Effect of Ramp Angle on the Anti-Loosening Ability of Wedge Self-Locking Nuts Under Vibration

Abstract

Recently, the wedge self-locking nut, a special anti-loosening product, is receiving more attention because of its excellent reliability in preventing loosening failure under vibration conditions. The key characteristic of a wedge self-locking nut is the special wedge ramp at the root of the thread. In this work, the effect of ramp angle on the anti-loosening ability of wedge self-locking nuts was studied systematically based on numerical simulations and experiments. Wedge self-locking nuts with nine ramp angles (10 deg, 15 deg, 20 deg, 25 deg, 30 deg, 35 deg, 40 deg, 45 deg, and 50 deg) were modeled using a finite element (FE) method, and manufactured using commercial production technology. Their anti-loosening abilities under transversal vibration conditions were analyzed based on numerical and experimental results. It was found that there is a threshold value of the initial preload below which the wedge self-locking nuts would lose their anti-loosening ability. This threshold value of initial preload was then proposed for use as a criterion to evaluate the anti-loosening ability of wedge self-locking nuts quantitatively and to determine the optimal ramp angle. Based on this criterion, it was demonstrated, numerically and experimentally, that a 30 deg wedge ramp resulted in the best anti-loosening ability among nine ramp angles studied. The significance of this study is that it provides an effective method to evaluate the anti-loosening ability of wedge self-locking nuts quantitatively, and determined the optimal ramp angle in terms of anti-loosening ability. The proposed method can also be used to optimize other parameters, such as the material properties and other dimensions, to guarantee the best anti-loosening ability of wedge self-locking nuts.

Concept of radial slippage propagation triggering self-loosening and optimisation design of novel anti-loosening structures

“…Spiralock thread form as an anti-loosening structure has a modified thread profile including a 30° wedge ramp, as shown in Fig. 24 [30]. After the Spiralock nut is tightened, the tip of the regular bolt will be embedded into the wedge ramp.…”

“…An FEM of engagement between regular bolt and Spiralock nut was built based on the method proposed by Liu et al [30], as shown in Fig. 25.…”

“…The latter mainly consists of wedge locking nuts, prevailing torque nuts, eccentric double nuts, and double nuts. They have been demonstrated to provide superior anti-loosening abilities [28][29][30][31]. In the transversal vibration experiment or finite element (FE) simulation, the preloads decrease very slowly or remain almost unchanged with the increase in vibration cycles.…”

A novel method for high-frequency non-sinusoidal vibration waveforms with uniaxial electro-hydraulic shaking table based on Fourier series

“…In the vibration test, different vibration waveforms are used to simulate various conditions. Except for the sinusoidal vibration waveform, non-sinusoidal vibration waveforms are often required in the vibration technology (Liu et al, 2018; Nakata, 2012; Pagano et al, 2013). Thus, the vibration waveform is clearly a key consideration in the construction and control of a uniaxial electro-hydraulic shaking table.…”

Bi-objective optimization design of material stiffness for improving contact interface performances

“…15 The effect of the screw thread shape on the anti-loosening ability of wedge self-locking nuts was investigated by Liu et al, and the shape of the screw thread was described in the form of a ramp angle. 16 In addition to the shape and the topology, the contact pressure and its distribution are also sensitive to the interfacial hardness and the material stiffness of the contact parts. Benefiting from the development of the surface hardening techniques, such as laser peening and warm laser shock peening, variable hardness or material stiffness designs are receiving increasing attention in many aspects, especially in the application of resisting wear and damage of the contact interfaces with relative motion.…”