Patent Description:
Test specimen holders or grips are well known in the material testing art and are used frequently to hold a test specimen in a material testing system. The holder includes opposed jaws or wedges that holder the test specimen therebetween. Although such test specimen holders have been around for a long time, use of such holders has been confined to test specimens that are relatively large. Use on very small test specimens is not known.

Typical test specimens use geometries that have a minimum length of <NUM> or greater and cross sections of multiple millimeters x multiple millimeters. These specimens can be used in a variety of test specimen holders. The holders are installed in a force reaction structure or test machine that applies longitudinal forces along the long axis of the specimen. The holders typically have a method of crudely, but repeatably aligning the test specimen in the holder and the holders can be aligned to each other easily to ensure low bending strains as required by ASTM testing procedures. The holders also require the user to install the specimen in the holders while the test machine is actively maintaining position and load. Document <CIT> relates to a test sample holding and alignment means for tensile testing machines.

The field of additively manufactured components has required investigation into the material properties of the deposition process. This has resulted in specimen cross section geometries of less than <NUM> thick and less than <NUM> wide with an overall length of less than <NUM>. These specimen sizes do not fit with current specimen holders and there is no method of inserting the specimen in the holders in a repeatable fashion. There are also concerns as the specimens are so small that requires additional time to install a specimen thereby exposing the user to an active machine for a longer duration of time.

This Summary and the Abstract herein are provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary and the Abstract are not intended to identify key features or essential features of the claimed subject matter, nor are they intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the Background.

Generally, a support jig for use with a testing machine applying tensile loadsincludes a frame and a pair of spaced apart supports joined to the frame to provide an alignment axis. Each support is configured to releasably hold a test specimen holder on the alignment axis in a fixed spatial relationship with ends of the test specimen holders mountable to the test machine facing in opposite directions. The support jig can be used with any type of test specimen holder including but not limited to the test specimen holders herein disclosed.

In a one embodiment, the support jig further includes a test specimen support joined to the frame between the pair of spaced apart supports. The test specimen support conveniently holds the test specimen on the alignment axis so that the test specimen holders can be secured to each end of the test specimen. An end of the test specimen support can have a recess to receive the test specimen. Preferably, the test specimen support comprises a first portion joined to the frame and a second portion having the end. The second portion is adjustably secured to the first portion so as to adjust a position of the end orthogonally with respect to the alignment axis, which allows test specimens of different widths to be accurately placed on the alignment axis. The second portion can be linearly adjustable with respect to the first portion such as by telescoping with respect to the first portion.

Preferably, the pair of supports comprises a first support and a second support, wherein at least one support, and preferably both, are adjustably positionable on the frame to axially adjust a position of the support(s) on the alignment axis. In a preferred embodiment, each support includes a recess or protrusion spaced apart from the alignment axis that is complimentary to a protrusion or recess, respectively, provided on the associated test specimen holder securable to the support. The complementary engagement of the protrusion and the recess orients the test specimen holders about the alignment axis so as to properly mount to the test specimen.

In one embodiment, each support provides a mounting aperture for receiving a portion of the test specimen holder. Preferably, each support includes a removable portion securable to the end that forms the mounting aperture so as to allow convenient mounting of each test specimen holder. The end of each support and the removable portion include surfaces engageable with the test specimen holder that are complimentary with the test specimen holder.

Another aspect of the present invention is a method of using the support jig to remotely mount the test specimen to the test specimen holders from the test machine, and then using the support jig to maintain the fixed special relationship while the test specimen holders are mounted to the test machine is also disclosed.

In one embodiment, the method for loading a test specimen in a tensile test machine having a first test specimen holder and a second test specimen holder, includes: providing a support jig remote from the test machine; mounting the first test specimen holder and the second test specimen holder to the support jig so that heads configured to hold ends of the test specimen face each other and ends of the test specimen holders securable to the test machine face in opposite directions, the test specimen holders being aligned with each other and located on a common alignment axis; securing heads of the first and second test specimen holders to first and second ends, respectively, of the test specimen; and mounting the first test specimen holder and the second test specimen holder in the tensile test machine wherein the support jig holds the first test specimen holder and the second test specimen holder on the alignment axis and in a fixed spatial relationship relative to each other.

In a further embodiment, the jig incudes a test specimen support and the method further comprises mounting the test specimen to the test specimen support so as to be aligned with the alignment axis. Preferably, mounting the test specimen to the test specimen support so as to be aligned with the alignment axis occurs before securing the heads of the first test specimen holder and the second test specimen holder to the test specimen.

