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推导了Modifled—Ψ法应力测试及其穿透深度的计算公式,并利用它测试了铍环形焊件热影响区和基体材料中的残余应力。对电子束焊接的铍环其焊缝附近外表面为拉应力,内表面为压应力。由于Modified—Ψ法透入深度太大,不能用来测定铍的表层残余应力,引入多波长法成功地测试出了铍环表层的应力及应力随层深的分布。同时针对电子束焊接过程的特点,编写了用于应力场计算的有限元分析程序。运用编写的程序分别对不同尺寸及焊接工艺的三个铍环电子束焊接样品进行了有限元分析,并将计算结果与实测值进行了比较。结果表明:有限元计算结果与实测值吻合得较好,为先期预测焊件中残余应力的大小和分布从而优化焊接工艺提供了参考依据。 相似文献
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推导了 Modified-ψ 法应力测试及其穿透深度的计算公式,并利用它测试了铍环形焊件热影响区和基体材料中的残余应力。对电子束焊接的铍环其焊缝附近外表面为拉应力,内表面为压应力。由于 Modified-ψ 法透入深度太大,不能用来测定铍的表层残余应力,引入多波长法成功地测试出了铍环表层的应力及应力随层深的分布。同时针对电子束焊接过程的特点,编写了用于应力场计算的有限元分析程序。运用编写的程序分别对不同尺寸及焊接工艺的三个铍环电子束焊接样品进行了有限元分析,并将计算结果与实测值进行了比较。结果表明:有限元计算结果与实测值吻合得较好,为先期预测焊件中残余应力的大小和分布从而优化焊接工艺提供了参考依据。 相似文献
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根据英国结构完整性评估标准BS7910(2013),考虑焊接残余应力影响,采用失效评估图(Failure Assessment Diagram,FAD)方法对镍基合金压力容器焊接部位内表面裂纹进行安全评估。首先采用有限元分析(Finite Element Analysis,FEA)方法,对压力容器V型、X型坡口环焊缝多层多道对接焊进行数值模拟,获取焊接残余应力分布,并将V型坡口对接焊焊接残余应力曲线与BS7910(2013)标准残余应力分布进行了对比;其次,对BS7910(2013)1级-FAC曲线进行公式化简,在焊接位置考虑残余应力、应力集中、塑性失效因子三因素的影响,对轴向内部半椭圆裂纹进行了失效应力预测。结果表明:残余应力的分布直接影响计算结果,残余拉应力越大,相应失效应力越小;残余应力值和裂纹深度a保持不变,失效应力计算结果随c/a(c为裂纹半长)增大而减小;当c/a比值不变,失效应力值随着a增大而减小。本文焊接残余应力模拟即及失效应力预测方法为以后含缺陷压力容器及管道失效应力计算(寿命预测)提供一定的参考。 相似文献
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利用稳态堆上的中子衍射应力谱仪开展了铍环激光焊接后的残余应力测试。先进行铍材中子衍射应力测试的参数及其优化研究,在固定堆功率、衍射晶面和规范体积的条件下,选取测试时间分别为600s和6 000s进行铍环上同一点的中子衍射峰的重复性测试,结果表明,后者测试铍材应变的统计误差仅为前者的1/3,其标准偏差约为1.10×10-5。取后者测试时间作为优化参数,对铍环焊缝附近轴向应变和环向应变方向的中子衍射峰进行测试,获得两个方向的残余应变分布,进一步计算出焊接残余应力分布。对铍环激光焊接过程的温度场和应力场进行三维有限元数值模拟,将有限元计算得到的铍环焊缝附近中间壁厚处的残余应力和应变与中子衍射测试结果进行对比,结果表明二者分布规律较为一致。 相似文献
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核电站反应堆压力容器(RPV)顶盖控制棒驱动机构(CRDM)管座J形坡口焊缝在一回路高温高压水环境下存在应力腐蚀开裂(SCC)的风险,而焊接残余应力是SCC的主要驱动力。使用二维轴对称模型有限元方法对CRDM中心管座J形坡口进行焊接残余应力分析。为了探索一种简单、高效和保守的方法,研究了热源简化、焊缝形状简化、屈服强度、相变和强化行为对焊接残余应力的影响。结果表明:双椭球热源与均匀热源得到的残余应力结果基本一致;焊缝形状由鱼鳞状简化为方块模型对焊接残余应力结果影响不大,但是与合并焊道的结果相差较大;采用低屈服强度得到的残余应力结果并不保守;在ANSYS软件中,固液相变对残余应力结果影响不大;等向强化模型的结果比随动强化模型的结果保守;在工程上,建议采用均匀热源、方块焊道模型和等向强化模型进行焊接模拟。 相似文献
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Nondestructive inspection techniques such as ultrasonic testing, eddy current testing, and visual testing are being developed to detect primary water stress corrosion cracks in control rod drive mechanism (CRDM) assemblies of nuclear power plants. A unit CRDM assembly consists of a reactor upper head including cladding, a penetration nozzle, and J-groove dissimilar metal welds with buttering. In this study, we fabricated a full-scale CRDM assembly mock-up. An ultrasonic propagation imaging (UPI) method using a scanning laser ultrasonic generator is proposed to visualize and simulate ultrasonic wave propagation around the thick and complex CRDM assembly. First, the proposed laser UPI system was validated for a simple aluminium plate by comparing the ultrasonic wave propagation movie (UWPM) obtained using the system with numerical simulation results reported in the literature. Lamb wave mode identification and damage detectability, depending on the ultrasonic frequency, were also included in the UWPM analysis. A CRDM assembly mock-up was fabricated in full-size and its vertical cross section