Aerospace Science and Technology
Milad Noorabadi; Rahnama Malihe; Ghasemi Mohammad Amin; Jafar Eskandari Jam
Volume 12, Issue 2 , October 2019, , Pages 1-9
Abstract
In this paper the energy absorption capacity of stiffened circular composite tube is considered. The governing equations and dynamic equilibrium are first derived and then solved. Additionally, a finite element model of reinforced circular composite tube structure is modeled. At the following, the effects ...
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In this paper the energy absorption capacity of stiffened circular composite tube is considered. The governing equations and dynamic equilibrium are first derived and then solved. Additionally, a finite element model of reinforced circular composite tube structure is modeled. At the following, the effects of various parameters such as structural geometry, number of rings and stingers on mechanical behavior of such tubes are considered. The Stiffened cylinder is under axial loading and internal pressure, and boundary conditions for both sides of the cylinder are considered as simple supports. Results show increasing in the amount of energy in the stingers while the number of stingers increases, and decreasing in the amount of total energy while the number of rings and stringers are increase. Total strain energy and the strain energy created in structural elements increase by increasing the ratio of radius to thickness. The analytical solution results are in good compatibility with the results achieved from the finite element method.
M. Noorabadi; N. Namdaran; M. Rahnama; Jafar Eskandari Jam
Volume 11, Issue 2 , October 2017, , Pages 13-22
Abstract
The aim of this study is to investigatethe effective parameters on vibrations of circular cylindrical shells with fixed rotary speed andresting elastic foundation by means of analytical and finite element numerical simulation. First, the governing equations are derived using the theory of Donnell, considering ...
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The aim of this study is to investigatethe effective parameters on vibrations of circular cylindrical shells with fixed rotary speed andresting elastic foundation by means of analytical and finite element numerical simulation. First, the governing equations are derived using the theory of Donnell, considering the centrifugal forces,Coriolis acceleration, and the initial annular tension. Then, the analytical solution for cylindrical shells isintroduced under simply supported conditions. Further, the effect of parameters such as therotational speed of the shell, its lay-up, fiber angle, and the stiffness of the elastic foundation on the values of natural frequency and the critical velocity of the shells are studied. The analytical solution results are in good compatibility with the results achieved from the finite element method.
Hossein H. Shahverdi; A.S Nobari; H Bahrami Torabi
Volume 11, Issue 1 , June 2017
Abstract
The aim of this paper is to provide an aeroelastic computational tool which determines the induced wing loads during flapping flight. For this purpose, a Finite Element (FE) code based on a four-node plate bending element formulation is developed to simulate the aeroelastic behavior of flapping wings ...
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The aim of this paper is to provide an aeroelastic computational tool which determines the induced wing loads during flapping flight. For this purpose, a Finite Element (FE) code based on a four-node plate bending element formulation is developed to simulate the aeroelastic behavior of flapping wings in low incompressible flow. A quasi-steady aerodynamic model is incorporated into the aeroelastic model for predicting the aerodynamic loads. In order for the validation of the present tool, the modal and dynamic response analyses of a rotating flat plate under pure flapping motion are firstly examined and the effect of dynamic stiffness on the plate response, due to the presence of shortening terms in the equations of motion, is also investigated. Finally, the aeroelastic analysis of an insect-like wing under a specified motion is carried out and the induced loads including shear force and bending moment at the wing root are determined. The obtained results signify the contribution of wing structural elasticity to the induced loads.
F. Javidrad; F. Dabirian
Volume 7, Issue 1 , March 2010, , Pages 59-67
Abstract
In this paper, an approach to aeronautical structural design based on reliability analysis is presented. In this way, the concept of level of safety is discussed and methods of its calculation using statistical data are described. Based on the concept of level of safety, a design procedure is proposed. ...
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In this paper, an approach to aeronautical structural design based on reliability analysis is presented. In this way, the concept of level of safety is discussed and methods of its calculation using statistical data are described. Based on the concept of level of safety, a design procedure is proposed. In order to validate this design procedure, two design cases are studied. In the first case study, using finite element method, a sandwich plate containing a circular disbond between the upper faceplate and core subjected to compressive in-plane load is examined. The calculated critical buckling load and its residual strength versus disbond diameter and design load versus level of safety are compared to the existing data a good agreement is achieved. In the second case study, a delaminated sandwich beam under bending load is considered and the design load (obtained from the strain energy release rate analysis) versus level of safety is determined. The results of the study show that for the adopted visual inspection technique and a high probability of damage occurrence, the design load should be about 25% of the beam strength to achieve a reliability higher than 0.99.
Rahmatollah Ghajar; G. R. Rashed
Volume 4, Issue 3 , September 2007, , Pages 25-35
Abstract
Engineers have a range of methods to estimate the fatigue life under multiaxial conditions. Each of these predictive methods is generally subjected to restrictions, related to the inherent simplified assumptions. The objective of this paper is to evaluate the validity of commonly used multiaxial fatigue ...
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Engineers have a range of methods to estimate the fatigue life under multiaxial conditions. Each of these predictive methods is generally subjected to restrictions, related to the inherent simplified assumptions. The objective of this paper is to evaluate the validity of commonly used multiaxial fatigue criteria for different multiaxial loading conditions. The best criterion is identified through comparative analysis. The assessment is based on the experimental research findings of the SAE notched shaft, which is used as a benchmark [1]. The relative performance of three of existing multiaxial fatigue theories based on the strain criteria and the critical plane approaches are investigated. There is not any fixed strain life criterion that can predict the fatigue life best for different loading. Among all the critical plane models considered, Fatemi and Socie model [2] gives best fatigue life prediction for both multiaxial in phase and 90° out of phase loading cases.
F. Javidrad
Volume 4, Issue 1 , March 2007, , Pages 25-32
Abstract
This paper studies the application of an inverse methodology for problem solving in fracture mechanics using the finite element analysis. The method was applied to both detection of subsurface cracks and the study of propagating cracks. The procedure for detection of subsurface cracks uses a first order ...
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This paper studies the application of an inverse methodology for problem solving in fracture mechanics using the finite element analysis. The method was applied to both detection of subsurface cracks and the study of propagating cracks. The procedure for detection of subsurface cracks uses a first order optimization analysis coupled with a penalty function to solve for the unknown geometric parameters associated with the internal flaw. The objective function is calculated from normalizing the finite element determined displacements by the prescribed ones at some arbitrary points of the damaged component. The technique was also used for determination of the propagating both 1-D and 2-D planar crack growth directions using the well known maximum strain energy release rate criterion. In all cases studied, a good agreement between the theoretical and/or the experimentally observed crack behavior and the developed technique is achieved.