Supercar probes material
Steel, aluminum, and composites vie for bragging
What will it take to design a vehicle that averages 80 mpg? With little
doubt, materials will play a key role. Which material will win out? It depends
upon who you talk to, but advocates can make strong cases for steel, aluminum,
Long a staple of the automotive industry, major metal producers have several in-novative material programs underway they hope will be included in future car designs. Nowhere will these concepts get a better test than in the so-called Supercar project.
The Partnership for a New Generation of Vehicles (PNGV), a government/auto industry consortium selected to develop the Supercar, has already embraced sheet-steel producers who will participate in the auto-body development. In addition, the Bar Applications Group of the American Iron and Steel Institute has met with the PNGV team dealing with power trains and suspension systems. Ideas being tossed around include the use of bar steels to save cost and reduce weight. Proposals currently focus on applications for micro-alloy and new spring steels.
One process that is sure to get a close look by the Supercar team is the UltraLight Steel AutoBody (ULSAB) project, a worldwide consortium of 32 steel companies sponsored by the Auto/Steel Partnership. Already, ULSAB has proved that it is possible to reduce the weight of the average steel car by 25%.
Design guidepost? General Motors' EV1 electric vehicle could serve as a guide for the use of aluminum in the Supercar. Alcan Rolled Products Co., Farmington Hills, MI, convinced GM to employ an Aluminum Vehicle Technology (AVT) system in the production-model electric vehicle. AVT creates the weld-bonded aluminum body structure, to which all the mechanical components and the composite exterior panels are attached. Extrusions, castings, and other sheet fabrications are integrated into this structure to simplify assembly and reduce production costs.
The sheet-based body frame integrates functions of the car body and chassis in the same way as the unibody of a body-frame integral design. About half the parts are stamped, while the balance are folded sheet, castings, and extrusions. "This translates into significant savings in tooling costs," explains David Rinehart, automotive program manager at Alcan.
Design synergy. In addition, Ford has created the Synergy 2010 concept car, which parallels many of the Supecar's design criteria. "A key purpose is to look at how some intriguing, extremely fuel-efficient technologies could be packaged in a well-styled car of the future," says Bob Mull, director of Ford's New Generation Vehicle programs.
At 2,200 lbs, the Synergy 2010 weighs about 1,100 lbs less than today's mid-sized sedan. Use of all-aluminum unibody construction was the primary contributor to weight-savings, cutting about 400 lbs from the vehicle. Because of this weight reduction, other components sized according to vehicle mass--such as the engine, flywheel system, radiator, and brakes--also could be reduced, saving another 300 lbs.
Persuasive Prowler. Also making a case for use of aluminum in the Supercar is the Plymouth Prowler. The sporty two-seater introduced by Chrysler early this year incorporates 900 lbs of aluminum, including an aluminum chassis. This is only 100 lbs less than the Honda Acura NSX, said to be the most aluminum-intensive car now on the market, which includes about 1,000 lbs of the lightweight metal.
Then there's the Audi A8 luxury car, set to debut in the U.S this fall. The A8 features a new "spaceframe" de-sign, including ex-truded and cast-aluminum components, that requires one-third fewer parts than traditional unibody construction.
"With the Audi A8, we have proven that we can build safe, lightweight aluminium cars," says Pete Bridenbaugh, Alcoa executive vice president, automotive, whose company helped develop the concept. "Although it is one of the safest cars ever made," he adds, "the barrier we have left to conquer is the cost."
Case for composites. However, according to one Supercar participant, polymer composites--any kind of plastic reinforced by glass, textile, or other material--also offer a number of advantages: strength, corrosion resistance, ease of moldability, light weight, and design flexibility.
"Composites have the greatest potential to meet or even exceed the weight-cutting goals for PNGV," observes John Fillion, Chrysler's Materials Tech Team member. "Carbon-fiber composites could save up to 65% and glass-fiber composites about one-quarter of the body structure weight."
