Stall Flutter Analysis of High-Aspect-Ratio Composite Wing

Given the vast advancements in computing power in the last several decades, nonlinear dynamic analysis has gained wide acceptance by practicing engineers as a useful way of assessing and improving the seismic performance of structures. Nonlinear structural analysis software packages give engineers the ability to directly model nonlinear component behavior in detail, resulting in improved understanding of how a building will respond under strong earthquake shaking. One key component, in particular, for understanding the behavior of moment-resisting frames is the plastic rotation of the flexural hinges. Performance-based standards typically use plastic rotation as the primary parameter for defining the acceptance criteria in moment-resisting frames. Since plastic rotation is a key parameter in the seismic damage assessment, the concept as well as the method to calculate this quantity must be understood completely. Though engineers rely on the plastic rotation output from seismic structural analysis software packages to determine acceptable performance, the actual calculation methods used in achieving such plastic rotation quantities usually lay within a so-called “black box”. Based on the outputs obtained from most structural analysis software packages, it can be shown that running an algorithm considering material nonlinearity by itself will produce reasonably accurate results. Moreover, separately running an algorithm considering geometric nonlinearity also can produce accurate results. However, when material nonlinearity is combined with geometric nonlinearity in an analysis, obtaining accurate results or even stable solutions is more difficult. The coupling effect between the two nonlinearities can significantly affect the global response and the local plastic rotation obtained from the analysis and therefore needs to be verified through some analytical means. Yet, the verification process is difficult because a robust analytical framework for calculating plastic rotation is currently unavailable and urgently needed. In view of this gap, an improved analytical approach based on small displacement theory is derived to calculate the plastic rotations of plastic hinges at various locations of moment-resisting frames. Both static and dynamic analysis with nonlinear geometric effects will be incorporated in the derivation. Here the element stiffness matrices are first rigorously derived using a member with plastic hinges in compression, and therefore the coupling of geometric and material nonlinearity effects is included from the beginning of the derivation. Additionally, plastic rotation is handled explicitly by considering this rotation as an additional nonlinear degree-of-freedom. Numerical simulation is performed to calculate the nonlinear static and dynamic responses of simple benchmark models subjected to seismic excitations. Results are compared with various software packages to demonstrate the feasibility of the proposed method in light of the output results among software packages in calculating plastic rotations.

Geometrically nonlinear theory of thin-walled composite box beams using shear-deformable beam theory

The problem of forced vibration of a hinged beam with piezoelectric layers is solved. Issues of mechanical and electric excitation of vibration and the possibility of damping mechanically induced vibration by applying a voltage to the electrodes of the piezolayers are studied. The effect of the physically nonlinear behavior of the passive layers on the response of the sensor layer and entire structure and the effect of geometric nonlinearity on the behavior of the structure and sensor layer are analyzed. The interaction of physical and geometrical nonlinearities for transient and stationary processes is studied

Membrane materials are widely used in construction engineering with small mass and high flexibility, which presents strong geometric nonlinearity in vibration. In this paper, an improved multiscale perturbation method is used to solve the aerostatics stability of membrane roofs on closed and open structures by quantifying the effect of geometric nonlinearity on the single-mode aeroelastic instability wind velocity. Results show that the critical wind velocities of two models are smaller when the geometrical nonlinearity of the membrane material is neglected. In addition, under normal wind load, the influence of geometrical nonlinearity of the membrane on the aerodynamic stability of the roof can be neglected. However, under strong wind load, when the roof deformation reaches 3% of the span, the influence of geometric nonlinearity should be considered and the influence increases with the decrease of transverse and downwind span of the membrane roof. The results obtained in this paper have an important theoretical reference value for the design membrane structures.

