Tensile-compression fatigue test clamp for composite material and method of tensile-compression fatigue test clamp

Abstract

The invention discloses a tensile-compression fatigue test fixture for a composite material, which is used for supporting a test piece, the test piece is a composite material laminated plate, the tensile-compression fatigue test fixture is characterized by comprising anti-instability plates and a clamping piece, the anti-instability plates are arranged on the front side and the rear side of the test piece, and the clamping piece is arranged on the anti-instability plates. Through mutual cooperation of the anti-instability plate and the clamping piece, rapid positioning and installation of the test piece are realized, the loading and unloading efficiency is improved, the overall structure of the clamp is simplified, the overall installation space of the test piece and the clamp is reduced, instability of the test piece in a composite material tensile-compression fatigue test can be effectively prevented, and the test piece is prevented from being damaged. An effective failure mode is obtained so as to meet the requirements of a tensile-compression fatigue test of the composite material.

Description

Technical Field

[0001] This invention relates to a tensile-compression fatigue testing fixture and method for composite materials. Background Technology

[0002] Fiber-reinforced composite materials have been widely used due to their high specific strength, high specific stiffness, and strong design flexibility. To obtain the tensile-compressive fatigue properties of test specimens made of fiber-reinforced composite materials, test fixtures are needed to support and clamp the specimens to prevent overall instability or local buckling during fatigue testing, thus ensuring the acquisition of effective failure modes.

[0003] In related technologies, tensile-compression fatigue testing of composite materials is generally designed according to the specific configuration of the test specimen. That is, each test specimen is usually supported by a dedicated anti-instability fixture. However, this support method has a relatively complex structure, is difficult to install and position, has low loading and unloading efficiency, and requires a relatively large installation space for the testing machine.

[0004] Therefore, there is an urgent need for a test fixture that is simple in structure, easy to install, and can ensure the effective destruction of the test specimen in order to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] The technical problem to be solved by the present invention is that the existing test piece support methods are complex in structure, difficult to install and position, and have low loading and unloading efficiency.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a tensile-compression fatigue test fixture for composite materials, used for supporting test pieces, wherein the test piece is a composite laminate, comprising an anti-instability plate and a clamping member, wherein the anti-instability plate is disposed on the front and rear sides of the test piece, and the clamping member is disposed on the anti-instability plate.

[0008] As a preferred embodiment of the tensile-compression fatigue test fixture for the composite material described in this invention, the anti-instability plate includes a front convex V-shaped upper support plate, a rear concave V-shaped upper support plate, a front concave V-shaped lower support plate, and a rear convex V-shaped lower support plate. The front convex V-shaped upper support plate and the rear concave V-shaped upper support plate are respectively disposed on the front and rear sides of the upper part of the test piece by clamping members. The front concave V-shaped lower support plate and the rear convex V-shaped lower support plate are respectively disposed on the front and rear sides of the lower part of the test piece by clamping members. V-shaped notches are formed between the front convex V-shaped upper support plate and the front concave V-shaped lower support plate, as well as between the rear concave V-shaped upper support plate and the rear convex V-shaped lower support plate.

[0009] As a preferred embodiment of the tensile-compression fatigue test fixture for the composite material described in this invention, the clamping member includes a front baffle, a rear baffle, and a first screw. The front baffle and the rear baffle are respectively disposed on both sides of the front convex V-shaped upper support plate and the rear concave V-shaped upper support plate, as well as the front concave V-shaped lower support plate and the rear convex V-shaped lower support plate, by means of the first screw.

[0010] As a preferred embodiment of the tensile-compression fatigue test fixture for the composite material described in this invention, the inner surfaces of the front convex V-shaped upper support plate, the rear concave V-shaped upper support plate, the front concave V-shaped lower support plate, and the rear convex V-shaped lower support plate are all provided with positioning grooves, and the test piece is placed in the positioning grooves.

[0011] As a preferred embodiment of the tensile-compression fatigue test fixture for the composite material described in this invention, the positioning groove is stepped.

