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The tightening of bolted joints.

Humble, Peter A. (1986) The tightening of bolted joints. Doctoral thesis, University of Surrey (United Kingdom)..

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This thesis presents a review of different techniques to tighten a bolted joint and investigates the ability of the methods to tighten the joint to a prescribed bolt tension. A literature survey was undertaken which revealed that different opinions exist regarding the performance of certain tightening methods and the influence of several commonly encountered factors on them. Test equipment was designed and built to study the performance of five tightening methods: torque control, angle control - elastic range, angle control - yield range, yield control, and load indicating washers. The effects of a number of practical factors on the performance of these methods were investigated. The main factors investigated were: joint stiffness, nut and bolt plating and geometry, and washer type. The tests have shown that yield controlled tightening and angle control (yield range) provide the most accurate methods of tightening a bolted joint to a prescribed bolt tension (+/- 5%). Torque control and load indicating washers (Coronet) can tighten the joint to +/- 10%. Angle control (elastic range) gives relatively poor control over bolt tension (+/- 14%), largely due to variations in snug position and tension-angle gradient. The deflections of the joint components influence the performance of the angle-related tightening methods. The deflection of the threaded connection itself is significant, especially for 'hard' joints. This contribution to the overall deflection has been largely neglected in previous studies. Methods to improve the accuracy of the tightening methods are discussed. In particular the use of hardened washers to improve the accuracy and repeatability of torque control is recommended. Furthermore, preliminary tests were conducted on the design of a washer, which would indicate when the joint has been tightened to a prescribed tension.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
Humble, Peter A.
Date : 1986
Contributors :
Depositing User : EPrints Services
Date Deposited : 09 Nov 2017 12:17
Last Modified : 20 Jun 2018 11:27

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