The proposed approach consists of three main steps. The first step aims to determine the vectors of deterministic and random variables, for reducing the computational time by omitting the insignificant uncertainties of certain random variables. A reliability analysis is performed in the second step, for estimating the probability of failure. Two reliability methods are used for this purpose, namely the Monte Carlo simulation technique and the first-order reliability method (FORM). The economical requirements are integrated into the reliability analysis in the third step, using two reliability-based design optimization (RBDO) methods. Based on the work of Aoues and Chateauneuf [1], the reliability index approach (RIA) method and the sequential optimization and reliability assessment (SORA) method are used for their efficiency and accuracy.

The proposed approach is applied for the design of a chisel plough, for integrating the randomness of tillage forces derived from the uncertainties of tillage system parameters [2], into the design analysis. Two performance criteria are considered in the reliability analysis. The first performance criterion is related to the mechanical resistance of soil tillage machines and the second one is related to the quality of soil tillage operation. Furthermore, the correlation between the tillage forces is taken into account in the reliability analysis.

The results of the reliability analysis show that the FORM method can be used for estimating the failure probability, by considering both the first performance criterion and the correlation between the tillage forces. The results of the RIA and SORA methods show that the optimal solutions obtained by these methods are nearly identical. However, the SORA method is more efficient and less time consuming than the RIA method. Therefore, the SORA method can be adopted for solving the RBDO problem for soil tillage machines. The compression between the results of SORA method and the initial design indicates that the SORA method improves slightly the reliability index and reduces the objective function by 9.25%.

1

Y. Aoues, A. Chateauneuf, "Benchmark study of numerical methods for reliability-based design optimization", Structural and Multidisciplinary Optimization, 41, 277-294, 2010. doi:10.1007/s00158-009-0412-2

2

A. Abo Al-kheer, M.G. Kharmanda, A. El-hami, "Probabilistic analysis of soil tillage forces", in "Proceedings of the 18th Triennial ISTRO Conference", Izmir, Turkey, T5-003-1/T5-003-15, 2009.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £145 +P&P)