厚壁奥氏体焊缝超声波检测之探究

由于奥氏体焊缝中材料性能的各向异性和微观组织结构的不同,奥氏体焊缝的超声波检测是非常困难的。超声波在奥氏体焊缝中会沿金属结晶方向发生偏转,并在焊缝边界上发生散射。过去十年来,人们开发了多种模拟各向异性材料中声波传播的仿真工具。本文则以常规超声波检测方法为基础,将声线跟踪法和弹性动力学有限积分技术（EI、IT）相结合,应用于含晶间应力腐蚀裂纹的厚壁奥氏体焊缝中,其结果显示声线跟踪法和弹性动力学有限积分技术（肼）结合应用,有助于超声波检测参数的选取。     

Ultrasonic array imaging through an anisotropic austenitic steel weld using an efficient ray-tracing algorithm

Ultrasonic inspection of austenitic welds is challenging due to their highly anisotropic and heterogeneous microstructure. The weld anisotropy causes a steering of the ultrasonic beam leading to a number of adverse effects upon ultrasonic array imagery, including defect mislocation and aberration of the defect response. A semi-analytical model to simulate degraded ultrasonic images due to propagation through an anisotropic austenitic weld is developed. Ray-tracing is performed using the A^⁎ path-finding algorithm and integrated into a semi-analytical beam-simulation and imaging routine to observe the impact of weld anisotropy on ultrasonic imaging. Representative anisotropy weld-maps are supplied by the MINA model of the welding process. A number of parametric studies are considered, including the magnitude and behaviour of defect mislocation and amplitude as the position of a fusion-face defect and the anisotropy distribution of a weld is varied, respectively. Furthermore, the use of the model to efficiently simulate and evaluate ultrasonic image degradation due to anisotropic austenitic welds during an inspection development process is discussed.     

Direct model optimisation for data inversion. Application to ultrasonic characterisation of heterogeneous welds

Numerous multipass welds in austenitic stainless steel are made on the primary circuits of nuclear power stations. The heterogeneous anisotropic nature of these welds causes disturbance to ultrasonic propagation. Simulation is a useful tool when attempting to understand physical phenomena. With this objective, a finite element code called ATHENA was developed. Sufficiently realistic modelling of the material is proposed by the Modelling anIsotropy from Notebook of Arc welding (MINA) model, which determines the orientation of the weld grains. Optimisation by inversion of the MINA model is proposed in this study. The results validate the strategy and open perspectives regarding use on real data.     

奥氏体不锈钢焊缝超声阵列检测方法

在焊接热循环作用下,奥氏体不锈钢焊缝内部呈粗大柱状晶组织,且其取向在焊缝不同区域呈各向异性.针对粗大柱状晶引起的超声波散射和晶粒取向不同导致的声束偏折等问题,进行奥氏体不锈钢焊缝超声阵列检测方法研究.针对超声阵列获得全矩阵数据,发展了一种基于时间反转算子分解的超声阵列信号去噪方法.利用射线追踪法,研究了各向异性介质中超声波传播路径确定方法,并将其应用于奥氏体不锈钢焊缝超声阵列全聚焦成像的声束偏折校正.开展了奥氏体不锈钢焊缝超声阵列检测试验研究.结果表明,基于时间反转算子分解方法可以很好剔除检测信号中的散射噪声,凸显特征回波信息,可将全聚焦成像的信噪比提高10 dB,而波束偏折校正则可以提高超声阵列全聚焦成像中缺陷定位的精度.     

Numerical modeling and simulation for ultrasonic inspection of anisotropic austenitic welds using the mass-spring lattice model

This paper deals with two-dimensional numerical modeling and simulation of ultrasonic nondestructive testing of austenitic welds, which are assumed to be homogeneous and transversely isotropic. The numerical computer model used in this work is the rectangular mass-spring lattice model (RMSLM). The model’s capability has first been investigated for accurately simulating ultrasonic waves in the austenitic weld medium. Compatible numerical models for transmitting probes ‘tailored’ for the austenitic weld have also been developed so that incident waves can be sent precisely in desired directions. A two-dimensional numerical simulator, consisting of the probe models and the RMSLM, has been applied to realistic, typical ultrasonic testing problems of austenitic welds, and effective test setups for them have been found. This demonstrates the capability and usefulness of the simulator.     

