Finite Element Numerical Model Research Articles

Crushing performance of a novel tetra-missing rib honeycomb: Experimental and numerical studies

Based on the unique monoclinic characteristics of the plastic deformation of the tetra-missing rib honeycomb, the symmetrical design of the whole and subunits of the tetra-missing rib honeycomb was carried out in this paper, and two new types of tetra-missing rib honeycomb with symmetrical structural characteristics were obtained. First, quasi-static compression was performed on three structures, including a conventional tetra-missing rib honeycomb, and the experimental results showed that both symmetrical designs could effectively improve the plastic deformation of the conventional tetra-missing rib honeycomb. At the same time, round holes were introduced into the three honeycomb structures, and the mechanical properties and deformation modes of the three structures under quasi-static loads were explored. The results of two sets of experiments were compared, and it was found that the introduction of round holes could improve the structural stiffness of the honeycomb. Second, Abaqus/Explicit was used to construct a finite element numerical model in the later stage, and the accuracy of the model was verified. The number of honeycomb cells was determined for the three honeycomb structures, and finally, the dynamic Poisson's ratio of the honeycomb structure in plastic deformation was determined, and the negative Poisson's ratio (NPR) effect of the three honeycombs was compared.

Machine learning-aided generative design methodology for a Martian regolith habitation shell

This study presents a novel design methodology to automate the development process of a regolith habitation shell for a crewed mission on Mars. The integration of generative design, simulation tools, and data science methodologies allows for a systematic and comprehensive iterative design process, which facilitates the development of dual-habitation shells that can resist harsh conditions on Mars.The study establishes a methodology consisting of four fundamental sections. Initially, the environmental conditions on the surface of Mars are assessed and quantified as structural loads, so that the generative design tools effectively transform these stresses into design parameters that might be used in finite element modeling (FEM). Next, this study employs human factors derived from existing literature as input for Social Network Analysis (SNA) and the Label Propagation Algorithm (LPA) to address important design inquiries concerning functional zoning, layout configuration, geometry generation, and habitability variables. These inquiries aim to inform the decision-making process regarding autonomous typology design. Furthermore, the use of space syntax, physics simulations, and Voronoi algorithms improves the accuracy of the habitation planning process by generating floor designs and habitable volumes that align with the distinctive requirements and preferences of individuals. Lastly, the regolith habitation shell is constructed using structural simulation techniques that incorporate Mars' environmental pressures as design considerations. By employing Karamba3D and numerical finite element modeling (FEM) techniques, the structural performance of the regolith habitation shell under the environmental conditions on Mars is simulated.Consequently, this study introduces three distinct habitation shell designs that were developed and exposed to structural simulations to evaluate the effects of environmental stresses on Mars. The study explores the conjunction between generative design, data science, and structural simulations by employing a systematic and comprehensive design process. Its objective is to provide insights into the impact of environmental pressures on habitation shells and improve our understanding of design outcomes for future exploration on Mars.

Post-fire behaviour and resistances of square recycled aggregate concrete-filled stainless steel tube stub columns

Experimental and numerical studies on the cross-section compressive behaviour and residual resistances of square recycled aggregate concrete-filled stainless steel tube (RACFSST) stub columns after exposure to fire are reported in this paper. An experimental programme was firstly carried out on twelve stub column specimens with three recycled coarse aggregate replacement ratios (0%, 35% and 70%) after exposure to the ISO-834 standard fire for 0 min (i.e. at ambient temperature), 15 min, 30 min and 45 min. The test results, including load–end shortening curves, failure loads and failure modes, were presented, with the initial compressive stiffness and confinement effect analysed. The experimental programme was followed by a numerical modelling programme, where thermal and mechanical finite element models were developed and validated against the test results and afterwards used to conduct parametric studies to generate additional numerical data over a wide range of cross-section dimensions. Based on the test and numerical data, the relevant design rules for square natural aggregate concrete-filled carbon steel tube stub columns at ambient temperature, as specified in the European code, Australia/New Zealand standard and American specification, were evaluated, using post-fire material properties, for their applicability to square RACFSST stub columns after exposure to fire. The evaluation results generally revealed that the European code and Australian/New Zealand standard led to a good level of design accuracy, while the American specification resulted in slightly conservative post-fire cross-section compression resistance predictions.

