The prediction of catastrophic rupture of heterogeneous brittle material has been investigated by researchers in the past.In this work,the acoustic emission generated by marble samples under compression was analyzed to verify a power law singularity of index 1/2 as a catastrophe precursor.It is found that prior to catastrophe,the variation of the system response to the controlling parameter follows a power law of negative index,which proves the power law singularity as a common precursor of catastrophe.However,the power indexes vary with variables and samples.The uncertainty reflects sample specificity of an evolution induced catastrophe (EIC) process.
More than 30 bending beams with rectangular cross-section and different thicknesses and heights were pre- pared from Q295 steel. The specimen dimensions were about 240 mm （length） × 60 mm （height） ×70 mm （thick ness）. Flaws were cut along its middle line with a wire cutter, with lengths ranging from 6 to 35 mm. Each specimen was tested with three-point bend loading, and a process curve was obtained between load and the displacement of the loading point, in order to analyze the fracture process when opening the crack. A deformation near the prefabricated crack was observed in the testing period, and the variation of the fracture characteristic parameters was analyzed for different sizes. For a comprehensive understanding of carbon steel fracture resistance behavior, its elasticity and plas- ticity were established by determining its Young＇s modulus and Poisson＇s ratio with an optical strain gauge. This gauge was also used for the loading process test. It was found that the fracture toughness varied with the dimensions, and the toughness of the elastic limit loading was almost constant. Using the relationship of crack resistance stress intensity factor and fracture criterion, the bearing capacity of the material structure could be estimated, which shows a good agreement with the experimental test data.
WANG Li-minFENG YingCHEN Fan-xiuWANG Hai-yingWANG Dong-xu
