001 Study of Bolted Joints with Threaded Inserts

Job title:

001 Study of Bolted Joints with Threaded Inserts

Company:

Centre National d’Etudes Spatiales

Job description

Space activities play a critical role in a variety of fields, including understanding of the universe, life and earth sciences, mobility, telecommunications and defense. As a result, it is essential to design space equipment that combines power and lightness, in order to improve performance while reducing fossil fuel consumption and launch costs. The miniaturization of satellites is part of this approach by decreasing equipment mass. However, designing a high-performance, lightweight spacecraft (weighting less than 200kg) remains a challenge in terms of propulsion and structures.Innovation is therefore focused on all components, in particular the numerous threaded connections used in space systems. These connections are designed to withstand complex mechanical and vibratory stresses, in an extreme environmental condition. Controlling stress transfer between components is a critical issue during system design, especially for threaded connections and their service life. These connections are found throughout the satellite and launchers. Structural parts use standard-size screws, while small-diameter screws are employed in on-board systems, electronic cards and microsatellites. These small screws, with a maximum diameter of 4mm, are more challenging to characterize because of their size.This project aims to contribute to the lightening of space equipment to promote sustainable space activities by improving the mechanical strength of assemblies. It is proposed to use threaded insert technology to reinforce threaded holes in soft materials, such as aluminium, which is highly valued for reducing system mass. Although this is a crucial challenge for the space industry, there are few scientific publications on threaded inserts. The highly non-linear behavior of the insert assembly is still not fully understood, particularly in the case of non-conformities. Manufacturing or installation defects in the insert can lead to the failure of the assembly. Numerous uncertainties exist regarding the mechanical behavior, which is influenced by complex physical phenomena and leads to the oversizing of these connections, counteracting mass reduction strategies.An initial study was carried out during an internship at ICA, which concluded in August 2024. The results obtained are relevant and encouraging demonstrating a significant interest in this research area for Toulouse’s space industry stakeholders. Feedback has identified several scientific bottlenecks in the field of screw connections with small-diameter inserts. The thesis will focus on (i) the influence of manufacturing and installation defects on inserts, (ii) the behavior of small-diameter screw connections during tightening, and (iii) their service life under various thermomechanical loading conditions. To achieve this, the scientific approach will involve a continuous dialogue between testing and simulation, through a multi-scale analysis of the connection. One of the experimental challenges w, lies in the small diameter of the screws, which complexifies the instrumentation needed to identify the force within the screw. The goal of this thesis is to better understand the interaction between the insert installation process, assembly tightening and its service life. The thesis work will address several key issues:

– The first area of focus will be the characterization of the inserts. Mechanical and morphological tests will provide insights into their mechanical strength, which is strongly influenced by their manufacturing process. The literature is limited, and the few available data sheets from insert suppliers do not provide sufficient mechanical characteristics for numerical modeling.– Insert installation relies on the expertise of trained operators. Despite this, defects can occur during insert installation or thread machining, which may affect the assembly’s tightening and resistance. Installation processes must be observed and studied.– During the tightening operation, the insert modifies the behavior of the pre-stressed assembly. Innovative tightening methods using connected tools or new measurement techniques to identify the torque-tension relationship will be investigated. These will help to determine the insert’s impact on preload in the event of multiple tightening operations.– Once the preload is applied in the assembly, with or without defects, the study of its resistance under static loads and in a vibrational thermal environment will help answer questions about the integrity of structures assembled with inserts.The purpose of the work is to develop a calculation model for the preliminary design of assemblies that describes the local behavior of connections. The assembly elements will be simplified into a single macro-element. This model will be based on a study at different scale levels, from the local scale of load transfer in the technological elements to the global scale of the multi-fastener assembly.For more Information about the topics and the co-financial partner (found by the lab !); contact Directeur de thèse –Then, prepare a resume, a recent transcript and a reference letter from your M2 supervisor/ engineering school director and you will be ready to apply online before March 14th, 2025 Midnight Paris time !ProfilMaster 2 ( .) or engineering school diploma in mechanical engineering: numerical simulation (finite elements), mechanical characterization, experimental testingLaboratoireICAMessage from PhD teamCNES will inform about the status of your application in mid-June. More details on CNES website :

Expected salary

Location

Toulouse

Job date

Wed, 05 Feb 2025 06:05:14 GMT

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