Crushing analysis of square gradient hierarchical multicellular tubes

Inspired by tree fractals, a novel square gradient hierarchical multicellular tube (SGHMT) is proposed, and a finite element (FE) model of the structure is constructed using Abaqus/Explicit. The accuracy of the FE numerical model was verified using experiments, and the energy absorption characteristics of the structure under axial impact were analyzed. The results show that the high-level SGHMTs have higher energy absorption capacity and impact force efficiency (CFE) compared with the low-level SGHMTs for both the same wall thickness and the same mass, and crashworthiness is greatly improved. The energy absorption (EA) and CFE of SGHMT-3 are 11.39 and 4.47 times higher than those of SGHMT-0 under the same wall thickness condition, respectively. The EA and CFE of SGHMT-3 are 2.15 and 2.28 times higher than those of SGHMT-0, respectively, under the same mass condition. On this basis, further geometrical parameter analysis was carried out, and it was found that the structural parameters (wall thickness, hierarchy, and shape scale factor γ 1 , γ 2 ) had a significant effect on the crashworthiness of the square gradient hierarchical multicellular tubes. Finally, a comparative study with other multicellular tubes was carried out to demonstrate the superiority of the proposed square gradient hierarchical multicellular tubes compared with other multicellular tubes.

Empirical formula of buckle propagation pressure for sandwich pipes with polymer core material

The sandwich pipe, with its high hydraulic pressure resistance and thermal insulation properties, presents itself as a potential choice for deepwater oil and gas exploration. This study developed a 3D finite element numerical model using ABAQUS software to simulate the collapse propagation of sandwich pipes under the high external hydraulic pressure. A parametric analysis was undertaken using a numerical model, which had been calibrated by experimental tests. The study aimed to assess the contributions of material properties, such as yield strength and Young's modulus, as well as geometric dimension, to the collapse propagation behavior of the sandwich pipe. Moreover, a simplified empirical formula was formulated to research the propagation pressure of polymer sandwich pipes. The research also investigated the contribution of the interaction property between the core layer and inner/outer steel layer on the propagation pressure. An interfacial factor was incorporated into the present simplified empirical formula. The empirical formula was validated using experimental results and data from various sources, including real interlayer interactions observed during tests. The results indicate that this formula offers an accurate prediction of the propagation pressure for polymer sandwich pipes.

Mechanism analysis and optimal design of sound-absorbing metastructure constructed by slit-embedded Helmholtz resonators

<sec>Low-frequency noise has always been a thorny problem in the field of noise control. In recent years, the development of sound-absorbing metastructures has provided new ideas for controlling low-frequency noise. In this work, we propose a low-frequency sound-absorbing metastructure constructed by Helmholtz resonators with embedded slit. Analytical and numerical models are established to analyze the sound absorption performance and mechanism of the proposed sound-absorbing metastructure, and optimization design is conducted to achieve low-frequency wideband absorption performance. The analytical modeling method and the performance of the proposed sound-absorbing metastructure are also experimentally verified. The main conclusions are summarized as follows.</sec><sec>1) By using transfer matrix method and finite element method, analytical and numerical models for calculating sound absorption coefficient are established. It is shown that analytical predictions are in good agreement with numerical calculations. It is demonstrated that a typical design of a 30-mm-thick single-cell metastructure can achieve a sound absorption coefficient of 0.88 at 404 Hz. Typical designs of two-cell parallel structure and the four-cell parallel structure (both with a thickness of 50 mm) can achieve two and four nearly perfect low-frequency sound absorption peaks in a frequency band of 200–400 Hz, respectively.</sec><sec>2) The low-frequency sound absorption mechanisms of the proposed metastructures are explained from four aspects: simplified equivalent model parameters, normalized acoustic impedance, complex-plane zero/pole distribution, and sound pressure cloud image and particle velocity field distribution. It is demonstrated that the main sound absorption mechanism is related to the thermal viscous loss of sound waves, caused by the inner wall of embedded slit.</sec><sec>3) The design for broadband low-frequency absorption performance is optimized by using differential evolution optimization algorithm. An optimized parallel-multi-cell coupled metastructure with multiple perfect sound absorption peaks below 500 Hz is realized. For a thickness of 90 mm, the sound absorption coefficient curve of an optimized metastructure exhibits 8 almost perfect sound absorption peaks and an average sound absorption coefficient of 0.86 in a frequency range of 170－380 Hz.</sec><sec>4) Experimental samples are fabricated to test sound absorption. Experimental results are basically consistent with the analytical predictions. The results from analytical model, numerical calculations and experimental measurements are mutually verified.</sec><sec>In summary, the sound-absorbing metastructures with a thickness of sub-wavelength, proposed in this work, exhibit outstanding sound absorption performance at low frequencies. We demonstrate that they are suitable for low frequency broadband sound absorption below 500 Hz. Owing to their thin thickness and relatively simple construction, they have broad application prospects in practical noise control engineering.</sec>

