Dow's polyolefin film is used by cable manufacturers to provide shielding around electrical and mechanical cables. The film is produced in mill rolls and in coils, in widths from 2 to 8 inches. The new package designs are intended to tighten the wide or narrow coils.

Six-axis transportation simulator shakes, rattles, and rolls Dow polyolefin film.

The Dow project was conducted with Control Power-Reliance (CP-R) of Troy, Mich., using the company's six-axis transportation simulator. The equipment includes a 10 x 10-foot test platform rated for a 15,000-pound payload. Six hydraulic cylinders create simultaneous motion in the x, y, and z directions, plus pitch, roll, and yaw. The equipment can reproduce motion that occurs in all modes of transportation. According to Hans Poehl-mann, the technical manager of the Films and Engineered Laminates Group, the simulator helped the company see what actually happens during a shipping scenario, observing the causes of problems.

Dow ships its narrow coils in one of two ways. In one, the coils lay flat, with the centerline of their coils vertical. The stack is mounted on a wooden pallet and bound with stretch wrap. In the other method, the coils are held on a horizontal rod inside of a wood box, weighing between 2,500 and 5,000 pounds.

In the vertical package, the coils were stacked with alternating wood spacers, explained Timothy Kirch, research leader in the Films and Laminates Group. Originally, these were in the form of radial spokes that had to extend beyond the circumference of the stacked coils for proper support. Stretch wrap forced the spokes toward the center of the stack, allowing the coils to telescope. Also, the spokes were not oriented uniformly, which tended to wrap the coils.

Using a square lattice spacer, which provided better overall load distribution, solved these conditions. Dow also switched the spacer material from wood to Homasote, compressed recycled newsprint that has no water content, preventing rust during shipment. The company also decided to use banding instead of stretch wrap, which allowed too much movement of the entire package; the motion could cause the coils to topple.

For the coils that are oriented horizontally, the package was redesigned for better weight-carrying capability. The load-bearing cradle was modified to handle 5,000 pounds, versus 3,000 for the original design. The box assembly was also changed to maintain a constant shape.

The company's engineers tailor their mixers for a variety of gas-liquid reactions by researching the hydrodynamic conditions of the reaction process, calculating the turbine geometry needed to accommodate it, and designing the equipment. The agitators themselves consist of shrouded radial turbines fixed to a hollow shaft. Annular gas inlet ports are machined into the upper portion of the shaft.

Robin Industries customizes its industrial agitators by analyzing the hydrodynamic condition of the reaction process and calculating turbine geometry.

As the turbine rotates, it causes negative pressure in the central zone that creates a high liquid flow through the inlet ports, drawing gas swiftly into the hollow shaft. The high turbulence of this procedure thoroughly mixes the gas and liquid process chemicals. When the mixture is ejected, the gas is highly dispersed in the liquid, substantially increasing the interface surfaces. The unblended gas moves up to the free liquid surface and is recycled into the liquid by the hollow shaft, thereby increasing the gas contact time and optimizing gas consumption. In addition, the heat exchange coefficient is high, aiding the reaction.

More than 50 companies worldwide use Robin Industries' agitators, including Korea Zinc in Seoul, for hydrometallurgy; Rhone Poulenc in Niort, France, for fermentation; and Certain Teed in Baton Rouge, La., for polymerization.

A design innovation on the high-clearance sprayers is the planetary wheel drive that incorporates an integral hydraulic piston motor designed as a joint effort by Auburn Gear of Auburn, Ind., and Denison Hydraulics of Marysville, Ohio. The Model 43 Power Wheel Plus hydraulic motor was based on Denison's PV piston pumps. The Auburn and Denison design team used Pro/ Engineer software to perform solid three-dimensional modeling and Pro/Mechanica software to conduct finite element analysis to design a compact motor measuring 14.72 inches long. Both software pro-grams were developed by PTC of Waltham, Mass.

Auburn Gear and Denison Hydraulics designed the motors that drive GK Machines' sprayers through fields with crops up to 97 inches high.

One method Denison used to make the motor so compact was to have the gearbox spindle house the motor. The virtue of the Model 43 motor's size is that it enables original equipment manufacturers like GK Machine to simplify their designs.

The new motors drive the spraying machines at either low speed with high torque, or at higher speed at low torque. GK Machine will build different gear ratios into its vehicles to tailor their drive to serve the specific torque and speed requirements of different applications.

The joint mimics the motion of a wrist, Rosheim said, giving access to any point within a hemispherical envelope without singularity or "gimbal lock."

Singularity in a robot's wrist is the area that the robot can't reach, Rosheim explained. The typical roll-pitch-roll joint, of which the split ball and the clevis are common manifestations, both generate what he called "conical voids in the workspace."

