Fatigue Life Equation – How to Go About It?

Are you concerned about the fatigue life of your products? Do you want to ensure that your products will withstand the rigours of use and still perform as expected? If so, then you need to understand the fatigue life equation. The fatigue life equation in product development is essential in designing a product. This article will give you a better understanding of the fatigue life equation and how to calculate it.

What Is The Fatigue Life Equation?

The fatigue life equation is a mathematical equation that calculates the fatigue life for material. It is calculated by dividing the total fatigue stress (S) by the total number of cycles (N). To ensure that your product will last long enough, you must calculate its fatigue life. The equation considers the material’s yield strength, the applied stress, and the number of cycles to failure.

Mathematically, the fatigue life equation is written as:

S/N = fatigue life

How to Calculate Fatigue Life? 

Several empirical equations can be used to calculate the fatigue life of a material. Still, the most accurate method is to test the material in a laboratory under controlled conditions. To calculate the fatigue life of a material, first determine the maximum stress the material will be subjected to during its intended use. Next, select the number of stress cycles that the material will experience during its intended use. Finally, divide the maximum stress by the number of stress cycles to determine the fatigue life of the material. 

Read More: Prostate Cancer

The Parts Of Fatigue Life Equation

The fatigue life equation predicts how long a component will last before it reaches its maximum allowable stress level. This equation considers the number of cycles put through and the stress on each cycle. It also includes information about safety margins and critical speeds.

Understanding Fatigue Lives

Fatigue lives are a measure of the endurance or strength of an object. They are used in many fields and industries, including engineering and physics, where they’re considered a form of energy. It’s calculated by multiplying two values: stress life and strength lives. There are three types to consider: fatigue, material, and stressful lives. Material lives are the number of times a product can be made before it wears out. Stress lives refer to the limit at which a material will start breaking down when put under mechanical stress, while fatigue lives refer to how often the strains that cause wear will occur during its lifetime.


You can use the fatigue life equation to predict how long a machine will last before it needs maintenance. It is important to remember that this equation is not an exact science, as many factors go into it, but it will give you a general idea of how much time you have before parts start needing replacement. The equation comprises three variables: stress intensity factor (SIF), exposure time, and operating frequency. You will need to know these three variables to calculate your fatigue life expectancy.