Commercial Finite Element Analysis Tool Research Articles

Numerical investigation on fracture behavior in novel material structure inspired from first hierarchy of human bone

In this work, at first, we modeled the bone first hierarchy structure made up of collagen fibril, and soft protein to evaluate the strength, and simulated the delamination pattern at the interface of the HAp, protein. We also analyzed a novel material structure inspired by the staggered structure of the bone at the first hierarchy level for its strength, and fracture behavior such as delamination at the interface. The soft matter considered is PLA polymer while the hard constituent is HAp. A commercial finite element analysis tool, ABAQUS 6.14 was used for the modeling purpose. The models were subjected to displacement controlled uniaxial tensile loading in a plane strain condition. The interfaces of the soft and hard constituents were modelled using cohesive surface modelling. Porous as well as non-porous models both were analyzed. The stress concentration was found to be higher in case of the porous model which is quite natural as the pores can be the points of stress concentration in comparison to the non-porous model. The delamination at the interface was correctly simulated by the use of cohesive surface elements. This study can be the first step towards novel material structure design mimicked from bone hierarchy.

Finite Element Analysis of Fatigue and Fracture Behavior in Idealized Airplane Wing Model with Embedded Crack Under Wind Load

Aircraft wings undergo forces like thrust, drag as well as transient loads due to gust. Even though these loads overall help in the stability of an aircraft but over time it can cause growth of defects such as micro cracks or voids due to fatigue. We would like to investigate the fatigue, fracture failure due to wind load during its long operating life of the airplane. Therefore, we have modeled the airplane wing as cantilever beam and applied fluctuating wind load. The airplane wing with embedded crack was modeled in commercial finite element analysis tool, ANSYS. The drag and lift forces acting as pressure on the adjacent faces of the wing with a transient wind load has been simulated to determine the loads on an aero foil working under similar conditions through CFD analysis. The load estimated through the CFD analysis was applied on the wing model to obtain the stress intensity factor and energy release rate. Analysis for fatigue failure was also carried out to predict life of the idealized model under considered loading. The results obtained through this work can be helpful in understanding the fatigue behavior in the transient loading condition such as wind in airplane wing.

Analytical modeling and numerical analysis of the effect of mosaic patterns on composite pressure vessels with dome

The aim of this work is to provide an analytical tool and numerical analysis for the optimum design of composite pressure vessels with the dome, incorporating triangular mosaic patterns. This article presents the analytical modeling involving kinematic constraints based on geodesic trajectory: the helical angle and dome thickness. The structural analysis is performed using a commercial finite element analysis tool. The results show that this new analytical method gives more accurate dome thickness than cubic spline function and Gramoll and Namiki’s methods. The incorporation of mosaic patterns based on winding kinematics provides more realistic modeling of the real stress distribution and the stress values compared to the vessel without mosaic patterns and vessels with mosaic patterns based on nongeodesic trajectories. The results have been validated and are quite promising with regard to better accuracy and safety.

A Computational Model for the Analysis of the Static Forced Performance of Self-Equalizing Tilting Pad Thrust Bearings

Abstract While failure analyses in the archival literature report thrust collar misalignment as a major cause of collapse in oil lubricated thrust bearings (TB), a self-equalizing tilting pad thrust bearing (TPTB) improves operation reliability by adjusting its pads to account for thrust collar tilt. This paper describes a kinematics model for the equalizing mechanism integrated into an existing thermo-elastohydrodynamic (TEHD) analysis tool to deliver load performance predictions for self-equalizing TPTBs. The analysis considers the actual leveling plates geometric model as obtained from a solids modeling commercial software and accounts for the sliding friction forces acting at the contact points of the leveling plates and the rolling friction at their pivots. Further, a Hertz contact analysis model uses the predicted forces to deliver a peak pressure and deformation over the contact area between the leveling plates. Next, this paper presents predictions for an example self-equalizing TPTB operating with a thrust collar static misalignment φ = 0.01 deg. The bearing 126 mm in outer diameter has six pads, operates at 4 krpm (26 m/s maximum surface speed) and under a specific load/pad ranging from 0.5 to 3.5 MPa. Compared to a nonequalizing TPTB, a self-equalizing TPTB operates with up to 50% larger minimum film thickness and about ½ largest elastic deformation. Friction forces acting at the contact points of the leveling plates show a significant effect on the performance of the pad leveling system as they reduce the film clearance and increase a pad peak pressure. Predictions from the Hertz contact analysis agree with those from a commercial finite element analysis tool and show a significantly large peak pressure at the contact points of the leveling plates (> 0.9 GPa) when the bearing supports a 3 MPa/pad specific load. This paper stresses the importance of conducting a comprehensive multiple-pad analysis to accurately evaluate the performance and reliable operation of self-equalizing TPTBs.

