Abstract: Bullet penetration in steel plate is investigated with
the help of three-dimensional, non-linear, transient, dynamic, finite
elements analysis using explicit time integration code LSDYNA. The
effect of large strain, strain-rate and temperature at very high velocity
regime was studied from number of simulations of semi-spherical
nose shape bullet penetration through single layered circular plate
with 2 mm thickness at impact velocities of 500, 1000, and 1500 m/s
with the help of Johnson Cook material model. Mie-Gruneisen
equation of state is used in conjunction with Johnson Cook material
model to determine pressure-volume relationship at various points of
interests. Two material models viz. Plastic-Kinematic and Johnson-
Cook resulted in different deformation patterns in steel plate. It is
observed from the simulation results that the velocity drop and loss of
kinetic energy occurred very quickly up to perforation of plate, after
that the change in velocity and changes in kinetic energy are
negligibly small. The physics behind this kind of behaviour is
presented in the paper.
Abstract: A problem is formulated for the natural oscillations of a circular plate of linearly variable thickness on the basis of the symmetry method. The equations of natural frequencies and forms for a plate are obtained, providing that it is rigidly fixed along the inner contour. The first three eigenfrequencies are calculated, and the eigenmodes of the oscillations of the acoustic element are constructed. An algorithm for applying the symmetry method and the factorization method for solving problems in the theory of oscillations for plates of variable thickness is shown. The effectiveness of the approach is demonstrated on the basis of comparison of known results and those obtained in the article. It is shown that the results are more accurate and reliable.
Abstract: Optimizations of Plate Heat Exchangers (PHS) have received great attention in the past decade. In this study, heat transfer and pressure drop coefficients are compared for rectangular and circular PHS employing numerical simulations. Plates are designed to have equivalent areas. Simulations were implemented to investigate the efficiency of PHSs considering heat transfer, friction factor and pressure drop. Amount of heat transfer and pressure drop was obtained for different range of Reynolds numbers. These two parameters were compared with aim of F "weighting factor correlation". In this comparison, the minimum amount of F indicates higher efficiency. Results reveal that the F value for rectangular shape is less than circular plate, and hence using rectangular shape of PHS is more efficient than circular one. It was observed that, the amount of friction factor is correlated to the Reynolds numbers, such that friction factor decreased in both rectangular and circular plates with an increase in Reynolds number. Furthermore, such simulations revealed that the amount of heat transfer in rectangular plate is more than circular plate for different range of Reynolds numbers. The difference is more distinct for higher Reynolds number. However, amount of pressure drop in circular plate is less than rectangular plate for the same range of Reynolds numbers which is considered as a negative point for rectangular plate efficiency. It can be concluded that, while rectangular PHSs occupy more space than circular plate, the efficiency of rectangular plate is higher.
Abstract: Geometrically nonlinear axisymmetric bending of a shallow spherical shell with a point support at the apex under linearly varying axisymmetric load was investigated numerically. The edge of the shell was assumed to be simply supported or clamped. The solution was obtained by the finite difference and the Newton-Raphson methods. The thickness of the shell was considered to be uniform and the material was assumed to be homogeneous and isotropic. Sensitivity analysis was made for two geometrical parameters. The accuracy of the algorithm was checked by comparing the deflection with the solution of point supported circular plates and good agreement was obtained.
Abstract: In the present study, the problem of geometrically nonlinear free vibrations of functionally graded circular plates (FGCP) resting on Pasternak elastic foundation with immovable ends was studied. The material properties of the functionally graded composites examined were assumed to be graded in the thickness direction and estimated through the rule of mixture. The theoretical model is based on the classical Plate theory and the Von Kármán geometrical nonlinearity assumptions. Hamilton’s principle is applied and a multimode approach is derived to calculate the fundamental nonlinear frequency parameters, which are found to be in a good agreement with the published results dealing with the problem of functionally graded plates. On the other hand, the influence of the foundation parameters on the nonlinear frequency to the linear frequency ratio of the FGCP has been studied. The effect of the linear and shearing foundations is to decrease the frequency ratio, where it increases with the effect of the nonlinear foundation stiffness.
Abstract: Analytical investigation of the free vibration behavior
of circular functionally graded (FG) plates integrated with two
uniformly distributed actuator layers made of piezoelectric (PZT4)
material on the top and bottom surfaces of the circular FG plate
based on the classical plate theory (CPT) is presented in this paper.
The material properties of the functionally graded substrate plate are
assumed to be graded in the thickness direction according to the
power-law distribution in terms of the volume fractions of the
constituents and the distribution of electric potential field along the
thickness direction of piezoelectric layers is simulated by a quadratic
function. The differential equations of motion are solved analytically
for clamped edge boundary condition of the plate. The detailed
mathematical derivations are presented and Numerical investigations
are performed for FG plates with two surface-bonded piezoelectric
layers. Emphasis is placed on investigating the effect of varying the
gradient index of FG plate on the free vibration characteristics of the
structure. The results are verified by those obtained from threedimensional
finite element analyses.
Abstract: The limit load carrying capacity of functionally
graded materials (FGM) circular plates subjected to an arbitrary
rotationally symmetric loading has been computed. It is provided that
the plate material behaves rigid perfectly plastic and obeys either the
Square or the Tresca yield criterion. To this end the upper and lower
bound principles of limit analysis are employed to determine the
exact value for the limiting load. The correctness of the result are
verified and finally limiting loads for two examples namely; through
radius and through thickness FGM circular plates with simply
supported edges are calculated, respectively and moreover, the values
of critical loading factor are determined.