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Alcoa and the Aluminum Auto
This article tells the story of the 'decade of inspired cooperation' between Audi and Alcoa that preceded the introduction of the revolutionary aluminum-bodied Audi A8 in 1994. Written by David Schlendorf of Alcoa and reprinted with permission from Ingénieurs de L'Automobile, September 1998.
The age of aluminum is just beginning. No one had ever seen metallic aluminum until 190 years ago. No one could make it in quantity until Alcoa invented the electrolytic reduction process. Today, aluminum is the basic structural material for aerospace applications. Commercial aviation and the extraordinary mobility it provides us could not exist without it. For the same reasons – strength and rigidity in lightweight, high performance structures – aluminum is rapidly becoming the chosen material for the body structures of high performance sports cars and luxury touring sedans.
Over the next 20 years, a trend will gather momentum as aluminum will progressively displace steel in the body structures of a growing variety of vehicles. Because the weight of aluminum is about 1/3 of an equivalent volume of steel (a specific gravity of 2.70 versus steel’s 7.85), automotive engineers can use it to achieve dramatic weight reductions in the single heaviest system in the car. To many this will seem a development of the new millennium. In reality, this dramatic change in the way car companies think about the body structure and its importance to the car began in the early 1980s.
That’s when Alcoa and Audi decided to merge their expertise and resources to develop an aluminum body structure that would be superior in every way to the conventional sheet stamped steel body. Audi had just completed the development of a car with very favorable aerodynamics that would have a sustained impact on the design of all cars to follow.
Dr. Ferdinand Piech, who was then responsible for R&D at Audi, was thinking further ahead, to an even more ambitious goal: He could see that the upward weight spiral in automobiles was on a collision course with the environmental need to reduce fuel consumption and emissions. He concluded that the removal of a truly meaningful amount of weight from the car – say, 200 kilograms – would be the next technological breakthrough in the automotive industry. To accomplish this, Dr. Piech knew that he would require the technology and commitment of a major partner in the aluminum industry.
Coincidentally, Alcoa had concluded that relying on component-by-component conversions from steel to aluminum was not a satisfactory approach to the largest metal consuming market in the world. This piecemeal progress would not gain the market growth we were looking for – nor would it enable car makers to realize aluminum’s full potential for improving automotive design and performance. To achieve what we felt was possible with the automotive industry would require no less than the production of fully aluminum structured cars.
CRITICAL MASS
From the perspective of the car manufacturer, it is necessary to remove at least 50 kilograms of mass before it is possible to downsize or lightweight other components such as the engine, transmission, brakes, bumpers, etc. However, any such downsizing must be accomplished without sacrifice to the performance of the car. As a market driven industry, automobile manufacturers are continually faced with the dilemma of meeting the performance expectations of their customers, while meeting increasingly stringent environmental and safety standards.
What we both foresaw was that the use of an aluminum body would provide far in excess of the critical 50 kilograms in weight reduction and would be the breakthrough needed to stop the weight spiral in its tracks. To get there, our engineers were faced with numerous technical issues. For example, a car body requires a combination of static strength and fatigue resistance. In addition it has to be extremely stiff in order to enhance vehicle responsiveness and provide pleasurable driving experience.
THE SAFETY ISSUE
The car body must also protect the occupants in the event of a collision. It does so by absorbing energy via the deformation process as the body itself folds and collapses in the milliseconds that it takes for a collision to be completed. The more energy absorbed by the body of the car, the less energy that must be dealt with by airbags, seat belts and the occupants’ bodies.
Thus a main thrust of the engineering project that Alcoa and Audi undertook focused on the issue of crashworthiness and occupant protection.
Early on, we elected not to be slaves to the manner in which the steel body had been successfully designed and produced for decades. Aluminum is a metal having substantially different physical and mechanical characteristics and, importantly, is routinely available in a wide variety of product forms.
Aluminum has also been widely and effectively characterized. Its engineering properties are well known and highly predictable. These considerations led us to the concept of an unconventional spaceframe body structure comprised of sheet, extruded and cast components which could be optimized to deliver the desired performance in all possible loading conditions.
It soon became clear that in addition to its inherent weight savings, the aluminum spaceframe would provide formidable advantages in performance ride, handling, safety and manufacturing efficiencies. For example:
Fewer parts. The component count was reduced by as much as 50%
Tooling economies. For the spaceframe’s extruded and cast components, tooling costs are a fraction of those required for sheet stampings.
Improved joints. Any number of joining processes could be employed – most of which provided superior joint efficiency compared with the spot welding that predominates in steel bodies
Versatility. The use of castings permitted a multiplicity of functions to be provided by a single component.
Stiffness and Safety. The spaceframe protects drivers and passengers in a safety cell of outstanding strength and stiffness. Its structural members are specifically designed to absorb energy better in relation to their weight than steel.
