The Flame Tube Mixing Hole Edge Micro-thermal Stress And Crack Propagation Studies

Stress distribution pattern of microscopic structure in alloy is discussed under inhomogeneous temperature field according to the real complicated temperature condition. In this thesis, both microscopic model and macroscopic model of dilution hole on combustion liner are built and analyzed and the mechanism of micro-crack forming and macro-crack propagation is studied.According to the investigation, three conclusions were obtained:1. Consider polycrystalline materials as aggregate of single crystals. Based on the aggregate relationship between of polycrystals and single crystals, orthotropic property of microscopic single crystals could be defined from macroscopic material by numerical simulation.2. Some materials properties, such as orthotropic orientation, temperature grade, the size of grains, lead to microscopic stress distribution inhomogeneous in high temperature alloy, and which may produce micro-crack. Especially near the dilution hole, stress concentration can produce crack easily.3. The initial cracks generated near dilution hole and can grow gradually. Undergo creep period of time, the trend of crack propagation became weak. The result of J integral and C integral indicate stress distribution is inhomogeneous and stress evolving is affected by creep obviously.The result of the research can explain how crack initiates on microscopic scale and grows under thermal stress field, which provide references for thermal stress estimating in engineering structure, and help for repairing project and life extending for combustion liner.