Numerical Finite Element Analysis Research Articles

A machine-learning-based model for seismic performance assessment of interior slab-column connections

Slab-column connections are the most critical components in flat plate systems under seismic actions due to their brittle failure mode. Finite element analysis (FEA) can be adopted as an extension of experimental testing to potentially lead to the development of modern design codes by providing significant information on the punching shear failure process of connections. However, the available concrete constitutive models in FEA packages fail in simulating the hysteretic response of the connections under cyclic loads. Moreover, it is shown that the available design code recommendations and empirical models are not accurate tools for assessing the seismic performance of these connections (e.g., unbalanced moment and/or drift capacity). In an effort to overcome these limitations, a dataset of previously tested experiments is compiled to predict the ultimate load and drift of the connections using the multi-variate non-linear regression model. Additionally, there is a need to develop a new constitutive material model for seismic performance assessment of the connections to capture the complete hysteretic response of the connection using numerical FEA. Consequently, a deep neural network is trained over the accumulated dataset and integrated into the OpenSees source code to determine the seismic performance of the connections. For data augmentation, a generative neural network model of autoencoders known as Generative Adversarial Networks (GANs) is constructed to generate synthetic data. The proposed material model is found to have significantly improved precision in capturing the hysteretic response of flat plates. The developed models showed higher accuracy than the design code estimations and empirical models.

Acoustic and Fracture Energy Correlation in Mode I Fracture with Concrete Damage Plasticity Model and Three-Point Bend Experiment

The progressive damage monitoring and fracture evaluation of plain concrete beam specimens subjected to three-point bending (TPB) are reported in this paper. The objective of the present research is to systematically correlate the fracture behavior of a concrete beam with acoustic emission (AE) data recorded during the present set of experiments. The damage growth and failure mechanisms of the beam specimens are investigated with AE parametric analysis, b-value analysis, and digital image correlation method. Eventually, a reasonable correlation between AE energy and the released fracture energy is established at various stages of loading, which is confirmed with the set of TPB beam experiments and further validated with nonlinear numerical finite-element analysis. The energy released during the cracking processes at different loading stages in the experiment is quantified and systematically analyzed. Acoustic and fracture energies are dependent on active concrete cracking, and their correlation is helpful in determining the extent of damage in the concrete structures. Such a relationship can be used as an operational tool for structural health monitoring of structures as an early warning system supplemented with numerical analysis, a well-calibrated laboratory, and in situ AE experiments.

Study on meshing performance of a novel point-contact hourglass worm drive based on modified involute

In this paper, a novel point-contact hourglass worm drive based on modified involute is proposed, it is composed of a modified involute gear and an hourglass worm enveloped by a standard involute gear. The involute modification method and criterion of the standard involute gear are proposed, four representative modification functions are established, and the mathematical model of this novel transmission pair is derived. The tooth contact analysis (TCA) is simulated by numerical analysis and finite element analysis (FEA); the effect of the modification position and modification amount on the contact stress is studied by transient structural analysis; the error sensitivity to center distance error, shaft angle error, and comprehensive error was studied by FEA. All these results of the analysis demonstrated that the tangible contact areas are in line with the theoretical contact points, the average stress value and variance are less affected by the modification position, and the novel worm pair has good error adaptability. This study aims to provide a new idea for the configuration of an hourglass worm drive with local conjugate meshing.

Numerical Simulation and Analysis of a Vertical Centrifuge

In order to solve the separation efficiency problem of the vertical centrifuge. First, understand the working principle and dynamic theory of the centrifuge, preliminarily design the technical parameters from the experience and experimental data of the prototype, solid works model, specify the overall structure scheme, and complete the virtual assembly. Secondly, the work performance is verified. The production capacity is calculated with power to meet the design requirements. Then, to verify the design strength and deformation meet the design requirements. Then, the finite element numerical analysis of the internal flow field. The FLUENT software is used to analyze the internal flow field velocity distribution and the turbulent kinetic energy of the centrifuge. Finally, a solid phase distribution rule analysis was performed to investigate the effect of particle diameter size on the separation performance at a suitable particle volume fraction.

