Modeling of stress-strain state in connection resource defines of volumetric hydraulic drive

Introduction. The article explores the stress-strain state of a distribution pair of aggregates of a volumetric hydraulic drive and the search for ways to increase its durability. Materials and Methods. In the process of studying, the generally accepted principles of the theories of friction, reliability, elasticity, mechanisms and machines, and mathematical modeling were used. To simulate the stress-strain state, an engineering analysis system ANSYS was used. Distribution pairs of hydraulic pumps 313.3.112, GST-112 and Sauer Danfoss 90R075 were chosen as objects of study. Results. As a result of the study there were obtained values of the real contact stresses and long-term current stress on the distribution of pairs of units of volumetric hydraulic drive: the 313.3.112 hydraulic pump is 26,93 MPa; for GTS-112 water pump is of 22.21 MPa for the Sauer Danfoss 90R075 hydraulic pump is 27,12 MPa. It is revealed that the area located on the discharge side is a subject to the greatest loads. This is the cause of one-sided wear of spherical surfaces, which is quite common in units decommissioned. The values of contact stresses in the joints hardened by the method of electric spark machining are on average 1.4 and 9.4 % lower than in not unhardened. In the process of electric spark machining there is a redistribution of stresses on the surface that leads to a decrease of the operating load in the connections. Conclusions. The study allowed modelling the stress-strain state in new and hardened distribution pairs of volumetric hydraulic drive units under operating conditions and suggesting ways to increase its durability. It was established that to increase the wear resistance of a resolving compound and the durability of the volumetric hydraulic drive aggregates, it is necessary to ensure that in distribution pairs the maximum bearing capacity is greater than the maximum long-term operating load in these connections. To solve this problem, it is proposed to create coatings with high tribotechnical properties by the method of electricspark machining.