Proposed Finite Element Model Research Articles

Numerical investigation on milling performance and damage response of UD-CFRP laminates

Carbon fiber-reinforced polymer (CFRP) is prone to machining defects, including burrs and tearing, during milling. These defects are closely associated with interface delamination while milling force plays a crucial role in their occurrence. In this paper, a nonlinear explicit finite element (FE) model is developed to predict the milling force and analyze the delamination damage occurring during the milling of unidirectional CFRP (UD-CFRP). The proposed FE model is validated through numerical comparison with experimental data for milling force. Moreover, a detailed study is conducted to examine the influences of spindle speed, feed rate and depth-of-cut on the side-milling performance and damage response of UD-CFRP. This study provides valuable insights into the effects of machining parameters on milling force and delamination damage in CFRP, thereby supporting the optimization of machining technology for this composite material system.

Study on seismic behavior of prefabricated shear wall with pressed cone sleeves (PCSs)

Current prefabricated shear walls predominantly utilize grouting sleeves for connection, whereas an in-depth review and summary of the current state of research have indicated a 26.7 % construction defect rate in these sleeves due to present construction techniques. To solve the problem of defects, this study introduced a novel prefabricated shear wall design using vertical rebars connected via pressed cone sleeves (PCSs). Three reinforced concrete (RC) prefabricated shear walls with different vertical rebars connected and tested under cyclic horizontal load and constant vertical load to study the seismic performance, including cast-in-situ shear wall (specimen SW1), partial sleeve grouting defects shear wall (specimen SW2) and shear wall with vertical rebars connected via PCSs (PCSs-SW, specimen SW3). Key performance indicators such as failure modes, hysteresis curves, shear capacity, stiffness, ductility, energy dissipation capacity and stress characteristics were evaluated. The results of the tests revealed that SW1 and SW3 failures resulted from a combination of bending moment and shear force, whereas SW2 failure in the area of grout sleeve defects connection. Compared to the specimen SW2, the SW3 owns better shear bearing capacity, ductility, stiffness, energy dissipating capacity and reliable seismic performance. Meanwhile, SW3 and SW1 exhibited the similar seismic performance, can primarily achieve the effect of “equivalent cast-in-situ”. Finite element (FE) model of specimen SW3 were developed by using software ABAQUS, and the precision and utility of FE models verified by testing data. Using proposed FE models, an extensive parametric study was conducted to investigate the influencing factors on the seismic performance of precast fabricated RC shear wall, including axial compression ratio, concrete strength, vertical rebar strengths and vertical rebar diameters.

Seismic performance of precast bridge bents with prestressed piles and new pocket connection design: Experimental and numerical study

Pile-slab bridges with prestressed high-strength concrete (PHC) piles or prestressed and reinforced high-strength concrete (PRC) piles are widely used in low-seismic zones. To further understand the seismic performance of pile-slab bridges and to promote their applications in high-seismic regions, specimens of PHC bent (PHCB) or PRC bent (PRCB) from pile-slab bridges with a new bent-cap-pile pocket connection are studied through quasi-static cyclic tests. Seismic performance of the PHCB and PRCB is evaluated and compared in terms of damage development, failure mode, lateral stiffness, residual displacement, peak strength, displacement and energy-dissipation capacity. The experimental results show that both PHCB and PRCB fail due to non-ductile fracture of prestressing rebars in the piles, and the proposed bent-cap-pile pocket connection remains functional throughout the tests. Additional mild rebars of PRCB significantly increase displacement capacity of PRCB against PHCB. Finite element (FE) models are then developed and validated by the experimental results, after which the influence of initial prestressing force level and longitudinal prestressing reinforcement ratio of piles is investigated through parametric study based on the validated models. The proposed FE models can accurately predict the overall hysteretic behavior. Based on the parametric study, the seismic performance of both PHCB and PRCB can be improved by decreasing initial prestressing force level or increasing longitudinal prestressing reinforcement ratio.

