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.Hydroelastic behavior plays a significant role in designing and constructing very large floating structures. There are different ways to reduce structure displacement and its stress due to wave. These structures are usually made separately out of the sea, and then components are connected to each other with rigid connection in installation location. Connecting components with joint connections to each other is one way to reduce the hydroelastic response. In this paper, the hydroelastic behavior of continuous structures is compared experimentally with structures composed of two and three sections. In order to simulate the hydroelastic behaviors of floating structure, the applied floating structure was 300 meters in height, 60 meters in width and its bending rigidity was equal to 4.77×1011 N.m2. Experimental model of aluminum was fabricated with length, width and height of 2, 0.55 and 0.04 meters respectively. polyethylene was used beneath aluminum plate in order to provide floating. The first model had no connection in its length; it was continuous. In the second model which consisted of two sections with 1 meter in length, there was a joint connection as a cross line in the middle of it. The third model consisted of three sections is made up by attaching three aluminum plates 67 centimeters in length which were connected together by hinges. In a wave generated tank of Graduate University of Advanced Technology laboratory with 16 meters in length and 1 meter in width and height, strain and vertical displacement measured at different points of experimental model. 5 regular waves’ periods of 0.67, 0.80, 0.91, 1.01 and 1.10 seconds were created. water depth was 70 centimeter. Comparison of the results shows that in all three models, the displacement in long waves is more than other waves. Also, in the models with hinge connection compared to the continuous model, the stress has been significantly reduced and its value has almost halved. At the first wave whose period is 0.67 second, the maximum stress is almost equal in the models with connections; so the models with three components reflected better performance regarding displacement and bending in comparison with other models. Due to the second wave (with periods of 0.8) displacement in the model with three components was less than the others, but the stress of this model was more than the model with two components. In such a case, in structure designing regarding the ratio of wave length to structure length, the more significant factor (displacement or stress) for the project must be preferred. In the last three waves (waves with longer length) the continuous model had less displacement. On the other hand, in this model which had no connections, the stress was more than the other cases. Therefore, a parameter which may offer both advantages can't be recommended. Since bending moment difference in the continuous model is twice more than the models with joint connections, if the structure displacement be within permissible limit of the project, using joint connection would be economical in designing.

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In this paper, an innovative flexible sandwich structure is introduced which can be used in shape changing (morphing) aircrafts that adapt their external shape to different flight conditions. First, different ideas for achieving smart aircraft in the literature is briefly reviewed and then characteristics of the new deformable sandwich structure as well as its different features in comparison to other proposed structures are described. Moreover, fabrication details of deformable and load bearable sandwich panel are explained. In an aircraft with variable camber wings, deformable sections can be supposed as a cantilever beam. As a result some specimens of new deformable sandwich structure are constructed and then tested as end-loaded beams. Since the numerical study of the new proposed structure requires an understanding of the mechanical behavior of components used, a comprehensive study about the mechanical behavior of individual components of structure is conducted. According to the observation of broken samples, a distribution of cavities resulting from the manufacturing process is supposed in one type of model to obtain more accurate numerical results. Finally, another example is analyzed with the same assumptions and it is shown that in the second example, the numerical results are close to the experimental data.

