Featured Research

from universities, journals, and other organizations

Spotting weaknesses in solid wood

Date:
August 5, 2011
Source:
Fraunhofer-Gesellschaft
Summary:
Is there a hairline crack in the oak table? Was the window frame glued badly? Ultrasound thermography can reliably identify material defects during the production of wooden items. This allows rejects to be caught quickly and eliminated, and faulty goods to be repaired in good time.

The ultrasound agitator causes the wood to vibrate, which generates frictional heat wherever there are cracks. A thermal imaging camera shows these defects up.
Credit: Image courtesy of Fraunhofer-Gesellschaft

Is there a hairline crack in the oak table? Was the window frame glued badly? Ultrasound thermography can reliably identify material defects during the production of wooden items. This allows rejects to be caught quickly and eliminated, and faulty goods to be repaired in good time.

People who buy an expensive solid wooden table or wardrobe want to be certain that their new piece of furniture is absolutely faultless. Pianos -- whether upright or grand -- can only produce an opulent tone if their soundboard, bridge and keyboard are made of high-quality materials. And wood that is free of imperfections is also essential in house building and window construction: load-bearing wooden beams need to be of the highest quality, as even the smallest crack can cause them to fail.

Research scientists from the Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut, WKI in Braunschweig are able to pinpoint defects in wood that cannot be seen with the naked eye. Using high-power ultrasound thermography they can detect longitudinal and transverse cracks, gluing errors, delaminations and black knots. To do this they vibrate the wooden item using a sonotrode, or ultrasound agitator, at a frequency of 20 kHz -- in other words, 20,000 times a second. Where there are defects, the different parts of the material rub against each other and produce heat. This heat at the defect's extremities is picked up by a thermal imaging camera connected to a monitor; in the case of hairline cracks, frictional heat can be seen along the length of the crack as well. High-power ultrasound thermography even allows the researchers to probe beneath the surface to uncover dowels that have not been glued and defects hidden under coatings -- something that today's much less reliable testing methods, such as mechanical materials testing or electrical measuring, are simply not able to do.

"We can spot the imperfections in raw timber. That is crucial for rejecting defective wood before time and money have been invested in processing it," says physicist Peter Meinlschmidt at the WKI. Whether the wood in question is oak, walnut or beech is not important, and neither is the condition of the wood ; defects in damp parts show up on the thermal imaging camera too. The depth to which the wood can be analyzed depends on its thermal conductivity, but up to 20 millimeters are possible.

"Our process is especially suited for finding defects in high-quality solid wooden parts and window frame squares and to detect badly glued joints. It's a non-destructive testing method. Applying the ultrasound agitator does leave small pressure marks though -- but these aren't an issue when you're dealing with raw timber," explains Meinlschmidt. The researchers have even managed to use high-energy ultrasound thermography to detect cracks in ceramics and glass. In laboratory tests, they were able to pinpoint defects in ceramic floor tiles and in glass mouthwash bottles. "In ceramics and glass we can spot defects that are up to 30 centimeters away from the sonotrode," says the research scientist. A demonstrator of the ultrasound generator with thermal imaging camera has already been built.


Story Source:

The above story is based on materials provided by Fraunhofer-Gesellschaft. Note: Materials may be edited for content and length.


Cite This Page:

Fraunhofer-Gesellschaft. "Spotting weaknesses in solid wood." ScienceDaily. ScienceDaily, 5 August 2011. <www.sciencedaily.com/releases/2011/08/110804081607.htm>.
Fraunhofer-Gesellschaft. (2011, August 5). Spotting weaknesses in solid wood. ScienceDaily. Retrieved October 23, 2014 from www.sciencedaily.com/releases/2011/08/110804081607.htm
Fraunhofer-Gesellschaft. "Spotting weaknesses in solid wood." ScienceDaily. www.sciencedaily.com/releases/2011/08/110804081607.htm (accessed October 23, 2014).

Share This



More Matter & Energy News

Thursday, October 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Chameleon Camouflage to Give Tanks Cloaking Capabilities

Chameleon Camouflage to Give Tanks Cloaking Capabilities

Reuters - Innovations Video Online (Oct. 22, 2014) — Inspired by the way a chameleon changes its colour to disguise itself; scientists in Poland want to replace traditional camouflage paint with thousands of electrochromic plates that will continuously change colour to blend with its surroundings. The first PL-01 concept tank prototype will be tested within a few years, with scientists predicting that a similar technology could even be woven into the fabric of a soldiers' clothing making them virtually invisible to the naked eye. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Jet Sales Lift Boeing Profit 18 Pct.

Jet Sales Lift Boeing Profit 18 Pct.

Reuters - Business Video Online (Oct. 22, 2014) — Strong jet demand has pushed Boeing to raise its profit forecast for the third time, but analysts were disappointed by its small cash flow. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Internet of Things Aims to Smarten Your Life

Internet of Things Aims to Smarten Your Life

AP (Oct. 22, 2014) — As more and more Bluetooth-enabled devices are reaching consumers, developers are busy connecting them together as part of the Internet of Things. (Oct. 22) Video provided by AP
Powered by NewsLook.com
What Is Magic Leap, And Why Is It Worth $500M?

What Is Magic Leap, And Why Is It Worth $500M?

Newsy (Oct. 22, 2014) — Magic Leap isn't publicizing much more than a description of its product, but it’s been enough for Google and others to invest more than $500M. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins