焊缝无损检测现状设计外文文献翻译、中英文翻译、外文翻译

2024年2月7日发(作者：)

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NDT of Welds: state of the art

R.J. Ditchburn , S.K. Burke and C.M. Scala

Ultrasonics

Ultrasonics was introduced as an NOT technique for weld inspection in the 1960’s .Since

then, the technique has undergone extensive development and gained increasing acceptance.

Consequently, ultrasonics is now the major technique used for validation of welded structures

in many in-service inspection applications, eg in off-shore structures. In nuclear and pressure

vessel industries

and in a range of naval applications.

The emergence of ultrasonics as a preferred technique over X-radiography in these

in-service inspections is due both to inherent limitations in radiography and to actual benefits

in applying ultrasonics. As described above, radiography is excellent for identifying

volumetric defects but is limited in its ability to detect or size planar defect, such as cracks,

which are likely to be the more serious defects type. Ultrasonic waves are scattered by planar

and volumetric defects, making the ultrasonic technique useful for detecting and sizing both

types of defects. Even closed cracks are detectable by ultrasonic. Provided that appropriate

procedures are used.

Ultrasonics also readily gives depth information concerning a defect,

whereas for X-rays, specialized and expensive techniques such as computer tomography are

needed to obtain such information. Ultrasonics also offers benefits over radiography in terms

of cost savings through increased productivity. Finally, in the 1990’s the increasing concerns

about radiation safely are a severe disincentive to the continued use of X-radiography.

In the last few decades, ultrasonics has developed from a purely manual technique to a

manual technique with computer-assisted processing to the use of automatic scanners and

more recently to the development of fully automated systems incorporating multiple

piezoelectric studies on the use of this range of increasingly sophisticated systems for defect

detection have formed a major factor in establishing the credibility of ultrasonics for weld

inspection. Studies such as the Programme for Inspection of Steel Components (PISC)

ultrasonic inspection in the nuclear and pressure vessel industries. Outside the PISC studies,

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useful work has been carried out to determine reliable procedures for inspecting specific weld

geometries including single-V and double-V welds and also compared the reliability of

radiography vs. ultrasonic inspection

Overall, the results of the reliability studies indicate that

the probability of detecting a defect with ultrasonics increases with the degree of

sophistication of the system. According to Lebowitz and DeNale the results also indicate that

manual ultrasonic procedures, can be expected to reject an equal or greater percentage of the

discontinuities present than will radiography.

Ultrasonic validation of welded structures requires not only reliable defect detection but

also sufficiently accurate defect location and sizing to allow acceptance/rejection criteria to be

correctly implemented Manual ultrasonic systems usually rely on the use of amplitude

dependent techniques for defect sizing. Techniques commonly used are the 20dB drop (shown

in Figure la), the 6dB drop, or comparison with the amplitude form a drilled hole. However

these techniques are known to be inaccurate. The inaccuracies are caused not only by the

effects of defect shape, orientation and location, but also by attenuation, coupling, resolution

and equipment characteristics. The incorporation of computer-assisted processing into

ultrasonic systems has allowed the easy implementation of potentially better methods for

defect detection and sizing such as time-of-flight-diffraction (TIFD) (see Figure 1b),eg in

PISCⅡ the addition of TOFD to standard procedures gave nearly perfect results in terms of

required rejection rate for-defects. Important advances in defect sizing have also been made

possible by the incorporation in automated ultrasonic systems of ultrasonics imaging based on

Synthetic aperture focusing (SAFT) and variants such as SUPERSAFT.

The development of reliable procedures for the application of ultrasonics to weld

inspection had required an understanding of the interaction waves with the various types of

weld defects, of wave propagation in complicated geometries, of particular problems caused

by inspecting for defects close to the surface of a structure of the effects of cladding and other

micro structural influences influences on wave propagation. While wave propagation in

ferritic and light-alloy welds Is relatively uncomplicated, the microstructures of austenitic

welds have caused special concerns. These materials strongly attenuate ultrasonic waves,

cause high background noise due to scattering from the large grains present, and result in

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skewing of the ultrasonic beam unless the propagation is along principal crystallographic

(a) 20 dB Drop Technique (b) TOFD Technique

Figure 1 Ultrasonic defect sizing (a) The 20dB intensity drop technique. Where the transducer is

positioned at points is used along with probe calibration characteristics to estimate the defect length.(b)

Time-of-flight-diffraction (TOFD) technique. A two probe technique used to determine crack size and

location utilizing the diffracted waves from the tips of the defect.

axes. Thus, much recent research has been directed toward the development of specialized

ultrasonic techniques to deal with these complications. Considerable progress has already

been made, especially under PISCⅡ and Ⅲ where detailed has been undertaken. In the future,

these models should allow more accurate estimation of location and sizing errors for specific

defects, and provide the basis for improved codes for inspection of austenitic steels and weld

steels.

