Abstract
The design of the hydraulic drive, which ensures the reciprocating motion of the knife of uprooter’s cutting bracket, is improved. This technical solution increases the productivity of the uprooter used during infill construction.
The design of the hydraulic drive, which ensures the reciprocating motion of the knife of uprooter’s cutting bracket, is improved. This technical solution increases the productivity of the uprooter used during infill construction.
On the basis of standard data for the density and the initial and final temperatures in the decomposition (pyrolysis) of thermoprotective binder composites, the law describing their decomposition is identified. That law permits determination of the mass of gases generated at the thermal wavefront, which takes the form of a narrow pyrolytic zone. The gases filter through the porous coke residue to the external boundary, and so affect the thermal state of the thermoprotective composite. On the basis of the law derived, the analysis of the composite’s pyrolysis is simplified, because there is no need to take account of the chemical kinetics.
The article presents the results of analysis of the influence of the thickness, deformation scheme, grain size, and chemical composition of annealed strip billets made of L68 alloy on the quality of tubes for continuous pressure welding after high-frequency induction heating. Two methods of obtaining billets for welding tubes made of silicon-alloyed brass that ensure high tube quality are considered.
The modification of polydimethylphenylsilazane with an epoxy oligomer for use as a binder in the technology of producing ceramic matrix composites (CMCs) is considered. As a result of the modification, the yield of pyrolysis residue increased from 21 to 60 wt %.
The potential of digital image analysis based on the Segment Anything Model (SAM) in analyzing the morphology of single tracks obtained by selective laser melting (SLM) is considered. A digital microscope produces images of single tracks obtained at different scanning speeds and different laser source power. The images are automatically analyzed: the single tracks are classified by external appearance and their width is recorded. The quality of the initial digital images and the presence of thermal influence zones significantly affect the agreement of the measurements obtained by automatic analysis and the measurements obtained by microscopy of transverse sections.
The article presents the experience of production of machine equipment for mixed and laser processing techniques in Russia. The presented approach has been used for creation and deployment into industrial production of electrochemical die-sinking and hole-contouring machines, equipment for electrochemical diamond honing, and automated technological complexes for laser machining.
Identification of the decomposition law of the binder in composites provides the basis for a mathematical model and analysis of the thermal state of most composites in significantly nonsteady high-temperature loading. The decomposition law of the binder permits analysis of the thermal state of composites without considering the chemical kinetics. Verification of the numerical results confirms the validity of this approach to modeling the thermal state of composites for use in hypersonic aircraft.
Assuming that the deformation of the threads of the screw, nut and locknut are caused mainly by the contact flexibility of their working surface, the load distribution along the threads of the screw is studied. It is found that if the locknut is tightened with a force equal to half the tightening force of the nut, then the loads on the first turns of the nut and locknut will become the same, amounting to approximately half the load on the most loaded turn of the screw tightened without a locknut.
Determining the thermal stress in selective laser melting (SLM) of a metal–powder composite within a single layer requires the solution of an auxiliary problem: analysis of the nonsteady heating of an isotropic half-space by a mobile laser source. The results are used in creating a surface influence function for a thermoelastic half-space.
The influence of the roughness of a steel surface on the slipping friction coefficient and wear of a sealing gasket in a flanged joint is studied. The dependence of the frictional coefficient on the surface roughness Ra of the steel part and the applied force is established. The critical tangential stress for the flange–gasket assembly is determined: at the critical stress, the surface layer of the sealing gasket fails, and sealing of the joint is lost.
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