[0012] As a preferred embodiment of the tensile-compression fatigue test fixture for the composite material described in this invention, an elliptical hole is provided at the middle position of both the front baffle and the rear baffle, and a second screw is provided in the elliptical hole.

[0013] As a preferred embodiment of the tensile-compression fatigue test fixture for the composite material described in this invention, the front convex V-shaped upper support plate, the rear concave V-shaped upper support plate, the front concave V-shaped lower support plate, and the rear convex V-shaped lower support plate are provided with countersunk holes, and a third screw is provided in the countersunk holes.

[0014] A method for tensile-compression fatigue testing of composite materials, utilizing the aforementioned tensile-compression fatigue testing fixture for composite materials, includes the following steps: S1: Install the front baffle and the rear baffle onto the front convex V-shaped upper support plate and the rear concave V-shaped upper support plate respectively using the second screw; S2: Place the upper part of the test piece in the positioning groove between the front convex V-shaped upper support plate and the rear concave V-shaped upper support plate and initially tighten the first screw; S3: Place the assembly of the front convex V-shaped upper support plate, the rear concave V-shaped upper support plate and the test piece vertically on the mounting platform, so that the end faces of the three are on the same plane, and tighten the first screw a second time. S4: Install the front baffle and the rear baffle onto the front concave V-shaped lower support plate and the rear convex V-shaped lower support plate respectively using the second screw; S5: Place the lower part of the test piece in the positioning groove between the front concave V-shaped lower support plate and the rear convex V-shaped lower support plate and initially tighten the first screw; S6: Place the assembly of the front concave V-shaped lower support plate, the rear convex V-shaped lower support plate and the test piece vertically on the mounting platform, so that the end faces of the three are on the same plane, and tighten the first screw a second time; S7: Place the entire assembly of the test piece, anti-instability plate, and clamping parts into the hydraulic chuck on the fatigue testing machine, and determine the clamping length and pressure according to the test method; S8: After clamping the assembly of the test piece, anti-instability plate and clamping parts, tighten all the first screws with a torque of 3 N·m; S9: Apply tensile-compressive fatigue loads to the test specimen with anti-instability plate according to the test requirements until the test is completed.

[0015] The beneficial effects of this invention are as follows: by cooperating with the anti-instability plate and the clamping parts, the test piece can be quickly positioned and installed, which improves the loading and unloading efficiency, simplifies the overall structure of the fixture, reduces the installation space of the test piece and the fixture as a whole, and can effectively prevent the test piece from becoming unstable in the tensile-compression fatigue test of composite materials, so as to obtain an effective failure mode and meet the requirements of the tensile-compression fatigue test of composite materials. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 A schematic diagram of the structure for mounting a tensile-compression fatigue test fixture for composite materials onto the test specimen.

[0017] Figure 2 This is a schematic diagram of the split structure between the fixture and the test piece in the tensile-compression fatigue test of composite materials.

[0018] Figure 3 A schematic diagram of the structure of the combination of tensile-compression fatigue test fixture and test piece for composite materials mounted on the hydraulic clamp of the fatigue testing machine.

[0019] In the figure: 10, test piece; 20, anti-instability plate; 201, front convex V-shaped upper support plate; 202, front concave V-shaped lower support plate; 203, rear concave V-shaped upper support plate; 204, rear convex V-shaped lower support plate; 205, positioning groove; 206, countersunk hole; 30, clamping component; 301, front baffle; 302, rear baffle; 303, elliptical hole; 304, first screw; 305, second screw; 306, third screw; 40, hydraulic chuck. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments. Example 1

[0023] Reference Figure 1 and Figure 2 This is the first embodiment of the present invention. This embodiment provides a tensile-compression fatigue test fixture for composite materials for supporting test specimen 10. Test specimen 10 is a composite material laminate, which includes an anti-instability plate 20 and a clamping member 30. The anti-instability plate 20 is disposed on the front and rear sides of the test specimen 10, and the clamping member 30 is disposed on the anti-instability plate 20.

