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Abstract- This research develops a Lamb wave technique to determine the dispersion curves of a two layered bonded component: an aluminum sheet attached to a composite layer by means of a cohesive. A commercial finite element code (ABAQUS Explicit) is used to determine the dispersion curves of the Aluminum-cohesive-composite multilayer component. The finite element model includes three plain strain layers that the middle one is cohesive. Then a lamb wave is propagated in the model and some output signals are received. The dispersion curves are obtained by using 2D Fourier transformation of finite element model output signals. In addition, to produce various modes, experiments are carried out on a composite-aluminum assembly using two 2 MHz variable angle transducers. Comparison of modes obtained from finite element method and experiments shows that group velocities are almost identical. Hence, good agreement between finite element method results and experimental results indicates that finite element is reasonably accurate for determination of dispersion curves.

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Mechanical properties of living cells play an important role in helping to understand cell physiology and pathology. Evaluation of mechanical properties of cells may potentially lead to new mechanical diagnostic methods for some of these diseases. In this study, viscoelastic properties of the outer layer (cytoplasm and membrane) were extracted using standard linear solid model. Finite element modeling of the two cell layers is performed and the model is validated by experimental data. In the two-layer model, the effect of the radius of the nucleus and the location of the nucleus in the cell are investigated on the cell properties. By reducing the cytoplasmic radius ratio up to 43%, the whole cell properties follow the cytoplasmic properties and the effect of the nucleus can be neglected. The 50-second displacement change at a radial ratio of 0.53 increased to 4.5% compared to radial ratio of 1.58.  At a radial ratio of 0.43, a change in cell behavior was observed compared to the previous one, with a displacement change equals to 6.8% compared to radial ratio of 1.85 and a displacement reduction of 9.5% at a radial ratio of 0.53. The results demonstrate that the location of the nucleus and the ratio of the radius of the cytoplasm to the radius of the nucleus can effectively influence the viscoelastic properties and mechanical behavior of the cell.

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In this paper the behavior of framee, the process of plastic hinge formation and energy absorption of frames with two spans and one floor with three types of slab including bubble deck slab, hollow core slab and reinforced slab under three earthquake accelerations have been analyzed and compared. The results show that bubble deck slab and hollow core slab as rigid as normal reinforced slab, although bubble deck slab has higher strength and stiffness compared to other slabs. Partnering slab in analysis make period of slab reduce more over bubble deck slab and hollow core to the comparison of reinforced slab, have more effect on period reduction. Ultimate displacement of frame with reinforced slab reach to failure mechanism is more than two mentioned case, however frame with bubble deck slab reach to failure mechanism under stronger earthquake acceleration and smaller displacement than reinforced slab. Comparison base shear of three discussed case shows that maximum base shear is in bubble deck slab and minimum base shear is in normal reinforced slab. Formation of plastic hinge in frame with bubble deck slab is similar with that in frame with hollow core slab with the difference that plastic hinge in former occurs later at the top end of the middle column and two ends of middle beams. In fact, formation of plastic hinges in this frame requires higher acceleration because of the higher amount of concrete and stiffness. In all samples, plastic hinge first occur in the frame and then yielding lines occur in the tensile region of the slabs. The failure mechanism of slab and steel frame occur at the same time in frame with hollow core slab and reinforced slab; however, this is not the case in the frame with bubble deck slab and even though with occurring of yielding lines, the slab does not fail. The stress distribution due to gravity loads is symmetric across all the slabs; however, the increase rate of stress is different. This difference is particularly notable in seismic behavior of slabs in a way that the formation of plastic hinge and yielding lines in hollow core slab, because of the holes, is totally different with that of in reinforced slab. In comparison with other slabs and due to the formation of plastic hinge, reinforced slab absorb lower energy. Columns, beams and connections play different role in energy dissipation. In all frame, the contribution of connections to dissipate energy is minor and this is because yielding does not occur in connections. Contrary to the frame with reinforced slabs, because of yielding in several places of columns, columns dissipate energy more than beams in the frames with hollow core slabs. It was concluded that hollow core slab and bubble deck slab have maximum and minimum contributions to the energy dissipation, respectively.

