Southwest Research Institute

David L Davidson

Thomas E Owen

John B Campbell

Andrew Nagy

Stuart T Schwab

Renee C Graef

Steven B Seida

A column assembly for use in conjunction with a test machine, for inducing high-cycle fatigue (at kilohertz vibration rates) in a specimen of a material under test. The column assembly has isolation masses, a specimen grip, and two actuators, the latter for imparting dynamic forces to the test specimen. The actuators are arranged on the column assembly asymmetrically relative to the test specimen.

Asymmetrical column assembly for high-cycle fatigue test machines

A fretting fixture accessory for a_test machine ( ) that induces high-cycle fatigue (at kilohertz vibration rates) in a specimen of a material under test. The fretting fixture ( ) is clamped to the test specimen ( ), for the purpose of testing for fretting damage. The fixture ( ) is designed to provide both the normal and shearing forces that result in fretting damage.

Fretting fixture for high-cycle fatigue test machines

A test machine (10, 40, 60) for inducing high-cycle fatigue (at kilohertz vibration rates) in a specimen of a material under test. Each test machine (10, 40, 60) provides both dynamic and static loading. One embodiment is an SEM-compatible machine (10), having an inner frame (11) containing symmetrical components on either side of a stationary node. The specimen is placed at this stationary vibration node. Dynamic loading is the result of vibrations provided by two piezoelectric actuators (16) inside the frame (11), one on each side of the node. Static loading is provided by means of two stress rods (12), each extending from an end plate (11a) into the frame (11). A pair of cylindrical couplers (14) is also inside the frame, one coupler (14) on each side of the node. Each coupler (14) is attached to an associated piezoelectric actuator (16) and stress rod (12) such that the static and dynamic loads are transferred to the couplers (14). The specimen is held between the inner faces of each coupler 14 such that the loading is transferred to the specimen. The static and dynamic loading applied to the specimen are independent of each other and separately controllable.

High-cycle fatigue test machine

A method for measuring strain in a sample of material. A reference image is obtained of a surface of the sample. A test machine is used to apply a load to the sample, as determined by a control signal from a system processor. A measurement image is then obtained, and test points on the reference image are located on the measurement image, using an image processor programmed to perform machine vision. The displacements between the location of the test points on the two images are determined. These displacements are used to calculate strain. Each new strain value may be used by the system processor to determine a next load value, so that the load is adjusted in terms of strain parameters.

Biaxial non-contacting strain measurement using machine vision

A method of making fiber-reinforced preceramic and ceramic composites by infiltrating a preform of heat-resistant fibers with a solvent-free thermosetting preceramic polysilazane poller. The invention also comprises the resultant preceramic and ceramic composites.

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San Antonio, TX, United States of America

David L Davidson