i want to know about the relationship between fatigue strength and tensile strength for thermoplastics especially PPSU (POLYPHENYLSULPHONE)@23 DEG.
The tensile strength of a material is how it resists tension and the difference between yield and failure.
The fatigue resistance is its behavior under cyclic loading which is more complicated, the amount of load and frequency makes a difference. The study of cyclic loading is “relatively” recent due to some airplanes failing due to cyclic loading.
There are text books covering this in detail.
Fatigue of plastics is strongly dependent on temperature, part surface finish, frequency of loading, etc. The results of fatigue tests are typically plotted on S-N curves – stress versus number of cycles to failure. The figure below shows S-N curves for various materials at a frequency of 30Hz.
The S-N curves should be valid for the applications at room temperature. You can relate the stress amplitude to the tensile strength of the respective material.