scholarly journals Time-Lapse Helical X-ray Computed Tomography (CT) Study of Tensile Fatigue Damage Formation in Composites for Wind Turbine Blades

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2340 ◽  
Author(s):  
Ying Wang ◽  
Lars Mikkelsen ◽  
Grzegorz Pyka ◽  
Philip Withers
Keyword(s):  
Computed Tomography ◽  
Wind Turbine ◽  
Fatigue Damage ◽  
Turbine Blades ◽  
Time Lapse ◽  
Ex Situ ◽  
Wind Turbine Blades ◽  
Damage Mechanisms ◽  
X Ray ◽  
X Ray Computed

Understanding the fatigue damage mechanisms in composite materials is of great importance in the wind turbine industry because of the very large number of loading cycles rotor blades undergo during their service life. In this paper, the fatigue damage mechanisms of a non-crimp unidirectional (UD) glass fibre reinforced polymer (GFRP) used in wind turbine blades are characterised by time-lapse ex-situ helical X-ray computed tomography (CT) at different stages through its fatigue life. Our observations validate the hypothesis that off-axis cracking in secondary oriented fibre bundles, the so-called backing bundles, are directly related to fibre fractures in the UD bundles. Using helical X-ray CT we are able to follow the fatigue damage evolution in the composite over a length of 20 mm in the UD fibre direction using a voxel size of (2.75 µm)3. A staining approach was used to enhance the detectability of the narrow off-axis matrix and interface cracks, partly closed fibre fractures and thin longitudinal splits. Instead of being evenly distributed, fibre fractures in the UD bundles nucleate and propagate locally where backing bundles cross-over, or where stitching threads cross-over. In addition, UD fibre fractures can also be initiated by the presence of extensive debonding and longitudinal splitting, which were found to develop from debonding of the stitching threads near surface. The splits lower the lateral constraint of the originally closely packed UD fibres, which could potentially make the composite susceptible to compressive loads as well as the environment in service. The results here indicate that further research into the better design of the positioning of stitching threads, and backing fibre cross-over regions is required, as well as new approaches to control the positions of UD fibres.

scholarly journals A Staged Approach to Erosion Analysis of Wind Turbine Blade Coatings

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 681
Author(s):  
David Nash ◽  
Grant Leishman ◽  
Cameron Mackie ◽  
Kirsten Dyer ◽  
Liu Yang
Keyword(s):  
Computed Tomography ◽  
Wind Turbine ◽  
Incubation Period ◽  
Leading Edge ◽  
X Ray ◽  
Erosion Testing ◽  
Staged Approach ◽  
X Ray Computed ◽  
Droplet Impacts ◽  
Rain Erosion

The current wind turbine leading-edge erosion research focuses on the end of the incubation period and breakthrough when analysing the erosion mechanism. This work presented here shows the benefits of splitting and describing leading-edge erosion progression into discrete stages. The five identified stages are: (1) an undamaged, as-new, sample; (2) between the undamaged sample and end of incubation; (3) the end of incubation period; (4) between the end of incubation and breakthrough, and (5) breakthrough. Mass loss, microscopy and X-ray computed tomography were investigated at each of the five stages. From this analysis, it was observed that notable changes were detected at Stages 2 and 4, which are not usually considered separately. The staged approach to rain erosion testing offers a more thorough understanding of how the coating system changes and ultimately fails due to rain droplet impacts. It is observed that during microscopy and X-ray computed tomography, changes unobservable to the naked eye can be tracked using the staged approach.

scholarly journals A study of the progression of damage in an axially loaded Branta leucopsis femur using X-ray computed tomography and digital image correlation

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3416 ◽  
Author(s):  
Zartasha Mustansar ◽  
Samuel A. McDonald ◽  
William Irvin Sellers ◽  
Phillip Lars Manning ◽  
Tristan Lowe ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Time Lapse ◽  
Image Correlation ◽  
Long Bone ◽  
Barnacle Goose ◽  
3D Images ◽  
X Ray ◽  
X Ray Computed

