Finite Element Analysis Predictions Research Articles

Distributed optical fibre sensor based monitoring of thermoplastic carbon composite cylinders under biaxial loading: Experimental and numerical investigations

Composite tubes are used in numerous applications including aerospace, mechanical, civil and transport sectors, where they may be susceptible to combined loading especially axial compression and torsion and suffer failure due to their intrinsic weakness under such loads. An experimental cum numerical investigation is performed to understand the behaviour of hollow composite tubes with cut-outs under combined axial compression and torsional loadings. Carbon fibre reinforced thermoplastic CF/PEEK tubes with different diameters and varied lay-up sequences, were robotically manufactured using an Automated Fibre Placement (AFP) machine. These specimens were mechanically tested using a novel biaxial test jig, designed specifically to be compatible with an INSTRON 8852 axial/torsion servo hydraulic test system. A standard acrylate coated optical fibre was affixed on the surface of the cylinder for distributed strain sensing using an optical backscatter reflectometer (OBR) interrogator to obtain spatial strain data. Surface strains measured using distributed optical fibre sensing (DOFS) and strain rosettes were compared against finite element analysis predictions to successfully validate the numerical model created using Ansys ACP Pre-Post simulation package. Directional deformations around the cut-outs of these tubes were also numerically characterised and compared with digital image correlation (DIC) results from the experimental tests.

Finite element analysis for prediction of adolescent bone strength: micro vs continuum models

Adolescence is a crucial period for bone growth, and many factors during this period can influence bone quality and the intensity of peak bone mass, e.g., nutritional intakes and physical activity ...

Structural Performance of Steel-Tube Concrete Columns Confined with CFRPs: Numerical and Theoretical Study

Fiber-reinforced polymers (FRPs) are being widely used in the structural engineering because of their superior performance over conventional materials such as higher tensile strength, high corrosion resistance, electromagnetic resistance, good durability and light weight. The literature is deficient in the nonlinear finite element analysis (NLFEA) and theoretical predictions of FRP-confined concrete columns. The aim of the present work is to explore the structural performance of steel-tube FRP confined concrete (STC) columns under axial concentric loading. A NLFEA model of STC columns was simulated using ABAQUS which was then, calibrated for different material and geometric models of concrete, steel tube and FRP material using the experimental results from literature. The predictions of proposed NLFEA model were in close agreement with the previous experimental measurements. An extensive parametric study was performed to examine the effects of various parameters of STC columns. Furthermore, a large database of axial strength of 543 confined concrete compression members was developed from the previous researches to propose an empirical model that predicts the ultimate axial strength of STC columns accurately.

Crack length correction and root rotation angle in a sandwich single cantilever beam (SCB) fracture specimen

Crack root rotation is a measure of deviation from clamped boundary conditions of region in front of the crack tip. The root rotation depends on the shear force and bending moment acting at the crack tip. Such rotation significantly affects the compliance and energy-release rate. Crack root rotation analysis of Single Cantilever Beam (SCB) sandwich specimens is presented here. Closed-form solutions for the root rotation angle obtained from the foundation analysis are compared to finite element analysis (FEA) predictions. The derived expressions closely match for a range of sandwich configurations. An expression for the energy-release rate, derived from the foundation analysis was found to agree with FEA predictions over a large range of face-to-core modulus ratios. Energy-release rate and mode mixity phase angle increased with decreasing crack length due to the transverse shear effects. At longer crack lengths, both energy-release rate and phase angle reached a value independent of crack length. The foundation model is used to derive a simple expression for the offset crack length for the SCB sandwich fracture test. It is shown that the obtained formulation agrees closely well with both numerical and experimental values. In addition, SCB fracture tests performed using an in-house built translatable rig showed close relation to both analytical and numerical compliance results.

Experimental and Numerical Comparison of Prestressed Perforated Concrete Rafters of Different Configurations

This paper demonstrates an experimental and numerical study aimed to compare the influence of openings of different configurations on the flexural behavior of prestressed concrete rafters. The experimental program consisted of testing six simply supported prestressed concrete rafters; 5 rafters are perforated, and the other one is solid as a reference. All rafters were tested under monotonic midpoint load. The variable which has been investigated in this work was the opening’s configuration (quadrilateral or circular) with the same upper and lower chords depths. The results indicate improvement in the beam flexural behavior using the circular openings compared to the quadrilateral openings, represented by increase the ultimate load capacity and decrease in deflection at the service limit. The experimental results of the tested rafters were confirmed by the non-linear finite element software (ABAQUS13.6.1). Comparisons are offered and the good agreement appears between the experimental results and the predictions of finite element analysis in terms of load-deflection and failure loads relationships.

