Vibration Responses of a Coaxial Dual-Rotor System with Supporting Misalignment

In order to improve the thrust-weight ratio, modern aeroengines generally adopt a coaxial dual-rotor system. Factors such as manufacturing errors, assembly errors, bearing wear, and structural deformation can cause misalignment failures in a dual-rotor system. Supporting misalignment is one of the common types of misalignments in a dual-rotor system. To analyze the vibration characteristics of misalignment faults, in this study, we aim to build a finite element model of a dual-rotor system with supporting misalignment. The bearing loads caused by supporting misalignment are calculated using the three-bending moment equation method. Bearing loads are introduced into the dynamic model of the dual-rotor system. The influence of supporting misalignment at different bearings on the dynamic characteristics of the rotor system is investigated based on the supporting misalignment model. Studies have shown that supporting misalignment at different bearings has similar effects on the dynamic characteristics of the dual-rotor system. The proposed supporting misalignment model is more adaptable than the coupling misalignment model. It indicates that the damping of a rolling bearing should be considered in the dynamic analysis of a dual-rotor system although the value of the damping is not large. An experimental analysis is carried out. The simulation results are in good agreement with the experimental results.

Design of a Low-Loss, Low-Cost Rolling Element Bearing System for a 5 kWh/100 kW Flywheel Energy Storage System

The bearings of a flywheel energy storage system (FESS) are critical machine elements, as they determine several important properties such as self-discharge, service life, maintenance intervals and most importantly cost. This paper describes the design of a low-cost, low-loss bearing system for a 5 kWh/100 kW FESS based on analytical, numerical and experimental methods. The special operating conditions of the FESS rotor (e.g., high rotational speeds, high rotor mass, vacuum) do not allow isolated consideration of the bearings alone, but require a systematic approach, taking into account aspects of rotor dynamics, thermal management, bearing loads and lubrication. The proposed design incorporates measures to mitigate both axial and radial bearing loads, by deploying resilient bearing seats and a lifting magnet for rotor weight compensation. As a consequence of minimized external loading, bearing kinematics also need to be considered during the design process. A generally valid, well-structured guideline for the design of such low-loss rolling bearing systems is presented and applied to the 5 kWh/100 kW FESS use case.

Mechanical properties of the surface membrane of lattice spacer-fabric flexible inflatable composites

The surface membrane plays a vital role in bearing loads of flexible inflatable composites. In this work, the mechanical properties of the upper and lower surfaces of inflatable composites and spacer fabrics were studied. It focused on the changes in mechanical properties of surfaces of spacer fabrics with different structures after coating and damage characteristics. The results show that the PVC resin improves the mechanical properties of the surface, which penetrates into the structure to make the yarns bond to each other and adhere to the resin on the surface. And compared with knitted structures, composite membranes with a woven structure have the characteristics of specific strength. This provides data accumulation for performance research of flexible inflatable composites, finite element calculation analysis, and the experimental reference for broadening the application in military pontoons and marching tents.

Dynamic Influence of Wheel Flat on Fatigue Life of the Traction Motor Bearing in Vibration Environment of a Locomotive

Wheel flat can cause a large impact between the wheel and rail and excites a forced vibration in the locomotive and track structure systems. The working conditions and fatigue life of the motor bearings are significantly affected by the intensified wheel–rail interaction via the transmission path of the gear mesh. In this study, a fatigue life prediction method of the traction motor bearings in a locomotive is proposed. Based on the L−P theory or ISO 281 combined with the Miner linear damage theory and vehicle–track coupled dynamics, the irregular loads induced by the track random irregularity and gear mesh are considered in this proposed method. It can greatly increase the accuracy of predictions compared with the traditional prediction models of a rolling bearing life whose bearing loads are assumed to be constant. The results indicate that the periodic impact forces and larger mesh forces caused by the wheel flat will reduce the fatigue life of the motor bearings, especially when the flat length is larger than 30 mm. Using this method, the effects of the flat length and relatively constant velocity of the locomotive are analyzed. The proposed method can provide a theoretical basis to guarantee safe and reliable working for motor bearings.

Design and Production of a New Smaller Diameter Axial Bearing Subjected to High Wear Loads

In the steering system of a passenger car, one of the essential components is the tie rod, and the sub-assembly component is the inner tie rod, which is subject to static and dynamic bearing loads. These bearing loads are the key points to ensure the inner tie rod's performance and total lifetime. A significant drop in the inner tie rod's performance can cause uncomfortable driving conditions and noise during driving. Most of the designs are developed over-safe with bigger ball sizes to fulfill the defined requirements. On the other hand, over-safe design can cause higher prices. In this study, a new small diameter axial bearing system is developed subjected to high wear loads on the inner tie rod. Three design parameters are considered: press force, tempering method, and tempering temperature. A smaller ball diameter design is created during the development phase. After the manufacturing, the inner tie rods are tested concerning the wear test and setting behavior under the maximum loading test. Results have been compared with a bigger ball size design. By changing the production and assembly parameters, optimum assembly conditions have been defined. Functional measurements before and after testing have validated the new smaller ball diameter design for serial usage.

Penetration and uplift resistances of two interfering pipelines buried in clays

The primary aim of this paper is to determine penetration and uplift resistances of two interfering pipelines buried in clay with a linear increase in strength. The advanced finite element limit analysis of upper and lower bound theorems is used to perform new limit analysis solutions for both penetration and uplift resistances of two interfering pipelines. The strength profiles of cohesive soils are the cases of normally consolidated clays in deep water by setting the shear strength at the ground surface to be zero and linearly increased with the depth. The twin pipelines have the same geometries and are simultaneously failed at the same magnitude of the failure uplift or bearing loads. There are three considered input parameters including the spacing between the pipes, the embedded depth of the pipes, and the unit weight of soils. All input parameters have significant influences on the penetration and uplift resistances of two interfering pipelines. Failure mechanisms of the problems are also investigated, and stability charts of the penetration and uplift resistances of two interfering pipelines are produced for practical uses in offshore geotechnical engineering.

DESIGN OF AND WITH SENSING MACHINE ELEMENTS - USING THE EXAMPLE OF A SENSING ROLLING BEARING

In this paper the development process of a sensing rolling bearing is presented, from which finally design rules for sensing machine elements are derived. In the first step, the requirements of the users are determined. It turns out user of sensing machine elements want to continue to use the advantage of the standardized machine elements and costs should not be incurred by redesign or complex assembly. With these requirements the development of the sensing rolling bearing is started, in which the different presented technologies are reviewed for their suitability regarding the requirements. With the selected technology measuring the electric rolling bearing impedance to estimate rolling bearing loads, a first prototype is developed by creating a functional structure of the product and focusing on the partial solution of the most relevant partial functions. This prototype is then tested with regard to its functionality. Finally, generalizable design rules for sensing machine elements are derived from the development.