Numerička analiza procesa penetracije pancirnog potkalibarnog projektila kalibra 30 mm

Introduction/purpose: In recent times, with the tendency to develop new types of armor-piercing ammunition, constant investments in the development of new types of armored obstacles is necessary. Obstacles made of high-alloy steel plates are still the best form of protection against larger caliber ammunition. There are a number of factors to consider when selecting an alloy, including the weight, dimensions, intended use, desired ballistic performance, and costs. According to that, a numerical analysis of penetration of a 30mm armor-piercing fin-stabilized discarding sabot projectile into the steel alloy Weldox 460 plates of different thicknesses at a distance of 1000m with a velocity of 1300m/s is presented in this paper. Methods: The stresses and deformations of the penetration effect were calculated through numerical analysis and finite element modeling. To specify material characteristics, the Johnson-Cook material model and the fracture of materials model have been utilized. In order to define models and carry out numerical calculations, the software packages FEMAP and LS Dyna have been used in this paper. Results: For a numerical analysis of the penetration process of this projectile type against armor obstacle, four different armor plate thicknesses are calculated: 10mm, 50mm, 100mm, and 110mm. For each of them, the results are shown in a form of stress and displacement, so that the interaction phenomena between the sub-projectile and the armor plate can be described. Conclusion: Modeling the impact on armor-piercing obstacles is extremely difficult, time-consuming, and complex, and the resulting models very successfully (or with some deviation) approximate the real problem of projectile penetration. One of the most effective methods for solving problems of this kind and others of a similar nature in recent times is the finite element method analysis. The material and the target dimensions, as well as the ballistic parameters and the material of the projectile have the biggest influence on projectile penetration. The target's resistance to penetration increases when all input parameters are maintained at the same level and its thickness is increased, and vice versa.

The effect of RAP content on fatigue damage property of hot reclaimed asphalt mixtures.

The fatigue property of the recycled mixture affects the structural design of recycled pavement. In order to explore the effect of different reclaimed asphalt pavement (RAP) content on the fatigue properties of recycled mixtures, the fatigue properties of recycled mixtures were analyzed through an indoor fatigue test and finite element numerical simulation. Based on the phenomenological method and the dissipated energy theory, the fatigue properties of recycled mixtures with different RAP contents were analyzed and the fatigue damage of the mixtures were also studies under various strain levels. Based on the finite element numerical model of fatigue damage, the stress distribution and internal damage field distribution of trabecular specimens under different temperatures, strain levels and RAP contents were analyzed. The results showed that the anti-fatigue level of the mixture decreased as the RAP content was increased. The relative change rate of dissipated energy for different types of mixtures showed a two-stage change rule with the change of load times, that is, the value is large and decreasing, and the value is small and stable. The correlation between the plateau value (PV) and the fatigue life was established under the double logarithm coordinates, which could better analyze the influence law of the RAP content on the fatigue performance of the recycled mixture. Under different temperatures, strain levels, and RAP contents, the stress at the bottom of trabecular specimen and the overall damage field were mainly generated at the upper part under compressive stress and the bottom under tensile stress, and the damage field distribution area accounted for a small part of the whole specimen. According to the test results and fatigue damage distribution, it is recommended that the content of recycled aggregate in recycled asphalt mixtures be less than 30% to ensure good performance. The research results have important practical significance for the improvement of fatigue performance and engineering application of recycled mixtures.