In today’s world, there is an increasing need to minimize the cost of weld inspection. The

advent of automated scanners, the use of multiple probes and computer-assisted processing in

modern ultrasonic systems have reduced costs by increasing both the speed and reliability of

inspection. On the negative side, equipment, and calibration costs are higher with automated

equipment. Also, the costs in actually interpreting ultrasonic data could rise due to the recent

advances in ultrasonic systems, since all types of defects and even very small defects can be

detected, whether or not the defects are critical. The solution to this problem would be

improvements in the automated application of acceptance/rejection criteria on defect

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criticality. Hence, considerable effort is now being directed towards the development of neural

networks to be used in ultrasonic systems to classify defect type, size and location, and

resulting conformance with a particular inspection code. Very promising results have already

been obtained in several laboratories in studies both on simulated weld defects, where a 100%

correct classification rate was achieved in defect type, and on real weld defects where success

rates of the order of 90% were achieved using a variety od methods. Preliminary work has

also been made in the automated application of acceptance/rejection codes via neural

networks.

Clearly neural networks will only prove successful if they can be trialed on

representative data. However, representative data can prove expensive to acquire. For

example, the PISC programme is currently costed at ＄200M, and it seems unlikely that this

type of effort will be duplicated in other industries in the near future. An alternative approach

would be to trial the networks using data generated from robust mathematical models of the

interaction of ultrasonic waves with weld defects. The development of such models is a

continuing PISC objective under PISCⅢ。 Until these mathematical models are more

complete, an emphasis staff seems necessary and technically qualified staff seems necessary

for ultrasonic weld validation.

For the future, many challenges remain in optimizing ultrasonic inspection of welds.

Substantial improvements are possible in the application of neural networks has only just

started. Various options exist for the improved generation and detection of ultrasonic in

welding applications, eg by the use of phased arrays, laser techniques (as described below)

and other specialist probes. A number of additional factors need to be considered in the

ultrasonic reliability area, eg residual stress, the effect of higher frequencies, more extensive

consideration of real rather than simulate defects.

Greater consideration also needs to be given to the overall cost effectiveness of

inspection. One of the elements in maximizing cost-effectiveness is the selection of the most

appropriate techniques for a given inspection, including the possible use of more than one

technique to validate different parts of a welded structure. For example, magnetic particle

testing is already used in conjunction with ultrasonics for rapid and cost-effective detection of

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surface cracks in welds. New electromagnetic methods could also have a role to play here (as

discussed in the following section). Finally, there are clearly challenges in implementing

advances in ultrasonic inspection technology into the codes for weld validation.

In-production weld inspection

On-line monitoring and control of the welding process has the potential to improve weld

quality and increase productivity in automated welding. Weld monitoring and control can be

achieve by the integration of real-time nondestructive evaluation techniques with the welding

process. In-production weld inspection can improve weld quality and may provide a

significant cost reduction. The welding parameters can usually be adjusted to prevent defects

do occur the flaws can be found and repaired before they are covered by subsequent welding

passes, leading to a decrease in the level of post-weld inspection and repair.

Good quality welds rely in the correct weld pool size geometry and position relative to the

weld preparation. In-production automated weld monitoring systems usually have sensors

providing information on the stare of the weld pool. Using this information and determining a

relationship between the stare of the weld pool and at least one of the critical welding

parameters (eg current, voltage, torch position and travel speed) the welding process can be

adjusted by a feed-back loop from the process parameters to maintain the desired stable

process state. This can be achieved with little operator intervention.

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Figure 3

Schematic diagram depicting the principle of introduction monitoring of the welding process

The dynamic nature of welding means that data acquisition and processing, must be

rapid enough to extract useful information before any major change occurs in the welding

process. A two-step real-time radiographic analysis involving a fast search for defective

regions followed by fine identification and location of defects has achieved this requirement.

Real-time radiographic images have been used in the control of arc welding conditions in

butt-joint welds. A combined approach using real-time radiographic images of the weld

immediately behind the pool was used for weld penetration and quality control.

