The objective of this work is to provide an efficient tool of Reliability-Based Design Optimization (RBDO) for soil tillage machine design process in order to achieve designs with a required reliability (safety) level. An efficient methodology that controls the reliability levels for different statistical distribution cases of random soil properties is developed. This developed strategy is based on design sensitivity concepts in order to determine the influence of each random parameter. The application of this method consists in taking into account the uncertainties on the soil tillage forces. The tillage forces are calculated in accordance with analytical model of McKyes and Ali with some modifications to include the effect of both soil-metal adhesion and tool speed. The different results show the importance of the developed strategy to improve the performance of the soil tillage equipments considering both random geometry and loading parameters.
design, optimization, structural reliability, random variables, soil properties, soil tillage equipment.
In the deterministic design optimization [1,2], the designer aims to reduce the engineering design cost without caring about the effects of uncertainties concerning materials, geometry and loading. The resulting optimal solution may therefore represent an inappropriate reliability level. However, the integration of reliability analysis during the optimization process leads to reduce the structural weight in uncritical regions that does not only provide an improved design but also a higher level of confidence in the design. This approach can be carried out in two separate spaces: the physical space and the normalized space. Since many repeated searches are needed in the above two spaces, the computational time for such an optimization is a big problem. The solution of the above nested problems leads to a high computational cost, especially for large-scale structures. The major difficulty lies in the structural reliability evaluation, which is carried out by a special optimization procedure. In order to improve the numerical performance, an efficient method is developed based on the optimality conditions. In this work, we use a statistical study of the soil tillage forces, based on soil property randomness.
1. Arora, J.S. Introduction to Optimum Design. McGraw-Hill, New York, NY, 1989.
2. Haftaka, R.T., Gurdal, Z. Elements of Structural Optimization. Kluwer Academic Publications, Dordrecht, Netherlands, 1991.
3. McKyes, E., Ali, O.S. The Cutting of Soil by Narrow Blades. Journal of Terramechanics, 1977, vol. 14, no. 2, pp. 43-58.
4. Mouazen, A.M. and Nemenyi, M. Finite element analysis of subsoiler cutting in non-homogeneous sandy loam soil. Soil & Tillage Research, 1999, no. 51, pp. 1-15.
5. Hasofer, A.M., Lind, N.C. An exact and invariant first order reliability format. J. Eng. Mech, ASCE, EM1, 1974, no. 100, pp. 111-121.
6. Lemaire, M. Fiabilité des structures. Paris, Hermes- Lavoisier, 2005, p. 506.
7. Feng, Y.S., Moses, F. A method of structural optimization based on structural system reliability study of numerical methods. J. Struct. Mech., 1986, no. 14, pp. 437-453.
8. Kharmanda, G. Numerical and semi-numerical methods for reliability-based design optimization. Structural Design Optimization Considering Uncertainties. Taylor & Francis, 2008.
9. Aoues, Y., Chateauneuf, A. Benchmark study of numerical methods for reliability-based design optimization. Journal of Struct. Multidisc. Optim, 2010, vol. 41, no. 2, pp. 277-294.
10. Kharmanda, G., Antypas, I., Integration of Reliability Concept into Soil Tillage Machine Design. Vestnik of DSTU, 2015, no. 15(2), pp. 22-35.