Finite element analysis and EMA predictions of the dielectric and pyroelectric properties of 0-3 Pz59/PVDF-TrFE composites with experimental validation

Dielectric and pyroelectric thick film materials are of growing interest for applications in medicine, advanced sensors, energy storage and energy harvesting. In the present work, thick 0–3 composite films consisting of particles of a relaxor material embedded in the ferroelectric co-polymer PVDF-TrFE are characterized in terms of dielectric and pyroelectric properties. The experimentally measured properties are compared with the predictions of analytical models and finite element analysis (FEA). A three-dimensional numerical model has been developed via FEA to calculate the effective dielectric constant as a function of the volume fraction (0–30%) of the ceramic particles. An electro-thermal coupled model is proposed to calculate the pyroelectric coefficient. Furthermore, the distribution of the pyroelectric coefficient in different layers of the ferroelectric composite with 30 % ceramic volume fraction together with the component-resolved spatial distribution of the pyroelectric response are analyzed. Overall, simulation and experiment results show very good agreement. In particular, by analyzing the temperature distribution in the thick film, it is demonstrated that the pyroelectric coefficient increases from top to bottom surfaces. Ceramic particle distribution also affects the pyroelectric current.

Finite element modelling and theoretical predictions of FRP-reinforced concrete columns confined with various FRP-tubes

The present research work has endeavored to investigate the structural behavior of fiber reinforced polymer (FRP) reinforced concrete columns confined with FRP-tubes under axial concentric and eccentric loadings. A finite element analysis (FEA) model of FRP-tube confined concrete columns having longitudinal reinforcements of either carbon fiber reinforced polymer (CFRP) and/or glass fiber reinforced polymer (GFRP) bars, was simulated using a finite element (FE) package ABAQUS 6.14 which was then, calibrated for different material and geometric models of concrete, FRP-tube and FRP longitudinal reinforcement using the experimental results from the literature. The comparative study shows that the proposed FEA model presented a close agreement with the experimental measurements. A detailed parametric study was performed using the FEA model to examine the effects of various parameters of FRP composite columns on the axial load capacity and axial deflection. Moreover, a large database of axial strengths of 685 FRP-confined concrete compression members was developed from the previous researches to propose an empirical model that predicts the ultimate axial strength of FRP reinforced concrete columns confined with FRP-tubes accurately. The comparison of predictions of the proposed empirical model with the FEA predictions from the parametric study portrayed a close agreement among them. Thus, the proposed models are accurate enough to predict the behavior of FRP reinforced concrete columns confined with FRP-tubes.

The effect of low-velocity impact on the flexural strength of E-glass/epoxy composite plates

E-glass/epoxy composite is very prone to small impact such as dropping tools or splash rocks, which can cause damage or degradation to E-glass/epoxy composite components. A progressive damage model for E-glass/epoxy composite in ABAQUS Explicit was developed in this study to numerically predict low-velocity impact (LVI) damage and residual strength of an E-glass/epoxy composite component. Hashin-Rotem criteria were used to define laminate damage initiation, and traction-separation law was used to define the cohesive region. LVI and four-point bending after the impact (BAI) of the woven E-glass/epoxy composite plates were simulated and compared with available experimental data in the literature. Good agreement was found between finite element analysis (FEA) predictions and the experimental results, which include the impact zone shape, as well as the load-deflection response and residual bending strength from the four-point bending tests.

Punching shear design of RC flat slabs supported on wall corners

AbstractReinforced concrete buildings are typically braced with shear walls positioned around lift shafts and stairs. Vertical transfer of load from slab to walls leads to a concentration of shear stress in the slab at wall ends and corners, which needs to be considered in punching shear design. This issue is not addressed in EN 1992 (2004) and only partially addressed in fib Model Code 2010 leaving engineers to resort to their own judgment. Consequently, consideration of punching shear at wall corners can be overlooked entirely or not properly addressed through lack of knowledge. The paper addresses this issue by proposing a method for calculating the design shear stress at wall corners for use in conjunction with the Critical Shear Crack Theory. The method is initially validated against test results for slabs supported on elongated columns as well as numerical simulations. Subsequently, the method is extended to the punching design of a slab supported by a wall corner. The proposed analysis of the slab‐wall corner junction is validated against the predictions of nonlinear finite element analysis (NLFEA) employing 3‐D solid elements as well as the joint‐shell punching model (JSPM) previously developed by the authors.

