AROMA 2.0 Structural Damping – Influence of Variable Normal Load on Friction Damping Mohammad Afzal, KTH Sound and Vibration MWL TURBO POWER Program Conference 2014

WP4 HCF Life WP2 Aerodynamic Damping and Forcing WP2 WP3 WP4 X WP1 Synthesis WP3 Structural Damping AROMA 2.0

This Talk Friction damping: Reduction in vibration amplitude! 3 Variable component of normal contact force has significant influence on damping at low contact force.

Interface in AROMA2.0 4 WP1: FE Model of linear component + Reduce order model WP2: Aerodynamic forces WP3: Contact interface description and parameters + Contact interface element Amplitude of displacement + Contact stiffness matrix WP3: Non- linear solver

Non-Linear Solver 5 Motion of adjacent surface Interaction forces Contact stiffness matrix Solution of linearized equation using Newton -Raphson method Expression are obtained analyticallyExact + Fast Non-Linear DOF Linearization of equation using HBM

Friction Damping Parameters 6 N Other Parameters: Friction coefficient Normal contact stiffness Tangential contact stiffness 1D & 2D tangential relative displacement Contact interface discretization …………

7 Constant Vs Variable Normal Load 1. Constant Normal Load 2. Variable Normal Load Note: It complicates the contact stiffness matrix & increase the computation time.

Numerical Test Case 8 Contact stiffness matrix, depends on X(t),N……… Equation of Motion: Time domain Frequency domain Need iterative solution

Response low contact load 9

Response medium contact load 10

Response high contact load 11

Results Variable component of normal contact force has huge influence on friction damping effectiveness for low normal load. At very low value of normal contact force there is possibility of separation hence reduction in effective damping. Implemented solution method shown to be robust and computationally efficient 12

Challenge in Friction Damping 13 Determination of normal & tangential stiffness, also depends on mode shapes. Exact value of friction coefficient Knowledge of contact type (Point, Line or Surface) Allowing for dependence on operating condition: temperature, wear, oxidation….

Reduce blade high cycle stress 14 Accurate prediction of reduction in amplitude Potential to reduce the amplitude by 50% Key contributor towards novel and innovative bladed disk design solutions for improved efficiency.

List of diploma works and publications 15 Name (Main author)TitleType PHILLIPPE JonathanParametric characterization of friction damping behavior and performance in inter-lock shrouded blades in low pressure power turbine application MSc Thesis (2012) Jia SunVibration Characteristics and Structural Damping of Rotating Compressor Blades Doctoral Thesis (2012) Jia SunA dynamic rotating blade model based on plate theory via Hamilton’s principle Journal of sound and vibration (2011) Jia SunNUMERICAL MODELING OF ROTATING COMPRESSOR BLADE WITH ARBITRARY STAGGER ANGLE 23rd NSCM (2010) Jia SunCOATING METHODS TO INCREASE MATERIAL DAMPING OF COMPRESSOR BLADES – MEASUREMENTS AND MODELING ASME Paper (2010) Jia SunDEVELOPMENT OF A DYNAMIC ROTATING TURBINE BLADE MODEL 16th ICSV (2009) Meng TianExperimental Investigation of Damping LayerMSc thesis (2009) Jia SunRotating structure modeling and damping measurementsLic Thesis (2011) Jia SunPrediction and Measurements of Structural Damping of Compressor Blades Treated by Different Damping Materials 20th ISABE (2011) Jia SunTransient Analysis of A Straight Blade with Arbitrary Stagger Angle under High Rotation Speed Internoise 2011 (2011)