Flange Bolts' Ascendancy: The Waning Role of Washer Designs

Washers, traditionally crucial in engineering for securing joints, protect surfaces from direct contact damage and distribute stress evenly under fastener heads to maintain stability. However, with technological progress and evolving engineering practices, flange bolts are supplanting washers in certain applications. This exploration delves into the rationale for this shift.

Torque control over bolt clamping force is a prevalent engineering method, straightforward and familiar to practitioners. Yet, it's evident that friction on the bolt threads and head consumes much of the applied torque, translating less torque into actual clamping force.

Washers, often softer than bolts and nuts, are susceptible to deformation under stress, compromising their integrity and potentially the bolt's clamping force. Flange bolts, with consistent hardness across the support surface, maintain performance under stress without such issues.

The washer's clearance hole, necessary to avoid interference with the bolt head's transition arc, can lead to misalignment during tightening, causing eccentric loading and stress concentration. This increases the risk of damage and affects the fastening system's safety and stability.

Washer rotation during tightening can alter the torque-clamping force relationship, leading to significant clamping force loss. This issue is challenging to detect without vigilant monitoring.

The use of washers also multiplies contact surfaces, leading to embedding at the microscopic level and a consequent loss of clamping force, particularly pronounced on painted surfaces. This effect is exacerbated by washers, further diminishing bolt clamping force.

In conclusion, while washers have been vital in traditional fastening, their drawbacks are significant. Flange bolts offer greater stability, reliability, and lower maintenance, prompting a shift towards their use. Engineers are increasingly opting for flange bolts over traditional washer-equipped fasteners, adjusting installation torque to optimize fastening outcomes.