf epidermal pattern as a model for studying the influence of stress conditions on morphogenesis

The leaf epidermis of a monocotyledonous plant is a widely used model system for studying the differentiation of plant cells, as it contains readily observable specialized cells. The approach proposed in this paper uses a growing cereal leaf to study stress-induced dynamic changes in morphogenesis. In the process of formation, the linear leaf of wheat remains in the stationary growth phase for long. This fact permits us to observe a series of successive morphogenetic events recorded in the cellular structure of the mature leaf. In studying the cellular architecture of the wheat leaf epidermis, we obtained and processed confocal 3D images of wheat leaves stained with fluorescent dyes. This procedure allows an accurate morphometric description and determination of quantitative characteristics of the leaf epidermal pattern. Low temperatures are among the factors limiting the growing of crop plants in the temperate zone. In the present work, we show significant aberrations of stomatal morphogenesis in the epidermis of boot leaves of wheat varieties Saratovskaya 29 and Yanetskis Probat in response to cold stress. We found that nonfunctional stomata predominated in the zone of maximum manifestation of stress, whereas in the zones formed before and after the stress impact, the developmental anomalies come to the disturbance in the morphogenesis of subsidiary cells. In Saratovskaya 29, a significant amount of ectopic trichomes formed in rows predetermined to stoma formation. The proposed approach can provide standardized qualitative and quantitative data on stress-induced morphogenesis aberrations in wheat leaf epidermis. Subsequently, these data can be used for verification of computer models of leaf morphogenesis. Further study of the mechanisms of the effect of cold stress on morphogenesis will add to the search for additional opportunities to increase wheat yields in areas of risky agriculture.

How to Relate Models to Reality? An Epistemological Framework for the Validation and Verification of Computational Models

Agent-based simulations have become increasingly prominent in various disciplines. This trend is positive, but it comes with challenges: while there are more and more standards for design, verification, validation, and presentation of the models, the various meta-theoretical strategies of how the models should be related to reality often remain implicit. Differences in the epistemological foundations of models make it however, difficult to relate distinct models to each other and to ensure a cumulative expansion of knowledge. Concepts and the analytic language developed by philosophers of science can help to overcome these obstacles. This paper introduces some of these concepts to the modelling community. It also presents an epistemological framework that helps to clarify how one wishes to generate knowledge about reality by the means of one's model and that helps to relate models to each other. Since the interpretation of a model is strongly connected to the activities of model verification and validation, these two activities will be embedded into the framework and their respective epistemological roles will be clarified. The resulting meta-theoretical framework aligns well with recently proposed frameworks for model presentation and evaluation.

Experimental Verification of Computational Model of Magnetized Segment of Pipeline with Artificially Created Defects

A computational model of a magnetized segment of a pipeline created for the software of a new and promising method of internal pipe flaw detection is presented. Verification of the applicability of the computational model is performed on a test bench containing a control segment of the pipe with artificially created defects of different shapes. The values of the induction of the magnetic field inside the pipe near the defects obtained by means of the computational model are compared to data obtained in the course of measurements of the magnetic field by variable inductance and flux-gate transducers. Recommendations to improve the capabilities of fl aw detection measurement systems are given on the basis of an analysis of the results of a calculation.

Influence of building characteristics on tunnelling-induced ground movements

The interaction mechanisms between surface structures and tunnelling-induced ground movements were investigated through centrifuge testing. Although numerous studies have considered this soil–structure interaction problem, previous experiments have neglected important building characteristics and field data inherently contain numerous uncertainties related to the soil, the structure and the tunnelling procedure. Consequently, the interpretation of results and validation of computational models can be problematic. In this study, tunnelling beneath three-dimensional printed structural models with varying building characteristics (i.e. position, length and facade openings) was simulated in a centrifuge. The experimental results demonstrate that tunnelling induces soil displacements at the surface and subsurface that are notably altered due to nearby structures. Specifically, different amounts of vertical and horizontal ground movements, soil dilation and widening of settlement troughs were observed. Building distortions and horizontal building strains were also affected by the relative position of the building to the tunnel, the building length and the area of facade openings. The experimental results provide important data for the evaluation of current design methods and verification of computational models.