[0024] The fatigue testing fixture in this embodiment is mainly used to support the composite laminate test piece 10. It mainly consists of an anti-instability plate 20 and a clamping member 30. The anti-instability plate 20 is placed on the front and rear sides of the test piece 10, and the clamping member 30 is installed on the anti-instability plate 20. The clamping member 30 can clamp and fix the anti-instability plate 20 and the test piece 10 to prevent them from loosening during the test. In this embodiment, the anti-instability plate 20 and the clamping member 30 cooperate with each other to achieve rapid positioning and installation of the test piece 10, improve loading and unloading efficiency, simplify the overall structure of the fixture, and reduce the overall installation space of the test piece 10 and the fixture.

[0025] Specifically, the anti-instability plate 20 includes a front convex V-shaped upper support plate 201, a rear concave V-shaped upper support plate 203, a front concave V-shaped lower support plate 202, and a rear convex V-shaped lower support plate 204. The front convex V-shaped upper support plate 201 and the rear concave V-shaped upper support plate 203 are respectively set on the front and rear sides of the upper part of the test piece 10 by clamping members 30. The front concave V-shaped lower support plate 202 and the rear convex V-shaped lower support plate 204 are respectively set on the front and rear sides of the lower part of the test piece 10 by clamping members 30. V-shaped notches are formed between the front convex V-shaped upper support plate 201 and the front concave V-shaped lower support plate 202, and between the rear concave V-shaped upper support plate 203 and the rear convex V-shaped lower support plate 204.

[0026] In this embodiment, the anti-instability plate 20 mainly consists of a front convex V-shaped upper support plate 201, a rear concave V-shaped upper support plate 203, a front concave V-shaped lower support plate 202, and a rear convex V-shaped lower support plate 204. The front convex V-shaped upper support plate 201 and the rear concave V-shaped upper support plate 203 are respectively installed on the front and rear sides of the upper part of the test piece 10 through clamping members 30 to support the upper part of the test piece 10. The front concave V-shaped lower support plate 202 and the rear convex V-shaped lower support plate 204 are respectively installed on the front and rear sides of the lower part of the test piece 10 through clamping members 30 to support the lower part of the test piece 10. This effectively prevents the test piece 10 from becoming unstable during the tensile-compression fatigue test of the composite material, obtains an effective failure mode, and meets the requirements of the tensile-compression fatigue test of the composite material. The bottom of the front convex V-shaped upper support plate 201 and the top of the rear convex V-shaped lower support plate 204 are both convex V-shaped. The structure features a concave V-shaped upper support plate 203 at the bottom and a concave V-shaped lower support plate 202 at the top, both forming a concave V-shape. This allows the bottom of the convex V-shaped upper support plate 201 and the top of the concave V-shaped lower support plate 202 to mate, forming a V-shaped notch. Similarly, the bottom of the concave V-shaped upper support plate 203 and the top of the convex V-shaped lower support plate 204 at the bottom mate, forming a V-shaped notch. The V-shaped notches ensure continuous anti-instability support along the length of the test piece 10, effectively transferring tensile and compressive loads to the test piece 10. Furthermore, the V-shaped notches on the left and right sides are not in the same position to better guarantee the anti-instability effect. In addition, the gap between the two formed V-shaped notches is set according to the loading stroke of the fatigue test. This not only prevents interference and collision of the anti-instability plate 20 during compression of the test piece 10 but also ensures the overall anti-instability effect of the anti-instability plate 20.

[0027] Specifically, the clamping member 30 includes a front baffle 301, a rear baffle 302, and a first screw 304. The front baffle 301 and the rear baffle 302 are respectively disposed on both sides of the front convex V-shaped upper support plate 201 and the rear concave V-shaped upper support plate 203, as well as the front concave V-shaped lower support plate 202 and the rear convex V-shaped lower support plate 204 by the first screw 304.