3D slope stability analysis considering strength anisotropy by a micro-structure tensor enhanced elasto-plastic finite element method

This article presents a micro-structure tensor enhanced elasto-plastic finite element (FE) method to address strength anisotropy in three-dimensional (3D) soil slope stability analysis. The gravity increase method (GIM) is employed to analyze the stability of 3D anisotropic soil slopes. The accuracy of the proposed method is first verified against the data in the literature. We then simulate the 3D soil slope with a straight slope surface and the convex and concave slope surfaces with a 90° turning corner to study the 3D effect on slope stability and the failure mechanism under anisotropy conditions. Based on our numerical results, the end effect significantly impacts the failure mechanism and safety factor. Anisotropy degree notably affects the safety factor, with higher degrees leading to deeper landslides. For concave slopes, they can be approximated by straight slopes with suitable boundary conditions to assess their stability. Furthermore, a case study of the Saint-Alban test embankment A in Quebec, Canada, is provided to demonstrate the applicability of the proposed FE model.

Shake table testing and finite element modeling of a modular prefabricated concrete bridge‐like specimen accounting for geometry imperfections and additional damping

AbstractThis paper presents the shake table testing and finite element (FE) modeling of a modular prefabricated concrete bridge‐like specimen. The specimen comprised four equal‐height cylindrical reinforced concrete (RC) columns capped with an RC slab. The structural connections were non‐monolithic. Hence, controlled relative motion of the members, including rocking (uplift) of the piers, was allowed. The columns were connected to the slab with stiff tendons that provided positive post‐uplift stiffness. The specimen was subjected to 184 triaxial shake table tests, so that a statistical validation of numerical models can be performed. Subsequently, a detailed three‐dimensional FE model of the bridge was developed. The objectives of the present study were to: i) investigate the shake table response of a modular bridge with positive post‐uplift stiffness under multiple ground motions, ii) develop an FE model of the proposed structural system, iii) investigate the influence of geometrical imperfections on rocking bridges, and iv) evaluate the efficiency of using additional dissipative rebars. After being subjected to 184 shake table tests, the specimen showed zero damage, moderate displacements and tendon forces (TFs), low slab torsion, and zero residual displacements. The shake table tests were practically repeatable. The proposed FE model accurately captured the experimental results. Geometrical imperfections heavily affect the response of negative stiffness systems. However, they have a marginal influence on positive stiffness systems. When comparing systems with equivalent uplift resistance and post‐uplift stiffness, the use of additional dissipative rebars results in lower slab torsion and TFs, provided that the rebars do not fracture.

A multiscale finite element modeling for predicting the surface integrity induced by thermo-mechanical loads during high-speed milling of Ti-6Al-4V

High-speed milling (HSM) of Ti-6Al-4V is subjected to complex thermo-mechanical loads, leading to alteration in metallurgical conditions within the cutting deformation zones, adversely impacting the mechanical performances of manufactured products. Hence, inclusive insight into microstructural alterations within the Adiabatic Shear Band (ASB) and the milled surface becomes essential for better service performance. This study first developed a Finite Element (FE) milling model to simulate the machining process of Ti-6Al-4V. The proposed FE model is validated through experimental results regarding cutting forces (CFs), cutting temperature (CT), and chip geometry, where the absolute relative error between simulations and experiments was less than 15 %. Secondly, Zenner-Holloman (Z-H) and Hall-Petch (H-P) equations were incorporated into a user-defined subroutine to simulate dynamic recrystallization (DRX) for grain size and microhardness prediction. Simulation results revealed that the grains became finer in the ASB than on the milled surface. In particular, when the cutting speed and feed rate were increased to 350 m/min and 0.30 mm/tooth, the grain size in the ASB decreased from 14 to 0.68 and 0.44 µm, while in the topmost milled surface, it reduced to 7.06 and 6.75 µm, respectively. Conversely, microhardness exhibited an inverse correlation with grain size and increased with cutting speed and feed rate. Furthermore, the impact of increased plastic strain and temperature on the grains during chip segmentation was also examined. Finally, the proposed FE model validity was established by comparing simulated results with experimental data using advanced characterization techniques. This research significantly contributes to a comprehensive understanding of microstructural evolution and its implications for the mechanical performance of machined titanium components.

