# Gas Foil Bearing Technology Enhanced with Smart Materials
## 3 Solutions for Improving Characteristics of Gas Foil Bearings--An Overview
#### Non-Smart Material Based Solutions--Brief Reference  
Below, a brief overview on the examples of non-smart material-based applications for improving properties of GFBs is provided. * Passive solutions Amongst passive approaches, it is worth mentioning the concept of progressive stiffness of the supporting layer [24]. The main idea of the approach is to assure self  
Figure 3: Thermal management in GFBs applied to enhance the performance of the bearings and prevent the loss of thermal stability. Heat energy source and sink components may be adequately installed to control the heat flow through the GFBs’ body and prevent from undesirable excessive temperature gradients. Figure 2: Scope of structural modifications in GFBs introduced to enhance the elasto-damping properties of the bearings. Various topology, size and geometric changes may be taken into account to improve the performance of GFBs. The modifications may affect both the bushing and specialized foils. Moreover, additional components (also made of smart materials) may be used to achieve an advantageous change in the bearing’s properties. adaptive properties of the bearing in terms of adequate modification of the stiffness of the bump foil undergoing mechanical deformation during GFBs' operation. The authors of the cited work conducted numerical simulations in ABAQUS software, employing a nonlinear model of the GFBs' structure. As shown, the bump foil may exhibit a gradual growth of the contact surface between the shaft's journal and the top foil in a controlled way, with the operational deformation of the structural part of the bearings' supporting layer. In reference, the authors of the presented approach have also investigated the influence of the long-lasting cyclic loading on the geometry of the bump foil in a GFB [16]. A modified shape of the bump foil as well as the concept of a rigid bore segment is presented in [22]. The authors of the work [19] introduce additional structural components, namely the flexure pivot tilting pads being mounted between the bearing's bushing and bump foils. The modification considered allows for effective reduction in the cross-coupled stiffness in the structural part of the supporting layer, that, in turn, leads to the improvement of the bearings performance, including the capability of larger load capacity and smaller nominal clearance. The feasibility of the proposed solution was confirmed using both numerical and experimental results. Another passive solution made use of additional structural components to improve the elasto-damping properties of GFBs is reported in [17]. The referenced work describes the application of metal meshes installed to provide additional supports, i.e., additional bumps, for a top foil. The proposed solution leads to the advantageous increase in damping that improves operational stability of the bearing eventually. The authors also discuss the influence of metal mesh density on the GFBs' performance. The concept of the introduction of bump foil dampers around the bearing sleeve is presented in [23]. As proven using numerical studies, additional components allow for the increase in the bearing's stability. The authors present and discuss the GFBs' load-displacement characteristics to investigate the influence of the damper thickness as well as sleeve mass and material selection on the bearings' operation. Recent work [18] presents an interesting concept of texturing the top foil for a GFB to improve the bearing's characteristics. As experimentally confirmed, the application of a dimple foil advantageously results in speeding up the air film formation process. Moreover, the authors of the referenced work investigated the effect of the texture on the GFBs' temperature growth and resultant friction coefficient under various lubrication conditions. As far as passive thermal management is of concern, it is worth mentioning the idea introduced in publication [36].