Introduction to the Design and Behavior of Bolted Joints: Non-Gasketed Joints

Cover
Half Title
Title Page
Copyright Page
Dedication
Contents
Preface
Acknowledgments
Authors
Chapter 1: Basic Concepts
1.1. Two Types of Bolted Joints
1.2. Bolt's Job
1.2.1. Tensile Joints
1.2.2. Shear Joints
1.3. The Challenge
1.3.1. Assembly Process
1.3.2. The Complexity of Tightening the Bolt
1.3.3. In-Service Behavior
1.3.3.1. Joints Loaded in Tension
1.3.3.2. Shear Joints
1.4. Failure Modes
1.5. Design
1.5.1. In General
1.5.2. Specific Goals of the Designer
1.5.3. Final Thought
1.6. Layout of the Book
Exercises
References
Chapter 2: Materials
2.1. Properties That Affect the Clamping Force
2.1.1. Magnitude of the Clamping Force
2.1.2. Stability of the Clamping Force
2.1.2.1. Thermal Expansion or Contraction
2.1.2.2. Corrosion
2.1.2.3. Fatigue Rupture
2.1.2.4. Loss of Strength with Temperature
2.1.2.5. Loss of Clamping Force with Temperature
2.1.2.6. Elastic Stiffness of the Parts
2.1.2.7. Change in Stiffness with Temperature
2.1.2.8. Brittle Fracture
2.1.3. Miscellaneous Properties
2.2. Fastener Standards
2.3. Selecting an Appropriate Standard
2.4. Bolting Materials
2.5. Tensile Strength of Bolting Materials
2.5.1. General Purpose/Automotive Group
2.5.2. Structural Steel Group
2.5.3. Petrochemical/Power Group
2.5.4. Metric Group
2.5.5. Extreme-Temperature Materials
2.5.5.1. American Society for Testing and Materials (ASTM) F2281 Materials
2.5.5.2. Traditional High-Temperature Materials
2.5.6. Corrosion-Resistant Group
2.5.7. ASTM Bolting Standards
2.5.7.1. Room Temperature Strengths of ASTM F2281 and F2282 Materials
2.6. Metric Fasteners
2.7. Equivalent Materials
2.7.1. Steel Designation
2.8. Some Comments on the Strength of Bolting Materials
2.8.1. In General
2.8.2. Shear Strength
2.8.3. Bearing Yield Strength
2.8.4. Hardness Versus Strength
2.9. Nut Selection
2.10. Effects of Temperature on Material Properties
2.10.1. Thermal Expansion
2.10.2. Miscellaneous Temperature Problems
2.11. Other Material Factors to Consider
2.11.1. Fatigue Properties
2.11.2. Corrosion
2.11.3. Miscellaneous Considerations
2.12. Joint Materials
2.13. The Affect of Material Hardness on the Development of Preload
2.14. The Manufacturing of Threaded Fasteners
2.14.1. Creating the Threaded Fastener
2.14.2. Microstructure
Exercises
References
Chapter 3: Stress and Strength Considerations
3.1. Types of Strength
3.1.1. Tensile Strength
3.1.2. Thread-Stripping Strength
3.1.3. Shear Strength
3.1.4. Brittle Fracture Strength
3.1.5. Strengths at High and Low Temperatures
3.1.6. Fatigue Strength
3.1.7. Stress Corrosion Cracking Strength
3.2. Bolt in Tension
3.2.1. Elastic Curves for Bolts in Tension
3.2.2. Elastic Curves Under Repeated Loading
3.2.3. Stress Distribution Under Tensile Load
3.2.4. Stress Concentrations
3.2.5. Magnitude of Tensile Stress
3.2.6. Load Distribution and Stress in the Nut
3.3. Strength of a Bolt
3.3.1. Proof Strength
3.3.2. Tensile Stress Area
3.3.3. Other Stress Area Equations
3.3.4. Stress Areas—Metric Threads
3.3.5. Strength of the Bolt Under Static Loads
3.3.6. Static Failure of the Bolt
3.4. Strength of the Joint
