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