Internal Friction in Metals

Citation

Hudson, Donald Ellis (1942) Internal Friction in Metals. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z2V9-C551. https://resolver.caltech.edu/CaltechETD:etd-05232003-090926

Abstract

(1) The mean damping capacity of steel over a stress range of several hundred pounds per square inch is a physical property of the material, the value of which can be checked accurately by successive tests on the same specimen, with the apparatus and method developed in the course of this investigation.

(2) The results of the damping capacity test can be duplicated accurately for successive specimens of the same material.

(3) There is a strong possibility that although the general trend of the stress-damping capacity relationship may follow a simple law, the true relationship for a material such as steel is extremely complex and somewhat erratic.

(4) The stress-damping capacity relationship indicates that for steel the damping does not follow the viscous friction law, although for low stresses the assumption of constant damping would not be far in error. In the case of brass, the internal friction was practically independent of stress for the stress range covered in the tests.

(5) The damping capacity of the specimens tested was found to be a function of the maximum torsional stress set up in the specimen rather than a function of the maximum shear stress or of the maximum normal stress.

(6) In the case of materials whose damping capacity decreases with decreasing stress, the apparent damping capacity measured from a solid test specimen is lower than the true specific damping capacity of the material.

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