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Hydraulic engine mounts isolate the structure of the vehicle from powertrain vibrations and also prevent excess motions of the powertrain due to shock excitations. In this paper, dynamic stiffness of a hydraulic engine mount in low frequency range (shock frequency range) is predicted using modal test data and three-dimensional finite element model through an iterative model updating procedure. The implemented model encompasses elastomeric material’s nonlinearity, fluid-structure-interaction and internal resonances of mount. Mesh morphing technique is used to model the fluid-structure-interaction. The results showed that the introduced procedure can successfully predict the shock isolation behaviour of the hydraulic engine mount.

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Analytical and finite element models predict the elastic modulus of CNT-polymer nanocomposites greater than experimental results. This paper presents a theoretical full continuum model to define the upper and lower thresholds with small variations for elastic modulus in polymer nanocomposites, which the experimental results always place between these thresholds. For this purpose, the governing elasticity equations in polar coordinates have been solved for nanocomposite representative volume element (RVE) with shear-lag model by assuming perfect bond condition between CNT and matrix. In addition, the nanocomposite elastic modulus in perfect bond and debonding conditions between nanotube and matrix is calculated using finite element method in ANSYS software which confirms the accuracy of theoretical results. Also the obtained analytical and FEM results are compared with available experimental results, which indicates that the value of experimental results is always between the upper and lower thresholds of analytical and FEM results.finally by surveying the axial and von-mises stress in the matrix region, the new way for defining the elastic modulus of new nanocomposites with analytical method is proposed here which reduce the cost of experimental research.

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Cold tube rolling process is one of the current seamless tube manufacturing methods. One of the serious problems of this process is micro-cracks in final product. Numerical modeling is a method to predict and reduce these micro-cracks. In the current paper damage in cold three-roller pilger process is simulated by finite element method. In these simulations to predict damage evolution three different damage models, including Lemaitre model, modified Lemaitre model and cumulative damage model are used. In conjunction with these models isotropic and combined hardening rules is also considered. Forming benchmarks are simulated to validate provided codes for the mentioned models. Then the process is simulated and good agreement is observed between current results and previous numerical and experimental results. The results show that three models correctly predict damage distribution but predicted damage by Lemaitre model is more than modified Lemaitre model due to ignoring crack closure in compressive loads. It is also concluded that using combined hardening rule predict damage growth less than using isotropic hardening. all of the models suggest that crack initiation take place in the outer surface of the tube .

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Mechanical behavior of articular cartilage is affected by many factors. Inhomogeneous distribution of proteoglycans and collagen fibers through the thickness causes some depth-wise behavior. Mechanical properties directly affect stress and deformation of the tissue. In previous studies complexities and variation in mechanical properties were ignored. The aim of the present study is to create a model close to real anatomy of articular cartilage in knee joint and to simulate its behavior under dynamic gate in the stance phase. A 3D finite element (FE) model was created. It was constructed considering femur and tibial cartilages as well as medial and lateral meniscus. In the FE model, a nonlinear isotropic viscoelastic material model used for cartilages and a linear anisotropic elastic one was chosen for meniscuses. As well, cartilages assumed saturated . Numerical simulations on the model showed that peak of maximum principal stress occurred in superficial layer. It was decreased through thickness. These expressed why osteoarthritis fall out in the exterior layers such superficial . The present study showed that hydraulic permeability variation in cartilage as a strain-dependent variable was negligible in dynamic loading. Also, results had a good agreement with experimental ones

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The detection of changes in the dynamic behavior of structures is an important issue in structural safety assessment. Deployment and servicing of marine and coastal structures such as piers in the marine environment with constantly changing, requires understanding the dynamic behavior of these structures to prevent possible damage. Among the factors of uncertainty in understanding the dynamic performance of piers is uncertainties related to semi-rigid connection of deck to piles. According to this fact that the main mass of the structure is on deck, the connection of deck to piles is very important. In this study, experimental and numerical model of beach piers were studied. A Test on experimental modal analysis was performed to determine the response of structures. A numerical model of the structure prepared and theory of modal analysis was performed on it. Then, based on the finite element model updating of structure approach, identify and determine the percentages of semi-rigid connections. Results show this fact the connection isn’t fully rigid. According to the present method can be compared to determine the percentage of semi-rigid connections and prepare the finite element model with more adaptable to the experimental model. Updated results with this method were very close to the real model.

