Computational and Experimental Study of the Stress State of the Opposed Compressor Connecting Rod to Assess the Probability of Failure-Free Operation

Abstract

During operation, fatigue crack events arising in the piston heads of connecting rods of opposed compressors are observed. In order to assess the probability of their failure-free operation, a study of the connecting rods loading of compressors operating in the chemical industry has been carried out. Since experimental studies of stresses acting in structural elements of large dimensions cause great difficulties, their stress state is determined by computational methods. When loading the connecting rod, there is an area where the distributed load acts and another area with a gap between the cylindrical surfaces where there is no contact pressure. The forces acting on the border of the contact areas and the gap of the finger with the connecting rod bore have been determined: radial force N, tangential force Q, and bending torque M. The forces N and Q are treated as functions of the contact angle a. By means of a numerical experiment, the stresses were determined in the contact zone from the angle a corresponding to the contact zone end to the angle of the head transition into the piston rod. In this case, the operating loads and clearances in the connecting rod-to-finger interface varied. The values and nature of changes in the loads affecting the crank mechanism of the compressor during its operation have been experimentally determined. The nature of the stress distribution in the connecting rod sections has been established, and the most loaded sections have been revealed. Comparing the data of a full-scale experiment and the results of numerical studies of stress distribution showed their practical coincidence. Moreover, a numerical experiment makes it possible to estimate the simultaneous effect of loads and clearances on the growth of stresses, which is almost impossible to implement by means of experimental studies.