Present Finite Element Model Research Articles

A Basic Numerical Peening Indentation Model with Geometric Indenter Based on Dynamic Impact Analysis

As shot peening is widely used to improve the crack resistance of various metals, it isimportant to have an accurate method to calculate the compressive residual stress produced by thisprocess. To this end, this paper presents a finite element (FE) model that includes an indenterdesigned from a dent profile. The results of compressive residual stress obtained by using thisindenter model and a normal shot impact model are compared. The indentation FE solution with anunmodified indenter is close to that obtained using the rigid shot (RS) impact model. The solutionfor the indentation FE model with a modified indenter closely matches that for an elasticdeformable shot (EDS) impact model. These results confirm the effectiveness of the indentation FEmodel based on the dent profile. This model can replace the present impact FE models to calculatethe compressive residual stress produced by shot peening.

Finite element formulation for active functionally graded thin-walled structures

For the analysis and design process of smart structures with integrated piezoelectric patches, the finite element method provides an effective simulation approach. In this paper, an attempt on modeling and simulation of the behavior of hybrid active structures is carried out using developed Kirchhoff-type-four-node shell element.The finite element results are compared with reference solutions taking into account the electromechanical responses of smart structures with various geometries, and the results show very high agreement. The main aspect of the application of the proposed element is to predict the behavior of FGM shells containing piezoelectric layers. A set of numerical analyses is performed in order to highlight the applicability and effectiveness of the present finite element model, notably for smart FGM structures. A comprehensive parametric study is conducted to show the influence of material composition, the placement and the thickness of the piezoelectric layers on the deformation of the laminated structure.

A compression shear mixed finite element model for vibration and damping analysis of viscoelastic sandwich structures

A finite element model is developed to investigate the vibration and damping of elastic–viscoelastic–elastic sandwich beams. Two energy dissipation mechanisms, namely the shear and compression damping, are combined in the finite element model. Numerical examples are provided to verify the finite element model. The vibration and damping characteristics of the viscoelastic sandwich beams are investigated in detail. The numerical results show that the present finite element model has a good accuracy in predicting the natural frequencies and loss factors of viscoelastic sandwich beam structures. Moreover, it shows good applicability for both the thin and relatively thick sandwich beams. Its comprehensive performance is much better than the traditional shear and compression damping models. The effect of the viscoelastic material and geometrical parameters on the natural frequencies and loss factors of elastic–viscoelastic–elastic sandwich beam is studied as well. The results obtained have some significance in engineering application.

Structural behavior of tubular X-joints strengthened with collar plate under axially compressive load at elevated temperatures

This paper investigates elevated temperature resistance of circular hollow section X-joints reinforced with collar plates subjected to brace compression. A finite element (FE) model was developed and the results were validated against the data available from seven experimental tests. Also, the results of the present FE model were compared with the numerical results of other researchers. Afterwards, several 3-D FE-models of the collar plate reinforced X-joints were generated to investigate the effect of joint geometry and collar plate size on the initial stiffness, ultimate strength, and failure mechanisms at different elevated temperatures. Results showed that the use of the collar plates in X-joints at elevated temperatures (200 °C, 400 °C, and 600 °C, and 800 °C) leads to the significant increase of the initial stiffness and ultimate strength. Also, the increase of the plate length results in the less reduction in ultimate strength, at all elevated temperatures. But, the effect of the plate thickness on the reduction factor can be ignored. Moreover, the decrease of the β in the plate reinforced X-joints at elevated temperature can lead to the shifting of the maximum plastic strain from joint intersection to the toe of the weld joining the collar plate to chord member. The parametric investigation was followed by the non-linear regression analysis to propose a parametric equation for determining the ultimate strength of the collar plate reinforced X-joints under brace compression at elevated temperatures.