WHAT COUNTS: RESULTS
In its final form, the spaceframe we jointly developed employs 40 new patents, several new aluminum alloys and a host of entirely new design and production techniques. After a decade of inspired cooperation, this collaborative breakthrough gave Audi the ability to introduce the remarkable A8 in 1994 and thus enter the top end of the market for luxury touring sedans. Their success in this segment has propelled Audi’s growing stature in the marketplace. Thanks largely to all-aluminum spaceframe construction, the various A8 models averaged 430 kilograms lighter than the typical European luxury car of that year. Imagine the performance you can experience when you have a half tonne less weight to move around.
The results do not stop there. Based upon the U.S./EPA city-highway cycle, trimming 430 kilograms from the weight of a full-size car reduces fuel consumption by 1.9 liters/100 kilometers and saves about 3,140 liters of fuel worth about DM 4,700 over 160,000 kilometer lifetime. Burning less fuel produces lower emissions. Reducing life time fuel consumption by 3,140 liters eliminates 6,800 kilograms of carbon dioxide and reduces emissions of nitrogen compounds, sulfuric acid and particulates.
AN ACCELERATING TREND
These are among the reasons the aluminum-structured car will progressively displace the steel car over the next 20 years regardless of what you may read or hear to the contrary.
Audi executives are on record as believing that within this timeframe all Audis will utilize an aluminum body structure. Other car manufacturers have programs in place that will lead them to do the same - certainly in the mid and upper level luxury touring sedan segments. That high performance sports cars will turn to aluminum bodies seems a foregone conclusion. To our knowledge, there is not a single major car manufacturer who is not exploring the use of aluminum body structures or working on aluminum car intended for series production. Today there are 7 aluminum cars on the road and a number of others are well on their way. Some like the Audi A 1-2, are being developed by the most highly credible and exciting car companies in the world. Taken together, the benefits of the aluminum body structure are so manifest that aluminum cars will prevail over a broad range of prices and volume. Based simply upon the programs we are currently involved in or are aware of, that time has already arrived for Luxury Touring Sedans, High Performance/Sports Cars, and zero emissions vehicles. This is an emerging trend that offers great benefits not only to the automotive and aluminum industries but also to society as a whole – in terms of safety, energy conservation and air quality.
And the turning point came with a shared idea and the strategic commitment of two very different companies.
PRODUCTION REALITY
Another tangible outcome of the development of the aluminum spaceframe has been the establishment of Alcoa Automotive Structures and the commissioning of our plant in Soest, Germany. This was the first plant of its kind worldwide dedicated to the production of components and assemblies for aluminum primary and secondary body structures.
The plant was originally built to produce the components for the body structure for the A8 and it continues to do so at an ever-increasing rate. Each car-set includes 47 extruded components, 50 cast components, and 15 sub-assemblies comprised of some of these components.
The castings are produced using the Alcoa Vacuum Die Casting process. The cast nodes utilized in the spaceframe body structure are designed to meet extremely stringent performance requirements in terms of static and fatigue strength as well as a remarkable degree of toughness. It is this toughness or ability to remain intact during deformation that contributes largely to the crash-worthiness and occupant protection embodied in the spaceframe structures with which Alcoa has been associated.
The production path for the extruded components includes component marking, two computer controlled bending machines, and high speed milling operations. All components, including both cast and extruded, pass through a completely automated heat treat, age and part washing/surface preparation system that brings all components to a uniform T6 temper, ready for subsequent welding operations.
Today the Soest plant also produces the front end energy management structure of the new A Class for Daimler Benz. This assembly, comprised of 13 separate components, is probably the highest volume aluminum welded assembly of this sophistication produced anywhere in the world. Manufacture of this assembly has extended the core competencies of Alcoa Automotive Structures, which are based upon the design and engineering and manufacture of complex assemblies for High Performance Body Structures.
Our plant in Soest of course has a full complement of automated measurement capabilities demanded by the dimensional precision required for today’s automobiles. In addition, we have installed a 3500 tonne hydroforming press. This apparatus is currently utilized for both production operations and the development of dramatic new components which we believe will bring remarkable functionality to spaceframe body structures in the future.
Currently we are in the process of launching production of three other programs associated with spectacular cars, all of which will take advantage of the performance benefits of light-weight, high integrity aluminum spaceframe technology.
In addition to our plant in Germany, Alcoa Automotive Structures has initiated production operations at yet another European location dedicated to the manufacture of complete aluminum spaceframe body structures. In North America we operate a third body structures plant in Northwood, Ohio. There we produce components and assemblies for five cars, these include the body frame for the Plymouth Prowler, the windshield surround for the Corvette, a very high volume cross-member for the Chrysler Intrepid-Concorde, that is a robotically welded assembly of three separate components, and bumper beams for the Buick Riviera and Oldsmobile Aurora.
Alcoa Automotive Structures is the leader in the developing market for aluminum spaceframe body structures. Our focus is the development and manufacture of primary and secondary body structures for cars whose performance expectations demand nothing short of the benefits the aluminum spaceframe provides.
David. W. Schlendorf
David Schlendorf is a business unit president at Alcoa.
Alcoa's German Casting Center & Extrusion Finishing Center
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The Audi Space Frame, the heart of aluminum-intensive vehicle designs like the A8 and S8, was developed in partnership with Alcoa.
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