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Rigid Body-Spring Models (RBSM) are a kind of discrete models which are developed mainly for the simulation of quasi-brittle materials ranging from ceramic, concrete, and masonry, to rock and soil. In this approach, material domain is discretized to a set of rigid cells interconnected through a set of translational and rotational springs located at cell interfaces. These cells are constructed over a set of points (seeds) distributed regularly or randomly over the domain. When it comes to heterogeneous materials, the seeds may be located in accord to the geometry and distribution of inclusions. For two-dimensional problems, each rigid cell has normally two translational and one rotational degrees of freedom (DOFs). The springs may be distributed along the interface or lumped at a point called contact/computational point (CP) and activated by the relative movement of connecting cells. As a fundamental issues, before being applicable for the simulation of inelastic behavior of materials, the kinematics of an RBSM and also the force-displacement relations of its springs should be defined in such a way that the model can adequately predict the elastic behavior of continuum at both macro and micro scales. Our review of the literature shows that except one of the RBSMs, used in the current paper for comparison, others suffer from some shortcomings which result in their inaccurate elastic predictions. In the aforementioned model, cells are convex polygons generated by the Voronoi diagram of seeds (cell nucleus) and the spring set of an interface is comprised of two translational (normal and tangential) and one rotational springs located at the midpoint of the interface. Our study shows that, although this RBSM presents generally a reliable predictions, however, there exists some kind of scattering in the predicted micro strain and stress distributions. Accordingly, with the aim of eliminating the observed scatters, this paper borrows the interpolation functions of the conventional finite element method and presents a new kinematic formulation for the RBSM. In the new model, called FE-RBSM, a Delaunay tessellation is constructed over cell nuclei. This results in a network of triangular elements which can be considered as 3-node constant strain triangular finite elements. Two translational DOFs at each nucleus and two CPs per interface with normal and tangential springs are assumed. Next the triangles including the CPs are determined. Finally, the normal, tangential, and lateral strains of each CP are calculated by projecting the constant strain tensor of the associated triangle on the corresponding interface. In order to examine the efficiency and accuracy of the proposed FE-RBSM formulation, two kinds of numerical analyses including constant and variable stress fields are employed. For the case of constant stress field, a 100mm square sample is analyzed in uniaxial tension and pure shear. Besides, for the case of variable stress field, a 300mm square sample including a 10mm diameter hole at its centroid is analyzed in uniaxial and biaxial tension. Also, a 300mm diameter circle sample is analyzed under splitting compression. The results are compared with those of the selected RBSM and also the analytical solutions. They show that, compared to the RBSM, the FE-RBSM can better predict the macro elastic properties and also gives scatter-free microstress fields.

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Skeletal muscles simulation remains a controversial topic as a result of its complex anatomical structure and mechanical characteristics such as nonlinear material properties and loading conditions. Most of the current models in the literature for describing the constitutive equations of skeletal muscles are based on Hill's one-dimensional, three element model. In this paper a 3D constitutive model which is based on the hyper elastic behavior of skeletal muscle and energy function has been presented. By using the derivatives of such energy function for defining the Second Piola and Cauchy stresses, we able to describe the inactive behavior of skeleton muscles. The applied constitutive equations are an efficient generalization of Hamphury's model for the inactive behavior of skeletal muscle. In this paper using a 3D model, different modes of deformations of skeletal muscle such as simple tension, biaxial and shear tests has been investigated and material properties constants for each modes of deformation has been optimized by Genetic algorithm. Finally the results of the model simulations of each mode are compared with those obtained from experimental tests. Also, the model results are compared with the ones from two well- known hyper elastic Ogden and Mooney-Rivilin models in order to show the priority of the new developed 3D model to those aforementioned models has been shown.

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The effect of temperature on the viscoelastic behavior of chicken meat frankfurters was assessed by creep recovery tests. Compression creep-recovery tests were performed at room temperature (20°C) and refrigeration (5°C) on samples of cylindrical shape. The viscoelastic behavior of samples was characterized based on the parameters of the four-element Burgers Model. During the compression phase, greater deformation was observed in samples analyzed at higher temperature, and it was demonstrated by a drop in elastic modulus and internal viscosity values of Kelvin–Voigt elements with an increase in temperature. The final percentage recovery of frankfurter samples decreased with an increase in temperature. The differences in compliance between samples analyzed at different temperatures can be attributed to temperature-induced changes in the properties of frankfurter fat.

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The fluid induced vibration in fluid conveying pipes can cause fatigue and failure in the system. Therefore, controlling these unwanted vibrations and suppressing the vibrations of the fluid conveying pipe is important. In this paper by considering the passive vibration absorber for the fluid conveying pipe, the influence of the vibration absorber parameters on the dynamic behavior of the system is investigated. The governing equations of motion are obtained via the Newton’s second law, and analytical solutions for the characteristic equation and mode shapes of the system are obtained through the power series method. After verifying the obtained results, the effect of the vibration absorber parameters and the fluid flow velocity on the vibration behavior of the fluid conveying pipe have been investigated. Results show that by increasing the absorber mass, the effect of absorber on decreasing the oscillations amplitude is diminished. At different fluid velocities, the oscillation amplitude of the system can be reduced considerably by specifying proper values of the absorber parameters. At velocities near the critical velocity, where the oscillation amplitude reaches a maximum value, using a suitable vibration absorber may reduce the maximum oscillations amplitude of the system by 98%. The method presented in current study can be easily generalized to design passive vibration absorber for fluid conveying pipes with different boundary conditions.

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