[0028] In this embodiment, the clamping member 30 mainly consists of two front baffles 301, two rear baffles 302, and four first screws 304. The front baffles 301 have a U-shaped structure with a groove in the middle (not shown in the figure). The width of the groove is the same as the width of the anti-instability plate 20. One front baffle 301 is fastened to the front convex V-shaped upper support plate 201, and one rear baffle 302 is fastened to the rear concave V-shaped upper support plate 203. The front baffles 301 and the rear baffles 302 are connected by two first screws 304. Screws 304 are used for fixing the front convex V-shaped upper support plate 201 and the rear concave V-shaped upper support plate 203, thereby providing support for the upper part of the test piece 10. Another front baffle 301 is fastened to the front concave V-shaped lower support plate 202, and another rear baffle 302 is fastened to the rear convex V-shaped lower support plate 204, and they are fixed together by two more first screws 304. The front concave V-shaped lower support plate 202 and the rear convex V-shaped lower support plate 204 are clamped and fixed, thereby enabling the front convex V-shaped upper support plate 201 and the rear concave V-shaped upper support plate 203 to support the lower part of the test piece 10. This makes the assembled test piece 10 and the anti-instability plate 20 form a whole, and at the same time prevents the anti-instability plate 20 from warping or deforming when subjected to compressive load. This effectively prevents the test piece 10 from becoming unstable in the tensile-compression fatigue test of composite materials, obtains an effective failure mode, and meets the requirements of the tensile-compression fatigue test of composite materials. Moreover, the clamping member 30 in this embodiment has a simple overall structure, which not only reduces the overall installation space of the test piece 10 and the fixture, but also improves the efficiency of loading and unloading. It should be noted that this embodiment does not limit the front and rear positions of the front baffle 301 and the rear baffle 302. In other embodiments, the front baffle 301 can also be installed on the rear concave V-shaped upper support plate 203 and the rear convex V-shaped lower support plate 204.

[0029] Furthermore, the inner surfaces of the front convex V-shaped upper support plate 201, the rear concave V-shaped upper support plate 203, the front concave V-shaped lower support plate 202, and the rear convex V-shaped lower support plate 204 are all provided with positioning grooves 205. The test piece 10 is placed in the positioning grooves 205, which are stepped.

[0030] In this embodiment, positioning grooves 205 are provided on the inner surfaces of the front convex V-shaped upper support plate 201, the rear concave V-shaped upper support plate 203, the front concave V-shaped lower support plate 202, and the rear convex V-shaped lower support plate 204. During assembly, the test piece 10 can be placed in the positioning grooves 205 to achieve quick positioning and installation of the test piece 10, further improving the efficiency of loading and unloading. It should be noted that this embodiment does not limit the specific width of the positioning grooves 205. The width of the positioning grooves 205 can be changed to accommodate test pieces 10 of different sizes. Furthermore, the positioning grooves 205 in this embodiment are also stepped. During assembly, the stepped positioning grooves 205 on the inner sides of the front and rear support plates are fastened together, which better ensures the installation position of the test piece 10 and also prevents the test piece 10 from moving during loading.

[0031] Furthermore, an elliptical hole 303 is provided at the middle position of both the front baffle 301 and the rear baffle 302, and a second screw 305 is provided in the elliptical hole 303.

[0032] In this embodiment, elliptical holes 303 are provided at the middle positions of the front baffle 301 and the rear baffle 302. A second screw 305 is installed in the elliptical hole 303 so that the front baffle 301 and the rear baffle 302 can be pre-installed on the anti-instability plate 20 during assembly. The second screw 305 can move up and down in the elliptical hole 303 so as to adjust the installation position of the front baffle 301 and the rear baffle 302 during assembly, thereby better clamping and fixing the anti-instability plate 20.

[0033] Furthermore, countersunk holes 206 are provided on the front convex V-shaped upper support plate 201, the rear concave V-shaped upper support plate 203, the front concave V-shaped lower support plate 202, and the rear convex V-shaped lower support plate 204, and a third screw 306 is provided in the countersunk hole 206.

