Abstract
Recoil spring is a key part in automatic or semi-automatic weapons re-entry mechanism. Because the stranded wire helical spring (SWHS) has longer fatigue life than an ordinary single-wire cylindrically helical spring, it is often used as a recoil spring in various weapons. Due to the lack of in-depth research on the dynamic characteristics of the current multi-wire recoil spring in recoil and re-entry processes, the fatigue life analysis of the current multi-wire recoil spring usually only considers uniform loading and does not consider dynamic impact loads, which cannot meet modern design requirements. Therefore, this paper proposes a research method for fatigue life prediction analysis of multi-wire recoil spring. Firstly, based on the secondary development of UG, a three-wire recoil spring parameterized model for a gun is established. Secondly, ABAQUS is used to carry out a finite element analysis of its dynamic response characteristics under impact, and experimental verification is performed. Then, based on the stress-time history curve of the dangerous position obtained by finite element analysis, the rain flow counting method is used to obtain the fatigue stress spectrum of recoil spring. Finally, according to the Miner fatigue cumulative damage theory, the fatigue life prediction of the recoil spring based on the S-N curve of the material is compared with experimental results. The research results show that the recoil spring has obvious transient characteristics during the impact of the bolt carrier. The impact velocity is far greater than the propagation speed of the stress wave in the recoil spring, which easily causes the spring coils to squeeze each other. The maximum stress occurs at the fixed end of the spring. And the mean fatigue curve (50% survival rate) is used to predict the life of the recoil spring. The calculation result is 8.6% different from the experiment value, which proves that the method has certain reliability.
Highlights
Recoil spring is a key part used in the re-entry mechanism of automatic or semi-automatic weapons to store energy during the recoil of the moving parts and release energy during the re-entry process to make the moving parts complete the reentry
Because the SWHS has longer fatigue life than an ordinary single-wire cylindrically helical spring, it is often used as a recoil spring in various weapons
Due to the complex contact friction between the wires, the multi-wire recoil spring has nonlinear characteristics of stiffness and damping. erefore, when the multi-wire recoil spring is subjected to high-speed impact loads during recoil and re-entry processes, its impact characteristics are different from ordinary single-wire cylindrically helical springs
Summary
Recoil spring is a key part used in the re-entry mechanism of automatic or semi-automatic weapons to store energy during the recoil of the moving parts and release energy during the re-entry process to make the moving parts complete the reentry. Erefore, when the multi-wire recoil spring is subjected to high-speed impact loads during recoil and re-entry processes, its impact characteristics are different from ordinary single-wire cylindrically helical springs. Fatigue life research on SWHS is rare at present, and multi-wire recoil springs of automatic weapons are subject to high-speed impact during launch. Based on the actual operating conditions, a set of test devices for the impact characteristics of the recoil spring is developed, and the dynamic parameters such as the motion displacement, velocity, acceleration, stress, and strain of the various points of the spring coils are analyzed. The engineering calculation based on Miner theory is used to predict the fatigue life of recoil spring It can provide some theoretical support for the research of other springs or automatic weapon recoil spring
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