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Steel plates are widely used in various industries, especially in civil engineering. Low cost in implementation and reduction of seismic mass are the advantage of steel shear wall system compared to other structural systems. The goal of a good design is that along with following the existing guidelines and achieving the desired seismic resistance of the structure, the structure is affordable in terms of weight and cost. Considering that according to the design, it is not possible to achieve the optimal use of the structure's capacity by force control method, the theory of uniform deformations was proposed with the assumption of a constant performance level. The subject of design based on performance increase the safety of the structure against earthquake force and design with optimal seismic performance during the useful life of the structure in seismic areas. Also, compared to the design method based on force control, it can lead to a lighter and economical design.
One of the significant ways to reduce the weight and stiffness of shear walls and boundary elements connected to them is to limit the connection of filler plates to boundary elements. In this method, limiting the length of the connection reduces the force on the beams and columns, and as a result, smaller sections can be used.
In this research, in order to achieve the optimal performance level, two concrete frames with steel shear wall resistant system are subjected to nonlinear analysis. Then, the initial evaluation of the behavior and the correctness of the used method are checked. After that, the effective factors in achieving uniform stress in the height of the structure will be investigated. For this purpose, by using the effect of the thickness parameter and the appropriate pattern of connection of the shear steel plate to the surrounding elements, the way of changing the performance and behavior of the structure will be investigated. For this purpose, 3- and 4-story concrete frames with steel shear wall systems were modeled using ABAQUS^TM finite element software. The steel used in the steel shear wall system is ST37. First, the connection of steel shear plates to floor beams was considered and then the influence of the partial connection pattern on the seismic performance of the steel shear wall system was investigated. The modeled frames were subjected to dynamic analysis, linear and nonlinear buckling analysis, and cyclic analysis. Based on the obtained results, the property of energy dissipation in the frame with a steel shear wall system with partial connection has increased significantly. Changing the partial connection pattern led to changing the maximum in-plan relative displacement. Also, the surface of the stress distribution shows that in the partial connection, the stress concentration mainly occurred in the place of the steel shear plate connections. In addition, according to the results of cyclic analysis, considering the partial connection of the steel shear wall has led to a decrease in the average energy absorbed in the structure and an increase in its ductility. Also, changing the connection pattern has affected the average amount of absorbed energy in different loading cycles.

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In this paper, we report results of stress analysis and fatigue life assessment of a number of spot weld joints. Models are presented for corrugated plates, jointed to an L-shape plate using 7 and 14 spot welds, which are subject to four different types of alternating loading conditions. The analyses are based on the solutions obtained from the ANSYS7 finite element package, using solid elements. In this study, strains and stresses in the weld nugget are evaluated. However, the primary focus is on strain-based fatigue life assessment which considers the 3D state of stress around the weld nugget and the nonlinear effects of the materical and the geometry.

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In this paper, we report results of stress analysis and fatigue life assessment of a number of spot weld joints. Models are presented for corrugated plates, jointed to an L-shape plate using 7 and 14 spot welds, which are subject to four different types of alternating loading conditions. The analyses are based on the solutions obtained from the ANSYS7 finite element package, using solid elements. In this study, strains and stresses in the weld nugget are evaluated. However, the primary focus is on strain-based fatigue life assessment which considers the 3D state of stress around the weld nugget and the nonlinear effects of the materical and the geometry.

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Aluminum alloys are desirable in industry due to their excellent high-strength to weight ratio, corrosion resistance, and weldability. However, at room temperature, the formability and the surface quality of the final product of these alloys are low. So in recent decade, new process, hot metal gas forming, has been introduced. This paper investigated new method of hot aluminum alloys forming using gas. Experimental test for bulge forming was designed and made. In addition to experimental test, finite element analysis of process was done. Results showed that hot metal gas forming provides highest forming temperature for aluminum alloy blank and with increasing blank temperature up to optimum temperature of hot forming, there is reduced pressure forming and significant improvement of formability. Results of experimental test and finite element analysis including determination of optimum temperature for forming of special aluminum alloy, maximum formability in this process, required forming pressure, minimum thickness, thickness and temperature distribution were conformed.

