NDLI: Simplified Forced Response HCF Assessment of Turbomachinery Blades

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Ma˚rtensson, Hans Forsman, Johan Eriksson, Martin
Copyright Year	2009
Abstract	A method is proposed for HCF-analysis that is suitable for use in early design stages of turbomachinery blades. Quantitative measures of the risk for later encountering HCF life limiting vibrations are the goal for the development. The novelty of the system is the unique and rational way all design data are processed resulting in a mode risk priority listing. The method makes extensive use of FE calculated modal analyses and simple assumptions on the modal force and damping. The modal force is taken proportional to the tangential force on the blade over the operating range. This choice is made because the tangential force is known early on from the compressor performance map, and gives a reasonable scaling with the operating point. Crossings occurring at low speed get a lower force than at high speed. The system damping used is a constant critical damping ratio. Using a modal force and damping along with the FE model forced response amplitude can be directly computed at resonance crossings inside operating envelope. The modal force calculated this way can be compared to the force amplitude needed to reach the fatigue limit in a Haigh diagram. Using the Haigh diagram this way allows modes with localized high stresses, so-called hot spots, to be highlighted. Taking the ratio of the forces gives a ranking value that can be used to compare risk. Details of the technique along with example applications to compressor blades are presented in the paper. It is found that many mode crossings can be excluded as low risk this way and that a rational way of prioritizing is achieved.
Sponsorship	International Gas Turbine Institute
Starting Page	477
Ending Page	486
Page Count	10
File Format	PDF
ISBN	9780791848876
DOI	10.1115/GT2009-60166
e-ISBN	9780791838495
Volume Number	Volume 6: Structures and Dynamics, Parts A and B
Conference Proceedings	ASME Turbo Expo 2009: Power for Land, Sea, and Air
Language	English
Publisher Date	2009-06-08
Publisher Place	Orlando, Florida, USA
Access Restriction	Subscribed
Subject Keyword	Damping Vibration Blades Modal analysis High cycle fatigue Turbomachinery Risk Compressors Fatigue limit Stress Design Finite element model Resonance
Content Type	Text
Resource Type	Article

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