Papers by Keyword: Finite Element Analysis (FEA)

Abstract: In this study, a design guideline for the die cavity and die bearing length distribution is proposed during an extrusion process of an asymmetrical thin sheet, such as clips of cell-phones. The plastic flow pattern of the billet inside the die cavity is analyzed using a commercial finite element package “DEFORM 3D”. The Module of Die Stress Analysis in the finite element software “DEFORM 3D” is also used to simulate the stress, strain, and the displacement distributions of the die during extrusion of clips of cell-phones. The extrusion load, the stress and strain distributions of the die, the temperature distribution, and thickness distribution of the extruded product are investigated. Furthermore, hot extrusion experiments using A6061 as the specimen are executed. The experimental results of temperature, thickness distribution of the product, extrusion force, etc, are compared with the analytical values to verify the validity of the proposed die design guideline.

Abstract: In the present paper, structural behaviour of masonry columns strengthened with fiber reinforced cementitious matrix have been investigated; in particular, numerical 3D simulations calibrated on experimental tests have been presented. T hree-dimensional numerical model, realized by using the commercial code MIDAS FEA, based on a macro-model approach, has been used to simulate the nonlinear structural behavior of masonry columns strengthened with FRCM, and two different models for unreinforced and strengthened columns have been adopted. The 3D numerical approach are presented and results discussed to investigate the interaction between masonry columns and reinforcement. The numerical model has been calibrated on a large number of experimental tests on confined masonry columns carried out at the University of Bologna; in particular, columns have been wrapped by FRP and FRCM and with different arrangements (continuous and discontinuous). The comparison of the numerical models with the experimental outcomes shows a good matching in terms of axial forces-strain curves and strength peak.

Abstract: The aim of the paper is to propose and assess the reliability of a modeling strategy which combines the homogenization of the masonry material and the use of zero-thickness interface elements. This strategy is specifically proposed for numerically investigating the structural response of FRP-reinforced curved masonry structures. Indeed, in order to consider the influence of the geometry curvature of the masonry substrate on the local bond behavior of the FRP-strengthening system, bond-slip laws which specifically account for the geometric curvature of the substrate are introduced at the FRP/substrate interface layer. Numerical analyses concerning masonry arches selected from the current literature are presented in the paper in order to assess the reliability of the proposed modelling approach.

Abstract: The structural system in Gothic architecture of Central Europe is characterized by the vaults supported on pillars and the dematerialization of walls to introduce into the Temple the maximum light possible. However the “Mediterranean Gothic” structure of the churches is formed by two sets of diaphragm walls breaking with the traditional gothic canons. The study carried out explains the reasons for these differences from an exhaustive structural analysis of Santa Catalina’s church of Valencia under seismic effects. Two methods for analyzing have been used for simulating the seismic effects: the pushover analysis and the nonlinear dynamic analysis in time-history. The non-linear damage model method with its evolution under static and dynamic loads was applied in both cases. The study has been extended up to five different simulations of the same Finite Element model, depending on the constructive elements that made up the wall structural system and two return periods of 475 and 950 years. The methods used gave a good correspondence in their results which make them two complementary methods according to the proposed objectives. The results show that the Santa Catalina’s church offers an optimal seismic response as a consequence of its structural system stiffness.

Abstract: Technological advances in the digital camera industry and computing resources make the use of photogrammetry a very fast, low-cost, contactless and non-destructive technique. It can represent a good alternative to obtain 3D information for monitoring and conservation of cultural heritage assets, especially where it is not possible to use 3D laser scanners and also in situations where areas to be inspected are not easily accessible [1]. Resolution generally depends on the number of images, their quality and the level of overlap between them, as well as hardware and software capabilities. Starting from 2D aerial or terrestrial photographic images, photogrammetry allows to reconstruct a 3D model in the form of a "point cloud" and also to derive accurate 3D measurements of large architectural elements.This paper is about stereo-photogrammetric scanning by drone performed by MENCI software s.r.l. aimed at the definition of the state of conservation of the “Bridge of the Towers” in Spoleto and its long term preservation without building scaffoldings. It was performed within the RoMA (Resilience enhancement of a Metropolitan Area) project, through an agreement between the “Italian National Agency for New Technologies, Energy and Sustainable Economic Development” (ENEA) and the “Italian Ministry of Cultural Heritage and Activities” (MIBACT).Photogrammetric scanning and FE modelling were applied within the project together with many other monitoring techniques in order to assess the bridge cracks pattern and its structural health by a multidisciplinary approach that allows their mutual validation [2].As one of the most important problems in the use of photogrammetric 3D reconstruction is the considerable demand in terms of hardware and software resources for images processing and data storage, thanks to the HPC (High Performance Computing) resources provided by the CRESCO infrastructure (Research Computational Centre on Complex Systems), it was possible to analyse and process a large amount of high-resolution photos in order to detect the crack pattern and to assess the actual damage state to be monitored over time [3].

