Most steels with ultimate tensile strengths beyond u 1400 M

Most steels with ultimate tensile strengths beyond u = 1400 MPa have fatigue limits below half the ultimate. However, a few high-strength steels (u = 1700 to 2000 MPa) have higher fatigue limits than is typical, with the values still being near the erb = 0.5u line. Speculate on how the tensile properties other than u for such steels might compare with those for more ordinary high-strength steels.

Solution

material with high tensile strength are considered to be as brittle which do not show yielding of material so it become very imporatnt to design these material with with a large safety in fatigue design. because these material are very hard so the factor which considered in fatigue design such as surface finish factor, reliabilty fator , and modifyin factor becomes less and less hence while considered in estimation of endurance strentgh it become approx. half of ultimate tensile strength.