Patent Description:
The physical testing of materials and/or components by taking a test specimen and applying tension and/or compressive loads and/or displacements using an actuator is well known. For example, <CIT> and <CIT> disclose a load testing apparatus for applying a known load to a test specimen to test its strength. Commonly, the tension and compression loads are applied to the test specimen in an alternating matter at a selected frequency, or through a range of frequencies at constant displacement or amplitude. In harmonic motion, such as present in this form of testing, the acceleration of moving components of the actuator, the specimen grips, etc. are proportional to the amount of displacement multiplied by the square of the frequency. Therefore, even if the amplitude is small (e.g. <NUM>), the acceleration can be very large at higher frequencies (e.g. <NUM>-<NUM> Hertz.

Consequently, the force, which proportional to the mass of the moving components times the acceleration, is also increasing by the square of the frequency, as the frequency increases. Moreover, this force must be reacted by the structure of the test system, which will cause excitation of modes in the test system.

A common test machine includes a base with upstanding columns that support a crosshead over the base. A first specimen grip is coupled to the crosshead through a force transducer, while a second specimen grip is coupled to the base using an actuator; however the location of the actuator and force transducer can be reversed.

Due to the large dynamic forces, vibrations can be present during operation. One mode of vibration that is proving to be detrimental to testing is a "box mode" excited in the box-like construction of the crosshead, base and columns. This mode is detrimental because these mode cause the force transducer (and/or displacement sensor) to move up and down, which induces error in its corresponding output signal(s).

This Summary is provided to introduce some concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features, essential features or all features of the invention. In addition, the description herein provided and the claimed subject matter should not be interpreted as being directed to addressing any of the short-comings discussed in the Background.

A testing machine includes a base, at least a pair of columns joined to the base and a crosshead joined to the columns at a location spaced apart from the base. At least a pair of specimen holders is provided. A first specimen holder is supported by the crosshead and faces the base, and a second specimen holder is supported by the base, the base being that portion joined to each of the columns closest to the crosshead. An actuator connected in series between one of the specimen holders and the corresponding base or crosshead. A brace connected to each of the columns and spanning between the columns, the brace being connected to each of the columns at a location along a length thereof between the base and the crosshead.

Embodiments can include one or more of the following features. The brace can be connected to each of the columns at various locations. In a first embodiment, the brace is connected to each of the columns between ends of the specimen holders remote from each other, while in another embodiment it may be preferable to connect the to each of the columns between ends of the specimen holders closest to each other.

Some preferred ranges include locating the brace being connected to each of the columns at a location in a range of about <NUM>% to <NUM>% of a distance between the ends of the specimen holders closest to each other. In a further embodiment, the brace is connected to each of the columns at a location in a range of about <NUM>% to <NUM>% of a distance between the ends of the specimen holders closest to each other. The brace can also be connected to each of the columns at about <NUM>% of a distance between the ends of the specimen holders closest to each other.

Each column includes an axis and the brace can include portions extending along planes between the columns that are parallel to a plane having the axes of both columns. The portions at each end of the brace are joined to opposite sides of an outer surface of each respective column along a bisecting plane for each column, the bisecting planes being normal to the plane extending between the columns. The brace includes an aperture through which an axis between the specimen holders can extend. The brace includes a removable portion defining a portion of the aperture, allowing easy insertion and removal of the test specimen without removing or moving the brace along the columns.

Typically, the test machine includes at least a pair of columns but also may include additional columns such as four columns. With more than two columns, a second brace can be connected between two different columns than the first brace, the second brace being connected to each of the respective columns at a location along a length thereof at least between ends of the specimen holders remote from each other. Depending on the number of columns, the testing machine may include a third brace and a fourth brace, the brace, the second brace, the third brace and the fourth brace each connecting adjacent columns about a perimeter encircling an axis extending between the specimen holders.

The columns can extend through base. Ends of the columns on a side of the base remote from the crosshead typically are joined together in such an embodiment. Likewise, the columns can extend through the crosshead, where ends of the columns on a side of the crosshead remote from the base are joined together.

The testing machine also includes a base; at least a pair of columns joined to the base; a crosshead joined to the columns at a location spaced apart from the base; at least a pair of specimen holders, where a first specimen holder is supported by the crosshead and faces the base, and a second specimen holder is supported by the base, the base being that portion joined to each of the columns closest to the crosshead; an actuator connected in series between one of the specimen holders and the corresponding base or crosshead;
A testing machine includes a base, at least a pair of columns joined to the base and a crosshead joined to the columns at a location spaced apart from the base. At least a pair of specimen holders is provided. A first specimen holder is supported by the crosshead and faces the base, and a second specimen holder is supported by the base, the base being that portion joined to each of the columns closest to the crosshead. An actuator connected in series between one of the specimen holders and the corresponding base or crosshead. A brace assembly is connected to each of the columns at a location along a length of each column between the base and the crosshead, the brace assembly spanning between the columns so as to connect the columns together or to the base or the crosshead. In a first embodiment, the brace connected to and span between the columns at a location spaced apart from the base and the crosshead. In addition or in the alternative, the brace assembly may include a gusset connected to each column, where a first end of the gusset is connected to the column and a second end is connected to the base or the crosshead.

