A Load Sequence Design Method for Hydraulic Piston Pump Based on Time-Related Markov Matrix

Accelerated life test (ALT) is commonly used to assess lifetime of mission critical and expensive products. Accurate ALT requires realistic load sequence representative of the actual and/or expected work conditions. A novel method, using the Markov information matrix, is proposed in this paper to produce the load sequence to be applied in the ALT. The proposed method provides several advantages, including improved efficiency as well as capturing dynamic characteristics of the loading conditions, such as transition frequency and cumulative time effect of the load. This paper presents the Markov method for analyzing the load sequence, in which the Markov information matrix is modified by taking into account the cumulative effect of each load level. The model is then applied to the ALT of hydraulic piston pumps, which are widely used in aircraft, in order to perform analysis of the cumulative damage. Considering the actual aircraft operation, hidden Markov model is used to generate the equivalent accelerated load sequence of a pump. The load sequence can be easily applied on a test bench for the verification and approval of pumps. Finally, an accelerated sequence design method is proposed to guide the ALT. The method ensures the consistency of the transfer frequency and the cumulative damage caused by the load, which provides an equivalent sequence for the ALT.