Testing system with column brace

Abstract

To suppress unfavorable oscillation during operating in a material testing machine.SOLUTION: A testing machine 10, 10' comprises: a base 12; at least a pair of columns 14 that is joined to the base 12; and a crosshead 16 that is joined to the columns 14. A first specimen holder 20A is supported by the crosshead 16, and a second specimen holder 20B is supported by the base 12. An actuator 22 is connected in series between one of the first and second specimen holders and the corresponding base 12 or crosshead 16. A brace 30 is connected to each of the pair of columns, and spans between the columns of the pair. The brace has an opening in which an axis between the first and second specimen holders extends, and includes a removable part that defines a part of the opening.SELECTED DRAWING: Figure 3

Description

[Background technology]

[0001] The following discussion is provided for general background information only and is not intended to be used as an aid in determining the scope of the claimed subject matter.

[0002] Physical testing of materials and / or components by taking a test sample and applying tensile and / or compressive loads and / or displacements using an actuator is known. Typically, tensile and compressive loads are applied to the test sample alternately at a selected frequency or over a range of frequencies at a constant displacement or amplitude. In harmonic motion, such as that present in this form of testing, the acceleration of the actuator's moving member, sample grip, etc., is proportional to the displacement multiplied by the square of the frequency. Thus, even for small amplitudes (e.g., 0.06 mm), the acceleration can be very large at high frequencies (e.g., 700 Hz to 1000 Hz).

[0003] As a result, the force, which is proportional to the mass of the moving part multiplied by the acceleration, also increases by the square of the frequency as the frequency increases. Furthermore, this force must be reacted to by the structure of the test system, resulting in excitation of the modes of the test system.

[0004] A typical testing machine includes a base with an upright support that supports a crosshead across the base. A first sample grip is coupled to the crosshead through a force transducer, while a second test grip is coupled to the base using an actuator, although the positions of the actuator and force transducer may be reversed.

[0005] Due to the large dynamic forces, vibrations may occur during operation. One vibration mode that is considered undesirable for testing is the "box mode" excited in the box-like structure of the crosshead, base, and support. This mode is undesirable because it causes the force transducers (and / or displacement sensors) to move up and down, causing errors in their corresponding output signal(s). Summary of the Invention

[0006] 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, essential, or all features of the invention. Additionally, the description and claimed subject matter provided herein should not be construed as addressing any of the shortcomings discussed in the Background.

[0007] The testing machine includes a base, at least one pair of struts connected to the base, and a crosshead connected to the struts at a location remote from the base. At least one 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 connected to each of the struts closest to the crosshead. An actuator is connected in series between one of the specimen holders and the corresponding base or crosshead. A brace is connected to each of the struts and spans between them. The brace is connected to each of the struts at a location along its length between the base and the crosshead.

[0008] Embodiments may include one or more of the following features: The braces may be connected to each of the struts at various locations. In a first embodiment, the braces are connected to each of the struts between the ends of the sample holders that are remote from each other, while in other embodiments, it may be preferable to connect the braces to each of the struts between the ends of the sample holders that are closest to each other.

[0009] Some preferred ranges include placing a brace connected to each of the struts at a distance between the ends of the nearest sample holders that is between about 25% and 75% of the distance between the ends of the nearest sample holders. In further embodiments, the brace is connected to each of the struts at a distance between about 40% and 60% of the distance between the ends of the nearest sample holders. The brace can also be connected to each of the struts at a distance between about 50% of the distance between the ends of the nearest sample holders.

[0010] Each strut has an axis, and the brace can have a portion extending along a plane between the struts that is parallel to the plane containing the axes of both struts. A portion at each end of the brace is joined to opposite sides of the outer surface of each strut along a bisecting plane of each strut, the bisecting plane being perpendicular to the plane extending between the struts. The brace can have an opening through which the axis between the sample holders can extend. If desired, the brace can have a removable portion that defines a portion of the opening, which facilitates insertion and removal of a test sample without removing the brace or moving the brace along the struts.

