Vision
The Vision of the aiCAMstir project was determined during a friction stir welding training course in Munich.
Summary
Some years ago, Stephan Kallee had worked on a project on making tailor welded blanks by friction stir welding. A new spindle, a new jig, two FSW experts and a new technician were available, who was experienced in operating milling machines but had not received in-depth training on parameter optimisation. Due to an unforeseen business trip, they worked on three different sites: in the lab, in the office and in a hotel. They could only communicate by mobile phone, sharing photos and information on the parameter settings. After a few iterations, optimised parameters could be found.
A few years later, he considered using neuro-networks for optimising FSW parameters. During a training course in Munich, the concept of using artificial intelligence in computer aided manufacturing was discussed in more detail and a project with very promising results was conducted.
In the aiCAMstir project we want to go one step further. We want to create a cloud, into which FSW operators can upload images and information on parameter settings during feasibility studies, prototyping, production ramp-up and series production, and get feedback about the weld quality and recommendations on optimising the parameters. In the final stage, such a system would be integrated into the FSW machine, and the machine would optimise the parameters itself within boundaries set by the operator.
The vision was explained for the first time in public during an on-line discussion with students of the University of Liège on 19 April 2021.
The first welds
The first welds were made by a group of experts and trainees in Munich. The trainees could choose the parameters after discussions with the experts and found visually acceptable parameter settings after a few iterations. The parameter matrix investigated during the course is shown below:
The next step: Automated PAUT-TOFD
![](/images/thumb/7/77/Screenshot_of_ultrasonic_examination_by_Sonaflex%2C_%C2%A9_Pavel_Pashkov%2C_Nordinkraft_AG%2C_Creative_Commons_%E2%80%94_Attribution-ShareAlike_4.0_International_%E2%80%94_CC_BY-SA_4.0.png/530px-Screenshot_of_ultrasonic_examination_by_Sonaflex%2C_%C2%A9_Pavel_Pashkov%2C_Nordinkraft_AG%2C_Creative_Commons_%E2%80%94_Attribution-ShareAlike_4.0_International_%E2%80%94_CC_BY-SA_4.0.png)
The aiCAMstir concept might also be useful for PAUT-TOFD examination with the Sonaflex system. The Sonaflex system makes use of an industrially proven, automatic ultrasonic inspection system combining Phased Array Ultrasonic Testing (PAUT) and Time of Flight Diffraction (TOFD) developed by Nordinkraft AG. The aiCAMstir software could be modified to evaluate screenshots of the NDT data in the same way as processing optical photographs for automated quality control during friction stir welding. Please contact stephan.kallee@alustir.com to discuss this in more detail.
Concept for automatic examination by LRUT, PAUT or X-ray
![](/images/thumb/9/97/AiCAMstir_Concept_for_Long_Range_Ultrasonic_Testing_or_Phased_Array_Ultrasonic_Testing_during_Orbital_Welding_of_Pipelines_%C2%A9_Stephan_Kallee_CC_BY_4.0_using_a_photo_of_X_Niu_et_al%2C_CC_BY_3.0.jpg/530px-AiCAMstir_Concept_for_Long_Range_Ultrasonic_Testing_or_Phased_Array_Ultrasonic_Testing_during_Orbital_Welding_of_Pipelines_%C2%A9_Stephan_Kallee_CC_BY_4.0_using_a_photo_of_X_Niu_et_al%2C_CC_BY_3.0.jpg)
The aiCAMstir project proposes to investigate a new concept for in-process long-distance ultrasonic examination or film-free X-ray examination during friction stir welding or other welding processes with adaptive control of the process parameters.
Especially when laying pipelines on construction sites or on the high seas using the J-lay or S-lay method, the quality of the weld should be examined during welding. If weld defects are detected during the process, the parameters can be adaptively controlled, for example the welding speed can be reduced or the contact pressure increased, or a repair weld can be carried out in the same clamping, e.g. in case of wear or breakage of a friction stir welding tool.
State of the art
After welding of tubes and pipelines, non-destructive testing is required for many applications in order to evaluate and document the quality of the weld seam. Up to now, mainly X-ray examinations or phased array ultrasonic examinations have been carried out.
Phased array ultrasonic examinations are usually performed after welding or in-line at least several centimetres away from the rotating friction stir welding tool. Water or gel is required to couple the ultrasound, which is why the material to be examined must have cooled down at least to such an extent that the coupling medium does not evaporate in the area of the ultrasonic probe. For this reason, the phased array ultrasonic head runs at a distance of several centimetres or a pipe length away from the welding tool during in-line ultrasonic examination, making adaptive control of the process impossible.
