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Bar-Cohen, Yoseph

Publications and source records attributed to Bar-Cohen, Yoseph.

At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Real-Time Leaky Lamb Wave Spectrum Measurement and Its Application to NDE of Composites

Numerous analytical and theoretical studies of the behavior of leaky Lamb waves (LLW) in composite materials were documented in the literature. One of the key issues that are constraining the application of this method as a practical tool is the amount of data that needs to be acquired and the slow process that is involved with such experiments. Recently, a methodology that allows quasi real-time acquisition of LLW dispersion data was developed. At each angle of incidence the reflection spectrum is available in real time from the experimental setup and it can be used for rapid detection of the defects. This technique can be used to rapidly acquire the various plate wave modes along various angles of incidence for the characterization of the material elastic properties. The experimental method and data acquisition technique will be described in this paper. Experimental data was used to examine a series of flaws including porosity and delaminations and demonstrated the efficiency of the developed technique.

Lih, Shyh-Shiuh↗
NASA NTRS1998

Ultrasonic Drilling and Coring

A novel drilling and coring device, driven by a combination, of sonic and ultrasonic vibration, was developed. The device is applicable to soft and hard objects using low axial load and potentially operational under extreme conditions. The device has numerous potential planetary applications. Significant potential for commercialization in construction, demining, drilling and medical technologies.

Bar-Cohen, Yoseph↗
NASA NTRS1997

Autonomous Rapid Inspection of Aerospace Structures

Aging aircraft structures and composite materials are requiring rapid inspection of large areas. Removal from the aircraft for NDE at an inspection facility is not economical as compared to field inspection. Detection and characterization of defects are labor intensive, time consuming and when the process is manual the result are subjected to human error.

control inspection systems↗
NASA NTRS1997

Autonomous Rapid Inspection of Aerospace Structures

Effective assurance of the integrity and performance of aging aircraft sturnctures, particularly those that are made of composite materials, requires rapid inspection of large area. Removal from the aircraft for NDE at an inspection facility is no economical and preferable the inspection should be performed at the field setting.

Aerospace Structure↗
NASA NTRS1997

Pump having pistons and valves made of electroactive actuators

The present invention provides a pump for inducing a displacement of a fluid from a first medium to a second medium, including a conduit coupled to the first and second media, a transducing material piston defining a pump chamber in the conduit and being transversely displaceable for increasing a volume of the chamber to extract the fluid from the first medium to the chamber and for decreasing the chamber volume to force the fluid from the chamber to the second medium, a first transducing material valve mounted in the conduit between the piston and the first medium and being transversely displaceable from a closed position to an open position to admit the fluid to the chamber, and control means for changing a first field applied to the piston to displace the piston for changing the chamber volume and for changing a second field applied to the first valve to change the position of the first valve.

Bar-Cohen, Yoseph↗
NASA NTRS1997

Rotary Ultrasonic Motors Actuated by Traveling Flexural Waves

Ultrasonic rotary motors are being developed as acutators for miniature spacecraft insturments and subsystems. The technology that has emerged in commercial products requires rigorous analytical tools for effective design of such motors. An analytical model was developed to examine the excitation of flexural plate wave traveling in rotary piezoelectrically actuated motor.

Piezoelectric↗
NASA NTRS1996

Wave Propagation in Anisotropic Composite Plates

This paper is concerned with the development of wave propagation based cost-effective ultrasonic techniques for the nondestructive materials and defects characterization in advanced structural composites. A theoretical model that captures the most significant features of wave phenomena in fiber reinforced composites is described. Laboratory tests are shown to yield results that are in excellent agreement with those obtained from the theoretical model.

nondestructive testing ultrasonic composites lamin↗
NASA NTRS1996

(abstract) NDE and Advanced Actuators at JPL

JPL is responsible for deep space exploration using spacecraft and telerobotic technologies. Since all JPL's missions are one of a kind and hardware dependent, the requirements for nondestructive evaluation (NDE) of the materials and structures that are employed are significantly more stringent than the ones for conventional aerospace needs. The multidisciplinary technologies that are developed at JPL, particularily the ones for the exploration of Mars, are finding applications to a wide variety of NDE applications. Further, technology spin-offs are enabling the development of advanced actuators that are being used to drive various types of telerobotic devices. A review will be given of the recent JPL NDE and advanced actuators activity and it will include several short videos.

nondestructive evaluation actuators telerobotics t↗
NASA NTRS1996

International NDT Technical Collaboration Using the Internet

This paper reviews the capability of the Internet as a world-wide NDT communication tool for technical collaboration, dissemination of information and international standards. This paper was written by authors that never personally met (except for two) and despite thousands of miles distance between them the authors managed to work as a team to complete this paper in a very time efficient manner. This success is attributed to the power of the Internet and it represents a simple example of the.

Internet communication information exchange web si↗
NASA NTRS1996

Rapid Inspection of Aerospace Structures - Is It Autonomous Yet?

The trend to increase the usage of aging aircraft added a great deal of urgency to the ongoing need for low-cost, rapid, simple-to-operate, reliable and efficient NDE methods for detection and characterization of flaws in aircraft structures. In many cases, the problem of inspection is complex due to the limitation of current technology and the need to disassemble aircraft structures and testing them in lab conditions. To overcome these limitations, reliable field inspection tools are being developed for rapid NDE of large and complex-shape structures, that can operate at harsh, hostal and remote conditions with minimum human interface. In recent years, to address the need for rapid inspection in field conditions, numerous portable scanners were developed using NDE methods, including ultrasonics, shearography, thermography. This paper is written with emphasis on ultrasonic NDE scanners, their evolution and the expected direction of growth.

Crawling System autonomous robotics↗
NASA NTRS1996

(abstract) Application of Space Technology to NDE at JPL

JPL is responsible for the deep space exploration using spacecraft and telerobotic technologies. Since all its missions are one of a kind and hardware dependent, the NDE requirements are significantly more stringent than the ones for aerospace conventional needs. The multidisciplinary technologies that have been developed at JPL, particularly the ones that were developed for the exploration of Mars, can find applications to a wide variety of NDE applications. A review will be given of the recent JPL NDE activity and it will include several short videos.

nondestructive evaluation Mars spacecraft testing↗