Assessment of Substrate and TBC Damage Effects on Resonance Frequencies for Blade Health Monitoring

The reliability of critical aircraft components continues to shift towards onboard monitoring to optimize maintenance scheduling, economy efficiency and safety. Therefore, the present study investigates changes in dynamic behavior of turbine blades for the detection of defects, with focus on substrate cracks and TBC spallation as they relate to vibration modes 1 to 6. Two‐dimensional and three-dimensional finite element simulation is used. The results indicate that TBC spallation reduces natural frequencies due to the ensuing hot spot and overall increase in temperature, leading to drops in blade stiffness and strength. Cracks cause even larger frequency shifts due to local plastic deformation at the crack that changes the energy dissipation behavior. Mode 1 vibration shows the largest shifts in natural frequencies that best correlate to the size of defects and their position. As such, it may be most appropriate for the early assessment of the severity and location of defects.

Estimation of Local Plastic Deformation in a Bulk of Polycrystalline Materials

The article deals with the local plastic deformation analysis after cold forming. The technology of drawing seamless steel tubes was used to obtain cold-formed samples. The tubes were manufactured by a Tinius Olsen 300ST tensile tester with a 6 ° and 12 ° die drawn without and with an inner mandrel. Based on orientation size recalculated by stereology and applying Monte Carlo method a mathematical conversion model was developed. Implemented model together with surface measurements and structure characteristics were used to get the orientation to the size of the deformation. Thus, the actual (logarithmic) deformations and local stresses were determined. Comparison of experimentally measured values of the actual local plastic deformation with the deformation calculated found on the model simulation in the Deform program defined the significance of the differences assessed by means of a statistical T-test. All differences in the values of the local plastic deformation with respect to the position were evaluated as statistically insignificant and therefore the difference between the experimental calculation and the simulation is random.

The Peculiarities of Mass Transfer in the Surface Layer of Materials under Extreme Heating

Possible causes of mass transfer acceleration of carbon atoms and alloying elements in the surface layers of steels and alloys under extreme heating, under pulsing laser irradiation in particular, are considered. The research shows that the anomaly accelerated mass transfer, including diffusion in particular, in steels and alloys under fast laser heating has a cooperative character and is a result of a simultaneous action of several processes of different physics. It is proved that the carbon atoms mass transfer parameters and alloying elements depend on the scale and the level of emerging tension, relaxation of which goes along with a local plastic deformation, and occurrence of increased number of linear defects in crystal structure.

IMPROVING THE MECHANICAL PROPERTIES OF Al-Cu-Mg-Mn ALLOY TUBES THROUGH PLASTIC DEFORMATION

The effect of plastic deformation upon the grain structure and mechanical properties of Al-Cu-Mg-Mn alloy tubes under upsetting was investigated. It was found that plastic deformation techniques such as cold upsetting can overcome the disadvantages of the cutting process, such as the anisotropy of the original material, no grain structure, and not high mechanical properties, while also improving the mechanical properties of the product in local plastic deformation zones by changing the grain and fiber structure of the material. This article presents the results of our research and evaluates the increase of material durability in the tubes’ deformation zones compared with the initial state. In this study Al-Cu-Mg-Mn alloy material had been cutting with turn machine and plastic deformation by upsetting. Microstructures and hardness variations of cut surfaces that are obtained with different processes have been investigated.

THE ROLE OF MASS-TRANSFER IN THE MATERIALS SURFACE LAYER STRUCTURING UNDER EXTREME HEATING

Possible causes of mass transfer acceleration of carbon atoms and alloying elements in the surface layers of steels and alloys under extreme heating, under pulsing laser irradiation in particular, are considered. The research shows that the anomaly accelerated mass transfer, including diffusion in particular, in steels and alloys under fast laser heating has a cooperative character and is a result of a simultaneous action of several processes of different physics. It is proved that the carbon atoms mass transfer parameters and alloying elements depend on the scale and the level of emerging tension, relaxation of which goes along with a local plastic deformation, and occurrence of increased number of linear defects in crystal structure. Experimental and theoretical studies have found that with the temperature of the laser heating lowered along the depth of the irradiated areas the mechanism of mass transfer will change as follows: atoms move in the fused spot area under the influence of Marangoni effect; a contact melting and liquid-phase diffusion occur at the boundaries with the solid matrix; Soret diffusion under the action of local plastic deformation also occur; atoms move along the irradiated zone in an atoms "drift" mechanism within the area of moving dislocations.

