Papers by Keyword: Substructure

Abstract: The results of the microstructure and hardness investigations of the Cu-0.8Cr alloy after application of severe plastic deformation (SPD) implemented by rolling with the cyclic movement of rolls (RCMR) are presented in this paper. Performed substructure investigations showed that using the RCMR method can refine the microstructure of Cu-0.8Cr alloy to the ultrafine scale. The structure of the Cu-0.8Cr alloy was analyzed using light microscope (LM) and scanning transmission electron microscope (STEM). The quantitative studies of the substructure was performed with "MET-ILO" software, on the basis of images acquired on STEM microscope.

Abstract: Current research in the field of iron aluminides are directed towards to understand the structural phenomena occurring during plastic deformation of these alloys. The obtained results of the study and collected informations will be used to determine the description of the structural changes taking place during hot deformation of Fe ̶Al alloys. The article presents the results of the study of the alloy FeAl28Cr5 deformed by hot torsion in temperature range of 800÷1100^°C and a strain rate of 0.1 s^-1. The analysis of the structure of the alloy FeAl28Cr5 allowed to reveal changes caused by dynamic processes of deformation. The results of torsion tests show the possibility to obtain a fine-grained structure with of parameters of the processes (T=1000^°C, 1100^°C) and strain of ε=40. After deformation at strain of (ε=40) the structure consists of fine grains with a misorientation angle higher than 15^°, and the average grain size diameter D=28.5 micrometers. Deformation at a temperature of T=1000^°C and 1100^°C is accompanied by superplastic flow effect.

Abstract: For the prestressed substructure analysis, the existing CMS super-element methods are only suitable for the model that relatively simple structure, less meshing and small number of nodes. Since the complex structure and more mesh division of an arbitrary large model such as a mistuned bladed disk system, it is more time-consuming for the dynamic characteristics analysis. Because of above shortcoming, an approximate analysis method is presented, it is called fixed interface prestressed-free interface CMS super-element method. The accuracy of this method is predicted by the example. The results showed that the dimensionless dynamic frequency maximum relative error of system is 3.072215%, which can be to meet the requirement of accuracy.

Abstract: The paper presents X-ray diffraction and scanning electron microscope analyses, and durometer measurements used to investigate the structural properties and phase composition of nitride layers of type 20Kh13 mild steel. A method of nitriding by low-pressure arc discharge was applied along with the combined surface treatment including ultrasonic finishing and nitriding. It was shown that within the close-to-critical temperature range starting from 200oС, the nitride layers was formed on the surface of type 20Kh13 mild steel. The ultrasonic pre-treatment shown its effect on the steel nitriding that increased the amount of nitride phases and the value of microharness on the steel surface.

Abstract: Building claddings still contains some technologically complicated details. The paper deals with modern diagnostics methods and possible solutions to eliminate energy leak.

Abstract: Substructure of offshore modular drilling rig has complex loading. It is necessary that a 3D finite element analysis has been conducted by using finite element software for substructure. The distributions of integrated displacement and stress have been obtained. The results show that the axial strength and stiffness of the substructure are sufficient. The relevant evaluation methods were summarized and integrated into the finite element software, and the command flow program of post-processing is written. Through post-processing graphical display, the carrying capacity of substructure is presented. The results show that the carrying capacity of substructure can meet the requirements in the combination condition which contains the maximum rotary load and the maximum setback load. This research method can provide pertinent reference for carrying capacity assessment of steel structure, and have some practical significance for field operation.

Abstract: The paper aims to study the influence of high temperature processing on the substructure of laser shock processed titanium alloy. The titanium alloy specimens were first treated by laser shock processing (LSP), then treated at 700°C for three hours and air cooled to the room temperature to investigate the influence of the high temperature processing. To evaluate such influence, the hardness and substructure on the surface were investigated by micro hardness tester and transmission electron microscope (TEM), respectively. Results show that after three times LSP, the hardness of TC11 alloy was improved by 30.9%. The cause of such an improvement in hardness is that the crystal grains in the surface layer under the shock wave stress were strongly deformed, causing a dynamic recrystallization. The substructure is mainly twin crystals, highly tangled and dense dislocations. After high temperature processing in vacuum, the average hardness is decreased by 12% compared to that of the specimens after LSP. And the substructures are mainly small dislocation, nanocrystalline.

Abstract: This paper proposes a methodology on simultaneous identification of substructure excitation and damage. Structural damages are simulated by virtual distortions which are computed together with unknown excitations using the measured responses through the intact isolated substructure model; the damage extent and type is then recovered by a comparison of the virtual and actual distortions. Unknown factors are reduced greatly which allows the method to be applied on practical complex structure. The computational cost is cutoff sharply. A damaged nonlinearity aluminum beam is used in the experimental verification. Both load and damage are successfully identified.

Abstract: Dynamic substructure method has been widely used in analyzing the torsional vibration characteristics of multi-shaft transmission. However, the existing literatures extract substructures of the multi-shaft transmission by treating its gears and shaft as several rotors, resulting in complex displacement coordination relationships and making it difficult to build dynamic model for the whole system. In this paper, a new method to extract substructures of the multi-shaft transmission is proposed when analyzing its torsional vibration characteristics using the dynamic substructure method. The proposed method avoids analyzing the displacement coordination relationships for the gear meshing, making it easier and more effective to establish the dynamic model for multi-shaft transmission.

Abstract: The fatigue characteristic of 2124 aluminum alloy in T851 condition was investigated by means of scanning electron microscopy (SEM) and transmission electron microscope (TEM). And the result shows that, the fatigue life is closely related to the thickness of plates, this is because that different thickness of plates results in the variation of grain size, grain boundaries and substructures of alloy, which thus influence the fatigue behavior of 2124-T851 alloy. The number of grain boundaries along the propagation direction of cracks and the amount of substructures after heat treatment increase with the decline of thicknesses of 2124 alloy plates, while the grain size is reverse. However, no obvious size and dispersion changes for the precipitates. Comparatively, the fatigue resistance performance of 30mm thickness plate is better than the 40mm and 55mm thickness plates, which is due to the more profitable grain size, grain boundary and substructure.