| Summary: | This research was carried out to study the effect of loading parameter on fatigue crack growth behaviour of stainless steel 316 at room temperature using the center-crack tension M(T) specimens. The parameter involved were R-ratio and D s . For studying the effect of R-ratio, experiments were carried out with R-ratio of 0, 0.33 and 0.6 at constant D s of 100 MPa, whereas for studying the effect of D s , experiments were carried out with D s values of 100, 150 and 225 MPa at constant R-ratio of 0.1. The crack length was measured using a travelling microscope. Results showed that at a given value of cyclic stress intensity, D K the crack growth rate increased with increasing R-ratio but decreased with increasing D s . At the first stage, the value of D Kth decreased with increasing the value of R-ratio but increased as the value of D s was increased. At the linear region, the fatigue crack growth could be described with the Paris-Erdogon Power Law. The fatigue crack growth rate for various R-ratio occurred between 1x10-5 to 1x10-3 mm/cycle whereas, the effect of D s was occurred in a range of 1x10-4 to 2x10-3 mm/cycle. An increase in fatigue crack growth rate by factor 3.4 is observed at low D K of 12 MPa when R-ratio increased from zero to 0.6. At high D K values exceeding 25 MPa, it was found that da/dN converged to 3x10-4mm/cycles. The microscopic examination of the fracture surface was done using SEM. The tension fracture surface showed a ductile fracture where many microvoid coalesced and dimples were found. Fractography of the fracture surface showed striation at the second stage especially at high D K. At this stage crack occurred transgranularly with little intergranular crack but at the third stage crack occurred intergranularly
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