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This paper presents a finite element solution for the static analysis of a multi-layers beam with and without piezoelectric layers. The beam is under large deformation. The virtual work principle and the Lagrangian update method (LUM) have been employed to study the static behavior of piezoelectric beams. Four-nodes element with two displacement degrees of freedom and one electrical degree of freedom has been used in this analysis. Finally, in order to prove the validity of the presented formulation and the solving process, the results are compared with the other available data.

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Progressive collapse of buildings has raised questions on adequacy of the existing regulations to prevent local and, in turn, global collapses. The present study mostly focuses on the performance of welded moment connections against progressive collapse. The performance of moment connections suggested in the FEMA 350, which are proper for seismic forces, Welded Flange Plate (WFP), Reduced Beam Seaction (RBS), Welded Unreinforced Flange- Welded Web (WUF-W) and Free Flange (FF), has been studied. The models used include non-linear behavior of materials and geometrical nonlinear behavior. The behavior of steel materials used in the structure is the true behavior of steel was stress-strain, which has been considered in the model completely. The nonlinear stress-strain behavior of steel selected for modeling the real behavior of beam and column members in the structure. The material properties of all steel components were modeled using elastic-plastic material model from ABAQUS. For connection region porous material plasticity was used. The diagram of vertical force against vertical displacement for each connection was drawn, and the state of each connection failure was investigated. Making the large scale experimental models to study the progressive collapse of structures seems too difficult. Using finite element models to study the behavior of structures are relatively appropriate option with regard to time and cost. In all of the numerical models, shell (S4) element has been used to simulate the beams, columns and connections. This is a four-node element, which contains four integration points on the element. During the calculations, full integration method with more precision was used. For analysis of the models, dynamic explicit method was used. This method is suitable to analyze the models with more members having nonlinear characteristics of materials and large deformations. In this method, the central difference integrating is used to solve the dynamic equations. In every time step, this method performs simpler than other methods in solving dynamic equations since there is no need to inverse stiffness matrix in any time stage. The used numerical method has compared using the laboratorial results, which have tested in 2010 by NIST. The analytical results showed a good agreement with laboratory models. The results of numerical analyses illustrated that RBS connection has less strength in comparison with other connections and this connection reaches maximum vertical displacement with less force. Performance of FF and WUF-W connections is similar to each other. These connections more resistant in comparison with RBS. WFP connection is more resistant as compared with the WUF-W, FF and RBS connections against the failure of the column. Failure load in WFPconnection is twice of other connection, and according to the analytical results, this connection is suitable for HLOP structures. In all connections, rotation capacity corresponding to collapse prevention against column removal scenario is about twice of the accepted criteria that FEMA 350 has suggested for seismic loads.

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Abstract- Damage of metals is a progressive physical process which finally leads to the failure of them. In this study, first, a coupled elastic- plastic- Lemaitre's ductile damage model combined with large deformations theory is developed and implemented as a subroutine into ABAQUS/EXPLICIT code. Then, by performing standard tensile and Vickers micro-hardness tests, mechanical and damage properties for St14 steel are determined. For validation of the damage model and also identified properties, cutting and fine cutting processes are simulated by the model in two cases of large and small deformation theories. Comparison of the numerical simulation results and experimental reports show that Lemaitre's ductile damage model combined with large deformation theory can accurately predict damage evolution, crack initiation, propagation, and ductile fracture in the metal forming processes with large deformations. Keywords: Lemaitre's Ductile Damage Model, Large Deformations Theory, Cutting and Fine Cutting Processes, Ductile Fracture.

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This paper presents the first and third order shear deformation plate theory and von Karman theories to solve Thermo-elastic problems of functionally graded hollow rotating disk. The material properties of the disk are assumed to be graded in the direction of the thickness by a power law distribution of volume fractions of the constituents. New set of equilibrium equations with small and large deflections are developed. Using small deflection theory an exact solution for displacement field is given. Solutions are obtained in series form in case of large deflection. Numerical results are presented for various percentages of ceramic-metal volume fractions and have been compared with those obtained using first-and third-order shear deformation plate theories. Also the results are verified with ABAQUS soft, simulink method and the known data in the literature.

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A novel geometrically nonlinear high order sandwich panel theory considering finite strains of sandwich components is presented in this paper. The equations are derived based on high order sandwich panel theory in which the Green strain and the second Piola-Kirchhoff stress tensor are used. The model uses Timoshenko beam theory assumptions for behavior of the composite face sheets. The core is modeled as a two dimensional linear elastic continuum that possessing shear and vertical normal and also in-plane rigidities. Nonlinear equations for a simply supported sandwich beam are derived using Ritz method in conjunction with minimum potential energy principle. After obtaining nonlinear results based on this enhanced model, simplification was applied to derive the linear model in which kinematic relations for face sheets and core reduced based on small displacement theory assumptions. A parametric study is done to illustrate the effect of geometrical parameters on difference between results of linear and nonlinear models. Also, to verify the analytical predictions some three point bending tests were carried out on sandwich beams with glass/epoxy face sheets and Nomex cores. In all cases good agreement is achieved between the nonlinear analytical predictions and experimental results.

