A mathematical model of dynamic processes in pumping unit of a drilling rig with friction clutch, taking into account variable moment of inertia of slider-crank mechanism links and random number of pistons of the pump, was developed. Joint integration of differential equations of motion of pumping unit parts was carried out with numerical methods. The calculations performed considered the torque moment of friction in the clutch and equations of electromagnetic processes in asynchronous motor. The results of research of run-up processes of pumping unit were presented. The influence of parameters of friction clutch on the performance of pumping unit was established.
The method of experimental determination of strain energy density of plastic materials is developed. The technique for complete true stress-strain curves plotting is formulated. The standard hydraulic testing machine is equipped with specially designed experimental setup for Bridgman specimens testing at strain controlled tension loading with digital camera and light source for using digital image correlation method-a non-contact technique for strain and displacement measurement. The digital image correlation method was used to determine the local strain at the onset of fracture in the neck of Bridgman specimen. The technique takes into account the change of cross-section area in the neck of specimen due to internal crack propagation when calculating the true stresses. The complete true stress stress-curve of 40Kh alloyed steel is plotted end critical strain energy density of steel is determined from it. It is shown that the critical strain energy density of material, determined from the curve obtained by developed technique is 1.8 times higher than determined from the classical true stress-strain curve and is close to the value of the specific heat of fusion of steel. The curves built using the proposed technique can be used for setting material properties in stress-strain state calculations by finite element method at large scale yielding conditions, for instance at pressure vessels critical pressure calculation. The critical strain energy density value can be considered as a material property at fatigue lifetime calculation using energy approach.
Results of the researches of hydrogen influence on fracture of 65 sheet spring steel by several methods are presented. The distribution of deformation and topography of a hollow in front of the crack tip is determined, the stress intensity factor is calculated, fractographic analysis of a fracture surface and metallographic analysis of the morphology of crack distribution are carried out. The decrease of operation characteristics of the material as a result of hydrogen influence which becomes apparent in localization of plastic deformations and intensive delamination on the layers of rolling is established.
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