Finite Element Model Analysis Research Articles

Exteriorization of the uterus reduces fetoscopic cannula-induced stress and strain: A finite element model analysis.

To estimate stresses and strains in the uterine wall and fetal membranes with single/multi-port fetoscopy, simulating either a percutaneous access or via exteriorized uterus. Finite element models based on anatomical dimensions, material properties and boundary conditions were created to simulate stresses, strains and displacements on the uterine wall and fetal membranes during simulated fetal surgery either via exteriorized uterus or percutaneous approach, and with one or three cannulas. Clinically, we measured the anatomical layer thickness and cannula entry point displacement in patients undergoing single port percutaneous fetoscopy. Simulations demonstrate that single port percutaneous fetoscopy increases stress on the fetal membranes (+105%, 128 to 262 kPa) and uterine wall (+115%, 0.89 to 1.9 kPa) compared to exteriorized uterine access. Using three ports increases stress by 110% (148 to 312 kPa) on membranes and 113% (1.08 to 2.3 kPa) on uterine wall. Finite Element Method showed 0.75cm uterine entry point displacementfrom the cutaneous entry, while clinical measurements demonstrated displacement of more than double (1.69±0.58cm), suggesting modeled measurements may be underestimations. The stresses and strains on the fetal membranes and uterus are double as high when entering percutaneously than via an exteriorized uterus. Based on what can be clinically measured, this may be an underestimation.

Tube Mechanism With 3-Axis Rotary Joints Structure to Achieve Variable Stiffness Using Positive Pressure

Studies on soft robotics have explored mechanisms of switching the stiffness of a robot structure. The hybrid soft-rigid approach, which combines soft materials and high-rigidity structures, is the most commonly-used method for the variable stiffness mechanism. The positive-pressurization method, in particular, has attracted significant attention in recent years as it can remove the limit on the driving pressure. Moreover, it can change the shape holding force according to the value of internal pressure. In this study, a variable stiffness mechanism, consisting of 3-axis rotary ball joints and a single chamber, is devised via frictional force using positive pressure. The prototype can change joint angles arbitrarily when not pressurized and can hold joint angles when a positive pressure is applied. By using a theoretical model of the torque required to hold the joint angle, we simulated the holding torque using finite element modeling analysis and measured the holding torque in the pitch and roll directions when internal pressure was applied. Based on the interaction of the theoretical model, measurement, and FEM analysis, it was confirmed that the value of the holding torque in the roll direction was approximately π/2 times larger than that in the pitch direction for each value of the internal pressure. Further, we evaluated the FEM value, theoretical value, and measured value of holding torque by numerical comparison with each other. We believe that our approach will aid the design of effective stiffening mechanisms for soft robotics applications.

Lateral Displacement Behavior of IBS Precast Concrete Elements Reinforced with Dual System

Throughout history, the construction industry has been a significant contributor to construction waste, presenting an ongoing challenge in efficiently managing this waste to mitigate environmental pollution. The Industrialized Building System (IBS) stands out as a construction approach that utilizes prefabricated components made from various waste materials, implemented with machinery and formwork, leading to minimal waste production. The potential failure of IBS blockwork columns under lateral loads is a significant concern, and the deformation of these columns is crucial in assessing overall structural performance against lateral forces. This study focuses on examining the deformation and flexibility of components in IBS blockwork columns when subjected to lateral loads. Using Finite Element Modeling (FEM), a 1:5 scale prototype model of the dual-reinforced system IBS Block Work Column is analyzed. The IBS Block Work Column, comprising four prefabricated components assembled in the form of a crucifix plan to enhance lateral stability, is subjected to FEM analysis and experimental investigations. The study aims to explore the impact of four different shapes of reinforcement on deformation resistance. The findings suggest that employing a dual-reinforced system in the IBS Block Work Column enhances its resistance to lateral loads compared to a column with conventional reinforcement. Moreover, the assembled IBS Block Work Column exhibits greater stiffness than a single prefabricated component when subjected to lateral loads. Doi: 10.28991/CEJ-2024-010-01-020 Full Text: PDF

