A versatile stereo photogrammetry based technique for measuring fracture mode displacements in structures

Shmueli, J.; Eder, Maximilian; Tesauro, Angelo

doi:10.1016/j.precisioneng.2014.07.004

Cited by 13 publications

(12 citation statements)

References 7 publications

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“…Figure 12 (a) shows that the critical angles for the TE-joint leading to opening effects are within the second and fourth quadrant. This is consistent with measurements performed during blade tests with similar loading directions as presented in [10,11]. It is remarkable that the TE-opening modes consistently occur within almost the same loading directions in different cases.…”

Section: Discussionsupporting

confidence: 90%

“…The following influenced the investigations performed in this paper: It was known from both experimental blade research and from numerical analyses [10,11] that blades that naturally undergo large deformations experience geometrically non-linear in-plane warping deformations that might be responsible for adhesive joint failure. An analytical investigation of geometrically non-linear effects on a simple cross-section as discussed in [12] supports this suspicion.…”

Section: Introductionmentioning

confidence: 99%

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Effects of geometric non-linearity on energy release rates in a realistic wind turbine blade cross section

Eder

Bitsche

Belloni

2015

Composite Structures

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Section: Discussionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Effects of geometric non-linearity on energy release rates in a realistic wind turbine blade cross section

Eder

Bitsche

Belloni

2015

Composite Structures

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“…7 are consistent with the measurements of local relative displacements taken in vicinity of the trailing edge of a SSP34 wind turbine blade. Figure 14 shows two different combined edgewise-flapwise loading directions and the associated bending moment vectors as conducted in two separate blade tests reported in [22] and [13]. The trailing edge was closing for a resulting bending moment direction of α=210…”

Section: Discussionmentioning

confidence: 99%

“…This finding was significant as the structural impact of the Brazier effect can no longer be neglected in the blade design process. Recent experimental and numerical investigations of fracture mode deformations near the trailing edge of a wind turbine blade [13] showed that in-plane deformations could be attributed to the Brazier effect. More importantly it could be seen that the trailing edge 'opened' for certain loading directions and load levels far below the capacity limit of the blade, all of which makes the trailing edge susceptible to fatigue damage.…”

Section: (C)mentioning

confidence: 99%

A qualitative analytical investigation of geometrically nonlinear effects in wind turbine blade cross sections

Eder

Bitsche

2015

Thin-Walled Structures

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This article analytically investigates the Brazier effect on asymmetric thinwalled sections subject to biaxial bending. In the latter case a torsional moment -in this paper referred to as Brazier torsion -is induced, which proved to be a vital part of the solution. By means of a generic cross section, that was inspired by a wind turbine blade it is demonstrated that geometric nonlinear effects can induce an in-plane opening deformation in re-entrant corners that may decrease the fatigue life. The opening effect induces Mode-I stress intensity factors which exceed the threshold for fatigue crack growth at loads well below the load-carrying capacity of the beam. The findings in this paper are twofold: Firstly, the investigated analysis procedure can be integrated into the design process of wind turbine blade cross sections. Secondly, the proposed approach serves as a basis for computationally efficient numerical analysis approaches of structures that comprise complex geometry and anisotropic material behaviour -such as wind turbine rotor blades.

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“…These large deflections, in conjunction with high out‐of‐plane and low in‐plane cross‐section stiffness, lead to geometric non‐linear in‐plane cross‐section deformations. This bending‐induced in‐plane warping effect—also referred to as Brazier effect or cross‐section ovalisation as investigated for blades by Damkilde and Lund as well as Cecchini and Weaver —is typically associated with mode‐I and mode‐II SERRs as discussed in . The formation of geometrically non‐linear lengthwise wave deformation patterns in the trailing edge increases the severity.…”

Section: Introductionmentioning

confidence: 99%

A comprehensive investigation of trailing edge damage in a wind turbine rotor blade

2016

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Wind turbine rotor blades are sophisticated, multipart, lightweight structures whose aeroelasticity-driven geometrical complexity and high strength-to-mass utilization lend themselves to the application of glass-fibre or carbon-fibre composite materials. Most manufacturing techniques involve separate production of the multi-material subcomponents of which a blade is comprised and which are commonly joined through adhesives. Adhesive joints are known to represent a weak link in the structural integrity of blades, where particularly, the trailing-edge joint is notorious for its susceptibility to damage. Empiricism tells that adhesive joints in blades often do not fulfil their expected lifetime, leading to considerable expenses because of repair or blade replacement. Owing to the complicated structural behaviour-in conjunction with the complex loading situation-literature about the root causes for adhesive joint failure in blades is scarce. This paper presents a comprehensive numerical investigation of energy release rates at the tip of a transversely oriented crack in the trailing edge of a 34m long blade for a 1.5MW wind turbine. First, results of a non-linear finite element analysis of a 3D blade model, compared with experimental data of a blade test conducted at Danmarks Tekniske Universitet (DTU) Wind Energy (Department of Wind Energy, Technical University of Denmark), showed to be in good agreement. Subsequently, the effects of geometrical non-linear cross-section deformation and trailing-edge wave formation on the energy release rates were investigated based on realistic aeroelastic load simulations. The paper concludes with a discussion about critical loading directions that trigger two different non-linear deformation mechanisms and their potential impact on adhesive trailing-edge joint failure.

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A versatile stereo photogrammetry based technique for measuring fracture mode displacements in structures

Cited by 13 publications

References 7 publications

Effects of geometric non-linearity on energy release rates in a realistic wind turbine blade cross section

Effects of geometric non-linearity on energy release rates in a realistic wind turbine blade cross section

A qualitative analytical investigation of geometrically nonlinear effects in wind turbine blade cross sections

A comprehensive investigation of trailing edge damage in a wind turbine rotor blade

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