A Numerical Study on Predicting Bond-Slip Relationship of Reinforced Concrete using Surface Based Cohesive Behavior

Overall structural integrity and load transfer between concrete and reinforcement enabling composite action relies on the bond between concrete and reinforcement. Bond strength determination of reinforced concrete is an essential task that a pullout test can determine. Experimental pullout behaviour can be affected by various parameters, such as concrete and steel strength, boundary conditions, etc. Therefore, a parametric study on pullout tests is time-consuming. In addition, measurements of internal stress-strain components and damages of constitutive materials are also difficult in experimental endeavours. In this context, finite element (FE) models should be developed to perform a parametric study with cost and time-saving. This study proposes a finite element modeling strategy of reinforced concrete under pullout force by using the expected failure mechanism to predict bond-slip behaviour in ABAQUS. In FE models, surface-to-surface cohesive interaction behaviour was used to assign interaction between reinforcement and concrete. The proposed modelling strategy was validated with available experimental data from four reference specimens, having all possible failures (i.e., pullout, splitting, and splitting-pullout) under pullout loading. The finite element analysis showed that the proposed FE modeling strategy performed well in predicting bond-slip behaviour in elastic regions. Additionally, maximum bond stresses were predicted satisfactorily, except for the splitting failure pattern, using the proposed FE modelling strategy.

Shaking Table Tests and Numerical Analysis Conducted on an Aluminum Alloy Single-Layer Spherical Reticulated Shell with Fully Welded Connections

Aluminum alloy offers the advantages of being lightweight, high in strength, corrosion-resistant, and easy to process. It has a promising application prospect in large-span space structures, with its primary application form being single-layer reticulated shells. In this study, shaking table tests were conducted on a 1/25 scale aluminum alloy single-layer spherical reticulated shell structure. A finite element (FE) model of the reticulated shell structure was established in Ansys. Compared with the experimental results, the deviation in natural frequency, acceleration amplitude, and displacement amplitude was less than 20%, confirming the validity of the model. An extensive analysis of the various rise–span ratios and connection constraints of a single-layer spherical reticulated shell structure was carried out using the proposed FE model. The experimental and simulation results showed that as the rise–span ratio of the aluminum alloy reticulated shell increases, the natural frequency of the reticulated shell structure also increases while the dynamic performance decreases. The connection of the circumferential members changes from a rigid connection to a hinged connection. The natural frequency of the reticulated shell structure is reduced by about 40% while the acceleration and displacement response values are decreased by approximately 15%.

Numerical investigation on mechanical behavior of 3D orthogonal woven composites in hygrothermal environments

3D orthogonal woven composites (3DOWCs) are increasingly utilized in various engineering applications due to their superior mechanical properties. However, their mechanical properties and damage mechanisms could be significantly influenced by the environmental factors such as temperature and moisture. This study aims to investigate the mechanical behavior of 3DOWCs under hygrothermal conditions through meso-scale finite element (FE) simulations. The proposed FE model is validated using existing experimental results under standard temperature and humidity conditions, and subsequently applied to predict the performance in hygrothermal environments. The effects of temperature, humidity, and loading conditions on the mechanical properties of 3DOWCs are analyzed and the corresponding failure mechanisms are revealed. This study offers significant insights into the hygrothermal behavior of 3DOWCs, thereby facilitating their optimal design and implementation in various engineering applications.