Экспериментальная оценка адекватности численного моделирования межслоевой трещиностойкости слоистого стеклоэпоксикомпозита при комбинированной моде нагружения I/II

The reliability of numerical simulation of crack growth in a laminate glass-epoxy composite under mixed-mode loading by opening (mode I) and shear (mode II) of an interlayer crack is verified. According to the experimentally determined standard (DCB and ENF) and nonstandard (SLB and OLB) methods, the values of the parameters of interlayer crack resistance under individual and mixed-mode loading modes I and II calculated the exponent in the Benzeggagh-Kenane equation as a material constant of the laminate epoxy glass composite. Using this parameter and the ANSYS software package, within the framework of linear elastic fracture mechanics and the method of virtual crack closure, numerical finite element modeling of the growth of interlayer cracks in samples of a laminate glass-epoxy composite of the SLB and OLB types was carried out under a mixed-mode loading with a different fraction of modes. With the optimal number of elements in the finite element mesh per given length of the crack growth trajectory, numerical simulation provides sufficient accuracy of calculations of the limit load of the beginning of crack growth with a minimum amount of calculations and good agreement between the experimentally determined and calculated crack resistance parameters.

The Material Heterogeneity Effect on the Local Resistance of Pultruded GFRP Columns.

Pultruded GFRP (glass fiber-reinforced polymer) materials are widely used in structural engineering because of their lightweight, corrosion immunity, and electromagnetic transparency. However, the design of load-bearing components facing substantial compressive stresses, e.g., columns, must be more stringent than steel structures due to excessive deformability, material heterogeneity, and vulnerability to stress concentration. This manuscript investigates the failure performance of locally produced GFRP materials, focusing on the material heterogeneity effect on the mechanical resistance of a support joint of a pultruded tubular GFRP column. This experimental campaign employs relatively short rectangular profile fragments to isolate the support behavior and verify a simplified numerical finite element model, which neglects the nonlinearity of GFRP material. This work determines the material failure mechanisms behind the mechanical performance of pultruded profiles subjected to longitudinal compression for various column lengths.

Investigation of rail damage considering impact at a welded joint under wet condition

PurposeThe purpose of this study is to develop a transient wheel–rail rolling contact model to primarily investigate the rail damage under wet condition when the train passes through the welded joints.Design/methodology/approachThe impact force induced by welded joints is obtained through vehicle–track coupling dynamics. The normal and tangential wheel–rail contact pressures were solved by elastohydrodynamic lubrication (EHL) theory and simplified third-body layer theory, respectively. Then, the obtained tangential pressure and normal pressure were applied to the finite element model as moving loads, simulating cyclic loading. Finally, the shakedown map and critical plane method were used to predict rolling contact fatigue (RCF) and the initiation of fatigue cracks.FindingsThe results indicate that RCF will occur and fatigue cracks are more prone to appear on the subsurface of the rail, specifically around 2.7 mm below the rail surface in the vicinity of the welded joint and its heat-affected zone.Originality/valueThe cosimulation of numerical model and finite element model was implemented. The influence of surface roughness and fluids was considered. In this model, the normal and tangential wheel–rail contact pressure, the stress and strain and the rail fatigue cracks were obtained under a rail-welded joint excitation.

PERSPECTIVES AND SPECIFIC FEATURES OF THE USE OF COMPOSITE MATERIALS FOR STRENGTHENING OF DAMAGED REINFORCED CONCRETE STRUCTURES

The need for strengthening of existing structures has recently become topical. Composite materials due to their remarkable properties, possibility to adaptation to the design requirements and facilitation of restoration measures are widely used for strengthening. This article is focused on review of restoration approaches with the use of composite materials and specific features of their behavior under various impacts. Study includes analysis of recent studies in the area, identifying gaps of knowledge and perspectives for further research. The most relevant areas of research were distinguished including numerical finite element modelling for parametric analysis, deepening of understanding of composites` linearly elastic behavior, approaches to prevent delamination failure. Further thorough research in this area is strongly recommended to deepen the knowledge and maximize the efficiency of use of composite strengthening systems.