An Accurate Analysis for Sandwich Steel Beams with Graded Corrugated Core Under Dynamic Impulse

This paper addresses the dynamic loading characteristics of the shock tube onto sandwich steel beams as an efficient and accurate alternative to time consuming and complicated fluid structure interaction using finite element modeling. The corrugated sandwich steel beam consists of top and bottom flat substrates of steel 1018 and corrugated cores of steel 1008. The corrugated core layers are arranged with non-uniform thicknesses thus making sandwich beam graded. This sandwich beam is analogous to a steel beam with web and flanges. Substrates correspond to flanges and cores to web. The stress–strain relations of steel 1018 at high strain rates are measured using the split-Hopkinson pressure. Both carbon steels are assumed to follow bilinear strain hardening and strain rate-dependence. The present finite element modeling procedure with an improved dynamic impulse loading assumption is validated with a set of shock tube experiments, and it provides excellent correlation based on Russell error estimation with the test results. Four corrugated graded steel core arrangements are taken into account for core design parameters in order to maximize mitigation of blast load effects onto the structure. In addition, numerical study of four corrugated steel core placed in a reverse order is done using the validated finite element model. The dynamic behavior of the reversed steel core arrangement is compared with the normal core arrangement for deflections, contact force between support and specimen and plastic energy absorption.

Numerical simulation of high-temperature thermal contact resistance and its reduction mechanism

High-temperature thermal contact resistance (TCR) plays an important role in heat-pipe-cooled thermal protection structures due to the existence of contact interface between the embedded heat pipe and the heat resistive structure, and the reduction mechanism of thermal contact resistance is of special interests in the design of such structures. The present paper proposed a finite element model of the high-temperature thermal contact resistance based on the multi-point contact model with the consideration of temperature-dependent material properties, heat radiation through the cavities at the interface and the effect of thermal interface material (TIM), and the geometry parameters of the finite element model are determined by simple surface roughness test and experimental data fitting. The experimental results of high-temperature thermal contact resistance between superalloy GH600 and C/C composite material are employed to validate the present finite element model. The effect of the crucial parameters on the thermal contact resistance with and without TIM are also investigated with the proposed finite element model.

Efficient 2D thermo-mechanical analysis of composites and sandwich laminates

ABSTRACTThe static behavior of composites and sandwich plates in thermo-mechanical environment is investigated by a two dimensional (2D) FE model. An efficient higher-order zig-zag theory (HOZT) considering actual through-thickness temperature profile and a least square error (LSE) method to accurately predict the inter-laminar stresses is implemented in this model. The in-plane displacement field is obtained by superposing a cubically varying global displacement field on a zig-zag displacement field having different slopes at each layer. This plate theory represents parabolic through thickness variation of transverse shear stresses, which satisfy the inter-laminar continuity at the layer interfaces and zero transverse shear stress conditions at the top and bottom of the plate. In the present 2D finite element (FE) model, the first derivatives of transverse displacement have been treated as independent variables to circumvent the problem of C1 continuity associated with the above plate theory (HOZT). The accurate through-thickness distribution of temperature is obtained by using a linear zig-zag thermal lamination theory proposed by the authors by using the thermal conduction properties of different constituent layers in the thickness direction. The LSE method is applied at the postprocessing stage to accurately calculate the inter-laminar stresses by the 3D equilibrium equations of the plate problem, after in-plane stresses are calculated. The proposed combined FE model (HOZT+LSE) is implemented to analyze the static behavior of laminated composites and sandwich plates subjected to thermo-mechanical loadings. Many new results are also presented that should be useful for the future reference.

Drop test simulation and validation of a full composite fuselage section of a regional aircraft

In the aircraft industry, the use of fiber reinforced materials for primary structural components over metallic parts has increased up to more than 50% in the recent years, because of their high strength and high modulus to weight ratios, high fatigue and corrosion resistance. Currently, the need of lowering weight and fuel consumption is pushing the world’s largest aircraft manufacturers in the design and building of structures entirely made of composites.Fuselage structure plays an important role in absorbing the kinetic energy during a crash. Through the deformation, crushing and damage of fuselage sub-floor structure, a survivable space inside the cabin area should be preserved during and after a crash impact in order to minimize the risk of passengers’ injuries.In this work, a Finite Element (FE) model of a full-scale 95% composites made fuselage section of a regional aircraft under vertical drop test is presented. The experiment, conducted by the Italian Aerospace Research Centre (CIRA) with an actual impact velocity of 9.14 m/s in according to the FAR/CS 25, has been numerically simulated. Two ATDs (Anthropomorphic Test Dummies), both 50th percentile, seats and belts have been modelled to reproduce the experimental setup. The results of the simulation, performed by using LS-DYNA® explicit FE code, have been validated by correlation with the experimental ones. Such comparisons highlight that a good agreement has been achieved.The presented FE model allows verifying the structural behavior under a dynamic load condition and also estimating the passive safety capabilities of the designed structure. Since the experiment is expensive and non-repeatable, a FE model can be used for Certification by Analysis purposes since, if established, it is able to virtually demonstrate the compliance to the airworthiness rules.

