Abstract:Based on the series expansion, the series forms of right stretch tensor in polar decomposition are given, and the different approximate expressions of right strech tensor are obtained by selecting different number of series terms. From the different expressions, the series expansion with the least error is found. The effectiveness of the approximate expression is verified using some simple examples. Compared with the approximate expressions of right strech tensor and rotation tensor proposed by Huang Mojia, the approximate expressions of right strech tensor and rotation tensor given in this paper are of simple forms, high accurate and widely applicability.