Eight-node Solid Elements Research Articles

Uncertainty Analysis of Tensile Strength of Scarf Adhesive Joints Using Numerical Method

This study uses three-dimensional finite element (FE) analysis to investigate stress distribution and fatigue strength in adhesive scarf joints, which are complex due to their oblique geometry and varying material properties. ANSYS was used to model stress components within the adhesive and at the adhesive-adherent interface. The FE models, created with eight-node solid elements, utilized fine meshing to ensure accurate stress representation. A mesh size of 0.025 mm was optimal. The models, assuming linearly elastic materials, were validated by comparing simulated deformations with experimental results. Findings enhance understanding of local stress states, improving adhesive joint design reliability. Key Words: Adhesive scarf joints, finite element analysis, stress distribution, fatigue strength, ANSYS,

НЕЛИНЕЙНЫЙ АНАЛИЗ МАССИВНЫХ ЖЕЛЕЗОБЕТОННЫХ КОНСТРУКЦИЙ С УЧЕТОМ ТРЕЩИНООБРАЗОВАНИЯ

A finite element method, as well as the algorithm and the program for solid reinforced concrete structures analysis have been developed, taking into account plastic deformations of concrete. A modified Willam & Warnke failure criterion was used, supplemented by a flow criterion. Two models of volumetric deformation of concrete have been developed: an elastic model under brittle fracture and an ideal elastic-plastic model. An eight-node solid finite element with linear approximation of displacement functions, which implements the deformation models above mentioned, is constructed. This finite element is adapted to the PRINS computational software, and as part of this program it can be used for physically nonlinear analysis of building structures containing three-dimensional reinforced concrete elements. Modern building codes prescribe to carry out calculations of concrete and reinforced concrete structures in a nonlinear formulation, taking into account the real properties of concrete and reinforcement. To verify the developed finite element, a series of test calculations of a beam in the condition of pure bending was carried out. Comparison of the calculation results with experimental data confirmed the high accuracy and reliability of the results obtained.

Three-dimensional decoupled modeling on curing simulation of composite laminated plates with damage

The curing simulation problem of composite laminated plates with damage is investigated based on a three-dimensional decoupled model, considering the thermo-mechanical interaction between the composite laminated plates and tool. The composite laminated plates and tool are simulated by the extended layerwise method (XLWM) and eight-node solid element, respectively. The cure kinetics is employed to simulate the curing process. In the numerical examples, the proposed method is validated by using the commercial softwares. The effects of delamination and transverse cracks on the curing process of composite laminates are investigated, together with the interaction between the composite laminate plates and tool.

The effect of soil improvement and auxiliary rails at railway track transition zones

Railway track transition zones are areas where there is a sudden change in the track-ground structure. They include changes between ballasted and slab track, bridge approaches, and tunnel entry/exits. They are often the location of rapid track deterioration, and therefore this paper investigates the use of auxiliary rails and soil improvement to minimise train-track-ground dynamic effects. To do so, a 3D finite element model is developed using eight-node solid elements and a perfectly matched layer absorbing boundary condition. A moving train load is simulated using a sprung mass model to represent train-track interaction. After presenting the model, it is validated against field data collected on both a plain line and at a transition zone. Once validated, a sensitivity study is performed into auxiliary rails and soil improvement. It is found that auxiliary rails can improve the dynamic characteristics of the track across the transition, and that more widely spaced auxiliary rails provide greater benefit compared to closely spaced ones. Regarding soil improvement, a large benefit is found, and for the material properties under investigation, the effect of soil stiffening is greater than using auxiliary rails.

FINITE ELEMENT ANALYSIS OF CELLULAR CIRCLE COFFERDAM FOR WET SOIL

This paper presented nonlinear finite element analysis to predict the load deflection behavior of circular cell cofferdam under lateral load by using ANSYS (Analysis System) (version 12.1) computer program. Eight-node solid element (SOLID 45) has been used to model filling soil, and the same element by using overlap and glue technique to model steel sheet pile of cofferdam. The bond between steel sheet pile and filling soil has been modeled by using nodes merge.

A three-dimensional numerical model for delaminations, transverse crack or debonding in composite sandwich plates with piezoelectric sensors

An Extended Layerwise/Solid-Element (XLW/SE) method is developed based on the Extended Layerwise method (XLWM) and eight-node solid element method for the static analysis of damaged composite sandwich structures with piezoelectric sensor. In this method, the XLWM is used to model the facesheets and piezoelectric sensors, and the eight-node solid element is used for the lattice. Based on the equilibrium conditions of displacement and internal force of the overlapped joints at the facesheet/sensors and facesheet/lattice interfaces, the general governing equation is established. In the numerical examples, the proposed method is verified by comparing with the 3D elasticity model developed in the commercial finite element software, and composite sandwich plates with delamination and/or transverse crack and/or debonding are analyzed.