For X-ray inspection of pipelines, in many cases a radioactive emitter or X-ray tube is inserted on a long rod into the pipe, which has previously been wrapped with an X-ray sensitive film. This is not possible during friction stir welding because the film cannot be wrapped 360° around the pipe because the welding tool makes the pipe circumference inaccessible in places. For this reason, the X-ray inspection is often staggered by one pipe length at the same time as the next weld. If defects are found, repair welding is difficult and time-consuming because accessibility for the welding head at the NDT station is usually obstructed by the NDT equipment.
Long-range ultrasound examination
![](/images/thumb/3/35/AiCAMstir_Concept_for_Long_Range_Ultrasonic_Testing_or_Phased_Array_Ultrasonic_Testing_during_Orbital_Welding_of_Pipelines_%C2%A9_Stephan_Kalleee%2C_CC_BY-SA_4.0_using_photo_of_Bundesanstalt_f%C3%BCr_Wasserbau%2C_CC_BY_2.0.jpg/530px-AiCAMstir_Concept_for_Long_Range_Ultrasonic_Testing_or_Phased_Array_Ultrasonic_Testing_during_Orbital_Welding_of_Pipelines_%C2%A9_Stephan_Kalleee%2C_CC_BY-SA_4.0_using_photo_of_Bundesanstalt_f%C3%BCr_Wasserbau%2C_CC_BY_2.0.jpg)
Long-range ultrasonic testing is a non-destructive testing method using guided ultrasonic waves. Compared to other NDT methods, guided waves can propagate over several metres with a relatively high sensitivity to defects in the structure. The general sensitivity range is up to 3% of the cross-sectional area, depending on the signal-to-noise ratio. Further optimisation of the inspection process with guided ultrasonic waves is possible. This can be done by optimising the transducer array.
In particular, depending on the resonance frequencies of the system to be examined, it may be advantageous to use sound waves instead of ultrasonic waves for in-process non-destructive testing. Long-range ultrasonic testing with multiple transmitters and receivers In an advantageous concept variant, multiple transmitters and receivers are used. These transducers are placed on the left and right (or above and below) of the joint or weld.
Especially in friction stir welding, it is also advantageous to use a set of transducers in the rotating tool spindle or near the spindle bearings. The sound or ultrasound generated with these can then be received and processed, possibly with a time delay, at various points. In arc or beam welding processes, it is advantageous to modulate the welding current or the laser or electron beam energy in the sonic or ultrasonic range to generate sonic or ultrasonic waves in the molten metal that can be received by various transducers or modulated for transmission.
Film-free X-ray
Filmless X-ray, i.e. digital radiography, is an advanced technology based on digital detector systems where the X-ray image is displayed directly on a computer screen without the need to develop chemicals or perform intermediate scans. The incident X-ray radiation is converted into an equivalent electrical charge and then into a digital image by a detector sensor. Compared to other imaging devices, the screen detector provides high quality digital images with a better signal-to-noise ratio and improved dynamic range, which in turn provides high sensitivity for radiographic applications. Flat panel detectors use two different approaches, indirect conversion and direct conversion. Indirect conversion flat panel detectors use an amorphous silicon photodiode array. Instead of a conventional flat panel detector, the system described here can advantageously use a concave screen detector whose inner diameter is slightly larger than the outer diameter of the tube.
Direct conversion detectors use a photoconductor such as amorphous selenium (a-Se) or cadmium telluride (Cd-Te) on a multimicroscopic electrode plate and offer the highest sharpness and resolution. The information on both types of detectors is read out by thin-film transistors. In the direct conversion process, when photons such as amorphous selenium strike the photoconductor, they are directly converted into electronic signals that are amplified and digitised. Since there is no scintillator, the lateral distribution of the photons is missing here, which makes for a sharper image. This distinguishes it from the indirect design concept. Automatic image evaluation can provide signals for adaptive control of welding process parameters
Microfocus X-ray inspection
Systems for microfocus X-ray examination differ from conventional X-ray examination in the precise focusing of the X-ray beam, typically in the millimetre range. The advantage is that it can produce radiographs with extremely high resolution. This means that images can be produced with high magnification, whereby even the smallest defects can still be detected well.
Macrofocus X-ray examination
Instead of microfocus X-ray examination, macrofocus X-ray examination can also be advantageous, e.g. with a 450kV Broad Focus system.
