Prototype Plastic Pressure Vessel

The Problem

It was suspected that the concept design of prototype plastic pressure vessel would not be strong enough to withstand the high pressures applied to the component. It was decided that an in-depth Finite Element Analysis should be carried out prior to any material being machined. The problem was complicated by the fact that the plastic material that the unit was made out of behaved non-linearly with temperature. Since the unit was expected to operate over a range of temperatures it required a careful analysis.

The Approach

The model generation, problem setup and analysis was carried out and a non-linear analysis was chosen to accurately model the physical problem. Loads and constraints were applied as boundary conditions and temperature dependent stress-strain properties were programmed into the software using appropriate polynomials. A number of non-linear analysis were then carried out at over a range of temperatures which then allowed an insight into how the unit would behave.

The Result

The analysis indicated that the unit was well within save levels of stress and displacement at all temperatures. This indicated that the unit was perhaps over designed and prompted an investigation in order to optimise the materials and weight of the design. It was found that a substantial reduction in material could be obtained whilst ensuring that the stresses remained at safe levels over the required working range.