Enhancement of Static and Dynamic Performance of Composite Tapered Pretwisted Rotating Blade With Variable Stiffness

AbstractComposite pretwisted tapered rotating thin-walled beams (TWB) can be used as a load-carrying structural part of a composite helicopter, wind turbine, fan, and turbomachinery blades. In the present study, the variable stiffness concept with curvilinear fiber path is used to achieve improved structural statics and dynamics performance of uniform and asymmetric composite thin-walled rotating beams. A parametric study is performed to investigate the effect of different fiber paths on the structural performance metrics including frequency spacing, coupling factor, and critical buckling load. For this purpose, The Euler–Lagrange governing equations of the dynamic system are derived via Hamilton's principle. To solve the governing set of equations, the extended Galerkin’s method (EGM) is employed. To validate the TWB model with curvilinear fibers, commercial finite element analysis tools abaqus is used. The author believes that the results presented here are likely to provide valuable information to the engineers involved in the design of advanced turbomachinery rotating blades using a variable stiffness concept with curvilinear fiber placement.

An Experimental and Numerical Study of Repairs on Composite Substrates with Composite and Aluminum Doublers Using Riveted, Bonded, and Hybrid Joints.

In this work, experimental and numerical analyses of repairs on carbon fiber reinforced epoxy (CFRE) substrates, with CFRE and aluminum alloy doublers typical of aircraft structures, are presented. The substrates have a bridge gap of 12.7 mm (simulated crack), repaired with twin doublers joined with riveted, adhesive bonded, and hybrid joints. The performance of the repairs using different doubler materials and joining techniques are compared under static loading. The experimental results show that riveted joints have the lowest strength, while adhesive bonded joints have the highest strength, irrespective of the doubler material. Finite element analysis (FEA) of the studied joints is also performed using commercial FEA tool Abaqus. In the FEA model, point-based fasteners are used for the rivets, and a cohesive zone contact model is used to simulate the adhesive bond. The FEA results indicate that the riveted joints have higher tensile stresses on the metal doublers compared to the composite doublers. As per the failure modes, interestingly, for hybrid joints using composite doublers, the doublers fail due to net-section failure, while, for hybrid joints using metal doublers, it is the composite substrate that fails due to net-section failure. This suggests vulnerability of the composite structures to mechanical fastener holes. Lastly, the Autodesk Helius composite tool is used for prediction of first-ply failure and ply load distribution, and for progressive failure analysis of the composite substrate.

Effect of strain rate on bending and transmission characteristics of injection molded polyamide 66 spur gears

Polymer material exhibits time-dependent mechanical behavior due to its viscoelastic characteristics. Thus, unlike steel gears, polymer gears exhibit complex behavior when transmitting loads at various rotational speeds. In general, gear tooth surfaces exhibit complex stress due to their nonconformal geometry. Hence, the nonlinear material and nonlinear geometric aspects of polymer gear mesh prompted an investigation of the bending and transmission characteristics of injection molded polyamide 66 gears at various strain rate conditions. The injection molded tensile specimens made from the gear material were subjected to various rates of loading. The stress–strain performance at various rates of loading was evaluated and used to model linear and nonlinear gear materials for the numerical analysis. The numerical investigation was carried out on the steel–polyamide gear pair with the commercial finite element analysis tool ABAQUS® to predict the bending stress and static transmission error. The predicted static transmission error of the gear pair was compared with the experimental results obtained using an in-house developed gear test rig. The bending stress with the linear material models was higher than that of the nonlinear material models. An increase in bending stress with the strain rate was observed in the case of the nonlinear material models. The static transmission error predicted with the nonlinear material model at a higher strain rate was lower for both the single tooth contact and the double teeth contacts.

