scholarly journals Progressive Damage Modeling of Fiberglass/Epoxy Composites with Manufacturing Induced Waves Common to Wind Turbine Blades

2017 ◽  
Author(s):  
Jared W. Nelson ◽  
Trey W. Riddle ◽  
Douglas S. Cairns
Keyword(s):  
Turbine Blades ◽  
Progressive Damage ◽  
State University ◽  
Damage Modeling ◽  
Wind Turbine Blades ◽  
Worst Case ◽  
Discrete Method ◽  
Manufacturing Defects ◽  
Montana State University ◽  
Insight Into

Abstract. As part of the Blade Reliability Collaborative, the Montana State University Composites Group has investigated the effects of manufacturing defects. To better understand and predict these effects, various progressive damage modeling approaches were investigated. While the use of damage modeling has increased with improved computational capabilities, they are often performed for worst-case scenarios where damage or defects are replaced with notches or holes. To contribute to the establishment of a protocol understanding and quantifying the effects of these defects, a three-round study was performed using continuum, discrete, and combined damage modeling. This approach relied on a systematically comparing consistency, accuracy and predictive capability for each model. These models were constructed to match the coupons from, and compare the results to, the characterization and material testing study. A standard defect case was chosen and initially used for each modeling approach to perform the qualitative and quantitative comparisons. It was found that while each model was able to show certain attributes, the most consistent, accurate, and predictive model was based on a combined continuum/discrete method. Overall, the results indicate that this combined approach may provide insight into blade performance with known defects when used in conjunction with a probabilistic flaw framework.

scholarly journals Probabilistic Design of Wind Turbine Blades with Treatment of Manufacturing Defects as Uncertainty Variables in a Framework

2017 ◽  
Author(s):  
Trey W. Riddle ◽  
Jared W. Nelson ◽  
Douglas S. Cairns
Keyword(s):  
Wind Turbine ◽  
Probabilistic Models ◽  
Low Cost ◽  
Turbine Blades ◽  
Design Parameters ◽  
State University ◽  
Wind Turbine Blades ◽  
Manufacturing Defects ◽  
Montana State University ◽  
Blade Failure

Abstract. Given that wind turbine blades are such large structures, the use of low-cost composite manufacturing processes and materials has been necessary for the industry to be cost competitive. Since these manufacturing methods can lead to inclusion of unwanted defects, potentially reducing blade life, the Blade Reliability Collaborative tasked the Montana State University Composites Group with assessing the effects of these defects. Utilizing the results of characterization and mechanical testing studies, probabilistic models were developed to assess the reliability of a wind blade with known defects. As such, defects were found to best be assessed as design parameters in a parametric probabilistic analysis allowing for establishment of a consistent framework to validate categorization and analysis. Monte Carlo simulations were found to adequately describe the probability of failure of composite blades with included defects. By treating defects as random variables, the approaches utilized indicate the level of conservation used in blade design may be reduced when considering fatigue. In turn, safety factors may be reduced as some of the uncertainty surrounding blade failure is reduced when analysed with application specific data. Overall, the results indicate that characterization of defects and reduction of design uncertainty is possible for wind turbine blades.

scholarly journals Characterization and Mechanical Testing of Manufacturing Defects Common to Composite Wind Turbine Blades

2017 ◽  
Author(s):  
Jared W. Nelson ◽  
Trey W. Riddle ◽  
Douglas S. Cairns
Keyword(s):  
Wind Turbine ◽  
Mechanical Testing ◽  
Mechanical Response ◽  
Turbine Blades ◽  
Analysis Data ◽  
State University ◽  
Wind Turbine Blades ◽  
Manufacturing Defects ◽  
Montana State University ◽  
Damage Models

Abstract. The Montana State University Composites Group performed a study to ascertain the effects of defects that often result from the manufacture of composite wind turbine blades. The first step in this multi-year study was to systematically quantify and database these defects before embedding similar defects into manufactured coupons. Through the Blade Reliability Collaborative, it was determined that the key defects to investigate were fiber waves and porosity. An inspection of failed commercial-scale wind turbine blades yielded metrics that utilize specific parameters to physically characterize a defect. Methods to easily and consistently discretize, measure, and assess these defects based on the identified parameters were established to allow for statistical analysis. Data relating flaw parameters to frequencies of occurrence were analyzed and found to fit within standard distributions. Additionally, mechanical testing of coupons with flaws based on this physical characterization data was performed to understand effects of these defects. Representative blade materials and manufacturing methods were utilized and both material properties and damage progression were measured. It was observed that flaw parameters directly affected the mechanical response. While the data gathered in this first step is widely useful, it was also intended for use as a foundation for the rest of the study; to perform probabilistic analysis and comparative analysis of progressive damage models.