To make composites practical, however, high-volume, cost-effective production techniques must become the primary focus for automotive and material engineers. The drawback: lack of data on the durability of polymer composites in an automotive environment. Also, manufacturing and material costs need to be reduced and economical recycling methods developed.
Recently, researchers have turned to Structural Reaction Injection Molding (SRIM) methods to produce large, complex, composite structures. One experimental component under investigation is a pickup-truck box and tailgate. Advanced assembly and joining technologies also are being developed as part of this project. Such technology for structural composite parts will be tested later this year.
Super Supercar. Even before the Supercar's design is finalized, another company hopes to introduce a vechicle that gets up to 90 mpg. Xcorp, Malibu, CA, designed its energy-efficient vehicle using technology spun off from NASA and the Department of Energy. Assembly won't require spot welding, drilling, or riveting. Few finishing operations will be needed. The vehicle also won't have to be painted, thanks to color molded into the composite body. And the vehicle will incorporate ma-jor components de-signed for easy service or replacement.
For the project, Xcorp developed a new class of materials it dubs environmental composites or ECs. The company has applied for more than 50 patents covering the composition of the material, the fastening system, molding systems, production, and a recycling system for manufacturing the ECs. Like current composite technology, ECs are strong, lightweight, non-corrosive, nonconducting, and tend to dampen vibration. They also stand up well to abrasion and wear. In addition, the materials are said to be superior to aluminum in applications where the structure requires a controlled deformation response during catastrophic loads.
ECs also differ from current composites by utilizing a low-energy, low-emissions, "clean" manufacturing system. They can even be formulated from agricultural waste and use recycled materials. Better yet, ECs cost about the same as aluminum to make, according to Xcorp CEO Chris Catlin. He attributes this to EC's low-pressure, low-friction, hybrid molding system; minimal tooling costs; and low labor costs. The materials can be recycled a number of times with a minimal loss of strength.
The initial production-model Xcorp Supercar will be a rear-wheel-drive/rear-engine design. Xcorp plans to offer five models--roadster, sub-compact coupe, sports utility vehicle, and military vehicle. Each will have two drivetrain packages--a modified 45-hp and 80-hp Orbital two-stroke, three-cylinder engine with a CVT or four-speed electronic transmission.
No matter which Supercar design wins the gas-miser war, engineers and automakers should benefit from the materials research devoted to the project. More than likely, some of these advanced materials will show up on future production cars--whether they average 80 mpg or not.
--Gary Chamberlain, Senior Editor
Mold-flow analysis speeds dashboard production
Meru, France--Dashboards roll off the Citroën Saxo production line at the rate of 800 per hour, thanks in part to the fact that they no longer have to be painted after leaving the mold. Other French car makers will soon follow suit.
"We undertook a research program here for two years to optimize the injection of the plastic," relates Sabine Eybert Berard, a plastic engineer at Sommer Allibert Industrie, a major French plastics manufacturer. Seeking to eliminate the need to paint molded parts, Berard based the program on Matra Datavision's Strimflow software for simulating plastic flow. This enabled engineers to predict the quality and appearance of finished plastic parts, as well their mechanical and dimensional properties--all of which depend on the way the plastic is injected into the mold.
The first requirement involved meeting development times, which are continuously becoming shorter. At present, they stand at about four years, but are expected to be cut to three in the near future. All stages of production, therefore, have to be brought forward, particularly the plastic-molding process.
In addition, it was deemed essential to produce an unpainted part of good appearance, something not previously possible with instrument panels. If an unpainted part is scratched, it has to be scrapped, whereas a painted part can always be repainted. The production process had to take this into account, to minimize the risk of scratching during assembly.
The choice of which press to employ for the instrument panel project was determined by the rheological simulation. "Initially, we envisaged using a 1,300-metric-ton press," says Berard. "But the simulation showed that this was too close to the limit, which led to the eventual choice of a more powerful 1,600-ton press."
During the molding of the Saxo dashboard, the molten plastic flowed around openings and left a visible line when the two flows recombined. This can produce blemishes in the surface and create unacceptable long, shiny lines. To overcome this, the mold was redesigned to direct the flow of plastic so that the seal line would remain hidden below the windshield.
