Abstract: In order to understand the mechanical response of the sandwich shell of wind turbine blade in lifting process using slings and to prevent damage to the sandwich shell caused by stress concentration during lifting, a full-scale wind turbine blade single-point flexible lifting test was conducted. The study investigated changes in displacement and the distribution of strains during lifting to determine the lifting failure mode. Based on the test results, the accuracy of two finite element models, namely node-restrained loading and flexible sling loading, was comparatively analyzed. Additionally, parameter analysis was performed to examine key factors influencing flexible lifting. The results indicate that the area of failure during single-point flexible lifting is near the lifting point, consistent with the failure mode under actual lifting conditions. Both node-restrained loading and flexible sling loading can predict overall displacement distribution quite accurately. However, the skin strain distribution during node-restrained loading differs from that at the lifting point, with significant experimental variations. The results from flexible sling loading are more precise. Parameter analysis revealed that contact stress significantly decreases with increased contact area. Expanding sling width, enhancing the elastic modulus and interface roughness effectively reduce stress concentration at the contact interface. Conversely, the height of sling point has no significant effect on the strain distribution and contact stress.

Key words: soft lifting sling, wind turbine blade, sandwich structure, lifting test, finite element analysis, composites