Finite Element Analysis Of Mechanical Properties Of Nickel-base Single Crystal Structures Based On Crystal Plasticity Theory

Finite element simulations have been carried out to study the elastic-plastic and creep responses of single crystal structures. The models included circumferentially notched bars and plates containing hole(s) which can simulate air-cooled blades. The vibration character of single crystal blade has also been analyzed. All the calculation parameters were chosen from the nickel-base single crystal DD3. In order to perform temperature-gradient experiment, the high-temperature testing machine has been improved. They are as follows:1. Different U-type and V-type notched bars were investigated with tensile orientation [001] using the finite element code ABAQUS. The von Mises stress characteristics and resolved shear stress distributions of slip systems were given. The results show that the notch size has strong influence on the resolved shear stress. To the two types of notches studied, the resolved shear stress increases with the decreasing of notch radius, and so does the resolved shear stress along the circle of the specimens. The activated slip systems in the notch section are different for different notch .2. Seven U-type and V-type circumferentially notched specimens have been creep numerical simulated under tensile orientation [001] at 950 °C with the software MARC. The creep lifetime including circumferentially notched and smooth specimens was investigated based on the maximum shear stress amplitude. The results show that the notch size has strong influence on stress distributions and lifetime. The resolved shear stresses increase with notch radius increasing. For the same net-section stress, the notched specimens have a longer lifetime than of the smooth one.3. A plate containing a hole was used to simulate gas turbine blade with cooling holes. Numerical calculations with crystal plasticity theory have been performed to study the elastic-plastic stress field near the hole under tensile loading. Two crystallographic orientations, [001] and [111], were considered. The distributions of von Mises stress and resolved shear stresses (RSS) of the 12 octahedron slip systems were given. The results show that the crystallographic orientation has remarkable influence on both von Mises stress and RSS distributions. The elastic stress distributions near the hole are similar for both orientations, though the stress levels are different. The RSS distributions around the hole are different between the two orientations, which leads to the different activated slip systems.So the deformed shape of the hole in [001] orientation differs from that in [111] orientation.4. Thin-walled plates with small holes were used to simulate gas turbine blades with cooling holes. The effect of cooling holes on stress-rupture properties of cooling gas turbine blades were investigated by finite element method. The creep parameters in crystallographic orientations [001] and [111] were chosen from nickel-base single crystal superalloy DD3 at 950℃. The numerical results show that the cooling holes cause high stress concentration and the creep life of the specimens is greatly influenced by the holes. The number of the cooling holes has notable influence on the lifetime. The cooling holes have larger influence on the lifetime in [001] orientation than that in [111] orientation. All the calculations were performed with the finite element code MARC with a user subroutine.5. The vibration characteristics of single crystal blade were simulated using the finite element code MARC. The influences of crystallographic orientation, temperature and rotating speed were considered. The results show that the natural frequency of crystallographic orientation [111] is larger than that of [001]. The crystallographic orientation has greater influence on the high order natural frequencies than low order ones. The natural frequencies increase with the decreasing of temperature and increasing of rotating speed respectively. The influence of rotating speed on natural frequency in orientation [001] is greater than that in [111]. At working state, rotating speed influe...