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Mathematical modeling of tumor growth as modeling of other biological tissues is important since these models enable us to predict and evaluate the parameters that could not be measured easily. The accuracy of a derived model depends upon considering more involved factors and mechanisms and will lead us toward a realistic modelling.
In this study, a finite element model of avascular tumor growth is represented. This model concentrates on the constitutive behavior of tissues and the resulting stresses. The tumor and its host are assumed to behave as a hyperelastic material. The tumor model is supplied with a growth term which is a function of nutrient concentration, solid content of the tumor and rate of cell proliferation and death. The evolved stresses during growth and interactions between tumor and the surrounding host could be evaluated using the presented model. The results show that the exerted stresses on tumor increase as time passes which lead to reduction of tumor growth rate until it gradually reaches an asymptotic radius. The effects of variation of the bulk modulus which is a determinant of compressibility are investigated. Since biological tissues consist mainly of water so we should impose the condition of incompressibility. It is found that the increase of bulk modulus which leads to more incompressibility causes stress elevation.

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Vehicle vibration and noise characteristics play a major role in ride comfort. Noise of tire in contact with the road is one of the main sources of noise in passenger cars, caused by the rolling of tire on uneven surfaces. Excitation imports through tread structure to fluid cavity and noise and vibrations transmission to the rims is of particular importance. In this paper, vibration analysis of coupled acoustic model of tire, rim and fluid acoustic cavity is performed. For this purpose, a coupled numerical finite element model is used. First, tire modeling has been addressed, taking into account the tread and two side walls and steel wheel rim. Then modal analysis has been performed to identify the structural and acoustic resonance frequencies and mode shapes. Then, using the harmonic environment coupled with static and modal analyses, acoustically coupled models of tire, rim and cavity are used to calculate the acoustic pressure of the fluid cavity, and sound pressure level, and the harmonic frequency response of the wheel hub system including the forces of wheel hub is discussed. According to the presented model, the parameters affecting tire noise levels are discussed.

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Abstract:
Composite construction in steel and concrete offers significant advantages for use as the primary lateral resistance systems in building structures subjected to seismic loading. While composite construction has been common for over half a century through the use of composite beam and joist floor systems, over the past decade a substantial amount of research has been conducted worldwide on a wide range of composite lateral resistance systems. These systems include unbraced moment frames consisting of steel girders with concrete-filled steel tube (CFT) or steel reinforced concrete (i.e., encased steel sections, or SRC) beam-columns; braced frames having concrete-filled steel tube columns; and a variety of composite and hybrid wall systems.
Structural walls are widely used in building structures as the major structural members to provide substantial lateral strength, stiffness, and the inelastic deformation capacity needed to withstand earthquake ground motions. In recent years, steel reinforced concrete (SRC) walls have gained popularity for use in high-rise buildings in regions of high seismicity. SRC walls have additional structural steel embedded in the boundary elements of the reinforced concrete (RC) walls. Walls with additional shapes referred as composite steel-concrete shear walls, contain one or more encased steel shapes, usually located at the ends of the wall.
Composite shear walls with steel boundary element are known as the structural members able to withstand high in-plane lateral forces at low displacement levels. Reinforced concrete shear walls with steel boundary element being performed in Iran are joined to the foundation, in boundary element section, usually through bolts and base plates. Most reliable codes of the world have nothing to say about the behavior of this type of shear walls, and no experimental studies or analyses have been conducted on the behavior of this type of shear walls. In the past decade, great effort has been devoted to the study of seismic behavior of SRC walls, for Design provisions for SRC walls have also been included in some leading design codes and specifications, for example, AISC 341-10 , Eurocode 8, and JGJ 3-2010
Exposed baseplates together with anchor bolts are the customary method of connection of steel structures to the concrete footings . In this paper, the influence of cross section of base plate’s joint bolts to the foundation and the wall’s longitudinal bars embedding within the area of boundary element in the foundation, on the behavior of this type of shear walls have been investigated. The finite element software is first calibrated and the accuracy of its results is validated through modeling the experimental samples. In this research, the concrete’s nonlinear finite element analysis method and concrete damage plasticity model have been used for the concrete’s behavior modeling. The results show that increasing in the level of bolt’s cross section and also the embedding of longitudinal bars of boundary element in the foundation cause an improvement of the capacity of these walls. However, these walls’ resistance against the normal axial loads is considered to be less than reinforced concrete shear wall.

