Stress-Strain-Based Approach to Catastrophic Failure of Steel Structures at Low Temperatures

摘要

The paper concerns propagation of cracks in structures. The coupled fracture criterion is used when plotting diagrams of quasi-brittle failure of structures made of elastic-plastic material having ultimate strain. Diagrams of quasi-brittle fracture for commonly occurring simplest components of structures just as homogeneous, so with welded joins are given. Analysis of parameters entering into the proposed model has been performed. Diagrams of quasi-brittle fracture were used in analyzing catastrophic failures of steel structure components operating at temperatures lower the cold-brittleness threshold. Parameters of the model are selected from two laboratory experiments (critical stress intensity factor and classical stress-strain diagram) performed at appropriate temperatures. It has been established that weld structures with cracks in the vicinity of a welded joint possess decreased crack toughness. The break-down effect of construction under monotonic loading is clearly expressed: critical loadings significantly decrease with increasing crack lengths. The attention is given to the parameter characterizing plastic material deformation and exhaustion of plasticity resource under preliminary plastic material deformation. After the plasticity resource is exhausted, the temperature of brittleness threshold approaches a room temperature.