[0034] In this embodiment, countersunk holes 206 are provided on the front convex V-shaped upper support plate 201, the rear concave V-shaped upper support plate 203, the front concave V-shaped lower support plate 202, and the rear convex V-shaped lower support plate 204. A third screw 306 can be installed in the countersunk hole 206. If the test piece 10 still slips after the front baffle 301 and the rear baffle 302 are assembled, the third screw 306 can be installed in the countersunk hole 206 to further clamp and fix the test piece 10 and prevent the test piece 10 from moving during loading. Example 2

[0035] Reference Figures 1-3 This is the second embodiment of the present invention, which is based on the previous embodiment.

[0036] A method for tensile-compression fatigue testing of composite materials, using the tensile-compression fatigue testing fixture for composite materials in Example 1, includes the following steps: S1: The front baffle 301 is installed on the front convex V-shaped upper support plate 201 through the elliptical hole 303 using the second screw 305, and the rear baffle 302 is installed on the rear concave V-shaped upper support plate 203 through the elliptical hole 303 using the second screw 305. S2: Place the upper part of the test piece 10 into the positioning groove 205 of the front convex V-shaped upper support plate 201, fasten the rear concave V-shaped upper support plate 203 with the rear baffle 302 onto the front convex V-shaped upper support plate 201 on which the test piece 10 is installed, and initially tighten the first screw 304. S3: The assembly of the front convex V-shaped upper support plate 201, the rear concave V-shaped upper support plate 203 and the test piece 10 is placed vertically on the mounting platform, so that the upper end face of the front convex V-shaped upper support plate 201, the upper end face of the rear concave V-shaped upper support plate 203 and the end face of the test piece 10 are on the same plane, and the first screw 304 is tightened a second time so that the front convex V-shaped upper support plate 201 and the rear concave V-shaped upper support plate 203 are clamped and fixed by the front baffle 301 and the rear baffle 302. S4: Use the second screw 305 to install another front side baffle 301 onto the front concave V-shaped lower support plate 202 through the elliptical hole 303; use the second screw 305 to install another rear side baffle 302 onto the rear convex V-shaped lower support plate 204 through the elliptical hole 303. S5: Place the lower part of the test piece 10 in the assembly of the front convex V-shaped upper support plate 201, the rear concave V-shaped upper support plate 203 and the test piece 10 into the positioning groove 205 of the front concave V-shaped lower support plate 202, fasten the rear convex V-shaped lower support plate 204 with the rear baffle 302 onto the front concave V-shaped lower support plate 202 with the test piece 10 already installed, and initially tighten the first screw 304; S6: The assembly of the front concave V-shaped lower support plate 202, the rear convex V-shaped lower support plate 204 and the test piece 10 is placed vertically on the mounting platform, so that the lower end face of the front concave V-shaped lower support plate 202, the lower end face of the rear convex V-shaped lower support plate 204 and the end face of the test piece 10 are on the same plane, and the first screw 304 is tightened a second time so that the front concave V-shaped lower support plate 202 and the rear convex V-shaped lower support plate 204 are clamped and fixed by the front baffle 301 and the rear baffle 302. S7: Place the entire assembly of test piece 10, anti-instability plate 20 and clamping member 30 into the hydraulic chuck 40 on the fatigue testing machine, and determine the clamping length and pressure according to the test method; S8: After clamping the assembly of test piece 10, anti-instability plate 20 and clamping member 30, in order to prevent clamping member 30 from loosening, tighten all the first screws 304 again with a torque of 3 N·m. S9: Apply tensile-compressive fatigue load to the test piece 10 with anti-instability plate 20 using a fatigue testing machine according to the test requirements until the test is completed.

[0037] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A tensile-compressive fatigue test fixture for composite materials, for the support of a test piece (10) which is a composite laminate, characterized in that: The anti-instability plate (20) is arranged on the front and back sides of the test piece (10), and the clamping piece (30) is arranged on the anti-instability plate (20).