Analysis of the effects of vertical joints on the stability of loess slope

Vertical joints with different lengths and slope distances (the horizontal distance from joints to slope shoulder) are generated at the top of the loess slope because of the unloading and collapsibility of the loess. The existence of vertical joints is a significant risk factor for loess landslides. This paper applies three methods, including laboratory tests, numerical simulation and theoretical analysis, to analyze the influence of vertical joints on the stability of loess slope. Firstly, the typical failure mode and strength characteristics of the samples containing vertical joints are analyzed through the unconfined compressive strength test and triaxial compression test. Further, the effects of vertical joints with different lengths and the slope distance on the slope safety coefficient and sliding surface position are calculated by finite element numerical analysis. Finally, the formula for calculating the safety coefficient of loess slope with vertical joints is derived. The results show that: the joint bonding degree affects the sample's strength and failure rate. The strength of the sample with open vertical joints is less than that of closed ones, and the failure rate is greater than that of closed ones. When the length and the slope distances of the vertical joint are less than 5 m, the influence of vertical joints on the shape and position of the sliding surface will be small. When the length of the vertical joint is more than 5 m and less than 15 m, the safety factor of the slope decreases with the increase in the length of vertical joints. When the length of vertical joints reaches 15 m, and the slope distance is 10 m, the deterioration degree of vertical joints on the slope comes up to the peak. Statistical analysis shows that the dominant dip angle of shear fracture at the back edge of the landslide affected by the vertical joint surface is between 45° and 65°. The research results can be used for rapid calculation of the safety coefficient and rapid evaluation of slope stability of loess slope with vertical joints.

Evaluation of the dynamic response for scaled models of shaped concrete floor slabs

The dynamic response of building structures is an essential design consideration in building acoustics. However, building design is increasingly driven by sustainability goals. Floors can be optimized to reduce material consumption and corresponding carbon emissions, yet geometric changes may cause sound insulation and vibration problems. Although the dynamic performance of traditional floors is well established, the performance of non-traditional shapes is less understood. Before trusting the results of building simulations encompassing optimized floors, the dynamic results should first be validated experimentally. This paper details a numerical finite element analysis method to ascertain the dynamic response of four shaped concrete slabs, with experimental modal analysis used to validate the numerical results. The material properties in the numerical model are updated to match the experimental results. The findings support a computational framework for determining the dynamic response of shaped structures that can then be implemented in future large-scale building models.

Effect of infilled CLT shear walls on the lateral performance of glued-laminated timber frames: Experimental and numerical analysis

A new timber structural system about the combination of cross-laminated timber (CLT) and glued-laminated timber (GLT) aiming to improve the timber lateral performance and satisfy the seismic demands has recently been proposed, highlighting the important influence on the design of timber frame-shear walls structure. This paper presents the lateral behaviour and seismic performance of GLT frame infilled with CLT shear walls by experimental and finite element numerical analysis. Four specimens of 1:1.5 scale including one bare GLT frame and three GLT frames infilled with CLT shear walls were designed to research the lateral performance under the cyclic loading tests. The mechanical characteristics of these specimens were effectively evaluated in the form of theoretical derivation under the lateral load, and the theoretical models of the beam-column joint and the column-base joint were established. Based on the theoretical calculation methods, the finite element models of four specimens were established and analyzed by Abaqus software to research the lateral performance of the influence of CLT shear walls on the GLT frame. The results indicate that the lateral deformation of the bare GLT frame is obvious, the shear cracks emerge in the joints, and the damage degree of the beam end of the beam-column joint is significantly greater than that of the column-base joint. The lateral load-bearing capacity of the GLT frame is improved after being infilled with CLT shear walls, and the damage degree of GLT frame joints is significantly improved. The elastic lateral stiffness of GLT frame infilled CLT shear walls with the opening can reach 9.66–13.1 times higher than that of bare GLT frame according to the test results. From the beginning of loading to the failure stage, the lateral load of specimens provided by the CLT shear wall is more than 50 %, and the contribution of the CLT shear wall to the lateral performance of the structure is significant in collaborative work. The numerical analysis based on the FE models of GLT frame infilled with CLT shear wall shows that the opening type, size and thickness height ratio of the CLT wall are obvious effects on the lateral resistance of the structure. The lateral load-bearing capacity increase by about 95.06–127.5 % when the thickness of the CLT shear wall of three-layers wood panels increases from 30 mm to 105 mm. The lateral resistance increases by 49.29–72.29 %, and the lateral stiffness increases by 48.26 % when the thickness of the CLT shear wall of five-layers wood panels increases from 50 mm to 150 mm. The research shows that CLT can increase the lateral load-bearing capacity and stiffness of structures, which can satisfy the demands of better lateral performance and sustainable buildings with a low carbon cycle.