Creating such a line involved on-screen simulation of the plastic's flow through the mold, constantly tracking the resin's precise location. The intensity of the coalescence of the flows is deduced and analyzed as they combine. The analysis also calculates the plastic's temperature at each point in the mold.
With this rheological analysis, it becomes possible to predict the appearance of the part, determine the most favorable flow configurations, and work out the modifications needed to move the join line to a non-visible position. In addition, the analysis enables the diameter of the injection nozzles to be calculated so that the plastic flows quickest at the right spot.
"Using rheological simulation, it is possible to make changes sufficiently early, well before production of the prototype mold," Berard says. "This would be impossible without the help of software. The end result is a better quality plastic part that helps cut production costs and the time it takes to produce a new vehicle."
The resulting design introduces molten plastic into the mold at just three injection points, a major innovation, as traditional methods use a minimum of six injection points. "We would never had dared to attempt that previously," Berard reports.
Parametric software optimizes wrist implant
Beaverton, OR--Using a new PC-based parametric CAD system, engineers at Acumed solved a tough design problem by iterating through 20 variations of a medical implant in half an hour. The program, T-FLEX, developed by Top Systems in Moscow, Russia, allowed them to alter part dimensions by simply typing new values into a linked variable list.
Implants must be designed to closely mimic the human joints they replace. Yet, because each patient's structure is unique, producing one size to fit everybody is impossible. Instead, implants are produced in a limited range of sizes, says Gene Conrad, product development engineer at Acumed.
Typically, engineers work with foam sawbones and prototypes in an effort to establish dimensions for a new implant design, Conrad explains. The process is tedious, expensive, and time consuming. Traditional CAD tools offer little help, because resizing a model involves considerable manual redrawing.
Using T-FLEX, Acumed engineers began by sketching design concepts of the Polarus wrist fixator implant and assigning variables--defined as either independent or dependent--to different physical features. Independent variables were listed in a spreadsheet. Dependent variables were defined in terms of the independent ones, and they adjusted themselves automatically when a related variable was changed. By simply typing dimensions into the spreadsheet and printing a copy of the updated drawing on transparent Mylar, engineers visually checked the fit of potential designs against X-rays of actual bones.
Conrad claims that iterating the wrist implant design through 20 concepts with conventional CAD would have taken 30 hours. With T-FLEX, it took just 30 minutes.
T-FLEX is distributed by Western Technical Products (Eugene, OR). Version 5.0 contains complex 2-D and 3-D modeling and parametric capabilities, runs on most Intel-based PCs, and includes AutoCAD compatibility.
Injection-molding tool made by RP
Cranston, RI--American Industrial Casting Inc. (AIC) is using a Sanders Prototype MM-6B Model-MakerTM to make patterns and injection-molding tools with tight dimensional accuracies and surface finishes. The machine employs plotter/miller/inject printing technology to produce intricate prototypes of a thermoplastic material that functions as the wax pattern.
The MM-6B uses a dual printhead to deposit a sequence of thin layers that combine the thermoplastic build material and a wax support material. This supports pattern overhangs and cavities during the construction process. Subsequently, immersion in a solvent bath dissolves the wax support material, leaving the pattern ready for the investment-casting process. No manual post-processing steps are required.
Plotter technology used in the MM-6B maintains dimensional tolerances within 0.001 inch in the x-y plane. A horizontal milling cutter technique maintains consistent slice layer thickness from 0.0005 to 0.005 inch. Cast parts made from patterns (positives) have dimensional resolution of 0.002 inch and surfaces finishes of 80 to 100 µinches, RMS.
In applications that require rapid prototyping of larger parts, AIC has used elastomeric molds made by quick processes. To do so, the company makes an RP pattern on the MM-6B system and an investment-cast BeCu master. Temporary molds of RTV, rubber, or epoxy are made from the master. Though fairly successful, the process has limits reflected in time, cost and mold accuracy.