Numerical and theoretical analysis on soil arching effect of prefabricated piles as deep foundation pit supports

This study presents a detailed investigation into the soil arching effects within deep foundation pits (DFPs), focusing on their mechanical behavior and implications for structural design. Through rigorous 3D finite element modeling and parameter sensitivity analyses, the research explores the formation, geometric characteristics, and spatial distribution of soil arching phenomena. The investigation encompasses the influence of key parameters such as elastic modulus, cohesion, and internal friction angle on the soil arching effect. The findings reveal that soil arching within DFPs exhibits distinct spatial characteristics, with the prominent arch axis shifting as excavation depth progresses. Optimal soil arching is observed when the pile spacing approximates three times the pile diameter, enhancing soil retention and minimizing deformation risks. Sensitivity analyses highlight the significant impact of soil parameters on soil arching behavior, underscoring the critical role of cohesive forces and internal friction angles in shaping arching characteristics. By elucidating the interplay between soil parameters and soil arching effects, the research provides insights for optimizing pile spacing and structural stability.

Design and numerical analysis of new earthquake-resilient semi-rigid joints

A calculation method for the design of a new earthquake-resilient semi-rigid joint was proposed, and its accuracy was verified through cyclic loading tests. Finite element model analysis was performed to investigate the energy dissipation capacity of the new joint. The deformation characteristics, energy dissipation capacity, and stiffness of energy dissipators with different shapes and lengths were compared. Subsequently, the computational method was improved. The parametric analysis results revealed the excellent seismic performance of the joint; the energy dissipator dissipated more than 75% of the energy. Furthermore, we assessed the influence of the area, shape, and length of the energy dissipators on their energy dissipation capacity. Increasing β (the ratio of the flange to web area in the energy-dissipating core area) and γ (the slenderness ratio of the energy-dissipating core area) resulted in an initial rise in the energy dissipation capacity followed by a decrease. The recommended values for β and γ are 0.67 and 7.71–9.21, respectively.

Research on the Multi-Angle Seismic Spectrum Response Law of Auxiliary Feedwater Electric Pumps

The auxiliary feedwater electric pump, which is vital in nuclear power units, demands exceptional seismic reliability. The impact of the seismic excitation direction on the seismic response of the complex auxiliary feedwater electric pump structure remains inadequately understood, thereby introducing uncertainties into seismic analysis and equipment installation procedures. To address this challenge, this study centers on a representative horizontal multi-stage centrifugal pump based on the finite element model and modal analysis. Utilizing the response spectrum method and the square root of the sum of the squares (SRSS) vibration pattern superposition principle, the research comprehensively explores the seismic response characteristics of individual pressure-bearing components and key rotor positions under seismic excitation from various angles. Findings reveal intricate variations in maximum stress and displacement responses for each pressure-bearing component under safe shutdown earthquake (SSE) level seismic excitation, corresponding to different input angles of seismic spectra. In assessing the seismic operability of the clearance between the impeller and the stator, the direction near 45° exhibits the maximum displacement response, highlighting the need for focused attention in testing and verification checks. The methodologies and conclusions presented in this paper offer valuable insights for designing, optimizing, and installing horizontal multi-stage centrifugal pumps, including auxiliary feedwater electric pumps, providing valuable guidance for future applications in the field.

Review and Assessment of Fatigue Delamination Damage of Laminated Composite Structures.

