31 lines
1.1 KiB
Markdown
31 lines
1.1 KiB
Markdown
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# Study 02 — Stiffness Sweep (Method B)
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**Type:** Parametric — CBUSH Spring-to-Ground Sweep
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**Runs:** 22 (2 validation + 10 K_vert sweep + 10 K_lat sweep)
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**Model:** CBUSH elements at 5 interface points, offset ground nodes (−10mm Z)
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## What This Does
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Replaces fixed BCs with CBUSH springs. Sweeps translational stiffness from 1e4 → 1e10 N/m on log scale. Two independent campaigns:
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- Campaign 1: Sweep K_vert (laterals rigid)
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- Campaign 2: Sweep K_lat (verticals rigid)
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Finds the **knee point** where ΔWFE crosses the 1.0 nm budget.
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## .sim Setup Required
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1. Create 5 ground nodes (offset −10mm in −Z from each support node)
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2. SPC 123456 on all ground nodes
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3. Remove existing SPCs on 5 support nodes
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4. Create 5 CBUSH elements (support → ground, global coords)
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5. Create 2 PBUSH properties: 8001 (vertical, K=$K_vert) and 8002 (lateral, K=$K_lat)
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6. Create 2 NX expressions: `K_vert`, `K_lat` (default = 1e12)
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## Extractor
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Same as Study 01: Zernike annular OPD, 50 modes, J5+ filtered, annular aperture.
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## Output
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ΔWFE vs K curves → knee points → recommended minimum stiffness for StarSpec.
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