The jig can include a first support and a second support coupled to a frame, and wherein mounting the first test specimen holder and the second test specimen holder to a support jig comprises mounting the first test specimen holder to the first support and the second test specimen holder to the second support. Mounting the first test specimen holder and the second test specimen holder in the tensile test machine can occur after mounting the first test specimen holder and the second test specimen holder to the support jig and/or securing heads of the first and second test specimen holders to test specimen.

If desirable, so as to provide proper alignment of the test specimen holders to each other so as to hold the test specimen correctly, mounting the first test specimen holder and the second test specimen holder to the support jig can include fixing a rotational position of each of the first test specimen holder and the second test specimen holder about the alignment axis. Preferably, securing heads of the first and second test specimen holders to first and second ends, respectively, of the test specimen includes applying a preload clamping holding force to end of the test specimen.

One example not part of the claimed invention is a test specimen holder comprising a head body having a first inclined body surface and a second inclined body surface facing each other. A first and second wedge are located in the head body, the first wedge having a first inclined wedge surface in sliding contact with the first inclined body surface and the second wedge having a second inclined wedge surface in sliding contact with the second inclined body surface. A support shaft has a first end connectable to a portion of a test machine and a second end supporting the first and second wedges. A drive is supported by the support shaft, the drive being located between the second end and the first end. A spring is connected to the head body at a first end and to the drive at a second end.

Preferably, the drive is configured to pull the second end of the spring away from the head body. The drive can comprise a first portion movable with respect to a second portion, the first portion being connected to the second end of the spring and the second portion engages or is fixedly joined to a portion of the support shaft. The first portion can moves axially relative to the support shaft either with or without rotation about the support shaft.

The drive can include a driven part in contact with and movable relative to the first portion and the second portion. The driven part is movable toward and away from a longitudinal axis of the support shaft. Preferably, the drive includes an actuator supported by the first portion in contact with the driven part. In one embodiment, the actuator comprises a drive screw threadably engaging the first portion.

Engaging surfaces of the driven part and the second portion can include at least one inclined surface on at least one of the driven part and/or the second portion. Preferably, engaging surfaces of the driven part and the second portion are each an inclined surface.

The drive can include a wall forming a chamber about the support shaft, the driven element being disposed in the chamber, the drive can include an end cap joined to an end of the wall.

In one example the spring comprises a plurality of longitudinal spring elements disposed about the support shaft, preferably as a cylindrical body at least partially around the support shaft where the spring elements are integral with the body being formed from a single unitary body with longitudinal slots.

Preferably, at least one of the mount or the head body comprises one of an aperture opening to an outer surface and extending inwardly transversely to a longitudinal axis of the support shaft or a pin extending away from the outer surface in a direction transversely from the longitudinal axis so as to allowing mounting of the test specimen holder to the support jig.

Another example not part of the claimed invention includes a head body having a first inclined body surface and a second inclined body surface facing each other. First and second wedges are located in the head body, the first wedge having a first inclined wedge surface in sliding contact with the first inclined body surface and the second wedge having a second inclined wedge surface in sliding contact with the second inclined body surface. A mount is joined to the head body at a first end and has a bore. A support shaft is disposed in the bore and has a first end supporting the first and second wedges. A spring urges the support shaft toward the head body.

In one example the bore includes an inner flange, a first end of the spring engaging the support shaft and a second end engaging the inner flange. The spring can comprise a compression spring.

In one example an adjuster is provided and adjusts a force urging the support shaft toward the head body. The adjuster can comprise an actuator joined to the support shaft. For example, the actuator can comprise a screw threadably joined to the mount.

Preferably, a handle is joined to the support shaft and comprises portions extending in opposite directions from a longitudinal axis of the support shaft.

A material testing system <NUM> for applying force loads to a test specimen is illustrated in <FIG>. The system <NUM> typically would include an upper test specimen holder and an identical lower test specimen holder both of the type illustrated and described below. The test specimen holders hold a test specimen along a longitudinal axis <NUM>. The lower test specimen holder is connected to an actuator <NUM> through which force loads are applied to the test specimen and reacted against a reaction structure generally indicated at <NUM>.