3.4.1. Contact Stress between Fastener and Joint
3.4.2. Stresses within and between the Joint Members
3.4.3. Static Failure of the Joint
3.5. Other Types of Load on a Bolt
3.5.1. Strength under Combined Loads
Exercises
References
Chapter 4: Threads and Their Strength
4.1. Thread Forms
4.1.1. Thread Forms in General
4.1.2. Inch Series Thread Forms
4.1.3. Metric Thread Forms
4.2. Thread Series
4.2.1. Inch
4.2.2. Metric
4.3. Thread Nomenclature: Diameters, Allowance, Tolerance, and Class
4.3.1. Diameters
4.3.1.1. Tolerance and Allowance
4.3.1.2. Allowance
4.3.1.3. Tolerance
4.3.1.4. Thread Class
4.3.2. Metric Threads
4.3.2.1. Tolerance Position (Allowance)
4.3.2.2. Tolerance Grade (Tolerance)
4.3.2.3. Tolerance Class (the Class)
4.3.3. Inch Series and Metric Thread Classes, Compared
4.3.4. Formulas for Tolerance and Allowance
4.3.5. Coating Allowances
4.3.6. Tolerances for Abnormal Lengths of Engagement
4.4. Thread Inspection
4.4.1. Inspection Levels
4.4.2. Gaging
4.4.3. Thread Errors
4.4.4. Actual Inspecting
4.5. Thread Call-Outs or Identification on Drawings
4.5.1. Inch Series
4.5.2. Metric Thread
4.5.3. The Drawing
4.6. Coarse- Versus Fine- Versus Constant-Pitch Threads
4.6.1. Coarse-Pitch Threads
4.6.2. Fine-Pitch Threads
4.6.3. Constant-Pitch Threads
4.6.4. Miscellaneous Factors Affecting Choice
4.7. 3D Modeling of Threads
4.8. The Strength of Threads
4.8.1. Basic Considerations
4.8.2. Thread Strength Equations
4.8.3. Thread Strength Computations When LE = D
4.8.4. Basic Procedure—An Example
4.8.5. Thread Strength Calculations When LE ≠ D
4.8.6. Other Stress Area Formulas
4.9. What Happens to Thread Form Under Load?
4.10. Things that Modify the Static Strength of Threads
4.10.1. Common Factors
4.10.2. Which Is Usually Stronger—Nut or Bolt?
4.10.3. Tables of Tensile Stress and Shear Areas
4.11. Other Factors Affecting Strength
4.11.1. Pitch Diameter
4.11.2. Other Thread Parameters
Exercises
References
Chapter 5: Stiffness and Strain Considerations
5.1. Bolt Deflection
5.1.1. Basic Concepts
5.1.2. Change in Length of the Bolt
5.1.2.1. Effective Length
5.1.2.2. Cross-Sectional Areas of the Bolt
5.1.3. Computing Change in Length of the Bolt
5.2. Bolt Stiffness Calculations
5.2.1. Basic Concepts
5.2.2. Example
5.2.3. Actual versus Computed Stretch and Stiffness
5.2.4. Stiffness of Bolt–Nut–Washer System
5.2.5. Alternative Expression for Bolt Stiffness
5.2.6. Energy Stored in the Bolt
5.3. The Joint
5.3.1. Basic Concepts
5.3.2. Computing Joint Stiffness
5.3.2.1. Stiffness of Concentric Joints
5.3.2.2. Stiffness of Eccentric Joints
5.3.3. Stiffness in Practice
5.3.3.1. A Quick Way to Estimate the Stiffness of Non-Gasketed Steel Joints
5.4. Gasketed Joints
5.5. An Alternate Way to Compute Joint Stiffness
5.6. Joint Stiffness Ratio or Load Factor
5.7. Stiffness—Some Design Goals
5.7.1. Energy Stored in the Joint Members
5.7.2. Relationship between Stiffness and Stored Energy
5.7.3. Stiffness Ratio
5.8. Experiments in Stiffness
Exercises
References
Chapter 6: Introduction to Assembly
6.1. Initial versus Residual Preload
6.2. Speaking of Torque
6.3. Starting the Assembly Process
6.3.1. Assembling the Parts
