Fatigue test
Material fatigue under cyclic loadIn the fatigue test, material fatigue is evoked through a cyclic load with corresponding test frequency. This may involve a pulsating load test in tension or compression as well as an alternating load test with tension and compression components.
Material failure in fatigue testing often occurs well below the static strength limits.
Results from fatigue tests are commonly presented in the form of stress-load cycling diagrams. Here the number of cycles to specimen break is plotted against the amplitude of the cyclic stresses.
On one hand, fatigue tests are used for characteristic value determination and on the other to determine fatigue life.
Common fatigue tests Characteristic values Material fatigue Testing machines Other tests
Material Fatigue
Material fatigue is described as the damage or failure of a material or component under time-varying, frequently repeated stress.
Material fatigue is caused by plastic deformation, which in its smallest form is called microplastic deformation.
Investigation of many cases of damage lead to the following findings:
- Components that have been in use for some time without any problem, can suddenly fail.
- The failure is not caused by one single overload.
- The failure occurs well below the static strength limits.
- The load varies over time and is often repetitive.
The fatigue life of cyclically stressed components is limited.