Free vibration analysis of Stiffened Laminated Plate using FEM

This paper presents the free vibration analysis of stiffened laminated plate using Finite element method. Stiffened laminated plate are commonly employed in the structures of many aerospace vehicles such as aircrafts, rockets, missiles, etc. Therefore it is necessary to determine the structural deformation and vibrational characteristics of such structures where it is desired to have high natural frequencies. The free vibration results obtained by the present finite element model are compared with previous results for the stiffened composite plate. The result shows that the present model for the stiffened plate gives quite accurate results. Effects of the eccentricity, orientation- symmetric and anti-symmetric, angle-ply and cross-ply and boundary condition are also investigated.

Fracture behavior of roll bonded Al-brass-Al multilayer composites – Concept of the maximum undamaged defect size (dmax)

Multilayer sandwich composites consisting of two skin metals and perforated interlayer are rapidly becoming a good substitute for metal structures, especially in the automobile industry. Their good mechanical properties including excellent fatigue and impact strength, as well as damage tolerance, are accomplished. In this study, aluminum-perforated brass-aluminum sandwich composites are fabricated using roll bonding technique. Samples were made at different surface roughness, and their bonding behavior is investigated using peel test. The fracture behavior under mode-I was investigated. The effect of surface roughness (two different sand paper grits 50 and 80) on the fracture energy of mode-I peeling failure is studied experimentally. It is found that, the peeling resistance increased with increasing the surface roughness. To simulate the progressive failure of this sandwich composite, 3-D finite element model is employed in the present work. Virtual-Crack-Closing-Technique (VCCT) debonding model has been adopted to predicate the peeling failure. The concept of the maximum size of undamaged defect (dmax) has been adopted to predict the effect surface roughness on peeling load numerically. The numerical and experimental results showed an agreement between them. Therefore, the present 3D finite element model can be considered as a good candidate to expect the peeling damage in sandwich composites.

Bending Analysis of a Filament-Wound Composite Tube

The aim of this paper is to present finite element model of a filament-wound composite tube subjected to three-point bending and bending in accordance with standard EN 15807:2011 (railway applications-pneumatic half couplings) along with its experimental verification. In the finite element model, composite reinforcement plies have been characterized by linear orthotropic material model, while rubber liners have been described by a two-parameter MooneyRivlin model. Force-displacement curves of three-point bending show fairly good agreement between simulation results and experimental data. Reaction forces of FE simulation and experiment of standard bending test are in good agreement.

An efficient materially nonlinear finite element model for reinforced concrete beams based on layered global-local kinematics

In this study, a finite element model with low degrees of freedom is presented for the materially nonlinear analysis of reinforced concrete (RC) beams. The kinematics considered for the RC beam is based on a layered global-local (LGL) theory. Unlike the classical one-dimensional (1D) beam kinematics (e.g. Euler–Bernoulli’s and Timoshenko’s beam theory), the effects of shear deformation and normal flexibility of the RC beams are considered in the formulation of the present LGL theory. No shear correction factor is needed in the present LGL theory. The LGL theory has only one extra displacement variable more than Timoshenko’s beam theory. Elastoplastic and fixed smeared crack models are considered for modeling the material nonlinearity of the reinforcing steels and cracked concrete, respectively. The results obtained from the present nonlinear finite element model are compared with experimental and numerical results. Comparisons show that the present model gives accurate results at a low computational cost.

Finite rotation three and four nodes shell elements for functionally graded carbon nanotubes-reinforced thin composite shells analysis

In this paper, we address the extension of the Kirchhoff shell model to non-linear analysis of functionally graded carbon nanotubes-reinforced thin composite shells (FG-CNTRCs). The present model can bring up two levels of analysis: geometrically non-linearities and nanostructures with the possibilities of two type of discretization. Either, three and four nodes finite shell elements are implemented to analyze as well as predict the non-linear bending behavior of FG-CNTRC shell structures. Uniform (UD) and three graded distributions of carbon nanotubes (CNTs) which are FG-V, FG-O and FG-X are considered. These distributions are uniaxially aligned in the axial direction of the shell and functionally graded along the thickness direction. The material properties of CNTs are estimated using the modified rule of mixture and the size dependence of these CNTs is taken into account via the introduction of some efficiency parameters. Three numerical examples of FG-CNTRC plates, hyperboloidal and cylindrical shells are presented to highlight the applicability and effectiveness of the present finite element model notably for thin structures. The effect of CNT profiles, CNT volume fractions and others geometrical parameters on non-linear behavior of such structures are also examined.

