GH80A镍合金电子束焊接接头旋转弯曲高周疲劳行为研究

发布时间：2018-06-13 01:08

本文选题：GHA + 电子束焊接接头　；参考：《工程科学与技术》2017年04期

【摘要】：随着镍合金电子束焊接在工业中的大量应用,尤其是在航空发动机和燃气轮机等关键长寿命服役设备中的使用,有必要对镍合金电子束焊接接头的高周疲劳属性和断裂机理进行系统的分析研究。作者利用旋转弯曲高周疲劳试验机进行疲劳试验,获得了母材和焊接接头的应力寿命(S N)曲线和疲劳断口,同时利用扫描电镜(scanning electron microscope,SEM)对疲劳断口进行了微观特征分析,确定了母材和焊接接头在不同应力幅下的疲劳裂纹萌生区和扩展区,分析了裂纹萌生区位置与应力幅的关系。最后,利用有限元分析了焊接接头热影响区微裂纹位置与大小对材料疲劳性能的影响。从现有的试验和模拟结果可以得到:1)母材和电子束焊接接头应力寿命(S N)曲线分布趋势一致,但焊接接头疲劳强度要低于母材,在靠近107周次时,两者疲劳强度差距最小;2)在高应力幅(低周疲劳寿命阶段),母材和焊接接头的疲劳裂纹均起源于试件表面并且都是多点萌生断裂,焊接接头疲劳断口位置位于焊接熔合区或热影响区;3)在低应力幅(高周疲劳寿命阶段),疲劳裂纹在试件次表面萌生,焊接接头疲劳断口位于热影响区或焊接母材靠近热影响区;4)通过有限元模拟发现微裂纹的存在有利于裂纹的扩展。在拉应力作用下,横向微裂纹更优于纵向微裂纹沿着应力方向进行裂纹扩展;随着微裂纹尺寸增大,微裂纹间更易于相互贯通,形成更长的裂纹,从而降低了材料的疲劳性能。综上可知,电子束焊接仅仅影响材料的疲劳强度。疲劳断裂机理和母材一致都为穿晶解理断裂,疲劳裂纹萌生区域位置也和母材一样都受应力幅的直接影响。
[Abstract]:With the extensive application of nickel alloy electron beam welding in industry, especially in aero-engine and gas turbine and other key long-service equipment, It is necessary to study the high cycle fatigue properties and fracture mechanism of nickel alloy electron beam welded joints. In this paper, the fatigue test was carried out by rotating bending high cycle fatigue test machine, and the stress life curve and fatigue fracture of base metal and welded joint were obtained. At the same time, the microscopic characteristics of fatigue fracture were analyzed by scanning electron microscope (SEM) and scanning electron MicroscopeSome (SEM). The fatigue crack initiation zone and propagation zone of the base metal and welded joint under different stress amplitudes are determined and the relationship between the location of crack initiation region and the stress amplitude is analyzed. Finally, the influence of the location and size of microcracks in the heat-affected zone of welded joints on the fatigue properties of the welded joints is analyzed by finite element method. From the existing test and simulation results, it can be found that the distribution trend of the stress life of the base metal and electron beam welded joint is the same, but the fatigue strength of the welded joint is lower than that of the base metal, and the fatigue strength of the welded joint is lower than that of the base metal, and the fatigue strength of the welded joint is lower than that of the base metal. At high stress amplitude (low cycle fatigue life stage), the fatigue cracks of both base metal and welded joint originate from the surface of the specimen and are both multipoint initiation fracture. The fatigue fracture location of welded joint is located in the welding fusion zone or heat affected zone (HAZ). The fatigue crack initiation occurs on the subsurface of the specimen in the low stress amplitude (high cycle fatigue life stage). The fatigue fracture of welded joint is located in the heat-affected zone or near the heat-affected zone. Under the action of tensile stress, the transverse microcracks are better than the longitudinal microcracks propagating along the stress direction, and with the increase of the size of the microcracks, the microcracks are easier to penetrate each other and form longer cracks, thus reducing the fatigue properties of the materials. It can be seen that electron beam welding only affects the fatigue strength of the material. Both the fatigue fracture mechanism and the base metal are transgranular cleavage fracture, and the location of the fatigue crack initiation region is directly affected by the stress amplitude as well as the base metal.
【作者单位】：四川大学破坏力学与工程防灾减灾四川省重点试验室;
【基金】：国家自然科学基金资助项目(11502151;11327801)
【分类号】：TG456.3

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