2. The tensile-compressive fatigue test fixture for composite materials of claim 1, wherein: The anti-instability plate (20) comprises a front convex V-shaped upper support plate (201), a back concave V-shaped upper support plate (203), a front concave V-shaped lower support plate (202) and a back convex V-shaped lower support plate (204), the front convex V-shaped upper support plate (201) and the back concave V-shaped upper support plate (203) are arranged on the front and back sides of the upper part of the test piece (10) through the clamping piece (30), the front concave V-shaped lower support plate (202) and the back convex V-shaped lower support plate (204) are arranged on the front and back sides of the lower part of the test piece (10) through the clamping piece (30), and V-shaped notches are formed between the front convex V-shaped upper support plate (201) and the front concave V-shaped lower support plate (202) and between the back concave V-shaped upper support plate (203) and the back convex V-shaped lower support plate (204).

3. The tensile-compressive fatigue test fixture for composite materials of claim 2, wherein: The clamping piece (30) comprises a front baffle (301), a back baffle (302) and a first screw (304), the front baffle (301) and the back baffle (302) are arranged on the two sides of the front convex V-shaped upper support plate (201) and the back concave V-shaped upper support plate (203) and the front concave V-shaped lower support plate (202) and the back convex V-shaped lower support plate (204) through the first screw (304).

4. The tensile-compressive fatigue test fixture for composite materials of claim 2, wherein: The inner surfaces of the front convex V-shaped upper support plate (201), the back concave V-shaped upper support plate (203), the front concave V-shaped lower support plate (202) and the back convex V-shaped lower support plate (204) are provided with positioning grooves (205), and the test piece (10) is placed in the positioning grooves (205).

5. The tensile-compressive fatigue test fixture for composite materials of claim 4, wherein: The positioning grooves (205) are in a stepped shape.

6. The tensile-compressive fatigue test fixture for composite materials of claim 3, wherein: Elliptical holes (303) are arranged at the middle positions of the front baffle (301) and the back baffle (302), and second screws (305) are arranged in the elliptical holes (303).

7. The tensile-compressive fatigue test fixture for composites of claim 2, wherein: Sunk holes (206) are arranged on the front convex V-shaped upper support plate (201), the back concave V-shaped upper support plate (203), the front concave V-shaped lower support plate (202) and the back convex V-shaped lower support plate (204), and third screws (306) are arranged in the sunk holes (206).

8. A tensile-compressive fatigue test method of a composite material using the tensile-compressive fatigue test jig for a composite material according to any one of claims 1 to 7, characterized by, The method comprises the following steps: S1: the front baffle and the back baffle are respectively installed on the front convex V-shaped upper support plate and the back concave V-shaped upper support plate through the second screw; S2: the upper part of the test piece is placed in the positioning groove between the front convex V-shaped upper support plate and the back concave V-shaped upper support plate, and the first screw is preliminarily tightened; S3: the combination of the front convex V-shaped upper support plate, the back concave V-shaped upper support plate and the test piece is vertically placed on the installation platform, so that the end faces of the three are in the same plane, and the first screw is tightened again; S4: the front baffle and the back baffle are respectively installed on the front concave V-shaped lower support plate and the back convex V-shaped lower support plate through the second screw; S5: the lower part of the test piece is placed in the positioning groove between the front concave V-shaped lower support plate and the back convex V-shaped lower support plate, and the first screw is preliminarily tightened; S6: vertically place the combination of the front concave V-shaped lower support plate, the rear convex V-shaped lower support plate and the test piece on the mounting platform, so that the end faces of the three are on the same plane, and secondly tighten the first screw; S7: place the combination of the test piece, the anti-instability plate and the clamping piece as a whole into the hydraulic chuck on the fatigue testing machine, and determine the length and pressure of clamping according to the test method; S8: after the clamping of the combination of the test piece, the anti-instability plate and the clamping piece is completed, tighten all the first screws with a torque of 3N·m; S9: apply tensile-compressive fatigue load to the test piece with the anti-instability plate according to the test requirements until the test is completed.

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