In-production 371678 sensing has been used to determine the quality of both gas metal

arc (GMA) and gas tungsten arc (GTA) welding processes. This technique allows detection of

weld pool geometry and weld defects in real time. The technique evaluated the solidified weld

metal behind the electrode. Two types of discontinuities were detected: incomplete sidewall

penetration and porosity. These discontinuities were distinguished from sound welds using an

expert-system technique with a success rate of 92%. Unfortunately the expert-system

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algorithm was unable to discriminate between the discontinuity types as successfully. Porosity

was identified correctly 70% of the time and incomplete sidewall fusion was correctly

identified 63% of the time. But et al, have shown that CTA and resistance spot-welding can be

monitored ultrasonically and are making progress in developing an in-production monitoring

system for resistance spot-welding.

Using a piezoelectric transducer and complaint presents the possibility of contamination

of the weld by the coupling medium, obviously impractical for production. To overcome this

problem, a non-contact ultrasonic system has been developed. The system developed uses a

pulsed Nd: YAG laser for ultrasound generation and an electromagnetic acoustic transducer

(EMAT) for ultrasound reception.

Two other non-contact transducer are currently under investigation. The fist technique

involves the simultaneous observation of the infrared (IR) and the ultraviolet (UV) radiation

from the welding process using dual wavelength fiber-optic sensors. The radiation is produced

both from the hot melt pool and from the plasma produced by the beam/vapour interaction.

The technique has been successfully employed to indicate disturbances encountered in laser

welding. The second technique uses in-production processing of video images. Encouraging

results have been reported that provide weld joint area and bead centerline cooling rates in

GMA welding. This information is then used by a fuzzy logic controller and an artificial

neural network to modify process parameters.

The increasing demands of high production rates and greater weld quality at lower costs

will necessitate the strengthening of the bond between the technologies of welding and

nondestructive inspection. In achieving these goals, in-production monitoring of the welding

process will increase in importance and may well become indispensable.

Conclusions and future work

In recent years some exciting developments have occurred in NDT techniques for weld

inspection. Major advances have been made in several fields particularly in ultrasonics,

electromagnetic methods for both crack sizing and residual stress measurement, and in

on–line monitoring of the welding process.

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Many of the advances in NDT techniques have been driven by today’s increasing

pressures for cost-effective weld inspection. Cost effectiveness is linked to factory such as

reliability, sensitivity speed and coverage of NDT techniques. The need for greater reliability,

speed and coverage has resulted in the increasing use of automated ultrasonic systems for

weld inspection particularly in the nuclear application. Rapid development has occurred in a

range of non-contact NDT techniques which should improve speed of inspection in the future,

as will the continuing development of neural networks for automated data processing.

Worldwide, the need exists to implement these advance in NDT technology in weld

validation codes. Clearly there is no value in replacing an acceptable inspection method for

the sake of technological sophistication alone. However, substantial improvements are

possible by the incorporation of advanced concepts such as Time-of-Flight-Diffraction in

weld inspection.

In conclusion, many challenges remain in NDT of welds, particularly in minimizing

inspection costs without prejudicing structural integrity. These challenges are best met by

close cooperation between welding engineers and NDT experts, so that best practice is

achieved based on a knowledge of not only NDT but also weld manufacture, fracture

mechanics and structural mechanics.

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焊缝无损检测现状

[澳大利亚] RJ Ditchburn SK Burke CM Scala

超声检测

20世纪60年代，超声检测就被作为焊缝检验的一种NDT技术。从那时起，这种技术就得到广泛的发展，日益被人们所接受。因此，超声检测现已成为一项重要技术，用来判定很多在役检验的焊接结构，如海上结构、核工业及压力容器工业，以及海洋应用的某一范围。

在在役检验方面，超声检测之所以比X射线照相更受欢迎，是由于射线照相的内在局限性和应用超声所获得的实际利益。如上所述，射线照相在辨别立体缺陷时非常有效，但在检查或测量平面缺陷，有可能是最严重的缺陷类型裂纹时，其能力则有限。超声波经平面和立体缺陷散射，可用于探测这两种类型缺陷，并测量其尺寸，如果采用适当的方法，超声甚至能探测出闭合的裂纹。超声还能容易地给出与缺陷有关的深度信息，而X射线，还需专门且昂贵的技术（如CT）才能获得这些信息。在节约资金方面，通过提高生产率，超声检测比射线照相可获得更大的利益。90年代，人们对射线安全性的日益关注严重阻碍了X 射线照相的继续使用。