Methodology for the Identification of Nucleation Sites in Aluminum Alloy by Use of Misorientatation Mapping

The fabrication of semi-finished hot and cold rolled sheets includes a complex evolution of both microstructure and texture to meet the demanded mechanical properties and suitable formability characteristics. The desired mechanical properties along with the optimum grain size can be obtained through the control of both recovery and recrystallization processes. This work examines the effect of recovery and recrystallization on the resulting crystallographic texture and on the local plastic deformation. A processing approach for EBSD-KAM (Electron Back Scatter Diffraction—Kernel average misorientation) evaluation is suggested with the purpose of effectively evaluating all the possible misorientation angles in-between the grains and of observing the recovery phenomenon from a different point of view. The results showed that although texture components did not alternate significantly during recovery, the fraction of sub-grain boundaries was increased indicating the completion of recovery at the selected temperature exhibited a maximum value of 90%. The initiation of recrystallization was illustrated by a different aspect, underlying newly formed grains and points which exhibited high misorientation angle, critical for the evolution of the recrystallization process and texture evolution.

ПРОГНОЗИРУЕМЫЕ ЭФФЕКТЫ УПРОЧНЕНИЯ АЛМАЗНЫМ ВЫГЛАЖИВАНИЕМ ДЕТАЛЕЙ ПОЛУЧЕННЫХ С ПОМОЩЬЮ СЕЛЕКТИВНОГО ЛАЗЕРНОГО СПЕКАНИЯ

The analysis of the possibility of expanding the scope of selective laser sintering technology has been made for the production of parts of short-range gas turbine aircraft engines due to the strengthening of stress concentration points by local plastic deformation by diamond smoothing. The technical, economic, and social effects of the application of this technology have been considered.The stress-strain state of complex-shaped thin-walled parts such as a disk and a monowheel of a short-life aircraft engine during their manufacture according to the traditional techniques from the compact materials VT8 and INCONEL 718 and according to the alternative technology from the materials Ti45Al3Nb (SLS) and INCONEL 718 (SLS)has been calculated and studied. The analysis of stress fields in stress concentration zones is carried out. Estimates are obtained from the static strength reserves of these parts during delamination and rupture of the force layers. A comparison of the obtained reserves of static strength for various places of stress concentration of parts made of compact and non-compact materials has been performed.The effectiveness of the use of alternative technology has been estimated by calculating the unit cost of production in mass production with a production program of 1000 pcs. The economic effect of the use of selective laser sintering and hardening technology in the manufacture of a part of a disk made of INCONEL 718 non-compact material (SLS) is estimated in comparison with the basic technology for the production of a part made of INCONEL 718 compact material in mass production. The comparison of the required capital investments for basic and alternative technology is carried out. The impact of alternative technology on the social and environmental spheres of human life has been assessed.Conclusions have been drawn about the prospects of introducing the technology of local plastic deformation by diamond smoothing to expand the scope of using SLS in the production of parts for the domestic aviation and aerospace industries and society, as well as its potential for other industries.

On the Applicability of Stereological Methods for the Modelling of a Local Plastic Deformation in Grained Structure: Mathematical Principles

Analysis of systems and structures from their cross-sectional images finds applications in many branches. Therefore, the question of content, quantity, and accuracy of information obtained from various techniques based on cross-sectional views of structures is particularly important. Application of conventional techniques for two-dimensional imaging on the analysis of structure from a cross-sectional image is limited. The reason for this limitation is the fact that these techniques use a fixed cross-sectional plane and therefore cannot check the 3D structural changes caused by deformation. Geometric orientation of a grained structure must be considered when data, scanned from a cross section, is processed in order to obtain information about local deformation in this structure. The so-called degree of structure orientation in 3D can be estimated experimentally from the cross-sectional image of the structure by the statistical (Saltykov) method of oriented testing lines. Subsequently if the correlation between orientation and deformation were to be known a detailed map of local deformation in the structure could be revealed. Unfortunately, exact theoretical works dealing with the assessment of local deformation by means of change of structure orientation in 3D are still missing. Our work seeks to partially remove this shortcoming. In our work we are interested in how the transformation of the image of a grained structure in a cross-sectional plane reflects structure deformation. An initial shape of grains is assumed which is transformed into a deformed shape by analytic calculation. We present brief mathematical derivations aimed at the problem of single grain-surface area deformation. The main goal of this work led to the design of a computationally low consuming procedure for quantification of local deformation in a grained structure based on the distortion of the image of this structure in a cross-sectional view.