In the exemplary embodiment illustrated, although other configurations are known and can be used with aspects of the invention described below, the material testing system <NUM> includes a frame <NUM> having a base <NUM>. A pair of support members <NUM> extends upwardly from the base <NUM> and are joined together by a crossbeam <NUM> which provides a stable support surface. A pair of support columns 8A extends upwardly from the crossbeam <NUM> to a crosshead 8B movable on the support columns 8A. A load cell <NUM> can join the upper test specimen holder to the crosshead 8B, as illustrated, or can join the lower test specimen holder to a rod of the actuator <NUM>. As is known in the art, the load cell <NUM> provides a signal indicative of tension or compression forces applied to the test specimen. The crosshead <NUM> and the support columns 8A provide the reaction structure. Hydraulic lifts 8C move the crosshead <NUM> to selectively fixed positions.

Generally, among other aspects, a test specimen holder <NUM>, <NUM> (<FIG>) is described capable of through zero fatigue loading, tension loading, and compression loading of miniature and sub-miniature test specimens of both flat and round geometries. The test specimen holder <NUM>, <NUM> works in conjunction with a specimen insertion or support jig <NUM> (<FIG>, <FIG> and <FIG>) that has the purpose of allowing specimen insertion to happen on a workbench or table remotely from the test machine <NUM>. The support jig holds the specimen holders <NUM>, <NUM> rigidly and accurately so that bending strains on the specimen inherent to the installation process are limited and repeatable. The support jig <NUM> provides a method of introducing clamping forces into the specimen holders <NUM>, <NUM> while not applying errant load to the specimen. The support jig <NUM> allows the user to verify the installation accuracy, and allows the installation of the jig/specimen holder sub-system to be installed into the test machine <NUM> without errant loads being applied to the test specimen until such time that the test machine <NUM> is in control and managing loads and displacements.

An aspect of the disclosure is the support jig <NUM> (<FIG>, <FIG> and <FIG>) that is used to mount a test specimen <NUM> to test specimen holders or grips <NUM>, <NUM> so as to be accurately positioned in the holders <NUM>, <NUM> without undesired loading, which can damage or break the test specimen <NUM> as well as aligning the test specimen <NUM> with axes of the test specimen holders <NUM>, <NUM> so as to perform required testing in the testing machine <NUM>. The support jig <NUM> allows loading the test specimen <NUM> to the test specimen holders <NUM>, <NUM> in an accurate and repeatable manner.

With the test specimen <NUM> loaded in the test specimen holders <NUM>, <NUM>, and the test specimen holders <NUM>, <NUM> secured to the jig <NUM>, the complete assembly comprising the test specimen holders <NUM>, <NUM>, support jig <NUM> and test specimen <NUM>, as illustrated in <FIG>, can be transferred to the test machine <NUM> (<FIG>), such the test machine <NUM> described above, can be used to impart forces and/or displacements to the test specimen <NUM>. Such test machines are known in the art as a tension or tensile tester (used for applying monotonic or single directions loads) or a tension/compression tester (which can be used in fatigue testing where alternating tension and compression loads can be applied). If desired, a rotational actuator, not shown, can be part of the test machine <NUM> with or without the linear actuator <NUM>. The support jig <NUM> allows the test specimen holders <NUM>, <NUM> and the test specimen <NUM> attached between the holders <NUM>, <NUM> to be loaded into the test machine <NUM> without causing breakage of the test specimen <NUM> because all loads between the test specimen holders <NUM>, <NUM> are transferred through the support jig <NUM> rather than through the test specimen <NUM>. When the test specimen holders <NUM>, <NUM> have been secured in the test machine <NUM>, the jig <NUM> can be detached from the test specimen holders <NUM>, <NUM> so that testing can commence.

Referring to <FIG> and <FIG>, the support jig <NUM> includes a frame <NUM> having a base <NUM>. A pair of spaced-apart supports 14A, 14B is joined to the base <NUM>. Each support 14A, 14B is configured to releasably hold a test specimen holder on an alignment axis <NUM> (<FIG>). A test specimen support <NUM> is joined to the frame <NUM> between the pair of spaced-apart supports 14A, 14B. The test specimen support <NUM> has an end <NUM> configured to hold the test specimen <NUM> on the alignment axis <NUM>.