Fatigue delamination damage is one of the most important fatigue failure modes for laminated composite structures. However, there are still many challenging problems in the development of the theoretical framework, mathematical/physical models, and numerical simulation of fatigue delamination. What is more, it is essential to establish a systematic classification of these methods and models. This article reviews the experimental phenomena of delamination onset and propagation under fatigue loading. The authors reviewed the commonly used phenomenological models for laminated composite structures. The research methods, general modeling formulas, and development prospects of phenomenological models were presented in detail. Based on the analysis of finite element models (FEMs) for laminated composite structures, several simulation methods for fatigue delamination damage models (FDDMs) were carefully classified. Then, the whole procedure, range of applications, capability assessment, and advantages and limitations of the models, which were based on four types of theoretical frameworks, were also discussed in detail. The theoretical frameworks include the strength theory model (SM), fracture mechanics model (FM), damage mechanics model (DM), and hybrid model (HM). To the best of the authors' knowledge, the FDDM based on the modified Paris law within the framework of hybrid fracture and damage mechanics is the most effective method so far. However, it is difficult for the traditional FDDM to solve the problem of the spatial delamination of complex structures. In addition, the balance between the cost of acquiring the model and the computational efficiency of the model is also critical. Therefore, several potential research directions, such as the extended finite element method (XFEM), isogeometric analysis (IGA), phase-field model (PFM), artificial intelligence algorithm, and higher-order deformation theory (HODT), have been presented in the conclusions. Through validation by investigators, these research directions have the ability to overcome the challenging technical issues in the fatigue delamination prediction of laminated composite structures.

Tarihi Kubbeli Yapıların Çekme Bölgelerinde Karbon Fiber Takviyeli Polimer ve Cam Fiber Takviyeli Polimer Kullanılarak Güçlendirme Yönteminin Sonlu Elemanlar Analizi: Edirnekapı Mihrimah Sultan Camii Kubbesi

Historic buildings are remarkable monuments that carry cultural traces and heritage from the past to the present and from the present to the past in terms of historical sustainability. These assets worthy of preservation should be restored and strengthened under certain intervention criteria for the continuity of cultural accumulation. Although historical masonry buildings exhibit a very rigid performance under vertical loads, their tensile strength against lateral loads such as seismic forces created by earthquakes is low. Domes, an important architectural element of masonry buildings, are likely to be damaged under the influence of seismic forces. The retrofitting analyses were performed with CFRP and GFRP in the dome tensile zones and readings were made on the Modulus of Elasticity. Since Edirnekapı Mihrimah Sultan Mosque is a structure sensitive to seismic force due to its location and the earthquakes experienced by the structure, it was deemed suitable for finite element model analysis.

Axial compressive behavior of high-strength concrete-filled steel tube with multiple confinement effects

To study the axial compressive behavior and the confinement mechanism of high-strength concrete-filled circular steel tube with multiple confinement effects, five large size samples with horizontal stiffeners, longitudinal stiffeners, multilayer reinforcement cages, inner steel tube and separation steel plates were designed. The influences of these structures on the bearing capacity, ductility, stiffness, and residual deformation were then analyzed. Combining the strain analyses and finite element model analysis, the confinement mechanism of different structures and the coupling mechanism of different confinement effects were investigated. The results showed that the confinement effect of the horizontal stiffeners was similar to that of the stirrups. The longitudinal stiffeners did not provide a significant confinement effect on the concrete. The multilayer reinforcement cages had an effective confinement effect on the concrete, where the confinement effect increased from the outside to the inside, while the reinforcement cages had a slight influence on the concrete outside the reinforcement cages. The inner steel tube had an effective confinement effect on the core concrete and had a slight influence on the concrete outside the inner steel tube. The multicell steel tube showed the best confinement effect compared to the other structures and showed the best axial compressive behavior. In the confinement mechanism analyses, the calculation method of the stress–strain relationship of concrete with multiple confinement effects was proposed. The calculated F-Δ curves showed a good agreement with the test results.

Finite Element Modeling and Optimization Analysis of Cutting Force in Powder Metallurgy Green Compacts

Powder metallurgy (PM) is a manufacturing technique that employs metal powder as the raw material, which is then molded and sintered to produce various products. PM green compacts are inherently weak, rendering them prone to damage during machining due to cutting forces, which also affect the quality of the machined surface. To study the impact of different machining variables on cutting force, a finite element simulation (FEM) was employed, focusing on cutting thickness, cutting speed, tool rake angle, and rounded edge radius. The results indicated that cutting thickness had a highly significant impact on cutting force, while the rounded-edge radius and cutting speed were also significant factors. The tool rake angle was found to have minimal effects. The optimal parameters for minimizing cutting force were identified: a cutting thickness of 0.20 mm, a cutting speed of 120 m/min, a tool rake angle of 0°, and a rounded-edge radius of 40 μm, which reduced the cutting force to 887.95 N.

