A crack is introduced by replacing the axial spring between nodes k and k+1 with a breakable spring characterised by a traction–separation law:
[ T(\delta) = \begincases K_\textel , \delta, & 0 \le \delta < \delta_c \ T_\max \exp!\big[-\beta (\delta-\delta_c)\big], & \delta \ge \delta_c \endcases ]
The fracture energy (G_c) is enforced by integrating the area under the curve: orcaflex crack full
[ G_c = \int_0^\infty T(\delta) , d\delta ]
Marine flexible structures are subjected to complex, multi‑axial loading: vortex‑induced vibrations (VIV), hydrodynamic drag, wave‐induced tension, and ship‑induced motions. Over time, these loads generate cyclic stresses that can initiate micro‑cracks, which may grow under the combined influence of fatigue and corrosion. A crack is introduced by replacing the axial
OrcaFlex, developed by OrcaFlex Ltd., is the de‑facto industry tool for time‑domain analysis of marine lines. Its core algorithm treats a line as a series of lumped masses linked by linear or nonlinear springs representing axial, shear, and bending stiffness. While this representation excels at capturing large‑scale dynamics, it does not natively support localized fracture mechanics.
For those interested in using OrcaFlex, it's essential to obtain the software through official channels. This typically involves: The fracture energy (G_c) is enforced by integrating
| Step | Action |
|------|--------|
| 1 | Pre‑processing – identify potential crack locations from inspection data (e.g., ultrasonic NDT). |
| 2 | Model set‑up – generate the baseline OrcaFlex line model (mesh, hydrodynamics, boundary conditions). |
| 3 | Insert UDE – replace the axial spring(s) at the identified locations with CrackElement. |
| 4 | Calibrate – run a short static load case to match measured stiffness and initial crack opening. |
| 5 | Dynamic simulation – execute the full time‑domain analysis (wave spectra, vessel motions). |
| 6 | Post‑processing – extract crack length vs. time, residual tension, and failure probability. |
