Evaluation of equi-biaxial fatigue of stainless steel by the pressurized disc fatigue test

• The pressurized disc fatigue test technique was applied for equi-biaxial fatigue.
• Biaxial fatigue lives of stainless steel were longer than uni-axial fatigue.
• Equi-biaxial condition increased the fatigue limit for the equivalent strain range.
• Equi-biaxial condition is not necessary to be considered in design fatigue curve.

The pressurized disc fatigue (PDF) test technique was employed to obtain fatigue lives of Type 316 stainless steel under equi-biaxial stress conditions. In the PDF test, a disc-type specimen was subjected to the cyclic bulge test. The biaxial fatigue lives were successfully obtained by the PDF tests, and they were longer than those obtained by the uni-axial and plate bending fatigue tests under the same equivalent strain range. Observations of crack initiation and growth behavior during the PDF test revealed that the relatively large size of the disc-type specimens had only a minor influence on the fatigue lives. Finite element analysis results showed the PDF test was valid for evaluating the fatigue lives under equi-biaxial conditions. It was concluded that the influence of equi-biaxial condition was not necessary to be considered in the design fatigue curve.