Use Of Finite Element Analysis Research Articles

Experimental Evaluation of True Stress-Strain for Ductile Thermoplastics

<div class="section abstract"><div class="htmlview paragraph">Thermoplastics find application in many automotive components. Off late, hardware testing is supplemented by analysis using finite element (FE) codes. One of the factors determining the analysis accuracy is the representation of the components with suitable material models. While a uniaxial tensile test on the specimens typically provides engineering stress-strain data, material plasticity models in commercial FE solvers, such as LS-DYNA and ABAQUS, require equivalent plastic strain versus true stress as input. Engineering stress and strain can be converted to the corresponding true stress and true strain using equations based on the constant volume assumption; however, these equations are valid only up to the point of necking. A conventional approach of estimating the true stress and true strain beyond necking involves a trial and error method in which several true stress-strain curves are generated, and a finite element simulation is used to find the best possible fit with the test data. This approach is time consuming and provides an approximate true stress-strain curve beyond necking. The objective of this paper is to provide an experimental alternative to the conventional approach. Digital image correlation (DIC) was used to measure volumetric strain in the necking region of a tensile test specimen by employing two cameras simultaneously, one focusing on the front (width, length) and the other focusing on the side (thickness, length) surface of the test specimen. True strain measured by DIC in the longitudinal direction and the true stress, estimated from the applied force and measured true transverse strains, were used to generate material models for use in FE analysis without modification, i.e. without a need for correction factors. Material models were then validated by comparing the FE simulation with the tensile test results.</div></div>

Simulating wave propagation in acoustic metamaterials with isogeometric analysis

Finite element analysis (FEA) is commonly used to simulate and design acoustic metamaterials (AMM). Numerical studies employing FEA often rely on Bloch-Floquet analysis of a single unit cell or direct numerical simulations that include many unit cells. Unfortunately, AMM unit cells with fine features necessitate dense computational meshes to resolve the geometry and accurately model wave motion, sometimes prohibiting the use of FEA. Isogeometric Analysis (IGA) is a potential alternative approach to FEA for wave propagation problems. IGA utilizes basis functions that are typically employed in Computer Aided Design (CAD) software, such as B-splines and Non-Uniform Rational B-Splines (NURBS), to represent both the geometry and the wave solution. The direct utilization of the CAD geometry eliminates the need for a separate computational mesh of the geometry and the smoothness of the NURBS basis functions provides increased accuracy per degree of freedom. The latter point is particularly useful for high frequency problems. This talk presents IGA as a means to model AMM behavior and compares results with FEA simulations in terms of total simulation time and accuracy. Finally, we comment on the current limitations of IGA and discuss avenues of future research. [Work supported by the ARL:UT postdoctoral fellowship program.]

The use of FEA and semi-empirical equations for weight estimation of a passenger aircraft

PurposeThe purpose of this paper is to present the result of calculations that were performed to estimate the structural weight of the passenger aircraft using novel technological solution. Mass penalty resulting from the installation of the fuselage boundary layer ingestion device was needed in the CENTRELINE project to be able to estimate the real benefits of the applied technology.Design/methodology/approachThis paper focusses on the finite element analysis (FEA) of the fuselage and wing primary load-carrying structures. Masses obtained in these analyses were used as an input for the total structural mass calculation based on semi-empirical equations.FindingsCombining FEA with semi-empirical equations makes it possible to estimate the mass of structures at an early technology readiness level and gives the possibility of obtaining more accurate results than those obtained using only empirical formulas. The applied methodology allows estimating the mass in case of using unusual structural solutions, which are not covered by formulas available in the literature.Practical implicationsAccurate structural mass estimation is possible at an earlier design stage of the project based on the presented methodology, which allows for easier and less costly changes in designed aircrafts.Originality/valueThe presented methodology is an original method of mass estimation based on a two-track approach. The analytical formulas available in the literature have worked well for aeroplanes of conventional design, but thanks to the connection with FEA presented in this paper, it is possible to estimate the structure mass of aeroplanes using unconventional technological solutions.

