Tolerance analysis of a product coupling geometric and architectural specifications in a probabilistic approach

This article describes tolerance analysis using a reliability-based approach to ensuring that a functional condition is satisfied. A particular feature of this procedure is that it defines the combined effects of geometric and dimensional ISO specifications for product parts, and the architectural parameters that define the relative positions of parts in contact. In the first part, we describe configuring the product parameters by geometric deviations, and from this, a global model is produced to characterise the variation in rotor/stator clearance in a turboshaft engine turbine. This model relies on tolerance zone dimensions, dimensional tolerances and architectural parameters. When clearance is examined using the reliability-based approach, links emerge between the turbine's architectural parameters and its geometric and dimensional specifications. Indicators can then be deduced which guide the designer in selecting the optimum turbine architectures.