Abstract in English:The Generalized Finite Element Method (GFEM) can be viewed as an extension of the Finite Element Method (FEM) where the approximation space is enriched by shape functions appropriately chosen. Many applications of the GFEM can be found in literature, mostly when some information about the solution is known a priori. This paper presents the application of the GFEM to the problem of structural dynamic analysis of bars subject to axial displacements and trusses for the evaluation of the time response of the structure. Since the analytical solution of this problem is composed, in most cases, of a trigonometric series, the enrichment used in this paper is based on sine and cosine functions. Modal Superposition and the Newmark Method are used for the time integration procedure. Five examples are studied and the analytical solution is presented for two of them. The results are compared to the ones obtained with the FEM using linear elements and a Hierarchical Finite Element Method (HFEM) using higher order elements.
Abstract in English:Mainly due to their low weight, low cost and ease of assembly, the adhesive bonds have emerged as a promising technology. However, the lack of adequate tools of design and control remain an obstacle to the use of the adhesives. In this work a cohesive interface model formulated within the framework of damage mechanics is applied for the simulation of decohesion during crack propagation tests. Considering the mechanical tests of aluminium/epoxy specimens, comparisons between experimental and numerical results are presented.
Abstract in English:Buckling analysis of laminated composite plates is carried out by using an efficient C0 FE model developed based on higher order zigzag theory. In this model the first derivatives of transverse displacement have been treated as independent variables to overcome the problem of C¹ continuity associated with the FE implementation of the plate theory. The C0 continuity of the present FE model is compensated in the stiffness matrix calculations by using penalty parameter approach. Numerical results and comparison with other existing solutions show that the present model is very efficient in predicting the buckling responses of laminated composites.
Abstract in English:Stability analysis of laminated soft core sandwich beam has been studied by a C0 FE model developed by the authors based on higher order zigzag theory (HOZT). The in-plane displacement variation is considered to be cubic for the face sheets and the core, while transverse displacement is quadratic within the core and constant in the faces beyond the core. The proposed model satisfies the condition of stress continuity at the layer interfaces and the zero stress condition at the top and bottom of the beam for transverse shear. Numerical examples are presented to illustrate the accuracy of the present model.
Abstract in English:Steel tubular members are widely used as primary and secondary structural framing members in offshore oil and gas platforms. A platform is inherently liable to collisions from ships which can create severe structural damages in the rig. The effect of this damage has been studied by a number of researchers through investigating the impact behaviour isolated tubular members. This is while, the in-situ response of a member located in a structural frame, to lateral impact loads, is not necessarily the same as the response of an individual isolated impacted member. In this paper the behaviour of a chord member forming part of a tubular frame, subjected to impact loads, has been investigated. The tubular frame was tested experimentally by other researchers and reported in the literature. The non-linear numerical models of the frame presented by the authors have been validated against the experimental results. These validated models have been examined under both quasi-static and dynamic impact loads with operational pre-loading applied. It has been found that, in a pre-loaded frame, quasi-static impact loading results in the failure of the impacted member. Interestingly, dynamic modelling of the impact results in the dynamic instability of an adjacent bracing member. It has been noticed that, under a dynamic impact, the impacted in-situ member (located in the frame) behaves rather similarly to a pin ended isolated member. With a quasi-static impact, the impacted in-situ member follows fairly closely the response obtained for a fixed ended isolated member.
Abstract in English:Active Vibration Control (AVC) using smart structure is used to reduce the vibration of a system by automatic modification of the system structural response. AVC is widely used, because of its wide and broad frequency response range, low additional mass, high adaptability and good efficiency. A lot of research has been done on Finite Element (FE) models for AVC based on Euler Bernoulli Beam Theory (EBT). In the present work Timoshenko Beam Theory (TBT) is used to model a smart cantilever beam with surface mounted sensors / actuators. A Periodic Output Feedback (POF) Controller has been designed and applied to control the first three modes of vibration of a flexible smart cantilever beam. The difficulties encountered in the usage of surface mounted piezoelectric patches in practical situations can be overcome by the use of embedded shear sensors / actuators. A mathematical model of a smart cantilever beam with embedded shear sensors and actuators is developed. A POF Controller has been designed and applied to control of vibration of a flexible smart cantilever beam and effect of actuator location on the performance of the controller is investigated. The mathematical modeling and control of a Multiple Input multiple Output (MIMO) systems with two sensors and two actuators have also been considered.