University: University of Strathclyde Supervisor: Dr Yashar Javadi, Prof. Gareth Pierce  Start date: October 2021

In April 2019, the RCNDE board meeting decided to fund a feasibility study project entitled “Test Samples to Support Developments in High Temperature In-Process Inspection”. The PI was Dr Javadi and based on the industrial partners voting, the project had been ranked 1st among the other feasibility study proposals showing an initial strong interest to this topic from RCNDE industrial partners (i.e., Rolls-Royce, EDF, BAE System, BP, HITACHI, Shell, NNL, etc.). Dr Javadi delivered the final report in RCNDE board meeting in September 2020 when he presented the successful completion of the project with four journal papers [1-4], several conference papers and more importantly, the birth of a new innovative idea called “In-process Calibration” which is the main context of this PhD project.

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 [1]. 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, Javadi et al [3] presented a novel approach to calibration and introduced the concept of in-process calibration applied to ultrasonic NDT. The new concept was centered around the manufacturing of a second duplication sample, containing intentionally-embedded tungsten inclusions, with identical process parameters as the main sample [3]. Both samples were 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 was 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 [3].

However, the “in-process calibration” work had been supported by a short-term feasibility study fund from RCNDE and since it was found to be feasible, further investigations are now proposed in this PhD project. The idea was only tested on the multi-pass robotic welding and it was found that the following objectives are still required to be reached (which are the objectives of this PhD project):

1) The in-process calibration needs to be extended to the Wire Arc Additive Manufacturing (WAAM). This innovative approach will be tested in the RoboWAAM cell (which is the 1st NDE/WAAM robotic cell in the world). It will be an innovative challenging project but critical to support several multi-million pounds projects on the in-process inspection of WAAM components currently running at the University of Strathclyde.

2) It is required to automate the process of embedding artificial defects, tungsten balls and rods, to match the robotic NDE. This will then require a machining robot equipped with the propers gripper technology. Therefore, a new challenge with the integration of a machining/gripper robotic arm inside the in-process inspection robotic cell will be considered.

3) The welding and additive manufacturing process will be modelled using the finite element simulation to provide more comprehensive information on the thermal gradient required for the high-temperature in-process inspection and calibration.

Dr Javadi has been part of the weld modelling team at The University of Manchester (UoM) and published >20 journal papers in this field so the PhD student will have enough support in the area of process modelling (Objective 3). Furthermore, this project aligns directly with one key deliverable in the 5-year plan entitled “Towards Industry 4.0: In-process Repair of Welding and Wire Additive Manufacturing (IRWWAM)” associated with Dr Javadi’s fellowship which is a joint programme between the Department of Electronic & Electrical Engineering (EEE) and the Department of Design, Manufacturing & Engineering Management (DMEM)at the University of Strathclyde. The core of this ambitious plan is fully automated NDE in robotic welding and WAAM, where the three main research themes are: (I) in-process defect detection, (II) in-process residual stress measurement and (III) in-process material evaluation. When these three core research themes are coupled with the in-process calibration and also the process modelling, the project will deliver an Industry 4.0 adopted system in

which the sample can be fully inspected and importantly, repaired during the manufacturing process, if deemed necessary by the system. The in-situ measurement systems will be also linked to the manufacturing system for improving the quality control and creation of a closed-loop feedback system. Manufacturing within the IRWWAM framework will save time and energy (which is usually wasted in backward transmissions between the manufacturing and inspection stations) and hence will be better for the environment. The main plan is then in line with the national UK government post-COVID recovery plan and also NDEvR vision of Future Manufacturing NDE particularly new NDE 4.0/Industry 4.0 approach considering by the RCNDE management board.

Professor Gareth Pierce is Spirit AeroSystems/Royal Academy of Engineering Research Chair in the area of “In-process Non-destructive Testing for Composites”. He is also leading new Faculty Robotically Enabled Sensing (RES) laboratory and PI in many WAAM inspection projects, e.g., NEWAM which is a £10M EPSRC project or RoboWAAM which is the 1st commercial metal 3D printing machine in the world and is installed in Lightweight Manufacturing Center (LMC) as part of a strategic collaboration between National Manufacturing Institute Scotland (NMIS) and Advanced Forming Research Center (AFRC).

Therefore, the supervisory team are uniquely placed to bring together key research and KE infrastructure within Strathclyde and also through external links, as they can directly access a broad range of technical expertise and highly specialised facilities through (I) research-intensive Center for Ultrasonic Engineering (CUE), (II) WAAM facilities and programme (III) RES laboratory, (IV) Aerospace Innovation Centre (Prestwick) through collaboration with Spirit AeroSystems, (V) AFRC, LMC and NMIS, (VI) RCNDE academic and industrial membership, (VII) three aligned CDTs (FUSE, FIND and Photonics) and (VIII) DMEM facilities (given the Dr Javadi’s joint appointment).

In summary, there is a high degree of novelty in the proposed research plan. In particular, the high academic and industrial impact is expected from the idea of in-process calibration. Apart from the RCNDE and FIND-CDT academic/industrial partners, the PhD researcher will have a prime opportunity to have direct access to CUE, AFRC, NMIS, LMC, DMEM, RES lab and many more national and internationally leading research and industry-focused organisation.

References

[1] Y. Javadi, E. Mohseni, C.N. MacLeod, D. Lines, M. Vasilev, C. Mineo, E. Foster, S.G. Pierce, A. Gachagan, Continuous monitoring of an intentionally-manufactured crack using an automated welding and in-process inspection system, Materials & Design 191 (2020) 108655.

[2] Y. Javadi, N.E. Sweeney, E. Mohseni, C.N. MacLeod, D. Lines, M. Vasilev, Z. Qiu, C. Mineo, S.G. Pierce, A. Gachagan, Investigating the effect of residual stress on hydrogen cracking in multi-pass robotic welding through process compatible non-destructive testing, Journal of Manufacturing Processes (2020).

[3] Y. Javadi, N.E. Sweeney, E. Mohseni, C.N. MacLeod, D. Lines, M. Vasilev, Z. Qiu, R.K.W. Vithanage, C. Mineo, T. Stratoudaki, S.G. Pierce, A. Gachagan, In-process calibration of a non-destructive testing system used for in-process inspection of multi-pass welding, Materials & Design 195 (2020) 108981.

[4] E. Mohseni, Y. Javadi, N.E. Sweeney, D. Lines, C.N. MacLeod, R.K.W. Vithanage, Z. Qiu, M. Vasilev, C. Mineo, P. Lukacs, E. Foster, S.G. Pierce, A. Gachagan, Model-assisted ultrasonic calibration using intentionally embedded defects for in-process weld inspection, Materials & Design 198 (2021) 109330.

Funding: 

This studentship covers fees at the home/EU rate, a stipend of £16877 per annum and the full technical and professional training programme as part of the FIND CDT.