Finite element modelling of plastics fittings

A finite element analysis has been performed on plastic tees to minimise and/or distribute more evenly the high stress in the stress concentration regions, by redesigning the tee in the area of high stress. Many geometries (17 cases) have been analysed by adding local reinforcement to the region of high stress, as well as by varying parameters such as extemal/intemal area fillet radii, internal reinforcement thickness, internal reinforcement length, and so on. Each case included two profiles, i.e. tees only, and tees with pipes cemented into all three outlets of the fittings. The effect of each parameter and the local reinforcement is also discussed. It is found that the finite element method can be used as an effective approach to the design of plastic fittings, and the linear analysis is sufficient to effectively determine the stress concentration areas which are likely sites for failure initiation, when tested for fatigue under cyclic pressure. 1