Dynamical Analysis of a Cable Manipulator Using Multibody Approaches

This paper deals with the creation of a computational model of a particular cable manipulator composed of a rigid manipulator with three degrees of freedom and a platform driven by four fibers. Each fiber is led over a pulley and is driven by a linear motor, which can be controlled. The multibody dynamics approach is a suitable way in order to create the manipulator model. The most common cable modelling techniques are summarized in this paper and then the computational model of the cable manipulator QuadroSphere is created using MSC.Adams software. The computational model verification is done using the modal analysis of linearized model and the experimental modal analysis on the real set up. Further results of various numerical simulations are presented and their utilization is discussed.

Belousov-Zhabotinsky autonomic hydrogel composites: Regulating waves via asymmetry.

Belousov-Zhabotinsky (BZ) autonomic hydrogel composites contain active nodes of immobilized catalyst (Ru) encased within a nonactive matrix. Designing functional hierarchies of chemical and mechanical communication between these nodes enables applications ranging from encryption, sensors, and mechanochemical actuators to artificial skin. However, robust design rules and verification of computational models are challenged by insufficient understanding of the relative importance of local (molecular) heterogeneities, active node shape, and embedment geometry on transient and steady-state behavior. We demonstrate the predominance of asymmetric embedment and node shape in low-strain, BZ-gelatin composites and correlate behavior with gradients in BZ reactants. Asymmetric embedment of square and rectangular nodes results in directional steady-state waves that initiate at the embedded edge and propagate toward the free edge. In contrast, symmetric embedment does not produce preferential wave propagation because of a lack of diffusion gradient across the catalyzed region. The initiation at the embedded edge is correlated with bromide absorption by the inactive matrix, which locally elevates the bromate concentration required for catalyst oxidation. The competition between embedment asymmetry and node geometry was used to demonstrate a repeatable switch in wave direction that functions as a signal delay. Furthermore, signal propagation in or out of the composite was demonstrated via embedment asymmetry and relative dimensions of a T-shaped active network node. Overall, structural asymmetry provides a robust approach to controlling initiation and orientation of chemical-mechanical communication within composite BZ gels.

A Novel Method to Verify Multilevel Computational Models of Biological Systems Using Multiscale Spatio-Temporal Meta Model Checking.

Insights gained from multilevel computational models of biological systems can be translated into real-life applications only if the model correctness has been verified first. One of the most frequently employed in silico techniques for computational model verification is model checking. Traditional model checking approaches only consider the evolution of numeric values, such as concentrations, over time and are appropriate for computational models of small scale systems (e.g. intracellular networks). However for gaining a systems level understanding of how biological organisms function it is essential to consider more complex large scale biological systems (e.g. organs). Verifying computational models of such systems requires capturing both how numeric values and properties of (emergent) spatial structures (e.g. area of multicellular population) change over time and across multiple levels of organization, which are not considered by existing model checking approaches. To address this limitation we have developed a novel approximate probabilistic multiscale spatio-temporal meta model checking methodology for verifying multilevel computational models relative to specifications describing the desired/expected system behaviour. The methodology is generic and supports computational models encoded using various high-level modelling formalisms because it is defined relative to time series data and not the models used to generate it. In addition, the methodology can be automatically adapted to case study specific types of spatial structures and properties using the spatio-temporal meta model checking concept. To automate the computational model verification process we have implemented the model checking approach in the software tool Mule (http://mule.modelchecking.org). Its applicability is illustrated against four systems biology computational models previously published in the literature encoding the rat cardiovascular system dynamics, the uterine contractions of labour, the Xenopus laevis cell cycle and the acute inflammation of the gut and lung. Our methodology and software will enable computational biologists to efficiently develop reliable multilevel computational models of biological systems.