The test specimen support <NUM> includes a first portion <NUM> joined to the base <NUM> or frame <NUM> and a second portion 20B having the end <NUM>. The second portion 20B is adjustably secured to the first portion 20A so as to adjust a position of the end <NUM> orthogonally with respect to the alignment axis <NUM>. Preferably the second portion 20B is linearly adjustable with respect to the first portion 20A. In the embodiment illustrated, the second portion 20B telescopes with respect to the first portion 20A. The end <NUM> can include a recess of size and shape to hold the test specimen <NUM> on the alignment axis <NUM>. A holding device such as a clip, clamp, tape, straps or the like can be provided on the end <NUM> if desired to aid in holding the test specimen <NUM> to the end <NUM>. Fasteners <NUM> secure the test specimen support <NUM> to the frame <NUM>, while a fastener <NUM> such as a setscrew can be used to fix the second portion 20B at a desired position with respect to the first portion 20A.

The pair of supports 14A, 14B preferably are adjustable on the frame <NUM> axially or parallel to the alignment axis <NUM> so as to adjust a position of supports 14A, 14B relative to the test specimen support <NUM>. Preferably, each of the supports 14A, 14B is adjustably positionable on the frame <NUM>, being mounted on a linear bearing support 26A, 26B, respectively. In a preferred embodiment, each linear bearing support 26A, 26B is mounted to a linear rail <NUM> with no backlash (vertical backlash in the illustrated embodiment) such that only linear movement along the rail <NUM> is possible.

In the embodiment illustrated, the frame <NUM> includes an optional alignment guide <NUM>. Each of the supports 14A, 14B is supported by the rail <NUM>, but the guide <NUM> defines the orientation of the alignment axis <NUM> wherein the alignment axis <NUM> in effect, remains parallel to the guide <NUM>. Preferably, each of the supports 14A, 14B and the test specimen support <NUM> include a bore 34A, 34B, 34C, respectively, so as to receive the guide <NUM>. The guide <NUM> is held in a stationary position with respect to the base <NUM> by a standoff <NUM>, which in the embodiment illustrated, also includes a bore <NUM> to receive an end of a guide <NUM> while fasteners such as set screws <NUM> fix the guide <NUM> to the standoff <NUM>.

The supports 14A, 14B move linearly with respect to the rail <NUM> being guided by guide <NUM> so as to remain in proper alignment. Once the test specimen holders <NUM>, <NUM> have been mounted in each respective support 14A, 14B, and the test specimen <NUM> is mounted to each of the holders <NUM>, <NUM>, the supports 14A, 14B are fixedly secured to the guide <NUM> each with a corresponding fastener <NUM>. In the embodiment illustrated, each fastener comprises a set screw for securing the position of each support 14A, 14B on the guide <NUM>. In <FIG>, set screw <NUM> secures support 14A to guide <NUM>, while support 14B includes a similar set screw, which is on a backside of support 14B in <FIG>. Likewise a fastener such as set screw <NUM> is used to secure the test specimen support <NUM> to the guide <NUM>.

It should be noted that use of the guide <NUM> is not a requirement. In particular, the guide <NUM> is not necessary if the supports 14A, 14B and test specimen support <NUM> can be secured to rail <NUM> such that alignment of the supports 14A, 14B and test specimen support <NUM> are suitably aligned with each other along the alignment axis <NUM>.

Herein disclosed are two different test specimen holders <NUM>, <NUM>. The test specimen holder <NUM> is generally used in tensile testing, but can be used also in fatigue testing at lighter loads. The test specimen holder <NUM> is particularly well suited for fatigue testing. Each test specimen holder <NUM>, <NUM> can be used with the support jig <NUM>. Each test specimen holder <NUM>, <NUM> is releasably secured to each corresponding support 14A, 14B. Generally, each of the test specimen holders <NUM>, <NUM> described below comprises a base or mount <NUM>, <NUM> and a head body <NUM>, <NUM> secured to the mount <NUM>, <NUM> (<FIG> and <FIG>). The mount <NUM>, <NUM> typically comprises a cylindrical member that can be inserted into corresponding recess provided in the test machine <NUM>, such as a grip, and secured therein. The head body <NUM>, <NUM> includes wedges that are used to hold an end of the test specimen <NUM> during testing.

In the embodiment illustrated, the supports 14A, 14B are releasably secured to the mounts <NUM>, <NUM> of each of the test specimen holders <NUM>, <NUM>; however, it should be noted, if desired, the supports 14A, 14B can be configured to releasably secure to each of the head body <NUM>, <NUM> of the test specimen holders <NUM>, <NUM>.

Each support 14A, 14B includes a mounting aperture configured to receive a portion of the test specimen holder <NUM>, <NUM>. In the embodiment illustrated, the mounting aperture is formed from a portion 40A, 40B, respectively, removably secured to an end 38A, 38B of each support 14A, 14B. Surfaces of the removable portions 40A, 40B and the ends 38A, 38B together engage surfaces of the test specimen holders <NUM>, <NUM>. Fasteners <NUM> secure each removable portion 40A, 40B to its corresponding end 38A, 38B.

