Papers by Keyword: Large Deflection

Abstract: Due to thin skins and soft core, it is apt to local indentation inducing the concurrence of geometrical and material nonlinearity in sandwich structures. In the paper, finite element simulation is used to investigate the bending behavior of lightweight sandwich beams under large deflection. A modified formulation for the moment at mid-span section of sandwich beams under large deflection is presented, and energy absorption performance is assessed based on energy absorption efficiency. In addition, it is found that no local indentation arises initially, while later that increases gradually with loading displacement increasing. The height of the mid-span section as well as load-carrying capacity decreases significantly with local indentation depth increasing.

Abstract: A theoretical research is carried out to study the large deflection response of a fully clamped rectangular metal sandwich plates with functionally graded foam core subjected to blast loading. Using a new yield criterion for sandwich cross-section with graded foam core, we obtained the analytical solutions for the dynamic response of rectangular sandwich plates. Finite element simulations with gradient layers foam core model are performed to study the dynamic response of the sandwich plates with graded foam core subjected to blast loading. The results of the analyses seem to predict well the deflections that are given numerically.

Abstract: This study explores the curvature and mechanical sensitivity of a pre-stressed layered plate embedded with a piezoelectric layer in large deflection. Piezoelectric effect was included in deriving the nonlinear governing equations but the arising nonlinear terms are neglected, yielding a standard Bessel equation or a modified Bessel equation for the lateral slope. Analytical solutions are developed and further manipulated to obtain lateral curvature and mechanical sensitivity. The results for a nearly monolithic plate under low pretension and low voltage applied across the piezoelectric layer agree well with those of CPT for a single-layered plate under pure mechanical loading. For typical symmetric 3-layered piezoelectric plates, the solutions show that, piezoelectric effect is apparent only up to a moderate initial tension. Beyond a moderate threshold value, the pretension turns to be dominant, resulting in nearly zero curvature and uniform mechanical sensitivity throughout the entire plate.

Abstract: The high precision numerical method for solving nonlinear bending problems of large deflection beam is presented. The governing equation of large deflection beam is a strongly nonlinear ordinary differential equation. Using the solution of linear bending beam as an initial guess function, the nonlinear bending equation of beam can be transferred into a linear differential equation. The improvement solution of nonlinear bending beam is obtained by solving the linearized bending equation using barycentric interpolation collocation method. Then, the solution of nonlinear bending beam can be given by iterative method. Some examples demonstrate the validity and computational accuracy of proposed method.

Abstract: Foam sandwich beams with sine-curve skins subjected to large deflection were studied using finite element analysis, in which damage mechanisms of face sheet were introduced. Sandwich beams with various sinusoidal skins were simulated and results indicated that corrugation could make the deflection and energy absorption up to face fracture increase remarkably compared to the counterpart with planar skins.

Abstract: The objective of this work is to study the large deflection of a pin-supported slender geometrically asymmetric metal foam core sandwich beam under transverse loading by a flat punch. Based on the yield criterion for geometrically asymmetric metal foam core sandwich structure, analytical solution for the large deflection of a pin-supported slender sandwich beam is obtained, in which the interaction of bending and stretching induced by large deflection is considered. The finite element results confirm the accuracy of the analytical solutions. The effects of asymmetric factor and boundary condition on the structural response of the asymmetric sandwich beam are discussed in detail. It is shown that the axial stretching induced by large deflection plays an important role in the load-carrying and energy absorption capacities of geometrically asymmetric sandwich structure.

Abstract: An analytic model is developed to obtain the dynamic response of beams with initial velocities of the upper beam which is clamped at both ends and fully supported by metal foam, as a representative arrangement for protective structures. In large deflection, plastic bending and stretching in deforming regions are considered and the membrane factor method is introduced in the model to take into account the effect of axial force in the yielding. The relationships between the final displacement of the center in the beam and the dimensionless parameters are obtained. This model can predict the dynamic effects of different initial velocities and beams with different lengths, thickness and yield strength of cores.

Abstract: This work examines the resistance of metal sandwich plates with corrugated core subjected to impulsive loading over central patch, in which effects of the low-density polymeric foam filling the interstices of the corrugated core on dynamic response of sandwich plate are studied to ascertain the enhancement of sandwich plate under impulsive loading. The face sheets and corrugated core are made of the same metal materials. The resistance of the metal sandwich plates with foam-filled cores is compared to that of the metal sandwich plates with unfilled core with the same weight. The results of comparison show that the foam-filled core does not make the overall deflection decrease compared with empty core, but it can make the sandwich plate achieve multifunctional advantages. The membrane method is employed to predict large deflection response of metal sandwich plates with foam-filled and unfilled cores under impulsive loading over a central patch. The theoretical predictions agree well with FE results of sandwich plates with foam-filled and empty cores.

Abstract: The limit displacement was calculated with regard to a large deflection tunnel. The continuum calculation model was established with actual parameters of the surrounding rock of the tunnel as input. In the simulation calculation, the action occasion of the support structure was determined based on the ratio of the measured rock pressure to the geo-stress, and the bearing capacity of the R.C. compressive bending component of the support was expressed with the axial force and bending moment on losing capacity of the support structure in loading; The limit displacement of the tunnel wais determined finally combined with the measured displacement of control points on collapsed or gauge-intrusive sections and cracked primary support or secondary lining sections. Since the deforming rate is more concerned than the displacement in drill and blast tunnel construction, three-level-management of deflection and deforming rate was proposed based on the statistical analysis of measured deforming rate, and the safety requirement for deflection control in construction. The management criterion has reference value to other similar tunnels where difficulty is encountered due to large deflection occurring in construction.

Abstract: This paper reviews research on the large deflection of the orthotropic and rectangular membrane under the distributed load. Through building the theoretical model of the orthotropic and rectangular membrane under the distributed load, the authors deduce the equations set of the membrane which has the effect of pretension and solve the equations set with the perturbation method. The authors obtain the relational expression between the maximum deflection of the membrane’s centre point and the external load, then make a comparison between the large deflection and the small deflection. At last, With the example, the authors analyze the change of the deflection of the centre point of the membrane along the external load, and the length of the side, and the large or small of the pretension and other parameter.