Turbopower Program Conference April 14 15 2010 Linkping
Turbopower Program Conference April 14 -15, 2010, Linköping Development and validation of numerical tools for prediction of HCF Salar Sadek, KTH Solid Mechanics 1
Turbo. Vib Synthesis Aeromechanical Analyses AROMA WP 4 2
Why HCF assessment? • • • Important failure mode in turbomachinery Typical requirements: durability, high reliability, light weight and high performance Optimization… design against HCF becomes more important HCF Failure 3
WP 4 – HCF assessment • Develop new models for prediction of HCF • Numerical tools, FE-based • Introduce gradient & volume effects ’’automatically’’ - No use of fatigue factors • Models should include scatter: probabilistic methods 4
HCF design today • • Commercial fatigue Post-Processors: FEMFAT, P·FAT, n. Code, …. . Goodman-like diagrams are also used 5
Our work … Future HCF-design 6
Some concepts • Stress history • The stress history: • Plot contours of • A measure of the loading of the whole structure or more complex to find the ’’hot spots’’ The probability of fatigue is then: 7
ed Some effective stresses • • Criteria • • Fatigue criteria based on stress invariants: Sines or … Matake or Findley or Dang Van or … a component subjected to non proportional stressing. higher. 8
Equivalent stress… VS-plot Structure A Structure B Findley, Sines, Matake, Dang Vang 9
More on our work … • Volume methods: Weakest-link integral • Alternative volume methods are being developed • Volume method together with gradient effect • Development of equivalent stresses (that give loading of a whole component) • Optimize the component to take out the hot spots: More hot spots! 10
Some Research Results Weakest-link integral: Tensile loading with notched cylindrical specimens 11
More Research Results 12
More Research Results VPF: Volume method for the Probability of Fatigue • Threshold stress: • Volume: The probability of fatigue is then: 13
Relation to Turbo. Vib Synthesis • The HCF results in this WP contributes to: • Provide better design guide-lines for turbine blades • Give information in the LAST STEP IN THE DESIGN LOOP • Optimization, which requires good HCF methods HCF assessment Re-design 14
Publications Name Title Type Shahab Teimourimanesh The Effect of Load Sequencing on the Fatigue Life of High Strength Steel MSc thesis (2009) Salar Sadek AN FE-based Fatigue Design Method for a Turbine Cr-Steel – Experiments and Modeling MSc thesis (2009) Andreas Östbring Effects of cycles below the fatigue limit for MSc thesis Ti HCF – Z (2010) Daniel Sandberg Criteria for Fatigue in Gas Turbines Mehdi Basirat Development of a New Volume Method for MSc thesis the Probability of Fatigue (2010) MSc thesis (2010) 15
Planned Research Efforts • Development of fatigue stress: • • Effective stress to evaluate the stress cycle point-wize, Equivalent stress to evaluate the whole structure, Models for probability of HCF failure, Experiments: • • Volume effect vs. gradient effect Competing failure sites Low testing Scatter of fatigue 16
- Slides: 16