Abstract: The eight-level spectrum of torque is established by using the stochastic loading history of torsion shaft of military vehicles on various types of standard road surface. In consideration of the randomness of factors such as material performance, and fatigue influence coefficient, etc., the durability model is built by applying fatigue reliability theories. An optimization model, which takes the maximum durability of torsion shaft as the objective function when a vehicle travels for 6 000 km, is built based on the constraints such as rigidity reliability, structure dimension and so on. The approach that introduces the double-loop strategy for durability object conversion and the single-loop strategy for reliability bounds conversion is presented for this optimization model. The high computing accuracy of object value and the high efficiency of optimal computation are obtained. The results show that the durability of torsion shaft is improved obviously.

Key words: ordnance science and technology, torsion shaft, durability, reliability, optimization design, load spectrum