Numerical comparison between Hashin and Chang-Chang failure criteria in terms of inter-laminar damage behavior of laminated composite

In this paper, a general three-dimensional finite element model composed of eight-node three-dimension cohesive elements and eight-node solid elements with reduced integration for low-velocity impact analysis of composite materials is established. Firstly, the continuum damage mechanics is applied to simulate the initiation and evolution of the intra-laminar damage. Based on cohesive zone model, the cohesive elements are inserted between layers to predict the inter-laminar damage. Three failure criteria, including 2D Hashin, 3D Hashin and Chang-Chang criteria, are coded in VUMAT and are implemented in ABAQUS/Explicit. The numerical results of energy time curves, force time curves, force displacement curves and damage distribution under three impact energies (7.35 J, 11.03 J and 14.7 J) are in good agreement with previously published data in literature, which indicates that the finite element model is suitable for studying the mechanical response and damage distribution of composites laminates subjected to low-velocity impact. Moreover, the influence of stacking sequence and friction coefficient on mechanical response and damage distribution is analyzed. It is concluded that the composite laminate with a stacking sequence of [45°/0°/−45°/90°]S can reduce the area of damage region compared to [0°/90°]2S because the ±45° layer can improve the shear resistance of composite laminate. Also, the computation accuracy will be the best when the friction coefficient is adopted between 0.5 and 0.7.

Dynamic thermomechanical analysis on composite sandwich plates with damage

The dynamic thermomechanical analysis on composite sandwich plates with damage is investigated in this paper. A thermomechanical extended layerwise/soild-element (TELW/SE) method is developed for sandwich plates. In the TELW/SE method, the thermomechanical extended layerwise theory is used to model the behavior of the laminated composite facesheets, while the thermomechanical eight-node solid element is employed to discretize the cores. The total governing equations are assembled by using the interface conditions, to ensure the compatibility of displacements and temperature, and the equilibrium of internal force. In the numerical examples, the dynamic thermomechanical analysis is carried out for the sandwich plates with one or two layer honeycombs cores, taking the delaminations, transverse crack and debonding at core/facesheets interface into account. The proposed method is validated by using three-dimensional elastic models developed in commercial finite element softwares Comsol and Abaqus, and good agreement is achieved. Several typical damage in composite sandwich plates can be described finely in the proposed method.

Estudo de deslocamentos em placas utilizando um elemento sólido de baixa ordem enriquecido com modos incompatíveis

The work proposes to study the displacement in plates, characteristics of geometry and diverse loads. The computational implementation of an 8-node hexahedral solid finite element is performed. After that, this element is enhanced through incompatible modes in order to improve the performance of the element in situations of multiaxial stresses, commonly present on plates. Then, we perform comparative analyzes with the purpose of studying the performance of the developed algorithm and compare its results with the final values of analyzes made by other authors, and with the results obtained by the modeling of the plates in commercial software. The analyzes take place in the static, linear and elastic range. It has been found that the enrichment of the low-order eight-node hexahedral solid element significantly improves its performance in plate analyzes, making it a viable alternative to the application.

Study of Direct Finite Element Method of Analysing Soil–Structure Interaction in a Simply Supported Railway Bridge Subjected to Resonance

This paper presents the dynamic soil–bridge interaction under high-speed railway lines, under different soil stiffness conditions. Starting from the analysis of a simply supported Euler–Bernoulli beam model subjected to moving loads, a three-dimensional multi-body (soil–abutment–bridge–ballast–sleeper–rail) model formulated in the time domain to study the vibrations induced due to the passage of moving concentrated loads was analysed using the direct finite element method of soil–structure interaction analysis. The high-speed train was considered to be a set of concentrated loads, the rail was modelled as a Euler–Bernoulli beam (frame element), and the sleepers, ballast, bridge, abutments and soil were modelled using eight-node solid (brick) elements. Layered soil stratum’s effects on the dynamic response of the bridge deck and variation of stresses were studied. From this study, it was observed that the direct method of FE analysis can be an effective tool to solve the complex dynamic soil–structure interaction problems.

