Material testing device for the continuous measurement of stress relaxation

Claim 3

A material testing device for measuring stress relaxation comprising, first rotatable means having first securing means for rigidly affixing an extremity of a material test specimen, said rotatable means being coupled to stationary housing means, second rotatable means having second securing means for rigidly affixing a second extremity of said material test specimen, said second rotatable means being disposed within said stationary housing means, air venting means for maintaining said second rotatable means suspended on an air bearing, free to rotate about the vertical axis of said second rotatable means, first torquing means for applying a torque to said second rotatable means proportional to a torque applied to said first rotatable means providing rotational displacement of said test specimen, second torquing means responsive to an error signal for applying a torque to maintain said second rotatable means at a null position, sensing means for detecting displacement of said second rotatable means relative to said null position and generating said error signal which is proportional to the magnitude of said displacement, said error signal being indicative of said material stress relaxation in said test specimen, and display means responsive to said error signal for continuous display of said stress relaxation.

Claim 4

A material testing device for measuring stress relaxation comprising, first rotatable means having first securing means for rigidly affixing an extremity of a material test specimen, said rotatable means being coupled to stationary housing means, second rotatable means having second securing means for rigidly affixing a second extremity of said material test specimen, said second rotatable means being disposed within said stationary housing means, air venting means for maintaining said second rotatable means suspended on an air bearing, free to rotate about the vertical axis of said second rotatable means, first torquing means for applying a torque to said second rotatable means proportional to a torque applied to said first rotatable means providing rotational displacement of said test specimen, second torquing means responsive to an error signal for applying a torque to maintain said second rotatable means at a null position, sensing means for detecting displacement of said second rotatable means relative to said null position and generating said error signal which is proportional to the magnitude of said displacement, said error signal being indicative of said material stress relaxation in said test specimen, and display means responsive to said error signal for continuous display of said stress relaxation.

Claim 5

A material testing device comprising, cylindrical stationary housing means having a removable base, an access port in its head and an inner chamber, calibrated rotatable plate means coupled to said stationary housing means having securing means for rigidly affixing one end of a material test specimen and providing rotatable displacement of said material test specimen, cylindrical air manifold means mounted on said removable base within said inner chamber having an air inlet vent extending through said removable base and a plurality of air outlet vents in the head and wall of said air manifold, cylindrical rotatable means with an open base incasing said air manifold and free to rotate about its vertical axis when suspended on a cushion of air vented through said plurality of air outlet vents, having securing means for affixing a second end of said material test specimen, an electromagnetic spring field for applying a torque proportional to said displacement of said material test specimen, electronic sensing means having an adjustable null position for detecting displacement of said cylindrical rotatable means from a null position, preamplifier means connected to said sensing means for amplifying said error signal, demodulator means responsive to said amplified error signal for removing the carrier frequency from said error signal, power amplifier means for amplifying said demodulated error signal, providing an amplified error signal, torque motor means responsive to said amplified error signal for returning said rotatable means to its null position, load resistor means for developing a voltage proportional to said amplified error signal, suppression circuit means including constant current source means for developing a threshold signal, summing amplifier means coupled to said suppression circuit means and said load resistor means for producing a difference signal equivalent to the difference between said threshold signal level and said load resistor voltage, and display recorder means for providing a recorded display of said difference signal which is indicative of the stress relaxation in the material test specimen.

Claim 6

A material testing device comprising, cylindrical stationary housing means having a removable base, an access port in its head and an inner chamber, calibrated rotatable plate means coupled to said stationary housing means having securing means for rigidly affixing one end of a material test specimen and providing rotatable displacement of said material test specimen, cylindrical air manifold means mounted on said removable base within said inner chamber having an air inlet vent extending through said removable base and a plurality of air outlet vents in the head and wall of said air manifold, cylindrical rotatable means with an open base incasing said air manifold and free to rotate about its vertical axis when suspended on a cushion of air vented through said plurality of air outlet vents, having securing means for affixing a second end of said material test specimen, an electromagnetic spring field for applying a torque proportional to said displacement of said material test specimen, electronic sensing means having an adjustable null position for detecting displacement of said cylindrical rotatable means from a null position, preamplifier means connected to said sensing means for amplifying said error signal, demodulator means responsive to said amplified error signal for removing the carrier frequency from said error signal, power amplifier means for amplifying said demodulated error signal, providing an amplified error signal, torque motor means responsive to said amplified error signal for returning said rotatable means to its null position, load resistor means for developing a voltage proportional to said amplified error signal, suppression circuit means including constant current source means for developing a threshold signal, summing amplifier means coupled to said suppression circuit means and said load resistor means for producing a difference signal equivalent to the difference between said threshold signal level and said load resistor voltage, and display recorder means for providing a recorded display of said difference signal which is indicative of the stress relaxation in the material test specimen.