Processing and structural health monitoring of a composite overwrapped pressure vessel for hydrogen storage

A process and Structural Health Monitoring system was implemented on a Composite Overwrapped Pressure Vessel (COPV) for hydrogen storage at 350 bar to be used in a fuel-cell system of an Unmanned Aerial Vehicle. This work reports the embedment strategy of optical fibre Bragg grating (FBG) sensors to monitor the full life cycle of the vessel, consisting of an aluminium liner and a wound carbon fibre reinforced polymer composite overwrap. A FBG sensing array, bonded on the aluminium liner circumferential section, was covered with a localised unidirectional prepreg composite tape, enabling composite winding and curing monitoring. The sensing array strategy allowed to detect and locate Barely Visible Impact Damage resulting from drop-weight impact tests, based on the ratio of the residual strain amplitude between FBG sensor pairs. Errors as small as 17 mm and up to 56 mm were determined between the predicted and ‘real’ impact locations. To simulate the real-life operational pressure charging and discharging cycles, the COPV was subjected to cycling testing at different pressure ranges. The FBG sensors were able to monitor a total of 20 980 pressure cycles, revealing a linear response to the applied pressure, and remained operational after COPV failure. Furthermore, the FBG sensing array was able to detect the residual plastic strain caused in the aluminium liner by the autofrettage process that the COPV was subjected to prior to pressure cycling, at 600 bar for 2 min, to improve its fatigue performance. This manuscript also reports the COPV structural design by Finite Element Modelling (FEM), its manufacturing process and burst pressure testing for the FEM analysis validation. A small difference of 0.7% was found between the simulated and experimental determined burst pressure of 1061 ± 26 bar.

Optimisation design of a large space cable-pole tensioned parabolic cylindrical antenna mechanism

The cable-strut structure optimisation of a large space cable-strut tensioned parabolic cylindrical antenna is studied. Firstly, the deployment mechanism is designed, and the degree of freedom and kinematics analysis of the mechanism are conducted. Secondly, a complete tension cable configuration with 58 tension cables in 24 categories is established on the basis of the structural characteristics and constraints. A configuration optimisation design method based on the influence coefficient of comprehensive stiffness is proposed. A less tensioned cable optimisation configuration with better static and dynamic stiffness performance is established on the basis of the fully tensioned cable configuration and using the proposed method, and the stiffness characteristics of the configuration are verified through the analysis of an example. Lastly, a mathematical surrogate model between the designed angle and length parameters of the reflector rod system and the fundamental frequency of the antenna is established using the response surface method, and the optimal solution of the reflector rod system is obtained by a genetic algorithm. The effectiveness of the optimisation is verified by finite element modelling and simulation analysis. This study provides a basis and reference for the structural dynamic modelling, characteristic analysis and optimal design of a large space cable-strut tensioned parabolic cylindrical antenna.

Comparison of sacroiliac screw techniques for unstable sacroiliac joint disruptions: a finite element model analysis

Vertically unstable pelvic injuries associated with sacroiliac disruption are challenging. Although percutaneous iliosacral fixation using two screws at S1 vertebral body has been shown beneficial, the use of two transiliac screws at S1 has been proposed to increase the fixation strength of the construct. In the herein study, the finite element method (FEM) was performed to analyse the biomechanical behaviour of five different constructions using iliosacral screws only, transiliac screws only, and combining an iliosacral and a transiliac screw. A vertically unstable AO 61C1.2 type pelvic injury was produced for the evaluation of the posterior pelvic displacement and implant stress, and the anterior implant stress using FEM. The symphysis pubis was fixed with a 3.5-mm reconstruction plate in all cases. The model was axially loaded with 800N applied in the centre of S1 body, perpendicular to the ground (Y-axis), simulating the bipodal stance moment. There was a statistically significant reduction in both posterior displacement and implant stresses in the groups fixed with at least one transiliac screw compared to the groups fixed with iliosacral screws. In our FEM study, the construct using two transiliac screws in S1 is biomechanically superior for stabilizing the sacroiliac joint in vertically unstable pelvic ring injuries compared to the other configurations. Lateral displacement, posterior displacement, and von Mises stress were reduced with this construct. A good option can be the use of one iliosacral screw and one transiliac screw in S1.

