Resumo em Inglês:

Abstract This paper describes an isogeometric analysis of the boundary element method, called IGABEM, applied to anisotropic 2D plane elastic problems. The Lekhnitskii's anisotropic fundamental solution is used and the singular integral terms is regularized. For the weak singularity kernel, the Telles transform is used. On the other hand, in the strong singularity term, the Singularity Subtraction Technique - SST is used. The shape functions used are the Non-Uniform Rational B-Spline - NURBS. Thus, the same mathematical representation of Computer Aided Design - CAD is used in the implemented computational code. This avoids the generation of meshes and provides an exact representation of most complex geometries. As a reflection of this isoparametric concept, errors from geometric interpolation are excluded, improving numerical results. Furthermore, to increase the numerical efficiency of the code, the NURBS are decomposed into Bézier curves. To evaluate the accuracy of the formulation, complex problems using high-order isogeometric boundary elements are analyzed. Their results are compared to analytical solutions showing good agreement.

Resumo em Inglês:

Abstract Friction is an important source of dissipation in dynamical systems. Properly considering it in the numerical model is fundamental to obtain stable and representative responses in structures and mechanisms. This is especially significant for the well-known Coulomb model due to discontinuity in force when stick-slip transition occurs. In this work an improved friction force model is proposed to smooth the force transition at null velocity, with an additional parameter obtained from the own system state. The improved model is employed in sliding connections of plane frames finite elements. A total Lagrangian Finite Element Method (FEM) formulation based on a positional description of the motion is employed. Using a variational principle, frictional dissipation is added to the total mechanical energy to develop the equations of motion. The resulting nonlinear equations are solved by the Newton-Raphson method accounting for the friction force update in the iterative process. Examples are presented to show the formulation effectiveness and possibilities in simulating dynamical systems that present the stick-slip effect.

Resumo em Inglês:

Abstract The potential risk of cable-stayed arch-truss damage is large and the damage is undetectable. The damage identification methods based on frequency domain have limitations such as limited data and complex theoretical methods. A damage identification method based on multi-node time-domain data fusion was proposed to overcome these limitations. The time-domain data library was established by finite element analysis, and the time-domain data was preprocessed and augmented. Two CNNs models were established to identify the damage location and damage degree of cable-stayed arch-truss. The proposed method was verified by the analysis of a practical cable-stayed arch-truss scale model, and the recognition effect of the method on noisy data and noise-free data was studied respectively. The results showed that the CNN can effectively identify the damage degree and damage location of cable-stayed arch-truss structure with good robustness. CNN with Gaussian noise can accurately predict the damage degree of cable-stayed arch-truss. The prediction error of most elements is within 15%, which can meet the actual needs of engineering.

Resumo em Inglês:

Abstract In this article, the efficiency of the tuned liquid column damper (TLCD) in reducing structural vibration is analyzed. The analysis by numerical methods and by analytical methods is adopted in the search for the ideal parameters for the liquid column. The equivalent linear model is considered for the U-shaped liquid column equation of motion with damping resulting from an orifice. Thus, variation of TLCD parameters for different loads is investigated. Initially, for the numerical study in conjunction with the analytical formulation, a sinusoidal forcing is adopted. Subsequently, the action of an earthquake through the recorded ground accelerations is considered in the case study. Optimal TLCD parameters are presented via response map for reducing the structure's maximum permanent response to harmonic excitation and for reducing the structure's rms response to seismic excitation with wide frequency and various amplitude. The variation of the TLCD parameters presented by the response map is directly related to the force acting on the structure. However, it is verified that regardless of the acting force, there is an ideal frequency range to tune the TLCD where the greatest reductions in the primary system response are found. It appears that reducing the aspect ratio of the liquid column makes this range narrower, making the damper more sensitive to parameter variations, as well as its performance. It is also observed that the increase in the attenuator mass ratio combined with the correct tuning and damping ratios present greater reductions in structural vibration. Also, the frequency ratio is reduced with the increase of the mass ratio, while the damping rate of the liquid column increases. From the ideal liquid column parameters determined by the parametric analysis, structural response reductions of approximately 60% were achieved.

Resumo em Inglês:

Abstract This study highlights the analysis of corrosion shape effects under thermo-mechanical loading on the development of damage in corroded and cracked aluminum plates. This study is divided into two parts, the numerical analytical part, was performed to compare the effect of the corrosion geometry on the repair and adhesive damage; We analyzed the effects of damaged areas on the level of corrosion in the adhesive layer of three composite materials (boron/epoxy, glass/epoxy, and graphite/epoxy), and studied the change of the stress intensity factor for circle or square-shaped corrosion. The second part related to an experimental study of the corrosion shape on the ultimate strength of the damaged plate repaired by the boron/epoxy composite material. The results obtained, indicated that the effect of the circular shape of corrosion is small compared to the square shape. The type of composite material (boron / epoxy) has proven its optimal effect on repair.

Resumo em Inglês:

Abstract Compared to other orthodontic acceleration methods such as drug, electric current, and laser, vibratory loading is less invasive and easier to use. But the optimal duration for vibratory load application has not been determined, nor can the alveolar bone parameters be predicted after vibratory load application. Therefore, this work examined the mechanism of vibration-accelerated alveolar bone reconstruction and established a numerical model for simulating alveolar bone damage caused by vibration loads. That is, the role of vibration load in orthodontic acceleration was analyzed, and a finite element model was established to validate the vibra-tion-accelerated orthodontic mechanism with a simulated numerical model of alveolar bone damage. The optimal duration of application was obtained for the right anterior incisor under vibratory loading of 5 N orthodontic force, 50 Hz in the gingival orientation and 0.2 cm amplitude for 120 to 140 minutes. This work is of guidance and reference significance in promoting the development of orthodontic treatment and shortening the orthodontic treatment cycle.