6.3.2. Tightening the First Bolt
6.4. Bolt Preload versus Clamping Force on the Joint
6.4.1. Effects of Hole Interference
6.4.2. Resistance from Joint Members
6.5. Continuing the Snugging Pass
6.6. Short-Term Relaxation of Individual Bolts
6.6.1. Sources of Short-Term Relaxation
6.6.1.1. Poor Thread Engagement
6.6.1.2. Thread Engagement Too Short
6.6.1.3. Soft Parts
6.6.1.4. Bending
6.6.1.5. Non-perpendicular Nuts or Bolt Heads
6.6.1.6. Fillets or Undersized Holes
6.6.1.7. Oversized Holes
6.6.1.8. Conical Makeups
6.6.2. Factors Affecting Short-Term Relaxation
6.6.2.1. Bolt Length
6.6.2.2. Belleville Washers
6.6.2.3. Number of Joint Members
6.6.2.4. Simultaneous Tightening of Many Fasteners
6.6.2.5. Bent Joint Members
6.6.3. Amount of Relaxation To Expect
6.6.4. Torsional Relaxation
6.7. The Effect of Tightening Speed on Preload Generation
6.8. Elastic Interactions Between Bolts
6.9. The Assembly Process Reviewed
6.10. Optimizing Assembly Results
Exercises
References
Chapter 7: Torque Control of Preload
7.1. Importance of Correct Preload
7.1.1. Problems Created by Incorrect Preload
7.1.2. How Much Preload?
7.1.3. Factors That Affect the Working Loads on Bolts
7.2. Torque versus Preload—The Long-Form Equation
7.3. Things That Affect the Torque–Preload Relationship
7.3.1. Variables That Affect Friction
7.3.2. Geometric Variables
7.3.3. Strain Energy Losses
7.3.4. Prevailing Torque
7.3.5. Weight Effect
7.3.6. Hole Interference
7.3.7. Interference Fit Threads
7.3.8. The Mechanic
7.3.9. Tool Accuracy
7.3.10. Miscellaneous Factors
7.3.11. Lubrication
7.4. Torque versus Preload—The Short-Form Equation
7.5. Nut Factors
7.5.1. Some General Comments
7.5.2. Nut Factor Examples and Case Histories
7.5.3. Coefficient of Friction versus Nut Factor
7.6. Torque Control in Practice
7.6.1. What Torque Should I Use?
7.6.2. Initial Preload Scatter
7.6.3. Low Friction for Best Control
7.6.4. The Lines Aren't Always Straight
7.6.5. Other Problems
7.7. Some Tools for Torque Control
7.7.1. Some Generalities
7.7.2. Reaction Forces Created by the Tool
7.7.2.1. Shear Loads Created by Torque Wrenches
7.7.2.2. Reaction Torques
7.7.3. In the Beginning—A Search for Accuracy
7.7.3.1. Manual Torque Wrenches
7.7.4. More Torque for Large Fasteners
7.7.4.1. Torque Multipliers and Geared Wrenches
7.7.4.2. Hydraulic Wrenches
7.7.5. Toward Higher Speed
7.7.5.1. Impact Wrenches
7.7.5.2. Pulse Tools
7.7.5.3. Nut Runners
7.7.6. Add Torque Calibration or Torque Monitoring
7.7.7. Add Torque Feedback for Still Better Control
7.7.8. For More Information
7.8. Chatter
7.8.1. Background
7.8.2. Torque and Preload
7.8.3. Under-Head and Thread CoF
7.8.4. How to Fix the Chatter
7.8.5. Chatter Conclusion
7.9. Fasteners that Limit Applied Torque
7.9.1. The Twist-Off Bolt
7.9.2. The Frangible Nut
7.10. Is Torque Control Any Good?
7.11. Testing Tools
7.12. The Influence of Torque Control on Joint Design
7.13. Using Torque to Disassemble a Joint
Exercises
References
Chapter 8: Torque and Turn Control
8.1. Basic Concepts of Turn Control
8.2. Turn versus Preload
8.2.1. Common Turn–Preload Relationship
8.2.2. Other Turn-Preload Curves
8.2.2.1. Sheet Metal Joint
