FASTLITE: French Program to Cut Vehicle Weight

In the next 5 to 7 years, the French FASTLITE project is attempting to take 200 kg (440 lb) out of vehicle weight. FASTLITE is subsidized by the French government, and involves Renault, PSA Peugeot Citroen, a dozen suppliers, research labs and universities.
A PSA Materials Expert was quoted as saying that carbon fiber is too expensive for mass production even when considering lifetime fuel savings. However, SMC (sheet molding compound) becomes more economical, since the lower lifetime fuel costs can outweigh the additional costs associated with manufacturing. In addition, he says that “We are not sure that the materials needed are existing today … We need modeling tools, automation, numeric tools; and our teams need to learn how to design composite parts.”
The article describes a presentation from the Massachusetts Institute of Technology comparing extra costs of different materials with the possible weight savings. High-strength steel adds €1 to €2 ($1.33 to $1.66) per 2.2 lbs. (1 kg) and saves 5% to 20% of mass, while carbon fiber adds €10 to €16 ($13.30 to $21.25) in manufacturing cost to save 40% to 60% in mass.

http://wardsauto.com/vehicles-amp-technology/french-researchers-driven-cut-vehicle-weight

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Audi A3: Mixed Materials Leads to Lighter Weight

The current model Audi A3 is 80 kg lighter than the prior version, resulting from “relatively thin-walled, form-hardened steels that make up 26% of an A3’s body materials, many aluminum parts including the hood and fenders, plastic for the front passenger airbag housing, and magnesium for the MMI human-machine interface monitor bracket.”
http://www.sae.org/mags/aei/11143

http://www.sae.org/servlets/dlymags/dailymag/articleImage.jsp?imgsrc=/dlymagazineimages/11143_14204_ACT.jpg&alttxt=Audi%20A3%20Materials%202.jpg

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Aluminum from Bauxite and Alumina

Here’s a video showing how aluminum is made:

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Aluminum Can Manufacturing

Here’s a great video on how aluminum cans are made:

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IIHS Small Overlap Frontal Crash Test

New challenges are ahead in material requirements and automotive structural design.

http://www.iihs.org/news/rss/pr081412.html

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Training, Mathematics, and Communicating

I read a summary of a research report out of Carnegie-Mellon University this morning which found that early understanding of fractions and division predicts a student’s future math success (http://www.cmu.edu/homepage/society/2012/summer/math-success.shtml). Similarly, I read an interesting and somewhat humorous article in Forbes about the overuse of hackneyed business cliches (http://tinyurl.com/brtnput). You may be asking how do these seemingly unrelated articles relate.

When was the last time you sat in on a conference or symposium where a presenter flashed a long string of Greek letters on the screen for 5 seconds saying “And here is the equation for blah, blah, blah”? Maybe you really care what “blah, blah, blah” is, and have extensive experience in the field. You still feel inadequate that you didn’t understand the 15 Greek symbols in the 5 seconds you were allotted. After the seventh or eighth 5-second slide of Greek letters you either fell asleep or became really angry at the presenter. I assure you that the problem isn’t you. The problem is the lazy presenter.

How much effort does it take for a knowledgeable instructor to say “The value of A is a function of the values of C, D, R, Q, and Theta. Here is how they relate”? Perhaps your instructor really was just lazy in preparing his or her presentation. Perhaps your instrutor really doesn’t understand the relationship and hopes you won’t notice. In this video by Carnegie Mellon University’s Robert Siegler, he discusses how too many primary education teachers simply teach the rules without explaining why the process works.

I’ve made a commitment to challenge the drive-by equation presenters from now on. Why not join me?

The same problem exists with all the tired old business cliches. I believe that these cliches are frequently coined by lecturers, writers, and administrators who want only to be noticed. Most seem to lack the depth of knowledge to express a problem or its solution articulately. I find it amusing that accountants refer to accounting as the “Language of Business”. The problem, of course is that accounting is an “after the fact” measurement. It doesn’t innovate, design or build product, or sell anything. Real business speaks many languages. It speaks engineering, design, sales, innovation, manufacturing, customer service, and administration.

When we understand the richness and contribution of each “language”, we better understand our companies, products, employees, and business.