For test specimens having generally flat ends to which the test specimen holders <NUM>, <NUM> are attached require that the test specimen holders <NUM>, <NUM> be properly oriented about the alignment axis <NUM> so as to coincide with and properly engage the ends of the test specimen <NUM>.

Since typically the test specimens have ends that are coplanar with each other, each of the test specimen holders <NUM>, <NUM> should be oriented in the same position with respect to each other so as to orient each of the test specimen holders <NUM>, <NUM> in their proper position. The supports 14A, 14B and holders <NUM>, <NUM> include a protrusion-aperture connection between the supports 14A, 14B and the test specimen holders <NUM>, <NUM> so as to align and also hold the test specimen holders <NUM>, <NUM> in their proper rotational positions about the alignment axis <NUM>. In the embodiment illustrated, the protrusion comprises a pin <NUM> (<FIG>). The pin <NUM> can be securely fixed in the support 14A, 14B such as in the removable portion 40A, 40B and/or, as illustrated, in the end 38A, 38B of each support 14A, 14B. With the supports 14A, 14B having the protrusions or pins <NUM>, the test specimen holders <NUM>, <NUM> include corresponding apertures <NUM>, <NUM> of size to receive a pin <NUM>. In an alternative embodiment, the protrusion such as a pin, can be disposed on the test specimen holder <NUM>, <NUM> wherein then the aperture would be provided on the supports 14A, 14B.

<FIG> illustrate the test specimen holder <NUM>. Generally, the test specimen holder <NUM> includes the mount or base <NUM> and the head body <NUM> secured to an end of the mount <NUM>. At an end opposite the head body <NUM>, the mount <NUM> is inserted into a corresponding recess provided in the test machine <NUM>, which could comprise another, larger test specimen holder. A stop-collar <NUM> limits how far the mount <NUM> is inserted into the test machine <NUM>.

As indicated above, it is preferable that the test specimen holder <NUM> be positioned in the support jig <NUM> where its rotational position is fixed in an accurate and repeatable manner. The protrusion-aperture described above can be used. In the embodiment illustrated, the protrusion herein comprising the pin <NUM> is secured to each of the supports 14A, 14B, while the aperture <NUM> resides in the mount <NUM>.

Generally, the test specimen holder <NUM> includes movable wedges <NUM> that are supported by and slide on a support plate <NUM>. Each of the wedges <NUM> has a specimen engaging face that faces the other wedge and engages the test specimen <NUM>. The wedges <NUM> are planar for use with flat test specimens; however this should not be considered limiting in that the wedges <NUM> can be configured to hold test specimens having other shapes such as test specimens having cylindrical ends, where for example, the wedges <NUM> would include notches. Together the wedges <NUM> engage the test specimen <NUM> from opposite sides. Each wedge <NUM> includes an inclined back surface <NUM>. Inclined surfaces <NUM> of a head body <NUM> engage the inclined back surfaces <NUM> of each wedge <NUM> and drive or urge the wedges <NUM> toward each other with relative displacement between the head body <NUM> and the wedges <NUM>. The use of such wedges in a head body is well-known and thus will not be further described, but it should be noted that although two wedges <NUM> are shown in the exemplary embodiment a single wedge or three or more wedges can be used, where each wedge commonly would engage the inclined surface <NUM> on the head body <NUM>.

Springs <NUM> are attached to the wedges <NUM> and have a spring bias that drives or urges the wedges <NUM> away from each other so as to create a space and allow easy insertion of the ends of the test specimen <NUM> between wedges <NUM>. Each of the springs <NUM> comprise a torsion spring having one end insertable into a recess or aperture <NUM> (<FIG>) provided in the wedge <NUM> while the other end is fixedly retained by the head body <NUM>, herein with an opposite end received in a recess or aperture <NUM> (<FIG>).

