Mts Systems Corporation

Harry R Meline

Richard Alan Meyer

Eric L Paulsen

Scott P Iverslie

Nebojsa D Kovacevic

An extensometer for measuring strain in a specimen on which the extensometer is mounted which has two arms joined together at first ends, and with specimen engaging knife edges at the second ends. The knife edges will engage a specimen at spaced locations, so that when the specimen is subjected to a load, the knife edges will separate, and the amount of separation will be an indication of the strain in the specimen. The distance between the knife edges is known as the 'gage length' and the present invention relates to providing for mounting the knife edge contact points in a selected plurality of positions in which the gage length of the extensometer is changed from other of the positions of the knife edges.

Multiple gage length extensometer

A capacitive extensometer has an extensometer frame formed of a pair of arms having first ends with specimen contacting members and which are connected together about a hinge axis at second remote ends. The specimen contacting members engage the surfaces of a specimen to be tested. A capacitive type sensing arrangement is mounted on the arms, and is used with conventional circuitry for determining arm motion. The sensing members are located to insure adequate output, and can be located to the exterior of the periphery of the extensometer arm assembly. The ability to mount the capacitor sensor appropriately, while obtaining a relatively large output signal enhances the operability of the extensometer.

Pivoted arm capacitive extensometer

A high temperature extensometer system carries specimen contact rods of substantial length which pass through openings in a furnace to engage a specimen in such furnace. The rods are supported at the exterior of the furnace on a paralleogram linkage support frame made to provide an output indicating specimen strain as the contact rods separate and also made with parallel beams which shift so the rods can move differentially in longitudinally axial direction. The rods shift axially when the specimen and test loading grips shift in position, for example when the grips and specimen are initially heated.

High temperature extensometer system

An extensometer support system having vibration damping mountings for parts that have substantial mass and which are subjected to external vibrations. Such parts include counterweights for counterbalancing the extensometer and also the mounting for an external support frame for the extensometer. The vibration damping comprises a mounting made of a suitable damping material, such as a silicone foam rubber.

Vibration damped mounting for extensometer system

A capacitive extensometer has an extensometer frame formed of a pair of arms connected together about a hinge axis at first remote ends, and having second ends which include specimen contacting members for engaging the surfaces of a specimen to be tested. A capacitive type sensing arrangement is mounted on the arms, and is used with conventional circuitry for determining arm motion. The sensing is made so that it can be compensated for nonlinearities and minimizes undesirable extraneous effects by utilizing concave and convex shaped mating surfaces on the sensing elements. The ability to mount and protect the capacitor sensor approximately, while obtaining a relatively large output signal enhances the operability of the extensometer.

Capacitive extensometer with curved target surface

A capacitive extensometer utilizes an extensometer frame having a pair of arms connected together about a hinge axis at first remote ends, and having second ends which include specimen contacting members for engaging the surfaces of a specimen to be tested. A capacitive type sensing arrangement is mounted on the arms, and is used with conventional circuitry for determining arm motion with respect to each other. The sensor is made so that it can be adjusted, and also can compensate for nonlinearities by utilizing differently shaped elements. The ability to mount and protect the capacitor sensor appropriately, while obtaining a relatively large output signal enhances the operability of the extensometer.

Capacitive extensometer

A self-supporting extensometer for use with rectilinear specimens has one arm that contacts a specimen edge on two points that are spaced apart in a longitudinal direction of the specimen, and a second arm which engages an opposite edge of the specimen at a single substantially point contact under a spring load urging the arms together. The specimen contact arms are notched to receive edges of the rectilinear specimen. The second specimen contact arm has single point contact and has a curved surface which engages a side edge of the specimen so that contact with the specimen is at a point. The support assembly includes a releasable hold-down or clamp spring that bears on the surface of the specimen opposite from the extensometer to clamp the extensometer in place. The spring loading of the extensometer arms and the hold-down spring supports the weight of the extensometer directly on the specimen.

