Patent ID: 6532421
Filing Date: 2003-03-11
Classification: G07C

Abstract:
A method for estimating a life of an apparatus under a narrow-band random stress amplitude variation, including the steps of:sampling and storing data on stress, strain, and temperature which occur in an apparatus during operation; analyzing the stored data to determine a random stress amplitude variation &sgr;(t) (instantaneous) being imposed on the material of the apparatus; determining a model expression of load variation by the following conditions of: i) converting the random stress amplitude variation &sgr;(t) (instantaneous) determined in the above step into a sum of a time averaged value &sgr;(t) (mean) and a stochastic variation &sgr;â€²(t) which is a stress varying at the averaged value and thereabouts, and ii) when the random stress amplitude variation &sgr;(t) (instantaneous) determined in the above step is in a narrow band, approximating a damage coefficient indicative of a quantity of damage accumulated in the material of the apparatus per one stress amplitude variation by a linear expression which is a sum of a quantity of damage which the material undergoes from the stress at the time averaged value &sgr;(t) (mean) and a quantity of damage which the material undergoes from the stress at the stochastic variation &sgr;â€²(t): determining a theoretical correction value of damage accumulation based on statistic characteristic data on a life of the material itself; completing an estimating expression of damage accumulation by substituting thereinto the model expression of load variation and the theoretical correction value of damage accumulation; and calculating the life of the apparatus by the completed estimating expression of damage accumulation.