JOURNAL OF SCHOOL OF ENGINEERING
Year:2000 | Volume:12 | Issue:1|Papers Count:6

A cause of failure in advanced composites is the effect of free-edge in composite plate's which generates three-dimensional stress field in venicity of free-edge. So, the effective axail stifness property and the effect of stress field at free-edge of laminated composite material with finite-width and [±ө] s orientation is studied. Due to the existance of free-edge effect, the reduction of effective stiffness could be predicted compared to classical theory. An analytical approximated analysis is presented to explain this effect. The characteristic of the analysis is the assumption of an introduction concerning the variation of stiffness reduction, with experimental results, approximated as a function. Then, the stiffness and strain field within the composite material is studed using this function. The finite element method is used to verify the calculations.

The main purpose of this paper is to study numerically the flow-field of an incompressible viscous flow in a curved pipe (1800) with two straight pipes attached to both ends. In order to extend the capabilities of the finite volume method, a boundary (body) fitted coordinate (BFC) method is used. Transformation of the partial differential equations to algebraic relations is based on the finite-volume method with collocated variables arrangement. For solving the obtained algebraic relations the TDMA in periodic state is used. To approximate the convective. fluxes, the differencing scheme of Van Leer is used and SIMPLEC handles the linkage between velocities and pressures. For verification of the code, a test case of flow in a (1800) curved pipe at Reynolds number of 242 is performed and the good agreement between the present results with the numerical and experimental data is obtained. This study showed that by adding two straight pipes at the ends of a curved (1800) pipe, the strength of the secondary flow in the curved zone is reduced.  

Combination of numerical solution of path-independent J-integral method which is based on conservation law of energy in conservative field with finite element method is a very powerful tool to analyze cracks with complex shapes and model geometry. In the present research after defining J -integral which includes three dimensional effects, concentrated loads inside the integration path and thermal gradient, a numerical method is proposed for the computation of J -integral on the basis of the results of a finite element analysis using 20-node isoparametric elements. This method allows the assessment of the values of a finite analysis using 20-node isoparametric elements. Finally some examples are given concerning three dimensional problems such as a penny-shaped crack, elliptical embedded and surface cracks. Comparison between results of present study and existing results in engineering literature show the ability of this method in analyzing plane cracks in three dimensional space.  

In nonlinear analysis of trusses, the effects of axial forces on flexural buckling of the members have been considered, but in many instances, the members of the space trusses are made of thin-walled open sections, and in these sections, consideration of the flexural torsional buckling shall be indispensable. In this paper, the elements of truss are seleded of thin-walled open sections. The critical loads of elements and large displacements of the joints have been considered. For considering the rotation of the members, the Eulerian system of coordinate axes has been applied. The effects of the torsional-flexural buckling have been presented on nonlinear behavior and stability of the structures, for the I, L, T and open circle section. It is shown that neglectiong of such effects creator remarkable error in calculation of buckling, especially in open circle trusses.

For any stainless steel a critical pitting temperature (CPT) can be defined, below which stable pits do not occure at any potential in an aggressive environment. The more highly alloyed stainless steel with molybdenum and nitrogen, the higher is the CPT. the effect of surface finishing on the CPT was investigated using potentiodynamic and potentiostatic techniques, on a quality 904 L stainless steel in 1M NaCl solution. The alloy showed a wide range of passivity, from corrosion potential (Ecorr) to tranpassivity potential (ETr) with no pitting at all temperatures bellow the CPT whereas at temperatures greater than the CPT pitting corrosion occured at the pitting potential It was found that the CPT depends on the final surface finishing and the smoothness of the surface increases the CPT. The highest CPT was recorded on the fine-finished surface (3 mm diamond paste) at 54°C and the lowest for a rough-finished surface (60 grit SiC) at 46°C.

Colloidal grout penetration into soils or porous rocks depends on their void volume and particle size of the grout material and also on shear resistance existing between the surfaces of the voids and the grout. Coarse sand and gravel soils or fissured rocks are the cases in which cement-water-bentonite slurry could be injected into. However, particle size distribution, liquid limit and plastic limit values and the density of the grout are important in addition to rheology properties like viscosity which has considerable effect on the flow of the grout through formation. Most of the colloidal grout is non-Newtonian fluids which are called Bingham fluids and their rheology properties are measured by rotational viscometer such as Stormer in the laboratory. Although, Marsh funnel is usually used as a relative method in the field, if used together with a chart, a metal plate and a mud balance, the rheology parameters of the grout can simply and cheaply be determined with 'satisfactory accuracy.