1,721,124 research outputs found
A new theoretical approach for structural modelling of riveted and spot welded multi-spot structures
No full textA general theoretical approach based on theory of elasticity is presented in order to define the structural behaviour of riveted and spot welded joints. The new closed form solutions lead to the definition of a joint element useful to FE models of riveted or spot welded multi-spot structures. The objective is an accurate evaluation of the local elastic stiffness of spot joints in FE analysis, which is fundamental to perform a reliable simulation of multi-joint structures and, consequently, a good estimate of loads acting on spots; this makes it possible to introduce structural stress or new general criteria allowing, for example, to predict fatigue behaviour. On the other hand, a low entry of degrees of freedom is needed when several spot joints are present in a complex structure. The goal is to reach a reliable spot region model which can be used as the basis to develop a spot element in FE analysis. In the present paper, based on new closed form solutions, a spot element is introduced, so as to precisely evaluate both local and overall stiffness both of spot welded joints and riveted joints. Based on the stress function approach and the Kirchhoff plate theory in linear elastic hypotheses, closed-form in-plane stress, displacement, moment and transverse shear force solutions are derived for a new bidimensional model, subjected to various types of loads. The capability to simulate spot welds or rivets depends on the definition of two elastic parameters intrinsic in closed form solutions, that tunes the theoretical model according to actual joint behaviour. The proposed joint element combines the precision in the simulation with a very limited number degrees of freedom in the overall finite element model of an actual multi-spot structure. The results obtained using the introduced theoretical framework and spot element approach perfectly match those obtained using very refined FE models and experimental data. © 2009 Elsevier Ltd. All rights reserved
Sviluppo di un Elemento Punto di Saldatura per L’analisi ad Elementi Finiti di Strutture Saldate a Punti
No full text
Modellazione di una giunzione rivettata soggetta a carichi ortogonali mediante un nuovo elemento rivetto
No full textInfluenza delle Condizioni di Vincolo sul Modello Analitico del Comportamento Elasto-Plastico di Strutture Saldate a Punti
No full textCaratterizzazione analitica del fronte di plasticizzazione in strutture saldate per punti
No full textAnalytical characterization of plastic flow in spot welded joints
No full textAn analytical procedure for the evaluation of the elastic-plastic behaviour of spot welded joints, in terms of global stiffness is presented in this paper. The analytical procedure is based on a new reference theoretical model of the sheet region close to spot welded joint able to follow the evolution of plastic flow close to the joint. The new closed-form solutions allow to define the deflection of spot joint when an axial load is applied and plasticization occurred. The reference theoretical model is based on theory of elasticity and consists in a circular plate having two annular portions with different variable thickness and having a central rigid core representing the spot weld. This model allows to correctly simulate the actual plasticization radius when load increases and the global stiffness of the actual joint. The analytical procedure presented is new and lead to the definition of a spot weld finite element, able to precisely evaluate both local and overall stiffness of spot joints, also in elastic plastic field. This spot weld element lead to accurate simulation of multi spot welded structures with a very low computational effort
Influence of joint geometry on micro and macro mechanical properties of friction stir spot welded joints
No full textSpot welding can be considered a very common joining technique in automotive and transportation industries as it permits to obtain effective lap-joints with short process times and what is more it is easily developed through robots and automated systems. Recently, Friction Stir Spot Welding (FSSW) has been proposed as a natural evolution of the already known Friction Stir Welding (FSW) process, allowing to obtain sound spot joints that do not suffer from the insurgence of typical welding defects due to the melting of the base material. Similarly to FSW, both geometrical and technological parameters must be considered as they affect the material flow and the heat flux generated during the process. In the paper the results of an experimental campaign on AA6082-T6 aluminum alloy are presented. Lap joints have been FSSWed under different process conditions. During the process temperature fields have been measured through embedded thermocouples. The micro and macro mechanical joint properties have been measured and the effect of the joint geometry on the microstructure and local strength of the material was highlighted
Comparative Analysis of FE Modeling Techniques for Single-Lap Multi-column Composite Bolted Joints
No full textThe finite element analysis of composite bolted joints requires a trade-off between the precision of the results and the simulation time. In fact, the proper analysis of a composite bolted joint involves the understanding of different linear and nonlinear phenomena. In this regard, the composite bolted joint element (CBJE) is a simplified modeling technique that can be used within a pre-existing shell model. It is made of basic finite elements featuring elastic properties analytically evaluated from the theoretical reference model of bolted joint. These characteristics allow to bring together the exactness of results and the speed of the simulation process. Here, the suitability of the CBJE for the modeling of single-lap multi-column composite bolted joints is assessed. Outcomes of stiffness prediction and bolt-loads distribution are compared with a refined 3D model
A novel composite bolted joint element: application to a single-bolted joint
No full textBased on an analytical solution of the theoretical reference model of the composite bolted joint undergoing in-plane loads, a modeling technique for this kind of demountable connections is presented. The novel composite bolted joint element substitutes a region of the original model, comprising the bolt and the peripheral area, with a set of radially arranged beams: the cross-section properties are opportunely tailored in order to establish a stiffness equivalence between the theoretical reference model and the presented finite element through the resolution of a system of algebraic equations. The in-plane load condition is considered in this work because of its prevalence in comparison with other ones in many practical applications as the double lap shear joint. Numerical case studies are provided to validate the novel composite bolted joint element comparing FE models of circular plates, featuring a quasi-isotropic lay-up, with an internal rigid core or with the presented FE tool
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