Validation of Methods to Measure the Hardness and Elastic Modulus of Cold-Sprayed Al-ZN Composite Coatings

The elastic modulus and hardness of a cold-sprayed Al-25Zn metal matrix composite were characterized with the aid of Knoop and Vickers microindentation tests, nanoindentation test, and resonance frequency (RF) analysis. The mechanical properties were compared with the predictions of object-oriented image-based finite element (FE) analysis and related to the microstructural characteristics revealed by scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). The cold-sprayed coating exhibited an isotropic behavior along transversal and longitudinal directions and the predicted elastic modulus closely matched the results from the nanoindentation test. The approach offers a solution to the challenging task to determine the elastic modulus of thin coatings.

Experimental and numerical investigation on the deflection behavior of pre-cracked and repaired reinforced concrete beams with fiber-reinforced polymer

This paper presents an experimental and numerical study on the effect of fiber-reinforced polymer (FRP) sheets/laminates on the flexural deflection of pre-cracked and repaired reinforced concrete (RC) beams. The experimental program was aimed at studying the carrying capacity of repaired beams through load-deflection curves along with failure modes which can occur in unrepaired and repaired RC beams. The types of FRP reinforcement (CFRP sheet, GFRP sheet and CFRP laminate) and the number of FRP layers were selected as two main parameters in the test program. The major code models, namely Eurocode 2, the ACI-318 and the BS-8110 are used for evaluation of ultimate moment, and the results are also compared with experiments ones. Finite element analysis (FEA) using ANSYS software is presented to predict the load-deflection behavior of the RC beams, and completed with a numerical analysis to assess the interfacial shear stresses, focusing on debonding failure. The experimental results show an improvement in the ultimate load capacity of repaired RC beams with FRP ranging from 13% to 100%, with lower mid-span deflections ranging from 15% to 35% as compared to the control beam (without FRP). On the other hand, the major code models could not accurately predict the moment capacity of RC beams strengthened with FRP sheets/laminates, with a gap closer to 1.40. Moreover, the numerical FEA predictions show a good agreement in the load-deflection response for all tested beams. Also, the numerical analysis results indicate that the shear stresses rise with the number of FRP sheets layers.

Experimental and Numerical Investigation of Residual Stresses in Incremental Forming

Double Sided Incremental Forming (DSIF) is gaining importance over Single Point Incremental Forming (SPIF) due to its ability to form complex geometries and the capability to obtain better accuracies. In the present work, residual stresses are measured in pyramidal components formed using SPIF, DSIF using X-ray diffraction technique. Residual stress development mechanism during SPIF and DSIF is studied using Finite Element Analysis (FEA). Stress development along circumferential and meridional directions are explained using bending and unbending of sheet material taking place around forming tool. It is observed that the residual stresses are compressive on the outer surface and tensile on the inner surface of sheet in both circumferential and meridional directions. In DSIF, supporting tool restricts the unbending of sheet causing the residual stresses to be less compressive on the outer surface and less tensile on the inner surface compared to SPIF. It is also observed that with an increase in tool diameter, spring back increased, hence, meridional residual stress on the outer surface became more compressive and circumferential residual stress on the inner surface became more tensile. Residual stresses in ISF are compared with FEA predictions of conventional stamping process.

Performance of axially-loaded concrete-filled steel tubular circular columns using ultra-high strength concrete

Finite element analysis (FEA) is conducted to investigate the structural behaviour of axially-loaded ultra-high strength concrete (UHSC) filled steel tube circular columns in this paper. A new stress-strain model of UHSC confined by circular steel tube is proposed by recalibrating the existing normal strength concrete constitutive model. The comparison between FEA predictions and test results indicates that the proposed FEA model is able to capture the brittleness characteristic of UHSC in circular CFST columns accurately. Based on the proposed FEA model, the structural performance of axially-loaded UHSC filled steel tube circular columns, including load versus deformation relationship, stress development, confinement effect and preliminary optimized design, are analysed and discussed. Finally, a parametric study is conducted to investigate the influence of key parameters on the load-deformation curve and strength utilization index of axially-loaded UHSC filled steel tube circular column during the entire loading process.

