Finite Element Analysis (FEA) is a computational technique that divides a structure or component into thousands of small elements — the "finite elements" — and uses numerical methods to calculate stress, strain, deformation, temperature or fluid behaviour at every point across the model. The result is a detailed map of how a real component behaves under real loading conditions, without needing to physically build and test a prototype.
In structural and mechanical engineering, FEA has become an essential tool for validating designs that cannot be fully checked by hand calculation, assessing areas of high stress concentration, and demonstrating code compliance where standard formula-based methods are not directly applicable.
How FEA Works — The Core Methodology
The FEA process follows three stages regardless of the software used:
Pre-Processing (Model Setup)
The engineer defines the geometry — either imported from a CAD model or built directly in the FEA pre-processor — and assigns material properties (Young's modulus, Poisson's ratio, yield strength, density, thermal conductivity). The geometry is then meshed: divided into elements (tetrahedra, hexahedra, shell elements, beam elements) whose size is chosen based on the expected stress gradient. Finer meshes capture stress peaks more accurately but increase computation time. Boundary conditions (supports, symmetry planes) and loads (pressure, gravity, thermal loads, point forces) are applied.
Solving
The solver assembles the stiffness matrix and solves a large system of simultaneous equations — potentially millions of degrees of freedom — to compute displacements at every node. From displacements, the solver derives strains and stresses using the constitutive material equations.
Post-Processing (Results Interpretation)
Results are visualised as contour plots of von Mises stress, principal stress, deformation or temperature. The engineer interrogates peak values, checks them against material allowables defined by the governing code, and produces a written report documenting methodology, loads, boundary conditions and conclusions.
Types of FEA Analysis
- Linear static analysis: the most common type, assumes small deformations and linear material behaviour. Used for most pressure vessel and structural checks under design loads.
- Non-linear analysis: accounts for large deformations, contact (e.g., gasket behaviour), or material plasticity. Required when the component may yield locally under design or overload conditions.
- Modal analysis: extracts the natural frequencies and mode shapes of a structure. Essential for equipment subject to vibration — compressor skids, pipe supports, elevated vessels.
- Transient dynamic analysis: applies loads that vary with time — blast, seismic ground motion, water hammer. Results show how stress peaks evolve over the event duration.
- Thermal and thermo-structural analysis: models heat transfer to find temperature distributions, then uses those temperatures as loads in a structural analysis to capture thermal stress — critical in heat exchangers and fired equipment.
- Fatigue analysis: post-processes cyclic stress results against S-N curves to estimate service life. Required by ASME VIII Div.2 and EN 13445 for pressure cycling equipment.
FEA Software Commonly Used in Industry
The choice of software depends on the analysis type, industry sector and client requirements:
- ANSYS Mechanical: industry-standard for oil & gas pressure vessels, structural components and seismic analysis. Widely accepted by Saudi Aramco and international operators.
- Abaqus (Simulia): preferred for advanced non-linear problems — creep, fracture mechanics, rubber components, soil-structure interaction.
- SolidWorks Simulation: efficient for smaller fabricated components, brackets, frames and lifting equipment where the geometry originates from a SolidWorks CAD model.
- STAAD.Pro / SAP2000: frame-element based analysis tools widely used for structural steel and pipe-rack design, complementing FEA for global structural checks.
When is FEA Required — and When is It Not?
FEA is not always necessary. Standard code formula approaches (ASME VIII Div.1, API 650, AISC 360) are sufficient for the majority of routine designs. FEA becomes necessary when:
- The geometry is outside the scope of formula-based code checks (irregular nozzle clusters, eccentric loadings)
- Cyclic loading requires fatigue life estimation
- Existing equipment has been modified and requires fitness-for-service assessment per API 579
- A client specification specifically requires FEA validation
- Lifting lugs, pad eyes or temporary attachments need to be qualified
SLETEC's FEA analysis services cover structural, pressure vessel and thermal analysis using ANSYS and SolidWorks Simulation. Our reports are prepared with stress classification tables, load case summaries and clear pass/fail assessments referenced to the governing code or client specification.