Investigation of the Performance of the Interval Radial-Stop In-Line Device Under Conditions of Increased Pressure

The article reflects the results of a study to determine the operability of an interval radial-thrust in-line device, intended for use in the repair of the linear part of main gas pipelines. The paper contains information characterizing the stress-strain state of the most wear-out elements of the inline shell. The problem is reduced to finding the equivalent stresses for the initially selected material. The results of the study indicate that under the conditions of a one-sided force factor (pressure) of the gas pipeline medium, the limiting state of the material of the end element is not reached. As a methodological basis for the study, the use of finite element analysis is assumed. The result of the study is a picture of the distribution of equivalent stresses in the plane of the end element.

Predictive Hydration Model of Portland Cement and Its Main Minerals Based on Dissolution Theory and Water Diffusion Theory.

Efficient and accurate cement hydration simulation is an important issue for predicting and analyzing concrete’s performance evolution. A large number of models have been proposed to describe cement hydration. Some models can simulate the test results with high accuracy by constructing reasonable functions, but they are based on mathematical regression and lack of physical background and prediction ability. Other models, such as the famous HYMOSTRUC model and CEMHYD3D model, can predict the hydration rate and microstructure evolution of cement based on its initial microstructure. However, this kind of prediction model also has some limitations, such as the inability to fully consider the properties of cement slurry, or being too complicated for use in finite element analysis (FEA). In this study, the hydration mechanisms of the main minerals in Portland cement (PC) are expounded, and the corresponding hydration model is built. Firstly, a modified particle hydration model of tricalcium silicate (C3S) and alite is proposed based on the moisture diffusion theory and the calcium silicate hydrate (C-S-H) barrier layer hypothesis, which can predict the hydration degree of C3S and alite throughout the age. Taking the hydration model of C3S as a reference, the hydration model of dicalcium silicate (C2S) is established, and the synergistic hydration effect of C3S and C2S is calibrated by analyzing the published test results. The hydration model of tricalcium aluminate(C3A)-gypsum system is then designed by combining the theory of dissolution and diffusion. This model can reflect the hydration characteristics of C3A in different stages, and quantify the response of the hydration process of C3A to different gypsum content, water–cement ratio, and particle size distribution. Finally, several correction coefficients are introduced into the hydration model of the main mineral, to consider the synergistic hydration effect among the minerals to some extent and realize the prediction of the hydration of PC.

Assessing the use of finite element analysis for mechanical performance evaluation of intervertebral body fusion devices.

BackgroundIntervertebral body fusion devices (IBFDs) are a widely used type of spinal implant placed between two vertebral bodies to stabilize the spine for fusion in the treatment of spinal pathologies. Assessing mechanical performance of these devices is critical during the design, verification, and regulatory evaluation phases of development. While traditionally evaluated with physical bench testing, empirical assessments are at times supplemented with computational models and simulations such as finite element analysis (FEA). However, unlike many mechanical bench tests, FEA lacks standardized practices and consistency of implementation.ObjectivesThe objectives of this study were twofold. First, to identify IBFD 510(k) submissions containing FEA and conduct a comprehensive review of the elements provided in the FEA reports. Second, to engage with spinal device manufacturers through an anonymous survey and assess their practices for implementing FEA.MethodsFirst, a retrospective analysis of 510(k) submissions for IBFDs cleared by the FDA between 2013 and 2017 was performed. The contents of FEA test reports were quantified according to FDA guidance. Second, a survey inquiring about the use of FEA was distributed to industry and academic stakeholders. The survey asked up to 20 questions relating to modeler experience and modeling practices.ResultsSignificant gaps were present in model test reports that deemed the data unreliable and, therefore, unusable for regulatory decision‐making in a high percentage of submissions. Nonetheless, the industry survey revealed most stakeholders employ FEA during device evaluation and are interested in more prescriptive guidelines for executing IBFD models.ConclusionsThis study showed that while inconsistencies and gaps in FEA execution do exist within the spinal device community, the stakeholders are eager to work together in developing standardized approaches for executing computational models to support mechanical performance assessment of spinal devices in regulatory submissions.

