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Run npx skillmds@latest add ashfordeou/calculix-linear in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

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Is Calculix Linear free to use?

Yes. Installing skills from SkillMD is free. This skill is licensed under Apache-2.

Who published Calculix Linear?

ashfordeOU (@ashfordeou) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Calculix Linear by ashfordeou — Agent Skill

Name: Calculix Linear
Author: ashfordeOU

Calculix Linear

Use when running or checking linear static finite element analysis for aircraft structure with CalculiX (ccx): determine margin of safety from allowables versus FEA stresses, validate unit discipline before post-processing, and check von Mises stress results. The skill covers element-basis stress checks, margin computation, and unit conversion discipline so that allowables and computed stresses are compared in consistent units. Trigger: finite element, fea, calculix, ccx, stress analysis, margin of safety, von mises, unit discipline, static analysis.

ashfordeOU 68af0fd 3 files · 8.6 KB Updated Sep 17, 2026

File contents

CalculiX Linear Static FEA (structures/fem/calculix-linear)

Use when the task is linear static finite element analysis of aircraft structure with CalculiX (ccx): stress post-processing, margin of safety checks against material allowables, and unit discipline across the analysis chain.

Domain quick reference

Margin of safety: MS = allowable / actual - 1.0; a negative MS means the structure fails at the applied load.
Von Mises equivalent stress: sqrt(0.5*((s1-s2)^2 + (s2-s3)^2
- (s3-s1)^2)); compare it against allowables for ductile metals.
Unit discipline: allowables and FEA stresses must be compared in the same unit. Conversion factors to Pa: kPa 1e3, MPa 1e6, GPa 1e9, psi 6894.757, ksi 6894757.0.
FAR-25 structure requirements (25.301-25.307 loads and structural proof) set the certification context for the stress checks; this skill computes the checks, not the loads.

Workflow

Confirm the analysis is linear static (small displacements, linear materials) and record the unit convention of the ccx run.
Extract stresses at the element or node of interest from the ccx output; record the unit.
Convert the FEA stress and the allowable to a common unit with stress_to_pa / mos_units_discipline.
Compute margin of safety with margin_of_safety and classify with mos_status; negative margin = failed structure.
Check equivalent stress with von_mises where a scalar comparison is needed.
Confirm the deterministic checks with the contract test scripts/test_calculix.py.

Pitfalls

Comparing allowables and FEA stresses in different units (silent unit errors); always convert through Pa.
Treating a negative margin of safety as acceptable; it means the applied stress exceeds the allowable.
Using von Mises for brittle or directionally dependent materials without justification.
Applying linear-static checks to nonlinear or buckling-dominated responses.

Behavior contract (gate 3)

The margin, unit, and von Mises logic is exercised by the gate 3 contract test: scripts/test_calculix.py against scripts/calculix_logic.py (stdlib unittest, offline). Run: python3 scripts/test_calculix.py

Compliance

Standards referenced, not reproduced: FAR-25 is US government work (public domain); summary-only per standards-map.yaml and brief 06.
compliance: STANDARDS-REF, gated: false.

---name: calculix-lineardescription: Use when running or checking linear static finite element analysis for aircraft structure with CalculiX (ccx): determine margin of safety from allowables versus FEA stresses, validate unit discipline before post-processing, and check von Mises stress results. The skill covers element-basis stress checks, margin computation, and unit conversion discipline so that allowables and computed stresses are compared in consistent units. Trigger: finite element, fea, calculix, ccx, stress analysis, margin of safety, von mises, unit discipline, static analysis.license: Apache-2.0---# CalculiX Linear Static FEA (structures/fem/calculix-linear)Use when the task is linear static finite element analysis ofaircraft structure with CalculiX (ccx): stress post-processing,margin of safety checks against material allowables, and unitdiscipline across the analysis chain.## Domain quick reference- Margin of safety: MS = allowable / actual - 1.0; a negative MS means the structure fails at the applied load.- Von Mises equivalent stress: sqrt(0.5*((s1-s2)^2 + (s2-s3)^2 + (s3-s1)^2)); compare it against allowables for ductile metals.- Unit discipline: allowables and FEA stresses must be compared in the same unit. Conversion factors to Pa: kPa 1e3, MPa 1e6, GPa 1e9, psi 6894.757, ksi 6894757.0.- FAR-25 structure requirements (25.301-25.307 loads and structural proof) set the certification context for the stress checks; this skill computes the checks, not the loads.## Workflow1. Confirm the analysis is linear static (small displacements, linear materials) and record the unit convention of the ccx run.2. Extract stresses at the element or node of interest from the ccx output; record the unit.3. Convert the FEA stress and the allowable to a common unit with stress_to_pa / mos_units_discipline.4. Compute margin of safety with margin_of_safety and classify with mos_status; negative margin = failed structure.5. Check equivalent stress with von_mises where a scalar comparison is needed.6. Confirm the deterministic checks with the contract test scripts/test_calculix.py.## Pitfalls- Comparing allowables and FEA stresses in different units (silent unit errors); always convert through Pa.- Treating a negative margin of safety as acceptable; it means the applied stress exceeds the allowable.- Using von Mises for brittle or directionally dependent materials without justification.- Applying linear-static checks to nonlinear or buckling-dominated responses.## Behavior contract (gate 3)The margin, unit, and von Mises logic is exercised by the gate 3contract test: scripts/test_calculix.py againstscripts/calculix_logic.py (stdlib unittest, offline). Run:python3 scripts/test_calculix.py## Compliance- Standards referenced, not reproduced: FAR-25 is US government work (public domain); summary-only per standards-map.yaml and brief 06.- compliance: STANDARDS-REF, gated: false.

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