Failure Analysis of the Longitudinal Composite Leaf Spring
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TECHNICAL ARTICLE—PEER-REVIEWED
Failure Analysis of the Longitudinal Composite Leaf Spring Lubin Wang . Zhenyu Wang
Submitted: 12 March 2020 Ó ASM International 2020
Abstract This paper describes the common structure of the longitudinal composite leaf spring as well as the stress of different parts. Combined with force analysis, various failure modes may occur in the middle and end parts of the composite leaf spring. Attention should be paid to the stress concentration in the clamping area in the middle of the leaf spring, caused by U-bolt pre-tightening. At the end of the composite leaf spring, enough bolt hole-edge distances shall be ensured and attention should also be paid to the stress concentration caused by the bolt. In spring design, the static stiffness of the composite leaf spring can be appropriately increased to ensure the suspension has sufficient offset frequency. At the same time, attention should be paid to the glass transition temperature (Tg point) value of the resin, which is suggested to be higher than 80 °C. Keywords Composite material Longitudinal leaf spring Failure analysis
Introduction The leaf spring is the most widely used elastic element in the automotive suspension. The most commonly used leaf springs on the Chinese market are steel leaf springs. Steel leaf springs have the advantages of simple structure, reliable operation and easy processing. However, at the same time, steel leaf springs have the disadvantages of heavy structure, high stiffness and poor comfort. Traditional leaf springs are no longer able to meet the industry needs. L. Wang (&) Z. Wang Ningbo HuaXiang Automotive Technology Co., Ltd., Ningbo 315033, Zhejiang, China e-mail: [email protected]
Reducing the weight of a car has special significance to its development. In order to improve the performance of leaf springs, reduce their weights and improve comfort, researchers have conducted a lot of research on the material and the structure of leaf springs [1]. They have developed composite leaf springs that use plastic instead of steel [2, 3]. Compared with traditional steel leaf springs, composite leaf springs’ weight is only 30–40% of steel leaf springs of the same type [4]. Composite leaf springs inherit the advantages of simple structure and reliable operation of steel leaf springs. At the same time, it has the characteristics of large elastic strain, high specific strain energy, long fatigue life, and good safety fracture performance. At present, composite leaf springs outside China have gone into mass production and been put into practical use by companies, such as GM, Ford, Daimler, Chrysler, Iveco, and International Truck. Compared with traditional metal materials, composite materials have the advantages of high strength, large specific modulus, light weight, corrosion resistance, good shock absorption performance, excellent impact resistance performance, long service life, good noise reduction performance and excellent designability [5–7].
Composite Leaf Spring Structure The typical structure and insta
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