Engineering topics
Bar-Cohen, Y.
Publications and source records attributed to Bar-Cohen, Y..
The Multifunction Automated Crawling System (MACS)
A new robotic crawler is being developed for inspection of large aircraft external surfaces.
Measuring the Thickness and Elastic Properties of Electroactive Thin-film Polymers Using Platewave Dispersion Data
Electroactive thin-film polymers are candidate sensors and actuators materials [1,2]. They are also finding a significant potential for applications in muscle mechanisms and micro-electro-mechanical systems (MEMS).
Multifunction Automated Crawling System (MACS)
Nondestructive Evaluation (NDE) instruments and sensors are becoming smaller with enhanced computer controlled capability and increasingly used commercially available hardware and software.
NASA NDE Working Group Newsleter, April 1996, Vol. 4, No.2
This is a newsletter of the NSAS NDE working group.
NASA NDE Working Group Newsletter, Vol. 4 No. 1, 1996
None given. This is a quarterly newsletter of the NASA NDE working group.
International NDT Technical Collaboration Using the Internet
This paper summarizes the technology status, highlights current NDT Internet activities and suggests action items for international collaboration.
NASA NDE Working Group Newsletter
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Mars Lander Robotics and Machine Vision Capabilities for in situ Planetary Science
We overview our recent progress in lander-based robotics for Mars planetary science. Utilizing a 1:1 scale laboratory replica of the NASA Mars Surveyor '98 mission, JPL engineers and Mars sciencce colleagues have demonstrated approaches to lander science functions such as robotic sample acquisiiton and deposition, end-effector based microscopic viewing, hand-carried science instrument data collection, and science instrument emplacement by a robot.
Miniature Ultrasonic Rotary Motors
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Solid-State Actuation as a Driving Mechanism for Miniature Spacecraft
Piezoelectric rotary motors are being developed to form a drive mechanism for robotics, miniature spacecraft instruments and subsystems. The technology that has recently emerged in commercial products is associated with empirical design. An analytical model was developed for the motor and it is currently being modified to account for the effect of space environment. The interface between the rotor and stator components and the friction forces are investigated to determine the propelling effect of the stator. The model predicts motor performance and can be used to optimize the design of miniature high-torque motors.
NDE of Composite Materials Using Remote Health Monitoring Techniques
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Influence of Damage on the Vibration Response of Composite Laminates
The influence of delaminations on the natural frequencies and mode shapes of a composite.
Low Frequency Guided Plate Waves Propagation in Fiber Reinforced Composites
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Low Frequency Guided Plate Waves Propagation in Fiber Reinforced Composites
Conventional destructive techniques for the determination of the elastic stiffness constants of composite materials can be costly and often inaccurate. Reliable nondestructive evaluation methods for monitoring the integrity of composite materials and structures are needed. Guided wave propagation in isotropic plate have been studied. Studies on the low frequency symmetric guide waves are presented.
NASA NDE Working Group Newsletter, Vol. 3, No. 2, 1995
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High Precision Piezoelectric Linear Motors for Operations at Cryogenic Temperatures and Vacuum
The use of an electromechanical device for optically positioning a mirror system during the pre-project phase of the Pluto Fast Flyby mission was evaluated at JPL. The device under consideration was a piezoelectric driven linear motor functionally dependent upon a time varying electric field which induces displacements ranging from submicrons to millimeters with positioning accuracy within nanometers.