To deal with these problems, TIC developed a single-step, in-house RP process to make patterns for rapid-prototyped injection-molding tool components. Virtual Concepts Design Inc. of North Attleboro, MA, was engaged to design the tool components starting from a file for the final part. Virtual Concepts and AIC agreed upon parting lines and tool components were drawn using 3D CAD. To conclude the tool component design, a separate file was generated for each component of the injection molding tool.
Engineers combined these files into a single file, and constructed patterns for the tool components on the MM-6B in one overnight build. Subsequently, using a standard solid-mold processing technique, AIC investment-cast the patterns in BeCu. Later processing of the cast components included knockout, grind, finish, inspection, and solution heat treatment. On the seventh day of the project, AIC fitted up the final components and used them to injection-mold several wax patterns.
Those patterns were cast in alloy A356 on the eighth day, then solution-heat-treated to the T6 condition. The final investment-cast components conformed to print requirements. Metallurgist and Research Manager Thomas R. Richards of AIC believes this approach could be used for the rapid prototyp-ing of injection molds for rubber or plastic components.
Software takes on design for manufacture
Cincinnati, OH--Evaluating production results before layout or tooling design doesn't require a crystal ball. Cincinnati Milacron's Acraplace software can give accurate producibility and design-for-manufacture checks from CAD tooling and part data. The software translates part data into seven-axis commands enabling accurate modeling of automated fiber placement.
The Viper Fiber Placement System (FPS) was created to automate production of large, highly contoured parts such as spars, fan blades, inlet ducts, and fuselage sections for the aerospace industry. Acraplace software generates programs to precisely control seven servo-driven machine axes through the Acromatic 975F CNC. It manipulates the 24-tow fiber-placement head over contoured, concave, and convex surfaces.
"Given the huge complexities in part geometries and machine positioning, we knew that programming ease was critical to Viper performance," says Jay Hissett, supervisor of Cincinnati Milacron's Software Products development group. The Viper design and Acraplace software combination allows each tow of fiber to be independently clamped, cut, or restarted at any time.
The initial production release interfaces with CATIA. Future CAD interfaces will include SDRC I-DEAS and the IGES file format. A process manager uses data imported through the translator to the path generator, and develops composite layout paths. Path data is evaluated for producibility with the fiber-placement process. A post-processor module creates NC program files for the machine and mandrel motion for fiber-placing the part. Additional analyses verify that the part is producible with a particular machine/head configuration.
The simulator module allows engineers to view post-processor output at the programmer's station. The programmer can view an animated simulation of the program before the program is sent to the Viper FPS. Interferences, difficult to see in simulation, are automatically detected and corrected.
Automatic surface update accounts for composite material thickness and cycle-time estimates for fiber-placing the part. A link from Acraplace to various FEA packages lets the designer determine if the part meets specifications before actual fabrication begins.
--John Lewis, Northeast Technical Editor
'O2' takes over for Indy on the desktop
Mountain View, CA--Silicon Graphics Inc. has unveiled its next-generation machine to replace the popular entry-level Indy: O2, featuring texture mapping and 3-D accelerated graphics at prices rivaling those of a fully load-ed PC.
"No one is do-ing texture mapping in a $6,000 system," says Greg Weiss, a re-search analyst with D.H. Brown, Port Chester, NY. "For a $6,000 solid modeler, it has very strong price-performance, graphics-wise."
The O2 features a "unified memory architecture," integrating graphics, image processing, video, and compression within the system. This eliminates the need for plug-in cards and a tangle of ribbon cables, company officials say.
The system is targeted at technical users who want interactive 3-D graphics. An auto designer, for example, could check a computer model to see how a car might look in a real-world environ-ment. And consumer-product engi-neers could use such realistic models to see if surface reflections indicate unacceptable "seams" requiring changes to a mold plan.
SGI engineers developed the system around a MIPS R10000 180-MHz processor. The workstation features four custom ASICs: for rendering, display, image and compression, and I/O. Officials say the rendering chip can provide four times the graphic performance that the central processor can dish out. That means as new, faster central processors come out, O2's graphics rendering should scale up accordingly.