Comparative study and experiment of a double-sided permanent magnet linear synchronous generator according to magnetization pattern

This paper presents a comparison of efficiency and mover mass on a double-sided permanent magnet linear synchronous generator (PMLSG) according to its magnetization pattern. When a PMLSG has a lighter mover, it has advantages such as lower cost and other aspects regarding mechanical losses. In general, PMLSGs are used with a vertical PM pattern, but we propose a horizontal PM pattern in this paper because the horizontal PM mover does not need a back-iron for the magnetic path. Electromagnetic field analysis is especially essential when analyzing the characteristics of PMLSGs. For this type of analysis, commercial finite element analysis tools are widely used because they offer convenient user interfaces that provide very accurate analytical results. Based on two-dimensional finite element analysis, we got results for two different patterns and compared them with our experimental results. Finally, the results of this analysis and the test results obtained confirm the validity of the model and the superiority of the horizontal pattern proposed in this paper.

Emissivity compensated infrared thermometry for planar materials

PurposeThis paper aims to analyze the conical-shaped compensator applied to infrared (IR) thermometry for planar materials.Design/methodology/approachThe compensator for the IR thermometry system has been analyzed by means of numerical simulations performed in a commercial finite element analysis tool. Afterwards, the characteristics of a final system have been proposed. The simulation results have been validated by means of experimental measurements performed in a prototype of the proposed system.FindingsThe proposed conical shape geometry of the compensator is suitable to reduce the errors associated with the temperature estimation by IR thermometry when emissivity of the material is not known with adequate accuracy.Practical implicationsThis work proposed an arrangement of conical-shaped compensator to increase the precision in the IR radiation thermometry of planar materials.Originality/valueIn this paper, the conical shape geometry is proposed instead of the classical semi-spherical geometry for the compensator of an IR radiation thermometry system with the purpose of reducing the thickness of the complete system. This new proposal can be advantageous when geometrical constraints are imposed.

Implementation of Multi-Axial Fatigue Theory in FE Packages

Many mechanical or structural components are subjected to multi-axial, irregular cyclic loading during service. The direction and amplitude of principal stress and strain vary over a period of time results in non-proportional cyclic loading on the component. At geometrical discontinuities, even a monotonic load will result in multi-axial state of stress. In general, the life of the components subjected to multi-axial stress loadings, are evaluated using classical yield theories. The Tresca and von Mises criterions along with Basquin-Coffin and Manson life curve are widely used in commercially available Finite Element Analysis (FEA) tools. These classical methods are conservative and may not yield good experimental correlation at all the loading conditions and this augments the need for robust life estimation methodology.There are many commercially available FEA tools to estimate the multi-axial fatigue life viz. nCODE® which uses Wang-Brown method [1]. However, it has been found that for shear dominated fatigue material Fatemi-Socie criteria is more suitable. So an attempt is made to develop a an algorithm to implement Fatemi-Socie criteria in a commercially available generic FEA software in a cost effective way. This paper discusses how to estimate the life of a sample specimen subjected to multi-axial and non-proportional loading conditions. The classical yield criteria based on von-Mises stress with Basquin-Coffin and Manson equation and critical plane method viz, Fatemi-Socie criteria are implemented in to commercial FEA tool, ANSYS. This paper also attempt to see how these theories compare with experimental data. Results of this study would help in leveraging the established process of implementing custom based life estimation method in ANSYS for the estimation of the life of the mechanical components.