scholarly journals Effects of defects in composite wind turbine blades – Part 1: Characterization and mechanical testing

2017 ◽  
Vol 2 (2) ◽  
pp. 641-652 ◽  
Author(s):  
Jared W. Nelson ◽  
Trey W. Riddle ◽  
Douglas S. Cairns
Keyword(s):  
Wind Turbine ◽  
Mechanical Testing ◽  
Mechanical Response ◽  
Turbine Blades ◽  
Analysis Data ◽  
State University ◽  
Wind Turbine Blades ◽  
Montana State University ◽  
Damage Models ◽  
Commercial Scale

Abstract. The Montana State University Composite Material Technologies Research Group performed a study to ascertain the effects of defects that often result from the manufacture of composite wind turbine blades. The first step in this multiyear study was to systematically quantify and enter these defects into a database before embedding similar defects into manufactured coupons. Through the Sandia National Laboratories Blade Reliability Collaborative (BRC), it was determined that key defects to investigate were fiber waves and porosity. An inspection of failed commercial-scale wind turbine blades yielded metrics that utilized specific parameters to physically characterize a defect. Methods to easily and consistently discretize, measure, and assess these defects based on the identified parameters were established to allow for statistical analysis. Data relating flaw parameters to frequencies of occurrence were analyzed and found to fit within standard distributions. Additionally, mechanical testing of coupons with flaws based on these physical characterization data was performed to understand effects of these defects. Representative blade materials and manufacturing methods were utilized and both material properties and damage progression were measured. It was observed that flaw parameters directly affected the mechanical response. While the data gathered in this first step are widely useful, it was also intended for use as a foundation for the rest of the study, to perform probabilistic analysis and comparative analysis of progressive damage models.

scholarly journals Effects of defects in composite wind turbine blades – Part 3: A framework for treating defects as uncertainty variables for blade analysis

2018 ◽  
Vol 3 (1) ◽  
pp. 107-120 ◽  
Author(s):  
Trey W. Riddle ◽  
Jared W. Nelson ◽  
Douglas S. Cairns
Keyword(s):  
Wind Turbine ◽  
Probabilistic Models ◽  
Low Cost ◽  
Turbine Blades ◽  
Design Parameters ◽  
State University ◽  
Wind Turbine Blades ◽  
Montana State University ◽  
Large Structures ◽  
Blade Failure

Abstract. Given that wind turbine blades are large structures, the use of low-cost composite manufacturing processes and materials has been necessary for the industry to be cost competitive. Since these manufacturing methods can lead to the inclusion of unwanted defects, potentially reducing blade life, the Blade Reliability Collaborative tasked the Montana State University Composites Group with assessing the effects of these defects. Utilizing the results of characterization and mechanical testing studies, probabilistic models were developed to assess the reliability of a wind blade with known defects. As such, defects were found to be best assessed as design parameters in a parametric probabilistic analysis allowing for establishment of a consistent framework to validate categorization and analysis. Monte Carlo simulations were found to adequately describe the probability of failure of composite blades with included defects. By treating defects as random variables, the approaches utilized indicate the level of conservation used in blade design may be reduced when considering fatigue. In turn, safety factors may be reduced as some of the uncertainty surrounding blade failure is reduced when analyzed with application specific data. Overall, the results indicate that characterization of defects and reduction of design uncertainty is possible for wind turbine blades.

scholarly journals Effects of defects in composite wind turbine blades – Part 2: Progressive damage modeling of fiberglass-reinforced epoxy composites with manufacturing-induced waves

2017 ◽  
Vol 2 (2) ◽  
pp. 653-669 ◽  
Author(s):  
Jared W. Nelson ◽  
Trey W. Riddle ◽  
Douglas S. Cairns
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Damage Model ◽  
Peak Stress ◽  
Failure Criteria ◽  
Progressive Damage ◽  
Damage Modeling ◽  
Cohesive Elements ◽  
Wind Turbine Blades ◽  
Nonlinear Shear

Abstract. Composite wind turbine blades are typically reliable; however, premature failures are often in regions of manufacturing defects. While the use of damage modeling has increased with improved computational capabilities, they are often performed for worst-case scenarios in which damage or defects are replaced with notches or holes. To better understand and predict these effects, an effects-of-defects study has been undertaken. As a portion of this study, various progressive damage modeling approaches were investigated to determine if proven modeling capabilities could be adapted to predict damage progression of composite laminates with typical manufacturing flaws commonly found in wind turbine blades. Models were constructed to match the coupons from, and compare the results to, the characterization and material testing study presented as a companion. Modeling methods were chosen from established methodologies and included continuum damage models (linear elastic with Hashin failure criteria, user-defined failure criteria, nonlinear shear criteria), a discrete damage model (cohesive elements), and a combined damage model (nonlinear shear with cohesive elements). A systematic, combined qualitative–quantitative approach was used to compare consistency, accuracy, and predictive capability for each model to responses found experimentally. Results indicated that the Hashin and combined models were best able to predict material response to be within 10 % of the strain at peak stress and within 10 % of the peak stress. In both cases, the correlation was not as accurate as the wave shapes were changed in the model; correlation was still within 20 % in many cases. The other modeling approaches did not correlate well within the comparative framework. Overall, the results indicate that this combined approach may provide insight into blade performance with known defects when used in conjunction with a probabilistic flaw framework.