8.2.2.2. Gasketed Joint
8.3. Friction Effects
8.4. Torque and Turn in Theory
8.4.1. Torque, Turn, and Energy
8.4.2. Torque–Turn–Preload Cube
8.4.3. The Broader View
8.5. Turn-of-Nut Control
8.5.1. The Theory
8.5.2. The Practice
8.5.2.1. Structural Steel
8.5.2.2. Turn-of-Nut Procedure in Production Operations
8.5.2.3. Turn-of-Nut Procedure in Aerospace Assembly
8.6. Production Assembly Problems
8.7. Popular Control Strategies
8.7.1. Torque–Angle Window Control
8.7.2. Torque–Time Window Control
8.7.3. Hesitation and Pulse Tightening
8.7.4. Yield Control
8.7.5. Turn-of-Nut Control
8.7.6. Prevailing Torque Control
8.7.7. Plus—Permanent Records
8.7.8. Meanwhile, Out in the Field
8.8. Monitoring the Results
8.9. Problems Reduced by Torque–Angle Control
8.10. How to Get the Most Out of Torque–Angle Control
Exercises
References
Chapter 9: Other Ways to Control Preload
9.1. Stretch Control: The Concept
9.2. Problems of Stretch Control
9.2.1. Dimensional Variations
9.2.2. Change in Temperature
9.2.3. Plastic Deformation of the Bolt
9.2.4. Bending and Non-perpendicular Surfaces
9.2.5. Grip Length
9.3. Stretch Measurement Techniques
9.3.1. Micrometer Measurements
9.3.1.1. Irregular Measurement Surfaces
9.3.1.2. Operator Feel
9.3.1.3. Measurement Accuracy Required
9.3.1.4. Depth Micrometers
9.3.2. Other Techniques
9.3.2.1. Dial Gages
9.3.2.2. Commercially Available Gage Bolt
9.3.2.3. Other Gage Measurements
9.4. How Much Stretch?
9.5. Problems Reduced by Stretch Control
9.6. How to Get the Most Out of Stretch Control
9.7. Direct Preload Control—An Introduction
9.7.1. Strain-Gaged Bolts
9.7.2. Strain-Gaged Force Washers
9.7.3. Direct Tension Indicators
9.7.4. Squirter Self-Indicating DTIs
9.7.5. Twist-Off Tension-Control Bolts
9.7.6. Alternative-Design Fasteners
9.8. Bolt Tensioners
9.8.1. The Hardware
9.9. Bolt Heaters
9.10. Problems Reduced by Direct Preload Control
9.10.1. Direct Tension Indicators
9.10.2. Twist-Off Bolts
9.10.3. Hydraulic Tensioners
9.10.4. Bolt Heaters
9.11. Getting the Most Out of Direct Preload Control
9.11.1. Twist-Off Bolts and DTI Washers
9.11.2. Bolt Tensioners
9.11.3. Bolt Heaters
9.12. Ultrasonic Measurement of Stretch or Tension
9.12.1. In General
9.12.2. Principle of Operation
9.12.3. How It's Used
9.12.4. Calibration of the Instrument
9.12.5. Presently Available Instruments
9.13. Ultrasonic Measurements Using Plasma—Coated, Thin Film Transducers
9.14. Fiber Optic Strain Measurement
9.14.1. Principle of Operation
9.14.2. How It's Used
9.14.3. Installation
9.14.4. Calibration
9.14.5. Performance
Exercises
References
Chapter 10: Theoretical Behavior of the Joint under Tensile Loads
10.1. Basic Joint Diagram
10.1.1. Elastic Curves for Bolt and Joint Members
10.1.2. Determining Maximum and Minimum Residual Assembly Preload
10.1.2.1. The Equations
10.1.2.2. An Example
10.1.3. Joint Diagram for Simple Tensile Loads
10.1.4. The Parable of the Red Rolls Royce
10.1.5. Back to the Joint Diagram—Simple Tensile Load
10.1.6. Finite Element Analysis Support
10.2. Details and Variations
10.2.1. Changing the Bolt or Joint Stiffness
10.2.2. Critical External Load
10.2.3. Very Large External Loads
