How do you incorporate fatigue analysis into your design optimization and decision making process?

1 Why fatigue analysis matters

Fatigue analysis is the study of how materials and structures behave under repeated or fluctuating stresses, and how they may fail over time due to fatigue damage. Fatigue damage is the accumulation of microscopic cracks that grow and coalesce until they cause a macroscopic failure, such as a fracture or a rupture. Fatigue failure can occur at stress levels below the static strength of the material, and can be influenced by factors such as frequency, amplitude, mean stress, stress concentration, temperature, corrosion, and loading history. Fatigue analysis can help you predict the fatigue life of your design, identify the critical locations and parameters that affect fatigue performance, and optimize your design to reduce fatigue risks and improve reliability.

2 How to perform fatigue analysis

To perform fatigue analysis, you need to have a stress analysis model of your design, such as a finite element model, that can capture the stress distribution and variation under different loading scenarios. You also need to have a fatigue model that can relate the stress state to the fatigue life, such as a S-N curve, a strain-life curve, or a fracture mechanics model. Depending on the complexity and accuracy of your fatigue model, you may need to have additional inputs such as material properties, fatigue parameters, crack growth rate, and stress intensity factor. You can use software tools or analytical methods to apply your fatigue model to your stress analysis model, and obtain the fatigue life or damage for each element or node of your design.

3 How to interpret fatigue results

Once you have the fatigue results, you need to interpret them in a meaningful way for your design optimization and decision making process. You can use various techniques to visualize and analyze your fatigue results, such as contour plots, histograms, scatter plots, fatigue diagrams, and fatigue maps. You can also use statistical methods to estimate the probability of failure, the reliability, and the confidence interval of your fatigue results. You can compare your fatigue results with your design requirements, such as the allowable fatigue life, the safety factor, or the target reliability. You can identify the regions or components that have the highest fatigue risk, and the factors that contribute to the fatigue damage, such as the stress level, the stress gradient, the stress ratio, or the load spectrum.

5 How to validate your design for fatigue

After you have optimized your design for fatigue, you need to validate your design by testing it under realistic conditions and comparing the test results with your fatigue predictions. You can use experimental methods, such as fatigue testing, crack growth testing, or fracture testing, to measure the fatigue life or damage of your design under controlled or simulated loading. You can also use field methods, such as strain gauges, accelerometers, or acoustic emission sensors, to monitor the fatigue behavior of your design under actual service loading. You can use validation methods, such as correlation analysis, error analysis, or uncertainty analysis, to assess the agreement and discrepancy between your test results and your fatigue predictions, and to evaluate the accuracy and reliability of your fatigue analysis.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?