Field quality and surface resistance studies of a superconducting REBa2Cu3O7−x —Cu hybrid coating for the FCC beam screen

To ensure beam stability in the future circular collider study of the European Organization for Nuclear Research, RE(=Y, Gd, Eu)Ba2Cu3O 7−x high-temperature superconductor was proposed as a low-surface impedance coating for its beam screen. Unfortunately, persistent currents in the superconductor will degrade the magnetic field homogeneity inside the beam chamber, endangering the stability of the beam trajectory. To counteract this effect, we have explored the possibility of using a highly conductive hybrid coating made of Cu and REBa2Cu3O 7−x . This decreases the surface impedance when compared to that of pure copper, while maintaining high magnetic field quality inside the beam screen chamber. This work formulates guidelines for hybrid coating geometries to comply with the field quality criterion of a circular accelerator during operation with dipole magnets by means of finite elements numerical analysis. We produced hybrid coating samples with compliant geometries via photolithography. Scanning Hall microscopy and radio-frequency characterization have given the first experimental confirmation that these hybrid coatings offer high field quality and present a surface resistance lower than that of copper for the beam screen of the future circular hadron collider. The excellent agreement shown between experimental results and simulations validates that the numerical analysis performed throughout this work can be used as a prediction tool for future proposed geometries.

Study on Defect Evolution of Steel Strip under High-speed Cold Rolling

In this paper the strain rate effect of the material was quantitatively tested by INSTRON tensile testing machine and Zwick/Roell HTM5020 high-speed tensile testing machine. The dimple size of the fracture surface of the tensile specimen was determined and analyzed by using the scanning electron microscope. Based on the Cowper-Symonds constitutive model, the parameters in the dynamic constitutive model and the true stress-strain curve under quasi-static condition were obtained by combining the results of quasi-static and dynamic tensile tests and the finite element numerical analyses. Considering the strain rate effect of the material the effects of cold rolling speed on the evolution of different types of defects were analyzed by the ANSYS/LS-DYNA dynamics code. The results show that with the increasing of crack length and decreasing of crack width, the critical rolling speed decreases. But if the crack length is less than 5 mm and the aspect ratio of crack length to crack width is larger than 5, the critical rolling speed of crack growth can be much large.

Analysis of high frequency noise sources on air conditioning variable speed compressors

The improvement on energy consumption requires application of new technologies in existing products. On the past decades, optimization of power consumption on variable speed rotary compressors for air conditioning applications was achieved by replacing induction motors to brushless DC (BLDC) motors driven by a frequency inversor. Besides the positive behavior of the motor type change on compressor efficiency, acoustic problems on the compressor became more complex. This article makes a revision of the main noise generation mechanism by BLDC motors of an air conditioning compressor via numerical finite element and experimental analysis aiming a noise reduction on a tonal component around 8 kHz band. Results indicate harmonic components on the forces exciting some specific resonance frequencies of the stator. The harmonic components show up in the force signals via pulse width modulation of the inverter electronic controller. The structure-born noise is radiated through the compressor shell. Among the possibilities to mitigate the noise issues, it was chosen to optimize the electronic control reduced the excitation levels of the stator and the tonal component of 8 kHz band in about 10 dB improving the sound quality of the compressor.

Experimental and Numerical Investigation of an Innovative 3DPC Thin-Shell Structure

The development and application of new Fiber Reinforced Polymer (FRP) material and 3D printing construction technology provide a basis for making up for the shortcomings of traditional thin-shell structures and building new thin-shell structures with better performance. In this paper, a new 3D Printing Composite (3DPC) thin-shell structure is proposed, which is prepared using a FRP plate as a permanent base mold and combining it with 3D printing cement technology. Both the typical experiment and finite element numerical simulation analysis of the 3DPC thin-shell structure are carried out. The results show that the maximum load capacity of the 3DPC thin-shell structure is increased by 53.3% as compared with the corresponding traditional concrete thin-shell structure. The presence of the FRP sheet effectively delays the generation of initial cracks and enhances the ductility of components.

Seismic Response Analysis of Rock-Socketed Piles in Karst Areas under Vertical Loads

Karst landforms constitute one of the most harmful geological conditions, which have an adverse effect on the deep foundation structures of bridges. During earthquakes, the existence of karst caves can cause serious seismic damage to the bridge pile foundation. In order to investigate the seismic response of rock-socketed piles under vertical loads in complex karst cave conditions, finite element numerical simulation analyses were carried out, referring to the practical major bridge structure rock-socketed pile project in China. The peak strain distributions of rock-socketed pile foundation influenced by single-karst cave factors under the combined action of vertical loads and ground motions were investigated, and the influences of complex multi-caves were further explored. The results showed that the restraint effect of the bedrock near the pile would gradually decrease with the increase of the height of the karst cave and the decrease of the height of the karst cave roof; under the condition of a beaded karst cave, the constraint of bedrock between the karst caves makes the pile present the distribution characteristics of “multi-segment and multi-broken line”; under the condition of an underlying karst cave, the existence of the underlying karst cave would decrease the restraint of the bedrock at the bottom pile and increase the peak strain of the pile to a certain extent. This paper revealed the seismic response law of the rock-socketed pile under vertical loads within various complex karst cave conditions and developed reasonable reinforcement measures aiming at dangerous locations, providing important engineering guidance and a reference for the seismic design of rock-socketed pile foundation in complex karst areas.