The support plate <NUM> for the wedges <NUM> is mounted to a support rod or shaft <NUM> that extends downwardly away from the head body <NUM>. The support plate <NUM> includes upstanding sides or edges that maintain the orientation of the wedges <NUM> so as to generally face each other but allow movement of the wedges <NUM> on the support plate <NUM> towards and away from each other. The test specimen holder <NUM> includes a bias spring <NUM> that generally biases the support shaft <NUM> upwardly towards the head body <NUM> so as to urge the wedges <NUM> towards each other and to engage the end of the test specimen located therebetween. The bias spring <NUM> herein is a coil spring received in a bore <NUM> provided in the mount <NUM>. The support shaft <NUM> includes an extending portion <NUM> having a width allowing it to be inserted into the coils provided in the bias spring <NUM>. A flange <NUM> is provided in the support shaft <NUM> that engages the uppermost coil of the bias spring <NUM>.

A handle <NUM> secured to the support shaft <NUM> allows the support shaft <NUM> to be pulled away from the head body <NUM> and against the bias spring <NUM> so as to allow the wedges <NUM> to open due to the spring force provided in the springs <NUM> that urge the wedges <NUM> away from each other. In the embodiment illustrated, the handle <NUM> has portions <NUM> that extend in opposite directions through slots <NUM> provided in the mount <NUM>. The handle portions <NUM> are secured to the support shaft <NUM> where the support shaft <NUM> includes a bore <NUM> of size to receive a handle shaft <NUM> therein. Generally the forgoing design allows the handle <NUM> to be pulled downwardly away from the head body <NUM> where the torsion springs <NUM> thereby urge the wedges <NUM> away from each other so as to allow the test specimen end to be insert therebetween. When the handle <NUM> is released, a clamping force is generated and applied to the end of the test specimen <NUM>.

A preload clamp force adjuster <NUM> (<FIG>, <FIG>) is provided to apply a force that further urges the wedges <NUM> toward each other so as to apply a preload clamping force upon the end of the test specimen <NUM>. The adjuster <NUM> includes an actuator <NUM> that urges the support shaft <NUM> toward the head body <NUM> so as to urge the wedges <NUM> toward each other. The adjuster <NUM> comprises a drive screw that abuts the end of the shaft <NUM> and is threadably connected to a threaded bore in the mount <NUM>.

The test specimen <NUM> is secured to the test specimen holder <NUM> in two steps. First, the handle <NUM> is pulled down against the bias spring <NUM>, which causes the wedges <NUM> to separate allowing the test specimen <NUM> to be located between the wedges <NUM>. When the handle is released, the wedges <NUM> contact and hold the test specimen <NUM> from the force provided by the bias spring <NUM>. The actuator <NUM> is then operated, herein by rotation of it being a drive screw to further urge the shaft <NUM> toward the head <NUM>, thereby driving the wedges <NUM> toward each other and against the test specimen <NUM>.

The second test specimen holder <NUM> is illustrated in <FIG>. The test specimen holder <NUM> includes the mount <NUM> and head body <NUM> and wedges <NUM>. The wedges <NUM> and head body <NUM> operate in the same manner as wedges <NUM> and head body <NUM> where inclined back surfaces on the wedges <NUM> slide upon inclined surfaces in the head body <NUM> so as to cause transverse movement of the wedges <NUM> toward each other.

The mount <NUM> is connected to a support shaft <NUM> on a first end 240A with a fastener <NUM>, while a second end 240B supports the first and second wedges <NUM>. A drive <NUM> supported by the support shaft is located between the first end 240A and the second end 240B. A spring <NUM> is connected, for example threadably, to the head body <NUM> at a first end and to the drive <NUM>, for example threadably, at a second end to cylindrical a first portion <NUM>.

The drive <NUM> is configured to pull upon the spring <NUM> so as to displace the head <NUM> downward axially relatively to the shaft <NUM>. Downward movement of the head <NUM> urges the wedges <NUM> toward each other. The test specimen <NUM> is secured to the test specimen holder <NUM> also in two steps. First with the threaded connection between the spring <NUM> and the first portion <NUM> at a minimum so as to allow the head <NUM> to be displaced upwardly away from the end of the shaft <NUM>, the wedges <NUM> are sufficiently away from each other to allow the test specimen to be inserted between the wedges <NUM>. Springs <NUM> urge the wedges <NUM> against the inclined surfaces of the head <NUM> so as to cause the wedges <NUM> create a space so as to allow insertion of the test specimen <NUM>. In this embodiment, each of the springs <NUM> are elongated with a first end fixedly joined to the support shaft <NUM> and second end to the wedge <NUM>.

The first portion <NUM> is then rotated about the shaft <NUM> so as to increase the threaded connection between the first portion <NUM> and the spring <NUM>. This pulls the spring <NUM> and head downwardly so that the wedges <NUM> are urged toward each other and against the test specimen <NUM>, where the spring <NUM> provides a spring force.

