MODIFIED NEWMARK METHOD FOR HEAD-DISK INTERFACE DYNAMICS

The head-disk assembly in a disk drive has been modeled as a multi-deg ree-of-freedom system. To simulate the dynamics of the head-disk assem bly, the Newmark method with delta > 1/2, alpha > 1/4 is usually appli ed. This method may introduce some algorithmic dissipation which is de sired for eliminating high-frequency oscillation. However, this featur e is acquired at the cost of accuracy. In this paper, a modified Newma rk method is presented. The method is based on the standard Newmark me thod with delta = 1/2, alpha = 1/4 and the extrapolation technique. It is achieved by expressing the numerical amplification matrix of the h igher-order algorithm as a linear combination of the basic amplificati on matrices evaluated at selected instances of time. The matrices are combined with different weighting factors. The pairs of the selected i nstance of time and the corresponding weighting factors are free param eters. Unconditionally stable, higher-order accurate and dissipative a lgorithms can be derived by properly choosing the free parameters. Alg orithms of up to fourth-order accuracy are presented in this paper. De tailed analyses on stability, numerical dissipation and numerical disp ersion are also given. Comparisons of the modified method and some con ventional methods, such as the Newmark method, the Wilson method and t he HHT method, are presented to demonstrate its versatility; in partic ular, its dissipative features and accuracy. The proposed method is no t only suitable for simulating head-disk assembly dynamics, but is als o applicable to the analysis of a wide spectrum of the dynamics of str uctural and mechanical systems. (C) 1997 Elsevier Science Ltd.