Apparatus and method for damage detection

A method for detecting damage in a structure, comprising the steps of:

• applying a first excitation force to the structure;
• measuring with a transducer a pre-damage vibration frequency response of the structure in response to said first excitation force;
• converting said pre-damage frequency response to first data indicative of pre-damage modal parameters of the structure, said pre-damage modal parameters including at least one measured mode shape;
• applying a second excitation force to the structure;
• measuring with said transducer a post-damage vibration frequency response of the structure in response to said second excitation force;
• converting said post-damage frequency response to second data indicative of post-damage modal parameters of the structure, said post-damage modal parameters including at least one measured mode shape;
• and
• identifying at least one location of the damage based upon said first and second data.

A method for detecting damage in a structure, comprising the steps of:

• applying a first excitation force to the structure;
• measuring with a transducer a first signal set in response to said first excitation force;
• converting said first signal set to first data indicative of pre-damage modal parameters of the structure, said pre-damage modal parameters including at least one measure mode shape;
• applying a second excitation force to the structure;
• measuring with said transducer a second signal set in response to said second excitation force from the structure;
• converting said second signal set to second data indicative of post-damage modal parameters of the structure, said post-damage modal parameters including at least one measured mode shape;
• identifying at least one location of the damage based upon said first and second data;
• and
• determining a magnitude of the damage at each said location based upon each said identified location and upon said first and second data.

A method for detecting damage in a structure, comprising the steps of:

• applying a first excitation force to the structure;
• acquiring with a transducer a pre-damage vibration frequency response for the structure in response to said first excitation force;
• converting said pre-damage frequency response to first data indicative of said pre-damage vibration frequency response of the structure;
• applying a second excitation force to the structure;
• acquiring with said transducer a post-damage vibration frequency response for the structure as damaged in response to said second excitation force;
• converting said pre-damage frequency response to second data indicative of said post-damage vibration frequency response;
• generating a stiffness matrix fo the structure based on one or more material and geometric properties of the structure;
• from the pre-damage and post-damage frequency response data, extracting a plurality of N.times.1 matrices of modal parameters for one or more vibrational modes, the parameters including fractional changes in damped eigenvalue frequencies Z.sub.d, fractional changes in modal masses Z.sub.m, fractional changes in modal damping ratios Z.sub.damp, and fractional changes in the norm of mode shapes Z.sub.modes, N being selected as a number of said vibrational modes;
• using the stiffness matrix and the pre-damage frequency response data, computing an N.times.B pre-damage sensitivity matrix F.sub.0 which relates changes in said modal parameters to a fractional change in stiffness of one or more elements of the structure, B being selected as a number of said elements;
• using the stiffness matrix and the post-damage frequency response data computing an N.times.B sensitivity change matrix .DELTA.F, which accounts for changes in the sensitivity matrix F.sub.0 resulting from damage to the structure;
• and
• using a damage detection equation:
• Z.sub.d +Z.sub.m +Z.sub.damp +Z.sub.modes =(F.sub.0 +.DELTA.F).alpha.
• solving for .alpha., a B.times.1 matrix containing the fractional change in stiffness of each said element.

Apparatus for detecting damage in a structure, comprising:

• an exciter operable to provide an excitation force to the structure;
• a transducer operable to measure a first signal set indicative of pre-damage modal parameters of the structure in response to a first excitation force, said transducer further operable to determine a second signal set indicative of post-damage modal parameters of the structure in response to a second excitation force;
• a converter operable to convert said first signal set to first data indicative of pre-damage modal parameters of the structure, said pre-damage modal parameters including at least one measured mode shape, said converter further operable to convert said second signal set to second data indicative of post-damage modal parameters of the structure, said post-damage modal parameters including at least one measured mode shape;
• and
• means coupled to said converter operable to identify at least one location of the damage based upon said first and second data applied to an indicator function.

Apparatus for detecting damage in a structure, comprising:

• an exciter operable to provide an excitation force to the structure;
• a transducer coupled to the structure operable to measure a pre-damage vibration frequency response of the structure in response to a first excitation force, said transducer further operable to measure a post-damage vibration frequency response of the structure in response to a second excitation force;
• a converter operable to convert said pre-damage vibration frequency response to a first data indicative of pre-damage modal parameters of the structure, said pre-damage modal parameters including at least one measured mode shape, said converter further operable to convert said post-damage vibration frequency response to second data indicative of post-damage modal parameters of the structure, said post-damage modal parameters including at least one measured mode shape;
• and
• means coupled to said converter for identifying at least one location of the damage based upon said first and second data.

Apparatus for detecting damage in a structure, comprising:

• an exciter operable to provide an excitation force to the structure;
• a transducer operable to measure a first signal set in response to a first excitation force, said transducer further operable to measure a second signal set in response to a second excitation force;
• a converter operable to convert said first signal set to first data indicative of pre-damage modal parameters of the structure, said pre-damage modal parameters including at least one measured mode shape, said converter further operable to convert said second signal;
• set to second data indicative of post-damage modal parameters of the structure, said post-damage modal parameters including at least one measured mode shape;
• means coupled to said converter for identifying at least one location of the damage based upon said first and second data;
• and
• means coupled to said location identifying means for determining a magnitude of the damage at each said location based upon each said identified location and upon said first and second data.

Apparatus for detecting damage in a structure, comprising:

• an exciter operable to provide an excitation force to the structure;
• a transducer coupled to the structure operable to acquire a pre-damage vibration frequency response for the structure;
• in response to a first excitation force, said transducer further operable to determine a post-damage vibration frequency response for the structure as damaged;
• a converter operable to convert said pre-damage vibration frequency response to first data indicative of pre-damage modal parameters of the structure, said converter further operable to convert said post-damage vibration frequency response to second data indicative of post-damage modal parameters of the structure;
• means for generating a stiffness matrix of the structure based on one or more material and geometric properties of the structure;
• means coupled to said converter for extracting from the pre-damage and post-damage frequency response data a plurality of N.times.1 matrices of modal parameters for one or more vibrational modes, the parameters including fractional changes in damped eigenvalue frequencies Z.sub.d, fractional changes in modal masses Z.sub.m, fractional changes in modal damping ratios Z.sub.damp, and fractional changes in the norm of mode shapes Z.sub.modes, N being selected as a number of said vibrational modes;
• means coupled to said stiffness matrix generating means and to said converter for computing an N.times.B pre-damage sensitivity matrix F.sub.0 using the stiffness matrix and the pre-damage frequency response data, wherein said sensitivity matrix relates changes in said modal parameters to a fractional change in stiffness of one or more elements of the structure, B being selected as a number of said elements;
• means coupled to said stiffness matrix generating means and to said converter for computing an N.times.B sensitivity change matrix .DELTA.F using the stiffness matrix and the post-damage frequency response data, wherein said sensitivity change matrix accounts for changes in the sensitivity matrix F.sub.0 resulting from damage to the structure;
• and
• means coupled to said extracting means, to said sensitivity matrix computing means and to said sensitivity change matrix computing means for using a damage detection equation:
• Z.sub.d +Z.sub.m +Z.sub.damp +Z.sub.modes =(F.sub.0 +.DELTA.F).alpha.
• to solve for .alpha., a B.times.1 matrix containing the fractional change in stiffness of each said element.