Mechanical & Fluid Systems

Folded Resonant Horns for Power Ultrasonic Applications

Ultrasonic actuators can be made shorter.

Folded horns have been conceived as alternatives to straight horns used as resonators and strain amplifiers in power ultrasonic systems. Such systems are used for cleaning, welding, soldering, cutting, and drilling in a variety of industries. In addition, several previous NASA Tech Briefs articles have described instrumented drilling, coring, and burrowing machines that utilize combinations of sonic and ultrasonic vibrational actuation. The main advantage of a folded horn, relative to a straight horn of the same resonance frequency, is that the folded horn can be made shorter (that is, its greatest linear dimension measured from the outside can be made smaller). Alternatively, for a given length, the resonance frequency can be reduced. Hence, the folded-horn concept affords an additional degree of design freedom for reducing the length of an ultrasonic power system that includes a horn.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Downsizing, Amplifiers, Amplifiers, Tools and equipment, Product development, Drilling, Industrial vehicles and equipment

Rollable Thin Shell Composite-Material Paraboloidal Mirrors

These lightweight focusing mirrors can be stored in fairly narrow cylinders.

An experiment and calculation have demonstrated the feasibility of a technique of compact storage of paraboloidal mirrors made of thin composite-material (multiple layers of carbon fiber mats in a polymeric matrix) shells coated with metal for reflectivity. Such mirrors are under consideration as simple, lightweight alternatives to the heavier, more complex mirrors now used in space telescopes. They could also be used on Earth in applications in which gravitational sag of the thin shells can be tolerated.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Mirrors, Imaging, Imaging and visualization, Imaging, Imaging and visualization, Composite materials, Lightweight materials, Materials properties

Cellular Pressure-Actuated Joint

Pockets in one of the sealing members would help maintain differential pressure.

A modification of a pressure-actuated joint has been proposed to improve its pressure actuation in such a manner as to reduce the potential for leakage of the pressurizing fluid. The specific joint for which the modification is proposed is a field joint in a reusable solid-fuel rocket motor (RSRM), in which the pressurizing fluid is a mixture of hot combustion gases. The proposed modification could also be applicable to other pressure- actuated joints of similar configuration.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Sensors and actuators, Sensors and actuators, Joining, Pneumatic systems, Rocket engines

Force-Measuring Clamps

Clamping forces can be measured easily and quickly.

Force-measuring clamps have been invented to facilitate and simplify the task of measuring the forces or pressures applied to clamped parts. There is a critical need to measure clamping forces or pressures in some applications — for example, while bonding sensors to substrates or while clamping any sensitive or delicate parts. Many manufacturers of adhesives and sensors recommend clamping at specific pressures while bonding sensors or during adhesive bonding between parts in general.

Posted in: Briefs, Mechanical Components, Mechanics, Sensors and actuators, Sensors and actuators, Joining, Adhesives and sealants, Test equipment and instrumentation

Multiple-Use Mechanisms for Attachment to Seat Tracks

These could serve as standard or universal seat-track clamps.

A Seat Track Attach Mechanism (SAM) is a multiple-use clamping device intended for use in mounting various objects on the standard seat tracks used on the International Space Station (ISS). The basic SAM design could also be adapted to other settings in which seat tracks are available: for example, SAM-like devices could be used as universal aircraft- seat-track mounting clamps.

Posted in: Briefs, Mechanical Components, Mechanics, Seats and seating, Seats and seating, Mountings, Spacecraft

Tool for Bending a Metal Tube Precisely in a Confined Space

This tool offers capabilities that prior tools do not.

A relatively simple, manually operated tool enables precise bending (typically, within ±1/2° of the specified bend angle) of a metal tube located in a confined space, with a minimum of flattening of the tube and without significant gouging of the tube surface. The tool is designed for use in a situation in which the tube cannot be removed from the confined space for placement in a conventional bench- mounted tube bender. The tool is also designed for use in a situation in which previously available hand-held tube benders do not afford the required precision, do not support the tube wall sufficiently to prevent flattening or gouging, and/or do not fit within the confined space.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Tools and equipment, Product development

Touchdown Ball-Bearing System for Magnetic Bearings

In the event of a touchdown, ball bearings provide full support.

The torque-limited touchdown bearing system (TLTBS) is a backup mechanical- bearing system for a high-speed rotary machine in which the rotor shaft is supported by magnetic bearings in steady-state normal operation. The TLTBS provides ballbearing support to augment or supplant the magnetic bearings during startup, shutdown, or failure of the magnetic bearings. The TLTBS also provides support in the presence of conditions (in particular, rotational acceleration) that make it difficult or impossible to control the magnetic bearings or in which the magnetic bearings are not strong enough (e.g., when the side load against the rotor exceeds the available lateral magnetic force).

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Bearings

Flux-Based Deadbeat Control of Induction-Motor Torque

Graphical constructions provide insight into solutions of control problems.

An improved method and prior methods of deadbeat direct torque control involve the use of pulse-width modulation (PWM) of applied voltages. The prior methods are based on the use of stator flux and stator current as state variables, leading to mathematical solutions of control equations in forms that do not lend themselves to clear visualization of solution spaces. In contrast, the use of rotor and stator fluxes as the state variables in the present improved method lends itself to graphical representations that aid in understanding possible solutions under various operating conditions. In addition, the present improved method incorporates the superposition of high-frequency carrier signals for use in a motor-self-sensing technique for estimating the rotor shaft angle at any speed (including low or even zero speed) without need for additional shaft-angle-measuring sensors.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Electronic control systems, Electronic control systems, Electric motors

Piezoelectric Positioning Enables Vibration Assisted Machining

Triangle-shaped actuators create precise ultrafast elliptical diamond tool movement.

A precision piezoelectric positioning system with high-bandwidth and high-power enables a new class of precision machining called Vibration Assisted Machining. The actuator and drive electronics optimize stroke, stiffness and dynamic response of the diamond tool.

Posted in: Briefs, Mechanical Components, Mechanics, Electronic control systems, Sensors and actuators, Electronic control systems, Sensors and actuators, Machining processes, Manufacturing equipment and machinery, Vibration, Vibration

Accurate Spring Testing

Load-testing machine features can affect the accuracy, precision, repeatability, and reproducibility of test results.

Virtually all spring manufacturers must test their products with some kind of load testing machine. Testing ensures that the product is produced and shipped within the customer's specifications. Or does it? Disputes over test results still occur that can cause a multitude of costly problems: returned product, delayed payment, product liability, or customer dissatisfaction. The quality of a spring testing program can largely affect these problems and their associated cost.

Posted in: Briefs, Mechanical Components, Mechanics, Springs, Quality control, Reliability, Quality control, Reliability, Performance tests, Test procedures

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