Unfavorable geometric imperfections in steel plate girders subjected to localized loads

Recent experimental studies have shown that the current EN1993-1-5 patch loading resistance model underestimates the ultimate strength of steel plate girders in certain cases, especially for longitudinally stiffened steel plate girders and longer patch load lengths. In addition to this resistance model, the design standard allows the use of finite element analysis for the ultimate limit state. The existing design recommendations for an adequate ultimate limit state design are found insufficient. In the current paper, the imperfection sensitivity analysis of steel plate girders subjected to patch loading is performed. The paper presents a nonlinear finite element parametric study designed to determine the influence of a variety of geometric imperfections on the patch load resistance of longitudinally unstiffened and stiffened steel plate girders. Experimentally measured, buckling mode-affine, and hand-defined sinusoidal geometric imperfections were varied in the study in combination with varying patch load lengths and relative stiffnesses of the longitudinal stiffener.The ultimate strength of longitudinally unstiffened and stiffened steel plate girders increases as the patch load length is increased for all the geometric imperfections considered. For relatively small patch load lengths, the relative stiffness of the longitudinal stiffener has no significant influence on the ultimate load regardless of the geometric imperfection. For longer patch load lengths, the ultimate strength is highly dependent on geometric imperfections. The influence of the web panel aspect ratio is shown to be negligible for smaller patch load lengths regardless of the geometric imperfection, while for longer applied loads, the impact of this ratio is dependent on the geometric imperfection.Unfavorable geometric imperfections in steel plate girders subjected to patch loading are governed by the patch load length and the relative stiffness of the longitudinal stiffener. Different unfavorable geometric imperfections were found for different patch load lengths and relative stiffnesses. Local geometric imperfections defined in the upper web sub-panel yield lower ultimate strengths than global geometric imperfections (defined over the whole web depth). The lowest patch load resistances were returned for geometric imperfections that resembled the deformation at collapse (collapse-affine geometric imperfections). Although the concept of collapse-affine geometric imperfections seems impractical for design purposes (a geometrically and materially nonlinear analysis must be conducted before collapse-affine geometric imperfection shapes are determined), the use of these imperfection shapes is recommended.

PERSONALIZED CHOICE OF STRUCTURAL MATERIALS FOR ARTIFICIAL CROWNS FROM THE LEVEL OF MULTI-UNIT ABUTMENT OR TITANIUM PLATFORM FOR DIRECT PROSTHETICS ON DENTAL IMPLANTS

The high prevalence of secondary adentia in the adult population, as well as increased aesthetic requirements of patients has contributed to the development of orthopedic dentistry. Direct prosthetics on dental implants have been increasingly used for replacing defects in the dentition. However, the choice of structural materials for dental implant-supported prostheses is not fully understood. Hence, it remains a debatable issue.
 Purpose of the study: to justify the optimal structural materials for artificial crowns from the level of a multi-unit abutment or a standard titanium platform for direct prosthetics on dental implants with the use of finite-element analysis of the stress-strain state of the “bone tissue-dental implant-abutment-suprastructure” multidimensional model under the conditions of simulation modeling.
 Materials and methods. Specialized CAD / CAE software was employed to develop multi-dimensional computer models of biomechanical systems such as “bone tissue-dental implant-abutment-suprastructure” with simulation of direct prostheses on dental implants with the corresponding physical and mechanical properties of structural elements and load conditions. The created 10 simulation models were based on combinations of two types of abutment (standard titanium platform (A1) and multi-unit abutment (A2)), and five structural materials of the crown, including lithium disilicate glass ceramic (KM1), polymer-infiltrated hybrid ceramic (KM2), polymethyl methacrylate (PMMA) (KM3), zirconia (KM4), and multi-layer zirconia (KM5)). The stress-strain state and the bearing capacity of biomechanical systems were assessed with the use of the von Mises stresses analysis and safety factors.
 Results. During a numerical experiment, there was revealed a complex stress-strain state in “bone tissue - dental implant - abutment - suprastructure” biomechanical systems. The maximum loads were recorded in systems with A1 and A2 type of abutment in the crown models (149.37 MPa and 142.08 MPa, respectively), spongy (4.25 MPa and 4.08 MPa) and the cortical bone (20.58 MPa and 20.61 MPa). The nature of the distribution of the von Mises stresses in the structural elements of systems with A1 and A2 types of abutments was found to be similar for all models under consideration with KM1, KM2, KM4, KM5 structural materials of crowns, except for the system with KM3 suprastructure material.
 Conclusions. Based on the findings of computer simulation of the stress-strain state of “bone tissue - dental implant - abutment - suprastructure” biomechanical systems, there have been grounded the optimal structural materials for dental implant-supported crowns for direct prosthetics by such abutment as a standard titanium platform and multi-unit abutment. The obtained values of the von Mises stresses analysis and safety factors showed that with external force applied to the dental implant-supported crown the at an angle of 11.5°, the greatest bearing capacity was ensured by biomechanical systems with a standard titanium platform and multi-unit abutment with crown materials including zirconia (safety factors 6.22 and 6.42 respectively), multilayer zirconia (safety factors 5.52 and 5.70) and lithium disilicate glass ceramic (safety factors 2.39 and 2.52).

