Dimensional Finite Element Simulations Research Articles

Finite element simulation of lamellar copper–silver composites

The mechanical behavior and texture evolution of lamellar Cu–Ag polycrystals are numerically investigated for a uniaxial compression test by three dimensional finite element simulations. In the representative volume element (RVE), the lamellar structure is generated inside the grains. A crystal plasticity material model for large deformations is used at each integration point. In this work, two cold drawn textured Cu–Ag polycrystals are modeled by periodic Voronoi tessellations in the finite element (FE) software ABAQUS. The FE calculations use periodic boundary conditions to simulate the mechanical behavior of the textured polycrystals. The numerical model is validated by experimental compression tests for a constant strain rate of 10-4s-1 at room temperature. The numerical results in terms of texture of each phase and the mechanical behavior have been compared with the experimental results.

FEM simulation of infeed rotary swaging with structured tools

Rotary swaging is an incremental cold forming process for rods and tubes. Infeed rotary swaging with structure in the reduction zone of the tools is investigated using a two dimensional finite element simulation. A few geometrical parameters are varied, for cosine and skew stairway shapes. The effective tool angle is kept constant. The influence is evaluated by the radial and axial process forces. Furthermore, the material flow is visualized by the neutral plane. The simulation results are quantitatively compared to each other to analyse the reaction force F A , which acts against the feeding force. Also, the results serve to find suitable geometries to be transferred to rotary swaging tools for practical application. It is shown that the shapes have a significant effect on the forces and the location of the neutral plane. Finally a first swaging tool is modified with an exemplary geometry for experimental investigations.

High quality factor, fully switchable terahertz superconducting metasurface

We present a complementary THz metasurface realised with Niobium thin film which displays a quality factor Q = 54 and a fully switchable behaviour as a function of the temperature. The switching behaviour and the high quality factor are due to a careful design of the metasurface aimed at maximising the ohmic losses when the Nb is above the critical temperature and minimising the radiative coupling. The superconductor allows the operation of the cavity with high Q and the use of inductive elements with a high aspect ratio. Comparison with three dimensional finite element simulations highlights the crucial role of the inductive elements and of the kinetic inductance of the Cooper pairs in achieving the high quality factor and the high field enhancement.

Experimental confirmation for the validity of Ritz method in structural dynamic analysis

The issue of Ritz vectors and their advantages is well-known in the field of structural engineering. This study deals with Ritz analysis and its experimental support. To that end, two different precast concrete molds were handled. Experiments were performed under vibration with the use of a computer-based data acquisition system. Transducers were used to measure displacement histories on the mold. Three dimensional finite element (3D FEM) simulation modeling of the concrete mold was carried out to obtain deflection histories on the mold. The computed displacement histories were compared with the experimental testing results. The comparisons show that the experimental and numerical results are compatible.

Numerical Prediction of Differences in Micromechanical Fracture Sequence in Notched and Un-Notched Wires for Civil Engineering Applications

The need to employ simulation-based investigations of fracture of civil engineering structures has been emphasised recently in literature. In this paper, three dimensional finite element simulations revealed that the cup and cone fracture process in channel-shaped notched wire for civil engineering applications begins with a slant fracture at the root of the outer edge of the channel-shaped notch and follows a slant to flat fracture sequence. These results demonstrate that the fracture origin in cup and cone fracture in notched wires for civil engineering applications does not necessarily begin with a flat fracture at the center of the wire and does not necessarily follows the flat to slant fracture sequence or propagation generally reported in literature. These results further demonstrate the need to employ simulation-based methodologies in conjunction with or as an alternative to purely experimental fractographic analysis for an accurate failure analysis of wires used for civil engineering applications.

Constraint analysis of defects in strength mismatched girth welds of (pressurized) pipe and Curved Wide Plate tensile test specimens

Curved Wide Plate (CWP) specimens are often considered to evaluate the tensile strain capacity of girth weld defected pipelines. However, to date no comparison has been made between the constraint in CWP and (pressurized) pipe specimens. This paper reports on the evaluation of the constraint through three dimensional finite element simulations. At first, it is observed that the internal pressure marginally increases the out-of-plane constraint. Second, the CWP specimens appear to closely represent the constraint in pipe specimens for homogeneous as well as strength mismatched situations. CWP specimens become increasingly conservative to pipe specimens with increasing defect dimensions.

