Mechanical & Fluid Systems

'Snap' Design Mimics Venus Flytrap

A team led by physicist Christian Santangelo at the University of Massachusetts Amherst uses curved creases to give thin shells a fast, programmable snapping motion. The technique – inspired by the natural "snapping systems" like Venus flytrap leaves and hummingbird beaks – avoids the need for complicated materials and fabrication methods when creating structures with fast dynamics.

Posted in: News, Joining & Assembly

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Gear Shift Modeling and Analysis for Automatic Transmissions in MapleSim

In this paper, a simple dynamic physical model of an automatic transmission was created to evaluate all required forces and motion characteristics of the system during the shift process. Gear shift quality was assessed by setting different timing sequences for the engage/disengage process of the frictional components (pressure on the clutches), during the upshift process. The output torque of the transmission was analyzed under two conditions, with the timing to apply/remove pressure from the clutches being different in both cases.

Posted in: White Papers

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Proper Bearing Handling Can Help Prevent Failures

Ball bearings are extremely precise mechanisms, which in many cases have geometrical tolerances measured in millionths of an inch. When handling, inspecting or mounting bearings, one should treat them as precision instruments. Most bearing failures are caused by the user's poor handling techniques.

Posted in: White Papers

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DC Transformer

This transformer can fill a role in which DC conversion potential, coupled with power filtering/storage capability, is required in high-DC power transmission. John F. Kennedy Space Center, Florida A component-level DC transformer was developed in which no alternating currents or voltages are present. It operates by combining features of a homopolar motor and a homopolar generator, both DC devices, such that the output voltage of a DC power supply can be stepped up (or down) with a corresponding step down (or up) in current. The DC transformer should be scalable to low-megawatt levels, but is more suited to high-current than high-voltage applications.

Posted in: Briefs, TSP

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Wallops Flight Facility 6U Advanced CubeSat Ejector (ACE)

Goddard Space Flight Center, Greenbelt, Maryland Six-unit (6U) CubeSats are recognized as the next nanosatellite to be considered for standardization. The CubeSat standard established by California Polytechnic University (Cal Poly), which applies to 1U–3U sizes, has proven to be a valuable asset to the community. It has both provided design guidelines to CubeSat developers and a consistent, low-risk interface to launch service providers. This has ultimately led to more flight opportunities for CubeSats. A similar path is desired for the 6U CubeSat. Through this process of standardization, a consistent, low-risk interface for the 6U needs to be established.

Posted in: Briefs, TSP

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Improved Attachment Design for Ceramic Turbine Blades Via Hybrid Concepts

This approach facilitates increased precision and ease of handling the blades during assembly. John H. Glenn Research Center, Cleveland, Ohio This innovation is a hybrid metal-ceramic matrix composite (CMC) turbine blade in which a SiC/SiC CMC airfoil section is bonded to a single-crystal superalloy root section in order to mitigate risks associated with an all-CMC blade inserted in a superalloy disk. This will allow current blade attachment technology (SX blade with a dovetail attachment to a slotted Ni disk) to be used with a ceramic airfoil. The bond between the CMC and single crystal will be primarily mechanical in nature, and enhance with clamping arising from thermal expansion mismatch. Two single-crystal root sections will be bonded to each other using diffusion bonding at temperatures near 1,200 °C. The single crystals will form a clamshell around the CMC, with little or no gap between the metal and ceramic. Upon cooling, the metal will shrink around the CMC to firmly clamp it. It is envisioned that this will allow the blade root to operate at temperatures up to about 800 °C. Single crystals will resist stress relaxation at this temperature, thus maintaining clamping loads for long lives. The hybrid concept plus the method of manufacture is new technology.

Posted in: Briefs, TSP

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Powdered Copper Cryogenic Heat Exchanger

This technology provides a high level of thermal performance while dramatically simplifying the chore of determining safety factors. John F. Kennedy Space Center, Florida This work involved designing a liquid nitrogen cold-plate heat exchanger with a high thermal mass using code-standard, high-pressure tubing. High thermal mass requires a substantial amount of material, so heat exchangers of this type are usually fabricated from a solid piece of metal (such as copper) with fluid paths machined into the component. However, standard tubing was desired for the fluid path due to its pressure rating and predictability. The key problem was how to embed copper tubing into a larger mass while maintaining good heat transfer properties.

Posted in: Briefs, TSP

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