10.2.4. Another Form of Joint Diagram
10.3. Mathematics of the Joint
10.3.1. Basic Equations
10.3.2. Continuing the Example
10.4. Loading Planes
10.4.1. Tension Applied to Interface of Joint Members
10.4.2. Mathematics of a Tension Load at the Interface
10.4.3. Significance of the Loading Planes
10.4.4. Loading Planes within the Joint Members
10.4.5. Modifying Our Example to Include the Effects of Internal Loading Planes
10.5. Dynamic Loads on Tension Joints
10.6. The Joint Under a Compressive Load
10.7. A Warning
Exercises
References
Chapter 11: Behavior of the Joint Loaded in Tension: A Closer Look
11.1. Effect of Prying Action on Bolt Loads
11.1.1. Definition of Prying
11.1.2. Discussion of Prying
11.1.3. Prying Is Non-Linear
11.1.4. Prying via Fea
11.2. Mathematics of Prying
11.2.1. In General
11.2.2. VDI's Analytical Procedure
11.2.3. Critical Loads and the Preloads Required to Prevent Joint Separation
11.2.4. Bending Stress in the Bolt Before Liftoff
11.2.5. Effects of Very Large External Loads
11.3. Other Non-Linear Factors
11.3.1. Nut-Bolt System
11.4. Thermal Effects
11.4.1. Change in Elasticity
11.4.2. Loss of Strength
11.4.3. Differential Thermal Expansion
11.4.4. Stress Relaxation
11.4.5. Creep Rupture
11.4.6. Compensating for Thermal Effects
11.5. Joint Equations That Include the Effects of Eccentricity and Differential Expansion
11.5.1. The Equations
11.5.2. An Example
Exercises
References
Chapter 12: In-Service Behavior of a Shear Joint
12.1. Bolted Joints Loaded in Axial Shear
12.1.1. In General
12.1.2. Friction-Type Joints
12.1.2.1. Bolt Load in Friction-Type Joints
12.1.2.2. Stresses in Friction-Type Joints
12.1.3. Bearing-Type Joints
12.1.3.1. Stresses in Bearing-Type Joints
12.2. Factors That Affect Clamping Force in Shear Joints
12.3. Response of Shear Joints to External Loads
12.4. Joints Loaded in Both Shear and Tension
12.5. Present Definitions—Types of Shear Joint
Exercises
References
Chapter 13: Introduction to Joint Failure
13.1. Mechanical Failure of Bolts
13.2. Missing Bolts
13.3. Loose Bolts
13.4. Bolts Too Tight
13.5. Which Failure Modes Must We Worry About?
13.6. Concept of Essential Conditions
13.7. Importance of Correct Preload
13.7.1. Corrosion
13.7.2. Stress Corrosion Cracking
13.7.3. Fatigue Failure
13.7.4. Mechanical Failure
13.7.5. Self-Loosening of Fastener
13.7.6. Leakage
13.8. Load Intensifiers
13.9. Failure of Joint Members
13.10. Galling
13.10.1. Discussion
13.10.2. Removing Galled Studs
Exercises
References
Chapter 14: Self-Loosening
14.1. The Problem
14.2. How Does a Nut Self-Loosen?
14.3. Loosening Sequence
14.4. Junker's Theory of Self-Loosening
14.4.1. The Equations
14.4.2. The Long-Form Equation in Practice
14.4.3. The Equation When Applied Torque Is Absent
14.4.4. Why Slip Occurs
14.4.5. Other Reasons for Slip
14.4.6. Other Theories of Self-Loosening
14.5. Testing For Vibration Resistance
14.5.1. NAS Test
14.5.2. Junker Test
14.6. To Resist Vibration
14.6.1. Maintaining Preload and Friction
14.6.1.1. Conventional Wisdom
14.6.2. Preventing Relative Slip between Surfaces
14.6.3. Countering Back-Off Torque
14.6.3.1. Prevailing Torque Fasteners
14.6.3.2. DISC-LOCK® Washers and Nuts
