50MW汽轮机断裂叶片及断口的磁记忆研究

从断裂叶片及断口应力分布研究及评估的角度,在对事故叶片进行动、静应力分析基础上,进行了现场50MW汽轮机断裂叶片及断口应力分布的磁记忆检测,研究了断裂叶片及断口应力分布的磁记忆信号特点。结果表明,叶片型线部分出气侧较进气侧磁感应强度过零点信号多,形状复杂;叶根部分断口上出气侧裂纹起始区磁感应强度变化幅度很大,而中间过渡区幅值变化最小,进气侧瞬断区的幅值变化最大且具有过零点的特征。这些磁记忆数值记录了叶片断裂过程的应力变化和分布,磁记忆检测结果与盲孔法应力分布检测结果有较好的一致性。

Stress Distribution Testing of 50 MW Turbine Fracture Blade with Metal Magnetic Memory Method

For the stress distribution measurement and fracture analysis of turbine blades, MMM (metal magnetic memory) testing which is a new nondestructive technology has been applied. Based on the static and dynamic stress calculating, MMM testing is carried out at workshop. Given are the MMM stress distribution characteristics of the cracked blade and fracture face. For the blade root fracture face, the magnetic density normal component Hp(y) of the transition zone is minimal; Hp(y) of the initiation zone is in the middle; Hp(y)of the arrest zone is maximal. And for the blade profile, Hp(y) data of the air-out side have more zero passage signals than that of air-in side. The conclusion from MMM investigation is consistent with the result of small hole stress measuring method. MMM data have recorded the stress distribution variation of failure blade during the whole rupture process. It offers a new tool of fracture analysis in engineering practice.