Technical Briefs Effect of Geometrical Nonlinearity on the Minimum Mass Design of Fully Stressed Beams M. K. Verma, M. K. Verma Indian Institute of Science, Bangalore, India Search for other works by this author on: This Site PubMed Google Scholar A. V. Krishna Murty A. V. Krishna Murty Department of Aeronautical Engineering, Indian Institute of Science, Bangalore, India Search for other works by this author on: This Site PubMed Google Scholar Author and Article Information M. K. Verma Indian Institute of Science, Bangalore, India A. V. Krishna Murty Department of Aeronautical Engineering, Indian Institute of Science, Bangalore, India J. Appl. Mech. Jun 1972, 39(2): 627-628 (2 pages) https://doi.org/10.1115/1.3422742 Published Online: June 1, 1972 Article history Received: September 1, 1971 Revised: February 1, 1972 Online: July 12, 2010

This paper develops a numerical formulation for the nonlinear time-dependent analysis of steel-concrete composite members that are curved arbitrarily in space, which includes the effects of concrete shrinkage, creep, and geometric nonlinearity. This formulation is applicable to the analysis of composite arches and composite beams curved in plan, representing the limiting cases of members that are vertically and horizontally curved. The flexibility of the shear connection at the interface surface between the steel girder and the concrete deck is taken into consideration in the formulation. For an accurate serviceability limit state analysis of composite curved members, it is essential to include the shrinkage and creep response of the concrete component in the analysis. To also include the effects of geometric nonlinearity, a step-by-step incremental iterative solution procedure is adopted. Comparisons of the numerical solutions with those based on much less efficient and tractable viscoelastic ABAQUS shell element models, and with available experimental results, verify the accuracy of the computational formulation that is developed. Examples are chosen to illustrate the effects of partial interaction and initial curvature on the time-dependent behavior of spatially curved composite beams.

Nano-switch structures are important control elements in nanoelectromechanical systems and have potential applications in future nanodevices. This paper analyzes the effects of surface effects, geometric nonlinearity, electrostatic forces, and intermolecular forces on the nonlinear bending behavior and adhesion stability of nano-switches. Based on the Von Karman geometric nonlinearity theory, four types of boundary conditions for the nano-switch structure were specifically calculated. The results show that surface effects have a significant impact on the nonlinear bending and adhesion stability of nano-switches. Surface effects increase the adhesion voltage of the nano-switch and decrease its adhesion displacement, and as the size of the nano-switch structure increases, the impact of surface effects decreases. A comparative analysis of the linear theory and the nonlinear theory results shows that the adhesion voltage predicted by the linear theory is smaller than that predicted by the nonlinear theory. The effect of geometric nonlinearity increases as the size of the nano-switch structure increases, as the distance between the electrodes increases, and as the aspect ratio of the nano-switch structure increases. These findings provide theoretical support and reference for the design and use of future nanodevices and nanoelectromechanical systems.

NONLINEAR RESPONSE OF A NON-ROTATING ROTOR BLADE TO A PERIODIC GUST

In this paper we reviewed the research on the dynamic response of forced vibrations of orthotropic membranes, which applies in the membrane structural engineering. We applied the large deflection theory of membranes, the D’Alembert’s principle and the momentum theorem to derive the fundamental equations of forced vibrations of orthotropic membranes, which we solved according to the Lindstedt Poincaré Perturbation Method, and obtained the formula of impact load and nonlinear forced vibration deflection of rectangular membranes with four edges fixed. Then a numerical computation method for the equation was applied. The results of practical examples are shown and discussed in the paper. This paper provide a method for analyzing some practical engineering problems and furthermore the nonlinear governing equations of forced vibration and the solving method provide some theoretical foundation for the .research relating to the solving of membrane structures under dynamic loads by comprehensively considering the effects of material nonlinearity, geometric nonlinearity and viscous damping.

This research work aims to evaluate the dynamic structural behaviour of tall buildings when subjected to wind loads considering the effect of the geometric nonlinearity and also the aerodynamic damping, due to the relative movement between the structure and the wind action. This way, the project associated to a steel-concrete composite building with 48 floors and 172.8 m height is investigated, when subjected to wind nondeterministic dynamic actions. The composite building finite element model was developed based on the use of the Finite Element Method (FEM), utilising the ANSYS computational program, and considering the soil-structure interaction effect, aiming to obtain a realistic representation of the dynamic behaviour. The building dynamic response was obtained based on the displacements and accelerations values, determined having in mind a wind velocity range between 5 m/s [18 km/h] and 45 m/s [162 km/h]. The conclusions of this investigation pointed out to the fact that when the geometric nonlinearity effect was considered in the analysis the investigated building dynamic response presented relevant differences, with maximum differences up to 30% to horizontal translational displacements and up to 45% to accelerations. On the other hand, when the aerodynamic damping was considered the contribution was not significant to the structure dynamic response, with maximum differences up to 5% for the displacements and up to 10% for the accelerations.

