Assembly process designers typically confront the challenge of seeking information out of large volumes of non-structured files with a view to supporting the decision-making to be made. It is a leading concern that embedding data in text documents can hardly be retrieved semantically in order to facilitate decision-making with timely support. For tackling this gap, we propose in this paper a knowledge graph-based approach used to merge and retrieve information decided to be relevant within an engineering context. The proposed approach is to establish a multidimensional integrated assembly resource knowledge graph (ARKG) based on the structure of function-structure-assembly procedure-assembly resource, and this multidimensional integrated structure can well accomplish the retrieval of related knowledge. The upper semantic framework of ARKG is established by the assembly resource ontology model, which is a semantic-type framework involving multiple domains of knowledge to create instantiated data reflecting the full profile of the assembly resource for obtaining structured data of ARKG while avoiding the data redundancy problem. The ARKG method is validated through assembly scenario of the aircraft, and the results show the effectiveness and accuracy of the ARKG used by the assembly process designer in the assembly process design phase for retrieving the target knowledge of the assembly resources.

Although bearings have been used in many rotating machineries, the literatures relative to matched bearings are very scarce. The distributions of contact load and contact angle between bearing parts are the key indicators to reflect the operating condition of bearings, which can directly influence the wear rate and fatigue life of bearings. Owing to the complex and compact structure of matched bearings, it is hard to judge and evaluate what happens inside the matched bearings by experiments. To solve this problem, this paper presents a novel method to determine the distributions of contact load and contact angle of matched bearings under complex working conditions. Firstly, to establish the nonlinear relationship between internal deformations of balls and applied loads, a comprehensive model is proposed by using the coordinate transformation method and the Hertz contact theory. Then, the accuracy of the proposed model is validated by comparing the stiffness values with those reported in the existing reference. Finally, a pair of 7206B bearings is used as a case to introduce the use of the proposed model. The influences of installation type, preload, combined loads on the distributions of contact load and contact angle of matched bearings are detailed analyzed and studied.

Wear of rolling elements can produce a huge impact on the mechanical properties of screw-nut joint, and is one of primary causes resulting in the accuracy degradation or even failure of kinematic pairs. Many mechanical models have been constructed to investigate the vibration performance of rolling elements. But the wear influence is considered scarcely because of the complicacy of loading status and wear process. In this study, a novel wear prediction model can be proposed for screw-nut joint to overcome the above difficulty. An ultimate stiffness model can be constructed on basis of the wear model. The influences of running distance, external forces, preload, and structural parameters on wear performance are researched. A dynamic model of screw-nut joint with varying stiffness is constructed to carry out a detailed study on its vibration performance, particularly taking into account the coupling effect between wear and vibration. The influences of wear on the axial stiffness and vibration characteristics are studied based on the proposed model. Moreover, the change rules of axial stiffness and dynamic response under variable preloads are researched. The results indicate that the choice of parameters can produce an appreciable impact on the wear rate. The wear can result in the losses of stiffness and critical displacement of screw-nut joint. Although increasing the preload can improve the stiffness and the critical displacement, it also aggravates the wear degree. When the relative displacement between nut and screw is greater than the critical displacement, the balls with preload and axial force in opposite directions will be out of action, and the monotonic property of stiffness will also change. Due to the monotonicity of stiffness is not consistent before and after the critical displacement point, the amplitude-frequency curve presents a jumping phenomenon.

In engineering practice, bearings used as support components are usually installed in pairs in various rotating machines. The mechanical and contact characteristics of bearings play a crucial role in determining the operational accuracy, safety performance and stability of equipment. Numerous studies focused on single bearings have been reported form diffident aspects for enhancing service performance. However, the literature reports on the matched bearings are scarce due to the mutual coupling of rolling elements and the extremely complex stress conditions. Especially the stiffness fluctuation and internal contact status affected by the ball position are difficult to be observed and tested experimentally because of the complex and compact structure, which significantly impacts the safe and reliable operation of rotating machines. To overcome the above shortcomings, this paper investigates the effect of ball position on the stiffness characteristics and contact status of matched angular contact ball bearings based on the coordinate matrix transformation approach and Jones’ statics model. Then, the stiffness results of published literature are used as a benchmark to validate the accuracy of solution method of this paper. Finally, 7206B bearings with different installing forms are used as a numerical example to reveal the effect of ball position on the stiffness characteristics and contact status of matched angular contact ball bearings under different working conditions. The study provides a scientific guidance to investigate the mechanical characteristics and contact mechanism of multi-bearing system.