DEVELOPMENT OF MEANINGFUL DISCRETIZATION SCHEME FOR FINITE ELEMENT ANALYSIS OF STRESS CONCENTRATION PROBLEM

Abstract

In finite element (FE) modelling, apart from proper element selection, selection of an appropriate discretization scheme is crucial in correctly evaluating the intended variables [2]. The discretization of any domain into finite elements is important as the value of the variables to be found is very much dependent on it. The manual discretization of any domain is very tedious and time consuming [4]. Hence the development of automatic mesh generation scheme is very important in FE analysis of a problem In the last two decades, automation of photoelastic analysis has received a greater impetus with the introduction of digital image processing techniques for data acquisition. The advent of Rapid prototyping technologies has made the model making simple and faster. Photoelasticity plays an effective role in selecting an appropriate discretization scheme as well as the boundary condition for modelling problems in stress analysis. A meaningful FE discretization is very important in evaluating the desired parameters in FE analysis. The adaptive mesh refinement emphasizes the need for a meaningful discretization of domain [2]. There are many software packages which automatically discretize domain using triangular elements but only few software are available dealing with quadrilateral elements. Domain discretization using quadrilateral elements can help one to use most versatile eight noded isoparametric element. Guideline for devising automatic mesh generation schemes for domain discretization using quadrilateral element can be obtained with the help of photoelasticity. This thesis presents a discretization strategy for meaningful discretization of the rail track subjected to eccentric__ load. The element chosen is eight noded isoparametric quadrilateral element due to its versality to represent complex domain. Due to asymmetry of the problem whole domain is discretized. The work evolved the generation of meaningful discretization scheme for the rail track subjected to eccentric load. The plane elasticity problem is solved for the rail track using the software FEM2DM.FOR. Since validity of any program is of great importance, the FE results are compared with the results obtained by experimental technique such as photoelasticity. Since the photo elasticity gives the contours of isochromatics fringes, the FE results are post processed to get the isochromatic fringe order. These fringe orders are used to vi simulate the results obtained in photoelasticity using plotting algorithm. The comparison is found to be good, hence validating the discretization. It is observed that both photoelasticity and FE are complementary. Photoelasticity can be used as tool to better discretize the domain and verify the FE modelling. FE can be used as a tool to separate the stresses. Thus by combining these two techniques complete and reliable stress analysis is possible. vii