was scanned using the laser UPI system to investigate the propagation characteristics of the longitudinal and Rayleigh waves in the complex structure. The ultrasonic source location and frequency were easily simulated by changing the sensor location and the band pass filtering zone, respectively. The ultrasonic propagation patterns before and after cracks in the weld and nozzle of the CRDM assembly were also analyzed. Since this visualization method is not limited in the flat cross section, it will be useful in developing ultrasound-based structural health monitoring technologies, advanced nondestructive methods, and numerical models. In addition, the proposed laser UPI system could be a useful tool in optimizing the receiver and transmitter locations, the ultrasonic path, and the ultrasonic frequency. 相似文献
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控制棒驱动机构(CRDM)检修及堆芯换料时都需要多次拆卸CRDM的耐压壳体,为解决现有耐压壳体Ω密封焊缝泄漏以及不能多次拆卸的问题,本文采用螺母压紧石墨环方案,利用石墨环的压缩回弹性能防止冷却剂泄漏,并设计一种石墨环密封组件实现快速拆卸;通过开展密封环压缩回弹测试、应力松弛测试以及密封组件泄漏率等密封性能测试试验对石墨环密封组件的密封性能进行验证。结果表明,本文设计的石墨环密封环组件满足设计要求,可以实现高温高压环境下的密封性能。 相似文献
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获得反应堆压力容器内部大尺寸环形异种金属焊缝残余应力分布可为反应堆压力容器结构设计和制造工艺优化提供指导,通过设计和制造能够代表产品焊接结构形式的镍基合金和低合金钢异种金属焊接结构模拟件,采用轮廓法测试焊接结构模拟件内部纵向残余应力,采用有限元法模拟计算焊接结构模拟件横向和纵向残余应力,获得了整个异种金属焊接接头残余应力分布特征。结果表明:焊缝区域内部纵向残余应力为拉伸应力,峰值应力达到500 MPa左右,并且表层应力大于内部应力,峰值应力出现在距下表面3 mm和24 mm位置;横向残余应力在焊缝区域从上表面到下表面的分布为拉应力-压应力-拉应力,压缩横向残余应力峰值达到?300 MPa,出现在距下表面约18 mm位置。本文研究可为焊接结构设计提供理论指导。 相似文献
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Stress corrosion cracking (SCC) in the heat affected zone is the primary damage form due to weld residual stress, corrosion and neutron irradiation environment in the core shroud of a boiling water reactor. The distribution of weld residual stress around a weld is necessary to be clarified to evaluate the structural integrity of core shroud for SCC. Moreover, studying the effects of welding parameters on residual stress on reducing the residual stress is very important to suppress the initiation and propagation of SCC.In this paper, we used a finite element method (FEM) to clarify the distribution of weld residual stress around the sixth horizontal weld (H6a) between the lower ring and the cylinder in the core shroud. The simulation results of axial stress were consistent with the experimental results at the inside and outside surfaces of the core shroud, respectively. The effects of thermal loads and cooling conditions were also investigated with the same model. We simulated the welding progress with water cooling on the inside and outside surfaces of the core shroud in order to study the influence of cooling conditions on the residual axial stress around the weld. The simulation results indicated that water cooling decreased the residual axial stress at the same side due to changing the temperature-affected fields. Moreover, with fixing the peak temperatures of weld passes, the simulation results of the distribution of residual axial stress by the thermal loads with different heating time were compared. The simulation results suggested that the heating time was expected to be longer and the heat flux to be smaller for reaching the small tension residual axial stress or even compression stress around the H6a weld. 相似文献
