Photoelastimetric apparatus for stress analysis

Claim 1

PHOLOELASTIMETRIC APPARATUS FOR THE INVESTIGATION OF PRINCIPAL PLANE STRESSES ACTING LATERALLY WITHIN A REGION OF A SHEET OF TRANSPARENT BIREFRINGENT MATERIAL CONTIGUOUS WITH A REFLECTING SURFACE, SAID APPARATUS COMPRISING: A MOUNT RELATIVELY ROTATABLE ABOUT AN AXIS THROUGH SAID REGION AND, SUPPORTED ON SAID MOUNT, A UNITARY LIGHT SOURCE, A SHEET MATERIAL POLARIZER, A SHEET MATERIAL ANALYZER, AN AXIALLY ELONGATED POINTER, AND FIRST AND SECOND PLANE MIRRORS; SAID POLARIZER AND SAID ANALYZER BEING COPLANAR AND SYMMETRICALLY DISPLACED TO OPPOSITE SIDES OF SAID AXIS AT ONE END THEREOF; SAID POINTER BEING LOCATED AT THE OTHER END OF SAID AXIS AND ORIENTED COAXIALLY WITH RESPECT THERETO; SAID FIRST AND SECOND MIRRORS BEING LOCATED INTERMEDIATE SAID ENDS OF SAID AXIS, SYMMETRICALLY DISPLACED TO OPPOSITE SIDES THEREOF, AND EQUIANGULARLY DISPOSED WITH RESPECT THERETO; SAID SOURCE BEING LOCATED BEHIND SAID POLARIZER AND ILLUMINATING SAID FIRST MIRROR AND SAID POINTER; AND SAID SOURCE, POLARIZER, FIRST AND SECOND MIRRORS, AND ANALYZER BEING FURTHER RELATIVELY ORIENTED WITH RESPECT TO SAID AXIS AND TO SAID POINTER TO SIMULTANEOUSLY DEFINE FIRST AND SECOND COPLANAR LIGHT PATHS THROUGH THE REGION WHEN SAID APPARATUS IS IN A POSITION WITH SAID POINTER CONTIGUOUS WITH THE REGION AND SAID AXIS PERPENDICULAR TO THE PLANE OF THE PRINCIPAL STRESSES; SAID FIRST LIGHT PATH EXTENDING FROM SAID SOURCE, THROUGH SAID POLARIZER, THROUGH THE REGION, TO THE REFLECTING SURFACE, BACK THROUGH THE REGION, AND THROUGH SAID ANALYZER, WHEN SAID APPARATUS IS IN SAID POSITION; SAID SECOND LIGHT PATH EXTENDING FROM SAID SOURCE, THROUGH SAID POLARIZER, TO SAID FIRST MIRROR, THROUGH THE REGION, TO THE REFLECTING SURFACE, BACK THROUGH THE REGION, TO SAID SECOND MIRROR, AND THROUGH SAID ANALYZER, WHEN SAID APPARATUS IS IN SAID POSITION; THE PORTION OF SAID FIRST LIGHT PATH WITHIN THE REGION BEING SUBSTANTIALLY NORMAL TO THE PLANE OF THE PRINCIPAL STRESSES WHEN SAID APPARATUS IS IN SAID POSITION; AND THE PORTION OF SAID SECOND LIGHT PATH WITHIN THE REGION BEING AT A SUBSTANTIAL OBLIQUE ANGLE WITH THE NORMAL TO THE PRINCIPAL STRESSES ACTING WITHIN THE REGION WHEN WHEREBY UPON RELATIVE ROTATION OF SAID APPARATUS IN SAID POSITION ABOUT SAID AXIS, THE PLANE OF SAID COPLANAR LIGHT PATHS MAY BE ORIENTED PARALLEL WITH ONE AND THE OTHER OF THE PRINCIPAL STRESSES ACTING LATERALLY OF THE REGION TO YIELD PHOTOELASTIC FRINGE INFORMATION FOR THE IMMEDIATE RESOLUTION OF THE INDIVIDUAL MAGNITUDES OF THE PRINCIPAL STRESSES.