Modeling tools for ultrasonic inspection of welds

Developments in quantitative ultrasonic nondestructive testing (NDT) of welds require simulation tools for cost-effective research and engineering works. The present paper reviews the specific developments in modeling of weld inspection at the French Atomic Energy Commission (CEA), made in keeping with the general pattern of CEA in simulation studies of ultrasonic examination. Two models have been developed for several years at CEA for this purpose. One is dedicated to the computation of the ultrasonic field radiated by arbitrary transducers into pieces (possibly anisotropic and heterogeneous) under examination. We specifically discuss how the metallurgical structure and associated elastic properties of welds is taken into account. The other simulates a testing experiment. It accounts for the interaction of the beam with defects (within a piece made of isotropic material) and specimen boundaries and simulates the transducer scan over the piece for synthesizing images comparable with measurements. We specifically discuss the influence of the possible complex geometry of the back-wall of a weld. Examples of application are given. They demonstrate the usefulness of such modeling tools in ultrasonic NDT of welds to study and optimize testing configurations, and to help NDT experts to interpret actual data.     

Model-based simulation of focused beam fields produced by a phased array ultrasonic transducer in dissimilar metal welds

Phased array ultrasound testing (PAUT) can produce steerable and tightly focused ultrasonic beams, so it is widely used for detecting flaws. However, inspection of dissimilar metal welds (DMWs) using phased array ultrasound is not easy at all, since ultrasonic beams are skewed and distorted severely in the welds that are anisotropic and inhomogeneous elastic media. So, to increase focusing efficiency and have optimized conditions for inspecting the welds, quantitative prediction of phased array ultrasonic beams is needed. This paper proposes a modeling approach that includes modeling the grain orientation of the welds with buttering, calculating the ray path for the determination of focal laws, and applying the linear phasing multi-Gaussian beam model in order to focus the ultrasonic beams produced by a phased array transducer mounted on a wedge contacted to the interrogated DMW. This paper also presents an example of the model-based simulation of the focused beam fields produced in the DMW. The proposed model allows us to increase the focusing efficiency by accurately simulating the ultrasonic testing of welded components and to propose a new tool to associate welding design with the ultrasonic assessment of structural integrity.     

Modeling of transducer fields in inhomogeneous anisotropic materials using Gaussian beam superposition

This article describes a three-dimensional Gaussian beam model for calculating transducer-generated ultrasonic wave fields in inhomogeneous anisotropic media. The model is based on a formulation presented recently for homogeneous anisotropic materials. The inhomogeneity is modeled by dividing the material into several homogeneous layers, the approach accounting for the propagation through the various layers and the reflection/refraction processes at the interfaces. It thus calculates ultrasonic field patterns, including proper amplitude information and allows a quick evaluation of the sound fields. Application of the model in view of ultrasonic nondestructive testing of layered composite material and of austenitic steel components is addressed. In the latter case, examples are given for various weldment structures, wherein ultrasonic inspection using commercial angle beam transducers is of interest.     

Ultrasonic through-transmission characterization of thick fibre-reinforced composites

Thick composites pose a significant challenge to the ultrasonic nondestructive evaluation process due to the increased attenuation as well as the influence of material anisotropy. The physics of ultrasonic wave propagation in anisotropic material involves understanding such phenomena as beam skewing, material focusing/defocusing, unsymmetrical beam profiles, etc. This ultrasonic behaviour can be considered to be relatively insignificant in the nondestructive evaluation of thin anisotropic composite structures, but cannot be neglected in thick composites. In this paper, the ultrasonic characterization of thick glass-epoxy composites using an immersion through-transmission method employing a standard ultrasonic robot scanner system is discussed in detail. An inverse technique for computing material elastic constants from the acquired data is discussed. The experiment measures group velocity is a function of energy propagation angle (group angle), from which phase velocity is numerically computed as a function of phase angle. Then, the material constants are determined from phase velocity profiles using commercially available parameter identification software. Both uni-directional (five independent elastic constants) as well as cross-ply (nine independent elastic constants) were considered. Through-transmitted ultrasonic beam characteristics in thick composites are then analysed using feature extraction procedures and compared with the isotropic plexiglass structure.     

