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HIGH TEMPERATURE ROTORS - FAILURE MECHANISMS AND REMNANT LIFE ASSESSMENT

机译:高温转子-故障机理和剩余寿命评估

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This paper presents the common failure mechanisms of high temperature rotors and the engineering approaches to their remnant life prediction.1. Rotor bore fatigue crack growth - cracks from original forging defects or induced during long service life may grow under cyclic loading into its critical size causing fast fracture.2. Shaft surface fatigue-creep interaction - high tensile residual stress relaxation under high operating temperature causes creep crack initiation. The cracks would then grow under the combination of cyclic loading and high operating temperature.3. Remanent creep life at the centre of the rotor is based on the time while accumulated creep strain reaches its threshold level.4. Creep rupture could occur at other locations such as the outside surface of the shaft at discs/shaft radii or blade fixings.Finite element method is a powerful tool to analyse stresses, temperature transients, creep strain and reference stress for creep rupture. Fracture mechanics analyses with R5 & R6 approaches were used to estimate the crack initiation and growth rates, the critical crack sizes and the type of the failure. Appropriate Paris law and Norton creep laws were used for fatigue and creep crack growth. Depending on the failure mechanism, a rotor's remnant life is defined in terms of allowable starts and operating hours.
机译:本文介绍了高温转子常见的失效机理及预测其剩余寿命的工程方法。1。转子孔疲劳裂纹扩展-原始锻造缺陷或在较长使用寿命内引起的裂纹可能在循环载荷下增长到其临界尺寸,从而导致快速断裂2。轴表面疲劳-蠕变相互作用-在较高的工作温度下高的残余拉伸应力松弛会引起蠕变裂纹的萌生。然后,在循环载荷和高工作温度的共同作用下,裂纹会扩展。3。转子中心的剩余蠕变寿命取决于累积蠕变应变达到其阈值水平的时间4。蠕变断裂可能发生在其他位置,例如在圆盘/轴半径或叶片固定处的轴外表面。有限元方法是分析应力,温度瞬变,蠕变应变和蠕变断裂参考应力的强大工具。使用R5和R6方法进行的断裂力学分析可以估算裂纹的萌生和扩展速率,关键的裂纹尺寸和破坏类型。适当的巴黎定律和诺顿蠕变定律用于疲劳和蠕变裂纹的增长。取决于故障机理,转子的剩余寿命是根据允许的启动和运行时间来定义的。

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