Experimental Study Of Dynamic Characteristics Of Stranded Wire Helical Springs Under Shock Load

A stranded wire helical spring, also multi-strand spring for short, is normally reeledby a multilayer and coaxial strand that is made up of several steel wires. Due to theadvantages of higher reliability, longer life and better damping effect compared withconventional single wire helical springs, the spring is especially suitable for theenvironment of high speed impact and vibration, and is being more and moreextensively interested. As a damping element, it’s mainly used in the field of aeroengine,automatic weapons launching systems, vehicle shock absorber and key reset parts ofhigh-precision instrument.As the complicated structure of spring, the complex contact friction between steelwires results that the static response and dynamic response of stranded wire helicalsprings have distinct nonlinear characteristics, such as nonlinear stiffness, nonlineardamping, hysteresis characteristics and so on, which result the corresponding researchof the dynamic response is more difficult, too. However, when used as the recoil springin reciprocating movement, the spring is mainly subjected to high-speed impact load.Not only the deformation speed of spring is very fast, but also the deformation andstress distribution is very nonuniform. At present, scholars whose researches aregenerally based on static load model, contribute little study on such spring. Therefore,the research group independently developed a set of dynamic parameter detectingequipment to study the dynamic characteristics of stranded wire helical springs underimpact load.This paper is aim to perfect the equipment and related theory research, analysis thestress and deformation of steel wires, establish the impact response dynamic models ofthe spring, and research the dynamic response characteristics based on the theoryresearch and the experiment. The mainly research works are as follows:①According to the different mechanical characteristics of the strand tightenedbefore and after, the stress and deformation of steel wires are analyzed. Combining thethird strength theory with impact dynamics theory, the strength of steel wires arechecked, and the maximum impact load and velocity are calculated, respectively. Theresearch can not only provide experimental condition for the follow-up experiment, butalso guide the parameter design of the spring.②According to the different treatment of the strongly nonlinear stiffness, the equivalent linear model and improved nonlinear model for the impact response ofspring are established. Applying the parameters transfer principle of modifiedLindstedt-Poincare method to multi-scale method, the response of nonlinear model issolved, which can provide the theory basis for the follow-up experimental reaearch.③Based on the highly precision counter and the corresponding driving function ofdata acquisition card(PCL-724), the control software under Windows interface used fordata collection is developed. The software not only realizes the microsecond level dataacquisition and real-time control, but also improves the data acquisition system of theequipment.④Combining the theory research with the improved equipment, the experimentalstudy of shock load characteristics of stranded wire helical springs is carried out. On thebasis of the experimental results, the response of displacement, velocity andacceleration of the spring and and the internal movement regularity of the spring areanalysed. And the damping and stiffness characteristics of the spring under shock loadare analysed.