– Bill

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North American Deep Draw Research Group (NADDRG)

On May 15, the Spring 2012 Symposium of the North American Deep Drawing Research Group (NADDRG) was held at Oakland University, Auburn Hills, MI, with over 100 attendees from industry and academia coming to discuss the latest theoretical and practical issues in sheet metal forming. In contrast with many related symposia, those of NADDRG often consist of informal, off-the-record, in-progress presentations. At this gathering, topics included Advanced High Strength Steels (AHSS), Experimental Measurements & Finite Element Modeling, Advanced Manufacturing Processes, and Hot/Warm Forming. 4M Partner Danny Schaeffler finished his 4-year term as NADDRG President, and passed the baton to the incoming president, a Technical Fellow from the General Motors Manufacturing Systems Research Lab.

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Bridge the Gap Between Virtual Modelling and your Plant Floor

Manufacturers and designers have much interest in virtual design and modelling for formed sheet metal products. There can be significant advantages, including reduced time to manufacture, lower cost, environmental friendliness, and greater flexibility in experimentation. The problem many encounter, though, is that virtual modelling results can differ quite a bit from the results on the plant floor. There are several actions you can take to “bridge the gap” between virtual results, and real mechanical results.

Probably the best thing you can do is to get your designers and modellers away from their monitors and onto the plant floor. Productive discussion between designers and plant employees can be the greatest “on-the-job” training your virtualization employees can recieve. How much better do you think design, modelling, and experimentation will be if virtual designers understand of such things as:

  • tool and die build and set up,
  • geometry and material effects on die temperatures,
  • real binder force and draw bead impacts on material flow on your plant floor, with your equipment and skill sets, and
  • the impact of design and materials on machine and die wear rates?

Continuing discussions and reliable information are the real contributors to the value of virtual design and modelling on your product quality and profitability.

– Bill

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The Ultimate Material in Automotive Manufacturing

Cheap, strong, manufacturable, light-weight. That’s all the auto industry wants. Of course, there is no single material that meets all of these qualifications, at least not under today’s economics and technologies. The likely candidates – steel, aluminum, magnesium, and composites – each offer some benefits. Consider:

  • ArcelorMittal, the world’s largest steel company, recently described the growing usage of Advanced High Strength Steel (AHSS) in automotive applications as: 6% in 2005; 9% in 2008; 14% (f) in 2014; 32% by 2020 (data provided by ArcelorMittal at the Platts/SBB Steel Markets Europe Conference in May 2012.)
  • AHSS is the cheapest advanced structural material at an average price of $1.70/kg, and is readily available. Carbon Fiber Reinforced Polymers (CFRP) are much more extensively used in aerospace, primarily because a 1 pound reduction is reportedly worth a $100 to $300 premium in this industry. While new aerospace models like Airbus’ A350 and Boeing’s 787 Dreamliner employ over 50% CFRP by weight, on average polymer composites constitute less than 2% of an automobile’s total weight.
  • Based on a broad-based survey in Europe, Ducker predicts 150kg of automotive aluminum applications by 2015. However, to continue growth, it will be necessary to make significant inroads into the smaller cars (A- and B-class), which currently consume 103kg per vehicle. In Europe, these small cars make up 27% of the market, compared with 4% in the USA.
  • The global production capacity of magnesium at the end of 2010 stood at 1,320,000 metric tons. China held 82% of this capacity (1,080,000 MT), Russia holds 6% (80,000 MT), and the United States is the country with the third largest worldwide production capacity of 4% of the global amount, or 52,000 metric tons. (United States Geological Survey)
  • Industry experts estimate that carbon fiber can easily use up to 85-90 kg (200 lbs) per vehicle. For a single series model of 250,000 vehicles, that equates to 22,500 MT (50M lbs) of carbon fiber. That single series model would consume about one-half of today’s worldwide supply of carbon fiber. (Presented by Zoltek at the October 2010 SAMPE Fall Technical Conference)

Obviously, 350 words aren’t enough to hit all the issues, but it’s what we can start with. There will be more to come…

– Danny

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AHSS Applications in Automotive

The American Iron and Steel Institute (AISI) just released a 42 page report titled AHSS 101: Evolving Use of Advanced High-strength Steels for Automotive Applications. It’s a great overview of the different grades of AHSS and their applications.

For a brief introduction, please see our 2-part series published by the Fabricators and Manufacturers Association (FMA) at www.TheFabricator.com. Part I describes the different grades, and Part II highlights some of the processing concerns stampers should consider in their designs and approaches.

