Course Details

Detail course structure

·--------------------Day1--------------------·

1) Introduction to Threaded Fasteners

• Some thread terminology
• Background to modern threads - the roles of Whitworth and Sellers and the development of the metric thread
• The difference between a fine and coarse thread and the advantages/disadvantages of each
• The basic profile of Unified and metric thread forms
• Thread tolerance positions, grades, and the different tolerance classes that are available
• The stress area, what it is and how is it derived

2) Strength of bolts

• The principles of bolt elongation, bolt stress and load
• Yield, tensile strength and proof load properties
• Details of common bolting specifications
• Upper and lower strength limits for bolts
• Bolt and nut head markings and identification of correct components
• Stainless steel fasteners ISO 3506, Duplex and Super Duplex stainless steel fasteners
• Nut/bolt combinations, nut strength versus bolt strength
• Upper and lower temperature limitations of common bolting materials

 3) Methods of Tightening

• Threaded Fasteners
• Overview of the methods used to tighten bolts
• Load-angle of turn graph for a bolt tightened to failure
• Torque controlled tightening method
• Torque-angle tightening below the yield point
• Projected angle tightening method below the yield point
• Yield point tightening using incremental angle method
• Yield point tightening method using slope measurement
• Torque-angle tightening method into the plastic region
• Yield control tightening plus an angle increment
• Limited re-use of bolts sustaining plastic deformation
• Bolt tensioning using hydraulic tensioning method
• Tightening by elongation measurement
• Heat tightening of large bolts
• Tension indicating methods using load indicating bolts and washers
• Use of ultrasonic for bolt tightening

4) Why bolts should be tightened

• The "Bolted Joint Enigma“ and why is tightening a bolt important?
• How a preload joint sustains an axial load
• Joint separation – what is it and why is it important
• Why tightening bolts is important for shear loaded joints
• Explanation of why the bolt usually sustains a small proportion of an axial load
• A case study of bolt failure in which part of the fastener was not tightened

·--------------------Day 2--------------------·

5) Fastener Failure Modes

• Overview of the ways threaded fasteners can fail
• Manufacturing Related Quality Defects
• Design Related Quality Defects
• Failure by insufficient preload - examples including joint slip, joint separation and gasket sealing failures
• Fatigue failure of bolts
• Thread Stripping Failures - internal and external threads
• Bolt overload from applied forces
• Bearing stress under the bolt head or nut face

 6) Torque Control

• What does a tightening torque mean? Units used to measure torque
• What are the consequences of not applying sufficient torque to a bolt
• How a nut/bolt assembly absorbs torque?
• 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
• Using the full torque-tension equation to determine the appropriate 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 it affects the torque distribution and what is the correct torque to use
• Tests to determine the coefficient of friction of threaded fasteners

7) Self-Loose Threaded Fasteners

• Non-rotational loosening (relaxation) and rotational loosening (self-loosening).
• Have an overview of the research completed over the last 50 years into establishing the cause of the 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

8) Systematic Calculation of Bolted Joints

• Why are systematic methods important?
• Development of Joint Diagrams
• VDI 2230 Background and range of validity
• Key concepts of VDI 2230, failure modes of bolted joints
• VDI 2230 - The Calculation Steps
• Initial bolt sizing
• Determining the Tightening Factor
• Determining the minimum clamp load
• Determining the load factor
• Relaxation/embedding loss in bolted joints
• Effect of temperature change
• How to determine the minimum assembly preload
• Determining the maximum assembly preload
• Establishing the bolt assembly stress
• Determining the bolt working stress
• Establishing the alternating stress in the bolt
• Importance of the bearing stress under the nut
• Thread stripping checks
• Joint slip and bolt shear stress
• Limitations of VDI 2230
• Software of VDI 2230 calculations

 ·--------------------Day 3--------------------·

9) Preload Requirement Charts

• How to prevent the majority of bolting issues
• Determining the maximum and minimum preloads
• How to calculate the likely embedding loss
• Establishing the axial force requirement
• Establishing the shear force requirement
• Determining the total force requirement for the joint
• Example calculations
• Ways in which a bolting design problem can be resolved
• Example problems for the student to resolve

 10) Bolts in Direct Shear and Axially Loaded

• The difference between a friction grip and a joint whose bolts are in direct shear
• The effect of having bolts in direct shear when a friction grip joint is more appropriate
• Joints in single and double shear
• The shear capacity of bolts in direct shear and the importance of the location of the shear plane
• The ratio of shear strength to tensile strength for steel
• How to determine the shear strength of bolts in direct shear
• Joints consisting of multiple bolts
• Joints in direct shear and axially loaded as well

 11) Fatigue of Threaded Fasteners

• Background to fatigue failures
• An explanation of what is fatigue
• The causes of fatigue to be able to recognise this type of failure
• Beach marking and why fatigue failures usually occur in the threads
• The S-N diagram and the endurance strength of a threaded fastener
• The difference between the load acting on a joint and that sustained by a bolt
• The different approaches that can be used to establish the endurance strength of a pre-tensioned threaded fastener
• The effect that joint face angularity can have on the fatigue performance of a fastener
• How the fatigue performance of a bolt can be improved
• The effect that bolt diameter has on fatigue performance

12) Thread Stripping

• Identify the thread stripping
• Be ableism the shear area of an internal or external thread
• How the tapping drill size affects the strength of the bolt thread.
• How the radial engagement of threads affects thread strength and the failure load.
• Use the information provided on the course to calculate the internal and external thread areas and the force needed to cause the threads to strip.
• Be able to establish the length of thread engagement needed to prevent thread stripping.
• Example problems will be shared together with questions and answers. stripping calculations so that you have confidence to use them in practical applications

·--------------------Day 4--------------------·

 13) Shear Loads applied to Bolted Joints

• What is meant by an eccentric shear load
• Understand the slip process that can occur with shear loaded joints
• Learn what is meant by the instantaneous centre of rotation for the joint
• Be able to calculate the reactions of individual bolts when shear forces are applied to the joint
• Some real examples to use them in practical applications

14) Galling of Threaded Fasteners

• Background and explanation of galling
• Types of fastener material and finishes susceptible to galling
• Examples of thread galling.
• Approaches that are used to prevent/minimize galling

 15) Combined Tension and Shear Loading

• What is meant by an eccentric shear load
• Understand the slip process that can occur with shear loaded joints
• Learn what is meant by the instantaneous centre of rotation for the joint
• Be able to calculate the reactions of individual bolts when shear forces are applied to the joint
• Perform example calculations so that you have confidence to use them in practical applications.
• Learn the methods that can be used to analyze joints subjected to combined tension and shear loads.
• What is meant by prying and its effects
• Two methods that can be used to determine the neutral axis of the joint when combined tension and shear loads are acting
• Some real examples to use them in practical applications

Eligibility: Participant must have an experience in  Mechanical / Electrical / Instrumentation / Civil Engineering