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Journal of Tribology

Published: September 2017

https://doi.org/10.1115/1.4036275 

■  Researchers

Junho Suh

School of Mechanical Engineering, Pusan National University

Alan Palazzolo

Department of Mechanical Engineering, Texas A&M University

Yeon-Sun Choi

Department of Mechanical Engineering, Sungkyunkwan University

■  Abstract

This paper presents a new approach for modeling flexure-pivot journal bearings (FPJB) employing a three-dimensional (3D) elasto-hydro-dynamic (EHD) lubrication model. The finite element (FE) method is adopted for an analysis of the (1) pad-pivot dynamic behavior and the (2) fluid force. The isoviscosity Reynolds equation is utilized to calculate the fluid force acting on a flexure-pivot pad bearing and spinning journal. Computational efficiency is achieved utilizing modal coordinate transformation for the flexible pad-pivot dynamic analysis. Fluid film thickness plays a critical role in the solution of Reynolds equation and is evaluated on a node-by-node basis accounting for the pad and web deflections. The increased fidelity of the novel modeling approach provides rotating machinery designers with a more effective tool to analyze and predict rotor–bearing dynamic behavior.

■  Conclusion

This study presented a new modeling method and algorithm for the evaluation of the static and dynamic characteristics of the flexible pad-pivot FPJB, adopting nonlinear transient dynamic analysis. This study can be summarized as follows:

Modal coordinate transformation is included for calculating the flexible pad-pivot dynamic behavior, in order to increase computational efficiency.

Flexible pad-pivot FE model was simulated and compared to the rigid-pad FPJB, fixed-pad bearing and TPJB with varying web thickness.

Static and dynamic characteristics of the FPJB were simulated with varying number of eigenmodes of the flexible pad-pivot FE model. The fifth bending mode except the first tilting mode, was found to have the biggest influence on the FPJB properties.

Both rigid-pad analytical FPJB and flexible pad-pivot FPJB FE models were simulated with fifteen different web thickness (1–15 mm) converging into the fixed-pad bearing static and dynamic properties. The flexible pad-pivot model produced slower convergence rate with increasing web thickness, which means the conventional approach with the rigid-pad FPJB model will have difficulty in accurately predicting static and dynamic bearing performance.

* 관련 자료 

[신진연구자 인터뷰] 저널 비대칭 가열과 샤프트 열굽힘에 기인 한 회전체 동역학적 불안정성 문제 (Morton effect)