Fluxball magnetic field analysis using a hybrid analytical/FEM/BEM with equivalent currents

In this paper, a fluxball electric machine is analyzed concerning the magnetic flux, force and torque. A novel method is proposed based in a special hybrid FEM/BEM (Finite Element Method/Boundary Element Method) with equivalent currents by using an analytical treatment for the source field determination. The method can be applied to evaluate the magnetic field in axisymmetric problems, in the presence of several magnetic materials. Same results obtained by a commercial Finite Element Analysis tool are presented for validation purposes with the proposed method.

Finite element analysis of a femur to deconstruct the paradox of bone curvature

Most long limb bones in terrestrial mammals exhibit a longitudinal curvature and have been found to be loaded in bending. Bone curvature poses a paradox in terms of the mechanical function of limb bones, for many believe the curvature in these bones increases bending stress, potentially reducing the bone's load carrying capacity (i.e., its mechanical strength). The aim of this study is to investigate the role of longitudinal bone curvature in the design of limb bones. In particular, it has been hypothesized that bone curvature results in a trade-off between the bone's mechanical strength and its bending predictability. We employed finite element analysis (FEA) of abstract and realistic human femora to address this issue. Geometrically simplified human femur models with different curvatures were developed and analyzed with a commercial FEA tool to examine how curvature affects the bone's bending predictability and load carrying capacity. Results were post-processed to yield probability density functions (PDFs) describing the circumferential location of maximum equivalent stress for various curvatures in order to assess bending predictability. To validate our findings, a finite element model was built from a CT scan of a real human femur and compared to the simplified femur model. We found general agreement in trends but some quantitative differences most likely due to the geometric differences between the digitally reconstructed and the simplified finite element models. As hypothesized by others, our results support the hypothesis that bone curvature can increase bending predictability, but at the expense of bone strength.

Finite element model updating on small-scale bridge model using the hybrid genetic algorithm

Finite element (FE) model-based dynamic analysis has been widely used to predict the dynamic characteristics of civil structures. FE model updating method based on the hybrid genetic algorithm, by combining genetic algorithm and the modified Nelder–Mead's simplex method, is presented to improve bridge structures' FE model. An objective function is formulated as a linear combination of fitness functions on natural frequencies, mode shapes and static deflections using measurements and analytical results to update both stiffness and mass simultaneously. A commercial FE analysis tool, which can utilise previously developed element library and solution algorithms, is adopted for applications on diversified and complex structures. The validity of the proposed method is verified by using a simply supported bridge model with three I-shaped girders. FE models such as grid, beam-shell and shell model are considered to modify initial FE models on the experimental structure. Experimental results suggest that the proposed method can be applied efficiently to various FE models and is feasible and effective when this method is applied to identify FE modelling errors.

Techniques for Modeling Muscle‐induced Forces in Finite Element Models of Skeletal Structures

This work introduces two mechanics-based approaches to modeling muscle forces exerted on curvilinear bone structures and compares the results with two traditional ad hoc methods of muscle loading. These new models use a combination of tensile, tangential, and normal traction loads to account for muscle fibers wrapped around curved bone surfaces. A computer program was written to interface with a commercial finite element analysis tool to automatically apply traction loads to surface faces of elements in muscle attachment regions according to the various muscle modeling methods. We modeled a highly complex skeletal structure, the skull of a Jamaican fruit bat (Artibeus jamaicensis), to compare the four muscle-loading methods. While reasonable qualitative agreement was found in the states of stress of the skull between the four muscle load modeling methods, there were substantial quantitative differences predicted in the stress states in some high stressed regions of the skull. Furthermore, our mechanics-based models required significantly less total applied muscle force to generate a bite-point reaction force identical to those produced by the ad hoc muscle loading models. Although the methods are not validated by in vivo data, we submit that muscle-load modeling methods that account for the underlying physics of muscle wrapping on curved bone surfaces are likely to provide more realistic results than ad hoc approaches that do not. We also note that, due to the geometric complexity of many bone structures--such as the skull analyzed here--load transmission paths are difficult to conceptualize a priori. Consequently, it is difficult to predict spatially where the results of finite element analyses are likely to be compromised by using ad hoc muscle modeling methods. For these reasons, it is recommended that a mechanics-based method be adopted for determination of the proper traction loads to be applied to skeletal structures due to muscular activity.