Updated Lagrangian formulations of two hexahedral elements with rotational DOFs

Updated Lagrangian formulations of two eight-node hexahedral solid elements with rotational degrees of freedom (DOFs) are developed to analyse geometrically nonlinear large deflection problems. These two elements are based on the so-called Space Fibre Rotation (SFR) concept that considers fictive small rotations of a nodal fibre within the element to enrich the displacement vector approximation of low-order finite elements. The validity and efficiency of the proposed formulations are demonstrated by solving several nonlinear large deflection benchmarks and the obtained results show a much better accuracy than those based on the total Lagrangian approach.

Numerical investigation on the forming behaviour of stainless/carbon steel bimetal composite

Bimetal composites have wide applications due to their excellent overall performance and relatively low comprehensive cost. The aim of this study is to investigate the forming behaviour of stainless/carbon steel bimetal composite during stamping by finite element method (FEM). In this work, the bonding interface of bimetal composite sheet was assumed to be perfect without delamination during the plastic forming process for simplicity. Uniaxial tensile tests on base metal (carbon steel) and compositing metal (stainless steel) were first carried out, respectively, in order to obtain the tensile properties of each of the component materials required in the forming simulation. Processing variables, including the layer stacking sequence, relative thickness ratios of two layers and friction were considered, and their effects on the distributions of circumferential stress and thickness strain were analysed. The bimetal composite sheet was set as the eight-node solid elements in the developed FEM model, which is effective for evaluating the distributions of circumferential stress and thickness strain, and predicting the high-risk region of necking during the stamping of bimetal composites. The simulation results can be used as an evaluation indicator of the capability of forming machine to ensure the bimetal composite can be safely formed.

Static response and free vibration analysis of the composite sandwich structures with multi-layer cores

The Layerwise/Solid-Element (LW/SE) method, which was developed based on the layerwise theory and the eight-noded solid element for the laminated composite stiffened plates and sandwich plates in the previous works [1–3], is extended to the static response and free vibration analysis of the composite sandwich structures with multi-layer cores. In the LW/SE method, the layerwise theory is used to model the behavior of the laminated composite facesheets while the eight-noded solid element is employed to discretize the cores. The total governing equations of the composite sandwich plates are assembled by using the compatibility conditions to ensure the compatibility of displacements and the equilibrium conditions to ensure the equilibrium of internal force at the interface between facesheets and cores. In the numerical examples, the static analysis and free vibration analysis of the composite sandwich plates are investigated for the sandwich plates with double-layer honeycombs and pyramidal lattice cores. The proposed method is validated by using the 3D elastic models developed in MSC.Patran/Nastran code. Two kinds of local models of the sandwich plates with double-layer honeycombs are presented for the local response problems to reduce the computational cost in the case of guarantee analysis accuracy of the local response.

Nonlinear Modeling and Identification of an Aluminum Honeycomb Panel with Multiple Bolts

This paper focuses on the nonlinear dynamics modeling and parameter identification of an Aluminum Honeycomb Panel (AHP) with multiple bolted joints. Finite element method using eight-node solid elements is exploited to model the panel and the bolted connection interface as a homogeneous, isotropic plate and as a thin layer of nonlinear elastic-plastic material, respectively. The material properties of a thin layer are defined by a bilinear elastic plastic model, which can describe the energy dissipation and softening phenomena in the bolted joints under nonlinear states. Experimental tests at low and high excitation levels are performed to reveal the dynamic characteristics of the bolted structure. In particular, the linear material parameters of the panel are identified via experimental tests at low excitation levels, whereas the nonlinear material parameters of the thin layer are updated by using the genetic algorithm to minimize the residual error between the measured and the simulation data at a high excitation level. It is demonstrated by comparing the frequency responses of the updated FEM and the experimental system that the thin layer of bilinear elastic-plastic material is very effective for modeling the nonlinear joint interface of the assembled structure with multiple bolts.

Seismic Damage in Shear Wall-Slab Junction in RC Buildings

Nonlinear time history analyses, under different levels of recorded earthquake ground motion, are carried out using the computer program ABAQUS to study the seismic damage in shear wall – slab junction of an RC wall-frame building. The beams, columns, shear walls and slabs are discretized with eight-noded solid elements. The incurred cumulative damage is determined at various locations for all the three models. It is observed that the damage gets primarily concentrated at the wall – slab junction region with increasing levels of ground motion.

