Featured Research

from universities, journals, and other organizations

Manufacturing crack-resistant lightweight components

Date:
September 6, 2012
Source:
Fraunhofer-Gesellschaft
Summary:
Cold cracking in high-strength steel presents major quality assurance challenges for the automotive and machine-building industries, since cracks are difficult to predict -- until now. A new process can determine, as early as the design stage, if critical conditions for such damage can be prevented. This lowers development times and costs.

In this test, the material sample is heated to welding temperature to determine its critical condi- tions for the formation of cold cracking.
Credit: Chair of Joining and Welding Technology at the Brandenburg University of Technology

Cold cracking in high-strength steel presents major quality assurance challenges for the automotive and machine-building industries, since cracks are difficult to predict -- until now. A new process can determine, as early as the design stage, if critical conditions for such damage can be prevented. This lowers development times and costs.

Cars, roof structures and bridges should become increasingly lighter, with the same stability, and thus save energy and materials. New high-strength steel is superbly suited for the needed lightweight design, because it can also withstand extremely heavy stresses. Yet these materials also betray a disadvantage: with increasing strength their susceptibility to cold cracking rises when welded. These miniscule fractures might form as the welded joints cool off -- typically at temperatures below 200C. In a worst case scenario, the welding seams would crack. For this reason, many industrial sectors are reluctant to employ these promising high-strength steel.

Scientists at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg, in conjunction with the Chair of Joining and Welding Technology LFT at Brandenburg University of Technology Cottbus (BTU) developed a new process for making cold cracking more predictable. "We are able to compute the probability of cold cracking as early as the design stage of a component, and immediately run through corrective measures as well," explains Frank Schweizer of the IWM. Because whether such cold cracking occurs, and how quickly, depends on how high the concentration of hydrogen in the steel is, how the residual stress turns out, and how its microstructure is configured. Predicting the probability of cracking has been difficult until now. Manufacturers used to conduct expensive testing, for example by applying an increasingly higher tensile stress to a sample component, and then analyse what stress level would cause cracking. Not only are these tests time-consuming and cost-intensive, the findings cannot be applied to subsequent components on a one-to-one basis -- because the geometry of the component has a decisive influence on crack formation. Even currently available computer simulations failed to deliver the desired predictive accuracy for real components.

Lowering production costs, shortening development phases

The new approach could markedly reduce such costly methods in the future -- and thus lower production costs while shortening development phases. The experts at LFT set up a special test, in order to precisely determine the cracking criterion on samples of highstrength steel. Beside typical influencing factors like hydrogen content, residual stresses and material structures that can be adjusted in at the same time, they also take into account the temperature gradients that emerge in the welding process.

The experts at IWM feed a computer simulation with this criterion in order to analyze the threat of cold cracking in random components and geometries. "This way, we can locate the areas on a welding seam at risk of cold cracking, for each point and at any time in the simulated welding process," explains Frank Schweizer. The researchers can also get a preliminary look at the effects of any countermeasures, and make the necessary adjustments. To do so, they transfert the results back into the simulation, in order to fine-tune them there.

In the future, with the aid of this process, manufacturers of vehicles and machines could be able to define non-critical welding parameters and limiting conditions for their materials in advance -- and thus establish a substantially more efficient and safer production process. This is especially relevant to materials that are difficult to weld, with very narrow processing windows regarding welding parameters or the pre- and post-heating temperatures. Fraunhofer IWM and LFT, in cooperation with Robert Bosch GmbH and ThyssenKrupp Steel Europe AG, are currently testing their new process on laser beam-welded demonstration models made of high-strength steels.


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. "Manufacturing crack-resistant lightweight components." ScienceDaily. ScienceDaily, 6 September 2012. <www.sciencedaily.com/releases/2012/09/120906111900.htm>.
Fraunhofer-Gesellschaft. (2012, September 6). Manufacturing crack-resistant lightweight components. ScienceDaily. Retrieved April 20, 2014 from www.sciencedaily.com/releases/2012/09/120906111900.htm
Fraunhofer-Gesellschaft. "Manufacturing crack-resistant lightweight components." ScienceDaily. www.sciencedaily.com/releases/2012/09/120906111900.htm (accessed April 20, 2014).

Share This



More Matter & Energy News

Sunday, April 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Why Did Nike Fire Most Of Its Nike FuelBand Team?

Why Did Nike Fire Most Of Its Nike FuelBand Team?

Newsy (Apr. 19, 2014) Nike fired most of its Digital Sport hardware team, the group behind Nike's FuelBand device. Could Apple or an overcrowded market be behind layoffs? Video provided by Newsy
Powered by NewsLook.com
Small Reactors Could Be Future of Nuclear Energy

Small Reactors Could Be Future of Nuclear Energy

AP (Apr. 17, 2014) After the Fukushima nuclear disaster, the industry fell under intense scrutiny. Now, small underground nuclear power plants are being considered as the possible future of the nuclear energy. (April 17) Video provided by AP
Powered by NewsLook.com
Horseless Carriage Introduced at NY Auto Show

Horseless Carriage Introduced at NY Auto Show

AP (Apr. 17, 2014) An electric car that proponents hope will replace horse-drawn carriages in New York City has also been revealed at the auto show. (Apr. 17) Video provided by AP
Powered by NewsLook.com
Honda's New ASIMO Robot, More Human-Like Than Ever

Honda's New ASIMO Robot, More Human-Like Than Ever

AFP (Apr. 17, 2014) It walks and runs, even up and down stairs. It can open a bottle and serve a drink, and politely tries to shake hands with a stranger. Meet the latest ASIMO, Honda's humanoid robot. Duration: 00:54 Video provided by AFP
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:
from the past week

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