A Global-Local Damage Assessment Methodology for Impact Damage on Offshore Wind Turbine Blades During Lifting Operations

Abstract

Lifting the latest generation offshore wind turbines using floating crane vessels is extremely challenging. This comes with an elevated risk of blades impacting the tower or surrounding structures due to excessive crane tip motions from wave induced vessel motions. The wind turbine blades are primarily made of composite materials and thus are extremely vulnerable to impact loads causing complex damages and failure modes. One of the most critical damage type for wind turbine blades is delamination because delaminations cannot always be visually detected but can cause significant strength and stiffness reductions. An explicit structural response based approach was proposed in the previous work which is used to derive response based operational limits for single blade lifting operation using floating vessels considering probability of contact/impact and damages in the blade. An assessment of such impact induced damages on the blade was mentioned which includes modelling and predicting damages in the blade for different contact scenarios representing lifting operations in different sea states along with post impact residual strength estimation. This would require an efficient damage assessment methodology which can be utilized in practice with acceptable accuracy along with a reasonable computational cost. In this work, a simplified global-local based damage assessment methodology is presented. The paper focusses on ’shell-to-solid submodelling’ based impact damage prediction along with a brief outline of ’shell-solid coupling’ based residual strength study. The paper further presents the submodelling technique for impact investigations on DTU 10 MW blade section for a case when a projectile impacts the leading edge. Intraply damage mode based on Hashin failure criteria and Puck’s action plane theory was utilized as VUMAT in Abaqus-Explicit along with surface based cohesive behavior to model the inter-laminar failure mode. Finally, the damages and failure modes in the blade including impact induced delaminations are reported.

Structural Safety Assessment of Marine Operations From a Long-Term Perspective: A Case Study of Offshore Wind Turbine Blade Installation

“…The wind turbine blade mating process is a substantially demanding task, and calls for high precision [16][17][18][19][20]. The blade is lifted from the deck using a crane, and several bolted connections along with the guide pin at the root are mated with the flange holes of the preassembled hub ( Fig.…”

A comprehensive numerical investigation of the impact behaviour of an offshore wind turbine blade due to impact loads during installation

“…The effect of impact-induced loads on a fibre composite wind turbine blade are more serious compared to steel components such as transition pieces and monopiles [4,7]. The steel structures are inherently ductile in nature, and most of the energy during the impact is dissipated in the plastic phase or work hardening phase before the material fails [12].…”

“…A wind turbine blade, on the other hand, is comprised of composite sandwich materials, which provide a high stiffness-to-weight ratio, including excellent in-plane structural performance [7,12,13]. However, these materials are weak in their off-axis direction and are sensitive to impact loads [13].…”

“…Several intricate and interacting damage modes can develop [12,13,14], and they are not always detectable via visual inspection; however, such damage can grow under operational loads [15] and can cause global structural failure of the blade. In addition, damage of varying sizes, positions and locations in the blade could affect the residual strength and performance of the blade in a multitude of manners, and judging its criticality is thus difficult [4,6,7]. Haselbach et al [16] found that delamination arising close to the surface of the laminate of the blade at the suction side has a more adverse effect than delamination near the middle layers of the laminate of the blade.…”

“…Parameters determining contact/impact scenario Damage assessment of a composite structure due to impact loads is not a recent development. Scientists have been examining this research topic for several years, especially in aerospace and defense applications [7,14,17]. However, the problem of a lifted offshore wind blade suffering impact during installation tasks because of crane tip and blade motions is a novel research area.…”