ANALYTICAL STUDY OF FLEXURAL BEHAVIOR OF COLD FORMED STEEL SECTIONS WITH AND WITHOUT PERFORATION

This work is about the investigation of flexural behavior cold formed steel member of different cross sections with and without perforation under similar cross sectional area. This work gives idea about the performance of different sections under same loading condition among selected sections and highlights the increasing the flexural strength of member by using stiffener arrangement. In this work three different cross sectional shapes are selected which are C – section, Z – section and Hat shaped section of same cross sectional area analyzed with and without lip under same loading and end condition as well as with perforation. The selected specimens were analyzed analytically using ANSYS Workbench software which shown better comparison among analyzed different geometries of members. Effectiveness of providing edge stiffener to different perforated sections also determined in this work.

Parametric modal analysis of an induced-strain actuated wing-like plate for pitch and heave coupling response

This article investigates the feasibility of a plate-like flapping wing with varying geometric and boundary conditions actuated by surface-bonded piezoelectric material devices. The most influential structural parameters that vary dynamic response and heave–pitch mode coupling are investigated. An analytically and experimentally validated dynamic finite element model is developed to analyze the structure. A parametric analysis is conducted by varying critical geometric parameters and boundary conditions, such as aspect ratio, actuator position, actuator angle, clamp size, and position; substrate thickness variation; and substrate-to-actuator-thickness ratio. Response metrics representing heave and pitch motions are taken as longitudinal curvature and lateral slope, respectively—the surface regression analysis and results leading to these choices are presented. Maximum longitudinal curvature and lateral slope amplitudes and phase shifts are reported for key parameter choices. Longitudinal curvature to lateral slope coupling is achieved with the introduction of a leading edge stiffener to the otherwise uniform thickness plate. Conditions and parameters that lead to and influence heave–pitch coupling are presented and discussed in detail. This article presents a unique approach to flapping mode of flight compared to the literature. The article proposes a purely induced-strain actuation approach rather than the typical “mechanisms” based approach.

Induced Strain Actuation for Solid-State Ornithopters: Pitch and Heave Coupling

This paper investigates the heaving and pitching of a wing-like parameterized cantilevered plate with a leading edge stiffener and clamp variation when actuated with a surface-bonded piezoelectric actuator. The response is analyzed using a finite element model that is validated by comparison with known analytical solutions. The validated finite-element model is subjected to a harmonic excitation parametric analysis. The parameters varied in the model are the root clamped percentage, leading edge stiffener thickness, and the aspect ratio of the plate. The model is examined at the first two Eigen frequencies. Metrics of heaving and pitching are developed using surface fitting methods and their amplitudes and phases are reported throughout the parameter space. Emphasis is placed on the interaction and coupling of the first two modes of vibration with respect to the parameters. A piezo-composite wing prototype is fabricated and actuated harmonically with a Macro-Fiber Composite actuator while leading edge stiffener thickness and root clamped percentage is varied. The resulting experimental data is used to further validate the theoretical models.

Buckling Of The Stiffened Flange Of The Thin-Walled Member At Longitudinal Stress Variation

Buckling of the stiffened flange of a thin-walled member is reduced to the buckling analysis of the cantilever plate, elastically restrained against rotation, with the free edge stiffener, which is susceptible to deflection. Longitudinal stress variation is taken into account using a linear function and a 2nd degree parabola. Deflection functions for the plate and the stiffener, adopted in the study, made it possible to model boundary conditions and different buckling modes at the occurrence of longitudinal stress variation. Graphs of buckling coefficients are determined for different load distributions as a function of the elastic restraint coefficient and geometric details of the stiffener. Exemplary buckling modes are presented.

Transfer of Load From an Edge-Stiffener to a Sheet—A Reconsideration of Melan’s Problem

The problem posed by the diffusion of load from an infinite edge-stiffener into a semi-infinite elastic sheet is reconsidered under two alternative refinements of the underlying stiffener model. First, the stiffener is regarded as an elastic strip of finite width, and the theory of generalized plane stress is applied rigorously to the sheet and stiffener alike. Next, Melan’s one-dimensional treatment of the stiffener is amended to account for its bending rigidity. The “exact” and the intermediate approximate solution thus obtained are compared to Melan’s results with particular attention to the relevant asymptotic behavior in the vicinity of the applied load and at large distances from the load. Comparative numerical results, showing the variation of the sheet stresses at the interface and the distribution of the axial stiffener force, are included.