Investigation of Foil Journal Bearing Performance by Generalized Differential Quadrature (GDQ) Method M. Mehdizadeh 1 , B. Hajshirmohammadi 1 , A. Ghobadi 2 , M. Esfahanian 3 1 Department of Mechanical and Industrial Engineering, Louisiana State University, USA 2 Department of Mechanical Engineering, Islamic Azad University of Khomeini-Shahr, Iran 3 Department of mechanical engineering, Isfahan University of Technology, Isfahan, Iran INTRODUCTION Many research has been conducted on wear mechanisms and tribology behavior of materials and components such as gear, bearings, etc [1-3]. Compliant journal bearings popularly known as foil bearings have gained significant attention in recent years because of their unique mode of operation and diversity of applications. These types of bearings have various advantages compared to the conventional rigid journal bearings in terms of higher load carrying capacity, lower power loss, better stability and greater endurance. These bearings are self-acting, and can operate with ambient air or any process gas as the lubricating fluid. The need for complex lubrication systems is eliminated, which result in significant weight reduction and lower maintenance. Air as a lubricant is available abundantly and can operate at elevated temperatures whereas conventional oil-based lubricants fail since their viscosity drops exponentially with the rise in temperature. Figure (1) represents the configuration of a foil journal bearing. It is comprised of an outer bearing sleeve which houses the corrugated series of bumps on a thin foil strip and over the bump foil strip a thin smooth top foil sheet is laid. These foils are welded at leading edge and are free at the trailing edge. Fig. 1 Schematic of Compliant Journal Bearing The series of bumps in the strip supports the top foil sheet and acts as a spring bed which makes the bearing compliant (Fig 2). The journal and bearing system are supported by a thin lubricant film (gas) due to the hydrodynamic pressure Distribution. Fig. 2 Schematic Configuration of Top and Bump Foils Blok and VanRossum (1953) first introduced the technical community to foil bearings and investigated a tension type CFB with analytical and experimental method [4]. Foil air bearings were first commercialized in the 1970s in air cycle machines used for