It has been selected the most industry perspective laser welding technological implementations of the welded T-joints made of fine-sheeted heat resisting steel AISI 321 by identifying the influence of technological parameters on formation quality, level of mechanical properties and structural peculiarities of the welded T-joints obtained by laser welding in different spatial positions.
Comparative studies were performed of microstructure, degree of softening, ultimate strength, crack initiation and propagation susceptibility and fatigue resistance of welded joints of wrought aluminium alloys AMg5M andAMg6M 1.8 mm thick, produced by nonconsumable-electrode argon-arc welding and friction stir welding, as well as of the levels of residual longitudinal stresses developing in them. It is shown that application of FSW enables formation of permanent joint with minimum level of stress concentration in weld-to-base metal transition areas, and allows avoiding defects in the form of pores, oxide film macroinclusions and hot cracks in welds due to metal melting and solidification in fusion welding. Intensive plastic deformation of metal results in formation of a uniform disoriented structure under the tool shoulder and in the weld nugget with grain size of 3-4 μm and disperse (not more than 1 μm) phase precipitates, and grain elongation and distortion in the direction of plasticized metal displacement occur in the adjacent areas. This leads to increase of metal hardness in the joint zone, sample ultimate strength at uniaxial tension, their fatigue strength and lowering of crack initiation and propagation susceptibility. Lowering of temperature of welded edges heating leads to lowering of maximum level of residual longitudinal stresses in welded joints by 25 %, compared to TIG welding. 16 Ref., 8 Figures.
In the work, theoretical foundations of behavior analysis of elastic bushings of modern engines high-speed elements under load were created. Several variation settings are offered. The first one of them is based on the model of a thin ring. The second model is formed on a flat setting. The third model is a three-dimensional formulation of the contact problem. It was established that during radial force loading, uneven deformation of the elastic intermediate ring occurs. At the same time, the contact zones gradually change their location in the direction of the radial force. The dependence of the radial displacement on the loading force is significantly nonlinear. It was established that the static characteristic of an elastic ring has a complex form. Unlike the traditional linear characteristic, it consists of three sections. The first one corresponds to a zero reaction to the action of the load. The second is a linear part. The third is a tough section. Thus, new formulations of the problem of determining the stress-strain state of an elastic intermediate ring, taking into account the contact interaction, have been developed. This forms, in contrast to traditional linear, significantly nonlinear models of the stress-strain state. They are more adequate and take into account factors that were not taken into account before. In particular, the clearances, tension and contact in the coupling of the elastic intermediate ring with other parts of the structure of the support of the rotor system are taken into account.
Keywords: high-speed element, elastic bushing, support, critical rotational speeds, air blower, internal combustion engine
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