[0011] Typically, the testing machine includes at least one pair of support columns, but may include additional support columns, such as four support columns. In the case of three or more support columns, a second brace may be connected between two support columns different from the first brace, with the second brace connected to each of the respective support columns at a location along their length between at least the ends of the specimen holders that are remote from each other. Depending on the number of support columns, the testing machine may also include a third brace and a fourth brace, with the second brace, the third brace, and the fourth brace each connecting adjacent support columns around a periphery surrounding an axis extending between the specimen holders.

[0012] The struts can extend through the base. In such embodiments, the ends of the struts on the side of the base remote from the crosshead are typically joined together. Similarly, the struts can extend through the crosshead, in which case the ends of the struts on the side of the crosshead remote from the base are joined together.

[0013] The testing machine also includes a base, at least one pair of support posts joined to the base, a crosshead joined to the support posts at a position spaced from the base, at least one pair of sample holders, a first sample holder supported by the crosshead and facing the base, and a second sample holder supported by the base, the base being the portion joined to each of the support posts closest to the crosshead, and an actuator connected in series between one of the sample holders and the corresponding base or crosshead.

[0014] The testing machine includes a base, at least one pair of struts connected to the base, and a crosshead connected to the struts at a location remote from the base. At least one pair of sample holders is provided. A first sample holder is supported by the crosshead and faces the base, and a second sample holder is supported by the base, the base being the portion connected to each of the struts closest to the crosshead. An actuator is connected in series between one of the sample holders and the corresponding base or crosshead. A brace assembly is connected to each of the struts at a location along the length of each strut between the base and the crosshead, and the brace assembly spans between the struts to connect the struts together or to the base or crosshead. In a first embodiment, the brace is connected to the struts at a location remote from the base and the crosshead and spans between the struts. Additionally or alternatively, the brace assembly may include a gusset coupled to each strut, with a first end of the gusset coupled to the strut and a second end coupled to the base or crosshead. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is a side view of the testing machine. [Figure 2] FIG. 1 is an enlarged view of a portion of the testing machine. [Figure 3] FIG. 1 is a perspective view of a portion of a testing machine. [Figure 4] FIG. 4 is a cross-sectional view of the testing machine taken along line IV-IV in FIG. 3. [Figure 5] 10A-10C are pictorial representations of the deformation of the testing machine at selected frequencies without the column brace. [Figure 6] 10A-10C are pictorial representations of the deformation of the testing machine at selected frequencies with the column brace. [Figure 7] FIG. 10 shows the box mode resonance frequencies of samples with different lengths. [Figure 8] FIG. 1 is a schematic diagram showing a strut brace. DETAILED DESCRIPTION OF THE INVENTION

[0016] A schematic diagram of a testing machine 10 for applying a force or motion to a test sample (not shown) is shown in FIG. 1. The testing machine includes a frame 11 having a base 12, a pair of posts 14 extending upwardly from the base 12, and a crosshead 16 joined to two of the posts 14 at a location distal to the base 12. At least one pair of specimen holders 20A, 20B is provided. A first specimen holder 20A is supported by the crosshead 16 and extends toward the base 12. A second specimen holder 20B is supported by the base 12 and extends toward the crosshead 16. It should be noted that the base 12 is the portion of the testing machine 10 joined to each of the posts 14 closest to the crosshead 16.

[0017] An actuator 22 is connected in series between one of these sample holders 20A, 20B and the corresponding base 12 or crosshead 16. In the illustrated embodiment, the first sample holder 20A is bonded to a force transducer 24 supported by the crosshead 16, while the second sample holder 20B is coupled to an actuator 22 within the base 12. It should be noted that in another embodiment, the actuator 22 is located within the crosshead 16, while the force transducer 24 is, in this case, bonded to the base 12.

[0018] Referring to Figures 3 and 4, a brace assembly, exemplified herein as a brace 30, is connected to and spans each of the columns 14 at locations along their length between the base 12 and the crosshead 16. The testing machine 10 has several resonant vibration modes. One important vibration mode is commonly referred to as the "box mode." When braces 30, which connect the columns 14 together, are added generally midway between the base 12 and the crosshead 16, the box mode frequency increases significantly compared to a testing machine without the braces 30. Figures 5 and 6 show exaggerated images of the testing machine 10 without and with the braces 30, respectively. In Figure 5, the testing machine 10 without the braces 30 exhibits significant deformation generally midway along the columns 14, with less deformation progressing downward toward the base 12 and upward toward the crosshead 16.

