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Tool for Blade Stress Estimation during Multiple Simultaneous Vibratory Mode Responses


TECHNOLOGY AREAS: Air Platform, Space Platforms

OBJECTIVE:  Develop a computational toolkit to estimate the stresses in rotating blades and other structures due to multiple structural vibratory modes.

DESCRIPTION:  Turbine engine stress estimation is necessary during engine stress survey testing. Newer modern turbine engines with integrally bladed rotors (IBR) tend to have a higher number of blade vibratory modes excited by unsteady flows associated with IGVs, stators, distortion, etc.  This results many times in multiple structural vibratory blade modes being excited simultaneously, therefore, making it difficult to estimate actual blade maximum stress using existing methods that model only single vibratory modes.  A need exists for a method to extract component critical stress limits for complex multi-mode stress states from simple modal limits provided by the manufacturer.  In addition, a method is needed that would identify critical stresses from a combination of relatively benign individual modal peaks to guide test program planning and life estimation programs.

PHASE I:  The theory will be developed to determine the stresses in a structure while multiple vibratory modes are excited.  In addition, the architecture for a program to determine the maximum stresses and present results to the user will also be developed.

PHASE II:  A software package will be developed utilizing the theory developed in Phase I to estimate blade stresses under all of the possible mode combinations.  The software shall automatically search for & determine those combinations that produce the greatest stresses & present them in an actionable manner.  In particular, the location & stress amplitude of the maximum stress for a variety of blade geometries & modal combinations shall be presented.


Military Application:  This code will be used extensively in the analysis of turbine engine blade stresses for both ground test programs and in support of flight testing and operations.

Commercial Application:  The software could be used to estimate stresses in other rotating systems such as industrial steam and wind turbines, fans, and other components.

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