Evolution of Technology for Materials Processing over the Last 50 Years: The Automotive Example, The

JOM, Feb 2007 by Taub, Alan I, Krajewski, Paul E, Luo, Alan A, Owens, John N

Author's Note: The automotive business is an ideal choice to examine the dramatic impact of improved materials and manufacturing processes on an industry. Automakerstodayareabletocombinehigh-tech materials originally applied in aerospace and other industries with the high-volume manufacture of a mass-marketed consumer product. This paper will detail how many of the changes to vehicles that have resulted from these influences over the past 50 years have been enabled By significant advances in materials and processes.

THE FIRST 50 YEARS

The basic elements of the automobile had matured substantially by the middle of the twentieth century-the first motor car was patented by Karl Benz in 1886 and the basic principle of the automobile manufacturing process, the moving assembly line, was first put into practice in 1913.1

By the 1950s, vehicle engineering and manufacturing processes had developed to the point where annual freshening of body styles was possible even with the requirement of efficiently ramping up new models to hundreds of thousands of u n its per year for each body type.2 In that same timeframe, the gasoline internal combustion engine had also advanced significantly. General Motors (GM), in fact, introduced the first overhead valve, high-compression eight-cylinder (V8) engine in the 1953 Buick Roadmaster and the small-block V8 in a 1955 Chevrolet. That first small block displaced just 4.3 liters and produced up to 195 horsepower, or 45 horsepower per liter. Ninety million engines and lour generations later, the small block today displaces up to 6.0 liters and achieves ~400 horsepower, or roughly 65-70 horse power per liter.3 The substantial improvement in power density is even more impressive when one considers that smog-forming emissions (hydrocarbons and nitrogen oxides) have been reduced by more than 99 percent at the same time.4

The large economies of scale available to the industry made vehicles affordable to growing numbers of people. Henry Ford designed the Model T to be "a motor ear for the great multitude . . . so low in price that no man making a good salary will be unable to own one,"5 and A lf red Sloan stated that "the ideal toward which (GM) is striving is to have "a car for every purse and purpose' and to make every car represent maximum value to the purchaser at its respective price."6 By 1955, the cost to buy a baseline Chevrolet Bel Air ($1,725) represented just 20 weeks of U.S. wages.7 Affordability promoted personal mobility and by the mid-1950s, the North American auto industry was producing almost 10 million units per year (compared to 14.6 million units today).8 The trend has continued-despite dramatically increased vehicle content, it takes only 24 weeks of a U.S. median family income to purchase a vehicle today.9 Global vehicle ownership has grown even more impressively-the industry produced just over 13.5 million units in 1950 compared to almost 66 million units today.10 In 1950, there were less than 60 million vehicles on the planet and only two percent of the world's population were vehicle owners. Today, the global vehicles in use stand at 800 million, which translates to approximately 12 percent of the world's population owning automobiles.11

INDUSTRY CHALLENGES IN PAST 50 YEARS

Beginning in the 1960s, the auto industry has had to deal with a number of significant "externalities" that have driven discontinuous changes in the automobile. These external pressures have included emissions concerns, issues related to energy consumption and availability vehicle safety, and, more recently growing consumer demand for more personalized products. Main of the changes to our vehicles that resulted from these key influences have been enabled by advances in materials and manufacturing processes (Figure 1).

At the start of the 1950s, design and performance were the key differentiators of the product in the marketplace. This worked well for the industry until the mid-1960s, when Ralph Nailer and other consumer advocates began to draw increased attention to automobile safety.12 With the heightened locus on safety, new features like energy-absorbing systems, structures, and materials were introduced into the vehicle to protect occupants in the event of a crash. These changes resulted in more demanding vehicle requirements and increased engineering complexity.

Following close on the heels of the calls for enhanced safety, the Organization of Petroleum Exporting Countries oil crises of 1973 and 1979 drove oil and gasoline prices sharply higher and the industry needed to increase vehicle fuel economy. One important avenue for improving vehicle efficiency, and thus fuel economy, is mass reduction. For a mid-sized family car weighing 1,450 kg, it takes a 45-kg reduction in mass to achieve a 0.6 miles-per-gallon improvement in fuel economy.13

To more easily reduce vehicle weight, the industry moved cars from the body-on-frame (BOF) architecture to the more weight-efficient body-frame-integral (BFI) architecture. With the BFI architecture, all body panels contribute to vehicle stiffness and performance. At the same time, lightweight materials began to he substituted for the low-carbon steel that dominated the vehicle structure. With this new architecture and additional engineering safety requirements, it became more difficult to make major styling changes and, therefore, it began to lake longer to refresh vehicle designs.