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Metal foams are a new class of materials with interesting structural properties; however no comprehensive understanding of their inelastic behavior has been established yet. Since the experimental studies of these materials have their own limitations, there is a growing research interest towards the mesostructural modeling of these materials. Accordingly many researchers have been trying to generate realistic and representative numerical models of the foams and prepare computational labs in which different aspects of foams mechanical behavior can be thoroughly investigated. The following three kinds of mesostructures have been commonly employed: (1) models based on a unit cell or a building block, (2) random Voronoi diagrams, and (3) CAD structures provided by the X-ray micro-computed tomography. In the current study, the physically representative circle set Voronoi diagrams are employed to define the geometry of 2D metallic foams. It is assumed that the minimum and maximum radii of the circular generators are 0.5 and 1.5 mm, respectively. The first sample is generated using linear distribution of cell size while, compared to the first sample, the second and third specimens have less and more small cells. An extra specimen (the forth sample) is also created with the same structure of the first one unless its edges are straight. In the next step, the FE models of the specimens are created using second order Timoshenko beam elements. Finally, the effects of microstructural features (e.g. strut curvature and cell size distribution) on the initial yield surface, elastic properties, and failure modes of the foams are numerically investigated under various biaxial loading conditions. Displacement-controlled loading is used. A newly energy-based approach developed for the identification of initial yield points has been incorporated. The results show that: (a) the size of the initial yield surface is significantly influenced by the curvature of the cell struts, (b) in the principal stresses space, the initial yield surface is bigger in the tension-tension region, (c) for a constant relative density, the presence of more big cells in a sample increases the size of the yield envelope, and (d) the macroscopic yield properties of the specimens can be interpreted according the microscopic failure mechanisms of the plastic yielding, elasto-plastic buckling, and plastic hinging of the struts. Furthermore, it is found that the previously proposed energy-based method for the identification of yield initiation under multiaxial loading conditions has serious shortcomings and needs revision.

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In this paper, simulation and analysis of thin steel cylindrical shells of various lengths and diameters and thickness with triangular cutouts have been studied. In this research buckling and post-buckling analyses were carried out using the finite element method by ABAQUS software. Moreover, the effect of cutout position and the length-to-diameter (L/D) and diameter-to-thickness (D/t) ratios on the buckling and post-buckling behavior of cylindrical shells have been investigated. In this work the cylindrical shells used for this study were made of mild steel and their mechanical properties were determined using servo hydraulic machine. Then buckling tests were performed using a servo hydraulic machine. In order to numerical analyze the buckling subject to axial load similar to what was done in the experiments; a displacement was applied to the center of the upper of the specimens. The results of experimental tests were compared to the results of the finite element method. A very good correlation was observed between numerical simulation and experimental result.

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Squat shear walls are common in low-rise buildings, their seismic rehabilitation, lower stories of high-rise buildings, and nuclear power plants. Wall segments formed by openings also have the same behavior as squat shear walls. Usually walls with aspect ratio less than 1.5 are known as low-rise or squat shear walls. Shear stresses have significant effect in lateral strength and ductility of such walls. Concrete structures with shear dominant behavior are more complex for Analyzing and their seismic behavior may be poor. Also squat shear walls have various failure modes under lateral loading. In recent years designers have intended to performance based assessment and design of structures. Thus, reliable instruments for nonlinear analysis of squat shear walls are required. Previous efforts to nonlinear modeling of squat shear walls usually were performed by FE codes such as ABAQUS, ADIANA and VecTor2. These codes are not practical for performance based assessment and design of structures. Performance based assessment software programs such as SAP 2000 and PERFORM 3D are more desired to modeling complex structures. Accordingly, there is a need for reliable modeling techniques for nonlinear modeling of squat shear walls using performance based assessment software programs. The purpose of this paper is to finding suitable information for fast and reliable modeling of squat concrete shear walls with widely used building structural software programs. Therefore, by selecting and modeling five test specimens from previous experimental studies using two widely use commercial codes, SAP 2000 and PERFORM 3D, Key parameters for modeling such walls are found and calibrated to bring analytical results near the test results. These software programs employ fiber (layered) model to modeling wall panels. In this model, the member is divided into several segments, and each segment consists of parallel layers. Some layers would represent the concrete material and other layers would represent the steel material. The constitutive laws for concrete and steel materials are defined and assigned to appropriate layer. Different approaches are employed for modeling shear behavior of concrete using this method. In addition to the concrete axial/flexural layer, a shear layer must be implemented; shear constitutive laws are needed for modeling this layer. Also shear behavior of concrete can be modeled using diagonal layers. In these layers shear stresses convert to axial stresses acting on the principal plane of the layer and axial constitutive laws will be used. Results show that, estimated strength and force-displacement curve are in the good agreement with experimental results. concrete diagonal layer characteristics and tension modeling method of concrete are key parameters for modeling squat shear walls using SAP 2000 and concrete shear layer characteristics are key parameter for modeling squat shear walls using PERFORM 3D. It can be said that strength is better estimated than stiffness using this type of analysis.