Performance of Reinforced Concrete Flat Slabs Having GFRP Gratings

A thorough study of the literature indicated that there is not much relevant research on the application of GFRP gratings. Otherwise, extensive study has been done on FRP bars, laminates, sheets, strips, and rods. This study proposes a novel approach to improve the punching shear resistance of flat slab column connections by inserting GFRP gratings across the slab thickness. The results of seven specimens tested under vertical static loading are presented, considering the influence of the grating’s characteristics. All specimens were tested as simply supported slabs under one point of static loading. Experimental results, including crack patterns, slab deflection, concrete compressive strain, tensile steel strain, GFRP grating strain, and failure load, were recorded using extensive electric instrumentation. Test results revealed an enhancement in the failure load ranging between 9.03% and 27.67% for the specimens provided with the GFRP grating. In addition, a nonlinear finite element numerical model analysis was carried out using the ANSYS 15 program. Correlational studies based on the load-deflection response and crack patterns were utilized, resulting in a good agreement between numerical simulations and experimental results with differences ranging from 1.0% to 8.0%.

Random fatigue life prediction of composite components for double-wishbone suspension considering an improved crack propagation model

To predict the fatigue life of composite structures more accurately under random loads, some parameters are introduced, such as threshold value, elastic modulus, and fracture toughness. The overload hysteresis effect under random loads is considered to improve the crack growth rate model and obtain a random fatigue life prediction model. Taking the key components of the double-wishbone suspension as the research object, the random life prediction model for the key components was established, and the fatigue life test bench was built. By comparing and analyzing the numerical fatigue life, finite element simulation life, and physical test life, the effectiveness of numerical model and finite element model is illustrated.

Inversion study on elastic–plastic material parameters of red sandstone in uniaxial compression test

In order to obtain the real material parameters of heterogeneous rock, the material parameters of red sandstone specimens under uniaxial compression tests are inverted based on the Digital Image Correlation (DIC) method and the Finite Element Model Updating (FEMU) method. The DIC method is employed to calculate the displacement field of red sandstone specimens during uniaxial compression loading. Concurrently, a uniaxial compression elastic–plastic finite element numerical model with non-uniform material parameters is developed based on the FEMU method. The model adopts the Mohr–Coulomb yield criterion and adjusts the boundary conditions in real-time to maintain consistency with the test. The vertical displacement field of the numerical model is juxtaposed with that of the test to construct the objective function. Optimization is achieved using the Artificial Fish Swarm algorithm, which enables the acquisition of the non-uniform distribution and evolution process of the material parameters of specimens at different loading moments. The results indicate that this method can spatially obtain the non-uniform distribution field of material parameters and temporally track the evolution of material parameters during the loading process. This research lays a solid foundation for enhancing the accuracy of intelligent coal mining and dynamic disaster monitoring and early warning in coal mines.

O.I.C.-based design of extruded and welded aluminum I-sections

Current standards rely on simplified approaches to predict the resistance of aluminum structural elements that can be shown to inadequately account for the effects of strain hardening, instabilities, and heat reduced properties. This paper summarizes investigations towards the development of an alternative design method for aluminum open cross-sections, based on the Overall Interaction Concept (O.I.C.). This innovative design approach relies on the interaction between resistance and stability, and also allows to consider geometrical and material imperfections. Moreover, it allows to obtain direct, precise and consistent resistance predictions using continuous buckling curves.A numerical finite element model was developed to accurately predict the resistance of aluminum cross-sections. Its efficiency was validated by comparing its numerical predictions of resistance to available experimental test data. Extensive parametric studies were then conducted, allowing to study the impact of varying geometries, aluminium alloys and load cases on the resistance. Using the results from more than 2300 numerical simulations, O.I.C.-type design proposals were formulated for the local resistance of extruded and welded aluminum sections.The performance of the design equations was evaluated by comparing their resistance estimates to the reference numerical results and to resistance predictions from the Canadian, European, and American aluminum design standards. The comparisons showed that the O.I.C. design proposal leads to much more accurate and consistent results than these standards, while remaining simpler and more efficient.