Along with its new memory architecture, engineers developed a radical new look for the system, which one analyst called almost toaster-like, compar-ed to competitive designs dubbed "pizza boxes."
A $10,000 O2 (prices range up to $14,000, depending on configuration) will deliver the graphics performance of a system that used to cost $26,000, according to SGI. Officials estimate the O2 boasts 10 times the shaded-triangle performance of the older Indy.
Weiss says that even if O2 doesn't offer the highest raw price/performance in its class, it is the breadth of graphics capabilities that makes the machine appealing. "For the low-end desktop, you're getting a lot of stuff thrown in for the price," he says. If some of the options--texture mapping, video, imaging--would be peripherally useful to an engineer, Weiss says, the O2 is a system worth considering.
Scientists produce better superconducting wire
Argonne, IL--Researchers at Argonne National Laboratory and the University of Pittsburgh have developed a manufacturing technique called "silver wire in tube" that produces wires with critical currents exceeding 100,000 amperes/sq-cm. According to scientists at Argonne, this critical current is the breakthrough value needed for superconducting wire to find a role in practical applications.
"Powder-in-tube" methods now used for making wire from high-temperature superconductors involve sealing superconducting powder in a silver tube, then rolling and drawing the tube into a wire. Result: a silver-clad ribbon of high-temperature superconducting material.
Research done by Argonne and the University of Pittsburgh demonstrated that current in powder-in-tube wires flowed through a thin interface, namely the layer of superconductor closest to the wire's silver casing. "The interface has just the right grain structure and alignment," says Roger Poeppel, director of Argonne's Energy Technology Division. "Since the remaining 90% of the superconductor carries no current worth mentioning, we decided to see if we could get rid of it."
Using a University of Pittsburgh design, Argonne scientists inserted a silver wire into a silver tube, and filled the annulus between the wire and tube with superconducting powder. Produced by the University of Pittsburgh, the BSCCO-223 powder is made from bismuth, lead, strontium, calcium, copper, and oxygen. When cooled to 110K, it becomes a superconductor.
Rolling and drawing the wire placed virtually all the BSCCO powder along the silver-superconductor interface. "We get a layer of superconductor 1 to 2 µm thick," says Poeppel. In tests done at Argonne, that layer consistently provides current densities of 100,000 amperes/sq-cm. By comparison, the best powder-in-tube wire could consistently carry 20,000 to 30,000 amperes/sq-cm, according to Argonne.
Argonne and the University of Pittsburgh are now working with Intermagnetics General Corp., Latham, NY, to make and test longer wires. "The inventors at Argonne and the University of Pittsburgh see no barrier to making long lengths," says James Daley, manager of the Department of Energy's Superconductivity Technology Programs. Reliable superconducting wire could be used in electric motors, generators, and transmission cables.
HP's Exemplar servers show Convex pedigree
Chelmsford, MA--What do you call a computer with 46 GFLOPS peak performance, 64 GB/sec system bandwidth, and that is expandable to 512 CPUs? According to Hewlett-Packard, it's a server, albeit a scalable, parallel one.
The latest HP Examplar S- and X-Class machines boast performance previously re-served for the supercomputer, but with footprints and features appropriate for office floors. This is not surprising, as the Exemplar S- and X-Classes, which are based on 64-bit PA-8000 processors, benefit grandly from HP's acquisition of supercomputing veteran Convex.
Technologies employed on the S Class server, such as a 16-GBit/sec cross-bar interconnect for parallel performance, 2-GBit/sec I/O bandwidth for microsecond response time, and 24 PCI bus I/O slots for connectivity, have their origins on Convex machines. The Exemplars use CMOS chips, however, rather than the gallium arsenide employed by Convex machines.
At the very high end, Exemplar X-Class servers are composed of multiple S-Class machines--up to 32 of them theoretically, although no-body has actually done this. HP intends its Exemplar series to function as applications and storage-management servers in what the company calls its Enterprise File System scheme.
