Ultrasonic non-destructive evaluation of thin specimens

A method for non-destructively evaluating a material, comprising the steps of:

• transmitting an ultrasonic wave having a frequency within a preselected frequency range into said material;
• receiving said ultrasonic wave from said material;
• measuring a frequency response of said material at frequencies within said preselected frequency range from said received ultrasonic wave;
• and
• equating said measured frequency response to a preselected frequency-dependent function of said material to determine an unknown parameter of said material.

An apparatus for evaluating a material, comprising:

• a generator being adapted to deliver an electrical pulse having a predetermined duration;
• a transducer being operably connected to said generator to receive said electrical pulse, said transducer converting said electrical pulse into an ultrasonic acoustical wave correlative to said electrical pulse;
• said transducer being positioned to direct said ultrasonic acoustical wave toward said material and to detect ultrasonic acoustical waves reflected from said material, and said transducer converting said reflected acoustical waves into an electronic signal correlative to said reflected acoustical waves;
• and
• a computer being operably connected to said transducer to receive said electronic signal, said computer being programmed to determine a frequency response of said material in response to said electronic signal, and to determine a frequency-dependent normalized wavenumber in said material from said frequency response.

A method for evaluating a material having a known thickness, comprising the steps of:

• imparting an ultrasonic wave into said material;
• receiving the ultrasonic wave from said material;
• determining the frequency response of said material within a predetermined frequency range from said received ultrasonic wave;
• calculating the attenuation of said material for ultrasonic waves having a frequency within said predetermined frequency range;
• and
• calculating the speed with which ultrasonic waves having a frequency within said predetermined frequency range propagate through said material.

A method for evaluating a material having a known attenuation and through which speed of an ultrasonic wave is known, comprising the steps of:

• imparting an ultrasonic wave into said material;
• receiving the ultrasonic wave from said material;
• determining the frequency response of said material within a predetermined frequency range from said received ultrasonic wave;
• and
• calculating the thickness of said material in response to said determined frequency response.

A method for non-destructively evaluating a material using at least one transducer being adapted to emit ultrasonic waves, comprising the steps of:

• determining the frequency response of said transducer;
• transmitting an ultrasonic wave having a frequency within a predetermined frequency range into said material;
• receiving said ultrasonic wave from said material;
• determining the frequency response of said received ultrasonic wave;
• dividing the frequency response of said received ultrasonic wave by the frequency response of said transducer, said division producing the frequency response of said material;
• and
• determining phase and magnitude of the frequency response of said material, phase velocity of said ultrasonic wave within said material being correlative to the phase and attenuation of said material being correlative to the magnitude.

A method for non-destructively evaluating a thin material, comprising the steps of:

• delivering a first ultrasonic signal from a first transducer;
• receiving said first ultrasonic signal by a second transducer;
• calculating the Fourier Transform of said received first ultrasonic signal;
• acoustically coupling said thin material between said first transducer and said second transducer;
• delivering a second ultrasonic signal from said first transducer to said thin material;
• receiving a portion of said second ultrasonic signal transmitted through said thin material by said second transducer;
• calculating the Fourier Transform of said received portion;
• dividing the Fourier Transform of said received portion by the Fourier Transform of said received first ultrasonic signal, said division producing a measured transfer function;
• equating said measured transfer function to a preselected transfer function corresponding to said thin material, said preselected transfer function having at least one unknown variable, said unknown variable being related to said thin material;
• and
• solving for said unknown variable.

A method for non-destructively determining the unknown thickness of a thin material, comprising the steps of:

• delivering a first ultrasonic signal from a first transducer;
• receiving said first ultrasonic signal by a second transducer;
• calculating the Fourier Transform of said received first ultrasonic signal;
• acoustically coupling said thin material between said first transducer and said second transducer;
• delivering a second ultrasonic signal from said first transducer to said thin material;
• receiving a portion of said second ultrasonic signal transmitted through said thin material by said second transducer;
• calculating the Fourier Transform of said received portion;
• dividing the Fourier Transform of said received portion by the Fourier Transform of said received first ultrasonic signal, said division producing a measured transfer function;
• equating said measured transfer function to a preselected transfer function corresponding to said thin material, said preselected transfer function including the unknown thickness of said thin material;
• and
• solving said equation for the unknown thickness.

A method for non-destructively determining speed and attenuation of an ultrasonic wave in a material of known thickness, comprising the steps of:

• delivering a first ultrasonic wave from a first transducer;
• receiving said first ultrasonic wave by a second transducer;
• calculating the Fourier Transform of said received first ultrasonic wave;
• acoustically coupling said material between said first transducer and said second transducer;
• delivering a second ultrasonic wave from said first transducer to said material;
• receiving a portion of said second ultrasonic wave transmitted through said material by said second transducer;
• calculating the Fourier Transform of said received portion;
• dividing the Fourier Transform of said received portion by the Fourier Transform of said received first ultrasonic wave, said division producing a measured transfer function;
• and
• determining phase and magnitude of said measured transfer function, the speed of said ultrasonic wave within said material being correlative to the phase and the attenuation of said material being correlative to the magnitude.

A method for non-destructively evaluating a thin material, comprising the steps of:

• acoustically coupling an ultrasonic transducer to a reference material;
• delivering a first ultrasonic signal from said transducer to said reference material, said transducer receiving a portion of said first ultrasonic signal reflected from said reference material;
• calculating the Fourier Transform of said received first ultrasonic signal;
• acoustically coupling said thin material to said transducer;
• delivering a second ultrasonic signal from said transducer to said thin material;
• receiving a portion of said second ultrasonic signal reflected from said thin material by said transducer;
• calculating the Fourier Transform of said received second ultrasonic signal;
• dividing the Fourier Transform of said received second ultrasonic signal by the Fourier Transform of said received first ultrasonic signal, said division producing a measured transfer function;
• equating said measured transfer function to a preselected transfer function having known parameters of said thin material, said preselected transfer function having at least one unknown parameter, said unknown parameter being related to said thin material;
• and
• solving for said unknown parameter.