Abstract
Although various types of anti-roll torsion bars have been developed to inhibit excessive roll angle of the electric multiple unit (EMU) car body, it is critical to ensure the reliability of structural design due to the complexity of the problems involving time and uncertainties. To address this issue, a multi-objective fuzzy design optimization model is constructed considering time-variant stiffness and strength reliability constraints for the anti-roll torsion bar. A hybrid optimization strategy combining the design of experiment (DoE) sampling and non-linear programming by quadratic lagrangian (NLPQL) is presented to deal with the design optimization model. To characterize the effect of time on the structural performance of the torsion bar, the continuous-time model combined with Ito lemma is proposed to establish the time-variant stiffness and strength reliability constraints. Fuzzy mathematics is employed to conduct uncertainty quantification for the design parameters of the torsion bar. A physical programming approach is used to improve the designer’s preference and to make the optimization results more consistent with engineering practices. Moreover, the effectiveness of the proposed method has been validated by comparing with current methods in a practical engineering case.
Highlights
Reliability-based design optimization (RBDO) is an important way to improve the reliability of products under uncertainty in the design stage
The time-variant reliability models of the torsion bar are first built related to the stiffness and strength considering the uncertainty and time-variant property
The physical programming method is presented to handle the multi-objective design optimization to avoid the selection of the weight factors
Summary
Reliability-based design optimization (RBDO) is an important way to improve the reliability of products under uncertainty in the design stage. Time-variant reliability-based multi-objective design optimization (TRBMDO) is a necessary approach to guaranteeing the lifecycle reliability and safety of products while the balance of several objectives and other constraints are satisfied. Yu et al [15] proposed a multi-objective design optimization framework combining both the time-variant reliability and robustness. As the most part of the anti-rolling device, the time-variant reliability of the anti-roll torsion bar will directly affect the operating safety of the vehicle. Dong et al [24] provided a multi-response robust optimization method for the anti-roll torsion bar based on a stochastic model. A time-variant reliability-based multi-objective fuzzy design optimization (TRBMFDO) method for the anti-roll torsion bar of the EMU is proposed. The TRBDO constraints related to the stiffness and strength are first established by accounting for the timevariant stochastic working conditions and the working principle of the anti-rolling torsion bar.
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