How are turbine blades attached to turbine discs?
A series of grooves or notches, conforming to the blade root design, are broached in the rim of the disk. These grooves allow attachment of the turbine blades to the disk; at the same time, space is provided by the notches for thermal expansion of the disk.
What material is used for turbine blades?
Modern turbine blades often use nickel-based superalloys that incorporate chromium, cobalt, and rhenium. Aside from alloy improvements, a major breakthrough was the development of directional solidification (DS) and single crystal (SC) production methods.
What is shroud in gas turbine?
Gas turbine blades comprise blade shrouds in order to control and minimise leakage flow between blade tips and stator as well as to limit vibration amplitudes. A further mismatch results from deformations of the shroud platform during turbine operation due to thermal and mechanical loading.
Why are turbine blades shrouded?
The turbine blades may have shrouds at the tips of the blades opposite to the roots. Shrouds are material added to the tips of the blades. The shrouds extend in a plane generally perpendicular to that of the airfoil portion. Shrouds reduce tip leakage loss of the airfoil portion of the blade.
How are single crystal turbine blades produced?
A common method is the Bridgman method to grow single crystals. In this method a casting furnace is used for crystal growth. In this process, a mould must first be made of the blade. Molten wax is injected into a metallic mould of the desired turbine blade and left to set and take the form of the turbine blade.
What is turbine blade creep?
Creep failure is one of the most important failure modes of turbine blade. Creep is the progressive time-dependent inelastic deformation under mechanical load and high temperature.
What does creeping mean?
: developing or advancing by slow imperceptible degrees a period of creeping inflation.
What is creep rupture test?
Accredited Testing of Metals. The creep test, also called a creep rupture test, shows deformation in a metallic material at temperatures that are generally elevated and under a constant load over time.
How is creep test performed?
Creep testing is conducted using a tensile specimen to which a constant stress is applied at a constant temperature, often by the simple method of suspending weights from it. The test is recorded on a graph of strain versus time. 69), the material increasing in length in the direction of the applied stress.