On the Control of Metal Strength of Structural Elements of Floating Cranes

Abstract

Introduction. The article is devoted to the issues of non-destructive testing of mechanical characteristics of metal structural elements of cranes. The reliability of cranes largely determines their safety. The main manifestations of operational failures of floating cranes are analyzed on the example of the UMK-2 crane. It is noted that 27% of failures occur due to the loss of metal strength of their structural elements. Determination of the causes of such failures is possible by conducting non-destructive testing of the mechanical characteristics of the failing structural elements metal. The paper provides the principle of one of the methods of non-destructive strength control based on the impact insertion of a conical indenter into the metal under study with the subsequent analysis of the intermediate parameters of this insertion. The results of measurements of the mechanical characteristics of the metal deformed during the operation of the boom strut of a floating crane are given. The current measured values of the mechanical characteristics of the metal obtained at various points of the strut are processed for compliance with the three-parameter Weibull law to obtain the minimum values of these characteristics. As a result of such processing, it is stated that the minimum values of yield strength, strength and elongation are lower than those claimed by the design documentation for the crane. This may be one of the reasons for the deformation of the structural element during operation.Problem Statement. The application of the method of non-destructive testing of the metal of the boom strut is considered in order to assess the mechanical characteristics and establish possible causes of its deformation when analyzing the operational reliability of the crane.Theoretical Part. When identifying possible causes of deformation or destruction of steel elements of crane structures, it is proposed to apply a method of non-destructive testing of mechanical characteristics based on the impact insertion of a conical indenter into the test surface. Further, it is proposed to process the obtained sample of values of the measured characteristic for compliance with the three-parameter Weibull law to estimate the shift parameter or the minimum value of this characteristic.Conclusions. The minimum values of the tensile strength, yield strength and relative elongation of the metal of the deformed boom strut of the UMK-2 crane were obtained on the basis of the application of the method of non-destructive testing with subsequent approximation of statistical information by the Weibull distribution law. A conclusion was made about the reduced strength characteristics of the metal relative to those stated in the technical documentation, which could cause deformation of the crane boom element.