Dorota Mazurek
Stress Engineer — Joints & Fasteners · Structural Analysis
Warsaw, Poland
Stress Engineer specializing in bolted and threaded joint analysis for aerospace structures. Main tool is the VDI 2230 standard for high-duty bolted joint assessment, supplemented by ECSS standards for space applications. Develops and maintains the team's bolt calculation spreadsheet library and performs FEM verification for complex multi-bolt joints.
Expertise
- VDI 2230 bolt joint analysis
- ECSS fastener standards
- bolt pattern analysis under eccentric loading
- clamping force loss assessment
- FEM verification of hand calc bolt loads
Technologies
Work History
2025-01
Clamping force loss due to vibration — assessed loosening risk for bolts in vibration-critical joint using Junker test data interpretation and Yamamoto-Kasei criterion.
Challenge: Junker test data was available only for dry friction coefficient — in-service bolts had thread-locking compound (Loctite 243). Loctite significantly changes the vibration loosening threshold. Had to apply correction factors from supplier technical data rather than direct test.
Learned: Thread-locking compounds change bolt loosening behavior fundamentally — they shift the loosening threshold to higher transverse amplitudes. Junker test data for uncoated bolts is not directly applicable to Loctite-treated bolts.
2024-09
FEM verification of hand-calculated bolt loads for a complex 12-bolt engine mount — ANSYS with BEAM188 bolt elements and COMBIN39 pretension springs. Compared with hand calc bolt loads.
Challenge: COMBIN39 pretension spring approach in ANSYS APDL gives bolt preload but cannot correctly model bolt flexibility (shear stiffness). PRETS179 pretension element is more physically correct but less documented for complex multi-bolt models.
Learned: ANSYS pretension element (PRETS179) is more accurate than the COMBIN39 spring approach for bolt modeling. The extra setup time is justified for complex multi-bolt joints where bolt shear stiffness contributes to load sharing.
2024-03
Excel-based bolt pattern analysis tool for eccentric loading — given bolt pattern geometry and external load, computes bolt loads using elastic center method (rigid base plate assumption).
Challenge: Elastic center method assumes rigid base plate — in flexible structures, bolt load distribution can differ significantly. Implemented an FEM-based correction factor that adjusts elastic center results for flange flexibility.
Learned: The elastic center method (rigid plate) is conservative for bolt tension in flexible joints and non-conservative for bolt shear. Flexible base plate methods or FEM are necessary when flange stiffness is comparable to bolt stiffness.
2023-11
Through-thickness stress analysis in flanged casing joint under non-uniform bolt loading — prying action from eccentric pressure load. Used beam-on-elastic-foundation model to estimate flange bending.
Challenge: Beam-on-elastic-foundation model underestimated flange bending by 25% compared with 3D FEM due to local 3D effects at bolt hole — ligament bending not captured in 1D beam model. FEM verification was necessary for this case.
Learned: Beam-on-elastic-foundation is a good first approximation for flange prying but becomes inaccurate when the flange-to-bolt pitch ratio is large or when local bolt hole effects are significant. Know when to escalate to FEM.
2023-06
ECSS-E-HB-32-23A fastener analysis for satellite panel interface joint — fracture mechanics based life of fastener hole, interaction equation for combined tension and shear loading, lug analysis.
Challenge: ECSS fatigue factors of safety (FoS on load and FoS on life) are more conservative than commercial aerospace standards. The joint design that passed VDI assessment required redesign to meet ECSS FoS requirements.
Learned: Space and commercial aviation fastener standards differ significantly in safety factors and failure mode philosophy. Always confirm which standard applies before beginning joint analysis — mixing standards gives neither the right answer nor the right safety level.
2023-01
VDI 2230 bolt calculation for HPT casing split-line joint — 24-bolt pattern, titanium bolts (Ti-6Al-4V), inconel flange. Assessed clamping force loss due to differential thermal expansion from ambient to operating temperature.
Challenge: Thermal expansion difference between titanium bolt and Inconel flange caused significant clamp force relaxation at operating temperature — calculated residual clamp force was 15% below minimum required for gas sealing. Required switching to a higher bolt preload torque.
Learned: VDI 2230 thermal analysis (Part 1, Step R4) must include the full temperature range from assembly to operating condition including start-up transients. Worst case clamp force loss often occurs during rapid heat-up, not at steady-state.