Finite Element Analysis of OT Bridge fixed prosthesis system

The aim of this paper has been to define the behaviour of an OT Bridge fixed prosthesis system (Rhein83®). Through the use of finite element analysis, the typical load conditions of the chewing dynamics were studied, in order to highlight possible errors of inadequate use of the implant itself. These techniques highlight how knowledge of the stresses produced on the implant prosthesis becomes necessary and indispensable. The innovation in this retention system lies in the use of Seeger rings in acetal resin. The Seeger ring constitutes a revolution in the concept of anchoring the prosthesis; having a retentive function, it prevents the screws from unscrewing by taking most of the retentive load.

Extending Marlow’s general first-invariant constitutive model to compressible, isotropic hyperelastic materials

PurposeA general first-invariant constitutive model has been derived in literature for incompressible, isotropic hyperelastic materials, known as Marlow model, which reproduces test data exactly without the need of curve-fitting procedures. This paper aims to describe how to extend Marlow’s constitutive model to the more general case of compressible hyperelastic materials.Design/methodology/approachThe isotropic constitutive model is based on a strain energy function, whose isochoric part is solely dependent on the first modified strain invariant. Based on Marlow’s idea, a principle of energetically equivalent deformation states is derived for the compressible case, which is used to determine the underlying strain energy function directly from measured test data. No particular functional of the strain energy function is assumed. It is shown how to calibrate the volumetric and isochoric strain energy functions uniquely with uniaxial or biaxial test data only. The constitutive model is implemented into a finite element program to demonstrate its applicability.FindingsThe model is well suited for use in finite element analysis. Only one set of test data is required for calibration without any need for curve-fitting procedures. These test data are reproduced exactly, and the model prediction is reasonable for other deformation modes.Originality/valueMarlow’s basic concept is extended to the compressible case and applied to both the volumetric and isochoric part of the compressible strain energy function. Moreover, a novel approach is described on how both compressive and tensile test data can be used simultaneously to calibrate the model.

A Proposal of Mode Polynomials for Efficient Use of Component Mode Synthesis and Methodology to Simplify the Calculation of the Connecting Beams

Analytical method using Rayleigh–Ritz method has not been widely used recently due to intensive use of finite element analysis (FEA). However as long as suitable mode functions together with component mode synthesis (CMS) can be provided, Rayleigh–Ritz method is still useful for the vibration analysis of many local structures in a ship such as tanks and supports for an equipment. In this study, polynomials which combines a simple and a fixed support have been proposed for the satisfaction of boundary conditions at a junction. Higher order polynomials have been generated using those suggested by Bhat. Since higher order polynomials used only satisfy geometrical boundary conditions, two ways are tried. One neglects moment continuity and the other satisfies moment continuity by sum of mode polynomials. Numerical analysis have been performed for typical shapes, which can generate easily more complicated structures. Comparison with FEA result shows good agreements enough to be used for practical purpose. Frequently dynamic behavior of one specific subcomponent is more concerned. In this case suitable way to estimate dynamic and static coupling of subcomponents connected to this specific subcomponent should be provided, which is not easy task. Elimination of generalized coordinates for subcomponents by mode by mode satisfaction of boundary conditions has been proposed. These results are still very useful for initial guidance.

