AUTOMATIC ADAPTIVE 3-D FINITE ELEMENT REFINEMENT USING DIFFERENT-ORDER TETRAHEDRAL ELEMENTS

Automatic reÞnement Þnite element analyses were carried out employing three di¤erent-order tetrahedral solid elements for the solution of 3-D stress analysis problems. Numerical results indicated that the adaptive reÞnement procedure could eliminate e¤ectively the e¤ect of singularities and the optimal convergence rate was achieved in all the examples tested. The preconditioned conjugate gradient technique was used for the solution of the large system of simultaneous equations. By interpolating the initial guess of the iteration solver from the previous converged solution, the number of iterations needed for the solution is lower than expected. Furthermore, when the mesh density distribution pattern has converged, it became even more e¦cient and independent of the number of degrees of freedom in the Þnite element mesh. The relative e¦ciency of the three di¤erent-order tetrahedral elements has also been compared in terms of storage and computational cost needed for achieving a certain accuracy. It is found that although the cubic T20 element can achieve the highest convergence rate, the T10 element is the most competitive and e¤ective element in terms of storage and computational cost needed