Dynamic analysis of liquid storage tank under blast using coupled Euler–Lagrange formulation

A growing number of terror attacks all over the world have become a threat to the human civilization. In the last two decades, bomb blasts in crowded business areas, underground railway stations and busy roads have taken numerous lives and destroyed properties in different parts of the world. However, blast response of many important civil infrastructures has still not been well understood due to the complexities in their material behavior, loading and higher nonlinearities. One such example of important civil infrastructure is liquid storage tanks which are undividable parts of any society for storage of water, milk, liquid petroleum, chemicals in industries etc. Blast loading on liquid storage structures may lead to disaster due to water and milk crisis, health hazard owing to the spread of chemicals and fire hazard due to the spread of liquid fuel. Hence, understanding the dynamic behavior of liquid storage structures under blast loading through numerical simulations is of utmost importance. In the present study, three dimensional (3D) finite element (FE) simulations of a steel water storage tank for different tank aspect ratios, percentages of water stored in the tank, tank wall thicknesses, boundary conditions at the bottom of the tank and magnitudes of blast loading have been performed using the FE software Abaqus. The coupled Euler–Lagrange (CEL) formulation in Abaqus has been adopted herein which has the advantage of considering the coupling of structural mechanics and fluid mechanics fundamental equations. The maximum hoop stress and shear stress in the tank wall, the water sloshing heights in tanks and the energy response of the tanks have been studied. It is observed that stresses and liquid sloshing heights in the tank increase with decreasing scaled distance of the explosive material and increasing aspect ratio, i.e. height to radius ratio.

Finite element analysis of free vibration of the delaminated composite plate with variable kinematic multilayered plate elements

Composite laminates are prone to delamination. Implementation of delamination in the Carrera Unified Formulation frame work using nine noded quadrilateral MITC9 element is discussed in this article. MITC9 element is devoid of shear locking and membrane locking. Delaminated as well as healthy structure is analyzed for free mode vibration. The results from the present work are compared with the available experimental or/and research article or/and the three dimensional finite element simulations. The effect of different kinds and different percentages of area of delamination on the first three natural frequencies of the structure is discussed. The presence of open-mode delamination mode shape for large delaminations within the first three natural frequencies is discussed. Also, the switching of places between the second bending mode, with that of the first torsional mode frequency is discussed. Results obtained from different ordered theories are compared in the presence of delamination. Advantage of layerwise theories as compared to equivalent single layer theories for very large delaminations is stated. The effect of different kinds of delamination and their effect on the second bending and first torsional mode shape is discussed.

Thickness Increasing Characteristics of Steel Pipe during Die Forming

Relationships among the forming conditions (such as shapes of dies, lubrication conditions, and slide motion of the press machine) and the thickening ratio (thickness after forming / thickness before forming) has been clarified in uniaxial press forming by experiments and a three dimensional finite element simulation. Steel pipes with 39.0mm and 7.6mm thickness were used in the experiment. The relationship between thickening ratio and the forming load that depends on the die shape, lubrication, and slide motion of the press machine was investigated. It has also been found that an eight percent increase of the wall thickness of the pipes could be possible without buckling. It has been clarified that thickening ratio during die forming could be predictable by using a finite element simulation.

Method for Determining the Plastic Properties of Metallic Materials by Instrumented Indentation with Dual Pyramidal Indenters

Method for determining the plastic properties of metallic materials was proposed based on the functional relationships between representative stress, representative strain and nominal hardness which were established with the aid of dimensional analysis and finite element simulation. The errors of 0.2% yield strength and strain hardening exponent of five engineering metals were from-17.1% to 15.4% and from -0.125 to 0.11, respectively,which satisfied the need of engineering application and verified the effectiveness of the method.

Pipette aspiration of hyperelastic compliant materials: Theoretical analysis, simulations and experiments

This paper explores the pipette aspiration test of hyperelastic compliant materials. Explicit expressions of the relationship between the imposed pressure and the aspiration length are developed, which serve as fundamental relations to deduce the material parameters from experimental responses. Four commonly used hyperelastic constitutive models, e.g. neo-Hookean, Mooney–Rivlin, Fung, and Arruda–Boyce models, are investigated. Through dimensional analysis and nonlinear finite element simulations, we establish the relations between the experimental responses and the constitutive parameters of hyperelastic materials in explicit form, upon which inverse approaches for determining the hyperelastic properties of materials are developed. The reliability of the results given by the proposed methods has been verified both theoretically and numerically. Experiments have been carried out on an elastomer (polydimethylsiloxane, 1:50) and porcine liver to validate the applicability of the inverse approaches in practical measurements.