[0019] In Figure 6, braces 30 extend between the struts 14. Although additional deformation may occur at the crosshead 16, deformation in the middle of the struts 14 is significantly reduced. More importantly, the box mode resonant frequency increased from about 715 Hz without the braces 30 to about 824 Hz with the braces 30. Figure 7 shows the box mode resonant frequencies for samples of different lengths.

[0020] Although FIGS. 3 and 6 illustrate the brace 30 disposed around the middle of the support columns 14, other locations along the support columns 14 may provide benefits. Generally, the brace 30 is coupled to each support column 14 at a location along its length between the ends of the sample holders 20A, 20B that are remote from each other. In a further embodiment, the brace 30 is coupled to each support column 14 between the ends of the sample holders 20A, 20B that are closest to each other. In a further embodiment, the brace 30 is coupled to each support column 14 at a location that is between about 25% and about 75% of the distance between the ends of the sample holders 20A, 20B that are closest to each other. In yet another embodiment, the brace 30 is coupled to each support column 14 at a location that is between about 40% and about 60% of the distance between the ends of the sample holders 20A, 20B that are closest to each other. The brace 30 may also be coupled to each support column 14 at a location that is between about 50% of the distance between the ends of the sample holders 20A, 20B that are closest to each other.

[0021] Each strut 14 has an axis 32, and the brace 30 has a portion 40 that extends along a plane 41 between the struts 14 that is parallel to a plane 43 containing the axes 32 of both struts 14. In one embodiment, the portion 40 at each end of the brace 30 is joined to opposite sides of the outer surface of each strut 14 at a bisecting plane 45 of each strut 14 that is perpendicular to the plane 43 extending between the struts 14. Locating or joining the brace 30 to a point on the outer surface of the strut 14 that coincides with the bisecting plane 45 is believed to provide maximum stiffness for the strut 14. Typically, the brace 30 is attached to the strut 14 to provide a structural element such as the portion 40 that extends in a plane perpendicular to the axis of the strut 14.

[0022] Referring to FIG. 4 , the brace 30 can have an opening 42 through which an axis 44 ( FIG. 2 ) between the specimen holders 20A, 20B extends. The opening 42 thus allows a test specimen to be coupled to the specimen holders 20A, 20B along the axis 44 without contacting any portion of the brace 30. The opening 42 can be sized to allow an end of the test specimen to extend through the opening 42 upon loading, allowing the end of the test specimen to be subsequently attached to each of the other specimen holders 20A, 20B. While, in the exemplary embodiment, the diameter of the struts 14 may be relatively large and wider than the test specimen being tested, it should be noted that the configuration of the illustrated brace 30 is not intended to be limiting in that the portion of the brace 30 extending between the struts 14 may be curved outward in one or both directions, as indicated by the double-headed arrow 47, to provide a larger opening, if necessary.

[0023] In a further embodiment, a portion 46 of brace 30 that defines a portion of the periphery of opening 42 is removable to allow for insertion or removal of a test specimen from opening 42. Portion 46 is then reattached once the test specimen is attached to specimen holders 20A, 20B. Removable portion 46 can be joined to other portions of brace 30 using suitable fasteners 48, such as threaded bolts. In another embodiment, portion 46 can be hinged at one end so that only one fastener is required to secure portion 46 to other portions of brace 30.

[0024] The ends 30A, 30B of the brace are secured to the column 14, e.g., its outer surface. In one embodiment, the ends 30A, 30B each include a clamp that clamps the outer surface of the column 14. For example, the clamp at each end 30A, 30B can include a split collar with one or more suitable fasteners 51, such as a threaded bolt, that can reduce or expand the inner diameter of the brace 30 (or even attach separate portions together) to clamp the outer surface of the column 14.

