Flexural rigidity

About: Flexural rigidity is a research topic. Over the lifetime, 3829 publications have been published within this topic receiving 56780 citations.

A novel variable stiffness mechanism for dielectric elastomer actuators

Abstract: In this paper, a novel variable stiffness mechanism is proposed for the design of a variable stiffness dielectric elastomer actuator (VSDEA) which combines a flexible strip with a DEA in a dielectric elastomer minimum energy structure The DEA induces an analog tuning of the transverse curvature of the strip, thus conveniently providing a voltage-controllable flexural rigidity The VSDEA tends to be a fully flexible and compact structure with the advantages of simplicity and fast response Both experimental and theoretical investigations are carried out to reveal the variable stiffness performances of the VSDEA The effect of the clamped location on the bending stiffness of the VSDEA is analyzed, and then effects of the lengths, the loading points and the applied voltages on the bending stiffness are experimentally investigated An analytical model is developed to verify the availability of this variable stiffness mechanism, and the theoretical results demonstrate that the bending stiffness of the VSDEA decreases as the applied voltage increases, which agree well with the experimental data Moreover, the experimental results show that the maximum change of the relative stiffness can reach about 8880% It can be useful for the design and optimization of active variable stiffness structures and DEAs for soft robots, vibration control, and morphing applications

Numerical study on the flexural capacity of ultra-light composite timber sandwich panels

Abstract: The flexural stiffness and ultimate load capacity of novel ultralight composite sandwich panels, made of plywood faces and bamboo or peeling cores are investigated herein. Modified Ritz method and sandwich beam theory formulations for composite sandwich panels with thick faces and thick/stiff cores are developed, and are used to find the bending stiffness of the panels in one-way and two-way bending. The ultimate capacity and failure modes of the panels are then predicted from nonlinear material and geometric finite element analyses (FEA). The numerical methods are validated against published experimental results of orthotropic composite sandwich panels. It is shown that at similar panel depths, the proposed composite timber panels can be as high as 15% stiffer and 40% lighter than the existing commercial cross-laminated timber (CLT) panels. Results of a parametric study on selected composite panels with different yield stresses in compression, show that panels with bamboo cores exhibit relatively more ductile behaviour compared to those with peeling cores. At the ultimate flexural capacity, the tensile face of the panels fails in tension parallel to the grain, while the compressive face almost reaches its yield capacity.

Postcracking stiffness of reinforced concrete beams in torsion and bending

Abstract: THEORETICAL EXPRESSIONS FOR THE POSTRCRACKING STIFFNESS OF RECTANGULAR REINFORCED CONCRETE BEAMS IN TORSION AND BENDING ARE DESCRIBED AND SIMPLIFIED. THEY ARE BASED ON A SPACE TRUSS MODEL. IT IS SHOWN THAT THE POSTRCRACKING TORSIONAL STIFFNESS IS NOT GREATLY INFLUENCED BY BENDING WHILE THE POSTCRACKING FLEXURAL STIFFNESS DEPENDS ON THE AMOUNT OF TORSION. REALIZING THAT THE DROP IN TORSIONAL STIFFNESS AFTER CRACKING IS GREATER THAN THE DROP IN FLEXURAL STIFFNESS, THE TORSIONAL MOMENTS AFTER CRACKING WILL BE SMALLER IN MANY CASES THAN THE ONES PREDICTED BY THE UNCRACKED STIFFNESS VALUES. THE TORSIONAL REINFORCEMENT MAY THUS BE REDUCED BY MEANS OF THE TOOLS PROVIDED IN THIS PAPER. /ACI/

Liner Buckling in Profiled Polyethylene Pipes

Abstract: Thermoplastic pipes are often manufactured with profiled walls to maximize the flexural stiffness of the pipe for a given amount of polymer. Thin elements in the profile can buckle under the influence of large earth pressures associated with deep burial or other extreme loading conditions. Earth load tests have been conducted on high density polyethylene pipes with a number of different wall profiles. Two high-pressure pipe test cells have been used to conduct these tests. Observations of local buckling in the internal liners of these products have been examined and compared to stability assessments based on the conventional equation for buckling in stiffened plate structures (following modification of that equation to an equation that defines critical strain instead of critical stress). The strain levels that develop in the liner are, however, dependent on three-dimensional bending within the pipe profile. Provided the effects of three-dimensional bending in the pipe profile are considered, the modified ...

Buckling of a soap film spanning a flexible loop resistant to bending and twisting

Abstract: A generalization of the Euler–Plateau problem to account for the energy contribution due to twisting of the bounding loop is proposed. Euler–Lagrange equations are derived in a parametrized setting and a buckling analysis is performed. A pair of dimensionless parameters govern buckling from a flat, circular ground state. While one of these is familiar from the Euler–Plateau problem, the other encompasses information about the ratio of the torsional rigidity to the bending rigidity, the twist density and the size of the loop. For sufficiently small values of the latter parameter, two separate groups of buckling modes are identified. However, for values of that parameter exceeding the critical twist density arising in Michell's study of the stability of a twisted elastic ring, only one group of buckling modes exists. Buckling diagrams indicate that a loop with greater torsional rigidity shows more resistance to transverse buckling. Additionally, a twisted flexible loop spanned by a soap film buckles at a value of the twist density less that the value at which buckling would occur if the soap film were absent.