14.6.3.3. In General
14.6.4. Double Nuts
14.6.5. Mechanically Locked Fasteners
14.6.5.1. Lock Wires and Pins
14.6.5.2. Welding
14.6.5.3. Stage 8 Fastening System
14.6.5.4. Huck Lockbolt
14.6.5.5. Honeybee Robotics
14.6.5.6. A-Lock Bolt and Nut
14.6.5.7. Omni-Lok Fasteners
14.6.6. Chemically Bonded Fasteners
14.6.6.1. Rust
14.6.6.2. Anaerobic Adhesives
14.6.7. Vibration-Resistant Washers
14.6.7.1. Washers That Maintain Tension in the Fastener
14.6.7.2. Toothed Washer
14.6.7.3. Helical Spring Washer
14.6.7.4. DISC-LOCK® Washer
14.6.8. Comparison of Options
Exercises
References
Chapter 15: Fatigue Failure
15.1. Fatigue Process
15.1.1. Sequence of a Fatigue Failure
15.1.1.1. Crack Initiation
15.1.1.2. Crack Growth
15.1.1.3. Crack Propagation
15.1.1.4. Final Rupture
15.1.2. Types of Fatigue Failure
15.1.3. Appearance of the Break
15.2. What Determines Fatigue Life?
15.2.1. S–N Diagrams
15.2.2. Material versus “The Part”
15.2.3. Summary
15.3. Other Types of Diagram
15.3.1. Constant Life Diagram
15.3.2. Center Portion of Constant Life Diagram
15.3.3. Approximate Constant Life Diagram
15.3.4. Endurance Limit Diagram
15.3.5. Fatigue Life Data for Fasteners
15.4. Influence of Preload and Joint Stiffness
15.4.1. Fatigue in a Linear Joint
15.4.2. Non-Linear Joints
15.4.3. What Is the Optimum Preload?
15.4.4. Fatigue and the VDI Joint Design Equations
15.5. Minimizing Fatigue Problems
15.5.1. Minimizing Stress Levels
15.5.1.1. Increased Thread Root Radius
15.5.1.2. Rolled Threads
15.5.1.3. Fillets
15.5.1.4. Perpendicularity
15.5.1.5. Overlapping Stress Concentrations
15.5.1.6. Thread Run-Out
15.5.1.7. Thread Stress Distribution
15.5.1.8. Bending
15.5.1.9. Corrosion
15.5.1.10. Flanged Head and Nut
15.5.1.11. Surface Condition
15.5.2. Reducing Load Excursions
15.5.2.1. Prevent Prying
15.5.2.2. Proper Selection of Preload
15.5.2.3. Control of Bolt-to-Joint Stiffness Ratios
15.5.2.4. Achieving the Correct Preload
15.6. Predicting Fatigue Life or Endurance Limit
15.7. Fatigue of Shear Joint Members
15.8. Case Histories
15.8.1. Transmission Towers
15.8.2. Gas Compressor Distance Piece
Exercises
References
Chapter 16: Corrosion
16.1. Corrosion Mechanism
16.1.1. Galvanic Series
16.1.2. Corrosion Cell
16.1.3. Types of Cells
16.1.3.1. Two-Metal Corrosion
16.1.3.2. Broken Oxide Film
16.1.3.3. Stress Corrosion Cracking
16.1.3.4. Crevice Corrosion
16.1.3.5. Fretting Corrosion
16.2. Hydrogen Embrittlement
16.2.1. Brittle Cracking and Fracture
16.2.2. General Description of Hydrogen Embrittlement
16.2.3. Hydrogen Damage Mechanism
16.2.4. Fracture Morphology
16.2.5. Conditions at the Tip of a Crack
16.2.6. Conditions for Hydrogen Embrittlement Failure
16.2.6.1. Root Cause and Triggers for Hydrogen Embrittlement Failure
16.2.7. Material Susceptibility
16.2.7.1. General
16.2.7.2. Defects and Other Conditions Causing Abnormal Material Susceptibility
16.2.7.3. Methodology for Measuring HE Threshold Stress
16.2.8. Tensile Stress
16.2.9. Atomic Hydrogen
16.2.9.1. Sources of Hydrogen
16.2.9.2. Internal Hydrogen
16.2.9.3. Environmental Hydrogen
16.2.10. Case-Hardened Fasteners
16.2.11. Hot Dip Galvanizing and Thermal Up-Quenching
