Author: Ling Chen
Chen, Ling, 2025 Design, manufacturing, experimental evaluation and numerical analysis of novel composite helical springs, Flinders University, College of Science and Engineering
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The past few years have witnessed a potentially increase of composite helical springs (CHSs) deployment. They can not only save fuels and thus expand overall cruising ranges but also reduce greatly carbon dioxide emissions. However, the insufficient of design method and the lack of comprehensive performance evaluation methods limit the application and development of CHSs. To solve this problem, the reinforcement structure of CHSs first is designed by combining the force analysis and textile structure, The initial compression comparison shown that CHSs with braided reinforcement (BCHS) have optimal stiffness among them. Hence the BCHS have been selected for studying further static and dynamic performance by combining experiment and simulation. The static performance has been optimized based on BCHS with single braided layer (SBCHS) with different braided angle of 0o, 15o and 30o (UCHS, SBCHS15° and SBCHS30°) The compression experimental results show that the spring constant of SBCHS15o and SBCHS30o can reach 105.4% and 171.4% higher than that of UCHS respectively. Therefore, the 30o braided angle have been selected to further optimized the dynamic performance based on the braided layer number. Then, the dynamic impact performance has been explored by comparing BCHS with multi-braided layers (MBLs-CHS) including BCHS with single, double and triple braided layers (SBCHS, DBCHS and TBCHS). Experimental results elucidate a sequential improvement in the impact performance of SBCHS, DBCHS, and TBCHS. Due to damage evolution under impact is challenging to detect physically in real time. Time domain analysis is introduced to explore the in real time relationship between impact force and damage. The stiffness degradation under various amplitude intensity of MBLs-CHS have been fitted to predict the global stiffness degradation of MBLs-CHS in real time. Based on above analysis, the TBCHS not only have best static and dynamic impact performance but also have minimum damage than SBCHS and DBCHS. Therefore, TBCHS is used to further explore the fatigue performance. The result shown that the life of TBCHSs under 100% and 90% stress levels is only 2000 and 6500 respectively based on the failure stiffness of 38.7kgf/mm. But when the stress level drops to 70%, the stiffness decreases only 1.3% after 30000 cycles, which shows that the TBCHSs can be used for long time under the stress level of less than 70%. Apart from the optimization of static and dynamic performance, the feasibility of replace metal spring using TBCHS have been further investigated through installing TBCHSs in the vehicle. The experiment result showed that there is no damage to the front TBCHSs. The damage just occurs on the resin component of the posterior region of rear TBCHSs. After resin optimization, the optimal TBCHSs have been successfully installed on the vehicle without damage, illustrating the feasibility of applicating optimal TBCHSs. This research establishes a robust foundation for performance studies and offers valuable guidelines for the engineering application of CHSs.
Keywords: composite helical springs, reinforcement structure, braided angle and layer, static and dynamic performance, numerical analysis
Subject: Engineering thesis
Thesis type: Doctor of Philosophy
Completed: 2025
School: College of Science and Engineering
Supervisor: Youhong Tang