What is Fatigue Failure in Welding?

When a material is subjected to repeated or alternating stresses below its ultimate tensile strength, cracking or breaking of the material may occur. This is known as fatigue failure. Fatigue failure in welding can be caused by many factors, including:

improper weld design,
incorrect welding procedures,
poor workmanship,
and inadequate quality control.

What are the two basic components of fatigue on a weld?

There are two types of fatigue failure:

Localized Fatigue Failure – This type of fatigue failure occurs when stresses are concentrated in a small area, causing the material to crack or break at that point.
Generalized Fatigue Failure – This type of fatigue failure occurs when stresses are distributed over a larger area, causing the material to crack or break at multiple points.

Many factors can contribute to fatigue failure in welding, but some of the most common are listed below:

Improper Weld Design – If a weld is not designed properly, it may be susceptible to fatigue failure. Some common design flaws that can lead to fatigue failure include incorrect joint configuration, improper weld size, and incorrect welding procedures.
Incorrect Welding Procedures – If welding procedures are not followed correctly, it may lead to fatigue failure. Some common procedural errors that can cause fatigue failure include improper electrode selection, incorrect weld parameter settings, and inadequate pre-weld and post-weld heat treatment.
Poor Workmanship – Poor workmanship can also lead to fatigue failure. Some common errors that can result in poor workmanship include improper weld preparations, incomplete fusion, and inadequate penetration.
Inadequate Quality Control – If proper quality control measures are not in place, it may lead to fatigue failure. Some common QC errors that can cause fatigue failure include incorrect welding parameters, lack of proper inspection, and inadequate repair procedures.

How to prevent fatigue failure?

Fatigue failure in welding can be prevented by following proper design, welding, and quality control procedures. If you are unsure of how to properly design or weld a component, it is best to consult with a professional engineer or certified welder.

What is fatigue failure explained?

When a material is subjected to repeated or alternating stresses below its ultimate tensile strength, cracking or breaking of the material may occur.

Fatigue failure examples

Some examples of fatigue failure are:

A welded joint that has been incorrectly designed, welded, or inspected.
A component that has been improperly heat treated.
A part that has been incorrectly machined.

Weld fatigue calculation example

The following is an example of how to calculate weld fatigue:

If the material has an ultimate tensile strength of 100 MPa and a yield strength of 50 MPa, the material can withstand maximum stress of 100 MPa before it will fail.
If the material is subjected to a stress of 50 MPa, the material will not fail immediately.

However, if the material is subjected to a stress of 50 MPa for a period of time, the material will eventually fail.