The Effects of Corrosion and Fire Damage on the Steel-Bolted T-Section Connections Used in the Steel Construction.

The most common type of connection in steel structures is the T-section connection. Steel structures can be damaged due to environmental effects such as earthquakes, fires, corrosion, etc., in real applications used in industry. Therefore, in this study, the corrosion and fire condition effects that occur in the T-section connection on the behavior of the connection zone were investigated. The study was carried out with 18 T-section connections with various corrosion (hydrochloric acid and sulfuric acid) in different layers at 5, 10, 15, and 20% corrosion levels, and fire (ISO834) conditions after corrosion have been evaluated and compared. T-section-bolted joints examined in the study were produced using IPE300 standard profiles. In the first part of the study, the behavior of the 18 T-section connections under an axial tensile load has been determined experimentally. The second part created a finite element model with the ABAQUS program for all models. It was seen that the finite element model analysis results converged with the results obtained as a result of the experimental study. As a result, compared to H2SO4 corrosion, HCl corrosion has little effect on the load-deformation characteristics of the connections. Also, if corrosion specimens are exposed to fire, then the connections will change from semirigid to hinged.

Numerical investigation of ultimate bearing capacity of circular and square concrete-filled double steel tubular T-joints

The punching shear problem in composite T-joints with doubler plates has been evaluated in various design codes of practice. However, code provisions do not address the behavior of concrete-filled double steel tubular T-joints filled with concrete, in which concrete contributes to a portion of the shear force to resist punching. The present study presents a finite element modeling analysis to investigate the ultimate load-bearing capacity of circular and square concrete-filled double steel tubular T-joints. A set of 24 double-skin concentric tubular joint specimens were modeled in ABAQUS. A subsequent parametric study was carried out to examine the influence of infill concrete compressive strength, steel tube cross section shape, and section width-to-thickness ratio. Accordingly, stress evolution pattern, buckling mode, stress-strain response, and load–displacement curve of the entire T-joints were investigated. Based on the results obtained, it was revealed that recession in the flange of the primary component, as well as the heaving of the primary component web, are the main reasons for the higher stress levels. It was also seen that when the compressive strength of the infill concrete is 45 MPa, the maximum stress level in circular concrete-filled double steel tubular joint is 2.6 × 102 MPa, while that in the square joint is 2.566 × 102 MPa. The corresponding values for concrete with a compressive strength of 30 MPa are 2.58 × 102 MPa and 0.455 × 102 MPa, respectively. It was also observed that when the width-to-thickness ratio is increased from 20 to 33.33 in circular T-joints, the ultimate load-bearing capacity is reduced by 15%.

Refined beam finite element model for thin-walled multi-cell box girders considering distortion and secondary distortional moment deformation effect

In this paper, a novel one-dimensional refined beam finite element model (FEM) accounting for non-uniform distortional warping and secondary distortional moment deformation effect (SDMDE) is formulated for the distortional analysis of thin-walled multi-cell box girders with cantilevered flanges. The extra distortional angle is introduced to incorporate SDMDE, and the validity of which is proved through rigorous theoretical derivation. The in-plane and out-plane deformations at any point around the edge of transverse section built upon the distortional center are unified in the same form and described in detail. The governing differential equations in terms of two generalized displacements, distortional angle χ and primary distortional angle curvature Θ, are derived based on the principle of minimum potential energy (MPE) and solved exactly so as to provide non-polynomial shape functions for the establishment of element stiffness matrix and nodal load vector. A series of multi-cell rectangular hollow section (RHS) girders are analyzed and particular extensions are given to single-cell and multi-cell bridge girders with cantilevered flanges. Comparisons to the results generated from corresponding ones provided by pioneering work or shell FEM analyses not only validate the correctness and reliability of the present beam element formulations but also highlight the significance of the inclusion of SDMDE when the cantilevered flanges are arranged.