Experimental investigation on flexural behavior of concrete-filled pentagonal flange beam under concentrated loading

The flexural behavior of simply supported concrete-filled pentagonal flange beams (CFPFBs) under mid-span loading is experimentally and numerically investigated. There are two CFPFB specimens tested to failure under static load condition to determine the beam flexural capacity. One of the test specimens is designed with a pair of transverse stiffener at mid-span while the other is without any stiffener to resist the load. Both the test specimens have identical geometrical and material properties. From the experimental results, the flexural capacity of the specimen with stiffener is found to be 10% higher than that of the specimen without stiffener. The failure behavior shows the importance of transverse stiffener to enhance the ultimate flexural capacity and to avoid the localized web distortion of the beam. In the numerical study based on finite element (FE) analysis, the concrete and steel materials are modeled using the eight-node solid and four-node shell element respectively. A comparison of the ultimate capacity of the CFPFBs with and without stiffener reveals that the FE models simulate very well the flexural behavior of the test specimens and the difference of maximum load is found to be less than 10%.

Seismic response analysis of an oil storage tank using Lagrangian fluid elements

Three-dimensional Lagrangian fluid finite element is applied to seismic response analysis of an oil storage tank with a floating roof. The fluid element utilized in the present analysis is formulated based on the displacement finite element method considering only volumetric elasticity and its element stiffness matrix is derived by using one-point integration method in order to avoid volumetric locking. The method usually adds a rotational penalty stiffness to satisfy the irrotational condition for fluid motion and modifies element mass matrices through the projected mass method to suppress spurious hourglass-mode appeared in compensation for one-point integration. In the fluid element utilized in the present paper, a small hourglass stiffness is employed. The fluid and structure domains for the objective oil storage tank are modeled by eight-node solid elements and four-node shell elements, respectively, and the transient response of the floating roof structure or the free surface are evaluated by implicit direct time integration method. The results of seismic response analyses are compared with those by other method and the validation of the present analysis using three-dimensional Lagrangian fluid finite elements is shown.

Numerical Modeling of Steel Fiber-Reinforced Beam

Steel fibre reinforced concrete is emerging very popular and attractive material in structural engineering because of its enhanced mechanical performance as compared to conventional concrete. It is well established that one of the important properties of steel fibre reinforced concrete (SFRC) is its superior resistance to cracking and crack propagation. Additionally, incorporation of fibres in the concrete enhances the compressive, tensile and shear strengths, flexural toughness, durability and resistance to impact. The mechanical properties of fibre reinforced concrete depend on the type and specification of fibres. In this paper numerical investigation of SFRC beam using ANSYS is presented. The analysis was conducted till the ultimate failure cracks. Eight-noded solid brick elements were used to model the concrete. Internal reinforcement was modeled by using 3D spar elements. It has been observed the results from the finite element failure behavior indicates a good agreement with the experimental failure behavior.

A layerwise/solid-element method of the linear static and free vibration analysis for the composite sandwich plates

In the traditional analysis schemes of the composite sandwich structures the core is firstly simplified as an equivalent anisotropic material and then modeled by the plates and shells theories. Its main disadvantage is that the equivalent core will result in large equivalent error especially in the key area and the thick core will further reduce the analysis accuracy of the plates and shells theories. Therefore, a layerwise/solid-element method (LW/SE) is proposed in this paper, in which the layerwise theory is used to model the behavior of the composite laminated facesheets while the eight-noded solid element is employed to discretize the core. Three models, the full model, the local model and the equivalent model, are presented to model the core. Several numerical examples are investigated and the static analysis and free vibration analysis of the composite sandwich plates are tested. The results of proposed method are in good agreement with those of 3D finite element model. A detailed comparative study is conducted to investigate the performance of three modeling schemes for static analysis and free vibration analysis problems.

A layerwise/solid-element method for the composite stiffened laminated cylindrical shell structures

For the composite stiffened laminated cylindrical shells, a layerwise/solid-element (LW/SE) method was established based the layerwise theory and the finite element method (FEM). In the present LW/SE method, the layerwise theory was used to model the behavior of the composite laminated cylindrical shells, and the eight-noded solid element is employed to discrete the stiffeners. And then, based on the governing equations of the shells and stiffeners, governing equation of the composite stiffened laminated cylindrical shells was assembled by using the compatibility conditions to ensure the compatibility of displacements at the interface between shells and stiffeners.To demonstrate the excellent predictive capability of this LW/SE method, several numerical examples were carried out to investigate the problem of static analysis and free vibration analysis for the composite stiffened laminated cylindrical shells. Good agreement had been achieved between the predictions and the results of finite element code MSC.Nastran. Furthermore, an analysis model for the composite shells structural systems reinforced by complex stiffeners, which is similar to the geometric form of the aircraft semi-monocoque fuselage structure, was developed based on the present coupling method. And the static response, natural frequencies and vibration modes were obtained.