Design and Analysis of Detachable Bolt Head (Zinc-Cap) from Zinc-Aluminum Series Alloys

Bolted joints are essential components in many engineering applications, especially in power transmission lines where structures are exposed to severe vibrations and low-frequency galloping oscillations. These dynamic effects can cause bundle conductors to collide, leading to mechanical wear and reduced system stability. Spacer dampers are therefore installed to maintain conductor spacing and mitigate vibration. However, their clamps must be tightened with precise torque values to function correctly. Under-tightening can lead to clamp slippage, while over-tightening may damage the conductor strands in aluminum-to-aluminum interfaces. To address this challenge, a torque-limiting separable bolt head, called the Zinc-Cap, has been specifically designed. The product consists of two zamac alloy sections connected by a thin, intentionally weakened shear region. The upper section transfers torque during installation, while the lower section grips the bolt head with a tight-fit geometry. When the applied torque reaches the predetermined limit of 45 Nm, the shear zone undergoes controlled fracture, separating the upper part from the lower part. This mechanism prevents further tightening and ensures the bolt is consistently fastened to the correct torque value, independent of installer skill.