Basics of Crack Propagation

In Basics of Crack Propagation, you'll learn ...

• The three modes of crack propagation
• Two mechanisms of crack advancement in a material
• The justification for a Crack Propagation Theory that is differentiated from the classical Stress Theory
• Standardized material testing methods for Fracture Toughness
• Practical crack propagation cases that are applicable to a large number of situations

Overview

Preview a portion of this course before purchasing it.

Credit: 2 PDH

Length: 46 pages

Whether obvious in a material or not, cracks are an inherent part of any component. This course introduces the engineer to crack propagation principles, and brings a basic understanding on how to tackle problems involving cracks.

The course presents typical crack features and some of the formulae governing crack propagation. The three modes of crack propagation and their features are presented, as defined by George Irwin a few decades ago. The two mechanisms of crack advancement in a material are described and associated material characteristics are presented for a few materials.

The justification is presented for a Crack Propagation Theory that is differentiated from the classical Stress Theory and is supported by several common cases of crack problems, with their respective formulae. Additionally, for the cases when FEA is applicable, several FEA set-up guidelines are suggested.

The course further introduces two standardized material testing methods for Fracture Toughness, the ASTM E399 and the Charpy test principles and general conclusions are mentioned to help the engineer fully understand the applicability of each test.

Going beyond presenting the theory, the course illustrates a few fundamental practical cases that are applicable to a large number of situations. The associated formulae are included, and some numerical cases are shown.

The interested reader can build on the foundations acquired in this course by consulting a list of additional related, more in-depth, topics.

This course will help design engineers, quality and forensic engineers, engineering managers and project managers who are interested in improving their understanding of Crack Propagation Theory.

Learning Objectives

Upon completion of this course, participants will be able to:

• Explain the basic crack-propagation theories associated with the three crack-opening modes and the situations in which they occur.
• Describe why classical stress theory is not applicable to cracks and how crack-propagation theories address this limitation.
• Apply FEA to crack-analysis situations, including geometry, LBCs, and meshing considerations.
• Explain how the ASTM E399 test is used to determine the fracture-critical toughness of a material.
• Describe how the Charpy test is used to evaluate ductile-to-brittle material behavior under varying environmental conditions.
• Apply stress-intensity-factor formulas to a center-cracked plate subjected to tensile loading.
• Calculate the stress intensity factor for a double-edge-cracked plate subjected to tensile loading.
• Apply stress-intensity-factor formulas to a single-edge-cracked plate subjected to tensile loading.
• Calculate the stress intensity factor for a single-edge crack in a semi-infinite plate under combined loading.
• Apply stress-intensity-factor formulas to a single-edge plate subjected to bending.
• Calculate the stress intensity factor for a center-cracked plate subjected to combined loading.
• Explain the basic steps for converting a real-world crack problem into a problem with a known solution and identifying the limitations of that approach.

Certificate of Completion

You will be able to immediately print a certificate of completion after passing a multiple-choice quiz consisting of 14 questions. PDH credits are not awarded until the course is completed and quiz is passed.