This paper uses X-ray computed tomography to track the mechanical response of a vertebrate (Barnacle goose) long bone subjected to an axial compressive load, which is increased gradually until failure. A loading rig was mounted in an X-ray computed tomography system so that a time-lapse sequence of three-dimensional (3D) images of the bone’s internal (cancellous or trabecular) structure could be recorded during loading. Five distinct types of deformation mechanism were observed in the cancellous part of the bone. These were (i) cracking, (ii) thinning (iii) tearing of cell walls and struts, (iv) notch formation, (v) necking and (vi) buckling. The results highlight that bone experiences brittle (notch formation and cracking), ductile (thinning, tearing and necking) and elastic (buckling) modes of deformation. Progressive deformation, leading to cracking was studied in detail using digital image correlation. The resulting strain maps were consistent with mechanisms occurring at a finer-length scale. This paper is the first to capture time-lapse 3D images of a whole long bone subject to loading until failure. The results serve as a unique reference for researchers interested in how bone responds to loading. For those using computer modelling, the study not only provides qualitative information for verification and validation of their simulations but also highlights that constitutive models for bone need to take into account a number of different deformation mechanisms.

Design and Fatigue Performance of Large Utility-Scale Wind Turbine Blades

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Peter K. Fossum ◽  
Lars Frøyd ◽  
Ole G. Dahlhaug
Keyword(s):  
Wind Turbine ◽  
Fatigue Damage ◽  
Turbine Blades ◽  
Fiber Material ◽  
Fatigue Performance ◽  
Wind Turbine Blades ◽  
Additional Material ◽  
Turbulent Wind ◽  
Fatigue Damage Accumulation ◽  
Utility Scale

Aeroelastic design and fatigue analysis of large utility-scale wind turbine blades have been performed to investigate the applicability of different types of materials in a fatigue environment. The blade designs used in the study are developed according to an iterative numerical design process for realistic wind turbine blades, and the software tool FAST is used for advanced aero-servo-elastic simulations. Elementary beam theory is used to calculate strain time series from these simulations, and the material fatigue is evaluated using established methods. Following wind turbine design standards, the fatigue evaluation is based on a turbulent wind load case. Fatigue damage is estimated based on 100% availability and a site-specific annual wind distribution. Rainflow cycle counting and Miner's sum for cumulative damage prediction is used together with constant life diagrams tailored to actual material S-N data. Material properties are based on 95% survival probability, 95% confidence level, and additional material safety factors to maintain conservative results. Fatigue performance is first evaluated for a baseline blade design of the 10 MW NOWITECH reference wind turbine. Results show that blade damage is dominated by tensile stresses due to poorer tensile fatigue characteristics of the shell glass fiber material. The interaction between turbulent wind and gravitational fluctuations is demonstrated to greatly influence the damage. The need for relevant S-N data to reliably predict fatigue damage accumulation and to avoid nonconservative conclusions is demonstrated. State-of-art wind turbine blade trends are discussed and different design varieties of the baseline blade are analyzed in a parametric study focusing on fatigue performance and material costs. It is observed that higher performance material is more favorable in the spar-cap construction of large blades which are designed for lower wind speeds.

scholarly journals Capabilities to Assess Health/Maintenance Status of Gas Turbine Blades with Non-Destructive Methods

2015 ◽  
Vol 21 (4) ◽  
pp. 41-47 ◽  
Author(s):  
Józef Błachnio
Keyword(s):  
Computed Tomography ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Health Maintenance ◽  
Visual Method ◽  
X Ray ◽  
Active Thermography ◽  
X Ray Computed ◽  
Non Destructive ◽  
Destructive Methods

Abstract The paper has been intended to discuss non-destructive testing methods and to present capabilities of applying them to diagnose objectively changes in the microstructure of a turbine blade with computer software engaged to assist with the analyses. The following techniques are discussed: a visual method, based on the processing of images of the material surface in visible light, active thermography, based on the detection of infrared radiation, and the X-ray computed tomography. All these are new non-destructive methods of assessing technical condition of structural components of machines. They have been intensively developed at research centers worldwide, and in Poland. The computer-aided visual method of analyzing images enables diagnosis of the condition of turbine blades, without the necessity of dismantling of the turbine. On the other hand, the active thermography and the X-ray computed tomography, although more sensitive and more reliable, can both be used with the blades dismounted from the turbine. If applied in a complex way, the non-destructive methods presented in this paper, are expected to increase significantly probability of detecting changes in the blade's condition, which in turn would be advantageous to reliability and safety of gas turbine service.

Sign in / Sign up

Export Citation Format

Share Document