A New Method to Evaluate Pressure Distribution Using a 3D-Printed C2-C3 Cervical Spine Model with an Embedded Sensor Array

Cervical degenerative disc diseases such as myelopathy and radiculopathy often require conventional treatments like artificial cervical disc replacement or anterior cervical discectomy and fusion (ACDF). When designing a medical device, like the stand-alone cage, there are many design inputs to consider. However, the precise biomechanics of the force between the vertebrae and implanted devices under certain conditions require further investigation. In this study, a new method was developed to evaluate the pressure between the vertebrae and implanted devices by embedding a sensor array into a 3D-printed C2-C3 cervical spine. The 3D-printed cervical spine model was subjected to a range of axial loads while under flexion, extension, bending and compression conditions. Cables were used for the application of a preload and a robotic arm was used to recreate the natural spine motions (flexion, extension, and bending). To verify and predict the total pressure between the vertebrae and the implanted devices, a 3D finite element (FE) numerical mathematical model was developed. A preload was represented by applying 22 N of force on each of the anterior tubercles for the C2 vertebra. The results of this study suggest that the sensor is useful in identifying static pressure. The pressure with the robot arm was verified from the FE results under all conditions. This study indicates that the sensor array has promising potential to reduce the trial and error with implants for various surgical procedures, including multi-level artificial cervical disk replacement and ACDF, which may help clinicians to reduce pain, suffering, and costly follow-up procedures.

Numerical analysis of the effect of trench on indoor vibration adjacent to railway ground line

By establishing a 3D finite element numerical simulation analysis model of railway-soil-trench-building, the accuracy of the simulation analysis model is verified using on-site measured data of surface vibration attenuation law. Install vibration isolation trenches with different depths at different locations between the building and the railway, and analyze and compare the impact of indoor vibration in different situations. The results indicate that; The surface vibration caused by railways attenuates rapidly around 30m~76m from the line, and then shows a slight amplification trend around 120m. The surface vibration near the railway is mainly concentrated in the range of 15-90Hz; The vibration reduction effect of trench on different indoor rooms in buildings varies greatly. By optimizing the parameters of trench, the average indoor vibration reduction effect can be close to 5dB, and the vibration reduction effect of trench at different positions varies greatly. The increase in trench from 6m to 12m increases the indoor vibration isolation effect.

Study on the Influence of Steel Fiber Distribution on the Mechanical Properties of Perfobond Leiste (PBL) Shear Connectors

In order to study the influence of steel fibers on the mechanical properties of Perfobond Leiste (PBL) shear connectors and improve the utilization of steel fibers in this structure, four push-out test specimens and eight finite element numerical models were produced to study PBL-type shear connector specimens with different steel fiber blending amounts and blending forms. The results show that in this structure, when the blending amount of steel fiber was 0.5% to 1.5%, the ultimate bearing capacity of the specimen improved linearly, and the steel fiber helped to give full play to the performance of the PBL shear connector. The steel fibers distributed in the Z-direction have a significant impact on the mechanical properties of the PBL shear connector, and the steel fibers distributed in this direction have a significant effect on increasing the ultimate bearing capacity of the specimen. Steel fibers distributed in the Y-direction can greatly improve the plasticity of concrete. In addition, the effective action area of steel fibers is the triangular area from the bottom of the PBL shear connector to the two tops of the concrete.

An automated computation method for flexible protection systems based on neural networks

An automated computation method is proposed in this paper to address the problems of enormous computational difficulty and low efficiency in flexible protection systems. This method uses neural networks to demonstrate the complex nonlinear mapping relationships between the system’s specifications and performance. Use the finite element numerical simulation model validated by a full-scale impact test on the 750 kJ passive flexible protection system for massive parametric analysis, and extract the critical computation results as the label space. Conducted mechanical tests on critical components, analyzed the mechanical characteristics of each component, and extracted training features to form a sample space. The label space and sample space formed a dataset containing 1828 sets of data and used 1700 sets of data to train a neural network while using the remaining 128 sets of data to test. The maximum predicted error was 8.33 %, and the maximum average error was 3.73 % from the test. The proposed method can complete the computation in just 6 s, with a computation speed of 520 times that of the fastest finite element method, significantly improving the computation efficiency of the flexible protection system and reducing the computational difficulty.