A rough surface contact model for anisotropically elastic materials

2008 ◽  
Vol 222 (3) ◽  
pp. 261-270
Author(s):  
U Scholz ◽  
D Bartel ◽  
L Deters
Keyword(s):  
Rough Surface ◽  
Contact Model ◽  
Elastic Materials ◽  
Surface Contact ◽  
Rough Surface Contact

Rough Surface Contact of Curved Conformal Surfaces: An Application to Rotor–Stator Rub

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Philip Varney ◽  
Itzhak Green
Keyword(s):  
Rough Surface ◽  
Contact Force ◽  
Contact Stiffness ◽  
Point Contact ◽  
Contact Model ◽  
Industrial Society ◽  
Real Surface ◽  
Linear Elastic ◽  
Surface Contact ◽  
Rough Surface Contact

Rotating machines and associated triboelements are ubiquitous in industrial society, playing a central role in power generation, transportation, and manufacturing. Unfortunately, these systems are susceptible to undesirable contact (i.e., rub) between the rotor and stator, which is both costly and dangerous. These adverse effects can be alleviated by properly applying accurate real-time diagnostics. The first step toward accurate diagnostics is developing rotor–stator rub models which appropriately emulate reality. Previous rotor–stator rub models disavow the contact physics by reducing the problem to a single esoteric linear contact stiffness occurring only at the point of maximum rotor radial deflection. Further, the contact stiffness is typically chosen arbitrarily, and as such provides no additional insight into the contacting surfaces. Here, a novel rotor–stator rub model is developed by treating the strongly conformal curved surfaces according to their actual nature: a collection of stochastically distributed asperities. Such an approach is advantageous in that it relies on real surface measurements to quantify the contact force rather than a heuristic choice of linear contact stiffness. Specifically, the elastoplastic Jackson–Green (JG) rough surface contact model is used to obtain the quasistatic contact force versus rotor radial deflection; differences and similarities in contact force between the linear elastic contact model (LECM) and JG model are discussed. Furthermore, the linear elastic model's point contact assumption is assessed and found to be inaccurate for systems with small clearances. Finally, to aid in computational efficiency in future rotordynamic simulation, a simple exponential curve fit is proposed to approximate the JG force–displacement relationship.

Rotordynamic Analysis of Rotor–Stator Rub Using Rough Surface Contact

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Philip Varney ◽  
Itzhak Green
Keyword(s):  
Rough Surface ◽  
Contact Force ◽  
Bulk Material ◽  
Contact Stiffness ◽  
Contact Model ◽  
Real Surface ◽  
Time Step ◽  
Surface Contact ◽  
Orbit Analysis ◽  
Rough Surface Contact

Undesirable rotor–stator rub is frequently observed in rotordynamic systems, and has been the subject of many investigations. Most of these studies employ a simple piecewise-smooth linear-elastic contact model (LECM), where the rotor switches between noncontacting and contacting operation once the clearance is exceeded (various complications have been incorporated, though the essential model premises endure). Though useful as a first step, the LECM relies on an arcane contact stiffness estimate, and therefore does not emulate the actual contacting surfaces. Consequentially, the LECM fails to elucidate how real surface parameters influence contact severity and surface durability. This work develops a novel model for rotor–stator rub which is commensurate with reality by treating the surfaces as a collection of stochastically distributed asperities. Specifically, the elastoplastic Jackson–Green (JG) rough surface contact model is used to calculate the quasistatic contact force as a function of rotor displacement, where bulk material deformation and surface cumulative damage are ignored. A simple exponential fit of the contact force is proposed to reduce computational burden associated with evaluating the JG rough surface contact model at each simulation time step. The rotor's response using the LECM and JG rough surface contact model is compared via shaft speed bifurcations and orbit analysis. Significant differences are observed between the models, though some similarities exist for responses with few contacts per rotor revolution.

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