Assessment of reverse gun taylor cylinder experimental configuration

Experimental efforts for Taylor-anvil impact tests have often been limited to near room temperature. The ‘Reverse Gun’ method proposed by Gust in 1982 allows for the Taylor impact specimen to be uniformly heated without temperature losses before impact. Through the use of finite element analysis, we explore two topics in this work. First, we examine whether the reverse gun experimental configuration is comparable to the traditional Taylor-anvil setup. Second, we assess the accuracy of several commonly employed flow strength models in terms of their ability to predict the reverse gun experimental results which involve dynamic loading conditions and complex thermo-mechanical coupling. The reverse gun simulations are performed for tantalum targets at initial temperatures in the range 295 K to 1295 K and velocities from 135 m/s to 242 m/s. We show that with suitable care in the modeling of the preheated reverse gun experiments one can make valuable assessments of flow strength models. Given the conditions explored, these observations probe the thermal softening, strain hardening, and strain rate sensitivity of the material.

Application of Finite Element Analysis in medicine

The article discusses the use of the finite element method in medicine. Finite element analysis has existed for a long time, and its application can cover vast areas of various fields. Using this technique in medicine is not new, but there are some problems that still have to be solved. In the work Finite Element Analysis or Method is explained. Briefly explained the application of the tool in the fields not related to medicine. A literature review is conducted on the use of Finite Element Analysis in medicine. The usage of the technique in dentistry is covered. Disadvantages and advantages of the use of the Finite Element Analysis tool in dentistry is presented in the work.

Bioengineering Case Study to Evaluate Complications of Adverse Anatomy of Aortic Root in Transcatheter Aortic Valve Replacement: Combining Biomechanical Modelling with CT imaging.

Gated computed tomography (CT) might not adequately predict occurrence of post-implantation transcatheter aortic valve replacement (TAVR) complications in hostile aortic root as it would require a more complex integration of morphological, functional and hemodynamical parameters. We used a computational framework based on finite element analysis (FEA) to simulate patient-specific implantation. Application of biomechanical modelling using FEA to gated-CT was able to demonstrate the relation of the device with voluminous calcification, its consequent misalignment and a significant stent deformation. Use of FEA and other advanced computed predictive modelling techniques as an adjunct to CT scan could improve our understanding of TAVR, potentially predict complications and fate of the devices after implantation and inform patient-specific treatment.

Brake Squeal Analysis using Finite Element Analysis Method

The Finite Element Analysis (FEA) is widely used for solving many Engineering problems. This paper focuses on use of FEA for Brake Squeal Analysis. Automobiles generates several kinds of noises like Groan, chatter, judder, moan, and squeal. Brake squeal can be defined as an unwanted noise that occurs due to dynamic instability of the system. It generally occurs in the frequency range of 1 KHz to 16 KHz.The aim of the project is to predict the squeal noise occurring at particular frequencies at an early stage of development using full corner brake model. The preprocessing of the full corner brake model is done using Hypermesh while the processing and post-processing is to be carried out by using Abaqus. Analysis uses non-linear static simulation which is followed by Complex Eigen Value (CEA) extraction for carrying out the squeal Simulation. It provides the relation between damping ratio and frequency (Real part of the complex Eigen value). If the damping ratio at any particular frequency is above one, it can be said that squeal will occur at that particular frequency.

Trends in the Characterization of the Proximal Humerus in Biomechanical Studies: A Review

Proximal humerus fractures are becoming more common due to the aging of the population, and more related scientific research is also emerging. Biomechanical studies attempt to optimize treatments, taking into consideration the factors involved, to obtain the best possible treatment scenario. To achieve this, the use of finite element analysis (FEA) is necessary, to experiment with situations that are difficult to replicate, and which are sometimes unethical. Furthermore, low costs and time requirements make FEA the perfect choice for biomechanical studies. Part of the complete process of an FEA involves three-dimensional (3D) bone modeling, mechanical properties assignment, and meshing the bone model to be analyzed. Due to the lack of standardization for bone modeling, properties assignment, and the meshing processes, this article aims to review the most widely used techniques to model the proximal humerus bone, according to its anatomy, for FEA. This study also seeks to understand the knowledge and bias behind mechanical properties assignment for bone, and the similarities/differences in mesh properties used in previous FEA studies of the proximal humerus. The best ways to achieve these processes, according to the evidence, will be analyzed and discussed, seeking to obtain the most accurate results for FEA simulations.

