Study of the process of connecting rod liners’ shape changing in the pre-failure operation period of transport and technological machines and equipment

Abstract

BACKGROUND: During the operation of transport and technological machines and equipment, the most frequent failure is loose running of connecting rod liners of a crankshaft. Previous studies on tractor, locomotive and automotive diesel engines did not sufficiently disclose the reasons for loose running of liners. AIMS: Study of the stress-strain state of the steel base of connecting rod liners as the initial and developing factors of the process leading to failure. METHODS: The research is based on the analysis of numerous works devoted to the study of the causes of loose running of connecting rod liners of various internal combustion engines. The methods and results on the operational and bench studies of the stress state and shape changing of connecting rod liners for the KAMAZ-740 (8Ch 12/12) engine obtained by the team of authors are used as the basic data. RESULTS: The process of change in stress state and consequent change in geometric parameters of the steel base, accompanied by change in the shape of connecting rod liners of the KAMAZ-740 engines has been revealed. It is established with the study that the occurrence of failure is not sudden. The process proceeds according to a certain pattern in three stages. The first stage is characterized by the appearance of deformation of a liner due to excessive stress state; the second stage is caused by development of obtained deformations up to critical values; the third stage is loose running of a connecting rod due to obtained deformations and violations of liner’s hydrodynamics conditions. The main result is justification of requirements and conditions for ensuring stability of parameters and shape of liners during long-term operation of engine. CONCLUSIONS: Knowledge of the process leading to the change in shape of crankshaft bearing liners makes it possible to develop design and technological solutions and recommendations to eliminate failures by optimizing the parameters of liners.