16.2.12. Stress Relief Prior to Electroplating
16.2.13. Fasteners Thread Rolled after Heat Treatment
16.2.14. Hydrogen Embrittlement Test Methods
16.2.15. Baking
16.3. Hydrogen Embrittlement and Stress Corrosion Cracking—A Fracture Mechanics Approach
16.3.1. The Concept of KISCC
16.3.2. Factors Affecting KISCC
16.3.2.1. Bolt Material
16.3.2.2. The Environment
16.3.2.3. Bolt Strength or Hardness
16.3.2.4. Type of Electrolyte
16.3.2.5. Temperature
16.3.2.6. Bolt Diameter and Thread Pitch
16.3.3. Combating SCC
16.3.3.1. Susceptibility of the Material
16.3.3.2. Eliminating the Electrolyte
16.3.3.3. Keeping Stress Levels below a Threshold Limit
16.3.4. Surface Coating or Treatment
16.3.5. Detecting Early SCC Cracks
16.4. Minimizing Corrosion Problems
16.4.1. In General
16.4.2. Detailed Techniques
16.5. Fastener Coatings
16.5.1. In General
16.5.2. Organic Coatings
16.5.2.1. Paints
16.5.2.2. Phos-Oil Coatings
16.5.2.3. Solid-Film Organic Coatings
16.5.3. Inorganic or Metallic Coatings
16.5.3.1. Electroplated Coatings
16.5.3.2. Hot-Dip Coatings
16.5.3.3. Mechanical Plating
16.5.3.4. Miscellaneous Coating Processes
16.5.4. Composite Coatings
16.5.5. Rating Corrosion Resistance
16.5.6. Substitutes for Cadmium Plate
Exercises
References
Chapter 17: Selecting Preload for an Existing Joint
17.1. How Much Clamping Force Do We Need?
17.1.1. Factors to Consider
17.1.1.1. Joint Slip
17.1.1.2. Self-Loosening
17.1.1.3. Pressure Loads
17.1.1.4. Joint Separation
17.1.1.5. Fatigue
17.1.2. Placing an Upper Limit on the Clamping Force
17.1.2.1. Yield Strength of the Bolt
17.1.2.2. Thread-Stripping Strength
17.1.2.3. Design-Allowable Bolt Stress and Assembly Stress Limits
17.1.2.4. Torsional Stress Factor
17.1.2.5. Shear Stress Allowance
17.1.2.6. Stress Cracking
17.1.2.7. Combined Loads
17.1.2.8. Damage to Joint Members
17.1.2.9. Distortion of Joint Members
17.1.2.10. Gasket Crush
17.1.3. Summarizing Clamping Force Limits
17.2. Simple Ways to Select Assembly Preloads
17.2.1. Best Guide: Past Experience
17.2.2. Second Best: Ask the Designer
17.2.3. Unimportant Joint: No Prior Experience
17.2.4. When More Care Is Indicated
17.2.5. If Improvements Are Required
17.2.6. Selecting Preload for Critical Joints
17.3. Estimating the In-Service Clamping Force
17.3.1. Basic Assumptions
17.3.2. Combining the Scatter Effects
17.4. Relating Desired to Anticipated Bolt Tensions
17.5. Which Variables to Include in the Analysis
17.5.1. In General
17.5.2. Possible Factors to Include
17.5.3. Which Should We Include?
17.6. ASTM F16.96. Subcommittee on Bolting Technology
17.7. A More Rigorous Procedure (Final Equations, 3D Solid Modeling, FEA, and Testing)
17.7.1. The Equations
17.7.1.1. Minimum Clamping Force—Some Examples
17.7.1.2. Maximum Bolt Tension
17.8. 3D Solid Modeling
17.9. Finite Element Analysis
17.9.1. The Math
17.9.2. Analysis or Table
17.9.3. Prepare the Simulation
17.10. Physical Testing
17.10.1. Why Test
17.10.2. Fastener Test Equipment
17.10.3. Fastener Tests
17.11. NASA's Space Shuttle Preload Selection Procedure
17.11.1. Calculating Maximum and Minimum Preloads
17.11.2. Confirming the Preload Calculations
