本文關鍵詞： 核主泵屏蔽套 脈沖激光焊接 Hastelloy C-276 數(shù)值模擬 殘余變形　出處：《大連理工大學》2014年博士論文　論文類型：學位論文

【摘要】：第三代核電站(AP1000)反應堆冷卻劑泵(核主泵)采用了屏蔽式電機,而屏蔽式電機中屏蔽套的制造質(zhì)量是保證核主泵安全可靠運行的重要基礎。屏蔽套主要由哈氏合金(Hastelloy C-276)薄板經(jīng)過剪裁和焊接工藝制造而成。由于定子屏蔽套壁厚在0.3～0.5mmin之間,長度達3000mm以上,直徑為565mm,而且其直徑偏差僅為±0.076mm,使役壽命更長達60年,因此屏蔽套的制造工藝精度要求非常高。本文針對屏蔽套成形制造高精度和長壽命的設計要求,采用脈沖激光焊接技術,以數(shù)值模擬為主要研究手段,分析了Hastelloy C-276薄板脈沖激光焊接應力應變及變形分布規(guī)律,提出了等效熱載荷的計算方法及焊接應力變形的調(diào)控策略,揭示了調(diào)控參數(shù)與屏蔽套尺寸精度的映射關系,為核主泵屏蔽套的自主化制造提供理論基礎和工程指導。主要研究內(nèi)容及結(jié)論如下： (1)建立了Hastelloy C-276薄板脈沖激光焊接熱力過程的有限元模型,模型中考慮了材料隨溫度變化的熱物理和力學性能以及脈沖激光能量間歇加載方式。分析了脈沖激光焊接溫度場、瞬態(tài)及殘余應力應變和變形場的分布特點。通過焊接實驗及相關檢測設備,測量了溫度場和殘余變形,兩者吻合較好,驗證了模擬結(jié)果的準確性。 (2)通過橫向塑性應變的演變歷程,分析了橫向收縮變形的產(chǎn)生機制,發(fā)現(xiàn)了壓縮塑性應變是橫向收縮變形的直接原因,提出了考慮橫向撓曲變形的表征方法,并獲得了工件尺寸對橫向收縮變形的影響規(guī)律。以縱向殘余應力分布特征為基礎,提出了一種利用縱向殘余應力沿橫截面分布的函數(shù)關系并考慮夾具拘束來確定等效熱載荷的計算方法,并采用彈性屈曲分析,實現(xiàn)了對超薄大長徑比屏蔽套焊后結(jié)構穩(wěn)定性的判斷。 (3)采用位移約束假設代替夾具剛性固定拘束的方法,分析了拘束距離對焊接瞬態(tài)及殘余應力應變和變形的影響規(guī)律。隨著拘束距離的減小,縱向殘余壓應力和橫向殘余拉應力的峰值都呈減小趨勢,而縱向殘余拉應力的峰值則呈增大趨勢；焊接縱向和橫向撓曲變形及橫向收縮變形都表現(xiàn)為減小的趨勢,特別是橫向收縮變形的減小幅度非常明顯；采用減小拘束距離的方法,能夠?qū)崿F(xiàn)屏蔽套周長尺寸精度的有效控制。 (4)針對夾具剛性固定拘束對縱向殘余拉應力調(diào)控效果的不足,提出了基于一定拘束條件下采用動態(tài)溫差拉伸對縱向殘余應力與失穩(wěn)變形進行調(diào)控的方法。研究了熱沉參數(shù)對焊接溫度場、瞬態(tài)及殘余應力和變形場的影響規(guī)律。隨著激冷位置靠近熱源或激冷強度增加,縱向殘余應力和撓曲變形呈顯著減小趨勢,而橫向收縮變形卻呈增大趨勢。通過優(yōu)選方法確定調(diào)控參數(shù),能為核主泵屏蔽套高精度低應力焊接制造提供生產(chǎn)指導。
[Abstract]:The third generation nuclear power plant AP1000) reactor coolant pump (nuclear main pump) uses the shielded motor. The manufacturing quality of the shield sleeve in the shielded motor is an important basis to ensure the safe and reliable operation of the nuclear main pump. The shield sleeve is mainly made of Hastelloy C-276). The thin plate is made by cutting and welding process. The thickness of stator shield sleeve is between 0.3 min and 0.5mmin. The length is more than 3000 mm, the diameter is 565 mm, and the diameter deviation is only 鹵0.076 mm, so the service life is even longer than 60 years. Therefore, the manufacturing precision of the shield sleeve is very high. In this paper, the pulse laser welding technology is adopted to design the high precision and long life of the shield sleeve. Numerical simulation is the main research method. The distribution of stress, strain and deformation in pulsed laser welding of Hastelloy C-276 thin plate is analyzed. The calculation method of equivalent thermal load and the control strategy of welding stress and deformation are put forward. The mapping relationship between the control parameters and the dimensional accuracy of the shield sleeve is revealed, which provides the theoretical basis and engineering guidance for the autonomic manufacture of the nuclear main pump shield sleeve. The main research contents and conclusions are as follows: 1) the finite element model of thermal process for pulsed laser welding of Hastelloy C-276 thin plate is established. The thermal physical and mechanical properties of the material with temperature variation and the intermittent loading mode of pulsed laser energy are considered in the model. The temperature field of pulsed laser welding is analyzed. The distribution characteristics of transient and residual stress strain and deformation field. The temperature field and residual deformation are measured by welding experiment and related testing equipment. The results are in good agreement with each other and verify the accuracy of the simulation results. 2) through the evolution of transverse plastic strain, the mechanism of transverse shrinkage deformation is analyzed, and the direct cause of transverse shrinkage deformation is found out. A representation method considering transverse flexural deformation is proposed, and the influence of workpiece size on transverse shrinkage and deformation is obtained, which is based on the longitudinal residual stress distribution. A method for determining the equivalent thermal load by using the functional relation of longitudinal residual stress distribution along the cross section and the constraint of the fixture is proposed, and the elastic buckling analysis is used. The structure stability of the shield sleeve with super thin and large aspect ratio is judged. (3) the influence of restraint distance on welding transient, residual stress, strain and deformation is analyzed by using displacement constraint hypothesis instead of rigid fixation constraint of fixture. With the decrease of restraint distance, the effect of restraint distance on welding transient, residual stress, strain and deformation is analyzed. The peak value of longitudinal residual compressive stress and transverse residual tensile stress decreased, while the peak value of longitudinal residual tensile stress increased. The longitudinal and transverse bending deformation and the transverse shrinkage deformation of the welding show a decreasing trend, especially the amplitude of the transverse shrinkage deformation is very obvious. The precision of circumference of shield sleeve can be controlled effectively by reducing the constraint distance. 4) the effect of rigid fixation on the longitudinal residual tensile stress is insufficient. A method of controlling longitudinal residual stress and unstable deformation by dynamic temperature differential tension under certain restraint conditions is proposed. The effect of heat sink parameters on welding temperature field is studied. The effect of transient and residual stress and deformation field. The longitudinal residual stress and flexural deformation decreased significantly with the increase of the cooling position near the heat source or the intensity of the cooling. However, the transverse shrinkage and deformation show an increasing trend, and the optimal selection method can be used to determine the control parameters, which can provide the production guidance for the manufacture of high precision and low stress welding of the shield sleeve of the nuclear main pump.
【學位授予單位】：大連理工大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TM623;TG456.7

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