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In this study, the finite element technique was used to analyze the thermo-mechanical behavior of the submerged arc butt-welded plates. In order to investigate the effects of the welding parameters on the magnitude of the submerged arc welding process efficiency, the distortions obtained from the finite element simulation were compared with experimental results. For studying the effects of welding voltage, current and speed on SAW process, finite element model with acceptable accuracy was developed. Welding efficiency of each sample were estimated by calibration of the finite element model. The angular distortions were studied in carbon steel plates of 12 millimeter thickness. Statistical analysis shows that the welding voltage and speed have no significant effect on the SAW efficiency. It is observed that by increasing the welding current, the magnitude of the welding efficiency increased significantly.

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Parallel piezo-flexural nanopositioning stages are extensively used in advanced nano-scale imaging and manipulation applications such as scanning probe microscopy systems. One of the major deficiencies of these devices is the coupled motion between their different axes. That is, the motion of stage in one direction interferes with motions in the other directions, leading to undesirable disturbances. In this paper, analytical, dynamic, experimental, and finite element analyses are carried out to investigate the major root cause of the cross-coupling effect. Using ABAQUS FEA software, a 3D model of the stage has been developed. Model consists of a central elastic body connected to the fixed frame through four flexural hinges. A cylindrical stack of multiple piezoelectric layers is placed between the moving central body and the fixed frame. Simulations are carried out for two different friction coefficients in the contact surfaces of the piezoelectric layers, and for different frame materials. It is observed that the main cause of the cross-coupling effect is the rotation of piezoelectric stack due to its friction with the stage moving in the tangential direction, concurrent with a change in the geometry of the stage.

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Recently, the use of coronary stents in interventional procedures has rapidly increased and different stent models, with different geometries and materials, have been introduced in the market. In order to select the most appropriate stent model, it is necessary to analyze and compare the mechanical behavior of different types of stent. In this paper, finite element method is used for investigating the effect of stent geometry and material properties on its behavior. Two commercially available stent designs with different geometries (the Palmaz–Schatz and NIR stents) and two different stent materials (stainless steel 304 and Cobalt alloy MP35N) are modeled and their behavior during the deployment is compared in terms of stress distribution in the stent and vessel, and outer diameter changes. Moreover, the effect of stent geometry and material properties on the restenosis after coronary stent placement is investigated by comparing the stress distribution in the arteries. According to the findings, the possibility of restenosis after coronary stenting is lower for NIR stent in comparison with Palmaz–Schatz stent. Moreover, stainless steel 304 is more suitable material for manufacturing stents, in comparison with the other one.

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In a mechanical assembly, errors arising from part manufacturing or assembly process may cause significant variation in final assembly with respect to the ideal model and affect the quality and performance of product. In sheet metal products due to high order of compliancy of components, errors generated during assembly process are as important as parts’ manufacturing tolerances. Therefore, it is crucial to have a comprehensive model in order to analyze the assembly process of these structures and represent the relationship between part tolerances and final assembly errors. However, it should be noted that assembly processes are often complex and nonlinear in nature. In sheet metal structures, the most important factor that makes the assembly process nonlinear is contact interaction between mating parts during assembly. If this factor is disregarded and the assembly process is only represented based on linear force-displacement relationship, the model will result in part penetration and a remarkable difference between theoretical and experimental results will occur. Another important feature in sheet metal tolerance analysis is the surface continuity of components which makes the deformation of the neighboring points of a plate correlated. This paper aims to present a new methodology for tolerance analysis of compliant sheet metal assemblies in which a nonlinear finite element analysis is integrated with improved sensitivity-free probability analysis in order to account ...

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In this article, an analytical procedure is presented for prediction of linear buckling load of a waffle cylinder stiffened by an array of equilateral triangles. The grid stiffened shell is subjected to axial loading condition. The shell has simply supported boundary conditions at its two edges. The equivalent stiffness of the stiffener and skin is computed by superimposing between the stiffness contributions of the stiffeners and skin with a new method. Total stiffness matrix of the shell is composed of stiffness matrix of skin and grids with special volume fractions. In this analysis, using energy method, equilibrium equations of the grid stiffened shell are extracted based on the thin shell theory of Flugge. The Navier solution is applied to solve the problem. A 3-D finite element model was also built in ANSYS software to show the accuracy and validity of the present solution. The results show that the present new approach has high accuracy and precision. The effect of various geometrical parameters on the critical buckling load is investigated. Due to the stability and accuracy, the present method can be used by many designers and engineers to improve their design quality.

