Continuous monitoring of an intentionally-manufactured crack using an automated welding and in-process inspection system

Automated weld deposition coupled with the real-time robotic Non-Destructive Evaluation (NDE) is used in this paper. For performance verification of the in-process inspection system, an intentionally embedded defect, a tungsten rod, is introduced into the multi-pass weld. A partially-filled groove (staircase) sample is also manufactured and ultrasonically tested to calibrate the real-time inspection implemented on all seven layers of the weld which are deposited progressively. The tungsten rod is successfully detected in the real-time NDE of the deposited position. The same robotic inspection system was then used to continuously monitor an intentionally-manufactured crack for 20 h. The crack was initiated 22 min after the weld ended and it grew quickly within the next 1.5 h. The crack growth stopped approximately after 2 h and no considerable change in the reflection signal was detected for the next 18 h of monitoring

In-process monitoring and control of multi-pass fusion welding using phased arrays

Many industrial sectors, such as nuclear and defence, employ high-integrity fusion welding processes for the manufacture of safety-critical components. Often these parts consist of thick-sections which necessitate the use of a multiple-pass weld deposition strategy. Ultrasonic Testing (UT) is a common volumetric testing technique used to ensure the safety of these components before they reach service. However, as testing traditionally occurs as a final step within the manufacturing timeline it is often regarded as a bottleneck in the supply chain, especially where defects are found in early weld runs which require a large amount of rework to correct. In recent years, there have been increasing economic and industrial drivers toward employing innovative in-process inspection techniques to reduce overall manufacturing costs and improve schedule certainty. Through in-process monitoring of the welding process, it is possible to detect the formation of defects at the earliest possible point to enable quicker, more cost effective repair. Here, traditional phased array ultrasonic technologies are used to monitor the deposition of a multi-pass Gas Tungsten Arc Welding (GTAW) process. Through processing and analysis of the received longitudinal ultrasonic signals, this technique is shown to be capable of inferring the suitability of the chosen welding parameters while screening for appropriate joint fusion. Crucially, this strategy is also shown to be effective at discriminating between solid lower and liquid upper passes in a multi-pass weld through appropriate phased array steering and focussing. This capability directly informs in-process inspection and monitoring and enables the potential for closed-loop control with the opportunity to correct for any defects as they are formed

In-process calibration of a non-destructive testing system used for in-process inspection of multi-pass welding

In multi-pass welding, there is increasing motivation to move towards in-process defect detection to enable real-time repair; thus avoiding deposition of more layers over a defective weld pass. All defect detection techniques require a consistent and repeatable approach to calibration to ensure that measured defect sizing is accurate. Conventional approaches to calibration employ fixed test blocks with known defect sizes, however, this methodology can lead to incorrect sizing when considering complex geometries, materials with challenging microstructure, and the significant thermal gradients present in materials during the inter-pass inspection period. To circumvent these challenges, the authors present a novel approach to calibration and introduce the concept of in-process calibration applied to ultrasonic Non-Destructive Testing (NDT). The new concept is centred around the manufacturing of a second duplication sample, containing intentionally-embedded tungsten inclusions, with identical process parameters as the main sample. Both samples are then inspected using a high-temperature robotic NDT process to allow direct comparative measurements to be established between the real part and the calibration sample. It is demonstrated that in-process weld defect detection using the in-process calibration technique can more reliably identify defects in samples which would otherwise pass the acceptance test using a traditional calibration

Complete two-loop effective potential approximation to the lightest Higgs scalar boson mass in supersymmetry

I present a method for accurately calculating the pole mass of the lightest Higgs scalar boson in supersymmetric extensions of the Standard Model, using a mass-independent renormalization scheme. The Higgs scalar self-energies are approximated by supplementing the exact one-loop results with the second derivatives of the complete two-loop effective potential in Landau gauge. I discuss the dependence of this approximation on the choice of renormalization scale, and note the existence of particularly poor choices which fortunately can be easily identified and avoided. For typical input parameters, the variation in the calculated Higgs mass over a wide range of renormalization scales is found to be of order a few hundred MeV or less, and is significantly improved over previous approximations.Comment: 5 pages, 1 figure. References added, sample test model parameters listed, minor wording change

Towards real-time ultrasound driven inspection and control of GTA welding processes for high-value manufacturing

