Accurate Free Vibration Analysis of Launcher Structures Using Refined 1D Models

Erasmo Carrera,Enrico Zappino,Tommaso Cavallo 한국항공우주학회 2015 International Journal of Aeronautical and Space Sc Vol.16 No.2

This work uses different finite element approaches to the free vibration analysis of reinforced shell structures, and a simplified model of a typical launcher with two boosters is used as an example. The results obtained using a refined one-dimensional (1D) beam model are compared to those obtained with commercial finite element software. The 1D models that are used in the present work are based on the Carrera Unified Formulation (CUF), which assumes a variable kinematic displacement field over the cross-sections of the beam. Two different sets of polynomials that correspond to Taylor (TE) or Lagrange (LE) expansions were used. The analyses focused on three reinforced structures: a stiffened panel, a reinforced cylinder and the complete structure of the launcher. The frequencies and natural modes obtained using one-dimensional models are compared to those obtained from classical finite element analysis. The classical FE models were built using a beam-shell or solid elements, and the results indicate that the refined beam models can in fact be used to investigate the behavior of very complex reinforced structures. These models can predict the shell-like modes that are typical of thin-walled structures that cannot be detected using classical beam models. The refined 1D models used in the present work provide results that are as accurate as those from solid FE models, but the 1D models have a much lower computational cost.

Static analysis of shear-deformable shells of revolution via G.D.Q. method

Erasmo Viola,Edoardo Artioli 국제구조공학회 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.19 No.4

This paper deals with a novel application of the Generalized Differential Quadrature (G.D.Q.) method to the linear elastic static analysis of isotropic rotational shells. The governing equations of equilibrium, in terms of stress resultants and couples, are those from Reissner-Mindlin shear deformation shell theory. These equations, written in terms of internal-resultants circular harmonic amplitudes, are first put into generalized displacements form, by use of the strain-displacements relationships and the constitutive equations. The resulting systems are solved by means of the G.D.Q. technique with favourable precision, leading to accurate stress patterns.

Comparative Safety of Long-Acting Injectable Antipsychotics: A Systematic Review and Network Meta-Analysis

Erasmo Saucedo Uribe,Samuel Enrique Olivares Mundo,Raul Ricardo Medrano Garza,Fernando Diaz Gonzalez-Colmenero,Lorena Martinez Sanchez,Cesar Bigran Espinosa Cantu,Martin Moreno Arellano,Yessica Yaneth 대한신경정신의학회 2023 PSYCHIATRY INVESTIGATION Vol.20 No.12

Objective To find the safety of long-acting injectable antipsychotics (LAIs) compared to each other, and/or placebo in the treatment of schizophrenia (SCZ) and/or schizoaffective disorder (SZA).Methods We performed a systematic review and a network meta-analysis of randomized controlled trials (RCTs) comparing the safety of LAIs versus other LAIs or placebo in adults diagnosed with SCZ or SZA. The primary outcomes were treatment emergent adverse events (TEAEs), serious treatment emergent adverse events (STEAEs), and deaths. The secondary outcomes included treatment discontinuations due to adverse events and all-cause discontinuations.Results Seventeen RCTs were included (n=7,908). There were no significant differences between LAIs and placebo in the risk of presenting TEAEs. LAIs had a significant lower risk of presenting STEAEs except for aripiprazole. No significant differences in deaths were found. LAIs showed a significant protective effect against all-cause discontinuation, except for haloperidol. Only aripiprazole had a significantly lower risk of treatment discontinuation due to adverse events.Conclusion We found no significant differences in the risk of presenting TEAEs between LAIs and placebo. The majority of LAIs had a significantly lower risk of presenting STEAEs than placebo. Development of international guidelines for the report of safety outcomes related to antipsychotics especially for LAIs in clinical trials could minimize report and interpretation biases and improve the accuracy of posterior meta-analysis.

Accurate Free Vibration Analysis of Launcher Structures Using Refined 1D Models

Carrera, Erasmo,Zappino, Enrico,Cavallo, Tommaso The Korean Society for Aeronautical and Space Scie 2015 International Journal of Aeronautical and Space Sc Vol.16 No.2

This work uses different finite element approaches to the free vibration analysis of reinforced shell structures, and a simplified model of a typical launcher with two boosters is used as an example. The results obtained using a refined one-dimensional (1D) beam model are compared to those obtained with commercial finite element software. The 1D models that are used in the present work are based on the Carrera Unified Formulation (CUF), which assumes a variable kinematic displacement field over the cross-sections of the beam. Two different sets of polynomials that correspond to Taylor (TE) or Lagrange (LE) expansions were used. The analyses focused on three reinforced structures: a stiffened panel, a reinforced cylinder and the complete structure of the launcher. The frequencies and natural modes obtained using one-dimensional models are compared to those obtained from classical finite element analysis. The classical FE models were built using a beam-shell or solid elements, and the results indicate that the refined beam models can in fact be used to investigate the behavior of very complex reinforced structures. These models can predict the shell-like modes that are typical of thin-walled structures that cannot be detected using classical beam models. The refined 1D models used in the present work provide results that are as accurate as those from solid FE models, but the 1D models have a much lower computational cost.

