Abstract
Gas turbine disks carry significant load under high temperatures and may be subject to fatigue failure. Disks contain several notches in the form of the fir tree blade attachments. Low cycle fatigue tests were performed on blunt notch compact tension specimens made from alloy 718. The results indicated that notch support needed to be incorporated not to cause an overly conservative life prediction. The notch support diminished as the plastic strain range decreased, indicating that notch support is only present in the low cycle fatigue regime. A critical distance approach was applied to account for the notch support. An equation relating the critical distance to the notch root stress was derived. The chosen life model was formulated in terms of a variation on the Smith–Watson–Topper (SWT) parameter. The modified SWT parameter taken at the critical distance was used in a life model calibrated for smooth specimens to successfully predict the fatigue life of notched specimens.
Highlights
Gas turbine disks, in the turbine section, carry significant load under intermediate to high temperatures [1]
Low cycle fatigue tests were performed on blunt notch compact tension specimens made from alloy 718
The results indicated that notch support needed to be incorporated in the lifing method not to cause an overly conservative life prediction
Summary
In the turbine section, carry significant load under intermediate to high temperatures [1]. The fir tree like blade attachments account for stress concentrations which may initiate cracks in the disk. Notches may promote crack initiation, there is a tendency for conventional lifing methods to underestimate the fatigue life of the component if the lifing method is applied using the notch root stress. The current desire to reduce conservatism in design against fatigue (especially in the energy sector) [3] calls for notch support to be investigated and incorporated in lifing methods in an industrially applicable manner. A method for incorporating notch support is applied to notched specimens made from the Ni base alloy 718 subjected to low cycle fatigue (LCF). The theory of critical distances is taken as basis for the suggested lifing method
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