In this paper, a wind tunnel experiment model for elastic aircraft with high-aspect-ratio is designed. The numerical simulation method is used to predict the state of the wind tunnel experiment, and the low-speed wind tunnel experiment is carried out. The purpose of this study is to verify the effect of geometric nonlinearity on the aerodynamic force of aircraft with high-aspect-ratio, and to obtain the aeroelastic trim parameters and influence of elastic deformation on aerodynamic forces. Some parts of the model are fabricated by 3-D print using nylon to reduce weight. The aircraft aeroelastic deformation is measured using the principle of binocular vision measurement, aerodynamic is measured using balance and angle of attack is measured using attack angle sensor. the elastic deformation is simulated coupled CFD method and finite state induced inflow aerodynamic model with geometrical exact intrinsic beam model which can accurately describe the geometrical nonlinear effect of high-aspect-ratio wing. By comparing the experimental data and numerical simulation results, the the influence of geometric nonlinear effect on aerodynamic force is quantitatively evaluated. Research show that the wind tunnel experiment device and supporting measurement device built for high aspect ratio aircraft can effectively acquire the influence of geometric nonlinearity on aircraft aerodynamic force.

Geometric nonlinear analysis of simply supported antisymmetric angle-ply laminated composite plates are investigated based on first order and higher order displacement models with five degrees of freedom. Analytical formulations and solutions are developed based on Von-Karman nonlinear plate theory and Taylor's series expansion of displacement components. Equations of equilibrium are obtained using Principle of Minimum Potential Energy (PMPE) and closed form solutions using Navier's Solution technique. A four layered square plate is considered for the present study. Parametric studies are performed on both the models to study the behaviour of displacements and stresses in laminated composite plates. Comparative studies are performed on both the models and the effect of geometric nonlinearity is discussed.

The cable tower is the bearing component of long-span suspension bridges, and its structure is very high and bear large force, which determines the stability and is the key of safety control. As for the height of the main tower of a long-span suspension bridge up to 195.3 m, the finite element software ANSYS is used to establish a three-dimensional finite element model (FEM), and the effects of geometric nonlinearity and material nonlinearity on the stability of the main tower are analyzed. The calculation results show that geometrical nonlinearity and material defects have significant influence on the main tower stability, and the nonlinear stability should be considered under wind load in the design calculation.

A tuned mass damper (TMD) on top flexible structures may sustain considerable rotation because of the significant flexural deformation of the supporting structure. The effects of such rotation on the vibration reduction performance are generally neglected in the analysis and design of TMD-controlled systems, by assuming that the mass moves only laterally in a fixed global coordinate. This technical note critically reviews this assumption by comparing the dynamic responses of a lumped-mass Euler beam with a TMD on top in either fixed or corotational coordinates to harmonic ground excitations. The results show that the corotational local coordinate of TMDs, which introduces geometric nonlinearity into the system, tends to bias the peaks of the frequency response curve toward lower excitation frequency, but such an effect is less profound than that induced by the P- Δ effect, another source of geometric nonlinearity in the system. The relative error in the peak frequency response of neglecting this effect increases for larger lateral drift of the supporting structure and smaller mass ratio of the TMD. An empirical equation for estimating this error is proposed to assist the decision-making of whether this assumption is appropriate for specific applications of TMDs.

Firstly the tension experiment was undertaken to investigate the mechanic behaviors of the flange repaired composite panels in this paper. Emphases were played on the damage initiation and the failure strength for the repaired composite structure. Then numerical studies were conducted by using finite element method. The effect of geometric non-linearity on the stress-strain response was taken into account through quadrilateral, thick shell elements (S8R). A better agreement with experiment could be obtained when geometric non-linearity was considered. In addition, a user material subroutine (UMAT) was implemented into ABAQUS for studying damage initiation and its progression in the composite structure. Finally, all the predicted strain distributions, damage development and strength of the repaired laminate were compared with experiments. The predictions and experiments were found to be in good agreement.