Damage mitigation techniques in wind turbine blades: A review

2017 ◽  
Vol 41 (3) ◽  
pp. 185-210 ◽  
Author(s):  
Md Abu S Shohag ◽  
Emily C Hammel ◽  
David O Olawale ◽  
Okenwa I Okoli
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Structural Elements ◽  
Variable Loading ◽  
Wind Turbine Blades ◽  
Lightning Strikes ◽  
Manufacturing Defects ◽  
Damage Mitigation ◽  
Mitigation Techniques ◽  
Operational Errors

Wind blades are major structural elements of wind turbines, but they are prone to damage like any other composite component. Blade damage can cause sudden structural failure and the associated costs to repair them are high. Therefore, it is important to identify the causation of damage to prevent defects during the manufacturing phase, transportation, and in operation. Generally, damage in wind blades can arise due to manufacturing defects, precipitation and debris, water ingress, variable loading due to wind, operational errors, lightning strikes, and fire. Early detection and mitigation techniques are required to avoid or reduce damage in costly wind turbine blades. This article provides an extensive review of viable solutions and approaches for damage mitigation in wind turbine blades.

scholarly journals Extending the life of wind turbine blade leading edges by reducing the tip speed during extreme precipitation events

2018 ◽  
Author(s):  
Jakob I. Bech ◽  
Charlotte B. Hasager ◽  
Christian Bak
Keyword(s):  
Wind Turbine ◽  
Extreme Precipitation ◽  
Turbine Blades ◽  
Leading Edge ◽  
Wind Turbine Blades ◽  
Worst Case ◽  
Severe Problem ◽  
Extreme Precipitation Events ◽  
Leading Edges ◽  
The Cost

Abstract. Impact fatigue caused by collision with rain droplets, hail stones and other airborne particles, also known as rain erosion, is a severe problem for wind turbine blades. Each impact on the leading edge adds an increment to the accumulated damage in the material. After a number of impacts the leading edge material will crack. This paper presents and supports the hypothesis that the vast majority of the damage accumulated in the leading edge is imposed at extreme precipitation condition events, which occur during a very small fraction of the turbines operation life. By reducing the tip speed of the blades during these events, the service life of the leading edges significantly increases from a few years to the full expected lifetime of the wind turbine. In the worst case at the cost of a negligible reduction of annual energy production (AEP) and in the best case with a significant increase in AEP.

THE RELATIVE IMPORTANCE OF STRENGTH AND WEIGHT IN PROCESSING NEW INFORMATION IN THE COLLEGE FOOTBALL BETTING MARKET

2012 ◽  
Vol 2 (2) ◽  
pp. 13-28
Author(s):  
Greg Durham ◽  
Mukunthan Santhanakrishnan
Keyword(s):  
San Antonio ◽  
College Football ◽  
Price Formation ◽  
Relative Importance ◽  
State University ◽  
Montana State University ◽  
New Information ◽  
Betting Market ◽  
Football Betting ◽  
Insight Into

Griffin and Tversky (1992) suggest that individuals, when formulating posterior probabilities based on the available evidence, tend to overreact to a new piece of evidence’s strength while underreacting to the relative importance of its weight.  We test this prediction using the college football betting market, a market that is commonly employed in tests for efficiency and rationality.  Using average points in excess of the spread and streak against the spread as measures for strength and weight, respectively, we find that bettors overreact to strength and underreact to weight.  These results are consistent with the predictions of Griffin and Tversky, as well as with the findings of Sorescu and Subrahmanyam (2006) and Barberis, Shleifer, and Vishny (1998) in financial market settings.  Our work also provides insight into how behavioral biases might affect price-formation processes in other markets.The authors thank Tod Perry, Omar Shehryar, and Kumar Venkataraman for their careful feedback and thoughtful suggestions.  The authors are also grateful for comments from seminar participants at the 2008 Midwest Finance Association meetings in San Antonio and 2008 Southwestern Finance Association meetings in Houston, as well as from seminar participants at Montana State University.  (The authors are responsible for any outstanding errors in this paper.)

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