The engineering task
An ASME pressure vessel contains a complex detail for which cyclic stresses cannot be obtained reliably from nominal-stress formulae. Pressure, thermal gradients and external connection loads occur in several combinations. An elastic finite-element model is required to provide stress ranges for fatigue assessment.
Evaluation must distinguish primary, secondary and peak stress and form the governing stress differences through each cycle. Mean-stress effects, elastic correction, weld detail and cumulative usage from multiple cycle types must also be addressed.
Required design data
- ASME code edition and selected Part 5 assessment route
- Complete load points for every cycle type
- Temperature-dependent elastic material data
- Weld detail, design life and acceptance criteria
Technical solution approach
Define the assessment route
Set the applicable Design-by-Analysis and elastic-fatigue rules before modelling.
Calculate FEA load points
Evaluate every pressure, temperature-field and external-load extreme with the same model.
Classify stresses
Process stress tensors and linearised stress along critical paths in accordance with the code.
Determine fatigue parameters
Calculate alternating stress intensity, corrections and allowable cycles for each cycle type.
Sum usage
Accumulate individual contributions and assess total allowable usage and any required design changes.
Expected deliverables
Suitable SOL ALPHA modules
The modules form a technically plausible toolchain. Their final selection and sequence will be confirmed during the later calculation against the applicable code and project conditions.