Calculating Failure Rates for Bolts

In Calculating Failure Rates for Bolts, you'll learn ...

• Bolting types and components, including washers and nuts
• Applications and advantages of bolts relative to screws, pins and rivets
• Bolting material selection, grades classification, markings and specification
• Bolt failure modes, including fatigue failure
• Method for calculating the reliability of common bolted connections by applying the concept of failure rate

Overview

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Credit: 3 PDH

Length: 53 pages

This course covers fundamental and more advanced concepts associated with bolted connections. Bolts are a specific type of fastener, just like screws, rivets, and pins. The course material is presented so that an engineer with a basic mechanics background can understand it. This foundation will then be applied to focus on calculating the failure rates based on fatigue, from dynamic or fluctuating loads.

Fatigue is commonly referred to as wear out, or wear and tear. A formal definition referenced in ASTM E1823 (Standard Terminology Relating to Fatigue and Fracture Testing) states fatigue is a process where localized and accumulating permanent damage to a structure occurs based on dynamic, alternating, or cyclical stress; after enough stress cycles, cracks may form or worse there may be a complete fracture of the structure. Dynamic or alternating loading particularly applies to bolted connections used for civil and mechanical engineering applications such as bridges, automobiles, maritime vessels, factories, and process and power plants. This course will examine a steel structure with a bolted connection for a notional steel structure that supports the weight of rotating machinery.

Bolt concepts such as nomenclature and configuration will be presented. Threads per inch, as well as thread series including coarse versus fine threads, are discussed. The course instructs on bolt markings as well as the specifications for ASTM and ISO bolts. More detailed subject matter about bolts would focus in detail on ASTM F3125 (Standard Specification for High Strength Structural Bolts).

The course material is at an introductory level, and no prior understanding of bolted connections is required. However, a general background in engineering mechanics is helpful for this course. Engineers who also are not structural or civil engineers may be interested in this course if they work with systems that require bolts and bolted connections.

Specific Knowledge or Skill Obtained

This course teaches the following specific knowledge and skills:

• Bolt concepts, nomenclature, classification, and standards, such as ASTM and ISO
• Bolted connection basics like ASTM A325 structural bolts, hex nut flanges, lock nuts, and safety wire
• Reliability Engineering and Fatigue failure theory, including the stages of failure, failure modes of a bolt, the bathtub curve, and stress versus number of cycle (S-N) graphs
• Ductile material low carbon steel behavior under tensile strain such as necking and elasticity
• Comparison of shear versus tensile strength when calculating the fatigue failure rate for a bolt
• Fatigue failure rate for a bolt based on United States Navy research and standards and derating by setting endurance stress limits order to avoid wear out and fatigue failure

Certificate of Completion

You will be able to immediately print a certificate of completion after passing a multiple-choice quiz consisting of 15 questions. PDH credits are not awarded until the course is completed and quiz is passed.