With an increase in the technical characteristics of the axial piston hydraulic machine (APHM), first of all, the working pressure and rotational frequencies, the requirements for the structures and materials of the parts of the swinging unit increase, since it is necessary to simultaneously ensure high strength and stiffness characteristics, wear resistance and thermal conductivity. Therefore, in recent decades, technologically more complex composite or composite structures have been used, in which the choice of materials for different parts of parts is made on the basis of meeting the necessary requirements for them, as well as the technological capabilities of production. An increase in pressure in an axial piston hydraulic machine APНM leads to an increase in bulk and contact stresses and an increase in the frequency of failures, of which about 30% is in the cylinder block (CB) and 10% – on lenticular distributor (LD). These two parts are characterized by a complex multiply-connected form, the distributor can be considered fs a flat (two-dimensional) design, a CB – as three-dimensional one. In the axial cylinders of the block there are variables according to the character and significant load: pressure of working fluid, forces from lateral pressure of the pistons, inertial loads, etc. In connection with friction on the contact surfaces, the LD is made of high-strength alloy steel, CB – of wear-resistant materials, bronzes or brass, which provides an increase in mechanical efficiency and heat sink. In the works devoted to the improvement of the design and calculations of the CB, it was proposed to us composite materials (steel-bronze) and composite permanent and detachable structures. For strength analysis, simplified analytical models of the LD and CB in the form of statically indefinable rod systems with variable cross-section rods were developed. Verification calculations using the finite element method (FEM) were more often performed in a flat formulation, although the stress-strain state (SSS) of the block is essentially three-dimensional. In this paper, using the Autodesk Inventor software package, a 3D model of the BC for the APH 310-25 was built. This model made it possible to calculate the SSS of CB in the ANSYS Workbench. Using the ANSYS Workbench software, the characteristics of the material, the method of fixing, and the uneven distribution of pressure in the pistons cavities into account are taken.
As a result of modeling and calculations in the ANSYS software package, the VAT of the BC has been determined. It has been established that the maximum stresses in the BC of the original modification appear in the bridges between the axial channels near the end of the block, and in other zones the stresses are substantially less.
To check the fatigue resistance of the BC, fatigue tests of samples of the material from CB, BrO12 bronze were carried out, with a symmetric cycle of stress variation and a fatigue curve was plotted.
This made it possible to perform an analytical calculation of the BC on fatigue resistance. The results of fatigue tests of samples were recalculated for the CB according to the method of the statistical similarity theory of fatigue failure by Serensen-Kogaev. In this case, a substantially inhomogeneous stress state at the dangerous section of the inter-cylinder bridge is reduced to an equivalent homogeneous one. In this method, a substantially inhomogeneous stress state at the dangerous section of the inter-cylinder bridge is reduced to an equivalent homogeneous one. This allows us to recommend used this method to determine the resource of the CB.
Some new modifications of the BC design are proposed: the fillet radius of the fillets is increased in the transition from the cylinder bores to the bottom; cylinder holes are inclined to the axis of the CB in the diametric plane at an angle . The rational values of the quantities and are determined by stepwise FEM-calculations. In the modified construction of the APG 310-25 block the stresses in the inter-cylinder jumper are distributed more evenly and their maximum values are reduced by 20%.
The manufacturing technology of the modernized CB was proposed. The performed analysis of the SSS of the considered structures confirms their higher technical level.
|Affiliation of speaker||Academy of Construction and Architecture of V.I. Vernadsky Crimean Federal University|
|Publication||Journal of Cleaner Production|
|Position of speaker||Head of Water Supply and Sanitary Technique Chair|