Computer vision for SHM of civil infrastructure: From dynamic response measurement to damage detection – A review

Structural health monitoring at local and global levels using computer vision technologies has gained much attention in the structural health monitoring community in research and practice. Due to t...

A review of computer vision–based structural health monitoring at local and global levels:

Damage detection techniques for wind turbine blades: A review

Vibration-based damage detection in wind turbine blades using Phase-based Motion Estimation and motion magnification

Quantifying the condition of aging structures is important to verify structural integrity and long-term reliability. Structural health monitoring plays a key role in the prevention of catastrophic ...

Feasibility of using digital image correlation for unmanned aerial vehicle structural health monitoring of bridges

Large-area photogrammetry based testing of wind turbine blades

Measured data from operating systems are often acquired to predict structural health of a system. With only a few measurement sensors, very limited understanding of the system can be obtained. Utilizing some recent novel expansion results, full field information can be obtained to identify a more complete strain description for the system. Using these results in conjunction with an analytical prediction of the expected strains, comparisons and differences can be identified using time response data. The expected full field stress-strain from the analytical model is compared to the predicted full field dynamic stress strain from limited sets of measured locations due to either operating or imposed loading on the structure. Differences in strain distributions at many time increments can provide indications of regions of possible damage in the structure. The work presented in this paper identifies the methodology as well as some results to illustrate the usefulness of the approach.

Comparison of Full Field Strain Distributions to Predicted Strain Distributions from Limited Sets of Measured Data for SHM Applications

Traditional ply-based and zone-based models are limited in their ability to account for the fiber directions resulting from the forming of fabric-reinforced composite wind turbine blades. Compounding the problem is the presence of defects such as resin-rich pockets of the polymer matrix due to out-of-plane and in-plane waves resulting from the manufacturing process. As a result, blades are typically overdesigned, unnecessarily increasing weight and material costs. In the current research, a methodology is presented for simulating the manufacturing process for fabric-reinforced composite wind turbine blades using ABAQUS/Explicit. The methodology captures the evolution of the yarn directions during the forming process thereby allowing for a map of the fiber orientations throughout the blade. A hybrid approach using conventional beam and shell elements is used to model the various fabric layers. Using experimental shear, tensile, bending, and friction data to characterize the mechanical behavior of the fabric layers, the model captures in-plane yarn waviness and changes in the in-plane yarn orientations as they conform to the shape of the mold, as well as out-of-plane wave defects as a result of the manufacturing process. Subsequently, after the fabric layers have been laid into the mold and the final yarn orientations are known, the structural stiffness of the blade resulting from the resin-infused fabrics can be calculated. The methodology can thereby link the resulting bending and torsional stiffnesses of the blade back to the manufacturing process. This paper discusses the methodology for determining the material properties of the beam and shell elements in their final orientations in the cured composite to predict the structural stiffness of a wind turbine blade.

Simulating the Manufacturing Process and Subsequent Structural Stiffness of Composite Wind Turbine Blades with and without Defects

Complex composite structures, that are subjected to appreciable externally induced loading, will fatigue and fail over time. For many structures, imminent failure and loss of structural integrity is not externally apparent. Typical failure occurs at the interfaces between the structure’s surface and internal ribs or stiffening members. Conventional approaches for proper validation of full-scale exterior dynamic behavior of numerical models require a significant number of measurement points; unfortunately, interior dynamic response due to time-varying loads is not currently predictable from measured data.

Dynamic Stress-Strain Prediction from Limited Measurements in the Presence of Structural Defects

There are numerous modeling approaches that can be employed in the generation of composite models for wind turbine applications. Several more traditional approaches have been used over the past few decades. However, one modeling approach used for the generation of manufacturing models uses what is referred to as the unit cell approach. This modeling approach has been used for large deformation applications where the orientation realignment of the composite plies needs to be considered in the forming process. This modeling approach has been used for static and large deformation applications but not for dynamic modeling scenarios. There would be a significant advantage to use this approach for the complete modeling of wind turbine blades. A comparison of the traditional composite ply modeling approach and the unit cell approach is studied to determine similarities and differences in the approaches. A panel section is modeled and tested in various conditions followed by correlation and updating studies. A comparison of the different modeling approaches is performed.

Eric Harvey

Papers

Large-area photogrammetry based testing of wind turbine blades

Comparison of Full Field Strain Distributions to Predicted Strain Distributions from Limited Sets of Measured Data for SHM Applications

Simulating the Manufacturing Process and Subsequent Structural Stiffness of Composite Wind Turbine Blades with and without Defects

Dynamic Stress-Strain Prediction from Limited Measurements in the Presence of Structural Defects

Developing a Finite Element Model in Conjunction with Modal Test for Wind Turbine Blade Models