Fatigue Life Evaluation Method for Foundry Crane Metal Structure Considering Load Dynamic Response and Crack Closure Effect

摘要

To compensate for the shortcomings of quasi-static law in anti-fatigue analysis of foundry crane metal structures, the fatigue life evaluation method of foundry crane metal structure considering load dynamic response and crack closure effect is proposed. In line with the theory of mechanical vibration, a dynamic model of crane structure during the working cycle is constructed, and dynamic coefficients under diverse actions are analysed. Calculation models of the internal force dynamic change process of dangerous cross-sections and a simulation model of first principal stress-time history are established by using the steel structure design criteria, which is utilised to extract the change of first principal stress of danger points over time. Then, the double-parameter stress spectrum is obtained by the rain flow counting method. The fatigue life calculation formula is corrected by introducing a crack closure parameter that can be calculated by the stress ratio and the effective stress ratio. Under the finite element model imported into Msc. Patran, crack propagation analysis is performed by the growth method in the fatigue integration module Msc. Fatigue. Taking the metal structure of a 100/40t-28.5m foundry crane with track offset as an example, the accuracy of calculation results and the feasibility and applicability of the proposed method are verified by theoretical calculation and finite element simulation, which provide a theoretical basis for improvement of the fatigue resistance design of foundry cranes.