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Soft tissue abnormalities are often correlated with a change in the mechanical properties of the soft tissue. New developing non-invasive techniques with the ability of early detection of cancerous tissue with high accuracy is a challenging state of art. In this paper, a new method is proposed to investigate the liver tissue cancers. Hyperelastic behavior of a porcine liver tissue has been extracted from the in vitro stress-strain experimental tests of the tissue. Hyperelastic coefficients have been used as the input of the Abaqus FEM software and the palpation of a physician has been simulated. The soft tissue contains a tumor with specified mechanical and geometrical properties. Artificial tactile sensing capability in tumor detection and localization has been investigated thoroughly. In mass localization we have focused on deeply located tumor which is a challenging area in the medical diagnosis. Moreover, tumor type differentiation which is commonly achieved through pathological investigations is studied by changing the stiffness ratio of the tumor and the tissue. Results show that the new proposed method has a high ability in mass detection, localization and type differentiation.

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In this paper, the effect of ductile damage on the behavior of a dented pipe subjected to internal pressure is investigated by experimental and numerical methods. In the numerical investigation, the plastic behavior of pipes under indentation is studied using continuum damage mechanics theory and the elastic-plastic finite element analysis. Finite element calculations are carried out using the damage plasticity model proposed by Xue and Wierzbicki (X-W). The proposed damage plasticity model incorporates effects of four parameters that play important role in predicting the fracture initiation, namely the damage rule, the softening effect, the hydrostatic pressure and the Lode angle. The target dent depth is considered as an indication of the load bearing capacity of the pipe under indentation process by a rigid spherical indenter. To validate numerical calculations, a series of experimental tests are conducted on the API XB steel pipe with atmospheric pressure. After verification, numerical calculations for different ranges of internal pressures, wall thicknesses and indenter diameters with and without damage effect are carried out for aluminum 2024-T351 pipe and results are compared. It is shown that damage plays an important role on the load bearing capacity of an indented pipe. Results of the present study confirm the credibility of the proposed model in predicting the ductile fracture under multi-axial state of stress loadings.

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Composite materials are widely used in aerospace, automotiveindustry, and other fields because of special mechanical properties.In this study, a step by step numerical analysis was developed to predict the fatigue life of E-Glass/Epoxy fiber reinforced laminates with (0, 90, 0, 90) s and (90, 0, 90, 0) s configurations. In the proposed Finite Element (FE) analysis, Hashin’s failure criterion was used which can distinguish the failure modes. The iterative algorithm was utilized so thatat each step of solution, the maximum load was applied to the model and then the stress componentswere obtained numerically at every nodes of the model. Then the appropriate failure criterion was applied to inspect the possible failure in all layers of each element. For failed layer in an element, material properties were degradedaccording to the failure mode and progressive damage theories. In other elements whichhad not been failed, the damage parameter was calculated. If the value of the damage parameter in each element exceeds 0.9, the layer of the element was assumed to be failed and the algorithm was continued. The predicted fatigue life was compared with the experimental results in the literature and good agreement was observed.

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Quantitative computed tomography (QCT) -based finite element analysis is a commonly accepted approach for prediction of mechanical behavior of bones. The objective of this research is to suggest linear criterion in order to accelerate and increase the precision of predicting of failure load in femoral bone. Accordingly, ten fresh frozen femora were QCT scanned and performed to use in this study. The specimens were loaded under eight different orientations. Finite element model for these samples were generated from QCT images, and related mechanical properties were calculated for each single voxel based on the value of density. In addition, the models were analyzed by linear finite element method. Risk factor that defines as the strain energy density divided to yield strain energy for each element was used for calculations of failure load. These values were sorted for particular loads in finite element model, and the correlations between experimental and numerical results were compared. Finally, eight linear criterions for eight different load conditions were presented which shows magnificent correlation between empirical results (average slope: 0.8903 and average R2: 0.8668). These correlations make it possible to accelerate the prediction of femoral fracture load in various orientations. This research shows a robust and fast method for prediction of failure in bones that can be used for multiple loads and orientations.

