Structural Durability Design Optimization and Its Reliability Assessment

Mechanical fatigue subject to external and inertia transient loads in the service life of mechanical systems often leads a structural failure due to accumulated damage. Structural durability analysis that predicts the fatigue life of mechanical components subject to dynamic stresses and strains is a compute intensive multidisciplinary simulation process, since it requires an integration of several computeraided engineering tools and large amount of data communication and computation. Uncertainties in geometric dimensions due to manufacturing tolerances cause the indeterministic nature of fatigue life of the mechanical component. Due to the fact that uncertainty propagation to structural fatigue under transient dynamic loading is not only numerically complicate but also extremely expensive, it is a challenging task to develop structural durability-based design optimization process and reliability analysis to ascertain whether the optimal design is reliable. The objective of this paper is development of an integrated CAD-based computeraided engineering process to effectively carry out the design optimization for a structural durability, yielding a durable and cost-effectively manufacturable product. In addition, a reliability analysis is executed to assess the reliability for the deterministic optimal design. NOMENCLATURE ( , ) a • • Energy bilinear form ( ) • ! Load bilinear form z Displacement vector L Crack initiation fatigue life W Weight for design optimization b Design parameter; b = [b1, b2,..., bn] T g(d) design constraint of design parameters , l u b b Lower and upper bound of design parameter d X Random vector; X = [X1, X2,..., Xn] T x Realization of X; x = [x1, x2,..., xn] T G(X) Constraint of random parameters Pf Probability of failure fX Probability density function μ Mean of random vector X; μ = [μ1, μ2,..., μn] β Reliability index f K Fatigue-strength reduction factor t K Stress intensification factor q Notch sensitivity factor