Geometrical reliability of overconstrained mechanisms with gaps

Reliability design relates generally to simulation of fatigue strength, thermal effects, etc. not to simulation of geometrical variations, i.e. tolerancing. The variables for geometrical reliability are manufacturing, gap and functional deviations. In case of isoconstrained mechanisms, the linear expression of dependencies between these variables allows to calculate failure probability. For overconstrained mechanisms, these linear expressions are not applicable for the whole behaviour of the mechanism; nevertheless, they are applicable for each particular configuration of contacts. The different configurations represent events taken into account in a numerical evaluation assumed by the Form–Sorm method. A case study, with numerical results, illustrates and validates the chosen process.