A schematic view of a testing machine <NUM> for applying forces or motions to a test specimen (not illustrated) is illustrated in <FIG>. The testing machine includes a frame <NUM> having a base <NUM>, a pair of columns <NUM> that extend upwardly from the base <NUM>, and a crosshead <NUM> joined two of the columns <NUM> at a location spaced apart from the base <NUM>. At least a pair of specimen holders, 20A, 20B, are provided. A first specimen holder 20A is supported by the crosshead <NUM> and extends toward the base <NUM>. A second specimen holder 20B is supported by the base <NUM> and extends toward the crosshead <NUM>. It should be noted, the base <NUM> is that portion of the testing machine <NUM> that is joined to each of the columns <NUM> closest to the crosshead <NUM>.

An actuator <NUM> is connected in series between one of these specimen holders 20A, 20B and the corresponding base <NUM> or crosshead <NUM>. In the embodiment illustrated, the first specimen holder 20A is joined to a force transducer <NUM> that is supported by the crosshead <NUM>, while the second specimen holder 20B is coupled to the actuator <NUM> in the base <NUM>. It should be noted in another embodiment, the actuator <NUM> is located in the crosshead <NUM> whereas the force transducer <NUM> would then be joined to the base <NUM>.

Referring to <FIG> and <FIG>, a brace assembly herein illustrated as a brace <NUM> is connected to each of the columns <NUM> and spans between the columns <NUM>, the brace <NUM> is connected to each of the columns <NUM> at a location along a length thereof between the base <NUM> and the crosshead <NUM>. The testing machine <NUM> has several resonant modes of vibration. One mode of vibration that is significant is commonly referred to as "the box mode". With the addition of the brace <NUM> coupling the columns <NUM> together, such as roughly at the mid-span of the columns <NUM> between the base <NUM> and the crosshead <NUM>, a significant increase in the box mode frequency is obtained relative to a testing machine without the brace <NUM>. <FIG> and <FIG> pictorially illustrate in an exaggerated form the testing machine <NUM> with and without the brace <NUM>, respectively. In <FIG>, the testing machine <NUM> without the brace <NUM> experiences significant deformation at roughly the mid-span of the columns <NUM> with decreasing deformation extending downwardly towards the base <NUM> and upwardly towards the crosshead <NUM>.

In <FIG>, the brace <NUM> extends between the columns <NUM>. The deformation of the columns <NUM> at the mid-span has been reduced significantly, although additional deformation can be present in the crosshead <NUM>. More importantly, the box mode resonant frequency has increased from about <NUM> Hertz without the brace <NUM> and to about <NUM> Hertz with the brace <NUM>. <FIG> illustrates box mode resonant frequencies for specimens of different lengths.

Although illustrated in <FIG> and <FIG> where the brace <NUM> is disposed at about the mid-span of the columns <NUM>, other locations along the columns <NUM> can provide benefit. Generally, the brace <NUM> is connected to each of the columns <NUM> at a location along a length thereof between the ends of the specimen holders 20A, 20B remote from each other. In a further embodiment, the brace <NUM> is connected to each of the columns <NUM> between ends of the specimen holders 20A, 20B closest to each other. In a further embodiment, the brace <NUM> is connected to each of the columns <NUM> at a location at a range of about <NUM>% to about <NUM>% of a distance between the ends of the specimen holders 20A, 20B closest to each other. In yet another embodiment, the brace <NUM> is connected to each of the columns at a location and a range of about <NUM>% to about <NUM>% of a distance between the ends of the specimen holders 20A, 20B closest to each other. The brace <NUM> can also be connected to each of the columns <NUM> at about <NUM>% of a distance between the ends of the specimen holders 20A, 20B closest to each other.

Each column <NUM> includes an axis <NUM> and the brace <NUM> includes portions <NUM> extending along planes <NUM> between the columns <NUM> that are parallel to a plane <NUM> having the axes <NUM> of both columns <NUM>. In one embodiment, the portions <NUM> at each end of the brace <NUM> are joined to opposite sides of an outer surface of each respective column <NUM> at a bisecting plane <NUM> for each column <NUM>, the bisecting planes <NUM> being normal to the plane <NUM> extending between the columns <NUM>. It is believed locating or joining the brace <NUM> at the points on the outer surface of the columns <NUM> coincident with the bisecting planes <NUM> provides the most stiffness to the columns <NUM>. Typically, the brace <NUM> is mounted to the columns <NUM> so as to provide structural elements, such as portions <NUM>, that extend in a plane that is perpendicular to axes of the columns <NUM>.