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Traumatic brain injury (TBI) has long been known as one of the most unspecified reasons for death around the world. This phenomenon has been under study for many years and yet questions remain due to its physiological, geometrical and computational complexity. Because of the limitations in experimental study on human head, the finite element human head model with precise geometric characteristics and mechanical properties is essential. In this study, the visco-hyperelastic parameters of bovine brain are extracted from experimental data and finite element simulations which are validated by experimental results. Then a 3D human head including brain, skull, and the meninges is modeled using CT-scan and MRI data of a 30-years old human. This model is named “Sharif University of Technology Head Trauma Model (SUTHTM)”. After validating SUTHTM, the model is then used to study the effect of G acceleration. Damage threshold based on consciousness in terms of acceleration and time duration is developed using HIC and Maximum Brain Pressure criteria. Results revealed that Max. Brain Pressure ≥ 3.1 KPa and HIC ≥ 30 are representative of loss of consciousness. Also, 3D domains for the loss of consciousness based on Max. Brain Pressure and HIC criteria are developed.

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An experimental procedure is used to determine the transient response of an elastomeric isolator under the impact loading conditions and a numerical procedure is developed to evaluate the corresponding acceleration transmission ratio and shock response spectrum. In the experimental analysis the elastomeric isolator is connected to a resonance beam subjected to the shock loading of a pendulum striker and the shock level is measured using acceleration sensors mounted along three orthogonal directions in the basement and free end of isolator. The shock response spectrum diagram and the level of wave attenuation are determined based on the measured acceleration levels for a wide frequency range. Finite element model based on mode superposition approach is developed to analyze the impact response of elastomeric isolator using the mode shapes with frequency in range of impact excitation spectrum. Due to the importance of longitudinal response of isolators, the numerical model is employed to evaluate the longitudinal output acceleration time history of isolator. The number of elements, time step for motion equation integration and the number of mode shapes are studied and the optimized corresponding values are selected based on the convergence of the numerical results. The calculated results for wave attenuation level and shock response spectrum diagrams correlate well with the experimental measurements under two different impact loading conditions and the present model can be used to evaluate the performance of isolators depending on the level of impact loads and transmission acceleration and displacement ratios in the output of elastomeric isolators.

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Iran with more than 11000 historical & monuments constructions is introduced one of the oldest civilizations in the word. Moreover, most of major earthquake in the world is referred to Iran , that is a serious threat for historical building that because during these constructions usually seismic loads are not considered, therefore it is necessary to identify these buildings behaviour in front of this natural hazard (earthquake), and doing necessary actions to strengthening the buildings and even reconstruct them in some cases. One of these splendid constructions is historical Tabriz citadel or Arge- Alisha Tabriz. Remained Citadel Alisha is a U shape plan with average 33 meters height, 51.2 meters width, 21.1 meters length. Arge Tabriz is situated in a city that is a high earthquake prone area. Thus because of different faults in this area and Arge- Alisha’s historical & cultural significance, this safety assessment of this building is unavoidable. Historical masonry structures have complex geometry that because of erosion, humidity and their materials mechanical properties has changed a lot. Usually, there is not enough exact information about compose materials of internal parts of the walls. On the other hand, because these constructions are cultural monuments of a country doing destructive tests for recognizing materials mechanicals properties is against international laws. Therefore producing a numerical model for construction analysis seems difficult, and if applicable solving it by software using FEA programs is time consuming. Simplified Kinematic Limit Analyses (SKLA) is a powerful method for historical building safety assessment analysis and its usage for retrofitting purpose that is permissible by O.P.C.M. 3431 Italian ordinance in both of the linear and nonlinear. In this research linear analysis is used for SKLA analysis. Because of masonry buildings have a rigid box behaviour, often local collapse mechanism (part of structure) is more important than its global collapse mechanism .this method assume that is collapse local, and large part of the structures are collapsed during earthquake. To identify probable collapse mechanism, we can use collapse of similar structure in the past earthquakes events. In this paper a research has been about this method (SKLA) capabilities for Tabriz Alisha Citadel seismic safety analysis. The results show that it doesn’t have enough safety against earthquake prone loads in the site. The analysis of both methods is more or less similar. Non linear time history response analysis results includes: displacement, stresses, wall’s collapse time, while SKLA only used for seismic safety assessment in different mechanisms. This method advantages such as, no need to exact information about materials mechanical properties and any destructive and non destructive test cause this method to be a powerful tool for evaluating seismic safety of historical buildings especially for huge and complex geometry structures. If we choose behaviour factor of structure 2 based on Italian ordinance, 3 mechanisms will not be active, although capacity and demand of the structure in three mechanisms have close value that indicates getting close to mechanism formation threshold.