在过去的几十年里，超声检验已从一种单纯的人工操作技术，经过计算机辅助处理的人工操作技术，到自动扫描仪的使用，最近发展为焊缝评估用联接多个压电传感器的全自动系统。对日益完善的系统在缺陷探测方面应用的可靠性研究已形成建立超声焊缝检验可信度的一个重要因素。如对钢构件检验方法（PISC) I ,Ⅱ和Ⅲ进行研究的目的是要获得超声检验在核工业和压力容器工业中的最佳应用。在PISC研究之外，已进行了某些工作来确定检验特殊焊缝几何形状的可靠方法，包括单面V形坡口焊缝、双面V形坡口焊缝以及对接焊缝。这些研究中的几项已用射线照相和超声检验的可靠性作了比较，结果表明，用超声探测缺陷的可靠性随着该系统完善的程度而增大。根据Lebowitz

和DeNale，该结果还表明人工操作超声技术，甚至使用最不完善的超声方法，对存在的不连续处的拒收率等于或大于射线照相的拒收率。

超声检测焊接结构要求不仅能可靠地探测缺陷，而且能精确地对缺陷定位和测量其大小，使接收／拒收准则能够正确实施，人工操作的超声系统通常使用的技术是20dB

辽宁科技大学本科生毕业设计 第10页

衰减（图la）、6dB衰减或与来自钻孔的幅度比较。然而，这些技术都有误差，这种误差不仅是由缺陷形状、方向和位置的影响引起的，而且还由衰减、耦合、分辨力及设备特征引起。结合计算机辅助处理的超声系统使得用于缺陷探测及测量的好方法如声时衍射法( TOFD)（图lb）便于实施，在 PISCⅡ中，标准方法加上TOFD，对所要求的缺陷拒收率，可得到近乎完美的结果。在测量缺陷大小方面，根据合成的小孔聚焦（SAFT）及其派生方法如 SUPER – SAFT。进行超声成像的自动超声系统已取得了重要进展。

（a）20dB衰减技术

（b）TOFD技术

图1 超声测量缺陷尺寸

对于焊缝超声检验可靠方法的开发要求了解声波与各种类型焊缝缺陷的相互作用、超声波在复杂几何体中的传播、检验某一结构中表面闭合缺陷所引起的特殊问题、复合层和其它显微组织对超声波传播的影响。虽然超声波在铁素体和轻质合金焊缝中的传播相对来说不是很复杂，但对奥氏体焊缝的显微组织已引起特别注意。这些材料对超声波的衰减很严重，由于存在大晶粒散射而使背底噪声高，除非沿着主要晶轴传播，否则还导致超声波束的偏移。因此，最近的研究已直接面向开发专门的超声技术去处理这些复杂情况，特别PISCⅡ,和Ⅲ对超声波在奥氏体材料中传播的详细模拟试验，已取得了重大进展。将来，这些模型应能更精确地估算特殊缺陷的位置和大小误差，为奥氏体钢和奥氏体焊缝钢检验采用改进的规则奠定基础。

目前，人们对降低焊缝检验成本的需求日益增长。在现代超声系统中，自动扫描仪的出现、多个探头的使用及计算机辅助处理通过提高检验速度和检验的可靠性降低了成本，但使用自动化设备时，设备和校准费用增高了。同时、由于近来超声系统的发展，分析超声数据的费用有可能提高，因为各种类型的缺陷（甚至很小的缺陷）都能探测到，而不管这些缺陷是否严重。对这个问题的解决方法就是改进缺陷严重性接收／拒收准则

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的自动化应用。因此，现在要努力开发神经网络，使其用于超声系统中对缺陷类型、尺寸和位置进行分级，得出的结果符合特定的检验规则。在模拟的焊缝缺陷（已获得100％正确的缺陷类型分辨力）和真实的焊缝缺陷（使用不同方法获得约为90％的成功率）研究方面，一些试验室已获得非常有价值的结果。借助于神经网络，接收／拒收准则在自动化应用方面的预备工作也已进行。神经网络只能在有代表性的数据上试用后，才能证明它们是成功的。然而，获得代表性数据的费用很高。一种替代方法，是在网络上采用从超声波与焊缝缺陷相互作用的加强数学模型产生的数据。这些模型是PISC Ⅲ下一个PISC继续项目的开发。在这些数学模型变得更完善之前，对于焊缝的超声判定，强调使用合格的科技人员是有必要的。