Evaluation of the effects of various force configurations and magnitudes on scoliotic curve correction by use of finite element analysis: A case study

Background: Scoliosis is a three-dimensional (3-D) spinal deformity that is associated with changes in the alignment of the spine in sagittal, frontal, and transverse planes. Various treatment approaches have been used to control scoliotic curve progression and decrease the curve. Although various braces have been used in this regard, it would be difficult to check the effects of multiple types of braces on scoliotic curve correction for each scoliotic patient. Therefore, the aim of this study was to evaluate the effects of various force magnitudes and configurations on scoliotic curve correction. Methods: A 3-D model of a scoliotic patient was produced based on CT scan images of the total spine. The scoliotic curves were 21 and 45 degrees in lumbar and thoracic parts, respectively. Mimics software was used to produce a 3-D model of the spine. The stress developed in the spine structure and the magnitude of correction achieved were evaluated following the use of various force configurations and magnitudes by use of finite element analysis (FEA). Results: The results of this analysis showed that vertical forces were more effective than transversely directed forces in decreasing scoliotic curve. There was an inverse relationship between the corrections of lumbar and thoracic curves. However, use of vertically directed forces decreased both lumbar and thoracic curves. An increase in the magnitude of transverse forces did not increase the correction, but it did increase the stress developed in the structure. Conclusions: The results of this case study confirmed the efficiency of vertically directed forces to decrease scoliotic curves of lumbar and thoracic spinal parts. The results of this analysis confirmed the results of the available literature, which support the efficiency of some braces such as Boston, Lyon, and Cheneau, which were mostly designed based on full contact and vertical traction. The results of this study also support the feasibility of finite element analysis to predict the output of brace treatment by use of various force configurations. Level of Evidence: Level IV.

Comparative study on vibration characteristics of aircraft wings using finite element method

In recent times, there has been significant research in the area of vibration in aircraft wings. Vibration can cause some serious failure in the structure. The increase in research in vibration has led to taking design considerations in the wings. This paper specifically focuses on the vibration in wings. Modal analysis of wing with the rectangular cross section is done with the use of Finite Element Analysis. Three different materials (Aluminum, Carbon Fiber and E-glass Fiber) have been incorporated which describe the effect of free vibration. The results show that Aluminum 2024 is best suited for the design of aircraft wings compared to other two materials.

Modeling and Experimental Analysis of Shear-Slitting of AA6111-T4 Aluminum Alloy Sheet.

This work presents experimental studies with numerical modeling, aiming at the development of guidelines for shaping aluminum alloy AA6111-T4, t = 1.5 mm thick, with the use of a shear-slitting operation. During the experimental tests, parametric analyses were conducted for the selected material thickness. For the purposes of the material deformation’s analysis, a vision system based on the digital image correlation (DiC) method was used. Numerical models were developed with the use of finite element analysis (FEA) and the mesh-free method: smoothed particle hydrodynamics (SPH), which were used to analyze the residual stress and strain in the cutting zone at different process conditions. The results indicate a significant effect of the horizontal clearance between knives on the width of the deformation zone on sheet cut edge. Together with the clearance value increase, the deformation zone increases. The highest burrs on the cut edge were obtained, when the slitting speed was set to v = 17 m/min, and clearance to hc = 6%t. A strong influence was observed of the horizontal clearance value at high slitting speeds on burr unshapeliness. The most favorable conditions were obtained for v = 32 m/min, hc = 0.062 mm, and rake angle of upper knife for α = 30°. For this configuration, a smooth sheared edge with minimal burr height was obtained.

Finite Element Application in Reservoir Deformation Analysis (Pilot Phase 2)

Finite element method (FEM) is a numerical technique for solving Engineering problem and Mathematical Physics. Useful problems with complicated geometries, Loading, and material properties where analytical solutions may not be obtained. Some of the complicated problems involving load is a cylindrical Reservoir structures where crude oil is stored in a Tank Farm. This paper demonstrates the use of Finite Element Analysis in above surface cylindrical Reservoir Engineering Structure. The reservoir which has sixteen (16) monitoring station was monitored using reflectorless Total station. This paper is the second phase of our pilot model and we hope to developed this second phase further to cover nine studs. The studs covered ranges from northern part of the Reservoir to the southern parts to further test the application of FEM triangular shaded (Truss) elements.