Modeling seismic response of a full-scale cold-formed steel-framed building

The objective of this paper is to present finite element modeling protocols and validation studies for the seismic response of a two-story cold-formed steel-framed building with oriented strand board sheathed shear walls. Recently, shake table testing of this building was completed by the authors. The building provides an archetype for modern details of cold-formed steel construction, and provides benchmarks for the seismic response of the building system, subsystem, and components. The seismic response of buildings framed from cold-formed steel has seen little study in comparison with efforts on isolated members and shear walls. Validated building-scale models are needed to expand our understanding of the seismic response of these systems. Finite element models corresponding to the archetype building during its various test phases are developed in OpenSees and detailed herein. For cold-formed steel framed buildings accurate seismic models require consideration of components beyond the isolated shear walls, e.g. the stiffness and capacity of the gravity framing is included in the model. Such decisions require model refinement beyond what is typically performed and details for completing this effort accurately and efficiently are described herein. In addition, nonstructural components, including exterior sheathing of the gravity framing, interior gypsum sheathing for the shear walls and gravity framing, and interior partition walls, are included in the building model based on nonlinear surrogate models that utilize experimental characterization of member-fastener-sheathing response. Comparisons between the developed models and testing for natural period, story drift, accelerations, and foundation hold-down forces validate the model. Performance of the tested archetype building is better than predicted by design or typical engineering assumptions. The model developed herein provides insights into how the building achieves its beneficial performance and will be used to further quantify the lateral resistance of each subsystem and the extent of their coupling. In addition, the protocols used to develop the model herein provide a first examination of the necessary modeling characteristics for wider archetype studies of cold-formed steel-framed buildings and the development and substantiation of seismic response modification coefficients.

Static capacity of tubular X-joints reinforced with collar plate subjected to brace compression

In the present paper, the effect of the collar plate on the static capacity of circular hollow section (CHS) X-joints under brace compression is experimentally and numerically investigated. For this aim, three X-joints reinforced with collar plate, with different values of β, and three corresponding unreinforced X-joints were tested. All of the details and results of the experimental tests are presented. The static behavior of the collar plate reinforced and un-reinforced X-joints is then evaluated from the load-displacement curves and deformed shapes. The compression between the results of reinforced and unreinforced X-joints shows that the collar plate can increase both of the initial stiffness and ultimate strength. Also, these beneficial effects of the collar plate are significant in all of the joints with small, intermediate, and big values of the brace-to-chord diameter ratio (β = 0.25, 0.54, 0.73). Moreover, the compression between deformed configurations shows that deformed shape of the reinforced specimens in the near joint intersection is more uniform than the deformed shape of the corresponding unreinforced specimens. Finally, finite element (FE) model is proposed. Results show that the present FE model can accurately predict the load-displacement curves and failure modes of the unreinforced and collar plate reinforced X-joints.

Coupled field modeling of E/M impedance of piezoelectric wafer active sensor for cataphoretic coating thickness measurement

The cataphoretic electro-coating is one of the most common methods that are used against corrosion as a primary coating layer. The cataphoretic electro-coating is commonly utilized technique especially in protecting of automobile components in automotive industry. This coating method has many advantages such as high corrosion resistance, ability of homogeneous and complete coating of components in any geometry, less pollution, and less risk of ignition. In this study, some specimens in the form of steel sheets coated by the cataphoretic electro-coating method are examined using electro-mechanical impedance spectroscopy (EMIS) method. One of the extensively employed sensor technologies has been permanently installed piezoelectric wafer active sensor (PWAS) for in situ continuous structural health monitoring (SHM). Using the transduction of ultrasonic elastic waves into voltage and vice versa, PWAS has been emerged as one of the major SHM sensing technologies. EMIS method has been utilized as a dynamic descriptor of PWAS and the structure on which it is bonded. EMIS of PWAS-structure couple is a high frequency local modal sensing technique by applying standing waves to indicate the response of the PWAS resonator by determining the resonance and anti-resonance frequencies. To simulate the actual EMIS measurements in the present work, two-dimensional and three-dimensional coupled field finite element models are created for both uncoated and coated steel plates in a commercial FEA software, ANSYS®. The EMIS values of the specimens in certain sizes and coated in different thickness are going to be simulated in broad-band of frequency spectra. The thickness of the coating layer and coating time are of paramount importance for the corrosion resistance. The coating layer thickness and the corresponding coating period will be optimized by analyses of the values obtained from the 2D and 3D EMIS simulations.