In-plane shear testing of unreinforced masonry walls and comparison with FEA and NZSEE predictions

The present study was conducted to investigate the global and local in-plane response of perforated URM walls under earthquake loading, based on observations of damage from previous earthquakes. To do so, full-scale cyclic in-plane testing of URM walls with an arched opening which were designed to represent walls in heritage URM structures in Australia was performed. The study investigated the behaviour of both pier and spandrel elements within the walls. Emphasis was also given to the position of walls within a multi-storey building by varying the pre-compression loads (representing gravity loads) on the walls. The tested walls were then simulated using nonlinear finite element analyses (FEA) where simplified micro-modelling (crack-shear-crush) approaches were used to analyse the wall behaviour. Finally, the shear capacities and the failure modes of the walls obtained from the experimental tests and FE analyses were compared to the proposed New Zealand Society for Earthquake Engineering (NZSEE) predictions.

In-plane Shear Testing of Unreinforced Masonry Walls and Comparison with FEA and NZSEE Predictions

The present study was conducted to investigate the global and local in-plane response of perforated URM walls under earthquake loading, based on observations of damage from previous earthquakes. To do so, full-scale cyclic in-plane testing of URM walls with an arched opening which were designed to represent walls in heritage URM structures in Australia was performed. The study investigated the behaviour of both pier and spandrel elements within the walls. Emphasis was also given to the position of walls within a multi-storey building by varying the pre-compression loads (representing gravity loads) on the walls. The tested walls were then simulated using nonlinear finite element analyses (FEA) where simplified micro-modelling (crack-shear-crush) approaches were used to analyse the wall behaviour. Finally, the shear capacities and the failure modes of the walls obtained from the experimental tests and FE analyses were compared to the proposed New Zealand Society for Earthquake Engineering (NZSEE) predictions.

Introducing an easy-install precast concrete beam-to-column connection strengthened by steel box and peripheral plates

Precast reinforced concrete frame is one of the industrialized building systems (IBS)s which assembling limitation in its precast beam-to-column connection (PBC) causes many problems and leads to design of pinned connections inappropriate for moment resisting frames (MRF)s in high seismic zones.Previous PBCs for MRFs in precast reinforced concrete structures (PRCS)s are classified in two “dry” and “semi-monolithic” connections. Despite of the easy installation procedures, most of dry connections have not showed acceptable performance in ductility and energy dissipation. On the other hand, semi-monolithic connections require long pending time for casting and scaffolding in construction site and lead to reinforcement congestion in beam-column joint. Also most of the precast beams in the both approaches have not appropriate bearing surface to create desirable beam-to-slab connection condition.The current study proposes a simple and efficient precast connection with suitable conditions for beam-to-slab connection, which could be also used in MRFs, through combining two approaches. To accomplish this, two external beam-to-column joints on 2/3 scale were designed in precast and in-situ forms. In the following, the proposed PBC connection was compared using the reverse cyclic test with the in-situ beam-to-column connection (IBC). The test results demonstrated that the proposed PBC had a higher load-carrying capacity, energy dissipation and ductility than those of the equivalent IBC and met all the seismic requirements of ACI374.1-05 criteria for moment resistant connections. Finally, the connections were simulated with finite element method (FEM) in ATENA software to develop the test results. At this stage, the finite element analysis predictions for load-carrying capacity, cracking pattern and strain values indicated good conformance with the test results and then the effect of parameters such as compressive strength of concrete, axial force of column and beam end plates length were investigated. An increase in concrete strength and axial force caused to more load-carrying capacity and strength degradation in the beam-column joints, respectively.

Stationary complementary energy high-order theory for the static analysis of beams

A high-order theory is developed for the analysis of beams with general mono-symmetric cross-sections. The theory represents the nonlinear distribution of the longitudinal normal stress across the section depth by a polynomial series expansion up to any order as specified by the analyst. The corresponding shear and transverse normal stresses are obtained by satisfying the 2D infinitesimal stress-flow equilibrium conditions. The resulting statically admissible stress fields are then used in conjunction with the principle of stationary complementary strain energy to formulate the governing compatibility equations and boundary conditions. Closed form solutions are then developed for general loading and boundary conditions. Comparisons with the theory of elasticity and 3D finite element analysis predictions showcase the ability of the present theory to naturally capture shear deformation effects, transverse normal stress effects, nonlinear longitudinal normal stress distributions in deep beams, as well as the effect of support height. Unlike conventional beam solutions that are based on postulated kinematic assumptions, which tend to converge to the displacement response from below, the present theory avoids introducing any kinematic assumptions and is shown to converge to the solution from above. The theory is applicable to beams with doubly symmetric or mono-symmetric cross-sections, with isotropic or orthotropic materials, and subjected to general loading and boundary conditions. The theory is shown to offer advantages compared to other theories when modelling deep beams and/or beams with supports that are offset from the centroidal axis.