奥氏体异种钢焊缝超声相控阵检测新法

奥氏体异种钢焊缝超声相控阵检测(PAUT)新法的要点是:(1)用电子背散射衍射法评价奥氏体焊缝显微结构特征;(2)将显微结构数据输入模型,修正适用延时法则;(3)在焊接试样及被检工件上进行特性验证。此法有望为解决承压设备奥氏体异种钢焊缝超声检测因声场畸变引起的表征定量困难,提供有效途径。     

Structures of Austenitic Stainless-steel Castings and their Relevance to Ultrasonic Examination of Castings for PWR Applications

In austenitic castings, the solidification modes A, B, and mixed AB with either A or B structures can all be found in alloys that lie in the specification range for ASME SA351 Grade CF3. Mode A structures are found at (Cr/Ni) equiv>2.2 whilst mode B structures occur for (Cr/Ni) equiv <2.0. For intermediate values of the (Cr/Ni) equiv mixed AB structures are found. Type A structures are equiaxed and can be regarded as macroscopically isotropic. As such, their acoustic attenuation is uniform and the ultrasonic beam does not distort on propagation through these materials. In contrast, Type B materials are highly anisotropic because of their coarse grained, columnar structure which results in a highly variable acoustic attenuation and distortion and skewing of the ultrasonic beam. As part of the safety case for the Sizewell “B” Pressurised Water Reactor (PWR) the Central Electricity Generating Board (CEGB) is fabricating test blocks containing known defects which will be used to validate the ultrasonic operators who will inspect the cast austenitic pump-casings of the primary circuit. This paper describes the development of the ultrasonic technique to inspect the pump casings based upon a detailed knowledge of the metallurgy of stainless-steel castings, the propagation of ultrasound in coarse grained austenitic materials and the design of the pump casing itself.     

Numerical calculation of ultrasonic propagation with anisotropy

A computer simulation technique for three-dimensional ultrasonic propagation was utilized for the visualization and investigation of ultrasonic propagation in various materials such as anisotropic solids and combined materials. The calculation technique used here is based on a finite-difference method, but uses an improved nodal calculation method following fundamental consideration of the elastic wave equations. The improvement enabled unified treatment of calculation nodes at the inside and the boundary of the solid, and offered simplicity for calculation at the boundary and applicability for combined and anisotropic materials with limitation on the applicable type of anisotropic stiffness matrix. Here, we present the applications of the calculation technique for the two-dimensional and three-dimensional ultrasonic propagation relating to nondestructive material evaluation using ultrasound, and show the usefulness and applicability for the complex ultrasonic phenomena observed in ultrasonic measurements.     

超超临界机组锅炉异种钢小径管镍基焊接接头超声波检测

针对超声检测火力发电厂锅炉小径管奥氏体钢与低合金钢对接异种钢焊缝的技术难题,文章通过理论分析、试验研究及现场检测验证,研究了常规小径管探头异种钢焊缝超声波检测方法。结果表明,对于如熔合线裂纹类缺陷选用小角度探头(K1～1.5)效果较佳;对于焊缝内缺陷宜选用大角度探头(K2～2.5)。利用该方法能有效检测出焊缝内各种缺陷,保证了机组安全运行也取得了较好的经济效益,对异种钢焊缝小径管超声波检测具有较强的借鉴意义。     

电磁超声技术在焊缝检测中的应用

电磁超声技术利用洛伦兹力或磁致伸缩原理在金属或磁性材料中激发出超声波,它是一种超声无损检测新技术。相对于其他无损检测技术而言,电磁超声具有所有的超声检测的优势。声波的激发发生在材料的表面而不是在传感器内部。所以它与传统的基于压电换能器的超声检测相比,具有无需耦合剂、可非接触、可适用于超低温或超高温环境、有利于工业自动化以及可方便有效地实现横波检测及导波检测等优势。Innerspec Technologies公司致力于电磁超声技术的研发和应用,在近十几年中开发了150多台工业在线电磁超声检测系统,广泛应用于钢铁、汽车制造、石油天然气管道和压力容器等领域。作为一种超声波技术,电磁超声可以应用于各种厚度测量、缺陷检测以及材料表征。举例讨论了电磁超声在焊缝检测中的应用。第一个应用是利用导波对激光拼焊板的检测。第二个应用是电阻焊钢管的在线检测。利用沿着周向传播的超声导波对焊缝进行检测,克服了由于焊缝位置偏转对传统超声焊缝检测设备带来的困难。第三个应用是水平横波以及多通道电磁超声相控阵技术实现奥氏体不锈钢焊缝的检测。     

A comparative evaluation of ultrasonic testing of AISI 316L welds made by shielded metal arc welding and gas tungsten arc welding processes

Ultrasonic testing of austenitic welds prepared by two different welding processes is studied in this paper. The two welding processes considered are shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW) and the ultrasonic testing technique used is time-of-flight diffraction (ToFD). Identical artificial flaws were implanted in both welds during the welding process. Austenitic characteristics consisting of grain orientation distribution and anisotropy show that the GTAW specimen is more isotropic than the SMAW due to the orientation of its grains. Moreover, comparison of echo amplitudes shows higher attenuation for the weld prepared by the GTAW process. The specimens were examined by the ultrasonic ToFD technique under identical conditions. B-scan images obtained from ToFD measurements of the two welds indicate that inspection of the specimen prepared by the SMAW process is easier than the one made by the GTAW process due to higher scattering of waves in the latter. The measurements also showed that the probe positioning is very important in the detection of diffracted echoes when using the ToFD technique.     

焊接工艺对9Ni钢焊缝超声检测的定量影响

从超声检测的定量对比出发,研究焊接工艺对9Ni钢焊缝超声传播性能的影响,探讨焊缝组织及晶粒度大小的变化对9Ni钢超声检测定量结果的影响,为优化9Ni钢超声检测工艺、提高缺陷超声波定量检测的精度提供依据。选用药芯焊丝电弧焊(FCAW)与手工电弧焊(SMAW)的焊缝进行超声检测结果的定量对比,分析了两种焊接工艺成型的焊缝与母材上同样缺陷的定量结果差异,并分析了检测中产生误差的原因。     

反应堆压力容器安全端异种金属焊缝超声检查技术

堆焊层、奥氏体粗晶材料的存在以及焊缝几何结构的复杂性使得反应堆压力容器安全端异种金属焊缝的超声检查非常具有挑战性。为提高安全端异种金属焊缝超声检查的可靠性和检查效率,利用常规双晶纵波检查技术及相控阵检查技术开展了安全端异种金属焊缝超声检查技术研究。试验结果表明,常规双晶纵波检查技术及相控阵检查技术均可有效检出安全端异种金属焊缝中的缺陷,且缺陷定量精度满足相关规范要求。其中,常规双晶纵波检查技术现已应用到核电站的役前检查及在役检查中,相控阵检查技术的缺陷定量精度及检查效率均优于常规双晶纵波检查技术。     

NUMERICAL SIMULATION OF ULTRASONIC NONDESTRUCTIVE TESTING FOR WELDS

A computer simulation technique for ultrasonic propagation is utilized for the simulation of ultrasonic nondestructive testing (NDT).In this paper,one goal of the simulation is to compute ultrasonic field radiated by arbitrary transducers into pieces under examination.The other simulates a testing experiment.The simulation approach is based on the model for the computation of the ultrasonic field in isotropic media radiated from actual NDT transducers.After the field is known, remaining to be modeled is the interaction between this field and the scatters (defect) and the echo structure. The model of beam-defect interaction is based on the Kirchhoff‘s diffraction approximations theory applied to elastodynamics.We assumed that the incident wave fronts on the defect are plane in the case of a focused immersed transducer and material is isotropic and homogeneous.The simulating results demonstrate that the model in ultrasonic NDT of welds is practical in further research and useful in optimizing testing configurations.     

奥氏体不锈钢焊缝中超声波衰减对缺陷定量的影响

奥氏体不锈钢焊缝中,超声波衰减严重,此衰减对缺陷定量有很大的影响。为了对缺陷准确定量,给出了计算衰减和缺陷定量的三种方法。     

奥氏体不锈钢焊缝的超声波检测方法研究

研究了奥氏体不锈钢焊缝组织结构的特性和不同振动类型超声波对大厚度奥氏体不锈钢焊缝的作用，通过试验得到了一种有效的超声波检测奥氏体不锈钢焊缝中缺陷的定量方法，即二维距离波幅表法。该方法显著减小了一维定量法所产生的较大误差，在一定程度上解决了由于奥氏体不锈钢焊缝的各向异性和组织粗大引起的缺陷无法定量的问题，提高了检测结果的准确性。