NUMERICAL AND EXPERIMENTAL STUDIES ON PROBABILITY DISTRIBUTION FEATURE OF VON MISES STRESS OF STRUCTURE UNDER SINGLE-DIMENSIONAL AND MULTI-DIMENSIONAL RANDOM EXCITATIONS

摘要

In this paper, the probability distribution features of Von Mises stress of a conical shell-plate built up structure subject to single-dimensional and multi-dimensional random excitations are investigated numerically and experimentally. Firstly, an approach is proposed to estimate Von Mises stress probability distribution of the complex structure under the various random excitations, which assumes a two-parameters Weibull distribution model. Additionally, a method is developed to determine the Weibull distribution parameters. Seven random excitation cases are considered, which include three single-axis random excitation cases and four multi-axis random excitation cases. With Monte Carlo method, the time histories of Von Mises stress can be obtained and thereafter the parameters of Weibull distribution model can be identified based on the given method. The identified results reveal that Von Mises stress probability distributions follows the Weibull model well for all studied cases. Secondly, single-dimensional and multi-dimensional random vibration tests of the conical shell-plate built up structure are performed using MAV-6000-50H type three-axis electromagnetic shaking table. Seven kinds of excitation cases same as those in numerical studies are applied respectively. The strain responses in three orthogonal directions at multi points of structure are measured and then used to calculate the corresponding Von Mises stress process therein. The test results of the first seven modal frequencies agree well with the numerical results, which indicates the accuracy of the established numerical model. Moreover, the experimental results show that the measured Von Mises stress processes in seven cases all obey the Weibull probability distribution well, which demonstrates experimentally the reasonability of the present assumption. The work provides the theoretical basis for fatigue life estimation of structure subjected to multi-dimensional random excitations.