Three dimensional simulation on binding efficiency of immunoassay for a biosensor with applying electrothermal effect

In this work, we perform three dimensional finite element simulations on the binding reaction kinetics of the commonly used analyte–ligand protein pairs, namely, C-reactive protein (CRP) and anti-CRP, in a reaction chamber (microchannel) of a biosensor. For the diffusion limited binding biomolecular pairs, due to the slower transport speed of the analyte and the faster reaction rate of analyte–ligand complex, diffusion boundary layers often develop on the reaction surface. To enhance the performance of a biosensor by accelerating the transport speed, a non-uniform AC electric field is applied to induce the electrothermal force to stir the flow field. The swirling flow in the fluid can accelerate the transport of the analyte to and from the reaction surface and hence enhance the association and dissociation of analyte–ligand complex. Four types of biosensors with different arrangements of the geometric locations of the electrode pair and the reaction surface are designed to study the effects of varying geometric configuration on the binding efficiency. The simulation results show that the performance of a biosensor can be better improved by placing the electrodes and the reaction surface on the same side of the microchannel against the opposite side. For the best case studied in this work, the maximum initial slope of the binding curve can be raised up to 6.94 times (with respect to the field-free value) in the association phase, under applying AC field of 15 Vrms and operating frequency of 100 kHz. Another important result with applying electrothermal effect is that it is feasible to use the slower sample flow in the microchannel to save a lot of sample consumption without sacrificing the performance of a biosensor. Several control factors not studied in our previous works such as the thermal boundary condition and the effect of electrical conductivity are also discussed.

Three Dimensional Finite Element Simulation for Surface Residual Stress in End Milling Process

This paper proposes a method to simulate residual stress induced by end milling process via 3-D FEM. First, Johnson-Cook material model parameters for a Japanese type of alloy steel (SCM440H) were extracted by a combination method. With the material model parameters, symmetrical end milling process for plate of SCM440H was simulated by FE software to get the residual stress distribution in the machined workpiece. Residual stress measurement experiment was carried out after end milling process to be compared with simulation result to verify the method, which proved that high simulation accuracy can be obtained by extracted material model parameters.

Characterization of the viscoelastic-plastic properties of UPVC by instrumented sharp indentation

The yielding behavior of glassy polymers may be sensitive to the hydrostatic pressure and also be influenced by the strain rate. Thus, the yield strength is a function of hydrostatic pressure and strain rate instead of a constant. In this paper, using dimensional analysis and finite element simulations, we established a method to estimate the yield strength of glassy polymers by instrumented indentation. Together with the method for determining shear creep compliance proposed in our previous work, the viscoelastic-plastic properties of glassy polymers can be extracted from a single indentation load-depth curve. Applications were illustrated on unplasticized polyvinyl chloride (UPVC). The shear creep compliance and yield strength of UPVC were successfully determined by a single indentation test. Using these parameters, the true stress–strain curves of UPVC under different strain rates were approximately predicted according to a linear viscoelastic-perfectly plastic constitutive description.

Research of Three Dimensional Finite Element Simulation of Rail during Cooling and Pre-Bending Process

In this paper, with the thermal mechanical coupled method and the whole rolling process simulation result using as the initial thermal field, the thermal field and deformation of rail during cooling have been simulated, then rail pre-bending process is proposed according rail bending deformation curve during cooling The results show that the bending curve formula fitting by rail cooling deformation curve is accurate comparing with the actual situation. Moreover, pre-bending process is set by fitting formula, and the rail recovers straightly after cooling.

Spherical indentation method for determining the constitutive parameters of hyperelastic soft materials

A comprehensive study on the spherical indentation of hyperelastic soft materials is carried out through combined theoretical, computational, and experimental efforts. Four widely used hyperelastic constitutive models are studied, including neo-Hookean, Mooney-Rivlin, Fung, and Arruda-Boyce models. Through dimensional analysis and finite element simulations, we establish the explicit relations between the indentation loads at given indentation depths and the constitutive parameters of materials. Based on the obtained results, the applicability of Hertzian solution to the measurement of the initial shear modulus of hyperelastic materials is examined. Furthermore, from the viewpoint of inverse problems, the possibility to measure some other properties of a hyperelastic material using spherical indentation tests, e.g., locking stretch, is addressed by considering the existence, uniqueness, and stability of the solution. Experiments have been performed on polydimethylsiloxane to validate the conclusions drawn from our theoretical analysis. The results reported in this study should help identify the extent to which the mechanical properties of hyperelastic materials could be measured from spherical indentation tests.

