Latest Branch News

News from the Institute Branches – June 2017 

| Yorkshire Branch
Phased array testing and the use of NDT data

John Moody reports

Dr Richard Freemantle of Wavelength NDT Ltd was able to present at the rearranged Yorkshire Branch meeting. The presentation was titled ‘Phased array testing’ and subtitled ‘The use of NDT data to support process development/tuning, mechanical testing and effect-of-defect FE analysis’. Interestingly, Richard initially studied music and electronic engineering and gained a degree in this followed by a PhD in ultrasonics in NDT and the different uses of sound. He has, since 2005, had his own consulting company, Wavelength NDT Ltd.

There are several NDT techniques that Richard is involved with in the oil & gas, aerospace, green energy and marine sectors, in particular ultrasonic phased array testing.
The oil & gas sector was looking towards using composite pipes for deep-water wells, where the pipe needs to be over 3 km long and steel would weigh too much. The thermoplastic composite pipe is manufactured as one length and ultrasonics can be used to monitor the manufacturing process, allowing for immediate repair of any section that has a flaw. This process relies on both heat and pressure and the ultrasonic testing can indicate a lack of consolidation, which can be repaired by reheating and the reapplication of pressure. Due to the current low oil and gas prices, development work in the deep-water exploration sector has slowed down.

Within the aerospace sector, the use of composites has become an accepted manufacturing process but the components are still typically over-engineered as the full benefits of the material are not being exploited, in particular the potential saving in weight. Composites do not degrade like metallic materials and this is one of the main reasons the aerospace sector is using them. With confidence in the inspection techniques and enhanced data, the weight savings that could be achieved with improved modelling and design are significant and this is where Richard is developing and proving suitable imaging techniques.

Green energy, or more specifically wind turbine blades, are also composite structures that require inspection both during manufacture and while in service. If the life of a blade can be extended by a third, the potential for profit is significantly increased. During the manufacturing process the internal spars are bonded to the outer shell and sometimes this process is unsatisfactory. Richard has developed a process that that can detect this, allowing for the repair of these areas. Currently, there are very few standards relating to the manufacture of the blades and it is often the manufacturer that decides what is acceptable. The blades are often modified during manufacture, so not all blades are the same. These blades can be in excess of 45 m long and Richard’s experience of testing at a height of 65 m made for an interesting inspection.

Marine applications are another area where composites are extensively used. In particular, this is the case for the Volvo Racing Yacht, the masts of which are between 30 m and 50 m long and the wall thickness only 3 mm to 5 mm. Richard has developed techniques that can find the flaws, but there still need to be standards developed for the classification of the flaws as either acceptable or rejectable. As a guideline, flaws less than the size of holes that may be drilled in the mast wall for rigging components are deemed acceptable. Other parts of the rigging use carbon fibre rods and these can fail internally, often not exhibiting any external indication of the cracks until it is too late. NDT can find these defects. Again, the hulls are made of composites and Richard has tested them and found defective areas.

With better NDT, structural engineers will more accurately detect flaw sizing and type. This will aid structural analysis using finite element analysis (FEA) and, in conjunction with other NDT methods, including thermography, micro-focus radiography and computed tomography, the understanding of the material and components will enable the better use of the materials.

Many thanks to Richard for a most informative presentation.

 



| South Wales Branch
Challenges and trends in multi-sector composite testing

Colin Macfarlane reports

On Wednesday 15 March 2017, the South Wales Branch convened at The Village Hotel, near Cardiff, for a presentation from Dr Richard Freemantle of Wavelength NDT Limited. The Branch was particularly grateful to Richard, who had accepted an invitation to speak at relatively short notice. The presentation was titled: ‘The challenges of multi-sector composite testing and future trends for manufacturing QA and NDT’.

Richard opened with a brief overview of his career. Following his first degree in electronic engineering and music he wanted to be a sound engineer with the BBC, but instead studied for a PhD in ultrasonics between 1992 and 1995 and then completed research in NDT between 1996 and 1997. With a feeling of ‘wanting to be closer to the workforce’, Richard helped to set up NDT Solutions Ltd (now part of Sonatest) and then went on to establish Wavelength NDT, an NDT inspection company focusing on advanced ultrasonic inspection of composite structures and components.

The presentation moved on to describe the differences between the highly-regulated aerospace sector and the significantly less regulated non-aerospace sectors in the NDT of composites. The aerospace sector’s accepted approach for the development of composite NDT inspection was described as ‘incremental’, beginning with coupons, then subcomponents, components and finally full-scale assemblies, all of which are controlled by appropriate regulations and standards.

The NDT challenges within the non-aerospace sector were highlighted and include:
  • The large variation in material responses, requiring different probe sizes, inspection set-ups, calibration and techniques
  • In-service testing requirements not considered in the design phase
  • NDT used in production not suitable for in-service testing
  • No standards or regulatory requirements
  • Multi-sector NDT stakeholders and conflicts in requirements between them.

Richard gave some interesting case studies from the oil & gas industry, wind energy and the exotic world of racing yachts. In each case, the importance in identifying the key stakeholders and demonstrating the value of NDT in terms of cost savings, shared costs and benefits to them was highlighted.

One example from the area of wind energy involved a challenge to develop an NDT inspection suitable for 45 m wind turbine blades in situ at a height of 65 m. 100% inspection of all surfaces is not possible in a case like this. The area of concern was identified as the shear web bonding to skin area. The design team was contacted to establish the largest defect acceptable. The inspection requirements involved scans at 0.5 m intervals for 20 m on both sides of the blade, before moving on to the next blade. A photo of Richard perched in a cherry picker 65 m up showed that this was not for the faint-hearted!

Here, the key stakeholders were identified as the insurer, investors, blade manufacturer, turbine manufacturer, designer and wind farm operator.

Further engagement with stakeholders involved life-extension decisions of NDT versus swapping the blades out, in addition to combining NDT technology with repair technology.

The final part of the presentation focused on future trends, including a better understanding of defects and their effect on serviceability, 3D imaging, holistic approaches, FE modelling, certification by simulation and, importantly, the development of standards and regulations within the non-aerospace sector. To this end, Richard is Vice Chair of the BINDT Composite Group. One of the aims of the group is to develop BINDT-approved training and examinations for composite inspection.

The Branch would like to express its gratitude to Dr Richard Freemantle for a very entertaining, informative and thought-provoking presentation. In addition, the Branch thanks its Honorary Secretary, Steve O’Brien, for all the necessary arrangements that made the evening possible.