Self-supporting extensometer for recilinear specimens

An extensometer assembly measures axial strain, torsional strain, and various combinations of these strains in a specimen on which the extensometer is mounted, through the use of two extensometers on opposite sides of the specimen coupled by a cross-beam. Connecting assemblies are used to eliminate flexibility in unneeded axes to thereby minimize the opportunities for unwanted signals to occur. The mounting frame is stiff in all axes which are not necessary for measurement. The frame is soft in necessary axes for operation.

Torsional-axial extensometer with additional restraint to limit

A support system provides a stable reference frame to support an extensometer assembly that measures both axial and torsional strains in a specimen. The reference frame is made so that it will retain an optimal relationship between the specimen and the test machine which is used for loading the specimen. The reference frame is made so that it will not substantially change position in relationship to the specimen during the specimen loading, or cross talk from one measurement axis to the other, while accommodating load frame deflections during the application of axial and torsional loads on the specimen.

Reference frame and hold-down support system for remote supported axial

An extensometer is used for measuring axial and diametral strains in a material test specimen. The extensometer comprises an assembly of extensometer sections positioned on diametrally opposite sides of the specimen with specimen engaging points spaced axially along the specimen. The extensometer assembly is arranged so that the two extensometer sections will average the axial strain measured by the two extensometer sections. Also, if desired, the two extensometer sections may provide an indication of the average change in diameter of the specimen at the location of the upper contact points and at the location of the lower contact points of the extensometer sections on opposite sides of the specimen. The support system between the extensometer sections provides for the necessary degrees of freedom to provide measuring only in the axis desired, and sufficient restraint in other axes to insure that accurate measurements are obtained.

Averaging axial-diametral strain measuring extensometer

A strain gage element system includes a spring flexure member on which strain gages of convention design are mounted, and a heat shrinkable waterproof tube that is placed over the gage and the support and shrunk into place. The spring flexure member is formed so that it has a substantially constant peripheral length about the perimeter of any cross-sectional plane perpendicular to the longitudinal axis of the spring flexure member. The heat shrinkable tube must be selected in size and shrinkage characteristics to tightly envelope and shrink against the gage and spring flexure member and seal the gage completely to prevent moisture of any kind from getting into contact with the gage.

Waterproof strain gage element system

A quick attach spring retainer holds an extensometer arm onto a test specimen under a resilient load using a unitary spring that is quickly placed onto an extensometer, and which has low mass to minimize any effects on dynamic testing. The spring force is reacted so that it creates a very low disturbing moment on the specimen and extensometer in that this clamping force is applied directly diametrically across from the specimen engaging edge of the extensometer. The unit is made so that it is very stable by providing a three point contact with the spring and the specimen engaging edge. The attachment clip or spring is adjustable across a range of different specimen sizes, using the same type of fixtures, and is made to be a self contained assembly that is not easily lost or misplaced because there are no loose parts. The spring that is utilized is retained in a mounting bracket that is used for attachment.

Quick attach retainer for extensometer

An extensometer assembly accurately measures axial strain, torsional strain and various combinations of these strains in a specimen on which the extensometer assembly is mounted. The torsional strain measurement is made by measuring angular displacement perpendicular to the longitudinal axis of the specimen with one extensometer at the same time separately measuring the elongation of the specimen with a separate extensometer linked to the torsional measuring extensometer by supports having the necessary degrees of freedom so that readings from the respective extensometers are not subjected to excessive 'cross talk', and at the same time torsional movement between the extensometers about an axis perpendicular to the longitudinal axis of the specimen is resisted.

Axial-torsional extensometer

A support for use with diametral and other types of extensometers to support the weight of the extensometer and also permit the extensometer to move with the specimen in its translational axes without substantial restraint, that is, up, down and in all directions sideways. At the same time the support provides restraint or stiffness in all three axes of rotation of the extensometer.

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Minnetonka, MN, United States of America

Harry R Meline