Displacement response of femur with various deformity angles under vertical load: FEA and experiment

Osteogenesis Imperfecta (OI) is a disease that affect the bone in terms of deformity and brittleness. It is known that after certain deformation angles, OI bone cannot sustain the excessive stress that resulting to bone fracture. Although several studies have been undertaken to analyse the fracture prediction on OI bone due to deformity angles using finite element analysis, however none of them has validated experimentally. Hence, the main objective of this study was to investigate the validity of finite element analysis in predicting the fracture risk of OI-affected femur. For experimental works, the bone specimens were prepared using polylactic acid material through Fuse Deposition Material method at 15°, 20° and 25°deformation angles. Findings of this study show a promising result as the deformation response for the FEA was agreed to experimental result. Hence, it proves that prediction of finite element analysis on bone fracture risk of OI is acceptable. This study also found that femur bone with 25° deformation angle tend to fracture under minimum load. Therefore, patients that have femur bone at 25°deformation angles should be advised to undergo surgical intervention.

Two-Sided Topological Architecture on a Monolithic Flexible Substrate for Ultrasensitive Strain Sensors.

Flexible ultrasensitive strain sensors are highly desirable in view of their widespread applications in wearable electronics, health monitoring systems, and smart robots, where subtle strain detection is required. However, traditional fabrication of such sensors was done to prepare sensitive layers on bare or single-sided structural substrates, leading to limited sensitivity. Herein, a stretchable resistive-type strain sensor was demonstrated by self-assembling conductive networks onto a monolithic polydimethylsiloxane substrate with a two-sided topological design, for example, a sinusoid/auxetic binary architecture. The sensitivity of the obtained sensor was greatly improved by 22-fold as compared to the traditional counterpart with a bare substrate. The remarkably good agreement between the experimental results and finite element analysis predictions confirmed that the superior sensitivity is a synergistic effect of local strain enhancement derived from the topological structure on the foreside and an additional strain concentration and a reduced Poisson's ratio from the auxetic arrays on the backside. Furthermore, this sensor can withstand an extreme mechanical force (>750 N) because of the shear stiffening characteristic of the auxetic structure. Benefiting from the characteristics of ultrahigh sensitivity (gauge factor ∼1744 at 5%), low detection limit (<0.05%), and long-term durability (>500 loading cycles), this as-prepared sensor shows promise in practical applications of high-performance wearable electronics.

Prediction of displacement in the equine third metacarpal bone using a neural network prediction algorithm

Bone is a nonlinear, inhomogeneous and anisotropic material. To predict the behavior of bones expert systems are employed to reduce the computational cost and to enhance the accuracy of simulations. In this study, an artificial neural network (ANN) was used for the prediction of displacement in long bones followed by ex-vivo experiments. Three hydrated third metacarpal bones (MC3) from 3 thoroughbred horses were used in the experiments. A set of strain gauges were distributed around the midshaft of the bones. These bones were then loaded in compression in an MTS machine. The recordings of strains, load, load exposure time, and displacement were used as ANN input parameters. The ANN which was trained using 3,250 experimental data points from two bones predicted the displacement of the third bone (R2 ≥ 0.98). It was suggested that the ANN should be trained using noisy data points. The proposed modification in the training algorithm makes the ANN very robust against noisy inputs measurements. The performance of the ANN was evaluated in response to changes in the number of input data points and then by assuming a lack of strain data. A finite element analysis (FEA) was conducted to replicate one cycle of force-displacement experimental data (to gain the same accuracy produced by the ANN). The comparison of FEA and ANN displacement predictions indicates that the ANN produced a satisfactory outcome within a couple of seconds, while FEA required more than 160 times as long to solve the same model (CPU time: 5 h and 30 min).