17.11.3. Discussion
Exercises
References
Chapter 18: Design of Joints Loaded in Tension
18.1. A Major Goal: Reliable Joints
18.1.1. Checklist for Reliable Bolted Joints
18.2. Typical Design Steps
18.2.1. Initial Definitions and Specifications
18.2.2. Preliminary Design
18.2.3. Load Estimates
18.2.4. Review Preliminary Layouts: Define the Bolts
18.2.5. Clamping Force Required
18.2.5.1. Minimum Clamp
18.2.5.2. Maximum Clamp
18.3. Joint Design in the Real World
18.4. VDI Joint Design Procedure
18.4.1. Terms and Units
18.4.2. Design Goals
18.4.3. General Procedure
18.4.4. Estimating Assembly Preloads: Preliminary Estimate of Minimum and Maximum Assembly Preloads
18.4.5. Adding the Effects of the External Load
18.4.6. Is the Required Force Good Enough?
18.4.7. Further Considerations
18.4.7.1. Static Strength of the Bolt
18.4.7.2. Fatigue
18.4.7.3. Bearing Stress
18.4.7.4. Shear Stress
18.4.7.5. Bending Stress
18.4.7.6. Eccentric Loading
18.4.8. Revised Bolt Specifications
18.5. An Example
18.5.1. Inputs
18.5.2. Calculations
18.5.2.1. Maximum and Minimum Assembly Preloads
18.5.2.2. Static Strength of the Bolts
18.5.2.3. Fatigue Strength
18.5.2.4. Contact Stress
18.6. Other Factors to Consider When Designing a Joint
18.6.1. Thread Strength
18.6.2. Flexible Bolts
18.6.3. Accessibility
18.6.4. Shear versus Tensile Loads
18.6.5. Load Magnifiers
18.6.6. Minimizing Embedment
18.6.7. Differential Expansion
18.6.8. Other Stresses in Joint Members
18.6.9. Locking Devices
18.6.10. Hole Interference
18.6.11. Safety Factors
18.6.12. Selecting a Torque to Be Used at Assembly
Exercises
References
Bibliography
Chapter 19: Design of Joints Loaded in Shear
19.1. An Overview
19.2. The VDI Procedure Applied to Shear Joints
19.3. How Shear Joints Resist Shear Loads
19.3.1. In General
19.3.2. Concept of Slip-Critical Joints
19.4. Strength of Friction-Type Joints
19.4.1. In General
19.4.2. Allowable Stress Procedure
19.4.3. Other Factors to Consider
19.4.4. Slip Coefficients in Structural Steel
19.4.5. An Example
19.4.5.1. Minimum Preload Required to Prevent Slip
19.4.5.2. Alternate Using the Allowable Stress Procedure
19.5. Strength of Bearing-Type Joints
19.5.1. Shear Strength of Bolts
19.5.1.1. Distribution of Load among the Bolts
19.5.1.2. Shear Strength Calculations
19.5.2. Tensile Strength of Joint Plates
19.5.3. Bearing Stress
19.5.4. Tearout Strength
19.5.5. Summary
19.5.6. Clamping Force Required by a Bearing-Type Joint
19.6. Eccentrically Loaded Shear Joints
19.6.1. Rotation about an Instant Center
19.6.2. Rotation About the Centroid of the Bolt Group
19.6.2.1. Find the Centroid of the Bolt Group
19.6.2.2. Estimating the Shear Stress on the Most Remote Bolt
19.7. Allowable Stress versus Load and Resistance Factor Design
Exercises
References
Appendix A: Units and Symbol Log
Appendix B: Glossary of Fastener and Bolted Joint Terms
Appendix C: Sources of Bolting Information and Standards
Appendix D: English and Metric Conversion Factors
Appendix E: Tensile Stress Areas for English and Metric Threads with Estimated “Typical” Preloads and Torques for As-Received Steel Fasteners
Appendix F: Basic Head, Thread, and Nut Lengths
Index