Method and apparatus for determining material structural integrity
First Claim
1. A method for evaluating the structural integrity of a sample of a material by the sample'"'"'s damping loss factor, said method comprising the steps of:
- isolating vibrationally said sample;
vibrating a portion of said sample at a point remote from a suspension point of said sample over a preselected range of frequencies by applying sufficient vibrational force at each frequency in said preselected range of frequencies to vibrate said portion, said portion vibrating at a different vibrational velocity at each frequency;
measuring vibrational velocity as a function of time of said sample over said preselected range of frequencies to generate a plurality of vibrational velocity measurements;
computing a drive point mobility of said sample over said preselected range of frequencies, said drive point mobility derived from said pluralities of vibrational force and velocity measurements;
computing a damping loss factor of said sample from said drive point mobility; and
comparing said damping loss factor of said sample with a reference damping loss factor for said material to determine whether said sample behaves differently than said reference material.
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Accused Products
Abstract
A non-destructive method and apparatus for determining the structural integrity of materials by combining laser vibrometry with damping analysis techniques to determine the damping loss factor of a material. The method comprises the steps of vibrating the area being tested over a known frequency range and measuring vibrational force and velocity as a function of time over the known frequency range. Vibrational velocity is preferably measured by a laser vibrometer. Measurement of the vibrational force depends on the vibration method. If an electromagnetic coil is used to vibrate a magnet secured to the area being tested, then the vibrational force is determined by the amount of coil current used in vibrating the magnet. If a reciprocating transducer is used to vibrate a magnet secured to the area being tested, then the vibrational force is determined by a force gauge in the reciprocating transducer. Using known vibrational analysis methods, a plot of the drive point mobility of the material over the preselected frequency range is generated from the vibrational force and velocity measurements. The damping loss factor is derived from a plot of the drive point mobility over the preselected frequency range using the resonance dwell method and compared with a reference damping loss factor for structural integrity evaluation.
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Citations
20 Claims
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1. A method for evaluating the structural integrity of a sample of a material by the sample'"'"'s damping loss factor, said method comprising the steps of:
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isolating vibrationally said sample; vibrating a portion of said sample at a point remote from a suspension point of said sample over a preselected range of frequencies by applying sufficient vibrational force at each frequency in said preselected range of frequencies to vibrate said portion, said portion vibrating at a different vibrational velocity at each frequency; measuring vibrational velocity as a function of time of said sample over said preselected range of frequencies to generate a plurality of vibrational velocity measurements; computing a drive point mobility of said sample over said preselected range of frequencies, said drive point mobility derived from said pluralities of vibrational force and velocity measurements; computing a damping loss factor of said sample from said drive point mobility; and comparing said damping loss factor of said sample with a reference damping loss factor for said material to determine whether said sample behaves differently than said reference material. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for evaluating the structural integrity of a sample of a material by the sample'"'"'s damping loss factor, said sample having a resonant frequency, said method comprising the steps of:
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providing a sample supported along a node of said sample; vibrating said sample over a preselected range of frequencies including said resonant frequency by applying vibrational force at a point remote from said support and sufficient to vibrate said sample at each frequency in said range of frequencies; measuring vibrational force as a function of time of said sample over said preselected range of frequencies to generate a plurality of vibrational force measurements; transforming said plurality of vibrational force measurements from said function of time to a function of frequency; measuring the vibrational velocity as a function of time of said sample over said preselected range of frequencies to generate a plurality of vibrational velocity measurements; transforming said plurality of vibrational velocity measurements from said function of time to a function of frequency; computing a ratio of said transformed vibrational force measurements to said transformed vibrational velocity measurements; computing a damping loss factor of said sample from said ratio, and comparing said damping loss factor of said sample to a reference damping loss factor of a said material. - View Dependent Claims (11, 12, 13, 14, 15)
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16. Apparatus for evaluating the structural integrity of a sample of a material including a weld by the sample'"'"'s damping loss factor, said sample having a resonant frequency, said apparatus comprising:
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means for positioning said sample in an essentially vibration-free manner along a node of said sample; means for vibrating said sample over a preselected range of frequencies including said resonant frequency by applying a vibrational force to said sample; means responsive to said vibrating means for measuring said vibrational force applied to said sample by said vibrating means, said vibrational force measuring means generating a plurality of vibrational force measurements as a function of time; means responsive to said vibrating sample for measuring a vibrational velocity of said sample, said vibrational velocity measuring means generating a plurality of vibrational velocity measurement as a function of time; means operably connected to said vibrational force measuring means and said vibrational velocity measuring means for calculating a damping loss factor of said sample from said plurality of vibrational force and velocity measurements and comparing said damping loss factor of said sample to a reference damping loss factor of said material to indicate structural integrity of said sample. - View Dependent Claims (17, 18, 19, 20)
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Specification