With the purpose of improving the fatigue assessment processes in different components, the Metal Digital Manufacturing Joint has developed the stiffness method to evaluate the fatigue resistance of components, specifically additive manufacturing products, in a more optimized way, reducing time, resources, and number of tests. Milad Bemani, PhD student at UPC and RMIT universities and a researcher at Eurecat, gives us the keys to understanding the advantages of the new fatigue assessment method.
What is the stiffness method?
The stiffness method is a novel rapid fatigue testing method to have a first estimation of the fatigue limit and the fracture behavior of metal sheets and AM parts based on measuring the changes in the stiffness and plastic strain in a stepwise loading test using available laboratory equipment such as an extensometer and conventional fatigue testing machine.
Why fatigue evaluation of components is harder than specimens?
Due to the complex stress conditions in different sections of the component during the test, a high number of required tests, test setup and fixtures, and complexity in analyzing the results, fatigue evaluation at the component level tends to be harder than specimens.
Why is it important to use rapid fatigue testing methods for components?
It is beneficial to employ rapid fatigue test methods to reduce the time, resources, and number of tests required for a full fatigue investigation to have a deep understanding of the fatigue mechanism and fatigue resistance. This data can help manufacturers initially to understand the effect of different parameters on lowering fatigue performance and ultimately try to improve the dynamic mechanical properties of the components.
Rapid Fatigue Testing of AM components- JRU
How did we test the fatigue demonstrator using the stiffness method?
Topology optimization was used to obtain the geometry and design the required fixture. Digital image correlation (DIC), extensometer, and displacement of the machine were employed to measure the plastic strain and stiffness changes during the test and ultimately the fatigue limit was calculated based on the same approach used for as-built specimens. Scanning electron microscopy (SEM) fractography was performed to investigate the fatigue mechanism and origins, and finite element method (FEM) simulation by Ansys software was utilized to obtain fatigue limit stress level.
How much time and resources were saved using a rapid fatigue approach?
This is one of the great achievements we have delivered: using the stiffness method, we reduce the time and resource consumption and number of specimens/components by about 90 to 95% with results deviating less than 10% from the conventional fatigue tests. Using only 2-3
specimens/components, tested in one day!
Who benefits from the rapid fatigue evaluation?
Several industrial sectors that employ AM products such as aerospace, automobile, and energy industries, researchers, and academic and technological centers can benefit from this novel and reliable rapid fatigue test method.
However, we believe that developing rapid fatigue test methods such as the stiffness method will be beneficial to society as a whole thanks to its reduction of energy, time, and resource consumption together with manufacturing components with higher quality and properties.
