FEA helps assess the structural integrity of a vessel under various conditions. You might outsource this analysis, and the resulting report can be quite technical. Let's break down what a typical FEA report contains and how to interpret it.
Levels of Detail in FEA Reports
The comprehensiveness of an FEA report depends on the project, consultant, and budget. A detailed report allows for better evaluation of the analysis and results. However, such reports can be expensive and time-consuming. You might receive anything from a basic summary to an in-depth analysis of every step.
Our focus here isn't on performing FEA, but on understanding the key information you'll find in a typical report.
Typical Steps in FEA
Define Material Properties (density, elasticity, etc.)
Create or Import Geometry
Create Finite Element Mesh (dividing the model into small elements)
Apply Loads and Boundary Conditions (how the pressure vessel is fixed and loaded)
Define Analysis Type and Options (e.g., including non-linear effects)
Solve the Analysis
Review and Evaluate Results
What to Expect in an FEA Report
Most FEA reports will address each of the above steps in some detail. Here's a breakdown of what to look for:
Material Properties: The report should list the material properties used in the analysis, including those for temperature effects if applicable.
Geometry: The report should discuss which parts of the vessel were included in the model, any exclusions, and any simplifications made. Consider the appropriateness of these choices.
Finite Element Mesh: This is crucial for accurate stress prediction. A poor mesh can lead to underestimating stresses. The report should describe the element types used and include mesh plots.
Solid vs. Shell Elements: 3D models use either solid or shell elements. Solid elements come in various shapes, and their quality significantly impacts results. Well-shaped elements with gradual size changes throughout the model are ideal.
Linear vs. Quadratic Elements: Linear elements have nodes only at corners, while quadratic elements have additional mid-side nodes for more accurate results but require longer computation times.
Mesh Refinement: The mesh should be more refined in areas with high stress gradients, such as around nozzles and openings. An adequate number of elements through the shell thickness is also important for accurate bending stress prediction.
The report should include mesh plots to allow you to assess its quality.
Loads and Boundary Conditions: The report should confirm that the relevant loading scenarios have been analyzed. Boundary conditions define how the model is fixed or constrained. Their appropriateness significantly impacts results.
Analysis Type and Options: There aren't many analysis-specific options for pressure vessels. Including non-linear geometric effects might be necessary for large deformations under load, but this is uncommon for pressure vessel analyses.
Results and Evaluation: This is the most critical part. Typical results include displacements and stresses. Here's what to consider when evaluating them:
Do the results seem reasonable? Displacements and stresses should be logical.
Do the stresses away from discontinuities due to internal pressure match hand calculations?
Are the reactions consistent with the weight and loading?
Are the high-stress areas evaluated, and are there any discounted areas with justification?
By understanding these key aspects of an FEA report, you, as a pressure vessel fabricator, can better interpret the analysis results and ensure the structural integrity of your vessels.
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**The content of this article is taken from web open source. The blogs are intended only to give technical knowledge to young engineers. Any engineering calculators, technical equations and write ups are only for reference and educational purpose.
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