To further increase the clamping force of the wedges <NUM> the drive <NUM> includes an actuator or displacement mechanism to further displace the first portion <NUM> axially downwardly. The actuator mechanism includes a driven part <NUM> in contact with and moveable relative to the first portion <NUM> and a second portion <NUM>. In the embodiment illustrated, the driven part <NUM> is moveable, herein transversely, toward and away from a longitudinal axis of the support shaft <NUM>. An actuator <NUM> supported by the first portion <NUM> is in engaging contact with the driven part <NUM>. The actuator <NUM> moves toward and away from the longitudinal axis, preferably being arranged transversely with respect thereto. In the embodiment illustrated, the actuator <NUM> can comprise a drive screw threadably engaging the first portion <NUM>. Engaging surfaces of the driven part <NUM> and second portion <NUM> include an inclined surface on at least one of the driven part <NUM> and/or second portion <NUM>, and in a preferred embodiment, each of the driven part <NUM> and the second portion <NUM> include inclined surfaces engaging each other. A wall <NUM> can form a chamber <NUM> about the support shaft <NUM> wherein the driven part <NUM> and second portion <NUM> are disposed in the chamber <NUM>. An end cap <NUM> is joined to an end of the wall <NUM> so as to capture the driven part <NUM> and second portion <NUM> in the chamber <NUM> and maintain the driven part <NUM> in contact with the second portion <NUM>. The second portion <NUM> can be fixedly secured to the support shaft <NUM> and in one embodiment being integrally formed therewith being formed from a single unitary body. In an alternative embodiment, as illustrated, the second portion <NUM> is separable from the support shaft <NUM> and can comprise a disc shaped element having an aperture 216A through which a portion 240A of the support shaft <NUM> extends therethrough. In such a configuration, the second portion <NUM> engages an annular flange 240B provided on the support shaft <NUM> so as to provide a reaction structure.

With the second portion <NUM> comprising a disc element, the driven part <NUM> can also be formed as a disc having an aperture 228A through which the portion 240A of the support shaft <NUM> extends therethrough. The aperture 228A, however, comprises a slot with a longitudinal axis being transverse to the longitudinal axis of the support shaft <NUM>. The slotted aperture 228A allows the driven element <NUM> to move transversely with respect to the longitudinal axis of a support shaft <NUM>. In the embodiment illustrated, the actuator <NUM> comprises two separate actuators 230A, 230B wherein a first actuator 230A drives the driven part in the direct indicated by arrow 250A while a second actuator 230B is used to drive the drive element <NUM> in the opposite direction by arrow 250B. One or both of the actuators 230A, 230B can comprise a threaded element threadably engaging the first portion <NUM>.

To increase the clamping force of the wedges <NUM> upon the test specimen <NUM>, the actuator <NUM> is operated to displace the driven element <NUM>. In the embodiment illustrated due to the inclined surfaces on the second portion <NUM> and driven element <NUM>, movement of the actuator 230B in the direction of arrow 250B further displaces the cylindrical first portion <NUM> downwardly with respect to the shaft <NUM>, thereby increasing the tension in the spring <NUM> and pulling the head <NUM> downwardly. When the test specimen is to be removed, the actuator 230B is moved in the direction of arrow 250A, and then the actuator 230A is also operated to drive the driven element <NUM> in the direction of arrow 250A, allowing the cylindrical portion <NUM> to move axially upwardly. The cylindrical portion <NUM> can then be rotated to minimize the threaded connection of the spring and the cylindrical portion <NUM> sufficiently so the wedges <NUM> separate and allow removal of the test specimen <NUM>.

Referring to <FIG>, the spring <NUM> can comprise a plurality of longitudinal spring elements disposed about the support shaft <NUM>. In the embodiment illustrated, the spring <NUM> comprises a cylindrical body having longitudinal slots 212A wherein the spring elements are portions 212B of the cylindrical body located between successive longitudinal slots 212A. In one embodiment, the spring <NUM> is threadably joined to the head body <NUM> at a first end 212C and threadably joined to the drive <NUM> at a second end 212D.

Like the test specimen holder <NUM> described above, the aperture <NUM> is provided to receive the pin <NUM> of the support jig <NUM>. The pin <NUM> can be disposed between two successive longitudinal spring elements such as being disposed through one of the slots 212A provided in the cylindrical body.

