In the present study, the nonlinear forced vibration of symmetric laminated rectangular plates, including Glare fiber metal laminated rectangular plate, is investigated based on the first order shear deformation theory. The boundary condition is considered to be immovable simply support. The Galerkin method is used to obtain the nonlinear ordinary differential equation in terms of an unknown time function. The obtained equation is solved analytically by the multiple time scales method. The obtained results are compared with the numerical solution of the nonlinear ordinary differential equation of motion and a good agreement is found between them.
Finite element method is used to study the free vibration analysis of functionally graded skew plates. The material properties of the skew plates are assumed to vary continuously through their thickness according to a power-law distribution of the volume fractions of the plate constituents. The first order shear deformation theory is used to incorporate the effects of transverse shear deformation and rotary inertia. Convergence study with respect to the number of nodes has been carried out and the results are compared with those from past investigations available in the literature. Two types of functionally graded skew plates - Al/ZrO2 and Al/Al2O3 are considered in this study and the effects of the volume fraction, different external boundary conditions and thickness ratio on the natural frequencies are studied in detail.
In this paper, butt joining of Al5083 to commercially pure copper is investigated by friction stir welding method. The effects of transverse welding speed of the tool on the mechanical properties and microstructure of the joint were studied, experimentally. By examining different circumstances, changes in the joint strength were studied and optimized in term of transverse speed. Based on the obtained results, welding speed can improve or reduce the joint strength and an optimum value can be found for the welding speed. Welded Joint that was conducted at the rotation speed of 800 RPM and tool traverse speed of 60 mm min?1 had the highest tensile strength (i.e. about 98% of the weak base metal). Intermetallic compounds were formed in the stir zone and XRD results indicated that Al4Cu9 and Al2Cu were the intermetallic compounds in the stir zone. Micro-cracks formed around the intimatelic particles were observed in the section of joint.
A new fracture test specimen is suggested and analyzed using finite element method. The mode I and mode II stress intensity factors as well as the T-stress were calculated for three geometries and loading conditions. It is shown that the specimen, called single edge cracked ring (SECR), covers different mixed mode loading conditions from pure mode I to pure mode II. The SECR specimen also covers negative and positive values of T-stresses. From the practical view point, the suggested specimen can be used easily for mixed mode II fracture tests.
In this paper, an extended forming limit stress diagram (EFLSD) was applied to predict neck initiation failure in tube hydroforming of metal bellows. The proposed EFLSD was used in conjunction with ABAQUS/ EXPLICIT finite element simulations to predict the onset of necking in tube hydroforming of metal bellows. The amount of calibration pressure and axial feeding required to produce an acceptable part in finite element method (FEM) were compared with the published experimental data and a satisfactory agreement between the FEM and published test results was achieved. Therefore, the present approach can be used as a reliable criterion for designing metal bellows hydroforming processes and reducing the number of costly trials.
In this research, the flow stress of dual layer austenitic-martensitic functionally graded steels (FGSs) under hot deformation loading has been modelled considering the Zener-Hollomon constitutive equations as a function of temperature and strain rate. Functionally graded austenitic-martensitic steels consist of austenite (?) and martensite (M) phases placed on each other in different configurations and produced via Electro Slag Remelting (ESR). The boundary layers properties are obtained by experimental investigation on single phase materials. Finally, the theoretical model is compared with the experimental results measured in the temperature range 1000-1200 °C and strain rate 0.01-1 s-1 and a good agreement is found.
Development of knowledge of cardiovascular diseases and treatments strongly depends on understanding of hemodynamic measurements. Hemodynamic parameters, therefore, have been investigated using simulation-based methods. A two-dimensional model was applied for seven healthy subjects with echo-Doppler at rest. Echocardiography imaging was also utilized to gain the geometry of the aortic valve. Fluid-Structure Interaction (FSI) model was carried out, coupling an Arbitrary Lagrangian-Eulerian mesh. Pressure loads were used as boundary conditions on the valve’s ventricular and aortic sides. Pressure loads used were the calculated brachial pressures plus differences between brachial, central and left ventricular pressures. The FSI model predicted the velocity integration, stroke volume and cardiac output over a range of heart rates while rest. Numerical results generally had a difference of 5.4 to 15.87% with Doppler results. Linear correlations between numerical and clinical approaches have been applied. This makes possible predictions achieved from the FSI model to be gained which are highly accurate (e.g. correlation factor r = 0.995, 0.990 and 0.990 for velocity integration, stroke volume and cardiac output, respectively). The obtained numerical results showed that numerical methods can be combined with clinical measurements to provide good estimates of patient specific hemodynamics for different subjects.
Composite materials due to high strength and stiffness to their weight ratio are widely used in different structures. Hence, it is necessary to predict their failure behavior under loading. The delamination due to interlaminar stresses at free edges is one of the most important damage modes in laminated composites. In this study, this mode in cross-ply and angle-ply laminates has been investigated using a cohesive zone model. The advantage of this method is the possibility of modeling the delamination initiation and propagation without requirement to the presence of initial crack and remeshing. Hence, at first an interface element based on bilinear cohesive law was implemented in Ansys. Next, laminated plates with different lay-ups under uniaxial tension loading were modeled. Also Hashin’s failure criteria were used to predict ply damage initiation. Numerical results show that in angle-ply laminates with small fiber angle orientation, delamination in the shear mode is the dominant mode in the loss of structural strength. The numerical and experimental results for global load-displacement response show a good agreement. Also numerical results show that in cross-ply laminates even under in-plane loading, the damage behavior extremely depends on the stacking sequence. Studies show that in cross-ply laminates under uniaxial tension, if 90o plies are inserted in top and bottom surface of the laminate, the mode I delamination and matrix cracking will start later.
In this paper, harmonic forced vibration of circular functionally graded plate integrated with two uniformly distributed actuator faces made of piezoelectric material is studied. The material properties of the functionally graded substrate layers are assumed to be graded in the thickness direction according to the power-law distribution, also the distribution of electric potential field along the thickness direction of piezoelectric layers is modeled by a quadratic function. The governing equations are solved for simply supported boundary condition of the sandwich circular plate and the solutions are presented by elementary Bessel functions. The performance of the present model is compared with that of ?nite element analyses as well as other available literature by the presentation of comparative results obtained for several examples encompassing different power indexes and vibration modes. The results show that thickness of piezoelectric layer and changing the power index in FG material has a significant influence on the deflection and natural frequencies of system.
Cold working a hole decreases tendency of fatigue crack initiation and growth near the hole. It is due to creation of some compressive tangential residual stresses around the hole. But there are many uncertainties which affect the residual strain and residual stress field. In fact these uncertainties lead to have scatter in the test results and considering the residual strains and residual stresses as random variables. In this paper strains recorded by strain gages mounted around the hole during cold working process in seven pieces specimens, were analyzed by statistical tests and stochastic properties of mentioned random variables were obtained using SPSS software. The residual strains have been also distributed by normal probability distribution function.