Who is considered the father of fatigue testing?

August Wöhler, a German engineer, is considered the father of fatigue testing. During the 1850s he performed systematic laboratory fatigue tests on rail axles under repeated stresses, developing the stress versus life (S-N) diagram. He demonstrated that fatigue life decreases with higher stress amplitudes and introduced the concept of an endurance limit — a stress level below which specimens would not fracture. He also established that cyclic stress range is more important than peak stress in driving fatigue failure.

What is the difference between Safe Life and Damage Tolerance design?

Safe Life design requires testing and analysis to ensure a component will not fail within a specified service period under given operating conditions, with a safety factor added to prevent catastrophic failure — typically resulting in heavier and more conservative components. Damage Tolerance design instead sizes a component to a specific life based on crack growth prediction methods, allowing for the presence of flaws and managing their growth to an acceptable size before failure. Both approaches are used in fatigue design depending on the application and industry requirements.

What is the difference between high cycle and low cycle fatigue?

High cycle fatigue involves large numbers of cycles — typically millions — at stress levels that produce little or no plastic deformation. Low cycle fatigue involves far fewer cycles but with local stresses far in excess of yield, where plastic strain ranges drive damage. Useful methods for analyzing low cycle fatigue were first developed by Langer, Coffin, and Manson in the 1950s and 1960s. Pressure vessels and piping typically operate in the low cycle regime, which is why ASME Section III and Section VIII fatigue design procedures are based on strain-controlled testing rather than nominal stress.

How did crack growth prediction methods develop?

In the 1960s, P.C. Paris proposed methods for predicting the rate of growth of individual fatigue cracks, demonstrating the relationship between crack length change and the number of load cycles. This established fracture mechanics as a foundation for Damage Tolerance design. During the 1980s, Brown and Miller investigated multiaxial fatigue, and the small crack problem was identified — small cracks were found to grow faster than longer cracks under the same driving forces, adding complexity to life prediction methods. Fatigue crack growth research has continued to evolve to address environmental effects, high-temperature conditions, and complex loading scenarios.

How did fatigue analysis become incorporated into the ASME Code?

The ASME Boiler and Pressure Vessel Code was among the first standards organizations to explicitly address fatigue life in design. Fatigue design procedures for low cycle applications were developed in the Naval Nuclear Program in the late 1950s and early 1960s, with contributions from Dr. William O'Donnell, Bernie Langer, W.E. Cooper, and James Farr — work that became known as SDB-63. These procedures were first incorporated into ASME Section III (Nuclear Facility Components) and subsequently into Section VIII Division 2, where they remain the basis for pressure vessel fatigue evaluation today. Dr. O'Donnell served as Chairman of the ASME Subgroup on Fatigue Strength for several decades and has published numerous papers advancing fatigue and fracture design methods.

Where did the history of fatigue analysis originate?

The history of fatigue analysis originated with investigations into the catastrophic failure of rail axles in the early 19th century. One of the first documented fatigue investigations was performed by German mining engineer W.A.S. Albert in 1829, who conducted repeated loading tests on hoist chains. These early studies established that failures occurred at geometric discontinuities such as axle shoulders, and that eliminating large stress concentrations helped reduce failures — leading to the introduction of the term 'fatigue' to describe failures from repeated loading.

History of Fatigue Analysis

The fatigue design life evaluation procedures in Section III of the ASME Boiler and Pressure Vessel Code were originally developed in the U.S. Naval Nuclear Program. Those involved included Dr. Bill O’Donnell, (Bernie) Langer, W.E. (Bill) Cooper and James (Jim) Farr – who, in the late 1950’s and early 1960’s developed the initial formulation of this technology in the Tentative Structural Design Basis for Reactor Pressure Vessels and Directly Associated Components, which became known as “SDB-63.”

Section III of the ASME Code “Vessels in Nuclear Service” was the first to include specific Code rules to prevent low cycle fatigue failure. Its first edition was published in 1963; Section VIII, Division 2, “Alternate Rules for Pressure Vessels” followed in 1968.Our company President, Bill, Sr. began his career at Westinghouse/ Bettis in the Naval Nuclear Program under Admiral Rickover. For several decades, he served as the Chairman of the ASME Subgroup on Fatigue Strength, and has published numerous papers on design, fatigue and fracture.

O’Donnell Consulting Performs Engineering Design and Analysis – including Vibration & Fatigue Analysis on Components including Pressure Vessels and Heat Exchangers.

Description of FEA – Finite Element Analysis

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Description of FEA – Finite Element Analysis

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