6 things all engineers should know before using FEA

Engineers in every industry are integrating finite element analysis (FEA) into the design cycle to ensure that their products are safe, cost-effective, and fast to market. But, analysis is not as simple as putting a CAD model into any FEA package.

There are more software options today than ever before. For many years, engineers were limited to using linear static stress analysis. More recently, finite element packages have been extended to include nonlinear static stress, dynamic stress (vibration), fluid flow, heat transfer, electrostatic, and FEA-based stress and motion analysis capabilities. These capabilities are frequently combined to perform analyses that consider multiple physical phenomena, and are tightly integrated within a CAD interface.

This article will briefly discuss some FEA basics and then outline what engineers need to know when they decide to use FEA.

1. FEA basics. A finite element model is a discrete representation of the continuous, physical part being analyzed. This representation is created using nodes, which are connected together to form elements. The nodes are the discrete points on the physical part where the analysis will predict the response of the part due to applied loading. This response is defined in terms of nodal degrees of freedom (DOF). For stress analysis, up to six degrees of freedom are possible at each node (three components of translation and three components of rotation), depending on the element type selected (e.g., beam, plate, 2D, and 3D elements).

The grid of connecting elements at common nodes comprises the mesh. When adjacent elements share nodes, the displacement field is continuous across the shared element boundary and loads can be transferred between the elements.

2. Design criteria. In any analysis, an engineer first needs to determine the significant physical phenomena and environmental conditions to which the part will be exposed, and also the desired design objective. For example, one of the most common concerns for engineers involves maximizing the part's durability.

The first step in an analysis is to determine whether the design will be subject to static or dynamic conditions. In its real-world application, is the part fixed in space, subject to vibration, or does it move relative to other parts in the assembly? What happens when you run the entire product through its motion cycle? For years, engineers faced with expensive computing resources have simplified the problem by using static FEA software to calculate stresses at a single instant in time. This method works only if the design does not experience impact, motion, or changes in applied loads over time.

3. Multiphysics. In addition to considering a part's ability to withstand mechanical stresses, FEA software often enables engineers to predict other real-world stresses, such as: the effects of extreme temperatures or temperature change (heat transfer analysis), the flow of fluids through and around objects (fluid flow analysis), or voltage distributions over the surface or throughout the volume of an object (electrostatic analysis).

Often these effects work in unison, so it is important that the FEA program can consider their effects on one another. For instance, a computer chip may be heating up over time,

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