Many industrial sectors, such as nuclear and defence, employ high-integrity welding processes for the manufacture of safety-critical, high-value components. Non-Destructive Evaluation (NDE) techniques are used to ensure the strength and safety of these components both before they reach service and throughout their service-life. Often these welded components are composed of thick-sections which necessitate the use of a multiple-pass weld deposition strategy. As a result of the traditional inspection approach occurring only after the deposition of all weld runs, defects which have been introduced in early weld runs remain undetected and buried until the final inspection. This greatly complicates the re-work procedure, increases material wastage and the associated costs as well as delaying early correction of improper process parameters. With the nuclear sector being called upon to play a significant role in the delivery of low-carbon energy production there has been an increasing drive to reduce manufacturing costs. The development and deployment of innovative in-process inspection and control strategies is one method being explored to help achieve this. Through in-process inspection and monitoring of the welding process, it is possible to detect the formation of defects at the earliest possible point to enable quicker, more efficient, and more cost-effective correction and repair. As the most critical weld run within any multi-pass weld is the root pass, it is vital that this be monitored precisely to ensure integrity of the welded joint. Here, the feasibility of using single element and phased array ultrasonic approaches to interrogate and analyse the molten weld pool during robotic deposition of a Gas Tungsten Arc Welding (GTAW) root pass of a common multi-pass weld joint (90 degree included bevel angle, 1.5 mm root face height and 3.2mm root gap) is explored. Through processing and analysis of the received shear and longitudinal ultrasonic waves, this technique is shown to be capable of screening root pass width and height and joint fusion, critically indicating lack-of root fusion. This capability directly informs in-process inspection and monitoring and enables the potential for closed-loop control with the opportunity to correct for any defects as they are formed. The concept of utilising a similar strategy for upper passes within multi-pass welds is introduced. Along with the wildly varying wave propagation path and associated impedance variations, the challenges encountered during discrimination of the solid lower and upper molten passes are presented along with suitable signal processing techniques to counteract for these

In-process phased array ultrasonic weld pool monitoring

In recent years, there have been increasing economic and industrial drivers for the development of real-time non-destructive evaluation directly at the point of manufacture. Real-time inspection and monitoring of welding processes can help to reduce fabrication costs by detecting defects as they occur, enabling more efficient and cost-effective builds. This paper shows, for the first time, the use of phased array ultrasonics to monitor and analyse the molten weld pool during deposition of multi-pass gas tungsten arc welds. The received ultrasonic signals are shown to contain information related to key physical transitions occurring within the welding process, namely the melting and solidification of the weldment. Furthermore, the technique used here is shown to be effective for determining weld quality in real-time with significant signal changes occurring when defects such as Lack of Root Penetration are present. The accurate focusing and steering capabilities offered by phased arrays are used to successfully isolate the molten weld pool from the surrounding solidified weldment during deposition of multiple layers of a multi-pass weld

Generalized messengers of supersymmetry breaking and the sparticle mass spectrum

We investigate the sparticle spectrum in models of gauge-mediated supersymmetry breaking. In these models, supersymmetry is spontaneously broken at an energy scale only a few orders of magnitude above the electroweak scale. The breakdown of supersymmetry is communicated to the standard model particles and their superpartners by "messenger" fields through their ordinary gauge interactions. We study the effects of a messenger sector in which the supersymmetry-violating F-term contributions to messenger scalar masses are comparable to the supersymmetry-preserving ones. We also argue that it is not particularly natural to restrict attention to models in which the messenger fields lie in complete SU(5) GUT multiplets, and we identify a much larger class of viable models. Remarkably, however, we find that the superpartner mass parameters in these models are still subject to many significant contraints.Comment: 24 pages, LaTeX, uses epsf.sty, 4 figures. Assumptions clarified, numerical bounds tweaked, typos correcte

High-temperature in-process inspection followed by 96-h robotic inspection of intentionally manufactured hydrogen crack in multi-pass robotic welding

This investigation introduces two new techniques to quantitatively address the challenging problem of understanding Hydrogen Induced Cracking (HIC) in welding processes. The first technique is a novel procedure to create a known and controlled HIC in a welded sample. The second is an in-process monitoring technique to measure the initial formation and subsequent growth of the HIC in a multi-pass weld whilst being compatible with the high temperatures associated with the welding process. The HIC was initiated using a localised quenching method of the weld and its character was verified using both macrograph and microscopic investigations. During HIC initiation and growth, the sample was monitored every 1–30 min for a total of 96 h using a custom non-destructive testing (NDT) system, mounted on a robot which ensured repeatable inspection positioning. Combining these techniques has therefore allowed for the first time, a detailed understanding of the evolution of HIC in a multi-pass welded sample. Our findings reveal that the HIC was initiated 43 min after the weld ended and that it then grew rapidly for about 15 min and continued growing at a slower rate for around 24 h. No significant growth was observed for the remaining 72 h of the experimental measurement