Adaptive control of welding parameters
The data obtained from the in-line non-destructive testing is automatically evaluated and used for adaptive control of the welding parameters.
Pipeline welding under construction site conditions
The system should be designed so that it can be used not only in the laboratory but also under construction site conditions. Depending on the requirements on site, the pipeline is either horizontal, vertical or diagonal.
Typical applications are under laboratory conditions, in factory buildings when manufacturing tubular products, in trenches when laying pipelines or pipelines on land, or laterally or above the trench, if necessary on transportable laying platforms. The process described here offers particular advantages on ships or platforms used for the production of underwater pipelines, riser pipes or flowlines, especially in the J-lay or S-lay process. The process is applicable in the manufacture of long pipelines that are wound onto a spool prior to laying, in particular for pipelines for oil, gas, water, waste water or data transport (e.g. for pipes, conduits and cables laid on land or under water).
Other industrial sectors
In addition to its use in pipeline construction in the oil and gas industry, the system presented here is ideally suited for the manufacture and laying of pipelines for energy transport (GIS and GIL), for drinking water and waste water pipelines, for rocket, satellite and aircraft construction as well as for the manufacture and sealing of containers for the transport or storage of nuclear waste. The process can also be used in plant construction, e.g. in refineries, gas separation plants and chemical plant construction, as well as in chimney and stack construction. It can also be used for load-bearing tubular structures in oil rigs, bridges or houses. It is also suitable for welding railway rails or wire ropes of suspension bridges or cable cars.
The process offers great advantages for lining wells or boreholes, especially those in oil, gas and water production, CO2 storage and geothermal energy, as well as tunnels, horizontal boreholes and mine tunnels.
Claims and Benefits
The aiCAMstir project proposes to investigate a method for in-process long range ultrasonic examination or film-free X-ray examination during friction stir welding or other welding processes:
- If desired, friction stir welding can be performed in-process with one, two or more non-destructive testing methods, i.e. simultaneously or sequentially with LRUT and X-ray.
- Instead of friction stir welding, the concept can also be used in combination with other welding processes, such as electron beam welding, laser welding, MIG/MAG welding or in hybrid processes such as laser-MIG-MAG hybrid welding.
- The results or signals of the in-line non-destructive testing are processed digitally or analogue and used as input variables for the adaptive control of the welding process used.
- Instead of conventional long-distance ultrasonic testing with one set of transducers placed in a ring on the circumference of the pipe, it is advantageous to use several sets of transducers for in-process ultrasonic testing.
- Instead of conventional ultrasound, low-frequency ultrasound or sound can also be used or detected. It is sometimes advantageous to change the frequency during the examination.
- The sound or ultrasound can also be generated with the aid of an electromagnetic induction coil, e.g. in a leading head for preheating or in a trailing head for slower cooling of the weld.
- The transducer sets can be placed, especially in friction stir welding, to the left and right (or above and below) of the weld, in the rotating spindle, near the spindle bearings or at suitable points on the welding machine.
- In arc, laser beam or electron beam welding, it is useful to modulate the welding energy in the sonic or ultrasonic range in order to generate sound or ultrasound in the molten metal which can be used, inter alia, for in-process non-destructive testing.
- Advantageously, the system described in the concept can also be used after the welding has been completed, for example to evaluate the quality of the weld end.
- The in-process non-destructive testing according to the concept is not only suitable for pipelines in which gases or liquids are transported, but is also suitable, among other things, for the manufacture or installation of gas insulated switches and gas insulated lines for the transmission of electricity (GIS and GIL). It proves itself both in the production in a factory and in the laying on the construction site. Other applications include the fabrication of round, oval or polygonal pipe or tank structures, particularly in the aerospace and nuclear industries.
- The concept can also be used in the welding of tanks for the storage of gases and liquids, in particular for the manufacture of liquefied natural gas (LNG) tanks made of aluminium or other materials, and in storage tanks for the storage of chemical or petrochemical gases or liquids.
- The concept can also be used in plant construction and for load-bearing tubular structures in oil rigs, bridges or houses.
- The concept can also be used for welding railway tracks or supporting cables of suspension bridges.
- For digital radiography, instead of a conventional flat screen detector, the system described here can advantageously use a concave screen detector whose inner diameter is slightly larger than the outer diameter of the tube.
- Two or more detectors may be used, since in orbital friction stir welding it is advantageous to use two friction stir welding tools offset by, for example, by 180°, or three offset by, for example, by 120°, or several offset by a suitable angle.
Please contact stephan.kallee@alustir.com if you are interested in investigating this innovative concept.