Strain measurement method and device

A strain measurement system for measuring the Poisson's ratio of a test piece in real time while applying a tensile force on said test piece comprising:

• a laser light source for directing a beam of energy onto a surface of a test piece for generating a spectral pattern;
• at least one video camera positioned for viewing the changes in said spectral pattern as a tensile force is applied to said test piece;
• a tracking system for said video camera such that said camera views the same area of said test piece during the application of the tensile force;
• an image processor coupled to said video camera;
• and
• a data processor coupled to said image processor and programmed to determine the Poisson's ratio in real time as said test piece is placed under a tensile force.

A strain measurement method for measuring the Poisson's ratio of a test piece in real time without contacting said test piece comprising:

• generating a spectral pattern in front of a test piece by irradiating a test piece perpendicularly with a laser beam from a laser projector;
• positioning two CCD cameras with respect to said test piece, each at an equidistance from a perpendicular position respectively in front of said test piece and toward said test piece;
• positioning an additional two CCD cameras each at an equidistance from a horizontal position respectively in front of said test piece and toward said test piece, wherein the two CCD cameras at the perpendicular position calculate a change (vertical strain) in spectral pattern movement in real time and, at the same time, the two additional CCD cameras at the horizontal position calculate a change (horizontal strain) in spectral pattern movement in real time;
• and
• inputting the vertical strain and the horizontal strain information into a data processing device where the Poisson's ratio is measured by dividing the horizontal strain by the vertical strain without contacting said test piece.

A strain measurement device for measuring a Poisson's ratio of a test piece in real time without contacting the test piece comprising:

• a laser projector positioned in front of the test piece, such that a laser beam outputted from said laser projector is irradiated perpendicular to said test piece to provide a spectral pattern in front of said test piece by diffused reflection of said laser beam light by said test piece;
• two CCD cameras positioned with respect to said test piece, each at an equidistance from a perpendicular position respectively in front of said test piece and toward the test piece;
• two additional CCD cameras positioned with respect to said test piece, each at an equidistance from a horizontal position respectively in front of said test piece and toward said test piece;
• wherein said two COD cameras at the perpendicular position are provided at a tracking mechanism for tracking the vertical movement of said test piece and calculate a change (vertical strain) in spectral pattern movement in real time, and, at the same time, the two additional CCD cameras at the horizontal position calculate a change (horizontal strain) in spectral pattern movement in real time;
• and
• a data processing device coupled to said CCD camera to receive the calculated vertical strain and horizontal strain, whereby the Poisson's ratio is measured by dividing the horizontal strain by the vertical strain without contacting said test piece.