Danny

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Hardness Testing: Rockwell / Brinell / Vickers Scales and Applicability to Stamped Sheet Steel Parts

You’ve probably noticed that hardness is sometimes reported on your sheet metal certs (and if you see it, you are likely paying for it, probably a few dollars a ton). If you are using mild steel that’s about 1.5 mm (0.060”) thick, it’ll probably be in the mid to high 70s if it’s measured on the Rockwell B scale. But what does this really mean?

Simply put, hardness is a measure of the resistance to indentation. Of course, different materials have different performance, but the test result also depends on what kind of indenter is used (size/shape/material) and how much force is used to push it into the sheet metal. These testing parameters determine what scale is used to report results.

Rockwell hardness values are determined using a two-step process. First, the indenter (either ball- or cone-shaped) is pushed into the surface until the desired pre-load (also called “minor load”) is reached (10kg for the B and C scales, 3kg for the N and T superficial scales). This small initial penetration seats the indenter and provides a reference depth. An additional “major load” is applied, which results in deeper penetration into the sheet metal surface. The major load is then removed and the minor load is re-applied. The difference between this depth reading and the reference depth is used in the Rockwell hardness calculation, and is “d” in the equation for the Rockwell B scale:
HRB = 130 – ( d / 0.002mm )

This calculation shows that if a Rockwell B value of 80 is measured, there is a 0.10mm difference in depth between the minor and major load, and for HRB65, there is a 0.13mm penetration. Put another way, there is only a 30 µm difference in penetration depth between readings of HRB65 and HRB80. As a point of reference, the thickness of human hair is on the order of 100 µm (0.10mm).

The Brinell hardness test involves applying a specified load using a hardened steel or tungsten carbide spherical indenter of a specified diameter (typically 1mm to 10mm). The Brinell hardness number is calculated by dividing the load applied by the hemispherical surface area of the indentation. Due at least partially to the relatively high loads and to the challenges of measuring a curved surface area, Brinell testing is typically not used for sheet metal.

Like Brinell testing, the Vickers hardness number is calculated by dividing the applied load by the surface area of the indentation. However, a Vickers microhardness test is typically done with significantly less force than a Brinell test, using a diamond indenter having a square cross-section. Built into the Vickers microhardness test machine is a microscope that allows for more precise measurement of the diagonal cross-sectional lengths. By magnifying the surface, it becomes possible to target specific microstructural constituents (like martensite or bainite in Advanced High Strength Steels) or to assess the quality of heat treating or surface hardening operations.

Independent of the hardness scale used, a deeper, wider impression will allow for more accurate and representative readings. However, if the impression is too deep, then the platform that supports the test piece, known as the anvil, will influence the result. According to ASTM Standard E18 for Hardness Testing, to avoid this so-called “anvil effect,” it is necessary to have the indentation depth no more than 10% of the total test piece thickness. If your indenter or hardness test scale is inappropriate, you’ll likely see a shiny spot on the test piece underside where it was pushed into the anvil surface. If you see this, then you are testing the hardness of the anvil, rather than the hardness of your test piece. You’ll need to change your test conditions to produce a smaller, shallower indentation.

A brief example of the relevance of this part of the specification: Using the measurements shown above, you are in violation of the ASTM requirements if you are getting a Rockwell B hardness reading of 80 or less on sheet metal that is less than 1mm thick. Why? HRB80 means an indentation depth of 0.10 mm, and as the indentation depth increases, the hardness decreases. 10 times this indentation depth is 1 mm. Any greater penetration violates the 10x rule, and you are likely going to see the influence of the anvil in your results. The applied load on the Rockwell B scale is 100 kg. To produce a more shallow impression, you should switch scales, potentially to a 30T scale, where the applied load is 30 kg.

Something else to think about … In the first paragraph, I told you that your Rockwell B hardness was about 75 to 78. If I was able to do that without knowing anything about your coil, what does that tell you about the usefulness of hardness testing of sheet products? The bottom line is that hardness measures the resistance to indentation, but is a poor predictor of sheet metal formability.

Selected hardness scales Indenter Applied load
Rockwell – B scale 1/16” diameter ball 100kg
Rockwell – C scale 120° diamond cone with a 0.2mm radius spherical tip 150kg
Rockwell – 15T scale 1/16” diameter ball 15kg
Rockwell – 30T scale 1/16” diameter ball 30kg
Vickers Square-based pyramid diamond indenter with a 136º included angle Typically 10g to 1,000g
Brinell Spherical indenter, with a diameter typically ranging from 1mm to 10mm. Typically 1kg to 3000kg
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