Subgrade reaction for closely spaced raft and isolated foundations on sand: case study

This paper investigates the interference effect of closely spaced foundations on the modulus of subgrade reaction (k) and provides an insight into some of the factors affecting the k-value of a raft foundation when other foundations (isolated footings or other identical rafts) are closely placed on both sides. The investigation adopted a three-dimensional, non-linear, finite-element numerical analysis based on a case study of a residential project with several multi-storey buildings constructed on sand underlain by weathered limestone. A site-specific ground investigation was conducted to determine soil properties, which were used to construct three-dimensional numerical models to simulate different arrangements of foundations and estimate the corresponding k-values. The results show that the k-value starts to decrease when the spacing between the foundations becomes less than three times the raft width, and the percentage of reduction in k-value increases in a non-linear way as the spacing decreases further. In addition to spacing, the study revealed that the effect of adjacent foundations depends on their size and the magnitude of their applied pressure. The case study provides a framework for developing a correction factor that can be applied to k-value for improving the structural and geotechnical design of closely spaced shallow foundations.

Energy trapping in a phononic crystal cavity enhanced by nonreciprocal acoustic wave transmission

Defect mode induced energy trapping at the bandgap frequency of a phononic crystal has been widely explored. Unlike this extensively used mechanism, this work reports the use of nonreciprocity in the transmission band to trap energy inside a phononic crystal cavity. Passive nonreciprocity is due to natural viscosity of the background liquid (water) and asymmetry of aluminum scatterers. The level of non-resonant energy trapping was compared for three cavities with different symmetry. Enhancement of energy trapping at a frequency of 624 kHz was observed experimentally for the cavity where nonreciprocity suppresses acoustic radiation into environment. Experimental results were further investigated and confirmed using finite element numerical analysis.

Static Behavior of a Prosthetic Running Blade Made from Alloys and Carbon Fiber

Prosthetic running blades offer a solution for individuals with disabilities to engage in sports, benefiting them both psychologically and physiologically. Furthermore, a good prosthetic running blade in terms of performance and cost is rarely available to all disabled persons. In this study, we have examined how various materials impact the static behavior of the prosthetic running blade. A finite element numerical analysis was conducted on a prosthetic design to investigate this effect. We have used different materials for investigation such as aluminum alloy (2024 T4), stainless steel (AISI 316), carbon fiber, and titanium alloy (grade 5), under different load conditions. The load conditions have been varied mainly to three conditions, namely, rest (700 N), walking (1400 N), and running (2100 N). In our experimental design, we studied total deformation, equivalent stress, and strain energy to understand the performance based on material choice. It was noticed that the aluminum alloy (2024 T4) blade goes under much deformation when compared to titanium- and carbon fiber-made running blades. The least amount of overall deformation occurs in carbon fiber under varying load conditions. Carbon fiber appears to be the most profitable option due to its lowest cost per running blade. Titanium alloy grade 5, carbon fiber, AISI 316 stainless steel, and aluminum 2024 T4 alloy cost a total of 78.1, 48.5, 67.6, and 20.9 USD, respectively. It is evident that titanium alloy materials carry a higher price compared to alternative materials.

Spiral-based confinement in slabs for the seismic performance enhancement of steel-concrete composite frames

The seismic performance analysis of steel-concrete composite frames involves, as known, the interaction of several load-bearing components that should be properly designed, with multiple geometrical and mechanical parameters to account. Practical recommendations are given by the Eurocode 8 – Annex C for the optimal detailing of transversal rebars, so as to ensure the activation of conventional resisting mechanisms. In this paper, the attention is focused on the analysis of effects and benefits due to a novel confinement solution for the reinforced concrete (RC) slab. The intervention is based on the use of diagonal steel spirals, that are expected to enforce the improve the overall compressive response of the RC slab, thanks to the activation of an optimized strut-and-tie resisting mechanism. The final expectation is to first increase the resistance capacity of the slab, that can thus transfer higher compressive actions under seismic loads. Further, as shown, the same resisting mechanism can be beneficial for the yielding of steel rebars, depending on the final detailing of components, and thus possibly improve the ductility of the system To this aim, a refined Finite Element (FE) numerical analysis is carried out for several configurations of technical interest. The in-plane compressive behaviour and the activation of resisting mechanisms is explored for several spiral-confined slabs, based on various arrangements. Major advantage is take from literature experimental data on RC slabs, that are further investigated by introducing the examined confinement technique. As shown, once the spirals are optimally placed into the slab, the strength and ductility parameters of the concrete struts can be efficiently improved, with marked benefits for the overall resisting mechanisms of the slab, and thus for steelcomposite frames as a whole.

