Jonas Roemer

The following content refers to the thermal aspects of Gas Foil Bearing (GFB).The GFBs are the subgroup of journal bearings, for which lubrication is provided by air, instead of 'traditional' lubricants like oil, graces etc. Gas Foil Bearings offer specific features unachievable for traditional bearings.GFB can operate with rotating speed up to several dozens of krpm in extreme temperature up to hundreds of Celsius degrees.However due to their specific construction, GFBs are prone to specific thermal issues which complicate their design process.Until now, many tools, mainly based on numerical models were developed.Their effectiveness is evaluated based on experimental data.Due to the high complexity of GFB's structure, the temperature measurement is a challenging task and so far, no reliable simple technique was proposed.There is still a need for developing reliable measurement techniques, allowing for precise temperature measurement.This paper presents the novel approach to temperature measurement of the GFBs compliant structure.The unique concept of foil with integrated sensors was presented and described in detail.

Laser spot thermography (LST) is a sub-domain method in active thermography that uses a laser as the heat source.The method allows for precise control of the beam shape, pulse duration, and delivered energy.Therefore, this technique can be applied, especially for delicate structures where testing conditions must be maintained precisely.The following work includes the introduction of a laser spot thermography technology demonstrator that was designed and constructed at AGH UST.The paper presents laser thermography laboratory experiments along with the developed procedure for automatic defect identification.The measurements were used to establish an automatic procedure and algorithm for automatic defect identification based on regression methods.

Bearings are commonly employed in various types of rotating machineries.Their properties indisputably influence the overall performance and time of maintenance-free operation of the mechanical systems in which they are used to support the shafts.Consequently, much effort is considered to provide reliable bearings' solution and develop new methods and technical tools for measurement and possibly modification of the operational characteristics of the above-mentioned parts.In reference, the concept of a smart bearing is developed as providing the means for real-time passive and active control of the bearings' behavior as well as different types of smart materials are used to enhance their characteristics.The current study deals with an application of structural components made of shape memory alloys to gas foil bearings (GFB).The paper presents and discusses the results of experimental tests conducted for the bearing's prototype to characterize the efficiency of thermally-induced modifications of geometric properties of one of the crucial parts of the investigated GFB.

The paper shows experimental results of fatigue crack detection, performed by laser spot thermography and vibrothermography techniques.The experiments were conducted on aluminium bar with artificially introduced crack.The paper contains theoretical background of both techniques.Also test setups including the control and signal processing software were presented and described.Semi-automatic algorithm for data processing was presented.The algorithm allows for automating measurement procedure, which limits the operator input.The paper shows that both laser spot thermography, as well as, vibrothermography can be effectively used for crack detection in metallic structures.

Essential parts of rotating machineries are supporting nodes, i.e., bearing systems.They assure required rotational degrees of freedom and feature desired load carrying capacity.Following the specificity of a technical solution considered, various types of bearings may be taken into account to effectively address the requirements regarding the speed and load.Specifically, gas foil bearings (GFB) are used in high-speed and lightlyloaded rotating machineries, e.g., auxiliary power units.In fact, they can operate up to several hundreds of thousands rpm, also for a wide temperature range.The current work reports an application of piezoelectric composites to control operation of a GFB.The authors present the developed bearing's prototype installation which is equipped with a specialized multifunctional structural component that advantageously allows to both characterize GFB's operational parameters and modify them.The experimental results confirm the usability of the proposed activelycontrolled configuration of a GFB.