A method of using the test specimen holders, such as but not limited to holders <NUM>, <NUM>, with the support jig <NUM> comprises preferably, positioning the support jig <NUM> on a work surface remote from the test machine <NUM>; securing the selected specimen holders to the supports 14A, 14B, preferably using the protrusion-aperture connection between the specimen holders and the supports 14A, 14B; locating the test specimen <NUM> in the specimen holders, herein with the exemplary holders <NUM>, <NUM> by opening the corresponding wedges of each of the test specimen holders <NUM>, <NUM> so as to locate ends of the test specimen <NUM> between the wedges. After the test specimen <NUM> is mounted to each of the specimen holders and the supports 14A, 14B have been secured to the jig <NUM> so that all or substantially all force loads between the specimen holders <NUM>, <NUM> are transferred through the jig <NUM>, thereby protecting the test specimen <NUM> from seeing such forces, the specimen holders <NUM>, <NUM> can be mounted in the test machine <NUM>, and once secured, the support jig <NUM> can then be removed.

In one embodiment, the method further includes allowing the supports 14A, 14B to move freely on the frame <NUM> of the support jig <NUM> during loading of the specimen end, and then securing the support 14A, 14B in a fixed position relative to the frame of the support jig <NUM>, or to the optional guide <NUM>.

With reference to <FIG> and the test specimen holders <NUM>, installing the test specimen <NUM> is as simple as placing it in one of the holders <NUM>, while opening the wedges <NUM> with the handle <NUM>, and releasing the wedges <NUM> on the test specimen <NUM> as illustrated in <FIG>. The test specimen holder <NUM> is brought toward the other end of the test specimen <NUM> and secured to it in the same manner to achieve the setup shown in <FIG>. Each actuator <NUM> of each holder <NUM> is then operated so as to increase the clamp forces upon the test specimen <NUM> as well as provide a solid load path from the wedges <NUM> to the mount <NUM>. The test specimen <NUM> is now installed in the holders <NUM>. The set screws of the supports 14A and 14B can be operated so as to secure the supports 14A and 14B to the rail <NUM> and/or the guide <NUM>, if provided. Specimen alignment in the test specimen holders can be verified through various means-mechanical measurement, optical measurement via light/shadow, lasers, and cameras. Other means of verification like photo elastic paint could also be used.

Referring to <FIG>, the jig <NUM> with the specimen holders (e.g. <NUM>) and test specimen <NUM> are transferred to the test machine <NUM>. In <FIG>, optional intermediate holders <NUM>, <NUM> are used. The upper test specimen holder is mounted to the load cell <NUM> that in turn is mounted to intermediate holder <NUM>, the intermediate holder <NUM> being mounted to an actuator if present in the crosshead <NUM>, or to the crosshead <NUM> directly. Similarly, the lower specimen test holder is mounted to lower intermediate holder <NUM> that is mounted to the actuator <NUM> or to a test machine base through a load cell if provided.

In the exemplary test machine <NUM> of <FIG>, one mount of the test specimen holders <NUM> is installed in the test machine <NUM> for example with a direct connection via a clevis pin to the load cell <NUM>. After installing one end, the test machine <NUM> can be operated so as to position the other end, for example, having grip <NUM> so as to grasp the end of the other test specimen holder <NUM>. After mounting, preferably, the test machine <NUM> is placed in force control and operated so that zero force is being applied between the test specimen holders <NUM>. With zero force applied, the jig <NUM> can then be removed and the test machine <NUM> is now ready to conduct a test upon the test specimen. Reverification of specimen alignment in the test specimen holders can again be verified through various means-mechanical measurement, optical measurement via light/shadow, lasers, and cameras. Other means of verification like photo elastic paint could also be used.

Claim 1:
A support jig (<NUM>) for use with a testing machine (<NUM>) applying tensile loads, the support jig (<NUM>) comprising:
a frame (<NUM>); and
a pair of spaced apart supports (14A, 14B) joined to the frame (<NUM>) to provide an alignment axis (<NUM>), each support (14A, 14B) configured to releasably hold a test specimen holder (<NUM>, <NUM>) on the alignment axis (<NUM>) in a fixed spatial relationship with ends of the test specimen holders (<NUM>, <NUM>) mountable to the test machine (<NUM>) facing in opposite directions; and
a test specimen support (<NUM>) joined to the frame (<NUM>) between the pair of spaced apart supports (14A, 14B), the test specimen support (<NUM>) having an end (<NUM>) configured to hold a test specimen (<NUM>) on the alignment axis.