Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Detecting material defects in ship propellers

02.04.2012
Ship propellers are as large as a single-family home – and manufacturing them is quite a challenge.

During the casting process, pores and miniscule cracks can form that in the worst case may cause a blade to break. Now these massive components can be inspected for defects in a non-invasive manner, using a new kind of ultrasound process.


Suction feet are used to attach the mobile scanner to the propeller. Researchers record the ultrasound test data on-site. © Fraunhofer ITWM

They can weigh up to 150 tons, and it’s not uncommon for them to measure nine meters or more in diameter: the ship propellers on huge tankers, container ships and cruise liners are invisible giants. Damage to these massive propellers could render a ship unmaneuverable – with unpredictable consequences for people and the environment. Many defects do not come from external influences, but instead originate in the production or repair process.

For example, when the molded parts are being cast, any turbulence could lead to sand inclusions and pores. Left undetected, critical imperfections could lead to breakage of a blade.

Until now, propellers have been inspected manually for inner defects when necessary. To make them visible, the inspector guides an ultrasound test probe over the component by hand – an error-prone procedure that fails to capture the entire volume of the component. This method cannot detect cracks inside the propeller in certain circumstances.

To identify defects in a timely manner, researchers at the Fraunhofer Institute for Industrial Mathematics ITWM developed a mechanized ultrasound process that can be used for the non-destructive testing of complex components. The scientists received support from the GL Group (Germanischer Lloyd) and propeller manufacturer Wärtsilä Propulsion Netherlands.

Mobile scanner can be positioned freely

“With our mobile ultrasound test system, we can inspect copper-nickel-aluminum bronzes up to 450 millimeters thick and detect fissures down to a few millimeters in length. Because we emit the ultrasound at defined angles, we also find defects positioned at an angle to the surface”, says Dr. Martin Spies of ITWM in Kaiserslautern. The system is capable of recording large volumes of digitized ultrasound test data, taking into account the many and variously intense curvatures of the propeller surface.

The device currently scans test grids of 700 by 400 millimeters, achieving a rate of up to 100 millimeters per second. The mobile scanner can be positioned anywhere on the propeller, and, thanks to its suction feet, it can be attached in a horizontal as well as vertical test position. “We obtained the 3D data about the inside of the component by an imaging procedure known as SAFT. It provides a detailed display of inclusions and welding-seam defects. It basically works like computer tomography in medicine,” explains Spies.

With the aid of special computational processes and algorithms, the experts have succeeded in reducing interference signals and intensifying error signals – a complicated task, since the various areas of the blade do not have a homogenously coarse grain. This can weaken the echo substantially. The specialists also use simulations to calculate in advance which ultrasound test probe they have to deploy.

The researchers use the mobile scan system for their on-site testing at foundries, at propeller manufacturers, on deck and in dry dock, and are currently improving scan times and 3D defect imaging. Only recently, they were able to put the efficiency of their procedure to the test at the world‘s largest shipbuilder in Korea. “The customer wanted to document the quality of its propellers, to gain an edge over the competition,” says Spies.

“With our procedure, we can test not only propellers but also other complex components made of materials that are difficult to test, like offshore components made of duplex steels,” he stressed. ITWM researchers Alexander Dillhöfer, Hans Rieder and Dr. Martin Spies recently received the Innovation Award from the Deutsches Kupferinstitut for their outstanding accomplishments with copper and its alloys.

Franz Miller | Fraunhofer Research News
Further information:
http://www.fraunhofer.de/en/press/research-news/2012/april/detecting-material-defects-in-ship-propellers.html

More articles from Materials Sciences:

nachricht Let the good tubes roll
19.01.2018 | DOE/Pacific Northwest National Laboratory

nachricht Method uses DNA, nanoparticles and lithography to make optically active structures
19.01.2018 | Northwestern University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Let the good tubes roll

19.01.2018 | Materials Sciences

How cancer metastasis happens: Researchers reveal a key mechanism

19.01.2018 | Health and Medicine

Meteoritic stardust unlocks timing of supernova dust formation

19.01.2018 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>