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Testing sheet metals and stamping dies costs the automotive industry tons of cash, and it's all wrong, wrong, wrong

Sheet metal isn't high-tech stuff, but a lot of work goes into getting it right when it comes to things like the automotive industry. The surface of a stamped piece of metal is an indicator to the amount of stress it can handle and how, when and where it may fail. The standard method of measurement for surface profiling is being called into question for its accuracy after findings from a group of NIST researchers.

Traditionally, the measurements in question were done with an instrument called a profilometer. The simple device, similar to a phonograph needle, is drawn in a line over the surface of a material to measure the often microscopic terrain. After repeated tests, the data from the instrument is averaged to make a "roughness" measurement.

Unfortunately, as the NIST research shows, this method may be terribly inaccurate due to uncertainties and statistical errors when the measurements are extrapolated into a three-dimensional surface.

Rather than using a two-dimensional technique like the profilometer, Mark Stoudt, Joseph Hubbard and Stanley Janet of NIST use an instrument called a scanning laser confocal microscope to make a point-by-point image of a surface. The measured area from one image is roughly 1000 x 800 micrometers long and wide by 20 micrometers deep. The data from each point is then analyzed simultaneously using mathematical techniques to give a more accurate measurement than could be obtained by two-dimensional methods.

One discovery already made on aluminum alloy used in the study is that the generally accepted linear relationship between surface roughness and material deformation for the alloy is wrong. Data from the research suggests a more complicated relationship was hidden by the uncertainties of linear profilometers.

This and the rest of their findings have been published in a paper titled "Using Matrix Methods to Characterize Evolution of Deformation Induced Surface Roughness in Aluminum Sheet" in the journal Materials Science and Technology.

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Like the title
By Etsp on 1/19/2008 2:50:25 PM , Rating: 2
Those scientific types can really come up with a catchy title to their articles...
quote:
Using Matrix Methods to Characterize Evolution of Deformation Induced Surface Roughness in Aluminum Sheet
Man that's both catchy, AND intriguing.




RE: Like the title
By fk49 on 1/19/2008 5:02:37 PM , Rating: 2
It's amazing how they can say so much...yet say so little.


RE: Like the title
By Master Kenobi (blog) on 1/20/2008 12:37:26 AM , Rating: 2
Saying so much yet saying so little. Makes me wonder why Scientists never make it as Politicians, they seem to be on the same track in this regard.


RE: Like the title
By elpresidente2075 on 1/20/2008 11:07:32 AM , Rating: 5
It's because scientists generally want to help the world.


RE: Like the title
By inighthawki on 1/21/2008 12:03:59 AM , Rating: 2
rofl, sadly it's true, yet personally i think it's these people that NEED to be politicians. These are the people that understand information thrown at them. Out idiot lawyer politicians only know how to sue people and sign papers when it comes down to it. How can we solve big issues like global warming if our politicians are dumb enough to believe it even exists?


RE: Like the title
By Ringold on 1/21/2008 2:55:54 AM , Rating: 2
I've met several politicians, I think that general theory of them is wrong. I think they're generally smart people, have to have some degree of intelligence in order to have cut a sufficient number of throats to even get elected.

Take for example, the current "stimulus package" deal. Democrats and Republican's, united for the first time in almost a decade with the goal of giving away money that isn't theirs to the masses; much like a Roman general returning to Rome with gifts for the people so that they would honor him with a triumph; this time, they just want votes in November. I bet you, though, that both parties are aware that it's ultimate impact will be virtually nil, that no one knows how to "fix" a business cycle, and that, besides, the root of the problem is in the financial markets anyway. That doesn't stop Republican's from trying to get in business depreciation benefits in, nor Democrats from trying to sneak in extra welfare money (though Bernanke did say the business benefits have more bang-for-the-buck, dont tell the left that, they dont care -- it wont get them elected!) Similar story in Europe; politicians know how to fix Europe's economic woes (Reaganomics, Ireland-style), just, as they often say, not how to get re-elected after they do it. Both of those being economic issues, I partly blame government educations that barely teach one how to balance a check book, much less look at marcoeconomic issues, but still.

Thats what it comes back to, though, the people and elections.Therefore.. I think the electorate are the idiots, not politicians. I don't care how miserable the weather was in Michigan, anybody note how low that turnout was for the primary? The politicians are slaves to the structure that we, the people, at least the fraction of us that vote, haphazardly create for them.

That said, they're not experts in many particular fields, but then again what does a scientist working at a biotech firm know about tax policy or defense anyway. Two of the worst presidents in United States history happened to be engineers; Hoover and Carter.


RE: Like the title
By arazok on 1/21/2008 8:47:52 AM , Rating: 2
I've seen some great politicians lose elections because they lacked charisma. It's unfortunate, but many people vote for leaders on gut feelings and baby kissing, not issues.

I think the biggest strength of Democracy is it's greatest weakness - everyone gets to vote. If we could find a very to identify the idiots and take away their votes, you would see politics change dramatically for the better. Politicians would stop pandering to the morons of society and talk about real issues. At a minimum, political ad's on TV would at least disappear.


A little exagerated...
By Keeir on 1/20/2008 1:17:49 AM , Rating: 2
"Sheet metal isn't high-tech stuff, but a lot of work goes into getting it right when it comes to things like the automotive industry. The surface of a stamped piece of metal is an indicator to the amount of stress it can handle and how, when and where it may fail. The standard method of measurement for surface profiling is being called into question for its accuracy after findings from a group of NIST researchers."

I'm going to go with the primary cause in the automotive industry for concern with Sheet Metal is more fitting and corrosion inhibition (such things as paint adherences etc) rather than Ultimate Strength or Fatigue Strength concerns that might be seen with structural members of airplanes (F-15 Longeron) or Cars.

Unless this technique is faster or cheaper, won't really be implemented widely.




RE: A little exagerated...
By roadrun777 on 1/20/2008 2:20:49 AM , Rating: 2
If its anything like laser tomography, it should be relatively fast. The technology to read laser feedback has progressed to the point that it can go as fast as you can move the laser. I imagine, that using an instrument to swipe across the metal and measuring variance differentiation, is extremely slow. When you are measuring on a atomic level like that, any small noise or vibration can throw all the measurements off. So, take a process with lasers, that can be speed up 100 times, and the accuracy increased 100 times or more, and you have something worth implementing.


RE: A little exagerated...
By ChronoReverse on 1/21/2008 3:24:21 PM , Rating: 2
Considering the things we can do with lasers these days, I was a little surprised that they weren't already used for this. Are they really using a mechanical measuring method on a single line and extrapolating that for an entire sheet?


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