火焰筒掺混孔边细观热应力及裂纹扩展的研究

【作者】 秦亮；

【导师】 张克实；

【作者基本信息】 西北工业大学 ， 固体力学， 2005， 硕士

【摘要】 结合高温合金的复杂工作条件,探讨了非均匀温度场下高温合金微观结构的应力分布。建立了火焰筒掺混孔边的宏、微观模型,从这两个层次上分别探讨了非均匀温度场下微裂纹的萌生及宏观裂纹的扩展。主要结论如下: 1.假定高温合金材料是单晶材料的集合体,通过数值模拟的方法,利用多晶与单晶之间的关系,可以由宏观材料参数估计微观单晶晶粒的材料属性。 2.非均匀温度场下,材料的晶粒取向、温度梯度、晶粒大小等因素均会影响高温合金内部的微观应力分布,导致应力不均匀分布,为微裂纹的产生创造条件。特别在孔边部分,存在较大的应力集中,很容易产生裂纹。 3.火焰筒掺混孔边裂纹萌生并会继续扩展,经历一段时间的蠕变,扩展趋势减弱。J积分和C积分的结果显示,在非均匀温度场中,材料内部的应力不均匀分布。裂纹尖端应力变化过程是与蠕变等因素息息相关。 本文的研究结果试图从微观上解释热应力下材料内部裂纹的萌生以及宏观热应力下裂纹的扩展。为工程结构中的热应力估计提供参考,为火焰筒的维修和延寿提供依据。更多还原

【Abstract】 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.更多还原