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A theoretical nonlinear droplet deformation model with an accurate estimation of aerodynamic force, which is appropriate for Lagrangian droplet tracking schemes, is presented and validated. The modeling is based on keeping track only of the fundamental oscillation mode. This conventional approach has been used in many deformation-based breakup models including Taylor Analogy Breakup, Droplet Deformation and Breakup, and Nonlinear Taylor Analogy Breakup. However, these models have some shortcomings such as the use of several calibration coefficient, two-dimensional analysis, and rough approximation of aerodynamic forces in large deformations. This paper is intended to amend these defects. The formulation is based on mechanical energy equation. The pressure distribution profile around the deformed droplet is approximated using a piecewise sinusoidal function which depends on Reynolds number and droplet deformation. The final kinetic equation is numerically solved using a fourth-order Runge-Kutta method and the results are compared with those of other models, experiments, and a Volume of Fluid simulation. Numerical results show that the present model predicts slightly greater deformations in comparison with other models for the unsteady case, which is more consistent with the experimental data. Considering the steady case, the results of present model stand between that of Taylor Analogy Breakup and Nonlinear Taylor Analogy Breakup model, and provide satisfactory predictions. The stream lines obtained from simulation match those of calculated analytically suggesting the appropriateness of the assumptions used in the modeling. Overall, the present model is found to be appropriate for the estimation of droplet deformation.

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Mechanical behavior of live cells and tissues is non-linear and their deformations are large. Using a suitable mechanical model that could predicts this behavior, is an important step in the prevention and treatment of various diseases and the production of artificial tissues. In this paper, using the non-linear elasticity theory and non-linear Mooney-Rivlin model, mechanical analysis of human arteries has been studied under internal pressure and axial tension. In the first By using the experimental study was conducted of biaxial test, the elastic constants of the arteries are calculated. For modeling, the arteries are considered as long homogeneous and isotropic cylinders. Radial and circumferential stress distribution on the minimum and maximum blood pressure is calculated. Variation of artery radius due to internal pressure is calculated and compared with the reported experimental data, and a good agreement is seen. The stress distribution curves versus radius are plotted which show that the inner layers of the arteries have much greater role in stress distribution than the outer layers. The elastic constants which are calculated for different ages show that the arteries of older people become stiffer and their flexibility decrease.

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Additional dampers TADAS are a kind of passive control systems which can be used in seismic design or retrofit of structures. In this study, behavior of TADAS dampers in large deformation has been examined and some of the possible errors in its design are expressed. It is shown that how the lack of attention can result in damage to the structure and reduce the ability of energy dissipation in the damper. To investigate this issue, TADAS damper with all its details was simulated in ABAQUS finite element software. TADAS damper made up of several components, these components include the upper plate, the lower plate, triangular plates, rods rollers (pins) and connection plates. Damper modeling in ABAQUS determined that in a large deformation, the damper stiffness strongly and suddenly increases. It is examined that this sudden changes in damper characteristics is mainly due to the collision of the damper pin and the upper wall of its slot. This sharp increase could lead to adverse responses and even help to the destruction of the structures. In this paper, two suggestions are presented to prevent this situation. These suggestions include increasing the slot height and putting pins in the lowest point than slot bottom during damper installation. Assuming uniform curvature over the damper plates, a relationship has been proposed to predict the amount of the large displacement corresponding to the high stiffness of the damper. Using this relationship can get awareness of the occurrence or non-occurrence of increasing stiffness of the damper in the various classes of structures. It can also be used as a design tool for selecting the proper height of the damper slots.
Also, a frame equipped with TADAS damper is constructed and get under cyclic loading to large deformation. This frame was simulated in ABAQUS and its behavior was compared with laboratory sample. This comparison indicates that there is a good agreement between laboratory and software results. From laboratory and software models it became clear that the frame equipped with TADAS damper even in large deformation has stable and acceptable behavior, but two very important defects are observed in the frame. One of these defects is buckling of braces despite their design based on the toleration of the maximum capacity of damper. This buckling has occurred due to the rotation of beam-to-column connections. To prevent damper from degradation, it must be considered in the design process as far as the large deformations is concerned. As per the design codes, damper’s retainer system TADAS (Chevron braces) should not be damaged and/or buckled. The second defect is related to the looseness of damper’s pins and the looseness of damper’s connection bolts inside their slots. It will be shown that how this looseness causes a delay in the performance of damper and will increase the possibility that the damper plays a lesser role during earthquake. Therefore, the looseness in pins and bolts must be properly prevented. In this study, 10 bolts with 24 mm diameter were used to the connecting damper to floor-beams and Chevron braces.

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In this research, the deformation of circular metal sandwich panels with vertical tube cores under blast load has been investigated numerically and experimentally. The relationship of energy balance in different components of the structure has been considered. The core tubes are installed in a cross arrangement and vertically with the same height between the upper and lower sheets of the sandwich structure. The amount of energy absorbed by the cores is determined according to their location in the structure and the effect of their number and diameter. The grouping of the desired tests for this research has been done according to the thickness of the sheet 1.2 and 2 mm and with aluminum cores with diameters of 12 and 16 (mm). Numerical simulation has been done in the form of free explosion and by defining the pressure function using the Conwep method in Abaqus software. To validate the numerical results, experimental tests have been carried out with the construction of sandwich structure. In both methods, the maximum lateral displacement of the structure at its center and the displacement in terms of distance from the center of the structure, at cores location have been measured. Increased number of tubes in the core of the structure decreased the maximum rise in the upper layer and decreased the transverse displacement of the lower sheet. Structures with fewer cores and less sheet thickness showed more energy absorption. The average difference between the results of numerical and experimental methods was approximately 11%.