Once product specifications are identified the next task is to design the product. Mainly design is performed based on design formulas, hand calculations, product experience and more complex products trial & error process based on selected initial design is used. This is not a well established process and involves more challenges for designing. And hence design validation is important. The FEA is one of the design validation method which analyse the real world problem with the actual loading environment. And if the product does not sustain for applied loading then its design fails. So based on the FEA results we can suggest some design changes to improve the design instead of redesigning. It is important for FEA analysts to understand the problem correctly to identify the weak point in the design, such as high stress region, higher deformation, etc.
The generic FEA design suggestion in case of failure:
Static load:
- Increase thickness (example: Increase support bracket thickness in case of failure),
- Reinforcing pad (additional repad for nozzle shell junction failure),
- Stiffeners and angle plate addition (stiffener addition for shell failure under buckling scenario),
- Gusset plate and ribs addition (example: Gusset plates to avoid local bending)
Thermal load:
- Sliding joint between pipe and clamp instead of fixed joint. It will help to reduce stress levels.
- Slotted holes instead of circular holes (sliding saddle in case of pressure vessel), it allows sliding movements and helps to reduce stress levels.
Dynamic load:
- The basic dynamic analysis is modal analysis and here the main cause of failure is due to resonance. The resonance occurs when natural frequency matches with the excitation frequency. When an FEA Analyst observes such a scenario, then he tries to shift the natural frequency by local stiffening in respective critical mode shapes direction.
- For example if motor base matching frequency with motor frequency then local stiffening either in the form of increasing thickness or providing stiffener on the motor support are added.
