为了探究船用增压锅炉在变负荷运行工况下耐火砖的断裂失效行为，采用有限元法建立了耐火砖的三维模型，分析锅炉启停时耐火砖的瞬态温度场和应力场，确定拉应力最大的时刻，并将此时的温度场和应力场作为加载条件，运用扩展有限元法分析不同取向初始裂纹的扩展行为，得到了耐火材料在变负荷条件下的失效机制。研究结果表明：耐火砖在锅炉每个启停运行周期内都要经历停炉时产生的拉应力集中阶段，且应力集中在砖肋方向上占优，从而导致任意方向的随机初始裂纹沿着垂直于砖肋的同一个方向扩展、连接，直至贯穿整个耐火砖表面，这是耐火砖失效的主要模式。
In order to explore the failure mechanism of refractories of ships’supercharged boiler under var-ying loads,the 3D model of refractory bricks was designed using the finite element method and thereby the transient fields of temperature and thermal stress were studied.The moment of the maximum tensile stress was determined,and the fields of temperature and thermal stress at that moment were set as load condi-tions.The initial crack propagations at different orientations were analyzed using extended finite element method,and the failure mechanisms of the refractory bricks under varying loads were obtained.The result indicates that:the refractory bricks experience tensile stress in the boiler for every starting-running-stopping cycle,and the tensile stress mainly focuses on the direction of the brick rib,as a result,the random initial cracks in arbitrary directions propagate,connect and finally run through the surface of the bricks in the di-rection perpendicular to the brick rib,which is the main failure mode of refractory bricks.
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