Numerical simulation of temperature profile during laser cladding of nickel powder for in situ repairing

A 3-D Finite Element (FE) model was established to simulate the laser cladding of nickel powder for in situ repairing AISI 410 stainless steel. The temperature distribution field was estimated at six different points using low laser power of 450 W and a scanning speed of 2 mm/s. This study used a moving laser heat source in COMSOL to simulate the laser cladding process. The proposed FE model investigated the temperature field in two cases: (1) in situ repairing the defect by laser cladding without preheating and (2) in situ repairing the defect by laser cladding technique after preheating the cavity made on the substrate. A time-temperature profile was obtained after the simulation in both cases. The results of both cases were compared and analyzed. When the cladding material is poured into the preheated cavity, its temperature rises due to the heating effect obtained from the cavity, resulting in a higher maximum temperature after the cladding process. It was observed that after the cladding process, the maximum temperature was higher in the case of laser cladding after preheating the substrate (2400.49 K) compared to the maximum temperature in cladding without preheating the substrate (1770 K). Therefore, a molten pool is formed, solidifying rapidly to form a clad coating with better metallurgical bonding and enhanced surface properties.

Numerical investigation on orthogonal cutting and damage response of CFRP/Ti6Al4V stacks

CFRP/Ti6Al4V stacks are widely employed in aerospace, automotive and marine applications owing to their superior properties. However, machining these stacked structures pose challenges due to the intrinsic difference in the mechanical properties of CFRP and Ti6Al4V. Such difference can induce distinct failure mechanisms and chip formation processes compared to those observed in individual materials. This paper presents an explicit finite element (FE) modeling to predict the cutting forces and analyze the induced damage during the orthogonal cutting process. The proposed FE model is validated using available experimental data for separate CFRP and Ti6Al4V conditions before being applied to simulate the cutting behavior of CFRP/Ti6Al4V stacks. The effects of fiber angles, cutting sequences and cutting parameters on the cutting performance and damage mechanism of CFRP/Ti6Al4V stacks are investigated in detail. This work provides insights into the cutting behavior of CFRP/Ti6Al4V stacks and facilitates the optimization of machining process for such composite system.

Numerical simulation of corroded circular hollow section steel columns: A corrosion evolution approach

This study introduces a numerical simulation method for corroded circular hollow section steel columns, utilising a newly developed corrosion evolution model. This model was formulated by characterising the corrosion morphology and calibrating parameters throughout the entire corrosion process. An interpolation method was implemented to estimate the number of corrosion pits, based on experimentally measured corrosion ratios. Consequently, this allowed for the numerical prediction of the time-varying corrosion morphologies. Finite element (FE) models, incorporating this corrosion evolution model, were constructed. These corroded column models underwent validation through comparison with experimental findings. To further establish the effectiveness of the proposed FE models in predicting the structural behaviour of corroded members, FE models were also developed using the traditional uniform thickness reduction approach for comparative analysis. The results revealed that the proposed FE models for corroded structures offer a more accurate prediction of mechanical performance, particularly in instances of severe corrosion damage.

Experimental and Modelling of Lightning Damage to Carbon Fibre-Reinforced Composites under Swept Stroke

Lightning swept stroke creates multiple lightning attachments along an aircraft in flight. This introduces distinct structural damage compared to that from a single-point lightning current injection test in laboratory. This study presents both experimental and numerical studies on lightning damage in carbon fibre-reinforced polymer (CFRP) composites under swept stroke. Coupled electrical–thermal finite element (FE) models were proposed to predict lightning damage to CFRP composites under single-point current injection and swept stroke, respectively. A lightning swept stroke testing method was proposed by embedding a copper wire inside the composites to simulate multiple lightning attachments on the composites. The FE-predicted damage from single-point current injection and swept stroke were comparable to those obtained from the experiments with a deviation less than 23%, demonstrating the effectiveness of the proposed FE model. Finally, the FE model was further utilised to gain insights into the failure mechanism of CFRP composites under swept stroke associated with different skip distances and peak currents. This paper provides an experimental method and a FE model for obtaining the LS damage of CFRP composite by swept stroke.