Keywords: Reinforced concrete shear wall, Steel boundary element, Concrete damage plasticity model, Finite element model.

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In recent years, development of polymer electrolyte membrane fuel cells (PEMFCs) has been considered to generate electricity and heat. Among main components of PEMFCs, bipolar plates (BPPs) have significant influence on cost and performance of the system. Metallic BPPs, formed using thin sheets, have been developed as alternative to conventional graphite plates because of advantages such as suitable cost, mechanical strength and power density. Flexibility of the sheets and spring back during forming process make dimensional errors inevitable and lead to inappropriate contact pressure distribution between BPPs and gas diffusion layer (GDL), resulting in decrease of fuel cell performance. Excessive accuracy in BPP production leads to increase the final cost and decrease the general usability of the technology. Therefore, to reduce unnecessary costs, managing design process and improving efficiency, analysis of BPP dimensional errors is done using finite element method and Monte Carlo simulation (MCS). First, contact model of the metallic BPP and GDL is developed and heights of each channel and each rib of BPP are fully parameterized due to stochastic variations of dimensional errors with normal distribution. Then, contact pressure distributions of GDL (Pave, Pstd) for different dimensional errors are obtained by MCSs. Increasing dimensional tolerance from 0.015 mm to 0.075 mm, average contact pressure (Pave) has decreased by 11% and standard deviation of contact pressure (Pstd) has increased up to 90%. Namely desirable distribution of GDL pressure is reduced by increasing the dimensional error and suitable dimensional tolerances for BPPs can be determined according to engineering requirements.

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Additive Manufacturing (AM) or 3D printing is a method to build parts by adding layer-upon-layer of material. The selective laser sintering (SLS) method is one of the most important methods of additive manufacturing processes. The low time and the variety of materials used to build the parts are major advantages of SLS method. The high quality of the product is one of the main goals in the additive manufacturing processes. The part warping is one of the factors that reduce the quality of the products which are built by the SLS process. The hatching patterns and scan algorithms in the SLS process are important factors that affect the product quality. In this paper, the effective parameters of the SLS processes such as the scan vector length and the number of offsets or contours, the laser power, the laser speed, and the hitching spacing are optimally determined to minimize the part warping of the product based on the finite element simulations and Taguchi method. For this reason, SLS process has been modeled on the SLS process. Then, to illustrate and validate the accuracy and efficiency of the proposed method, and the computational results are compared to the obtained results from the experimental tests Using SLS containing CO2 laser. Finally, using the Taguchi design of Experiments, the process parameters have been changed at different levels and optimal parameters have been obtained.

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In this paper, finite element modeling of friction welding of two ASTM A106-B and AISI 4140 dissimilar pipes is investigated. The effect of the friction welding parameters including rotation speed, friction pressure, friction time, forging pressure and forging time on the axial shortening are investigated using a fractional factorial design method. Because of the extreme material deformation, an innovative remeshing technique was scripted in Abaqus CAE to prevent the creation of distorted elements. 27 models were solved and 3 validation experimental tests were carried out. Results showed that increasing the all parameters cause larger axial shortening. Friction pressure with 33.9% had the most effect on the axial shortening. Moreover, an increase in forging pressure and forging time has a limited effect on the axial shortening. After about 2 seconds from the beginning of the welding, the temperature of the interface becomes steady at about 1250°C. The validation tests revealed that the simulation error was about 5.6% which shows a good agreement between the finite element results and the experimental data.