Abstract: The Scaled boundary finite element method and finite-infinite element method are used to model the system of reservoir water – gravity Dam - infinite foundation. The effect of the reservoir water and the infinite foundation on the seismic response of the dam system is analyzed. In the paper, taking the Koyna gravity dam as the research object, the dynamic water pressure on the upstream face of the dam is calculated by SBFEM. The finite-infinite element method is used to model the infinite foundation. Finally, the time history of seismic displacement and the response of the dam under different elastic modulus are evaluated. By comparing the displacement response of the infinite element model of different elastic modulus, the conclusion is drawn that the response of the dam is increased with the increase of the elastic modulus of the foundation. In addition, the calculated results are compared with those of the model with no-mass foundation. It shows that the results of the model considering the radiation damping of the foundation are less than that of the model with no mass foundation.

Abstract: This study presents the analysis of the constitutive behavior of fiber-reinforced polymer (FRP)-confined steel fiber reinforced concrete (SFRC) using a newly developed concrete damage-plasticity approach. Finite element (FE) analysis is conducted based on Lubliner’s model. The new concrete damage-plasticity approach accurately incorporates the effects of the steel fiber volume fraction and aspect ratio, confinement level, concrete strength, and nonlinear dilation behavior of confined concrete. New failure surface and flow rule were established using the experimental database. In order to validate the damage-plasticity model, the predictions from the FE analysis are compared with both experimental results and predictions of an accurate existing model for FRP-confined plain concrete. The analysis results indicate that the proposed approach accurately predicts the compressive behavior of FRP-confined SFRC.

Abstract: In this research, the effect of nanosized air bubbles embedded within carbon nanotubes (CNTs) coated by various thicknesses of alumina (Al₂O₃) reinforced epoxy resin based composite on the natural frequencies of a multi-cracked bar is investigated in details. The impact of cracks’ locations and depths within the hybrid composite structure on the natural frequency profiles is investigated. The volume fraction of CNTs is fixed to 0.5 wt. % due to the significant improvements reported in the literature when the composite is reinforced with this volume fraction of CNTs. The results of the multi-scale finite element analysis are verified by comparing with previous studies and a good agreement is shown relating to the longitudinal natural frequencies. The results of the research show that the dynamic response of cracked bar is highly sensitive to the volume fractions of nanosized air bubbles located within the composite. The results of the study supported the hypothesis that the nanosized air bubbles can be used to reduce the weight of heavy composite structures along with using of suitable coatings to improve the mechanical properties of the hybrid composite. Furthermore. The results of the study can be employed to detect multiple cracks located within similar structures like wind turbine blade (WTB) fabricated from a hybrid composite structure composed of carbon fiber reinforced modified epoxy resin which contains nanosized air bubbles and CNTs nanofillers coated by Al₂O₃ at different thicknesses.

Abstract: Modeling and simulation of mechanical structures in development phase are fundamental to optimize and improve the stability and reliability of the final product as well as to reduce the cost of prototyping and testing. Wind turbines are subject to critical loading to the centrifugal force due to wind speed and gravitational force. The present study discusses three-dimensional numerical simulations of combined Darrieus-Savonius wind turbine D-SWT for applications in urban and isolated areas for lighting, pumping water, etc. The Darrieus turbine is used to produce wind power and the Savonius rotor to start the system. Finite Element Analysis (FEA) using SolidWorks 2015 is employed to generate the geometry of the structure and SolidWorks Simulation to investigate the stability and reliability static on the structure of the D-WST built by two types of material of the blade Galvanized Steel (GS) and Aluminum alloys 1060-H18 (ALU). Mechanical parameter of the structure are calculated for critical loading conditions, including the gravity and wind pressure loading due to the wind speed of 23m/s. Simulations results indicate no structural failure is predicted for all components of the D-SWT for both materials used according to Von Mises criterion stresses and the factors of safety of the most fragile material are greater than (the unity) 1. The maximum displacements found (3.84 & 6.81mm), occurred at the tip blades (free ends levels). These displacements are accepted relatively to the structure size.

Abstract: This study investigated bending stress distribution on involute spur gear tooth profiles with pressure angle of 20 ̊ but different modules 2.5, 4.0 and 6.0 mm, using a finite-element-based simulation package - AutoFEA JL Analyzer. The drafting of the geometry for the three gear tooth profiles were implemented on the platform of VB-AutoCAD customized environment, before importing to the package. These were separately subjected to analysis for bending stresses for a point at the tooth fillet region with appropriate settings of material property, load and boundary conditions. With the same settings, the bending stresses were computed analytically using American Gear Manufacturers Association (AGMA) established equation. The results of the two approaches were in good agreement, with maximum relative deviation of 4.38%. This informed the confidence in the implementation of the package to investigate the variation of bending stress within the gear tooth profile. The simulation revealed decrease in the bending stresses at the investigated regions with increase in the module of the involute spur-gear. The study confirms that Finite element simulation of stresses on gear tooth can be obtained accurately and quickly with the AutoFEA JL Analyzer.