Methods and instruments for material testing

Abstract

Methods and instruments for characterizing a material, such as the properties of bone in a living human subject, using a test probe constructed for insertion into the material and a reference probe aligned with the test probe in a housing. The housing is hand held or placed so that the reference probe contacts the surface of the material under pressure applied either by hand or by the weight of the housing. The test probe is inserted into the material to indent the material while maintaining the reference probe substantially under the hand pressure or weight of the housing allowing evaluation of a property of the material related to indentation of the material by the probe. Force can be generated by a voice coil in a magnet structure to the end of which the test probe is connected and supported in the magnet structure by a flexure, opposing flexures, a linear translation stage, or a linear bearing. Optionally, a measurement unit containing the test probe and reference probe is connected to a base unit with a wireless connection, allowing in the field material testing.

1 - 44 . (canceled) 
     
     
         45 . An instrument for characterizing a material, comprising:
 a housing;   a three footed reference probe aligned with the housing, wherein the three feet form a tripod base for resting the instrument on a surface and the plane of the tripod forms a reference plane;   a test probe aligned within the reference probe;   a force generator; and;   a force sensor operatively coupled to the test probe for determining a force vs distance parameter by measuring the force needed to insert the test probe a predetermined distance or as a function of distance into the material relative to the reference plane formed by the tripod; wherein the test probe applies a force on the material of at least several Newtons.   
     
     
         46 . The instrument of  claim 45 , wherein the tripod base is located on a circle having a diameter of about 1.5 inches. 
     
     
         47 . The instrument of  claim 45 , further comprising a distance sensor. 
     
     
         48 . The instrument of  claim 45 , wherein the tripod feet are adjustable and contain permanent magnets. 
     
     
         49 . The instrument of  claim 45 , wherein the tripod feet are rounded. 
     
     
         50 . The instrument of  claim 45 , wherein the tripod feet are pointed. 
     
     
         51 . The instrument of  claim 45 , wherein the test probe is coaxially aligned within the reference probe and is not cantilevered.