Overview

The University of Texas at Austin has grown its Center for Electromechanics into a world class center for modeling, analyzing, designing, and fabricating advanced electrical power generation and distribution systems. The Center staff includes researchers recognized as world leaders in the development of advanced energy storage and power generation rotating machines for both intermittent and continuous duty applications. These capabilities are supported by a dedicated laboratory and fabrication facilities unmatched by any university research facility in the United States.

The laboratory, houses extensive fabrication, assembly, and testing facilities in a 140,000 square ft air conditioned high bay laboratory. The 70 ft tall high bay features two 25 ton cranes with an additional 25 ton crane servicing a machine shop area. In addition to the main high bay laboratory, an additional 10,000 square ft of air conditioned space is available in 8 satellite labs, along with a 1,200 square ft welding/fabrication shop.

high bay
Main high bay: Contains a granite surface plate for dimensional inspections. A 500 ton hydraulic assembly press

Machine and Fabrication Shop

The Center uses a distributed manufacturing approach to fabrication. Novel machines are designed by the research staff and component testing is done to provide the engineering data needed to fabricate these first-of-a-kind machines. Components that can be fabricated using conventional industrial practices are fabricated by experienced suppliers. When materials or other factors beyond current industrial practice are required, the Center researchers develop new fabrication processes in-house. If these new processes are needed routinely, they are transferred to competent industrial suppliers. In this way, the researchers remain focused on novel systems, but the results of the earlier work are available to others through a competent base of industrial suppliers.

Typically, final fabrication and testing is done in the Center facilities. When there is a high likelihood that subsequent similar machines will be needed, the Center teams with a manufacturer who participates in the assembly and test activities. This is an effective way to transfer the technology to an industrial supplier.

machine
Machine Shop: In the foreground is a HAAS Model VF7CNC machining center and the tool crib window is visible at the right center edge of the picture. The main machine shop door is visible in the background, along with the entrance, to the right, to the auxiliary machine shop area seen below

The Center’s machining capabilities were updated in 2003 with the installation of several new machine tools, including lathes, manual mills, and a horizontal band saw. Important additions to the machine shop include a HAAS Model VF7 CNC machining center that provides fully programmable 4-axis machining and a Hurco machining center.

HAAS machine
In the Machine Shop, the HAAS (left) and HURCO (right) Machining Centers provides fully programmable 4-axis machining.

The machine shop is also supported by a fully stocked tool crib, including measuring and inspection tools under NIST traceable calibrations. Although the Center does not have an on-site Coordinate Measuring Machine (CMM), one is available at The University of Texas at Austin Applied Research Laboratories, also located at the Pickle Research Campus. Below is a list of the machine tools available in the Center’s Machine Shop.

UT-CEM Machine Shop Equipment Listequipment list

In addition to the extensive machining capabilities, the Center also maintains a welding and fabrication shop. The welding shop features a 2-axis programmable Ingersoll Rand/ESAB Autopath GX 60,000 psi abrasive waterjet cutting system capable of cutting metals, ceramics, and composite materials without introducing significant heat into the part. An ESAB 2-axis combination oxy-acetylene and plasma cutter is also located in the welding shop, along with both metal/inert gas (MIG) and tungsten/inert gas (TIG) welding machines.

Testing Capabilities

The facility also houses a high energy spin test bunker designed to safely contain a 20 psig internal overpressure. The 600 square ft. spin test bunker features 30 in. thick fiberglass reinforced concrete walls with 6 in. thick aluminum door, window, and roof closures. tiedownA stainless steel tie down structure is rated for 5 million pound vertical load and torque loads of up to 20 million lb-ft. A metal building located immediately adjacent to the spin test bunker was designed for installation and testing of gas turbines, with openings for intake air and integral exhaust ducting in the roof. This structure can also be used for local instrumentation and data acquisition for experiments being conducted in the spin test bunker.

A 180 ft deep vertical gun range is located between the north end of the main high bay and the spin test bunker. The 9-story vertical range is serviced by a 3-person elevator and currently houses a 90 mm bore x 10 m long railgun and bore honing system.

bunker
This exterior view of the North end of the main high bay shows the vertical gun range, the spin test bunker, the turbine enclosure, and the honing tower above the gun range.

Composite Fabrication

The laboratory houses several specialized manufacturing and testing facilities designed to support prototype development and testing efforts.

There is significant in-house expertise in the design, analysis, and manufacture of composite structures used in high performance rotating machines. To aid in rapidly prototyping complex composite structures with known mechanical properties, the Center developed a set of linked computer codes (CEMWIND) that generates detailed material property data that can be exported to finite element analysis codes, along with programs that control fiber placement and orientation in the filament winding machine. One winding machine is a McClean Anderson 5-axis CNC filament winding machine installed in a dedicated low lab with local environmental control. The system is capable of processing parts up to 66 in. in diameter and 40 ft long using both wet winding and pre-impregnated fiber tows. The winding machine has been modified with a specially designed fiber payout system to enable processing of high modulus graphite fibers with minimal fiber damage.

winding
Composite winding machine

The newest winding machine is an ENTEC 5-axis CNC filament winding machine installed at the end of the McClean Anderson machine. It has been modified to accommodate heavy mandrels up to 15 ft in length. This machine has also been modified with a special payout system for advanced graphite and glass fiber systems used in high performance rotors.

A dedicated autoclave, manufactured by American Autoclave, is used to cure composite structures. The fully programmable autoclave is rated for 650° F and 250 psig and can process composite parts up to 7 ft in diameter and 11 ft long. The autoclave can process a range of materials including epoxies, cyanate esters, BMIs, some lower temperature polyimides, and thermoplastics. In addition to the autoclave, the facility includes a 12 ft x 20 ft curing oven with programmable time/temperature profiles for curing wet wound and resin transfer molded (RTM) composite structures and adhesively bonded assemblies.



To support the composites development program, the Center researchers developed and validated specialized testing equipment and procedures to measure the hoop modulus and strain to failure of filament wound composite materials. The testing is required to quickly evaluate the performance of different fiber and resin combinations or variations in the processing procedures to ensure that the delivered mechanical properties satisfy the design requirements. The test equipment and procedures are under review by the American Society for Testing and Materials (ASTM) as a new standard for quantifying mechanical properties of composite materials. Composite specimens are instrumented with strain gages and then subjected to internal hydraulic pressure, creating predominantly circumferential (hoop) stresses in the specimen. Data from multiple specimens is processed using MIL-HDBK-17 statistical analysis procedures to generate A-Basis and B-Basis design allowables.

The fabrication of advanced composite structures also required the development of custom fixtures for assembly of composite structures. Composite rotors are typically constructed using multiple concentric rings assembled with interference fits. This assembly approach is used to create radial preload and control the magnitude and distribution of radial stresses in the rotor structure. The facility includes custom hydraulic presses specifically designed by Center researchers for assembly of composite rotors. The largest assembly press is 40 ft tall and is capable of generating forces in excess of 550 tons; a smaller assembly press is 10 ft tall and rated for 200 tons.

Electronics and Instrumentation

In-house testing and experiments are supported by a wide array of electronic test equipment and instrumentation. The facility contains two dedicated EMI/RFI shielded control rooms to isolate instrumentation and controls during high energy testing. Fast transient data can be collected using digital storage oscilloscopes and custom designed data acquisition systems are available to monitor and analyze the performance of rotating electrical machines, including rotor vibration and housing accelerations in both time and frequency domains.

In addition to various bench top instrumentation power supplies, the Center also has a 250 V 6,000 A dc power supply located in the main high bay.

 
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