To avoid the problem of singularity, a robot wrist designer invokes a pitch-yaw-roll joint, Rosheim said. These joints operate as universal joints do. In their commonest configuration of two stacked single-axis actuators, however, one axis often ends up blocking motion of the other axis, he said. This is gimbal lock, another kind of singularity.

Through pushing and pulling alone, this double Cardan joint hits all points in a hemisphere, while avoiding singularity and backlash.

Prior Ross Heim designs eliminated singularity by translating the wrist motion by way of a train of gears, Rosheim said. But gears introduced backlash, reducing accuracy. The new design uses only the simplest of bearings and links. It is actuated by two push/pull rods.

The design solves the inverse kinematic problem, Rosheim said, making it computationally simple to move the wrist from point to point. Before this design, making a move required an iterative sequence of mathematical operations.

"That's what the inverse kinematic solution does: It's a mathematical model of the wrist. By giving it a linear input, you get an arcuate output of the value that you desire," he said.

Satellite tracking from the rolling, pitching, and yawing deck of a shipis one of many potential uses that exist for the joint.

"If you could see mechanisms as kind of a periodic table of elements, this thing fits a little gap—a hole—in the table," Rosheim said. "We're getting high-range, arcuate motion out of a simple device with simple inputs."

D. Stefan Dancila and Erian Armanios, both aerospace engineers at Georgia Tech, call the concept, in which some groups of fibers run straight and others wavy, "redundant load paths." A patent on tailoring redundant load paths is being issued, and experiments are being conducted on a variety of materials.

Meanwhile, the research team is investigating several applications. One is inflatable space structures, which are being evaluated for use with the International Space Station. Flexible composite webbing containing redundant load paths could reinforce these structures to help them better withstand an accidental internal pressure pulse. Armanios and Dancila also see potential applications in the reinforcement of tethers, mountain-climbing ropes, and crashworthy helicopter seat restraints.

Dancila said they plan to evaluate several materials with appropriate combinations of properties, then develop manufacturing technologies appropriate for each material system, before creating tailored structures.

The researchers came upon the concept by observing the tough tearing response of a plastic mesh bag. When subjected to load, it tears at one location and then another, as force increases. Finally, it gives in and fails completely, Dancila said.

They combined this observation with their understanding of typical failure mechanisms in one-directional fiber-reinforced composite materials. "We already knew that the adjacent failure of a small number of fibers can lead to the formation of a matrix crack that concentrates load on neighboring fibers. These cracks precipitate the overall failure process," Dancila said.

Composite materials made from these high-performance fibers can and do crack and then break. But the energy it takes to break the material increases as the surface area of the fracture increases—in other words, lots of little cracks are better than one big one. "We set out to devise a tailoring concept that would induce a load distribution mechanism, forcing repeated fracture of fibers," Dancila explained. "This mechanism—redundant load paths increase the amount of fracture surface generated—increases the energy dissipated.

"Fibers will start failing," Dancila said. "But in the way it is put together, and because of the matrix that is being used, fibers will fail at many locations, before overall failure."

Dancila estimates that optimal tailored structures may have 10 times the energy dissipation of conventional composites.

USFilter's subsidiary, Zimpro Products of Rothschild, Wis., will supply a Zimpro wet air oxidation system to the National Oil Distribution Co. in Mesaieed, Qatar. National Oil Distribution will use the system to destroy sulfide compounds and organic contaminants in the spent caustic from its chemical processing plant. The system produces an effluent that can be easily treated in a conventional wastewater treatment plant.

Management of the Pluspetrol gas processing plant in Ramos, Argentina, refurbished process control systems and remote data acquisition units using PlantWeb computer hardware and software from Fisher-Rosemount of Austin, Texas. Pluspetrol expects to realize significant savings in support, maintenance, and operations at its northern Argentina gas processing facility by using PlantWeb's intelligent fieldbus devices and Asset Management Solutions to enable the plant's administrators to configure, monitor, diagnose, and calibrate remote field devices and to perform online upgrades.

The Farmers Insurance Group of Los Angeles is offering degreed or licensed engineers a 15 percent discount on auto insurance.

Thanks to a robot for cutting and retrieving submerged timber, Aquatic Cellulose International Corp. of Vernon, B.C., recently shipped $130,000 worth of Brazilian hardwood to the United States. The robot harvests the trees left behind after rivers were dammed, while eliminating the hazards to, and the expense of, divers.

Schenectady, N.Y.-based GE Power Systems received multiyear service contracts from the Southern Co. of Atlanta, totaling $575 million, which cover combined-cycle power plants being built by Southern Co. affiliates in the southeastern United States. The service agreements support GE 7FA gas turbine-generators, GED11 steam turbines, Mark V Speedtronic control systems, and auxiliary equipment that GE will supply to those plants.

home | features | news update | marketplace | departments | about ME | back issues | ASME | site search

© 2000 by The American Society of Mechanical Engineers