In this paper, the design, simulations, and experimental results related to new analog circuits for voltage controlled synthetic inductors (VCSI) are presented. The new circuits based on a generalized impedance converter (GIC) are proposed for adaptive resonant piezoelectric shunt damping. The VCSIs are implemented using (1) an analog multiplier and (2) an operational transconductance amplifier (OTA) as voltage-controlled resistor. The simulation and experimental results for the new proposed VCSIs are presented and a comparative analysis follows. The proposed VCSIs work in a stable manner in parallel with negative impedance converters (NIC) to enhance structural damping in resonant piezoelectric resistive-inductive shunt applications. The behavior of the synthetic inductor is identical to a real inductor only in a specific frequency range and this situation can explain the reported spreading performance in the literature for resonant piezoelectric shunt damping. The simulation results are validated by a group of experimental investigations that confirm the improved stability and linearity of the new circuits proposed as VCSIs. Experimental results show that the VCSI based on an analog multiplier have an enhanced linearity in comparison with the OTA version in a limited voltage control range.

Functionally graded materials are increasingly used in the practice of engineering design, as is the case with thick-walled tubes. The use of these constructive elements requires a calculation, which should be as accurate, as accessible and as fast as possible. The present work responds to these requirements. For the calculation of tubes with thick walls made of functionally graded materials, two new ways were used, based on the concepts of multilayer (material) wall and equivalent material. The multi-layered wall concept considers the tube wall made of several layers, as in the case of the well-known multilayer plates, and the equivalent material concept considers the thick-walled tube made of homogeneous and isotropic material, but with fictitious properties, equivalent in behavior to the functionally graded material. The influence of Poisson's ratio is illustrated by some comparative results. The development of the calculus, the validation of the models and the analysis of the results are based on the numerical calculus using the finite element method. The models used, the transverse plane model, the axial-symmetric plane model and the 3D longitudinal model, are made in several variants regarding the fineness of the mesh. The paper also analyzes the influence of the Poisson ratio variation, compared to adopting a constant value. The results of the study, the models and concepts used are useful to specialists and designers of structures of this type, they have a high degree of generality and present openings for the use of other calculation methods.

In the calculus of functionally graded plates, the concept of multilayer plate is often used. For the use of this concept in this calculus, the continuous variation of the respective properties is replaced with a step variation. The first problem that arises in front of the user is related to the number of layers, which must be a finite and reasonably large number, to be accessible to the current calculus and to ensure the necessary accuracy of the results (under 5%). Another problem, generally poorly substantiated, is the one related to the assumption of a constant value of the Poisson’s ratio (usually 0.30 for the considered materials) over the entire plate thickness. The paper also contains a quantitative study of the influence of the Poisson ratio (4,…,10%), whose variation can be neglected, but only in certain circumstances. The presentation and substantiation of how to use the multilayer plate concept through models, methods and methodologies, along with the substantiation of the choice of the number of layers and the influence of the Poisson’s ratio, represent the main evidence of the originality of this work. The proposed numerical models are based on the use of common 3D finite elements. The software Ansys is used, which offers a multilayer finite element, which is taken into account in the comparative analysis of the results. The validation of the results is carried out by comparison with the analytical solution. The objective and purpose of this paper, that of completing the palette of achievements regarding the calculus of functionally graded plates, without modification of the stiffness matrices of the finite elements and using existing software products, are fulfilled.

This paper brings in front of the interested researchers using one of the most known and used meshfree method, Element-Free Galerkin (EFG) method, in modelling of a technological process. It is about the deep drawing process of thin plates made of steel or aluminium. The paper gives information both for EFG method and for deep drawing process. The modelling as well the results are presented in a comparative way towards the using of Finite Element Method (FEM). The numerical analysis is based on the Ansys/Ls-Dyna program, in which EFG method is implemented. This numerical method is less known in our country and much less used, in spite of some advantages comparatively with the FEM. Of course, the EFG method is still under developing, but it can be successfully used in many problems. This paper is a proof in this sense and an urge to use the EFG method.

This paper presents, in a synthetically way, the fundamentals of the element-free Galerkin (EFG) method - a meshfree method - under development but with many capabilities for solving complex problems in mechanical engineering, like impact problems etc. For interpolation, the EFG method uses moving least-squares (MLS) interpolants in curve and surface fitting. Unlike other interpolants, the MLS interpolants do not pass through the data because the Dirac function properties are not available. This aspect could be a disadvantage of the EFG method but next to it, there are many advantages. Upon these issues a discussion exists in this paper. Finally, some applications of the EFG method are presented referring to static and dynamic analysis of structures. The examples and conclusions can be useful for knowing and using of the EFG method

This paper presents some of our results regarding calculus of the functionally graded plates (FGPs). Such plates are made of Functionally Graded Materials (FGMs), which represent a new material class belonging to the composite materials. Our paper presents some material laws in a comparative way. But the main purpose of this paper is to provide calculus concepts and calculus methodologies, based on the means available in scientific research of mechanical engineering field, for the calculation of plates made of FGMs. Thus, the authors use the concepts of multilayer plate and equivalent plate, using both analytical and numerical calculus. The numerical method used are the Finite Element Method (FEM).The calculation aims both to determine the displacements and the stresses of the plates under statical loads, as well as to determine the free vibration frequencies. The research methodology is based on combining analytical calculation, where and when possible, with numerical simulation. The validation of our results is done by comparison with the analytical solution and the comparative analysis of the methods.