Hysteretic behavior of prestressed high-strength bolt joint subject to combined flexure and axial forces for prefabricated prestressed spatial structures

A novel prestressed high-strength bolt (PHSB) joint applied in the prefabricated large-span ridge tube cable dome with annular struts (PLRTCDAS) was proposed. Firstly, the hysteretic behavior of the PHSB joint under combinations of bending moment and axial compression was studied by experiments. Four parameters of the PHSB joint, including the disc thickness, perforated cross plate thickness, perforated angle steel thickness, and outer sleeve height, were considered in the test. The effects of these parameters on the hysteretic curves, skeleton curves, bearing capacity, failure modes, energy dissipation behavior, and ductility were analyzed and discussed in detail. Secondly, a three-dimensional finite element (FE) model of the PHSB joint considering geometric, material, and interaction nonlinearities was established by ABAQUS. The accuracy of FE model was verified by comparing the test and numerical results. Finally, the hysteretic behavior of the PSHB joint under different combinations of axial forces and bending moments was investigated by the proposed FE model. The research indicates that the PHSB joint exhibits perfect energy dissipation capacity and higher ductility. Reducing the perforated angle steel thickness or increasing the outer sleeve height can improve the hysteretic behavior of the PHSB joint without significantly reducing its bearing capacity. The verified FE model is an effective method to simulate PHSB joint hysteretic behavior.

Flexural vibration of elastic composite beams using a third-order deformation kinematics

The present study introduces a one-dimensional finite element (FE) model that utilizes third-order deformation kinematics to analyze the flexural vibration of two-layered composite beams with partial shear slip. The proposed model incorporates a three-node straight beam element, utilizing the field-consistent approach and full numerical integration of the stiffness matrix. This approach is adopted to effectively address stress oscillation and shear locking issues, ensuring accurate and reliable results. The analysis focuses on the third-order deformation kinematics of longitudinal displacement within the beam depth, examining each of the two layers individually. The interface between the two material layers is joined using deformable shear connectors, which are represented as dispersed shear springs over the length of the beam. This study focuses on conducting a flexural vibration analysis of two-layered composite beams. The analysis includes the examination of both free vibration and forced vibration responses while considering or omitting the influence of damping under various loading conditions. The validity of the proposed FE model is assessed by the utilization of a two-dimensional model developed within the ABAQUS software. Additionally, the suggested model is evaluated through the process of verification by comparing it with previously published results.

Behavior of CFRP strengthened concrete-filled steel tubes with spherical-cap gap under axial compression

Carbon fiber-reinforced polymer (CFRP) strengthening can be considered as an effect approach to compensate the unfavorable influence caused by the spherical-cap gap on concrete-filled steel tube (CFST) structures. In the present study, the influence of CFRP wrapped on the mechanical behavior of CFST with spherical-cap gap (CFST-G) is examined. Sixteen CFST stub columns are experimentally tested under axial compression loads, considering the gap ratio and the number of CFRP layers (nCFRP) as the main parameters for analysis. The test results show that the bearing capacity decreases with increasing gap ratio, and the wrapped CFRP effectively improves the axial bearing capacity of CFST-G. Notably, the strengthening effect increases as nCFRP increases. Meanwhile, finite element (FE) models are established and verified against the test results. The proposed FE model is then used to conduct behavior analysis, and the working mechanism of CFST-G with CFRP strengthened is revealed. Parametric studies are also carried out by the FE model. The results show that, under the same gap ratio, the strength index decreases with increasing steel strength, steel ratio, and nCFRP, whereas it increases as the concrete strength increases. Based on the test and numerical analysis results, a simplified formula to calculate the bearing capacity of CFRP-strengthened CFST-G is proposed, providing a basis and reference for practical engineering and design codes.

