FEA BY ENGINEERING 2 PRODUCTION, INC.
Finite Element Analysis (FEA)
Finite Element Analysis (FEA) provides the means to evaluate a component or product's performance with respect to simulated loads and operating conditions. Software solutions have become robust, less expensive and accurate to a point where analysis can be incorporated into every design.
FEA is a powerful tool that essentially divides a complex structure up into many small elements, allowing each of the stresses and deformations to be solved using known equations of elasticity. Because the boundaries of each element in contact with another element must have equal and opposite forces and equal deflections, a large array of equations can be generated and solved to determine the forces and deflections on all the elements. A critical issue is the constraints on the exterior elements that are meant to model the connection of the part to the world. For example, a cantilever beam has all the faces of elements at one end constrained to not have any deflections. But what about a simply supported beam?
FEA configures a model for analysis using a complex system of points or nodes, which are connected into a grid, called a mesh. This mesh has defined properties or characteristics, such as material, structural properties, elasticity, etc. The nodes are configured with particular density throughout the model dependant on the stress levels within a particular area. Areas of known elevated stress typically have a higher node density than those areas that will see little or no stress.
There are some types of elements, plates and shells that are two dimensional yet are assigned a thickness. These 2D elements can have an edge constrained to be simply supported (no linear displacement) or supported so there is no linear or angular displacement. Most design engineers creating new designs use a solid modeling system or Computer Aided Design (CAD) software, and the solid modeler is often parametrically linked directly to an FEA program. Herein lies the challenge, because some (not all) FEA programs take a solid model and break it up into solid elements, where their solid elements can only be constrained along a surface which causes a moment constraint (no linear or angular translations) to always be imposed. The moment constraint does not always capture the intent of the designer and can cause a structure’s stiffness to be greatly over predicted. Fortunately, as shown, some FEA programs do allow a solid’s edge to be displacement but not rotation constrained. If an FEA program does not allow the edge of a solid to be simply constrained, thin solid flexural elements can be added.