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Piezoelectric materials, in different shapes such as rectangular plate, annular plate, circular plate and cylindrical shell, have increasing application in industries in order to create smart structures. In this article, experimental and numerical analysis of free vibration of a two-layered cylindrical panel with metal and piezoelectric layer in different boundary condition is carried out. First, a single PZT-4 layer is polarized in radial direction. Using the Piezoelectric layer and an Aluminum layer, a two-layered smart panel is prepared. Then, the first natural frequency of the hybrid panel with free boundary condition is measured experimentally in three different ways. The hybrid panel is simulated in a finite element software (Abaqus). Results show good agreement between different experimental methods, as well as, between finite element model and experimental results. The accuracy, limitations and merits of different experimental methods are discussed completely. The results show that the natural frequency can be achieved accurately by excitation of actuator layer. Finally, the influence of different boundary conditions as well as geometrical parameter such as radios, length and thickness of smart cylindrical panel are investigated using the finite element software.

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The precise finite element model is an efficient tool for vibrational analysis. It should be mentioned that, in structural dynamic analysis finite element models of system should be able to accurately predict system characteristics such as natural frequencies. Contrary to static analysis, in structural dynamic analysis, it is not possible to overestimate system characteristics or apply safety factor for predicted characteristics; that means that the exact values of system characteristics such as natural frequencies, should be derived in structural dynamic. According to this, constructing a reliable model in the structure dynamic always has great degree of importance in vibrational analysis. In this study, it has been tried to extract a reliable finite element model for a row of a sample turbine of RollsRoyce brand using empirical results. So, the material properties of the disk and the connection between the disk and the blade are corrected and updated using experimental modal analysis results. Also, it has been tried to propose new method to model and update the disk and blade joint. Finally, reliable finite element model could be used for more analysis such as derivation of Campbell diagrams of system.

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Beam–column connections in reinforced concrete (RC) structures play an important role when the frame is subjected to seismic loading. The overall stability of the structure and the formation of the optimal energy absorption mechanism in the beam plastic hinge zone depends on the role of the beam-column joints. The non-seismic detailing in the joint panel area can cause a partial or total collapse of the structure. Beam-column connections with non-seismic detailing in buildings with moment resisting lateral load bearing systems, are the major cause of post-earthquake damage. The optimal shape and energy absorption of the moment frame structure is dependent on the design and perfect execution of the beam-column connections. In the beam-column connections, the lack of positive reinforcement of the beam in the joint area and non-extension of the column stirrup in the joint area are common defects of the joints in accordance with new regulations. Researchers have provided a lot of experimental studies on beam–column connections, while experimental studies are usually costly and time consuming, and can be restricted by the test facilities and space. The behaviour of the RC beam–column joint is very complex and several parameters such as axial load ratio, reinforcement detailing, concrete strength have significant influences on its seismic performance, it is impractical to fully investigate all parameters through a limited number of experimental tests. Finite element modelling using ABAQUS software platform can provide an opportunity to study the various parameters governing the monotonic and cyclic behaviour of the beam–column joints. In this study, by examining several parameters in the finite element model of the RC Beam–column connections in ABAQUS software, such as specifications of strain-hardening for steel, bushinger effects, concrete damaged plasticity (CDP) in tensile and compression, concrete confinement effects, presence of lateral beam, and also bond-slip of reinforcing bars was investigated and leads to provides recommendations for finite element modelling of the RC frames. For this purpose, the behaviours of the seismically and the non-seismically detailed beam–column joints under monotonic and cyclic lateral loading were evaluated in different conditions of the presence of lateral beam. The finite element models with seismic and non-seismic detail were considered and validate with laboratory tests by considering sliding effect of longitudinal beam reinforcement using modified steel stress-strain curve. Then, the effect of different lateral beam conditions around the joint was considered. The results showed well that the finite element model is more consistent with the experimental results when considering the slip effects of the longitudinal beam reinforcement. Also comparing the results of the models with the different lateral beam conditions showed that confining the non-seismic joints can increase the joint strength against lateral loads. The general behaviour mode for the seismically detailed specimen was flexural yielding in the beam at the column face whereas for the non-seismically detailed specimens joint shear failure occurred generally before the beam section reached its ultimate flexural strength. The finite element model of beam-column joint specimens was calibrated by test results and good agreement was found between the experimental and numerical hysteretic behaviour. The model was able to capture the modes of failure, peak load and initial stiffness of the tested specimens.

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