• Learn why there can be such a significant variation in the preload (tension in the bolt) and the consequences of this.
• How the torque is distributed between the threads and the nut face when free spinning and torque prevailing fasteners are used.
• Why preload is so crucial in a bolted joint.
• How preload variation can be accounted for at the design stage.
• The effect of the tightening method on the preload variation sustained by a fastener.

• What is galling and what types of materials tend to be affected?
• Examples of fastener threads that have galled, sectioned and x-ray photos.
• Four ways that galling can be eliminated.

Methods of Tightening Threaded Fasteners

Have an understanding of the principles behind each of the following tightening methods:

• Torque controlled tightening.
• Torque-angle controlled tightening.
• Yield controlled tightening.
• Bolt stretch method.
• Heat tightening.
• The use of load indicating methods.
• The use of ultrasonics to determine bolt loading.

• Learn the differences between a manufacturing and design quality defect.
• Be able to identify whether a failure is due to a fault in the design specification or is manufacturing related.
• Learn the 5 main design related failure modes of threaded fasteners and bolted joints.
• Have knowledge of the critical importance of a fastener's clamp force in ensuring a joint's structural integrity.
• Why the joint design normally prevents bolt overloading.
• Learn about fatigue and where failures normally occur on a threaded fastener.
• Why bearing stress can be crucial in ensuring a reliable joint.
• Learn about the nature of internal and external thread stripping failures.
  

Have an overview of the research completed over the last 50 years into establishing the cause of self-loosening of threaded fasteners.
Appreciate the forces that are acting on the threads that tend to self loosen a fastener.

• Why fine threads can resist loosening better than coarse threads. The inclined plane analogy.
• Learn about the work completed by Goodier and Sweeney into loosening due to variable axial loading.
• The work completed by ESNA and the theory of shock induced loosening and resonance within fasteners.
• The MIL-STD 1312-7 vibration test for fasteners.
• Junker’s theory on self-loosening of fasteners and why fasteners self-loosen.
• The Junkers/transverse vibration test for fasteners.
• The influence that vibration amplitude has on the fastener self-loosening rate.
• Preload decay curves and the effectiveness of various fastener types in resisting vibrational loosening.
• The findings of Haviland and Kerley and how fasteners can come loose as a result of bending, shock or impact and differential thermal expansion.
• Conclusions from the research and how loosening can be prevented.

• What is meant by a tightening torque?
• Units used to measure torque.
• What are the consequences of not applying sufficient torque to a bolt.
• How torque is absorbed by a nut/bolt assembly.
• The torque-tension graph.
• The relationship between the tightening torque and the resulting bolt preload (tension).
• The factors which affect the torque-tension relationship.
• The nut factor method of determining the correct tightening torque.
• Example calculation of how to determine the correct tightening torque.
• Scatter in the bolt preload resulting from friction variations.
• Determining the bolt preload (tension) resulting from a tightening torque.
• Prevailing torque fasteners (such as those containing a nylon insert) and how they affect the torque distribution and the correct torque to use.

Load Sensing Fasteners

• The use of strain gauged bolts.
• The use of load cells.
• The use of Rotabolts™.
• The use of Smartbolts™.
• The use of direct tension indicators (load indicating washers).
• Squirter™ direct tension indicators.
• Tension control bolts.

Hydraulic Tensioning of Threaded Fasteners

• The principles behind hydraulic tensioning.
• The number of tensioners that are used to tighten a joint – 100%, 50%, 33% and 25% tensioning methods.
• The effect of elastic recovery on the tension induced into a bolt.
• The use of hydraulic nuts and the sequence used to tighten them.
• The use of oil filled nuts.
• The use of rubber filled nuts.

• The problems of tightening multi-bolt assemblies.
• Elastic interaction or bolt cross-talk.
• The use of a tightening sequence.
• The single pass tightening sequence.
• Tightening sequences for non-circular bolt patterns.
• Tests completed to verify tightening sequences.
• The two pass tightening sequence.
• The use of multiple tightening tools.
• Bolt cross talk and hydraulic tensioning.
• Methods that can be used to check the tightening sequence.
• The solder plug method.
• The use of pressure sensitive films.
• Establishing a tightening procedure.
• Examples of tightening sequences for circular joints consisting from 4 to 32 bolts are given in the handbook together with an example tightening procedure.
  

A training course handbook is provided that contains background information to the material presented in the course, together with appendices containing tables of thread size details, fastener material strengths and a glossary detailing the key terms used in bolting technology.

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