Notice "lightweight configuration," and supercar masters Ferrari, McLaren, and Porsche presumably beat your hit parade. General Motors, on the off chance that you consider them by any means, definitely survives this rundown. In any case, now that each creator is endeavoring to fulfill future efficiency commitments, GM is developing as a pioneer of the lightweight pack, particularly as far as mass-delivered models that the vast majority of us can really manage.
Charlie Klein, GM's official executive in charge of CO2 methodology, vitality, mass, and optimal design (what else matters?), as of late compressed the advancement America's biggest auto maker has made. Utilizing GM's own figures, seven crisp creation models are said to be lighter by a normal of 350 pounds contrasted and their prompt forerunners. Pressing proof into his case, Klein uncovered the techniques behind GM's effectiveness activity and shared a couple propelled advances under examination for future usage.
Six to eight years back, GM's top building administration inferred that lighter items not just were vital to meet more stringent mileage models, additionally to contend effectively against worldwide rivals in execution. Once that acknowledgment streamed down to the R&D trenches, Klein and his designing group raised lightweighting to the same need as cutting edge powertrain advancements, streamlined refinement, and the optimization of every component and system. Lightweighting isn't the wholesale conversion of steel bodies to aluminum or carbon-fiber construction. Because cost and other variables—such as crash safety, interior space, and noise and vibration—are involved, this engineering responsibility gets complicated fast. So that everyone involved understood the war against weight, some clever GM manager coined a concise battle cry: Every engineer, part, and gram matters!
Fortunately, GM is armed with clever experts and powerful design and development tools. Computer-aided engineering (CAE) is arguably the handiest wrench in the GM toolbox; it facilitates the evaluation of 1001 good ideas before choosing a few for the prototype stage. CAE helps optimize load paths, structural stiffness, crash performance, aerodynamic efficiency, and curb weight. GM's team of 140 simulation engineers invested 19 million CAE computational hours to help shave weight in the Camaro and Malibu. Taking the incumbent German sport sedans seriously, another 50 million computational hours were invested in assuring that the Cadillac CT6 could meet or beat the Audi A6, BMW 5-series, and Mercedes-Benz E-class. Some of this effort is basic attention to details. The Cadillac ATS, for example, is lighter because many panels are liberally punched with holes, and flanges are trimmed and scalloped around spot weld locations to shed unnecessary material. Newer model Malibu is larger and structurally stiffer than its predecessor, but it's also hundreds of pounds lighter because half of its unibody consists of high-strength steel; seven different grades were selected to put the most appropriate steel at every location. This how much Cadillac CT6 is a crazy quilt of aluminum, steel, magnesium, and plastic— over 10 different materials in all. Front longitudinal members that must absorb collision energy are aluminum extrusions. Castings, which save weight and trim the total parts count, are used for major joints such as the front hinge pillar. Sheet aluminum covers the roof, fenders, and doors. Various grades of steel comprise the passenger cell's safety cage. To assemble the CT6's parts into a cohesive unibody, GM uses eight different joining methods: 900 feet of structural adhesive, 30 feet of aluminum arc welds, 7 feet of aluminum laser welds, 2 feet of steel brazing, 1620 steel spot welds, 1465 aluminum spot welds, 740 flow-form screws, and 330 self-piercing rivets.
Audi, Jaguar, and others have manufactured aluminum bodies for years, but GM ventured beyond their methodology to make the CT6 lighter, stiffer, and reasonably affordable. One major stride is avoiding use of rivets for joining panels, which adds weight and cost. Instead, GM perfected spot-welding techniques to unite the various forms of aluminum. This required new electrode tip designs and careful programming of the electrical current and voltage. Nine GM plants applied the lessons learned to begin manufacturing aluminum liftgate, door, and body-structure components.
The following stride is joining aluminum and steel with spot welding. A key issue is that aluminum dissolves at 1200 degrees Fahrenheit while steel softens at 2800 degrees. Likewise, a slight between metallic layer frames between the two metals and the oxide covering the aluminum sheet must be managed. By utilizing reproduction instruments to display the basic material science, GM engineers distinguished the weld parameters that would permit customary approach—spot welding—to be utilized as a part of Cadillac's most up to date vehicle. After approval testing is finished, this protected strategy will be utilized to join two sheets of aluminum to a solitary sheet of steel in the CT6's seat backs. The second not so distant future application is spot welding an aluminum internal hood board to its steel fortification.
Laser welding is another appealing innovation with issue ranges. Customary systems lessen quality with weld scatter and porosity issues. GM's licensed arrangement is utilizing double laser pillars to make a quiet pool of liquid metal at the weld area. The second issue is that the laser's gap plate is harmed by vitality reflected from the weld zone. That concern was resolved by shaping the plate into a V so that energy bounces harmlessly off without damaging the aperture plate. Magnesium is an attractive structural material because it's one-third lighter than aluminum. A few makers are already making inner-door assemblies of this material; Klein's show-and-tell compared a seven-piece steel assembly weighing 20 pounds to single-piece magnesium die-casting weighing half that much. Also, sheet magnesium is attractive for roof panels and other areas of the car. Three years ago, GM began manufacturing Cadillac SLS decklids in China consisting of a magnesium inner layer joined to an aluminum outer layer. Heating the magnesium to 850 degrees F softened it to the extent that it could be formed into a die with a blast of high-pressure air. A few hundred production cars were built to gain experience with this methodology.
Without saying exactly when, GM engineers acknowledge that they have sufficient experience testing carbon-composite wheels to offer them soon as a regular production option. This will save 35 pounds per car in unsprung weight and rotating inertia. Another study area is replacing most of a unibody's floor pan with a molded-fiberglass panel. A demonstration piece revealed a spot-welded sandwich of steel and fiberglass in key areas where seats, reinforcements, and cross members attach. Advantages are reduced parts count, lighter weight, and compatibility with current assembly methods. To save even more weight, substituting carbon fiber for the fiberglass also is feasible.Counting up the additions, GM asserts a net investment funds of 15-million gallons of fuel and 150,000 tons of CO2 for every year for seven new creation models: Buick LaCrosse; Cadillac XT5; Chevrolet's Camaro, Cruze, Malibu, and Volt; and GMC Acadia. This looks good for what's to come. Lessons learned, strategies set up, and innovation being worked on will lift GM's remaining on everybody's appreciation list. Also, don't be amazed if future GM items—match the best Ferrari, McLaren, and Porsche supercars as far as both weight and execution.
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