TEAMER: Deeply Embedded Ring Anchor Fatigue Life Optimization

The data provided in this submission contain the analysis input files and result post-processing spreadsheets and scripts to perform the CFD analysis, load case development, strength FEA, fatigue FEA, and optimization tasks outlined in the project report. Below is a summary of the project overall.

This project provided valuable qualitative and quantitative insights into the corrosion behavior, structural performance, fatigue resistance, and optimization of the Deeply Embedded Ring Anchor (DERA). The findings, which are summarized below, have significant implications for future research and development:
1. The structural performance of an optimized DERA was within allowable values for strength criteria and fatigue criteria.
-Stress hot spots exist in the DERA at the bottom padeye gusset and insert plate weld and at the insert plate to shell weld.
-Peak stress was successfully reduced by 61% (from 596 MPa to 234 MPa), compared to the baseline design, through design optimization.
-Fatigue life was increased by a factor of 862 (compared to the baseline design), through design optimization, and the unfactored fatigue life of 621 years exceeded the target fatigue life of 250 years for the structure.

2. The optimization methodology employed in this project successfully optimized the DERA design.
-The DOE optimization methodology utilized 40 simulation cases to map the design space, providing the data to optimize the structure.
-In addition to converging to the optimal component dimensions, optimization resulted in several key findings, including: Objective function selection is critical to achieve optimum design as per the overall project goals. Design could be optimized for weight, maximum fatigue life per unit weight, total cost of anchor including raw material and manufacturing, etc. The optimization process shown here remains consistent irrespective of the objective function. Surrogate functions generated from DOE help designers understand the impact of geometric parameters on the entities of interest.

3. Electrochemical corrosion of the padeye's carbon steel, immersed in a seawater environment, was calculated for the DERA design, and compared against corrosion allowances that should be considered per relevant industry standards. The nominal total corrosion of 0.381 mm over a 25-year operating life is not expected to significantly drive fatigue performance.

Overall, this project successfully achieved the goal of utilizing the DOE optimization process to improve the DERA design.
In summary:
-The peak stress was successfully reduced to keep the utilization ratio below 1.0.
-The fatigue life was improved by orders of magnitude, exceeding the target life of 250 years.
-Field validation is recommended for real-world performance verification.

This project successfully demonstrated that the DOE optimization process is a valuable tool that will allow designers to design efficient structures in a reliable and efficient way. This project has generated a roadmap for designers of marine renewable energy assets to optimally design their systems, reducing capital expenditures (CAPEX) and thus the levelized cost of energy (LCOE). For the DERA design, geometric dimensions that exceeded the strength utilization and fatigue life expectations were found using the DOE optimization process. Further optimization is possible by considering asymmetric design thus expanding the design space for DOE, however the process remains consistent with what is demonstrated here. By ensuring anchor functionality throughout its design life, free from impairment due to corrosion and fatigue, this project directly benefited the broader marine energy sector. It will drive economic growth by making marine energy installations more cost-effective for large-scale deployment and stimulating job creation. From a research perspective, the collaboration with Stress Engineering Services, Inc. (SES) ensured access to corrosion and fatigue expertise, providing valuable insights and advancements in marine anchor technology. The project will enhance marine energy systems' reliability and sustainability, supporting efforts to reduce fossil fuel reliance and combat climate change.

This project is part of the TEAMER RFTS 13 (request for technical support) program.