fatigue behavior of 4340 steel at room and elevated temperatures: correlating fatigue and tensile testing data

In this study, an existing approach for estimating fatigue life using tensile data was extended and applied to 4340 steel under different temperature. the s-n and strain-life curves were plotted at 25, 200, and 350 ˚c. the basquin and coffin-manson equation constants were determined based on the corrected true fracture stress and strain values. moreover, the b constants were approximated as -0.065, -0.072, and -0.073 at 25, 200, and 350 ˚c, respectively. this was achieved by setting the alternating stress equal to the fatigue limit in an infinite number of cycles when b leveled off. the transition fatigue life of 1000 cycles was considered for 4340 steel to determine the c constants, which were determined to be -0.69, -0.7, and -0.699, at 25, 200, and 350 ˚c, respectively and the strain-life curves were plotted. comparison of s-n curves obtained from both fatigue and tensile data revealed strong agreement, indicating that the tensile test is a simple and cost-effective method capable of providing a quick estimate of high- and low-cycle fatigue behavior and serving as a suitable alternative to conventional fatigue testing.