US 4,331,026 A · Indenter-type hardness testing apparatus

Abstract

A material hardness testing apparatus is provided, for use in quality control of production materials and parts, in which a pneumatically actuated indenter probe, incorporating an LVDT displacement transducer, is coupled by an analog-to-digital converter to a microprocessor-based computer that controls the cyclic actuation of the indentor probe, and processes indenter measurement data received from the LVDT transducer. The pneumatically actuated indenter probe includes pneumatic control means for providing independently adjustable control over the rates of probe impact and retraction in order to achieve consistent hardness measurements from cycle to cycle, together with relatively rapid displacement cycling of the indenter probe. The microprocessor-based computer incorporates a recalibration processor which automatically causes the testing apparatus to branch into a recalibration routine after a predetermined period of operation. During such recalibration, the apparatus semi-automatically tests and compares the measured hardness of one or more reference specimens with hardness values stored in memory and either disables the testing apparatus when the measured hardness deviates from the standard by a predetermined percentage amount, or stores in memory the difference between the measured hardness and the standard and enables the apparatus to continue with further testing. In each succeeding test, the apparatus automatically subtracts or adds the magnitude of the memorized difference to the raw measured hardness value to correct the hardness reading displayed by the apparatus.

Claims18

Dependent claims

In a hardness testing apparatus of the type having an indenter probe and a probe actuator for controllably moving said probe into and out of contact with a test part to thereby cause said probe to deformably penetrate the test part, and having sensing transducer means for producing an electrical signal representing the degree of such penetration as a measure of the hardness of the test part, the improvement in signal processing circuitry of such hardness testing apparatus comprising:

reset means;
indicator means responsive to said reset means for indicating a calibration mode;
and,
calibration processor means responsive to actuation of said probe by said actuator, said calibration processor means comprising:
calibration measuring processor means for developing a signal measurement representing the measured hardness of a calibrating material when such a calibrating material is contacted by said probe;
difference taking processor means for taking the difference between said measurement signal and a stored hardness signal representing the known hardness of said calibrating material, and for developing a calibration error signal in response thereto;
comparison processor means for comparing said error signal with a predetermined threshold;
automatic error correcting processor means responsive to said comparison means when said error signal is less than said predetermined threshold for storing said error signal for automatically correcting subsequent hardness measurements of parts of unknown hardness;
and,
recalibration disablement processor means responsive to said comparison processor means when said error signal is greater than said predetermined threshold for disabling said apparatus from further testing, said disablement processor means including means for reenabling said apparatus in response to said reset means.

7 more elements

A hardness testing apparatus comprising:

an indenter probe means;
a probe actuator means for controllably moving said probe means into and out of contact with a test part to thereby cause said probe means to deformably penetrate the test part;
sensing transducer means for producing an electrical signal representing the degree of such penetration by said probe means as a measure of the hardness of the test part;
hardness testing processor means responsive to said probe actuator means and said sensing transducer means for developing a measurement signal representing the hardness of a test part;
manually operated reset means;
p1 calibration processor means responsive to said reset means and to said probe actuator means and to said sensing transducer means, said calibration processor means comprising:
calibration measuring processor means for developing a calibration measurement signal representing the measured hrdness of a calibrating material when such a calibrating material is contacted by said probe means;
difference taking processor means for taking the difference between said calibration measurement signal and a stored hardness signal representing the known hardness of said calibrating material, and for developing a calibration error signal in response thereto;
comparison processor means for comparing said error signal with a predetermined threshold;
automatic error correcting processor means responsive to said comparison processor means, said automatic error correcting processor means storing said error signal for automatically correcting subsequent hardness measurements by said hardness testing processor means when said error signal is less than said predetermined threshold;
and,
disablement processor means responsive to said comparison processor means for disabling said hardness testing processor means when said error signal is greater than said predetermined threshold.

9 more elements

Dependencies are inferred from the claim text.

Indenter-type hardness testing apparatus

Life of this patent

Indenter-type hardness testing apparatus

Life of this patent

Abstract

Claims18