今后，进一步优化焊缝超声检验仍有很多困难，先进方法如TOFD的应用有可能取得实质性的改进，同时，神经网络的实施还只是个开始。在焊接应用中，改进的超声产生和探测有多种选择方法，如使用相控阵、激光技术（如下所述）和其它特种探头。在超声可靠性范围内需考虑其它一些因素，如残余应力、较高频率的影响及对真实缺陷而不是模拟缺陷更全面的考虑。

对检验的总经济效益也应给予更多的考虑。要获得最大经济效益就需对所给的某项检验选择最适合的技术，包括使用一种以上的技术来判定焊接结构的不同部位。例如，磁粉检验与超声结合快速而经济有效地探测焊缝表面裂纹。新的电磁方法在这种情况下也起着作用（如下面所讨论的）。还存在的问题是如何将超声检验技术的进展补充到焊缝判定规则中。

在线焊缝检验

在自动焊接过程中，焊接工艺的在线监测和控制能提高焊缝质量并增加产量，通过实时无损评价技术与焊接工艺的结合，可达到焊缝的监测和控制。另外，如果产生了焊接缺陷，则在这些缺陷被后续焊道覆盖前，对这些缺陷进行修补以减少焊后的检验和修补。

高质量焊缝取决于与焊接准备工作有关的正确的焊池尺寸、几何形状和位置。在线自动焊缝监测系统通常具有可提供焊池状况信息的传感器。利用这些信息，确定焊池状况与至少一个临界焊接参数（如电流、电压、焊距位置和传送速度）间的关系，通过传感器的反馈线路调整焊接工艺（图3）。该系统可连续调节工艺参数来维持期望的稳定工

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艺状态，且不需要操作人员介入。

图2 描述焊接工艺引入检测原理示意图

焊接的动态特征意味着数据采集和处理必须能迅速获得焊接过程中的有用信息，两级实时射线照相分析包括快速寻找缺陷区域，并对缺陷进行仔细辨别和定位的系统已达到这个要求。实时射线照相图像已用于对接接头焊缝电弧焊条件的控制；焊池凹陷的实时射线照相图像和池后焊缝迅速固化图像的综合方法可用于焊缝熔透和质量控制。

在线超声传感已用于确定金属极气体电弧焊(GMA)和钨极气体保护电弧焊（GTA）焊接工艺的质量，这种技术可实时探测焊池几何形状和焊缝缺陷。该技术评价了焊条处熔化的焊池质量和焊条后固化的焊缝金属质量，可探测侧壁不完全熔透和密集气孔。使用具有92％成功率的专家系统技术可将这些不连续与完好焊缝区分开来，遗憾的是这个专家系统的算法不能成功地识别不连续的类型。正确辨别密集气孔的比率为70%，正确辨别侧壁不完全熔化则为63％。Bull 等人已表明GTA和电阻点焊可用超声法监测，并在电阻点焊在线监测系统开发方面有所进展。

使用压电传感器和耦合剂因存在耦合介质使焊缝不纯净，对生产是不利的，为了解

辽宁科技大学本科生毕业设计 第13页

决这个问题，已研制出一种非接触式超声系统。该系统用一种受脉冲作用的钕YAG激光来产生超声波，用电磁声传感器（EMAT）接收。

另外，两种非接触检测技术正在研究过程中，第一种技术使用双波长光导纤维传感器可同时观察来自焊接过程的红外线（IR）和紫外线（UV），射线由热熔池和由光束/气体相互作用发出的等离子体产生。这种技术已成功地用于显示激光焊中所遇到的干扰。第二种技术使用录像图像在线处理，它可保证GMA焊接中焊缝接头区和焊道中心线的冷却速率，模糊逻辑控制装置和人工神经网络可用这个信息来修改工艺参数。

结论及今后的工作

近几年在焊缝NDT技术方面已取得了重大进展，特别是用超声和电磁方法测量裂纹尺寸和残余应力，以及焊接工艺的在线监测方面。成本效益与诸多因素有关，如NDT技术的可靠性、灵敏度、速度和覆盖面，这些方面的要求导致焊缝自动超声检验系统的应用得以扩大，特别是在核工业和压力容器领域。非接触式NDT技术已取得迅速发展，今后在自动数据处理的神经网络不断发展的同时，还应提高其检验速度。

总之，焊缝NDT特别是在使检验成本降至最低而不损坏结构完整性方面，仍有很多难题，通过焊接工程师与NDT专家之间的密切合作，这些难题正在得到解决，既具备NDT知识又具备焊缝生产，断裂力学和结构力学知识，是获得最佳效果的基础。