In addition, HP introduced D- and K- Class servers which are also based on the PA-8000 architecture but are not scalable. Exemplar technical servers are priced from $20,000 for a D-Class machine to upwards of $718,000 for an X-Class with 16 CPU, 1 GByte memory, and a 4-GByte disk system.
Monster heat sinks cool trolley electronics
San Francisco--When Bay Area Rapid Transit (BART) trolleys needed upgrading, engineers decided to keep the shells of the existing trolleys, but scrap the innards. The refurbishing will result in an increase in the heat generated by the electronics that operate the trolley lights, emergency alarms, and doors.
ABB Daimler-Benz Transportation North America Inc. (Adtranz), the company working on the trolleys, turned to Aavid, Laconia, NH, to solve the heat problem. Over a 5-year period, Aavid will provide heat sinks in 440 refurbished trolleys to cool the traction drives running motor controls and the auxiliary power inverter units--the electronics that operate lights, emergency alarms, and doors.
"BART's trolleys require twice as much power as other people-moving vehicles to operate and therefore require double the amount of heat dissipation," says Aavid President Max Henderson. "We were able to deliver increased thermal efficiency through the use of new technologies, and also increased the size of the heat sink to handle the increased work load."
Engineers from both Adtranz and Aavid worked together for 12 months to develop a prototype device. It uses four heat pipes--devices that take advantage of liquid-to-vapor phase changes to absorb heat--plus a new form of Aavid's augmented-fin heat sinks to break up airflow boundary layers and promote turbulence.
"Advanced cooling technology was needed because of the existing car size and the anticipated load it will carry," says Aavid's Chris Soule. "All of the electrical and mechanical systems in the shell will be replaced, but the outside will remain the same, while the cars will carry almost twice the mass of other people movers."
New Windows OS targets consumer electronics
Redmond, WA--Microsoft has developed a new Windows operating system for consumer electronic devices. Windows CE will make possible new categories of non-PC business and consumer devices that can communicate with each other, share information with Windows-based PCs, and connect to the Internet.
Microsoft built this compact, portable, 32-bit operating system from the ground up to make it scalable for a broad range of applications. Examples include: handheld PCs; "wallet" PCs; wireless communication devices such as digital information pagers and cellular smart phones; next-generation entertainment and multimedia consoles including DVD players; and Internet-access devices such as Internet TVs, digital set-top boxes, and "web phones."
Surface modeling resolves design conflicts
Elk Grove, IL--Reconciling function with formation in mold making is a difficult task. At Challenge Tool, engineers use SURFMASTER surface-modeling software, part of the EUCLID CAD/CAM Series from Matra Datavision, Andover, MA, to more accurately render molds they make for clients. Says Ken Stoltz, manufacturing engineer at Challenge, "Surface modeling helps in developing subtle but necessary features that make designs more manufacturable."
Challenge creates plastic injection molds for the automotive, electronics, toy, and home-appliance industries. Clients send design specifications to Challenge engineers electronically via IGES, and occasionally by blueprint. Electronic files are converted into 3-D surfaces in SURFMASTER, and blueprint instructions are redrawn from scratch.
Stoltz says a major draw to Euclid was its ability to handle an entire part as an even, clean surface. Maintaining an even surface while designing is important to mold makers. When determining the parting lines that indicate where a mold will separate, for example, designers want to work with a continuous surface to avoid imperfections that may occur in the molded part along the seam.
Another issue related to injection molding is shrinkage of the molded part. Since plastic shrinks as it cools, mold volume must be adjusted to achieve the correct finished part. Models built in SURFMASTER and stored in the EUCLID database can be easily modified to account for shrinkage.
SURFMASTER is also used to generate, edit, and verify toolpaths for controlling Challenge's vertical three-axis machine centers. Toolpaths are displayed and can be postprocessed to create machining simulations before downloading to NC machines. This way, trial runs on the shop floor can be eliminated. SURFMASTER helps reduce the number of false starts and increases the number of molds Challenge completes every year.