Government of the United States of America, As Represented by the Secretary of Commerce

Other

Alfred V Clark

George A Alers

Thanh Nguyen

Kevin Coakley

Christopher Hehman

R Bruce Thompson

Brian Barnes

Stephen R Schaps

A method and apparatus for measurement of stress in a specimen utilizing a motorized electromagnetic acoustic transducer (EMAT). Stress causes a rotation of the pure-mode polarization directions of SH-waves and a change in the phase of waves polarized along these certain directions. The method utilizes a rotating small-aperture EMAT, connected to a processor, to measure phase and amplitude data as a function of angle. The EMAT is placed on a workpiece at the location where the stress is to be measured. The acoustic birefringence B is determined from the normalized difference of these phases. From these data, an algorithm calculates values of B and &PHgr;. The workpiece is then stressed or its stress state is changed. The values are measured again at the same location. Stress is determined from the change in B and &PHgr;.

Ultrasonic strain gage using a motorized electromagnetic acoustic transducer

A method for measurement of stress in a specimen utilizing a motorized electromagnetic acoustic transducer (EMAT). Stress causes a rotation of the pure-mode polarization directions of SH-waves and a change in the phase of waves polarized along these certain directions. The method utilizes a rotating small-aperture EMAT, connected to a processor, to measure phase and amplitude data as a function of angle. The EMAT is placed on a workpiece at the location where the stress is to be measured. The acoustic birefringence B is determined from the normalized difference of these phases. From these data, an algorithm calculates values of B. and &phgr;. The workpiece is then stressed or its stress state is changed. The values are measured again at the same location. Stress is determined from the change in B and &phgr;.

The present invention is directed toward a method and apparatus for the ncontact inspection of workpieces having a plate-like portion of the first part joined via an inertia weld to the end of a second part extending away from the plate-like portion. The apparatus and method are particularly apt for the non-contact inspection of driver inflator igniter canisters for airbag applications, such canisters having a spool-shaped structure with outer walls which restrict access to the internal inertia welds for inspection. To achieve non-contact inspection, the invention comprises electromagnetic acoustic transducer means which generate a pulsed inspection signal and a detection signal. In one embodiment, the inspection signal comprises shear acoustic waves which are polarized parallel to the outer surface of the second member (e.g., the central web member of an inflator igniter canister), and a pulse/echo detection approach is employed. Separate electromagnetic acoustic transducer assemblies are utilized to generate the inspection and detection signals, with the transmit assembly being positioned between the detection assembly and workpiece.

Non-contact method and apparatus for inspection of inertia welds

An indication of the formability of metallic sheet is determined using a correlation between nondestructively measurable ultrasonic properties and a formability index. A calibration relation is initially established by measuring ultrasonic velocities at various angles to the rolling direction of sheet specimens with noncontacting electromagnetic acoustic transducers, calculating an ultrasonic correlation parameter from the measurements, destroying the specimens in tensile tests to measure a formability index, and then correlating the ultrasonic correlation parameter with the formability index. Once this relationship is established, the formability index of a working sample, which is not to be destroyed, is found by making the same types of ultrasonic property measurements on the working sample, calculating the ultrasonic correlation parameter for the working sample, and then employing the previously established correlation to ascertain the formability index for the working sample.

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Boulder, CO, United States of America

Alfred V Clark