An improved method for monitoring the junction temperature of 1200V / 50A IGBT modules used in power conversion systems

Abstract Insulated gate bipolar transistor (IGBT) is one of the most used devices for high-power-density and high-voltage applications such as wind turbines, electric vehicles, and smart grids. However, the field of IGBT research is still in its infancy owing to the failures that can happen to the module due to its temperature rise. Hence, the junction temperature T j measurement of the active region is essential for analyzing and predicting the degradation state of the IGBT device. In this paper, an overall study, including uses of the governing thermal equation to estimate the junction temperature T j, experimental analysis of the IGBT component during operation, and a numerical finite element (FE) study, was conducted. The thermal management FE model is conducted to predict temperature variation along time and heat spreading inside the IGBT layers. To investigate the material’s properties and structure change during operation impacting the junction temperature, scanning electron microscopy (SEM) and energy X-ray dispersive spectroscopy (EDS) were performed on the IGBT power module. Results were used to interpret the difference between the experimental and the predicted temperature values. For effectiveness validation purposes, results obtained from the proposed FE model are compared with the results of the experimental thermo-sensitive electrical parameters (TSEP) method. Good agreement was found between the experiment and the proposed FE model.

Numerical and theoretical studies for the shear behavior of CFRP plate-ECC-concrete composite interface

The shear behavior of the single-shear specimen with CFRP plate-ECC-concrete (CEC) composite interface was investigated using the finite element (FE) and theoretical calculation methods. The proposed FE model was established to simulate the entire loading process of the single-shear specimen under actual experimental conditions, and the newly developed CFRP-ECC interface model was incorporated. The FE model was calibrated and verified by comparing it with the experimental results. The results showed good agreement between the simulated and measured values for debonding load, shear stress, and interface damage. The proposed FE model was further adopted to perform parameter analyses of ECC thickness, CFRP bonding length, and CFRP plate width. This paper also proposed a calculation model for the debonding load of CEC composite interface considering the high tensile strength and the thickness of ECC. The results show that the proposed model shows a high accuracy for the prediction of debonding load.

Ballistic performance and damage behavior of three-dimensional angle-interlock woven composites under high velocity impact: Experimental and numerical studies

Three-dimensional angle-interlock woven composites (3DAWCs) are usually employed as exposed components in aerospace and other high-tech areas due to their superior impact resistance. In this work, the experimental characterization and numerical modeling are combined together to study the ballistic performance and damage behavior of 3DAWCs under high velocity impact (HVI). The initial-residual velocity relation is examined by ballistic impact test and the penetration process is recorded by high-speed camera. A nonlinear finite element (FE) model based on a multi-scale modeling framework is established to simulate the ballistic impact response and damage behavior of 3DAWCs. The proposed FE model is verified by comparing the predicted initial-residual velocity curve and penetration propagation with the experimental data. Parameter analysis is conducted to address the influences of projectile diameter and impact angle on the impact performance of 3DAWCs and the corresponding damage mechanisms are revealed in detail. The present work provides a transferable approach for studying the HVI problems of other textile composite structures.

Self-Piercing rivet joining of multi-material including CFRP: Experiments and FE modeling

In this study, finite element (FE) analyses based on the arbitrary Lagrangian–Eulerian technique were used to investigate the complex deformation behavior and numerous process variables that arise during the self-piercing riveting (SPR) joining of multi-materials, including carbon-fiber-reinforced polymer, GA590DP, and Al5052-H32 sheets in two- and three-layer combinations. Tensile tests and inverse analysis were conducted to determine the mechanical responses of each joining material, including the rivet, and equivalent strain-based fracture modeling approaches were adopted for a simple but effective crack initiation prediction during the mechanical joining process. The damage distribution and joining characteristics during the SPR joining were then numerically investigated by considering different die profiles. The high predictability of the proposed FE modeling approach in terms of the cross-sectional profile with joint quality indicators, such as the interlock, residual distance between the rivet leg and die, minimum thickness of the bottom sheet, load history, and peak load during mechanical joining, was validated through comparisons between the experiments and FE simulations.