Three dimensional finite element investigations into the effects of thickness and notch radius on the fracture toughness of polycarbonate

Fracture toughness of polycarbonate (PC), a commercially important glassy amorphous polymer, is known to be sensitively dependent on a number of factors including molecular weight, ageing time, loading rate and specimen geometry. In this work, we analyze the effect of notch radius and specimen thickness on the near tip fields and the consequence of these on the mode I fracture initiation. To this end, we have performed extensive three dimensional Finite Element simulations within the framework of large deformation elasto-plasticity based on a realistic constitutive model that has been carefully calibrated for PC. Using a simple set of criteria for fracture initiation by void nucleation or ductile tearing, we are able to reproduce experimentally observed brittle to ductile transitions that occur in PC with decrease in thickness and increase in notch radius.

Effects of curved geometry on residual stress in laser peening

Prevention of failure in materials has been extensively researched for centuries by people all over the world. Sustained or cyclic loading is a major cause of failure in many situations. There can be other contributing factors, such as manufacturing defects and the presence of unfavorable residual stresses. But residual stresses can also play a positive role and can enhance the life of the component, if applied properly. Laser peening (LP) is a surface enhancement technique that can impede crack initiation and propagation by inducing favorable compressive residual stresses in the peened components. Laser peening can generate deeper compressive stresses compared with other surface enhancement techniques, such as shot peening, and it has been used to improve the fatigue life of components in aerospace, automotive and medical applications. In this work, the effects of laser peening are studied by using two dimensional finite element simulation models created with ABAQUS©. Crack initiation often occurs along the curved regions or fillets of structural components because of the presence of high stress concentrations. These critical regions are modeled as a curved geometry to capture the curvature effects using simulation models. Concave and convex simulation models are created and compared with flat geometry to investigate the effects of curvature in a laser peening problem. A mechanism of residual stress generation in curved models is used to explain the residual stress results obtained from finite element models. The results predict that increasing the radius of curvature in a concave model decreases the compressive residual stress generated in the component while increasing the radius of curvature of a convex model increases the compressive residual stress induced in the material when compared with a flat component.

Beam model and three dimensional numerical simulations on suspended microchannel resonators

At the microscale level, the vibrational characteristics of microstructures have been widely applied on biochemical microchips, especially for bio-molecules detection. The vibrational mechanics and mechanism of microcantilever beams immersed in the fluids for detecting target bio-molecules carried in the fluids have been widely studied and realized in recent years. However, it is not the case for microcantilever beams containing fluids inside (called suspended microchannel resonators, SMR). In this paper, an 1-D beam model for SMR is proposed and the formula for prediction of resonant frequency and resonant frequency shift are derived. For verification of validity of the 1-D beam model, three dimensional finite element simulations using ANSYS are performed. The effects of relevant parameters, such as density and viscosity of the fluids, on the frequency response are investigated. A link between numerical simulations and mathematical modeling is established through an equivalence relation. Subsequently, a useful formula of the resonant frequency shift as a function of the mass variation and the viscosity of the contained fluid is derived. Good agreement between the numerical simulations and the experimental data is obtained and the physical mechanism is elucidated.

Numerical simulation of the Lamb wave propagation in honeycomb sandwich panels: A parametric study

The paper aims to describe the guided Lamb wave propagation in honeycomb sandwich panels. The application of Lamb waves is a well-known method in modern online structural health monitoring techniques. To analyze the wave propagation in such a complicated geometry with an analytical solution is hardly possible; therefore a dimensional finite element simulation is used. A piezoelectric actuator is used to excite the waves on the sandwich panel surface. The extended model of the honeycomb sandwich panel is consisting of two plate layers and a mid-core layer. In addition, a simplified model is used to reduce the computing costs, where the mid-core of the sandwich panel is replaced by a homogeneous layer. The results from the extended model and the simplified model are in most cases in a good agreement; however the limitations of using the simplified model are discussed. A parametric study is used to show the influence of the geometrical properties of honeycomb plates, the material properties of the skin plates and the loading frequency on the group velocity, the wave length and the energy transmission. Each of these properties provides valuable information to design an efficient health monitoring system. Finally, an experimental test is presented.