Mechanical behavior of Ti6Al4V lattice structures; numerical and experimental analysis

This study deals with the mechanical behavior of lattice structures produced by the Laser Powder Bed Fusion process experimentally and numerically for four different topologies of Body-Centered Cubic, Body-Centered Cubic with struts along Z-direction, Face-Centered Cubic and Face-Centered Cubic with struts along Z-direction. To study the effect of cross-section geometry of the struts on the mechanical behavior of the structure, three circular, rectangular and I-shaped cross-sections with the same surface area were manufactured and tested. Their simulations were done using Abaqus software and the simulation results were in great agreement with the test results. Numerical and experimental investigations showed that samples with the I-shaped cross-section of the strut exhibit more stiffness and strength

Evaluating the Effect of Oblique Ridge Conservation on Stress Distribution in an Endodontically Treated Maxillary First Molar: A Finite Element Study

Introduction: Although the maxillary first molar (MFM) has been frequently subjected to stress analysis in endodontic investigations, the available data about the effect of its oblique ridge are quite sparse. The aim of this study includes evaluating the effect of the residual oblique ridge on the stress distribution after preparing conservative access cavities. Methods: Based on the cone-beam computed tomographic data, the model of an intact MFM and 5 cavity designs were prepared for endodontic treatment, which were consequently filled with gutta-percha and dental resin composite (6 total models). All models were subjected to 4 types of occlusal loading; finite element analysis via ABAQUS CAE software (Dassault Systemes, Vélizy-Villacoublay, France) was accomplished, whereas other software programs such as (Mimics Research Materialise, Leuven, Belgium) and 3-Matic Research (Materialise) were also incorporated in different stages for detecting stress distribution. Results: The stress distribution on the MFM is not only dependent on the remaining width of the oblique ridge but also on the type of loading. The most stress on the cervical region was concentrated on the palatal root in some type of loading, whereas the least stress on the occlusal surface was recorded when the whole oblique ridge was replaced by the composite resin. Conclusions: When the occlusal contacts are occurring only on the palatal cusp, the stress distribution on the oblique ridge is noticeably affected by the cavity design. © 2020 American Association of Endodontist

Analysis and optimization of strut-based lattice structures by simplified finite element method

In this paper, the mechanical behavior of the lattice structures composed of unit cells such as BCC, BCCZ, FCC, FCCZ, and cubic arrangements with the struts in the forms of circle, rectangle, square, triangle, I-shape, and hollow-square longitudinal sections is examined. For this purpose, the elastic behavior of a lattice cubic with dimensions of 2 (cm) 7 2 (cm) 7 2 (cm) consisting of 125 unit cells and more than 1000 beam elements is investigated under the compressive loading using the finite element method. In this analysis, the mechanical properties such as stiffness, absorbed mechanical energy, and stiffness-to-weight ratio are determined for these cellular structures, and the orientations of their struts are optimized so that the structure\u27s stiffness–weight ratio is increased. It was observed that the cellular structures with an I-shaped cross-section have the highest stiffness-to-weight ratio among the studied cross-sections

Autofrettage of nonlinear strain-hardening cylinders using the proposed analytical solution for stresses

This paper focuses on pressurized thick-walled cylinders with nonlinear strain-hardening behavior. At first, a constitutive model is proposed to capture the test data done on the steel specimen. It is shown that this model is able to cover the various specific behaviors such as the perfect plastic, linear hardening, and nonlinear hardening behaviors. This constitutive model due to high performance in constitutive modeling and simplicity of its mathematical form is applied to pressurized thick-walled cylinders in order to find a closed-form analytical solution for their analysis. For this purpose, elasto-plastic stresses distribution in pressurized thick-walled cylinders made of a nonlinear strain-hardening material is obtained analytically for both loading and unloading phases using Tresca's yield criterion and considering the Bauschinger effect. Then, the solution is compared with experimental data and good agreement between predicted results and experimental data is observed. In the following, the residual stresses distribution are obtained to determine the best level of autofrettage for strengthening and design of these thick-walled cylinders prior to industrial use with the aim of increasing strength-to-weight ratio. It was observed that the parameters such as the material behavior (stress strain curve) and the Bauschinger effect have a significant influence on the results

Analysis and Design of a Permanent-Magnet Outer-Rotor Synchronous Generator for a Direct-Drive Vertical-Axis Wind Turbine

In Permanent-Magnet Synchronous Generators (PMSGs) the reduction of cogging torque is one of the most important problems in their performance and evaluation. In this paper, at first, a direct-drive vertical-axis wind turbine is chosen. According to its nominal value operational point, necessary parameters for the generator is extracted. Due to an analytical method, four generators with different pole-slot combinations are designed. Average torque, torque ripple and cogging torque are evaluated based on finite element method. The combination with best performance is chosen and with the analysis of variation of effective parameters on cogging torque, and introducing a useful method, an improved design of the PMSG with lowest cogging torque and maximum average torque is obtained. The results show a proper performance and a correctness of the proposed method

Design of a Permanent-Magnet Synchronous Generator for a 2 MW Gearless Horizontal-Axis Wind Turbine According to its Capability Curves

Permanent-Magnet Synchronous Generators (PMSGs) exhibit high efficiency and power density, and have already been employed in gearless wind turbines. In the gearless wind turbines, due to the removal of the gearbox, the cogging torque is an important issue. Therefore, in this paper, at first, design of a Permanent-Magnet Synchronous Generator for a 2MW gearless horizontal-axis wind turbine, according to torque-speed and capability curves, is presented. For estimation of cogging torque in PMSGs, an analytical method is used. Performance and accuracy of this method is compared with the results of Finite Element Method (FEM). Considering the effect of dominant design parameters, cogging torque is efficiently reduced

Ultrasound-assisted and efficient knoevenagel condensation reaction catalyzed by silica sodium carbonate nanoparticles

An efficient and ultrasound-assisted route to the synthesis of arylidene malononitriles/methylciano- or ethylciano acetates in a one-pot reaction catalyzed by silica sodium carbonate nanoparticles (SSC NPs) is described. In this reaction, SSC NPs demonstrated high efficiency as catalyst to obtain target products. By this achievement, a wide range of α,β-unsaturated compounds as Knoevenagel condensation products with good to excellent yields are obtained from reaction between numerous arylaldehydes, and malononitrile, methyl cianoacetate or ethyl cianoacetate. Target products which prepared in high yield and high purity can be candidate as important biologically active molecules. This method is an easy, cheap, rapid and highly efficient for the synthesis of desired products. In addition, capability of catalyst to separate from reaction mixture and reuse in further runs and being compatible with green chemistry are considered as other advantages of this procedure. All products were deduced from their FT-IR and FT-NMR spectroscopic and elemental analysis data. This work is licensed under a Creative Commons Attribution 4.0 International License