The G. D. Q. method for the harmonic dynamic analysis of rotational shell structural elements

Viola, Erasmo,Artioli, Edoardo Techno-Press 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.17 No.6

This paper deals with the modal analysis of rotational shell structures by means of the numerical solution technique known as the Generalized Differential Quadrature (G. D. Q.) method. The treatment is conducted within the Reissner first order shear deformation theory (F. S. D. T.) for linearly elastic isotropic shells. Starting from a non-linear formulation, the compatibility equations via Principle of Virtual Works are obtained, for the general shell structure, given the internal equilibrium equations in terms of stress resultants and couples. These equations are subsequently linearized and specialized for the rotational geometry, expanding all problem variables in a partial Fourier series, with respect to the longitudinal coordinate. The procedure leads to the fundamental system of dynamic equilibrium equations in terms of the reference surface kinematic harmonic components. Finally, a one-dimensional problem, by means of a set of five ordinary differential equations, in which the only spatial coordinate appearing is the one along meridians, is obtained. This can be conveniently solved using an appropriate G. D. Q. method in meridional direction, yielding accurate results with an extremely low computational cost and not using the so-called "delta-point" technique.

Nonhomogeneous atherosclerotic plaque analysis via enhanced 1D structural models

Alberto Varello,Erasmo Carrera 국제구조공학회 2014 Smart Structures and Systems, An International Jou Vol.13 No.4

The static analysis of structures with arbitrary cross-section geometry and material lamination via a refined one-dimensional (1D) approach is presented in this paper. Higher-order 1D models with a variable order of expansion for the displacement field are developed on the basis of Carrera Unified Formulation (CUF). Classical Euler-Bernoulli and Timoshenko beam theories are obtained as particular cases of the first-order model. Numerical results of displacement, strain and stress are provided by using the finite element method (FEM) along the longitudinal direction for different configurations in excellent agreement with three-dimensional (3D) finite element solutions. In particular, a layered thin-walled cylinder is considered as first assessment with a laminated conventional cross-section. An atherosclerotic plaque is introduced as a typical structure with arbitrary cross-section geometry and studied for both the homogeneous and nonhomogeneous material cases through the 1D variable kinematic models. The analyses highlight limitations of classical beam theories and the importance of higher-order terms in accurately detecting in-plane cross-section deformation without introducing additional numerical problems. Comparisons with 3D finite element solutions prove that 1D CUF provides remarkable three-dimensional accuracy in the analysis of even short and nonhomogeneous structures with arbitrary geometry through a significant reduction in computational cost.

The G. D. Q. method for the harmonic dynamic analysis of rotational shell structural elements

Edoardo Artioli,Erasmo Viola 국제구조공학회 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.17 No.6

Static Aeroelastic Response of Wing-Structures Accounting for In-Plane Cross-Section Deformation

Alberto Varello,Alessandro Lamberti,Erasmo Carrera 한국항공우주학회 2013 International Journal of Aeronautical and Space Sc Vol.14 No.4

In this paper, the aeroelastic static response of flexible wings with arbitrary cross-section geometry via a coupled CUFXFLR5 approach is presented. Refined structural one-dimensional (1D) models, with a variable order of expansion for the displacement field, are developed on the basis of the Carrera Unified Formulation (CUF), taking into account cross-sectional deformability. A three-dimensional (3D) Panel Method is employed for the aerodynamic analysis, providing more accuracy with respect to the Vortex Lattice Method (VLM). A straight wing with an airfoil cross-section is modeled as a clamped beam, by means of the finite element method (FEM). Numerical results present the variation of wing aerodynamic parameters, and the equilibrium aeroelastic response is evaluated in terms of displacements and in-plane cross-section deformation. Aeroelastic coupled analyses are based on an iterative procedure, as well as a linear coupling approach for different free stream velocities. A convergent trend of displacements and aerodynamic coefficients is achieved as the structural model accuracy increases. Comparisons with 3D finite element solutions prove that an accurate description of the in-plane crosssection deformation is provided by the proposed 1D CUF model, through a significant reduction in computational cost.

Effect of boundary conditions on the stability of beams under conservative and non-conservative forces

Marzani, Alessandro,Viola, Erasmo Techno-Press 2003 Structural Engineering and Mechanics, An Int'l Jou Vol.16 No.2

This paper, which is an extension of a previous work by Viola et al. (2002), deals with the dynamic stability of beams under a triangularly distributed sub-tangential forces when the effect of an elastically restrained end is taken into account. The sub-tangential forces can be realised by a combination of axial and tangential follower forces, that are conservative and non-conservative forces, respectively. The studied beams become unstable in the form of either flutter or divergence, depending on the degree of non-conservativeness of the distributed sub-tangential forces and the stiffness of the elastically restrained end. A non-conservative parameter ${\alpha}$ is introduced to provide all possible combinations of these forces. Problems of this kind are usually, at least in the first approximation, reduced to the analysis of beams according to the Bernoulli-Euler theory if shear deformability and rotational inertia are negligible. The equation governing the system may be derived from the extended form of Hamilton's principle. The stability maps will be obtained from the eigenvalue analysis in order to define the divergence and flutter domain. The passage from divergence to flutter is associated with a noticeable lowering of the critical load. A number of particular cases can be immediately recovered.

Further results on the development of a novel VTOL aircraft, the Anuloid. Part II: Flight mechanics

Petrolo, Marco,Carrera, Erasmo,Visser, Coen de,D'Ottavio, Michele,Polit, Olivier Techno-Press 2017 Advances in aircraft and spacecraft science Vol.4 No.4

This paper presents the main outcomes of the preliminary development of the Anuloid, an innovative disk-shaped VTOL aircraft. The Anuloid has three main features: lift is provided by a ducted fan powered by a turboshaft; control capabilities and anti-torque are due to a system of fixed and movable surfaces that are placed in the circular internal duct and the bottom portion of the aircraft; the Coanda effect is exploited to enable the control capabilities of such surfaces. In this paper, results from flight mechanics are presented. The vertical flight dynamics were found to be desirable. In contrast, the horizontal flight dynamics of the aircraft shows both dynamic instability, and more importantly, insufficient pitch and roll control authority. Some recommendations and guidelines are then given aimed at the alleviation of such problems.