[0025] It should be noted that the brace 30 disclosed herein is not limited to testing machines having only one pair of support columns, but can also be used with other multiple-column testing machines. FIG. 8 is a schematic top cross-sectional view of a testing machine 10′ having four support columns 14. In such a testing machine, multiple braces 52, 53, 54, and 55 (similar to brace 30) are used between adjacent support columns 14, with each brace 52-55 forming a structure 56 that spans the adjacent columns. Additionally or alternatively, braces 58, 59 can extend diagonally between non-adjacent support columns 14 when the four support columns 14 are arranged in a square or rectangular configuration. Thus, the diagonally extending braces 58, 59 can extend across or bisect the test sample axis that extends between the sample holders, and thus the braces 58, 59 can also have openings similar to the opening 42 of brace 30.

[0026] Referring again to FIG. 1 , testing machine 10 has struts 14 extending through base 12 to connecting elements 70 that join the ends of struts 14 on the side of base 12 remote from crosshead 16. Similarly, if desired, struts 14 can extend through crosshead 16, as shown in dashed lines, and connect with structural elements 72 on the end of crosshead 16 remote from base 12. In the embodiment of FIG. 1 , base 12 is movable along struts 14 and selectively secured to struts 14 using clamping devices 80 that include pneumatic or hydraulic actuators that clamp portions of base 12 to the exterior surfaces of struts 14. Base 12 is adjustable to change the distance between specimen holders 20A, 20B depending on the length of the test specimen being tested.

[0027] 3 shows another form of brace assembly 80 with one or more gussets 81, 82, 83, 84 (drawn diagrammatically) connected to the post 14 at a location indicated above, e.g., intermediate between the base 12 and the crosshead 16 or at a first portion thereof. The gussets 81-84 may be attached to the post 14 using split collars such as those found on brace 30. The gussets 81-84 are also rigidly secured to the base 12 as shown, but may also be secured to the crosshead 16 if desired.

[0028] [Aspect 1] A base and At least one pair of posts joined to the base; a crosshead joined to the support column at a position spaced from the base; at least one pair of sample holders, a first sample holder supported by the crosshead and facing the base, and a second sample holder supported by the base, the base being a portion joined to each of the support posts closest to the crosshead; an actuator coupled in series between one of the sample holders and the corresponding base or crosshead; a brace connected to and spanning each of the struts, the brace connected to each of the struts at a location along its length between the base and the crosshead. [Aspect 2] 2. The testing machine of claim 1, wherein the brace is coupled to each of the struts between ends of the sample holder that are remote from each other. [Aspect 3] 3. The testing machine of claim 1 or 2, wherein the brace is coupled to each of the struts between the ends of the sample holders that are closest to each other. [Aspect 4] The testing machine according to any one of aspects 1 to 3, wherein the brace is connected to each of the supports at a distance in the range of approximately 25% to 75% between the ends of the sample holders that are closest to each other. [Aspect 5] 5. The testing machine of claim 4, wherein the braces are coupled to each of the supports at a distance in the range of approximately 40% to 60% between the ends of the sample holders that are closest to each other. [Aspect 6] 6. The testing machine of claim 5, wherein the braces are coupled to each of the struts at a distance that is about 50% between the ends of the sample holders that are closest to each other. [Aspect 7] A testing machine according to any one of aspects 1 to 6, wherein each support has an axis, and the brace has a portion extending along a plane between the support pillars that is parallel to a plane having the axes of both support pillars. [Aspect 8] 8. The testing machine of claim 7, wherein the portions at each end of the brace are joined to opposite sides of the outer surface of each column along a bisecting plane of each column, the bisecting plane being perpendicular to the plane extending between the columns. [Aspect 9] Aspect 9. The testing machine according to any one of Aspects 1 to 8, wherein the brace has an opening through which the axis between the sample holders extends. [Aspect 10] 10. The testing machine of claim 9, wherein the brace has a removable portion that defines a portion of the opening. [Aspect 11] A testing machine as described in any one of aspects 1 to 10, wherein the at least one pair of support columns includes four support columns, a second brace is connected between two support columns different from the first brace, and the second brace is connected to each of the respective support columns at a position along its length between the ends of the sample holder that are remote from each other. [Aspect 12] 12. The testing machine of claim 11, further comprising a third brace and a fourth brace, wherein the brace, the second brace, the third brace, and the fourth brace each connect adjacent struts around a periphery surrounding an axis extending between the sample holders. [Aspect 13] 13. The testing machine according to any one of Aspects 1 to 12, wherein the actuator is disposed within the base. [Aspect 14] 14. The testing machine of claim 13, wherein the support extends through the base. [Aspect 15] 15. The testing machine of claim 14, wherein ends of the struts on the side of the base remote from the crosshead are joined together. [Aspect 16] 13. The testing machine according to any one of Aspects 1 to 12, wherein the actuator is disposed within the crosshead. [Aspect 17] 17. The testing machine of claim 16, wherein the support extends through the crosshead. [Aspect 18] 18. The testing machine of claim 17, wherein ends of the struts on the side of the crosshead remote from the base are joined together. [Aspect 19] A base and At least one pair of posts joined to the base; a crosshead joined to the support column at a position spaced from the base; at least one pair of sample holders, a first sample holder supported by the crosshead and facing the base, and a second sample holder supported by the base, the base being a portion joined to each of the support posts closest to the crosshead; an actuator coupled in series between one of the sample holders and the corresponding base or crosshead; a brace assembly connected to each of the struts at a location along the length of each strut between the base and the crosshead, and a brace assembly spanning between the struts to connect the struts together or to the base or the crosshead. [Aspect 20] 20. The testing machine of claim 19, wherein the brace assembly comprises a brace coupled to the struts at a location spaced from the base and the crosshead and spanning between the struts. [Aspect 21] 20. The testing machine of claim 19, wherein the brace assembly includes a gusset connected to each support, the gusset having a first end connected to the support and a second end connected to the base or the crosshead. [Explanation of symbols]

