M.Sc Thesis

M.Sc StudentGurevich Arkadi
SubjectReliability of Mechanical Design Based on a Model with
Uncertain Error
DepartmentDepartment of Quality Assurance and Reliability
Supervisor PROFESSOR EMERITUS Yakov Ben-Haim


This thesis presents a concept of design solution robustness estimation, which is based on information-gap models of uncertainty rather than on probabilistic concepts. Info-gap models quantify uncertainty as the size of the gap between what is known and could be known for an ideal solution. Info-gap models of uncertainty are particularly useful when data on the uncertainties are quite limited. In the proposed procedure a design is regarded as reliable if the robustness to failure from uncertain fluctuations exceeds a code-specified threshold. Design is thus based on immunity to uncertainty rather that on probability of survival. The key conclusion is that in order to choose a design one can exploit data about uncertainties without introducing probabilistic models. This is important when information is scarce, since verification of probabilistic models can then be difficult. 

The suggested approach is demonstrated and evaluated for two examples. The first example demonstrates the procedure of design-robustness estimation of a one-dimensional undamped linear oscillator with respect to uncertain input. This example shows the stages of the robust reliability analysis of a mechanical system and the method of transition from the robust reliability of a system to design robustness. The use of different info-gap models and their influence on the results of the analysis are presented in this work. In the second example the suggested approach is used for design-robustness estimation of a nonlinear static mechanical system with respect to uncertain properties of the system. The example demonstrates how the initial conditions of the design, for example the choice of the critical dimensionless strain, can effect the design decision.