本文選題：GHA + 電子束焊接接頭�。� 參考：《工程科學(xué)與技術(shù)》2017年04期

【摘要】：隨著鎳合金電子束焊接在工業(yè)中的大量應(yīng)用,尤其是在航空發(fā)動機和燃氣輪機等關(guān)鍵長壽命服役設(shè)備中的使用,有必要對鎳合金電子束焊接接頭的高周疲勞屬性和斷裂機理進行系統(tǒng)的分析研究。作者利用旋轉(zhuǎn)彎曲高周疲勞試驗機進行疲勞試驗,獲得了母材和焊接接頭的應(yīng)力 壽命(S N)曲線和疲勞斷口,同時利用掃描電鏡(scanning electron microscope,SEM)對疲勞斷口進行了微觀特征分析,確定了母材和焊接接頭在不同應(yīng)力幅下的疲勞裂紋萌生區(qū)和擴展區(qū),分析了裂紋萌生區(qū)位置與應(yīng)力幅的關(guān)系。最后,利用有限元分析了焊接接頭熱影響區(qū)微裂紋位置與大小對材料疲勞性能的影響。從現(xiàn)有的試驗和模擬結(jié)果可以得到:1)母材和電子束焊接接頭應(yīng)力 壽命(S N)曲線分布趨勢一致,但焊接接頭疲勞強度要低于母材,在靠近107周次時,兩者疲勞強度差距最小;2)在高應(yīng)力幅(低周疲勞壽命階段),母材和焊接接頭的疲勞裂紋均起源于試件表面并且都是多點萌生斷裂,焊接接頭疲勞斷口位置位于焊接熔合區(qū)或熱影響區(qū);3)在低應(yīng)力幅(高周疲勞壽命階段),疲勞裂紋在試件次表面萌生,焊接接頭疲勞斷口位于熱影響區(qū)或焊接母材靠近熱影響區(qū);4)通過有限元模擬發(fā)現(xiàn)微裂紋的存在有利于裂紋的擴展。在拉應(yīng)力作用下,橫向微裂紋更優(yōu)于縱向微裂紋沿著應(yīng)力方向進行裂紋擴展;隨著微裂紋尺寸增大,微裂紋間更易于相互貫通,形成更長的裂紋,從而降低了材料的疲勞性能。綜上可知,電子束焊接僅僅影響材料的疲勞強度。疲勞斷裂機理和母材一致都為穿晶解理斷裂,疲勞裂紋萌生區(qū)域位置也和母材一樣都受應(yīng)力幅的直接影響。
[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.
【作者單位】： 四川大學(xué)破壞力學(xué)與工程防災(zāi)減災(zāi)四川省重點試驗室;
【基金】：國家自然科學(xué)基金資助項目(11502151;11327801)
【分類號】：TG456.3

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