Model test and finite element analysis results of a monopile in very dense sand under unidirectional horizontal cyclic loading

This study is carried out to understand the response of a monopile for a large (8–9 MW) offshore wind turbine located at a 45m water depth under lateral cyclic loading. Firstly, a 1g large-scale model pile test was performed in saturated very dense sand under numerous cycles of lateral loading, N=2000. The test results show that the lateral pile head displacement and rotation increase while the secant stiffness of pile decreases with increasing N. The numerical model was then validated by comparing the pile head displacement results of the test and the finite element (FE) model analysis. The soil was modelled using the UBC3D-PLM constitutive model to understand the development of the excess pore pressure ratio (EPPR) around the monopile. The FE analysis was performed cycle by cycle up to N=5 for a large diameter “XL monopile” with diameter D=9m and embedded length L=50m. The results showed that the EPPR around the monopile is insignificant. Furthermore, the effect of the number of loading cycles on the evolution of the EPPR, pile head deformation and pile head rotation are insignificant. In addition, a relatively high maximum pile head rotation accumulation θmax≅0.13° was obtained during cyclic loading.

Finite element modeling and behavior analysis of axially comprised circular dual tube columns filled with concrete

Finite element modeling and behavior analysis of axially comprised circular dual tube columns filled with concrete

Strength of Hybrid Steel-BFRP Reinforced Concrete Beams with Openings in the D-Region Strengthened Internally and Externally

The opened beams always confused the designers due to the guidelines missing. In this research, six hybrid beams reinforced with mixed steel and basalt fiber-reinforced polymer (BFRP) bars and having constant cross-sections of 150 mm × 300 mm and a clear span of 1800 mm were cast and tested under a four-point loading setup. Generally, five beams had symmetrical rectangular openings with dimensions of 150 mm × 250 mm located at a distance of 250 mm (equivalent to the beam effective depth) from the beam support, while an additional solid beam served as a control. The studied parameters included the effect of using internal reinforcement (steel or BFRP bars) provided adjacent to the opening sides or by incorporating an external BFRP sheet around the opening corners. Also, double enhancement with internal steel reinforcement bars together with external strengthening BFRP sheet was investigated. The relevant results showed that the opened beam without enhancement lost 75% of the maximum load compared with the solid beam. Placing internal steel or BFRP bars around the openings increased the maximum load by 62% and 60%, respectively, compared to the non-enhanced opened beams. Using an external BFRP sheet to strengthen the opening corners of the beam enhanced the maximum load by 76% compared with the non-enhanced opened beam. Consequently, by combining both the internal steel reinforcement and external BFRP sheet around the openings, the maximum load increased by 137% compared with the non-enhanced opened beam. Ultimately, a numerical analysis of the three-dimensional finite element model was performed to confirm the experimental findings, and the relevant results showed compatibility correlations with the experimental ones. Also, the effect of various parameters such as BFRP reinforcement ratio and number of BFRP sheet layers around the openings was investigated by adapting the validated numerical model.

Nonlinear finite element modeling and parametric analysis for the design implication of expanded rib steel bars in RC beams

The quest for innovative design of reinforced-concrete to make it more durable, flexible, and sustainable has brought a transition from traditional methods of lap splicing to the use of anchor-head bars. One such innovation is the state-of-the-art Expanded Rib Steel Bar (ERSB) technique which reduces the conventional splice-length and also lessens the stress concentration at the concrete anchor-head contact areas to avoid brittle failure. Leveraging the four-point-bending experimental results of ERSB and two conventional designs, this paper investigates the performance of ERSB using a nonlinear 3D-Finite-Element Model. The results indicate that the proposed FEM reproduces the experimental behavior of ERSB in terms of maximum strength, displacement, ductility ratio, and crack pattern accurately. Moreover, the performance of ERSB is superior than the single-head-anchor bars and similar to that of the reinforced beams without joints. A parametric study then suggests design implications which can be adopted to develop guidelines for designing ERSBs.