Referring to <FIG>, the brace <NUM> includes an aperture <NUM> through which an axis <NUM> (<FIG>) between the specimen holders 20A, 20B extends. The aperture <NUM> thus allows a test specimen to be joined to the specimen holders 20A, 20B along the axis <NUM> without being in contact with portions of the brace <NUM>. The aperture <NUM> can be of size so as to allow an end of the test specimen to extend through the aperture <NUM> during loading where then the ends of the test specimen can then be attached to each other specimen holders 20A, 20B. It should be noted in the exemplary embodiment, columns <NUM> have a relatively large diameter, which may be wider than the test specimen to be tested; however, the configuration of brace <NUM> illustrated should not be limiting in that the brace <NUM> can have an aperture that is about the same size or larger than the diameter of the columns <NUM>, in which case, portions of the brace <NUM> extending between the columns <NUM> can bow out in one or both of the directions indicated by double arrow <NUM> if necessary to provide the larger aperture.

A portion <NUM> of the brace <NUM> that defines part of the perimeter of the aperture <NUM> is removable so as to allow the test specimen to be inserted into the aperture <NUM> or removed therefrom. The portion <NUM> is then reattached once the test specimen has been mounted to the specimen holders 20A, 20B. The removable portion <NUM> can be joined to other portions of the brace <NUM> using suitable fasteners <NUM> such as threaded bolts or the like. In another embodiment, the portion <NUM> may be hinged at one end such that only one fastener is needed to secure the portion <NUM> to the other portions of the brace <NUM>.

Ends 30A, 30B of the brace are secured to the columns <NUM> such as upon the outer surfaces thereof. In one embodiment, each of the ends 30A, 30B comprises a clamp that is clamped upon the outer surface of the columns <NUM>. For instance, the clamp at each end 30A, 30B can comprise a split collar with one or more suitable fasteners <NUM> such as a threaded bolt or the like that can constrict or expand an inner diameter (or also mount the separate portions together) of the brace <NUM> so as to clamp upon the outer surface of the column <NUM>.

It should be noted that the brace <NUM> herein disclosed is not limited to testing machines only having a pair of columns, but rather, can be used with other multi-column testing machines. <FIG> is a top schematic sectional view of a testing machine <NUM>' having four columns <NUM>. In such a testing machine, multiple braces <NUM>, <NUM>, <NUM> and <NUM> (similar to brace <NUM>) are used between adjacent columns <NUM> so as to form a structure <NUM> with individual braces <NUM>-<NUM> spanning between adjacent columns. In addition, or in the alternative, braces <NUM>, <NUM> can extend between non-adjacent columns <NUM>, such as diagonally when four columns <NUM> are arranged in a square or a rectangle. The braces <NUM>, <NUM> that extend diagonally hence would potentially extend or bisect the test specimen axis extending between the specimen holders; and therefore, braces <NUM>, <NUM> can also include apertures such as similar to aperture <NUM> in brace <NUM>.

Referring to back to <FIG>, testing machine <NUM> has columns <NUM> that extend through the base <NUM> to a connecting element <NUM> that joins ends of the columns <NUM> on a side of the base <NUM> remote from the crosshead <NUM>. Likewise, if desired, the columns <NUM> can extend through the crosshead <NUM> as indicated in dash lines and be connected with a structural element <NUM> on ends thereof that are remote from the base <NUM>. In the embodiment of <FIG>, the base <NUM> is moveable along the columns <NUM> and is selectively fixed thereto with clamping devices <NUM> comprising pneumatic or hydraulic actuators that clamp portions of the base <NUM> to the outer surface of the columns <NUM>. The base <NUM> is adjustable so as to vary the distance between the specimen holders 20A, 20B depending upon the length of the test specimen being tested.

<FIG> illustrates another form of brace assembly <NUM> comprising one or more gussets <NUM>, <NUM>, <NUM>, <NUM> (schematically depicted) connected to the columns <NUM> at first portions at the locations indicated above such as at or about mid-span between the base <NUM> and the crosshead <NUM>. The gussets <NUM>-<NUM> can be mounted to the columns <NUM> using the split collars as found in brace <NUM>. The gussets <NUM>-<NUM> are also securely fixed to the base <NUM> as illustrated, but could be fixed to the crosshead <NUM>, if desired.

Claim 1:
A testing machine (<NUM>) comprising:
a base (<NUM>);
at least a pair of columns (<NUM>) joined to the base (<NUM>);
a crosshead (<NUM>) joined to the columns (<NUM>) at a location spaced apart from the base (<NUM>);
at least a pair of specimen holders (20A, 20B), wherein a first specimen holder (20A) is supported by the crosshead (<NUM>) and faces the base (<NUM>), and a second specimen holder (20B) is supported by the base (<NUM>), the base (<NUM>) being that portion joined to each of the columns (<NUM>) closest to the crosshead (<NUM>);
an actuator (<NUM>) connected in series between one of the specimen holders (20A, 20B) and the corresponding base (<NUM>) or crosshead (<NUM>); and
a brace (<NUM>) connected to each of the columns (<NUM>) and spanning between the columns (<NUM>), the brace (<NUM>) being connected to each of the columns (<NUM>) at a location along a length thereof between the base (<NUM>) and the crosshead (<NUM>),
characterised in that the brace (<NUM>) includes an aperture (<NUM>) through which an axis between the specimen holders (20A, 20B) extend, and in that the brace (<NUM>) includes a removable portion (<NUM>) defining a portion of the aperture (<NUM>).