[0029] 10 Testing Machine 11 frames 12 Base 14 Posts 16 Crosshead 20A First Sample Holder 20B Second sample holder 22 Actuator 24 Force transducer 30 braces 30A end 30B end 32 axes 40 portions 41 plane 42 Aperture 43 plane 44 axes 45 Bisector 46 Removable parts 48 Fasteners 51 Fasteners 52 Brace 53 Brace 54 Brace 55 Brace 58 Brace 59 Brace 70 Connected Elements 72 Structural Elements 80 Clamping device 81 Gusset 82 Gusset 83 Gusset 84 Gusset

Claims

1. A base and a pair of support posts joined to the base and extending parallel to each other; a crosshead joined to the pair of struts at a position spaced from the base; a pair of sample holders including a first sample holder supported by the crosshead and facing the base, and a second sample holder supported by the base and positioned coaxially with the first sample holder; an actuator coupled in series between one of the first and second sample holders and the corresponding base or crosshead; a brace connected to each of the pair of columns and extending between the pair of columns; The brace has an opening through which an axis between the first and second sample holders extends, and the brace has a removable portion that defines a portion of the opening.

2. 2. The testing machine of claim 1, wherein each strut has an axis, and the brace has a portion extending along a plane between the struts that is parallel to a plane containing the axes of both struts.

3. 3. The testing machine of claim 2, wherein the portions at each end of the brace extending along the plane between the posts are joined to opposite sides of the outer surface of each post along a bisecting plane of each post, the bisecting plane being perpendicular to the plane extending between the posts.

4. 2. The testing machine of claim 1, wherein the at least one pair of support columns includes four support columns, a second brace is connected between two different support columns, and the second brace is connected to each of the support columns at a position along its length between the ends of the sample holder that are remote from each other.

5. 5. The testing machine of claim 4, further comprising a third brace and a fourth brace, wherein the brace, the second brace, the third brace, and the fourth brace respectively connect adjacent struts around a periphery surrounding an axis extending between the sample holders.

6. 2. The testing machine of claim 1, wherein the actuator is disposed within the base.

7. 7. The testing machine of claim 6, wherein the support post extends through the base.

8. 8. The testing machine of claim 7, wherein the ends of the struts on the proximal side remote from the crosshead are joined together.

Images