【作者】 于庆民；

【导师】 岳珠峰；

【作者基本信息】 西北工业大学 ， 固体力学， 2005， 硕士

【摘要】 本文针对单晶材料的各向异性特点,采用有限元方法,对国产镍基单晶DD3切口圆棒试样、气冷叶片模拟试样的弹塑性和蠕变性能及模拟叶片的振动特性进行了分析,同时对现有的高温试验设备进行了改造,使其适于温度梯度试验。主要的工作总结如下: 1.建立了镍基单晶切口试样的三维有限元模型,研究了不同尺寸的“U”型和“V”型切口试样的应力分布和滑移系开动特性,给出了八面体分切应力沿切口截面径向和周向的分布情况。切口尺寸对分切应力有显著影响:对于这两种类型切口,随着切口半径的减小,最大分切应力增加,并且切口半径越小,分切应力沿切口截面周向波动的幅度越大;相应的开动滑移系也不同。 2.利用有限元方法模拟了国产镍基单晶合金DD3【001】取向切口圆棒试样的蠕变性能。结果表明:切口半径对应力分布有显著的影响,切口半径越大,蠕变应力越大;切口深度对蠕变性能的影响不大;切口半径对持久寿命的影响作用非常大,切口半径越小,持久寿命越大。 3.针对单晶冷却涡轮叶片,对镍基单晶含孔洞平板模拟试样进行了弹塑性分析,详细分析了[001]和[111]两种晶体取向下孔洞附近弹塑性应力分布及八面体滑移系族12个滑移系在拉伸变形时的启动情况。结果表明,晶体取向对应力场的分布及启动滑移系有显著的影响。沿不同取向加载时,孔洞周围的应力水平不同,应力场演化的过程也不同,同时滑移系的启动状态也不同。 4.采用含孔平板试样模拟冷却单晶叶片,分析了冷却镍基单晶叶片在950℃时的蠕变持久性能。[001】、[111】两种晶体取向的有限元分析结果表明,气膜孔对试样的承载能力有较大的影响,对持久性能的影响更为显著,含气膜孔模型的持久寿命比不含孔的模型的持久寿命大大降低,小孔的数量越多,持久寿命降低的越大;气膜孔对[111]取向的持久性能的影响比【001】取向显著。 5.利用通用有限元程序Marc分析了单晶叶片的振动特性,考虑了取向、温度和转速的影响。计算结果表明,【111】取向的固有频率大于[001】取向,取向对万声J黄诀掌硕士学位论文 高阶固有频率的影响比低阶大;温度升高,固有频率下降;随着转速增加, 固有频率也在增加。转速对[001】取向固有频率的影响要比〔1川取向大。在工 作状态下,转速对低阶频率影响大,高阶则比较小。6.对现有的高温试验设备进行了改造,采用薄壁圆管试样,外壁温度由电炉控 制,内壁通冷却高压空气,产生温度梯度。此设备可用于温度梯度试验。关键词:镍基单晶合金;晶体塑性理论;有限元;切口圆棒试样;单晶涡轮叶片;气冷叶片:弹塑性;蠕变;振动;温度梯度更多还原

【Abstract】 Finite element simulations have been carried out to study the elastic-plastic and creep responses of single crystal structures. The models included circumferentially notched bars and plates containing hole(s) which can simulate air-cooled blades. The vibration character of single crystal blade has also been analyzed. All the calculation parameters were chosen from the nickel-base single crystal DD3. In order to perform temperature-gradient experiment, the high-temperature testing machine has been improved. They are as follows:1. Different U-type and V-type notched bars were investigated with tensile orientation [001] using the finite element code ABAQUS. The von Mises stress characteristics and resolved shear stress distributions of slip systems were given. The results show that the notch size has strong influence on the resolved shear stress. To the two types of notches studied, the resolved shear stress increases with the decreasing of notch radius, and so does the resolved shear stress along the circle of the specimens. The activated slip systems in the notch section are different for different notch .2. Seven U-type and V-type circumferentially notched specimens have been creep numerical simulated under tensile orientation [001] at 950 °C with the software MARC. The creep lifetime including circumferentially notched and smooth specimens was investigated based on the maximum shear stress amplitude. The results show that the notch size has strong influence on stress distributions and lifetime. The resolved shear stresses increase with notch radius increasing. For the same net-section stress, the notched specimens have a longer lifetime than of the smooth one.3. A plate containing a hole was used to simulate gas turbine blade with cooling holes. Numerical calculations with crystal plasticity theory have been performed to study the elastic-plastic stress field near the hole under tensile loading. Two crystallographic orientations, [001] and [111], were considered. The distributions of von Mises stress and resolved shear stresses (RSS) of the 12 octahedron slip systems were given. The results show that the crystallographic orientation has remarkable influence on both von Mises stress and RSS distributions. The elastic stress distributions near the hole are similar for both orientations, though the stress levels are different. The RSS distributions around the hole are different between the two orientations, which leads to the different activated slip systems.So the deformed shape of the hole in [001] orientation differs from that in [111] orientation.4. Thin-walled plates with small holes were used to simulate gas turbine blades with cooling holes. The effect of cooling holes on stress-rupture properties of cooling gas turbine blades were investigated by finite element method. The creep parameters in crystallographic orientations [001] and [111] were chosen from nickel-base single crystal superalloy DD3 at 950℃. The numerical results show that the cooling holes cause high stress concentration and the creep life of the specimens is greatly influenced by the holes. The number of the cooling holes has notable influence on the lifetime. The cooling holes have larger influence on the lifetime in [001] orientation than that in [111] orientation. All the calculations were performed with the finite element code MARC with a user subroutine.5. The vibration characteristics of single crystal blade were simulated using the finite element code MARC. The influences of crystallographic orientation, temperature and rotating speed were considered. The results show that the natural frequency of crystallographic orientation [111] is larger than that of [001]. The crystallographic orientation has greater influence on the high order natural frequencies than low order ones. The natural frequencies increase with the decreasing of temperature and increasing of rotating speed respectively. The influence of rotating speed on natural frequency in orientation [001] is greater than that in [111]. At working state, rotating speed influe更多还原