Fatigue Assessment

This one-day course combines lecture content with guided workshops. It is designed to take design engineers through the process of performing fatigue assessments to evaluate how a design will perform under cyclic loads.

On completing this course, users will have a good understanding of the fundamentals of what causes fatigue failure, why it is important to consider, and how to predict it. Delegates will learn how to deal with complex variable amplitude and non-proportional loads covering both high cycle fatigue and low cycle fatigue approaches. Then finally, how finite element techniques can be used in combination with these fatigue calculations to ensure the design achieves its design life.

1 day course with guided workshops:

Module 1 – Basics of Fatigue

Delegates start with a discussion about what causes fatigue failure, why it is important to consider, and how to predict it. This is followed by the first workshop, where the basics of fatigue life prediction are introduced. An explanation will be given of the stress versus number of cycles to failure (SN) curves for various materials together with high and low cycle fatigue concepts.

Module 2 – Stress Life Approach

Further important fatigue assessment concepts are introduced to account for mean stress, stress combinations, and certainty of survival. Understanding these parameters will allow you to more accurately predict your design's fatigue life to ensure it meets its intended design life. This module will focus on the high cycle fatigue approach.

Module 3 – Stress Life Approach – Variable Amplitude Loading

This module introduces methods for calculating fatigue damage using Palmgren-Miner’s rule and the Rainflow cycle counting method for fatigue life predictions for structures under variable amplitude loadings.

Module 4 – Stress Life Approach – Non-Proportional Loads

In the real-world, non-linear structural behaviour with alternating loads creates conditions where we cannot assume a simple proportional relationship between the load and stress. In this module, delegates will learn how to calculate the stress range for these real-world conditions.

Module 5 – Fatigue Assessment using FEA

Using these fatigue calculation methods and concepts, we will use finite element techniques as a basis for these calculations. Determining peak stresses in parent material or welded joints using FEA can be challenging due to stress singularities. The methods for extracting peak stresses in these complex situations will be presented. Methods including hot-spot and notch stress from various design codes such as PD 5500, EN 13445 and DNV-RP-C203 will be covered.

Module 6 – Strain Life Approach

Often stress concentration effects can cause plastic strains to develop. In these situations, we need to adopt a strain life and low cycle fatigue approach to calculating fatigue life.