Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Detecting material defects in ship propellers

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:

More articles from Materials Sciences:

nachricht How nanoscience will improve our health and lives in the coming years
27.10.2016 | University of California - Los Angeles

nachricht 3-D-printed structures shrink when heated
26.10.2016 | Massachusetts Institute of Technology

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

How nanoscience will improve our health and lives in the coming years

27.10.2016 | Materials Sciences

OU-led team discovers rare, newborn tri-star system using ALMA

27.10.2016 | Physics and Astronomy

'Neighbor maps' reveal the genome's 3-D shape

27.10.2016 | Life Sciences

More VideoLinks >>>