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《Fusion Engineering and Design》2014,89(4):456-465
The purpose of this study is to investigate the effect of geometric construction on the distribution of residual stresses before and after heat treatment in designing a nuclear welded rotor. The local material removal method was used to measure internal residual stress of the experimental pipe after post weld heat treatment. Three finite element models were employed as follows: a model of experimental pipe, a model with a bottom protrusion existed at the weld region, and a model of two rotor discs butt-welded with a bottom protrusion at the weld region. Investigated results showed that the bottom protrusion existed at the weld region can decrease the residual stress and mitigate the stress evolution significantly on the inner surface. Under the binding effect of the rotor discs, the axial stress of inner surface region is compressive stress; the through-wall axial stress at the weld center line can be deemed to a bending type; both the hoop stress and axial stress at the weld center line on the inner surface are compressive. The impact of geometric construction on the stress evolution at the root bead begins after pass 15 deposited. 相似文献
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Jinmiao Zhang Pingsha Dong Frederick W. Brust William J. Shack Michael E. Mayfield Michael McNeil 《Nuclear Engineering and Design》2000,195(2)
This paper presents a computational model to predict residual stresses in a girth weld (H4) of a BWR core shroud. The H4 weld is a multi-pass submerged-arc weld that joins two type 304 austenitic stainless steel cylinders. An axisymmetric solid element model was used to characterize the detailed evolution of residual stresses in the H4 weld. In the analysis, a series of advanced weld modeling techniques were used to address some specific welding-related issues, such as material melting/re-melting and history annihilation. In addition, a 3-D shell element analysis was performed to quantify specimen removal effects on residual stress measurements based on a sub-structural specimen from a core shroud. The predicted residual stresses in the H4 weld were used as the crack driving force for the subsequent analysis of stress corrosion cracking in the H4 weld. The crack growth behavior was investigated using an advanced finite element alternating method (FEAM). Stress intensity factors were calculated for both axisymmetric circumferential (360°) and circumferential surface cracks. The analysis results obtained from these studies shed light on the residual stress characteristics in core shroud weldments and the effects of residual stresses on stress corrosion cracking behavior. 相似文献
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为研究控制棒驱动机构(CRDM)的结构可靠性规律,考虑CRDM承压壳体的多失效模式,根据应力强度干涉理论建立与CRDM步跃动作次数相关的结构动态可靠性模型。用顺序统计量描述强度失效模式下应力幅值的动态分布模型,基于Miner累积损伤理论和疲劳等效应力分布模型建立结构疲劳寿命和累积损伤分布与步跃冲击载荷作用次数的关系。研究结果表明,在步跃冲击载荷作用下,承压壳体前期的结构可靠度主要由强度失效模式的可靠度决定,当步跃动作达到一定次数时,疲劳失效模式的失效率开始显著增大;相对于疲劳失效模式,强度失效模式的可靠度对应力均值的变化更加敏感。该结果可对CRDM承压壳体的可靠性设计和维修管理提供参考。 相似文献