Mixed mode fracture behavior of concrete pavement containing RAP - 3D finite element analysis

Reclaimed asphalt pavement (RAP) is commonly used to improve the sustainability of asphalt concrete pavement. The main objective of the present work is to study the effect of RAP content on the mixed mode fracture behavior of concrete pavement numerically. An extended finite-element model was adopted to simulate crack growth under mixed mode loading. Semi-circular bending (SCB) specimen was used with three different crack geometries, namely inclined crack at the middle with different inclination angles (SCB-1) and vertical crack subjected to asymmetric three point bending. The effect of specimen geometry on the mode I fracture toughness (KIC) has been studied. The relationships between both RAP content and specimen geometry and mixed mode fracture toughness have been correlated. It is found that, the present 3D finite element model is a good candidate to predict the fracture behavior of concrete pavement containing RAP. To examine the reliability of each type of specimen geometry for predicting KIC, the maximum undamaged defect size (dmax) concept has been applied. It is found that, KIC predicted from the classical SCB (SCB-1) is reliable compared the values predicted from the other specimen geometries. Where the ratio of dmax to the maximum aggregate size (dmax/MAZ) ranged between unity and 2 in the case of SCB-1, it ranged between 5 and 14 in the other cases. Furthermore, the relationship between the present numerical values of KIC predicted from SCB-1 specimen and the flexural strength measured experimentally by Hossiney et al. (2010) is strongly correlated.

Parametric Studies and Numerical Analysis of Low Velocity Impact on Smart Hybrid Composite Laminates

To evaluate the effect of low velocity impact on composite plate using nonlinear explicit finite element software LS-DYNA software. The theoretical basis of the present finite element model is verified by analyzing impact-loaded laminated composite plate previously been studied through analytical. The study of hybrid composite plates are carried were the SMA (shape memory alloy) are used in between the plies to increase the resistance. Also parametric studies were done to find the importance of the Mesh. The present numerical approach is successfully demonstrated through comparisons between experimentally-measured and computed force-time histories for impact of carbon fiber-reinforce plastic (CFRP) plates. Parametric studies are also conducted by varying Mesh results obtained are correlated with the results in the published literature.

Safety assessment of the acrylic conical frustum viewport structure for a deep-sea manned submersible

ABSTRACTFor new manned submersibles to dive deep sea, the conical frustum windows need to be designed under external uniform pressure, not only based on the rule design method but also verified by numerical or experimental methods. In this paper, the contact finite element (FE) model is provided for the conical window and validated accordingly. Based on the presented FE model, the stress and deformation characteristics have been accomplished for the thick conical window and then the failure reasons and design criterion of acrylic plastics viewports are thoroughly investigated by comparing with the experiment data and those from some existed windows. Meanwhile, the structural characteristics especially for stress concentration have been exposed by numerical calculation. Finally, the failure of conical frustum viewport has been discussed totally referring to the existing design criteria and some principles for its optimal design have been proposed.

Effect of different temperature load on thermal postbuckling behaviour of functionally graded shallow curved shell panels

This article investigated numerically the postbuckling load parameter of the functionally graded shell panels under uniform and non-uniform thermal environment using nonlinear finite element method. The shell structure is assumed to be under three different thermal fields (uniform, linear and nonlinear temperature) across the panel thickness including the temperature dependent properties of each constituent. The effective material properties of the graded structure are evaluated using micromechanical rule (Voigt type) in association with the power-law distribution of the material constituent. Further, the graded shell panel model is evaluated mathematically based on the higher-order mid-plane theory and Green-Lagrange nonlinear strain deformation relations. The excess thermal distortion of the panel has been included by taking all the nonlinear higher-order strains. The equation of graded structure under the in-plane thermal load is derived by minimizing the total potential energy expression. The desired postbuckling load parameters are computed numerically with the help of a suitable MATLAB code using the present nonlinear finite element model in conjunction with the direct iterative method. The accuracy of the proposed numerical solutions have been checked initially and extended to show the significance of the proposed complex mathematical by solving various numerical examples for different geometrical and material parameters.