2D and 3D numerical investigation on contact stress behaviour on different combinations of gear pair

Polyamide (PA6) polymer gear tremendously expanded its usage in power transmission applications. PA6 gear were engaged with different combinations of gear pairs (STEEL – PA6, PA6 – STEEL, and PA6 – PA6) were utilized in those applications. Normally gears are subjected to Hertzian contact stress due to their non-conformal contact and ANSYS is one of the widely used Finite Element Analysis (FEA) tool to determine the contact stress behaviour of those gears. Even though numerous 2D and 3D FEA investigation were performed to determine the gear contact stress behaviour, the occurrence of surface and subsurface stresses for different combination of gear pair was not explored especially for PA6 gears. Thus, the work attempted to study the surface and subsurface contact stress behaviour of three combination of gear pairs (STEEL – PA6, PA6 – STEEL, and PA6 – PA6) using 2D (plane stress with thickness condition) and 3D FE analysis (ANSYS APDL). The optimum mesh sizes were selected from the convergence study and further simulations were performed. From the analysis, the stress was observed maximum at the contact pitch point for 2D analysis, whereas, 3D analysis showed the maximum stress at a depth below the contact surface (subsurface stress) for all the combinations of gear pairs. Different trend pattern was obtained between the stress plot of 2D (surface stress) and 3D (subsurface stress) analysis for all the gear pairs. The variation in depth occurrence of maximum stress was observed for Steel-PA6 (0.16 mm depth), PA6-Steel (0.16 mm depth) and PA6-PA6 (0.25 mm depth) gear pairs. And, the Polymer – Polymer (PA6-PA6) gear pair exhibited higher depth occurrence compared to Steel – PA6 and PA6 – Steel gear pairs.

Research on optimization strategy of transformer economic operation mode considering digital twin technology

Considering the overall environment of the power field, power transformer is one of the most important energy consuming devices in the substation, and the digital analysis technology of power transformer carbon footprint has become one of the hot issues. Taking a certain brand power transformer as an example, the no-load loss, load loss and stray loss of power transformer under different load conditions are calculated and analyzed by using electromagnetic finite element numerical analysis method, and then the digital twin model of power transformer is built. Combined with the digital twin model of power transformer, the carbon footprint of transformer is analyzed. Finally, the economic load coefficient of transformer is determined, and the optimal economic operation mode of substation is established. This method can provide a scientific basis for the construction of digital, low-carbon and energy-saving substations, while meeting the optimal efficiency and the fastest solution.

STRENGTH OF SHS COLUMN TO BEAM CONNECTIONS WITH HOLES FOR HOT DIP GALVANIZING IN THROUGH DIAPHRAGMS

When hot-dip galvanizing a square hollow section column, it is necessary to provide holes in the diaphragms. These holes affect the local rigidity and local strength of the beam to column connections. It requires local strength evaluation formulae to properly design the hole diameter and the plate thickness of the diaphragms. In this paper, the behavior of the connections and the failure mode is examined by loading tests. The shortage of test parameters is supplemented by performing finite element numerical analysis. Evaluation formulas for local yield strength and local ultimate strength are proposed based on limit analysis.

MODIFICATION OF THE LEMAITRE DAMAGE MODEL BY A LOCAL MULTIAXIAL STRESS STATE FUNCTION

A modification of the Lemaitre damage model is proposed based on the introduction of a function sensitive to the Lode parameter. The modified model is imported into the ANSYS software as a dynamically linked custom tag library. The model takes into account isotropic hardening based on the exponential Voice model and kinematic hardening based on the Armstrong–Frederick model. Limit state curves are obtained by numerical finite element analysis for three types of experimental cylindrical specimens: a compression specimen under additional external pressure, a circular-notch specimen under uniaxial tension, and a hollow cylindrical specimen under combined tension, torsion, and internal pressure. The advantages and disadvantages of the proposed model are considered. Recommendations are given for choosing model parameters to predict limit states under multiaxial loading.