Measuring and testing – Specimen stress or strain – or testing by stress or strain... – By loading of specimen
Patent
1996-06-25
1998-06-16
Dombroske, George M.
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
By loading of specimen
73794, 73814, G01N 322, G01N 326
Patent
active
057674159
ABSTRACT:
A method for non-destructive determination of a fatigue limit for a component includes two sub-methods which may be performed separately, or in any order. A direct-deformation sub-method includes measuring micro-plastic deformation corresponding to each of a plurality of different known values of stress applied to the component, and identifying a critical value of stress corresponding to a change in the relationship between stress and micro-plastic deformation. An internal-friction damping method includes initiating torsional oscillations in the component, measuring an initial angular amplitude of oscillation, A.sub.0, and a final angular amplitude of oscillation, A.sub.n at the end of the number, n, of oscillations. This process is repeated a number of times and, for each pair of measurements, a corresponding measure of damping is calculated. A critical value of initial angular amplitude corresponding to a change in the relationship between amplitude and damping is then calculated. All testing is preferably performed torsionally, thereby making the method applicable to a wide range of real components of different shapes. Applied stresses are limited to below the yield point of the materials tested and do not affect the properties of the material.
REFERENCES:
patent: 3911734 (1975-10-01), Mehdizadeh
patent: 4567774 (1986-02-01), Manahan et al.
patent: 5022273 (1991-06-01), Evans
patent: 5152172 (1992-10-01), Leon et al.
patent: 5156053 (1992-10-01), Shiraishi et al.
patent: 5531122 (1996-07-01), Chatham et al.
Dombroske George M.
Friedman Mark M.
Noori Max H.
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